Fabrication challenges and trends in biomedical applications of alginate electrospun nanofibers

Journal Pre-proof Fabrication Challenges and trends in biomedical applications of alginate electrospun nanofibers Mahdokht Akbari Taemeh, Ayoub Shiravandi, Maryam Asadi Korayem, Hamed Daemi

PII:

S0144-8617(19)31086-0

DOI:

https://doi.org/10.1016/j.carbpol.2019.115419

Reference:

CARP 115419

To appear in:

Carbohydrate Polymers

Received Date:

5 August 2019

Revised Date:

29 September 2019

Accepted Date:

30 September 2019

Please cite this article as: Taemeh MA, Shiravandi A, Korayem MA, Daemi H, Fabrication Challenges and trends in biomedical applications of alginate electrospun nanofibers, Carbohydrate Polymers (2019), doi: https://doi.org/10.1016/j.carbpol.2019.115419

This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier.

Fabrication Challenges and trends in biomedical applications of alginate electrospun nanofibers

of

Mahdokht Akbari Taemeh ║, Ayoub Shiravandi ║, Maryam Asadi Korayem, Hamed Daemi*

ro

Department of Cell Engineering, Cell Science Research Center, Royan Institute for Stem Cell

These authors contributed equally to this paper.

re

║

-p

Biology and Technology, ACECR, Tehran, Iran

ur na

lP

* Corresponding author: Dr. Hamed Daemi, E-mail:[email protected]

Highlights 

The challenges and solutions of alginate electrospinning were reviewed for the first time.



High density of intra- and intermolecular hydrogen bonding restricts alginate

Jo

electrospinnability.



Alginate electrospinnability can be improved by blending with carrier polymers.



Electrospinning of alginate can be dramatically facilitated through chemical modifications.



Alginate nanofibers can be used in tissue engineering and drug delivery systems.

1

Abstract Alginate as a naturally-derived biomaterial with marine algae sources has gained much attention in both laboratorial and industrial applications due to its structural and chemical resemblance to extracellular matrix (ECM) as well as desirable properties like biocompatibility, biodegradability, processability and low cost. Electrospun alginate nanofibrous scaffolds have found wide

of

applications in biomedical field such as tissue engineering, biomedicine and drug delivery systems. However, electrospinning of alginate is challenging due to the low solubility and high viscosity of

ro

high molecular weight alginate, high density of intra- and intermolecular hydrogen bonding,

-p

polyelectrolyte nature of aqueous solution and lack of appropriate organic solvent. The aim of this review is to summarize the challenges and obstacles in alginate electrospinning reported in the

re

literature as well as the introduced solutions for them, in order to open new opportunities for more

lP

intended and successful investigations in the field. Keywords

Jo

ur na

Alginate; Nanofibers; Electrospinning; Wound dressing; Biomedical applications

2

1. Introduction Alginate, also called alginic acid, is a naturally occurring anionic polysaccharide with a herbal origin widely distributed in the cell walls of brown algae and generally extracted in sodium salt or acidic form (Dekamin et al., 2018; Pawar, & Edgar, 2012). It is also synthesized through the microbial fermentation by different bacteria such as Azotobacter and Pseudomonas (Batista, de Morais, Pintado, & de Morais, 2019). Marine extraction of alginate from algae reduces its

of

production costs and makes it available for different laboratorial and industrial applications

ro

(Daemi, Barikani, & Sardon, 2017; Lee, & Mooney, 2012). Alginate with algal sources exhibits different structural and chemical properties with respect to its seasonal and growth conditions

-p

(Daemi, Rezaieyeh Rad, Adib, & Barikani, 2014). Algal alginates usually possess a high content

re

of G blocks and are employed for biomedical application, while alginates with bacterial sources are M-enriched, immunogenic and show more potency to induce cytokine production (Otterlei et

lP

al., 1991). Alginate has been approved by the FDA for certain uses such as wound dressing, dental impression materials, food additives and textile because of its high moisture absorption, relatively

ur na

low cost, jellifying ability, availability, mild process conditions and cytocompatibility (Ching, Bansal, & Bhandari, 2017; Daemi et al., 2016). Furthermore, the alginate moieties lack the bioactive ligands necessary for cell anchoring, therefore , alginate shows proper biocompatibility and low immunogenicity (Batista et al., 2019).

Jo

Alginate is a linear copolymer consists of β-D-mannuronic acid (polyM) and α-L-guluronic acid (polyG) units. These units have been jointed together by 1 → 4 glycosidic bonds (Fig. 1). Alginate monovalent salts are water-soluble, while its acidic or multivalent salt forms are insoluble both in aqueous and organic media (Daemi & Barikani, 2012). The polymeric chains of alginate can easily crosslink in the presence of multivalent cations, especially calcium cations. When calcium cations

3

chelate with the G blocks of alginate in a proposed ‘‘egg-box’’ model, a calcium alginate hydrogel forms (Grant, Morris, Rees, Smith, & Thom, 1973; Morris, Rees, Thom, & Boyd, 1978). Reactive sites of alginate including carboxylic and hydroxyl groups, and chemically labile linkages, i.e. 1 → 4 glycosidic and internal glycolic bonds can be chemically treated to be used for production of more functional materials (Borgogna, Skjåk-Bræk, Paoletti, & Donati, 2013; Daemi, & Barikani,

-p

ro

of

2014).

re

Fig. 1. Chemical structure of sodium alginate

lP

Alginate hydrogels are inert biomaterials and can be used in a wide range of biomedical applications for example, wound healing, cell culture, cell transplantation and delivery of

ur na

pharmaceuticals because of their structural similarity to extracellular matrix (ECM) of living tissues (Augst, Kong, & Mooney, 2006; Esfandiari et al., 2017). The sheets and freeze-dried scaffolds of alginate have also been proposed for biomedical applications. In addition, the alginate microfibrous wound dressings traditionally crosslinked by divalent cations can promote formation

Jo

of granulation tissue, keratinocyte differentiation, rapid epithelialization, and appropriate healing (Aderibigbe & Buyana, 2018). Wet spinning is the common industrial method used for the production of alginate fibers with a diameter of 10 to hundreds of micrometers (Qin, 2008). Alginate scaffolds in form of nanofibrous mats have rarely been used in biomedical and industrial fields, since the mass production of alginate nanofibers is associated with different challenges. The alginate nanofibers may have a high potential in fabrication of tissue engineering scaffolds for 4

skin, bone, cartilage, and liver tissues as well as producing wound dressings with appropriate properties (Daemi, Mashayekhi, & Modaress, 2018). Despite the importance and various applications of alginate nanofibers, to date, efforts have not been successful for electrospinning of highly pure alginate nanofibers. Polymeric nanofibers have a wide range of applications in various fields of tissue engineering scaffolds, nanocatalysts, protective clothing, filters and biotechnology; therefore, their fabrication

of

methods, and modification their chemical, physical, and biological characteristics are very

ro

important (Pezeshki-Modaress, Mirzadeh, & Zandi, 2015; Ramakrishna et al., 2006). To make nanofibers, different techniques such as electrospinning, self-assembly, and phase separation have

-p

been used. The electrospinning technique is an interesting method for fabrication of polymer

re

nanofibers due to its ability to produce homogeneous fibers with controllable size and porosity, high efficiency and simplicity (Bhardwaj & Kundu, 2010).

lP

Until now, electrospinning method has been used in order to make nanofibers of different natural and synthetic polymers, such as proteins, nucleic acids and polysaccharides, or a combination of

ur na

them in the sub-micron dimensions (Schiffman & Schauer, 2008). In general, electrospinning of synthetic polymers are simpler than natural polymers due to their proper physicochemical properties. These advantages have caused a large number of research in the field of synthetic polymers; however, several important factors such as biocompatibility, biodegradability, having

Jo

cell attachment points, and non-toxicity have significant impact on the final product performance especially in medical applications (Iwasaki et al., 2004; Matricardi, Di Meo, Coviello, Hennink, & Alhaique, 2013). Therefore, using synthetic polymers in combination with natural polymers such as alginate, cellulose, chitosan, gellan gum, silk, collagen, fibronectin, and hyaluronic acid is desirable (Khan, & Ahmad, 2013; Sahraro, Barikani, & Daemi, 2018; Torabi, Sahraro, Barikani,

5

& Daemi, 2019). By considering the advantages of alginate nanofibers and their fabrication challenges, we have reviewed these challenges and methods employed to overcome them in detail

re

-p

ro

of

as well as the trends in biomedical applications of alginate electrospun nanofibers (Fig. 2).

2. Electrospinning

lP

Fig. 2. Schematic of alginate electrospinning process and its biomedical applications

ur na

Electrospinning has been used in many papers and patents to produce micro- and nanofibers. In this method, a high voltage creates a strong electric field between the collector and the electrospinning solution (Garg & Bowlin, 2011). This electric field applies a great force to the polymer molecules which are placed in the syringe nozzle and have been charged by potential

Jo

difference. The polymer at the end of the syringe nozzle is affected by two main forces: first, the surface tension that holds the polymer at the end of the nozzle and second, the force that is generated by the electric field and pulls the polymer toward the collector. By increasing the voltage, into a critical value, the generated force by electrical field, overcomes the surface tension of polymer, and the polymer in the end of the syringe tends to move toward the collector to form

6

a jet. Finally, a flow of the desired polymer solution or melt, moves from the syringe toward the conductive collector (Lim, 2017). In electrospinning process, the polymer can be used either in its molten state or as a polymer solution. In solution form, the solvent is evaporated during spinning, or the fibers are washed at the end of the process. The main challenge of solution electrospinning is choosing the suitable solvent as well as complete solvent elimination from the final product. Electrospinning of a

of

polymer in its molten state without using a solvent, is more suitable for polymers that are hardly

ro

soluble in common solvents. However, the high viscosity of polymers in molten state and the high melting temperature of most polymers have limited the application of this method for a wide range

-p

of natural and synthetic polymers. As a result of this limitation, almost all natural and synthetic

3. Challenges in alginate electrospinning

re

polymers are electrospun in soluble state (Li, & Xia, 2004).

lP

It is difficult to obtain continuous and uniform nanofibrous structures from pure alginate solutions via electrospinning, both in aqueous and organic solvents, and to date, there is no successful report

ur na

in this regard (Aadil, Nathani, Sharma, Lenka, & Gupta, 2018). To fabricate alginate containing nanofibers, researchers have been used spinning aid or carrier polymers such as poly(vinyl alcohol) (PVA) or poly(ethylene oxide) (PEO) (Bhardwaj & Kundu, 2010; Schiffman & Schauer, 2008). However, the challenges of low content of alginate and existence of impurities in resulting

Jo

electrospun mat, as well as hurdles in mass production of alginate-based nanofibers are still unsolved.

Different reasons have been given in the literature to explain alginate inability to form nanofibers via electrospinning. Some studies have declared that the electrical conductivity and high surface tension of alginate solution are the main reasons (Aadil et al., 2018). It has been shown that the

7

addition of surfactants will increase the alginate content in electrospinnable solution and result in smoother and bead-free fibers. However, using an additive electrospinnable polymer such as PEO in the solution is crucial (Bonino et al., 2012). Bonino et al., showed that addition of Triton X-100 into a blend of alginate and PEO eliminates the beads and results in smooth fibers, but when this surfactant was added to a pure alginate solution no fiber was obtained (Fig. 3) (Bonino et al., 2011). This shows that while surface tension plays an important role in alginate electrospinning, it cannot

Jo

ur na

lP

re

-p

ro

of

be considered as the main defining and limiting factor.

Fig. 3. Scanning electron micrographs of electrospun droplets of alginate (a) and alginate/Triton X-100 (b), both without PEO. Electrospun blended nanofibers prepared from alginate–PEO (600 8

kDa) (70:30 by wt.%) solutions. Beaded fibers, (c) and (d), were made without surfactant, whereas uniform fibers, (e) and (f), contained 1 wt.% Triton X-100 (Bonino et al., 2011). Some studies have investigated the role of spinning aid polymers in alginate electrospinning to shed more light on underpinning restrictive reason. In early studies of using PEO or PVA as spinning aid polymers to obtain alginate containing nanofibers, it was believed that the hydrogen

of

bonding that is formed between the ether oxygen of PEO or the hydroxyl groups of PVA and the hydroxyl groups of alginate, facilitates the electrospinning of the blend (Garg & Bowlin, 2011).

ro

However, further studies showed that despite the interactions between alginate and PEO molecules

-p

with molecular weight of 35 kDa, the blended solutions were electrosprayed and did not form continuous fibers. Saquing et al., examined electrospinning of alginate and PEO blends with

re

different molecular weights of PEO from 100 to 2000 kDa. Aqueous PEO solutions were mixed with both low viscosity (25 cP) and medium viscosity (200 cP) algal-based aqueous alginate

lP

solutions (corresponding average molecular weights of 46 and 100 kDa, respectively), where total polymer concentration was constant (4 wt.%) and ratio of PEO to alginate was varied (30:70,

ur na

50:50, and 70:30). As shown in the Fig. 4, the alginate content of bead-free fibers increased by increasing PEO molecular weight. While pure PEO solutions with MW of 100 to 600 kDa were readily electrospun, their blends with alginate did not result in fiber formation (Saquing et al.,

Jo

2013). It seems that by increasing the molecular weight of PEO, more hydroxyl groups in alginate structure will have donor-receptor interaction with ether groups in polyethylene oxide and consequently, the solution viscosity and electrospinnability of alginate will be improved (Daemi & Barikani, 2012). This result further demonstrates that even if the carrier polymer has sufficient entanglement to form fibers alone, it will not guarantee the generation of bead-free composite fibers when is blended with alginate. It suggests that the sufficient entanglement through the 9

molecules of a high molecular weight carrier polymer is necessary to facilitate the electrospinnability of the solution, not the interaction between the spinning aid polymer and

Jo

ur na

lP

re

-p

ro

of

alginate.

Fig. 4. The effect of PEO molecular weight (100-2000 kDa) on electrospinning of alginate-PEO blends. The scale bar shown on each SEM micrograph is 2 μm (Saquing et al., 2013)

10

It can be concluded that the main reason restricting alginate electrospinning is the lack of molecular entanglement and the rigid structure of alginate. This rigidity occurs due to extensive inter- and intra- molecular hydrogen bonding between carboxylate and hydroxyl groups of alginate and restricts polymer flexibility in aqueous solution (Schiffman & Schauer, 2008). To further demonstrate this phenomenon, researchers have recently conducted some chemical modifications on alginate backbone to hinder these inter- and -intra molecular hydrogen bonding. It has been

of

shown that these modifications can result in alginate content up to 50 wt.% in dry electrospun mats

ro

(Daemi et al., 2018). 4. Strategies for alginate electrospinning

-p

There are different physical and chemical strategies to facilitate alginate electrospinnability. Here,

re

we review the most important procedures that have been successful in this context. 4.1. Using carrier polymer

lP

Alginate electrospinnability can be improved by blending with carrier polymers, i.e. the materials which are easily electrospun. In recent years, polyethylene oxide (PEO) has been considered as a

ur na

widely-used carrier polymer because of its advantages such as good electrospinnability, appropriate biomedical properties and low cost. PEO and alginate can form a stable mixture in an aqueous solution by hydrogen bonding formation as a result of their hydroxyl and ether functional groups. The interaction between PEO and alginate alters the physical properties of the solution

Jo

such as viscosity and surface tension, and results in an electrospinnable solution (Safi, Morshed, Hosseini Ravandi, & Ghiaci, 2007). Another common carrier polymer used for alginate electrospinning is polyvinyl alcohol (PVA). In addition to the exposed hydroxyl groups in chemical structure and the possibility of hydrogen bonding formation with hydroxyl groups in alginate, PVA has an appropriate electrospinnability

11

that makes it a proper choice as a carrier polymer in alginate electrospinning (Daemi et al., 2018). The effects of PEO and PVA on the viscosity and electrospinnability of alginate containing solutions have been discussed in several studies. For example, Bhattarai et al. stated that the viscosity of alginate solution decreases when PEO (MW of 900 kDa) content increases. Moreover, storing alginate solution in ambient environment leads to a lower viscosity (Bhattarai & Zhang, 2007). In contrast, Saquing et al. revealed that addition of PEO (with MW of 1000 kDa) improved

of

electrospinnability by increasing the viscosity of the blend. Moreover, they explained that slightly

ro

higher viscosity of PVA in comparison to PEO, leads to more beaded fibers (Kataria, Gupta, Rath, Mathur, & Dhakate, 2014; Saquing et al., 2013). Therefore, it can be concluded that the effect of

-p

carrier polymer on solution viscosity depends on several factors such as carrier polymer type and

re

its molecular weight, and sodium alginate viscosity. Another study showed that addition of Ca2+ cations to the sodium alginate solution increases the viscosity of this solution by increasing ionic

lP

interactions among sodium alginate chains (Fang, Liu, Jiang, Nie, & Ma, 2011). Table 1 reports some important studies in alginate electrospinning using PEO or PVA as carrier

ur na

polymers without utilization of surfactant or co-solvent. The reporting parameters correspond to bead-free mats. The carrier polymer properties, sodium alginate content at final mat and electrospinning conditions are summarized in Table 1. As shown in Table 1, the content of SA at final mat is usually very low. However, Bhattarai et al.,

Jo

exhibited that the SA content can be increased up to 50 wt.% in final mat when the high molecular weight of PEO is used (Bhattarai & Zhang, 2007). In another study, PVA was used as the carrier polymer with 40% SA at final mat, however a few spindle-like beads were observed among the fibers (Li et al., 2013). It is important noting that a few studies have also reported the electrospinning of alginate without PEO or PVA, using other carrier polymers such as gelatin,

12

pullulan and polycaprolactone, nevertheless the results have not been desirable (Kim & Kim, 2014; Moon & Farris, 2009; Xiao & Lim, 2018).

4.2. Using co-solvent and surfactant Electrospinning of aqueous alginate solution alone is difficult and kind of impossible (Aadil et al., 2018). The use of PEO or PVA as the carrier polymer can help to improve the alginate

of

electrospinnability (Li et al., 2013; Lim, 2017). However, using a carrier polymer alone is not

ro

desirable because the obtained nanofibers contain low contents of alginate as shown in Table 1. Therefore, using surfactants is logically accepted for reducing the surface tension of solution which

-p

affords increasing of alginate content in the final mat. Surfactants are amphiphilic chemical structures that consist of a charged head group and a hydrocarbon tail, so they are absorbed in the

re

air-water interface (Doğaç, Deveci, Mercimek, & Teke, 2017).

lP

Using Triton X-100 as a surfactant can increase the alginate content up to 80 wt.% (Bhattarai & Zhang, 2007) and also decrease the surface tension from 36.8 mN/m to 13.7 mN/m. However, this surfactant does not significantly change the viscosity of the solution (14.7 Pa.S and 14.6 Pa.S with

ur na

and without Triton X-100, respectively) (Saquing et al., 2013). Triton X-100 (Doğaç et al., 2017) (Shen & Hsieh, 2014), pluronic F127 (Bonino et al., 2012; Bonino et al., 2011) and lecithin (Park, Park, & Kim, 2010) are widely-used surfactants that have been used to improve alginate

Jo

electrospinnability.

Using surfactants alone can improve alginate electrospinning, but in some cases, researchers have used co-solvents in addition to surfactants to achieve better results. Co-solvents can change the viscosity of the solution by different mechanisms such as creating dipole–dipole interaction with alginate chains and weakening the association between its chains and or forming new hydrogen bonding with alginate chains after disrupting some or most of the inter- and intramolecular 13

hydrogen bonding of alginate chains (Nie et al., 2008; Saquing et al., 2013). For example, using 5 wt.% of a co-solvent and 0.5 wt.% of a surfactant together increases the alginate content up to 90 wt.% and reduces the viscosity from 437 mPa.s to 402 mPa.s (Bhattarai & Zhang, 2007; Leung et al., 2014). The co-solvents which are used in alginate electrospinning are DMSO (Hu & Yu, 2013; Mokhena & Luyt, 2017; Xu, Shen, Yan, & Gao, 2017), glycerol (Chang, Lee, Wu, Yang, & Chien, 2012; Yu et al., 2013), DMF (Hajiali, Heredia-Guerrero, Liakos, Athanassiou, & Mele, 2015; Kim

of

& Kim, 2014), sodium carbonate (Tarun & Gobi, 2012), ethanol (Nista, Bettini, & Mei, 2015) and

ro

propanol (Stone, Gosavi, Athauda, & Ozer, 2013). A summary of electrospinning characteristics

4.3. Chemical modification of alginate backbone

-p

of alginate using several co-solvents and surfactants is shown in Table 2.

re

Majority of research on improving alginate electrospinning have focused on physical and rheological aspects of alginate blends with carrier polymers or/and co-solvents and surfactants.

lP

However, there are a few reports that have shown the electrospinning of alginate can be dramatically facilitated through chemical modifications. As mentioned before, alginate

ur na

electrospinning is challenging due to its inter- and intramolecular hydrogen bonding, rigid chain conformation and low solubility. Decrease in density of hydrogen bonding through chemical modification could be a rational design to solve these challenges. Since both free hydroxyl and carboxyl functional groups of alginate chains impart in inter- and intramolecular hydrogen

Jo

bonding, it seems that the chemical modification can decrease hydrogen bonding density and alter alginate solubility in aqueous and organic media (Fig. 5).

14

of ro -p re lP

Fig. 5. Decrease in inter- and intramolecular hydrogen bonding density of alginate through

ur na

chemical modification of hydroxyl groups The oxidation, sulfation and esterification of hydroxyl groups of alginate backbone afford the substitution of protons of OH groups with new atoms or functional groups that lack the ability to form hydrogen bonding. By keeping these modifications in mind, we previously reported the

Jo

sulfation of alginate and the facile production of sulfated alginate nanofibers via electrospinning method (Daemi, Mashayekhi, & Pezeshki Modaress, 2018). We showed that the sodium sulfated alginate (SSA) can be simply dissolved in deionized water at different concentrations up to 10 wt.%., and further electrospun combined with PVA aqueous solution results in 50 wt.% content of SSA electrospun nanofibers in a dry electrospun mat without using any co-solvent or surfactant

15

for the first time. After that, Mohammadi et al., reported the fabrication of PVA/SSA scaffolds and transforming growth factor-β1 (TGF-β1) loading into the nanofibrous mats (Mohammadi et al., 2019). They found that the release profile of TGF-β1 from sulfated alginate scaffolds is more sustained compared to the non-modified alginate. In addition, the oxidation of internal glycolic bonds converts the vicinal hydroxyl groups of alginate chemical structure to aldehyde functional groups. Therefore, both hydrogen bonding density and viscosity of alginate dialdehyde (ADA)

of

decrease in aqueous solution. In contrast to the low solubility of sodium alginate, Zhao et al.,

5. Biomedical applications of alginate nanofibers

-p

the aid of polyethylene oxide (Zhao, Chen, Lin, & Du, 2016).

ro

prepared aqueous solution of ADA with a high concentration of 6% w/v and electrospun it with

re

Alginate is a hydrophilic compound; hence the alginate fibers are easily dissolved in aqueous media and subsequently lose their stability. To produce stable nanofibers of alginate, two simple

lP

post-electrospinning crosslinking methods using divalent cations such as calcium ions and/or dialdehyde compounds such as glutaraldehyde are possible (Kyzioł, Michna, Moreno, Gamez, &

ur na

Irusta, 2017; Vigani et al., 2018, Wang et al., 2019). Due to the toxicity of aldehyde groups and the possibility of replacing calcium cations with sodium ones in vivo, these fibers lose their stability and are not ideal for in vivo applications. Two other methods for increasing the stability of alginate nanofibers are converting them to the

Jo

alginic acid nanofibers using acidic compounds such as trifluoroacetic acid or photo-crosslinking by photopolymerization process (Hajiali, Heredia-Guerrero, Liakos, Athanassiou, & Mele, 2015; Jeong, Jeon, Krebs, Hill, & Alsberg, 2012). Therefore, it can be expected that if the electrospun alginate nanofibers convert to insoluble alginic acid nanofibers, both the stability and biodegradability of nanofibers will be improved. Hajiali et al. showed that the nanofibers stabilized

16

with this method are non-toxic against fibroblasts. Unfortunately, glycosidic linkages between the uronic acid moieties in the alginate sequences are highly susceptible to degradation in the acidic medium. The result of these chemical events is degradation of the alginate chemical structure and decrease in its molecular weight. Alginate possesses favorable properties which makes it an ideal biomaterial for biological applications (Lee, Jeong, Kang, Lee, & Park, 2009). Besides, utilization of alginate in form of

of

nanofibers can promote its function and extend its application as a biomaterial due to high surface

ro

area of nanoscale materials (Lee et al., 2009). The most attractive applications of alginate nanofibers in biomedical field are explained below.

-p

5.1. Wound dressing

re

Alginate-based wound dressings are commercially used for bleeding wounds because of their ability in removing the dressing without trauma and pain, rapid granulation and re-epithelialization

lP

(Paul & Sharma, 2004), and absorbing heavy exudate of wounds (Aderibigbe & Buyana, 2018). It should be stated that the form of a dressing is one of the most important factors in fabrication of a

ur na

wound dressing. Several studies indicated the positive effect of a nanofibrous dressing on wound healing. A nanofibrous dressing promotes hemostasis (Wnek, Carr, Simpson, & Bowlin, 2003), absorbs high amount of wound exudates which is considerable compared with other forms of dressings such as films, retains the wound area moist and inhibits bacterial infection while allowing

Jo

gas penetration (Khil, Cha, Kim, Kim, & Bhattarai, 2003) and completely fits the wound (Zhang, Lim, Ramakrishna, & Huang, 2005). Since antibacterial property of a wound dressing is essential and due to the high utilization of alginate as the dressing material, several research have been performed on fabrication of antibacterial alginate-based nanofibrous dressings. In one study, antibacterial nanofibrous mats were fabricated by adding nanometer silver colloids to an

17

electrospinning solution consisting of sodium alginate, PEO and gelatin (Kong, Yu, Ji, & Xia, 2009). In another study, silver nanoparticles (AgNPs) were synthesized and used as antibacterial agent for electrospun alginate membranes (Alsberg et al., 2003). Mokhena and Luyt showed that the coating of chitosan/AgNPs onto an electrospun alginate membrane affords a polyelectrolyte complex with high antibacterial activity (Mokhena & Luyt, 2017). Moreover, ciprofloxacin can be used as an antibiotic in fabrication of antibacterial sodium alginate nanofibrous mats (Kataria et

of

al., 2014; Kyzioł, Michna, Moreno, Gamez, & Irusta, 2017). In one study, honey was incorporated

ro

into an alginate/PVA-based electrospun nanofibrous membrane to develop an efficient wound dressing material. The nanofibrous membranes with increasing honey content showed enhanced

-p

antioxidant activity, suggesting the ability of nanofibrous dressings to control the overproduction

re

of reactive oxygen species (Tang et al., 2019). 5.2. Tissue Engineering

lP

There is an increasing interest in use of polymeric nanofibers in tissue engineering as they can be tailored to mimic the natural extracellular matrix (ECM) from different aspects like structure,

ur na

chemical composition and mechanical properties (Li, Laurencin, Caterson, Tuan, & Ko, 2002; Rho et al., 2006). Moreover, studies have shown that polymeric scaffolds with nanoscale structures have better function in comparison to microstructures (Pattison, Wurster, Webster, & Haberstroh, 2005). Recently, electrospun natural biopolymers have been considered ideal candidates in

Jo

fabrication of nanofibrous scaffolds due to their suitable biological properties (Hsu et al., 2004; Suh & Matthew, 2000). Among natural biopolymers, alginate has received much attention to be used for tissue engineering of bone (Chae, Yang, Leung, Ko, & Troczynski, 2013), cartilage (Li & Zhang, 2005) and skin (Hashimoto, Suzuki, Tanihara, Kakimaru, & Suzuki, 2004). It is because of alginate’s special properties and its resemblance to major components of ECM in human body,

18

i.e. glycosaminoglycan (GAG) (Arlov, Aachmann, Sundan, Espevik, & Skjåk-Bræk, 2014; Zhao et al., 2007). Alginate/gelatin nanofibrous hydrogel achieved by wet electrospinning are ideal candidates for 3D cell culture and tissue regeneration. These 3D macroporous nanofibrous hydrogel (Alg/GelFMA) enable create greater cell adhesion, motility, proliferation and maturation (Majidi et al., 2018). Chemical modification of alginate by a cell adhesive peptide named Gly-Arg-Gly-Asp-Ser-Pro

of

(GRGDSP) before blending with PEO (to get uniform nanofibers), leads to attachment and growth

ro

of human dermal fibroblast cells (HDFs) on the surface of alginate nanofibers. These resultant nanofibers with cell adhesive properties are promising to be used in tissue regeneration

-p

applications (Jeong et al., 2010). In this context, nanofibrous membranes of sodium alginate/PEO

re

with a core-shell structure have a good potential to be used for tissue engineering scaffolds (Ma, Fang, Liu, Zhu, & Nie, 2012). Using chitosan in fabrication of alginate nanofibrous scaffolds not

lP

only improves cell adhesion and proliferation, but also eliminates the need of using toxic crosslinking agents. These polyionic complexed nanofibrous scaffolds can guide cell behavior in

ur na

tissue regeneration applications through the serum proteins adsorbed by chitosan (Jeong et al., 2010). Yu et al. fabricated an electrospun composite scaffold made of alginate, chitosan, collagen and hydroxyapatite which could support cell infiltration and growth. In comparison to conventional collagen scaffolds, this composite reduces disintegration of scaffold for bone tissue

Jo

engineering that makes it applicable for regenerating bone tissue (Yu et al., 2013). Saberi et al. added a bioglass (BG) ceramic into a nanofibrous scaffold of PVA/SA to obtain improved mechanical properties, and chemical and biological stability. Moreover, they indicated the formation of hydroxyapatite particles, one of the most important components of bone tissue, where the scaffold was immersed in simulated body fluid (SBF) (Saberi, Rafienia, & Poorazizi, 2017).

19

Chae et al. showed that presence of hydroxyapatite in hydroxyapatite/alginate nanocomposite fibrous scaffolds leads to stable attachment of rat calvarial osteoblast cells on scaffolds in comparison to pure alginate, and the morphology of osteoblasts differed from round-shape on pure alginate scaffolds into spindle-shape on the HAp/alginate scaffolds (Chae et al., 2013). In another recent study, nHAP was ultrasonically suspended in SA aqueous solution as stabilizer and electrospun in combination with PVA. The hemolysis and cytotoxicity analyses showed that the

of

nanocomposite fibrous membrane possesses good biocompatibility (Ni et al., 2019).

ro

Polycaprolactone (PCL) can be used to make an alginate containing nanofibrous scaffold suitable for hard tissue regeneration. Apart from better mechanical properties of the PCL-alginate scaffold

-p

reinforced with PCL struts compared to the alginate fibrous scaffold, these scaffolds have shown

re

high level of osteogenic differentiation (Kim & Kim, 2014). Furthermore, PCL/SA nanofibers have been used for cancer stem cell (CSC) enrichment. The results showed that alginate nanofibers

lP

effectively enriched CSCs and composite fibers created an uneven microenvironment to regulate cell morphology and distribution (Hu, Lin, & Hong, 2019). Also, alginate-based nanofibrous

ur na

scaffolds have been fabricated by incorporation of drug-loaded halloysite nanotubes (HNT). Low HNT composition led to bead-free nanofibers and good uniaxial alignment of HNT within alginate matrix enhanced mechanical properties of scaffolds. In continuation, cephalexin (CEF) was loaded within the lumen space of HNT and resulted in a sustained release profile of drug and great

Jo

antimicrobial properties against bacteria of S. aureus, S. epidermidis, P. aeruginosa and E. coli. Such a scaffold is potentially suitable for skin wounds regeneration (De Silva et al., 2018). 5.3. Drug Delivery Properties including biocompatibility, the ability of entrapping biomolecules and the possibility of achieving different size and shape have made alginate-based systems appropriate for drug delivery

20

systems (Ciofani, Raffa, Pizzorusso, Menciassi, & Dario, 2008). Fast delivery of antibiotic small molecules is needed for acute injuries and wounds in order to control infections. For this purpose, Kataria et al. developed a ciprofloxacin-loaded PVA/SA electrospun nanofibrous transdermal patch. The patch followed the Higuchi and Korsmeyer-Peppas model for drug release and decreased the healing time of the wound in comparison to unloaded patch (Kataria et al., 2014). In addition, it has been shown that blended fibers of sodium alginate/PEO/soy protein are promising

of

nanomaterials for drug delivery and tissue engineering applications. Presence of soy protein (SPI)

ro

in this system when is encapsulated with vancomycin decreases the release rate of vancomycin compared to neat SA/PEO nanofibers and enhances biocompatibility of the fibers. This

-p

nanocomposite inhibits bacterial growth against Staphylococcus aureus after 24 h of incubation

re

(Wongkanya et al., 2017).

The alginate nanofibers could also be used to deliver biomacromolecules and proteins as well as

lP

small molecules (Vigani et al., 2018). Doğaç et al. reported that immobilizing lipase on alginatebased nanofibers improves stability properties of this enzyme such as optimum temperature,

ur na

optimum pH, thermal stability, pH stability and reusability. Therefore, this alginate-based nanofibrous system would be an appropriate carrier to immobilize enzymes (Doğaç et al., 2017). Recently, a nanofibrous scaffold of PVA/sulfated alginate was fabricated for transforming growth factor-beta1 (TGF-β1) delivery. Sulfation of alginate provides affinity sites for growth factor

Jo

binding and enables their release in a controlled way. The results of this research showed that this nanofibrous scaffold is potentially suitable for tissue engineering applications (Mohammadi et al., 2019).

5.4. Other applications

21

Besides biomedical applications, alginate nanofibers can be used for different applications for example, biosensors and pollution absorbents. Hu et al., fabricated a wearable pressure sensor by immobilizing silver nanoparticles into the electrospun sodium alginate nanofibers. In addition to following human respiration, this pressure sensor could distinguish words spoken by a tester. Moreover, these Ag/alginate nanofibers showed great antibacterial properties (Hu et al., 2017). Water purification with ability of dye and oil separation is another application of alginate

of

nanofibers with development of a high flux three-layer membrane. A membrane composed of a

ro

coating layer based on chitosan and silver nanoparticles containing chitosan, a midlayer of electrospun alginate and a nonwoven layer for mechanical supporting of the membrane (Mokhena

-p

& Luyt, 2017). Zhang et al., produced a humidity sensor which is able to attach to a 3M-9001V

re

mask for monitoring human breath during exercise and emotion changes. This smart mask was made of alginate nanofibers assembled with silver nanoparticles and fabricated through three steps

lP

including electrospinning of sodium alginate, ion exchange between the sodium and silver ions, and in situ reduction of silver nanoparticles (Zhang et al., 2018).

ur na

6. Conclusion

Electrospun nanofibers obtained from natural polymers have found wide applications in medicine, drug delivery systems, wound dressings and tissue engineering. Alginate is one of these natural polymers with desirable properties. However, to date the electrospinning of pure alginate has not

Jo

been possible, and the methods were used in fabrication of nanofibers with high amounts of alginate have not been successful. Adding carrier polymers such as polyethylene oxide and polyvinyl alcohol is one of the most commonly used methods to electrospin alginate successfully. Moreover, co-solvents and surfactants can be used to increase the content of alginate in nanofibrous mats and to improve electrospinnability of alginate. Paying attention to important

22

factors of alginate electrospinning such as chain entanglement of alginate polymer, viscosity, surface tension and conductivity of the electrospinning solution and the way which polymers or solvents affect these factors can provide newer and more effective approaches for electrospinning of this valuable polymer. One of the most important applications of nanofibers is wound dressings. Alginate is an ideal option for this purpose due to its favorable properties such as high moisture absorption, being non-adhesive to the surface of the wound, biocompatibility and non-toxicity.

of

Alginate nanofibers with controlled porosity obtained from electrospinning are permeable to

ro

moisture and oxygen but not permeable to microorganism. Moreover, high surface area to volume ratio leads to excess wound fluid absorption and controls the amount of wound moisture at its

-p

normal value. These characteristics provide optimum conditions that accelerates wound healing.

re

In addition to wound dressing, high surface area to volume ratio, controlled porosity and also the ability of increasing drugs solubility and adjusting its release rate by changing the electrospinning

lP

conditions have made alginate nanofibers suitable for drug delivery. Various methods including the core-shell electrospinning have been developed to load a drug into a polymer matrix. Apart

ur na

from that, alginate nanofibers can be used in tissue engineering due to the structural and dimensional similarity to the extracellular matrix and their ability to be functionalized by agents

Jo

to enable cell adhesion and growth.

23

References

Aadil, K. R., Nathani, A., Sharma, C. S., Lenka, N., & Gupta, P. (2018). Fabrication of biocompatible alginate-poly (vinyl alcohol) nanofibers scaffolds for tissue engineering applications. Materials Technology, 33(8), 507-512. Aderibigbe, B., & Buyana, B. (2018). Alginate in wound dressings. Pharmaceutics, 10(2), 42.

of

Arlov, Ø., Aachmann, F. L., Sundan, A., Espevik, T., & Skjåk-Bræk, G. (2014). Heparin-like

ro

properties of sulfated alginates with defined sequences and sulfation degrees. Biomacromolecules, 15(7), 2744-2750.

-p

Augst, A. D., Kong, H. J., & Mooney, D. J. (2006). Alginate hydrogels as biomaterials.

re

Macromolecular Bioscience, 6(8), 623-633.

Batista, P. S. P., de Morais, A. M. M. B., Pintado, M. M. E., & de Morais, R. M. S. C. (2019).

lP

Alginate: Pharmaceutical and Medical Applications. In Extracellular Sugar-Based Biopolymers Matrices, Extracellular Sugar-Based Biopolymers Matrices (pp. 649-691): Springer

ur na

Bhardwaj, N., & Kundu, S. C. (2010). Electrospinning: a fascinating fiber fabrication technique. Biotechnology Advances, 28(3), 325-347. Bhattarai, N., & Zhang, M. (2007). Controlled synthesis and structural stability of alginate-based nanofibers. Nanotechnology, 18(45), 455601.

Jo

Bonino, C. A., Efimenko, K., Jeong, S. I., Krebs, M. D., Alsberg, E. et al. (2012). Three‐ dimensional electrospun alginate nanofiber mats via tailored charge repulsions. Small, 8(12), 1928-1936.

24

Bonino, C. A., Krebs, M. D., Saquing, C. D., Jeong, S. I., Shearer, K. L. et al. (2011). Electrospinning alginate-based nanofibers: From blends to crosslinked low molecular weight alginate-only systems. Carbohydrate Polymers, 85(1), 111-119. Borgogna, M., Skjåk-Bræk, G., Paoletti, S., & Donati, I. (2013). On the initial binding of alginate by calcium ions. The tilted egg-box hypothesis. The Journal of Physical Chemistry B, 117(24), 7277-7282.

of

Chae, T., Yang, H., Leung, V., Ko, F., & Troczynski, T. (2013). Novel biomimetic

Materials Science: Materials in Medicine, 24(8), 1885-1894.

ro

hydroxyapatite/alginate nanocomposite fibrous scaffolds for bone tissue regeneration. Journal of

-p

Chang, J. J., Lee, Y. H., Wu, M. H., Yang, M. C., & Chien, C. T. (2012). Preparation of electrospun

re

alginate fibers with chitosan sheath. Carbohydrate Polymers, 87(3), 2357-2361. Ching, S. H., Bansal, N., & Bhandari, B. (2017). Alginate gel particles–A review of production

lP

techniques and physical properties. Critical Reviews in Food Science Nutrition, 57(6), 1133-1152. Ciofani, G., Raffa, V., Pizzorusso, T., Menciassi, A., & Dario, P. (2008). Characterization of an

ur na

alginate-based drug delivery system for neurological applications. Medical Engineering Physics, 30(7), 848-855.

Daemi, H., & Barikani, M. (2014). Molecular engineering of manipulated alginate-based polyurethanes. Carbohydrate Polymers, 112, 638-647.

Jo

Daemi, H., & Barikani, M. (2012). Synthesis and characterization of calcium alginate nanoparticles, sodium homopolymannuronate salt and its calcium nanoparticles. Scientia Iranica, 19(6), 2023-2028.

Daemi, H., Barikani, M., & Sardon, H. (2017). Transition-metal-free synthesis of supramolecular ionic alginate-based polyurethanes. Carbohydrate Polymers, 157, 1949-1954.

25

Daemi, H., Mashayekhi, M., & Pezeshki Modaress, M. (2018). Facile fabrication of sulfated alginate electrospun nanofibers. Carbohydrate Polymers, 198, 481-485. Daemi, H., Rezaieyeh Rad, R., Adib, M., & Barikani, M. (2014). Sodium alginate: A renewable and very effective biopolymer catalyst for the synthesis of 3, 4-dihydropyrimidin-2 (1H)-ones. Scientia Iranica, 21(6), 2076. Daemi, H., Rajabi-Zeleti, S., Sardon, H., Barikani, M., Khademhosseini, A. et al. (2016). A robust

of

super-tough biodegradable elastomer engineered by supramolecular ionic interactions.

ro

Biomaterials, 84, 54-63.

Dekamin, M. G., Karimi, Z., Latifidoost, Z., Ilkhanizadeh, S., Daemi, H., et al. (2018). Alginic

-p

acid: A mild and renewable bifunctional heterogeneous biopolymeric organocatalyst for efficient

re

and facile synthesis of polyhydroquinolines. International Journal of Biological Macromolecules, 108, 1273-1280.

lP

De Silva, R. T., Dissanayake, R. K., Mantilaka, M. P. G., Wijesinghe, W. S. L., Kaleel, S. S. et al. (2018). Drug-loaded halloysite nanotube-reinforced electrospun alginate-based nanofibrous

ur na

scaffolds with sustained antimicrobial protection. ACS Applied Materials Interfaces, 10(40), 33913-33922.

Doğaç, Y. İ., Deveci, İ., Mercimek, B., & Teke, M. (2017). A comparative study for lipase immobilization onto alginate based composite electrospun nanofibers with effective and enhanced

Jo

stability. International Journal of Biological Macromolecules, 96, 302-311.

Esfandiari, F., Ashtiani, M. K., Sharifi-Tabar, M., Saber, M., Daemi, H., et al. (2017). Microparticle-Mediated Delivery of BMP4 for Generation of Meiosis-Competent Germ Cells from Embryonic Stem Cells. Macromolecular Bioscience, 17(3), 1600284.

26

Fang, D., Liu, Y., Jiang, S., Nie, J., & Ma, G. (2011). Effect of intermolecular interaction on electrospinning of sodium alginate. Carbohydrate Polymers, 85(1), 276-279. Garg, K., & Bowlin, G. L. (2011). Electrospinning jets and nanofibrous structures. Biomicrofluidics, 5(1), 013403. Grant, G. T., Morris, E. R., Rees, D. A., Smith, P. J. C., & Thom, D. (1973). Biological interactions between polysaccharides and divalent cations: The egg-box model. FEBS Letters, 32(1), 195-198.

of

Hajiali, H., Heredia-Guerrero, J. A., Liakos, I., Athanassiou, A., & Mele, E. (2015). Alginate

ro

nanofibrous mats with adjustable degradation rate for regenerative medicine. Biomacromolecules, 16(3), 936-943.

-p

Hashimoto, T., Suzuki, Y., Tanihara, M., Kakimaru, Y., & Suzuki, K. (2004). Development of

Biomaterials, 25(7-8), 1407-1414.

re

alginate wound dressings linked with hybrid peptides derived from laminin and elastin.

lP

Hsu, S. H, Whu, S. W., Hsieh, S. C., Tsai, C. L., Chen, D. C. et al. (2004). Evaluation of chitosan‐ alginate‐hyaluronate complexes modified by an RGD‐containing protein as tissue‐engineering

ur na

scaffolds for cartilage regeneration. Artificial Organs, 28(8), 693-703. Hu, W. P., Zhang, B., Zhang, J., Luo, W. L., Guo, Y. et al. (2017). Ag/alginate nanofiber membrane for flexible electronic skin. Nanotechnology, 28(44), 445502. Hu, W. W., Lin, C. H., & Hong, Z. J. (2019). The enrichment of cancer stem cells using composite

Jo

alginate/polycaprolactone nanofibers. Carbohydrate Polymers, 206, 70-79.

Hu, W. W., & Yu, H. N. (2013). Coelectrospinning of chitosan/alginate fibers by dual-jet system for modulating material surfaces. Carbohydrate Polymers, 95(2), 716-727.

27

Islam, M. S., Karim, M. R. J. C., Physicochemical, S. A., & Aspects, E. (2010). Fabrication and characterization of poly (vinyl alcohol)/alginate blend nanofibers by electrospinning method. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 366(1-3), 135-140. Iwasaki, N., Yamane, S. T., Majima, T., Kasahara, Y., Minami, A., et al. (2004). Feasibility of polysaccharide hybrid materials for scaffolds in cartilage tissue engineering:  evaluation of chondrocyte adhesion to polyion complex fibers prepared from alginate and chitosan.

of

Biomacromolecules, 5(3), 828-833.

ro

Jeong, S. I., Krebs, M. D., Bonino, C. A., Samorezov, J. E., Khan, S. A. et al. (2010). Electrospun chitosan–alginate nanofibers with in situ polyelectrolyte complexation for use as tissue

-p

engineering scaffolds. Tissue Engineering Part A, 17(1-2), 59-70.

re

Jeong, S. I., Jeon, O., Krebs, M. D., Hill, M. C., & Alsberg, E. (2012). Biodegradable photocrosslinked alginate nanofibre scaffolds with tuneable physical properties, cell adhesivity and

lP

growth factor release. European Cells & Materials, 24, 331-343. Kataria, K., Gupta, A., Rath, G., Mathur, R., & Dhakate, S. (2014). In vivo wound healing

ur na

performance of drug loaded electrospun composite nanofibers transdermal patch. International Journal of Pharmaceutics, 469(1), 102-110. Khan, F., & Ahmad, S. R. (2013). Polysaccharides and Their Derivatives for Versatile Tissue Engineering Application. Macromolecular Bioscience, 13(4), 395-421.

Jo

Khil, M. S., Cha, D. I., Kim, H. Y., Kim, I. S., & Bhattarai, N. (2003). Electrospun nanofibrous polyurethane membrane as wound dressing. Journal of Biomedical Materials Research Part B: Applied Biomaterials, 67(2), 675-679.

Kim, M. S., & Kim, G. (2014). Three-dimensional electrospun polycaprolactone (PCL)/alginate hybrid composite scaffolds. Carbohydrate Polymers, 114, 213-221.

28

Kyzioł, A., Michna, J., Moreno, I., Gamez, E., & Irusta, S. (2017). Preparation and characterization of electrospun alginate nanofibers loaded with ciprofloxacin hydrochloride. European Polymer Journal, 96, 350-360. Lee, K. Y., Jeong, L., Kang, Y. O., Lee, S. J., & Park, W. H. (2009). Electrospinning of polysaccharides for regenerative medicine. Advanced Drug Delivery Reviews, 61(12), 1020-1032. Lee, K. Y., & Mooney, D. J. (2012). Alginate: Properties and biomedical applications. Progress

of

in Polymer Science, 37(1), 106-126.

ro

Leung, V., Hartwell, R., Elizei, S. S., Yang, H., Ghahary, A. et al. (2014). Postelectrospinning modifications for alginate nanofiber‐based wound dressings. Journal of Biomedical Materials

-p

Research Part B: Applied Biomaterials, 102(3), 508-515.

re

Li, D., & Xia, Y. (2004). Electrospinning of Nanofibers: Reinventing the Wheel? Advanced Materials, 16(14), 1151-1170.

lP

Li, W., Li, X., Chen, Y., Li, X., Deng, H. et al. (2013). Poly (vinyl alcohol)/sodium alginate/layered silicate based nanofibrous mats for bacterial inhibition. Carbohydrate Polymers, 92(2), 2232-

ur na

2238.

Li, W. J., Laurencin, C. T., Caterson, E. J., Tuan, R. S., & Ko, F. K. (2002). Electrospun nanofibrous structure: a novel scaffold for tissue engineering. Journal of Biomedical Materials Research, 60(4), 613-621.

Jo

Li, Z., & Zhang, M. (2005). Chitosan–alginate as scaffolding material for cartilage tissue engineering. Journal of Biomedical Materials Research Part A, 75(2), 485-493.

Lim, C. T. (2017). Nanofiber technology: current status and emerging developments. Progress in Polymer Science, 70, 1-17.

29

Ma, G., Fang, D., Liu, Y., Zhu, X., & Nie, J. (2012). Electrospun sodium alginate/poly (ethylene oxide) core–shell nanofibers scaffolds potential for tissue engineering applications. Carbohydrate Polymers, 87(1), 737-743. Majidi, S. S., Slemming-Adamsen, P., Hanif, M., Zhang, Z., Wang, Z. et al. (2018). Wet electrospun alginate/gelatin hydrogel nanofibers for 3D cell culture. International Journal of Biological Macromolecules, 118, 1648-1654.

of

Matricardi, P., Di Meo, C., Coviello, T., Hennink, W. E., & Alhaique, F. (2013). Interpenetrating

ro

Polymer Networks polysaccharide hydrogels for drug delivery and tissue engineering. Advanced Drug Delivery Reviews, 65(9), 1172-1187.

-p

Mohammadi, S., Ramakrishna, S., Laurent, S., Shokrgozar, M. A., Semnani, D. et al. (2019).

re

Fabrication of Nanofibrous PVA/Alginate‐Sulfate Substrates for Growth Factor Delivery. Journal of Biomedical Materials Research Part A, 107(2), 403-413.

lP

Mokhena, T., & Luyt, A. (2017). Electrospun alginate nanofibres impregnated with silver nanoparticles: Preparation, morphology and antibacterial properties. Carbohydrate Polymers, 165,

ur na

304-312.

Moon, S., & Farris, R. J. (2009). Electrospinning of heated gelatin‐sodium alginate‐water solutions. Polymer Engineering & Sccience, 49(8), 1616-1620. Moon, S., Ryu, B. Y., Choi, J., Jo, B., & Farris, R. J. (2009). The morphology and mechanical

Jo

properties of sodium alginate based electrospun poly (ethylene oxide) nanofibers. Polymer Engineering Science, 49(1), 52-59.

Morris, E. R., Rees, D. A., Thom, D., & Boyd, J. (1978). Chiroptical and stoichiometric evidence of a specific, primary dimerisation process in alginate gelation. Carbohydrate Research, 66(1), 145-154.

30

Ni, P., Bi, H., Zhao, G., Han, Y., Wickramaratne, M. N. et al. (2019). Electrospun preparation and biological properties in vitro of polyvinyl alcohol/sodium alginate/nano-hydroxyapatite composite fiber membrane. Colloids Surfaces B: Biointerfaces, 173, 171-177. Nie, H., He, A., Zheng, J., Xu, S., Li, J., & Han, C. C. (2008). Effects of chain conformation and entanglement on the electrospinning of pure alginate. Biomacromolecules, 9(5), 1362-1365. Nista, S. V. G., Bettini, J., & Mei, L. H. I. (2015). Coaxial nanofibers of chitosan–alginate–PEO

of

polycomplex obtained by electrospinning. Carbohydrate Polymers, 127, 222-228.

ro

Otterlei, M., Ostgaard, K., Skjåk-Bræk, G., Smidsrød, O., Soon-Shiong, P. et al. (1991). Induction of cytokine production from human monocytes stimulated with alginate. Journal of

-p

Immunotherapy: Official Journal of The Society for Biological Therapy, 10(4), 286-291.

re

Park, S. A., Park, K. E., & Kim, W. (2010). Preparation of sodium alginate/poly (ethylene oxide) blend nanofibers with lecithin. Macromolecular Research, 18(9), 891-896.

lP

Pattison, M. A., Wurster, S., Webster, T. J., & Haberstroh, K. M. (2005). Three-dimensional, nanostructured PLGA scaffolds for bladder tissue replacement applications. Biomaterials, 26(15),

ur na

2491-2500.

Pawar, S. N., & Edgar, K. J. (2012). Alginate derivatization: A review of chemistry, properties and applications. Biomaterials, 33(11), 3279-3305. Pezeshki-Modaress, M., Mirzadeh, H., & Zandi, M. (2015). Gelatin–GAG electrospun nanofibrous

Jo

scaffold for skin tissue engineering: Fabrication and modeling of process parameters. Materials Science and Engineering: C, 48, 704-712.

Qin, Y. (2008). Alginate fibres: an overview of the production processes and applications in wound management. Polymer International, 57(2), 171-180.

31

Ramakrishna, S., Fujihara, K., Teo, W.-E., Yong, T., Ma, Z., & Ramaseshan, R. (2006). Electrospun nanofibers: solving global issues. Materials Today, 9(3), 40-50. Rho, K. S., Jeong, L., Lee, G., Seo, B.-M., Park, Y. J. et al. (2006). Electrospinning of collagen nanofibers: effects on the behavior of normal human keratinocytes and early-stage wound healing. Biomaterials, 27(8), 1452-1461. Saberi, A., Rafienia, M., & Poorazizi, E. (2017). A novel fabrication of PVA/Alginate-Bioglass

of

electrospun for biomedical engineering application. Nanomedicine Journal, 4(3), 152-163.

ro

Safi, S., Morshed, M., Hosseini Ravandi, S., & Ghiaci, M. (2007). Study of electrospinning of sodium alginate, blended solutions of sodium alginate/poly (vinyl alcohol) and sodium

-p

alginate/poly (ethylene oxide). Journal of Applied Polymer Science, 104(5), 3245-3255.

re

Sahraro, M., Barikani, M., & Daemi, H. (2018). Mechanical reinforcement of gellan gum polyelectrolyte hydrogels by cationic polyurethane soft nanoparticles. Carbohydrate Polymers,

lP

187, 102-109.

Saquing, C. D., Tang, C., Monian, B., Bonino, C. A., Manasco, J. L. et al. (2013). Alginate–

ur na

polyethylene oxide blend nanofibers and the role of the carrier polymer in electrospinning. Industrial Engineering Chemistry Research, 52(26), 8692-8704. Schiffman, J. D., & Schauer, C. L. (2008). A review: electrospinning of biopolymer nanofibers and their applications. Polymer Reviews, 48(2), 317-352.

Jo

Shalumon, K., Anulekha, K., Nair, S. V., Nair, S., Chennazhi, K. et al. (2011). Sodium alginate/poly (vinyl alcohol)/nano ZnO composite nanofibers for antibacterial wound dressings. International Journal of Biological Macromolecules, 49(3), 247-254.

Shen, W., & Hsieh, Y.-L. (2014). Biocompatible sodium alginate fibers by aqueous processing and physical crosslinking. Carbohydrate Polymers, 102, 893-900.

32

Sobhanian, P., Khorram, M., Hashemi, S.-S., & Mohammadi, A. (2019). Development of nanofibrous collagen-grafted poly (vinyl alcohol)/gelatin/alginate scaffolds as potential skin substitute. International Journal of Biological Macromolecules, 130, 977-987. Stone, S. A., Gosavi, P., Athauda, T. J., & Ozer, R. R. (2013). In situ citric acid crosslinking of alginate/polyvinyl alcohol electrospun nanofibers. Materials Letters, 112, 32-35. Suh, J. K. F., & Matthew, H. W. (2000). Application of chitosan-based polysaccharide biomaterials

of

in cartilage tissue engineering: a review. Biomaterials, 21(24), 2589-2598.

ro

Tang, Y., Lan, X., Liang, C., Zhong, Z., Xie, R. et al. (2019). Honey loaded alginate/PVA nanofibrous membrane as potential bioactive wound dressing. Carbohydrate Polymers, 219, 113-

-p

120.

re

Tarun, K., & Gobi, N. (2012). Calcium alginate/PVA blended nano fibre matrix for wound dressing. Indian Journal of Fibre & Textile Research, 37, 127-132.

lP

Torabi, A., Sahraro, M., Barikani, M., & Daemi, H. (2019). Green synthesis of in situ forming alginate-urethane hydrogel through Schiff base reaction. Materials Letters, 254, 194-197.

ur na

Vigani, B., Rossi, S., Sandri, G., Bonferoni, M. C., Milanesi, G. et al. (2018). Coated electrospun alginate-containing fibers as novel delivery systems for regenerative purposes. International Journal of Nanomedicine, 13, 6531-6550. Wang, Q., Ju, J., Tan, Y., Hao, L., Ma, Y., et al. (2019). Controlled synthesis of sodium alginate

Jo

electrospun nanofiber membranes for multi-occasion adsorption and separation of methylene blue. Carbohydrate Polymers, 205, 125-134.

Wnek, G. E., Carr, M. E., Simpson, D. G., & Bowlin, G. L. (2003). Electrospinning of nanofiber fibrinogen structures. Nano Letters, 3(2), 213-216.

33

Wongkanya, R., Chuysinuan, P., Pengsuk, C., Techasakul, S., Lirdprapamongkol, K. et al. (2017). Electrospinning of alginate/soy protein isolated nanofibers and their release characteristics for biomedical applications. Journal of Science: Advanced Materials Devices, 2(3), 309-316. Xiao, Q., & Lim, L. T. (2018). Pullulan-alginate fibers produced using free surface electrospinning. International Journal of Biological Macromolecules, 112, 809-817. Xu, W., Shen, R., Yan, Y., & Gao, J. (2017). Preparation and characterization of electrospun

of

alginate/PLA nanofibers as tissue engineering material by emulsion eletrospinning. Journal of The

ro

Mechanical Behavior of Biomedical Materials, 65, 428-438.

Yu, C. C., Chang, J. J., Lee, Y. H., Lin, Y. C., Wu, M. H. et al. (2013). Electrospun scaffolds

-p

composing of alginate, chitosan, collagen and hydroxyapatite for applying in bone tissue

re

engineering. Materials Letters, 93, 133-136.

Zhang, J., Wang, X. X., Zhang, B., Ramakrishna, S., Yu, M. et al. (2018). In situ assembly of well-

lP

dispersed Ag nanoparticles throughout electrospun alginate nanofibers for monitoring human breath—Smart fabrics. ACS Applied Materials & Interfaces, 10(23), 19863-19870.

ur na

Zhang, Y., Lim, C. T., Ramakrishna, S., & Huang, Z. M. (2005). Recent development of polymer nanofibers for biomedical and biotechnological applications. Journal of Materials Science: Materials in Medicine, 16(10), 933-946. Zhao, X., Chen, S., Lin, Z., & Du, C. (2016). Reactive electrospinning of composite nanofibers of

Jo

carboxymethyl chitosan cross-linked by alginate dialdehyde with the aid of polyethylene oxide. Carbohydrate Polymers, 148, 98-106.

Zhao, X., Yu, G., Guan, H., Yue, N., Zhang, Z. et al. (2007). Preparation of low-molecular-weight polyguluronate sulfate and its anticoagulant and anti-inflammatory activities. Carbohydrate Polymers, 69(2), 272-279.

34

Table 1. The content of SA (wt.%) at final mat and electrospinning conditions of studies in which PVA or PEO were used as the carrier polymer. Carrier SA content at

Tip to collector Voltage

Flow rate

polymer

Reference final mat (wt.%) distance (cm)

(kV)

(mL/h)

(CP) 15

15

0.5

(Kataria et al., 2014)

11

5

17

0.1

(Shalumon et al., 2011)

5.97

-

16-18

-

(Tarun & Gobi, 2012)

10

10

15

0.4

11.76

17

ro

Hashemi, & Mohammadi,

(Ni et al., 2019)

15

-

(Islam & Karim, 2010)

15

10-12

2019)

(Moon, Ryu, Choi, Jo, &

9-12

0.06-0.36

Farris, 2009)

10

13

Jo

33.33

0.2

0.32

13.5

ur na

25-50

PEO

20

(Sobhanian, Khorram,

re

6.6

10

lP

20

(Tang et al., 2019)

-p

PVA

of

4.2

35

1.2

(Jeong et al., 2010)

Table 2. Different co-solvents and surfactants were used for electrospinning of alginate Carrier polymer (CP)

SA content at Co-solvent

Surfactant

Reference

-

Pluronic F127

final mat (%) (Bonino et al., 7.2

2012) -

Lecithin

60

Ethanol

-

(Nista et al., 2015)

ro

PEO

(Park et al., 2010)

of

25-75

(Mokhena & Luyt,

16.6

-

Jo

ur na

PVA

Triton X-100

-p

-

lP

50

DMSO

36

2017)

(Doğaç et al.,

Triton X-100

re

50

2017) (Doğaç et al.,

Triton X-100 2017)