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UV protection and antibacterial properties of seaweed capped ZnO nanoparticles coated cotton fabrics
Accepted Manuscript Title: UV protection and antibacterial properties of seaweed capped ZnO nanoparticles coated cotton fabrics Authors: R. Pandimurugan, S. Thambidurai PII: DOI: Reference:
S0141-8130(17)31783-X http://dx.doi.org/doi:10.1016/j.ijbiomac.2017.07.097 BIOMAC 7905
To appear in:
International Journal of Biological Macromolecules
Received date: Revised date: Accepted date:
19-5-2017 2-7-2017 15-7-2017
Please cite this article as: R.Pandimurugan, S.Thambidurai, UV protection and antibacterial properties of seaweed capped ZnO nanoparticles coated cotton fabrics, International Journal of Biological Macromoleculeshttp://dx.doi.org/10.1016/j.ijbiomac.2017.07.097 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. 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.
UV protection and antibacterial properties of seaweed capped ZnO nanoparticles coated cotton fabrics R.Pandimurugan, S.Thambidurai*
Bio-nanomaterials Research Lab, Department of Industrial chemistry, School of Chemical Sciences, Alagappa University, Karaikudi-630003, Tamil Nadu, India.
Email: [email protected] (S.Thambidurai) Tel.: +91 4565 228836; fax: +91 4565 225202.
Research highlights
The SW-ZnO NPs were synthesized by simple chemical precipitation methods.
As synthesized nanoparticles coated with cotton fabric by pad dry cure techniques.
For comparison to seaweed extracts also coated in coated fabric
Study the antibacterial and UV protection properties of all coated cotton fabrics.
ABSTRACT Seaweed capped zinc oxide nanoparticles (SW-ZnO NPs) were prepared by simple chemical precipitation method of zinc nitrate in the presence of seaweed. The synthesised 1
SW-ZnO NPs were characterised by FT-IR, UV-Visible spectroscopy, XRD and BET analysis. These metal oxides were coated on cotton fabric using pad dry cure technique. The SW-ZnO NPs coated cotton fabrics, the surface morphology and chemical composition was analysed by HR-SEM with EDAX. The antibacterial activity of uncoated cotton, seaweed extract and SW-ZnO NPs coated cotton fabrics were investigated against Gram positive (S. aureus and S. pyogenes) and Gram negative (E. coli and K. aerogens). It showed that SW-ZnO NPs coated cotton fabric has higher antibacterial activity than other test samples against both bacteria’s. Finally, a UV-protection property of the coated cotton fabric was also tested. Keywords: Zinc oxide, Seaweed, Cotton fabric, Antibacterial activity, UV protection.
1. Introduction Cotton is one of the most abundant and widely used natural fibres in the world. Owing to its strong absorption capability, high specific surface, porous structure, bio-degradable and less cost, use of cotton has been extended from wear to technical textiles [1-3]. Despite the excellent properties of cotton fabrics, some characters like the inherently hydrophilic property, impotent antibacterial activity, low strength and poor sensitivity to the UV light, confine their wide applications, especially in some high-ends areas for medicine, personal healthcare, functional textile and self-cleaning [4-6]. Therefore, value addition to cotton by functionalization has generated considerable academic and industrial attention, not only due to their potential use in physical, thermal, biological and medical protection, but also meet the constantly evolving demand from consumers for advanced materials. Apart from the esthetical purpose of cotton, the value added cotton materials have become a basis for many industrial and technical applications [7-12].
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Bio-nanocomposite, a new generation of bio-nanocomposite materials, signifies an emerging field in the frontier of nanotechnology, materials science, life science [13-14]. Bio nanocomposite is composed of a natural polymer matrix and organic/inorganic filler with at least one dimension on the nanometer scale. These bio-nanocomposites show the remarkable advantages of biodegradability and biocompatibility in various medical, agricultural, drug release and packaging application [15]. Seaweeds are the potential renewable resources in the marine environment. About 6000 species of seaweeds have been identified and grouped into different classes viz., green (Chlorophytes), brown (Pheophytes) and red (Rhodophytes) algae. Generally, Macro algae of seaweed have a wide range of industrial and medical applications because of having bioactive compounds such as amines, sulphates, carboxyl and hydroxyl groups [16]. Recently, the synthesis of metal oxide is based semiconductor nanoparticles using seaweed extract from various solvents has been reported. For example, synthesis of silver and gold nanoparticles by using brown seaweed extract as a reducing and stabilizing agent [17-21]. ZnO NPs is one of the various inorganic compounds, which imparts antibacterial properties to textiles [22-23]. It also regards as an excellent UV blocking property over a board range of UV wavelengths with a wide direct band gap (3.37 eV) and large excitation binding energy (60 meV) [24-25] The treatment of cotton fabrics using ZnO NPs for improved UV radiation protection has been achieved by various methods including wet chemical method [26], homogeneous precipitation methods [27], and hydrothermal method [28-29]. There is considerable interest in organic-inorganic hybrid materials. A variety of organic polymers have been introduced into organic networks to afford the hybrid materials with or without covalent bond between the polymer and inorganic components, respectively [30]. In the recent years, many researchers are interested in coated cotton fabric using different metal oxides such as TiO2 NPs [31] ZnO NPs [32-35] Au NPs [36], Ag:ZnO NPs
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[37], SiO2 coated ZnO NPs [38] and SiO2@AgNPs [39] applied to acquire for antibacterial and UV-blocking properties. The inorganic UV blockers are more desirable than organic UV blockers due to their high efficiency at low concentration. In fact, ZnO NPs is well known of its non-toxicity as well as chemically stable under exposure to both high temperature and UV radiation. In addition, nanoparticles are significantly more effective in blocking the UV radiation more than the bulk materials, due to the fact that nanoparticles have a large surface area to volume ratio [40-41]. In this study, we prepared the seaweed capped zinc oxide nanoparticles (SW-ZnO NPs) and applied to cotton fabric by pad dry cure method for enhancing multifunctional properties of antibacterial activity and UV-protection. Furthermore, the characterization of prepared seaweed capped ZnO NPs discussed by means FT-IR, UV-Vis, XRD, BET, HRSEM and EDAX. 2. Experimental 2.1. Material The analytical grade of zinc nitrate (95% pure) and sodium hydroxide (98% pure) were purchased from Fischer Chemic Ltd, Chennai, India. For the brown seaweed of padina tetrastromatica was collected from the Gulf of Mannar, Tamil Nadu, India and washed with seawater followed by thorough washing with fresh water and under air shade. Finally, the dried samples were grind well to fine powder and stored in air tight plastic bag at room temperature. Deionized water was used in all experiment. 2.2. Preparation of seaweed capped zinc oxide nanoparticles (SW-ZnO NPs) The method of preparation of SW-ZnO NPs can be found in our recent paper [42]. Briefly, 12.5 g of zinc nitrate was dissolved in 100 ml distilled water to obtain a 12.5 % of zinc salt solution and 0.5 g of dried seaweed powder was poured into the solution and then 4
the mixture was stirred for 2 h at 80oC to assist the electrostatic attraction of Zn2+ onto the seaweed. After cooling the mixture at room temperature, 25% of fresh sodium hydroxide was drop wise added to the above mixture and left to react for 24 hours. The supernatant clear solution was drained and remaining was washed with distilled water for several times. Finally, the precipitate was filtered using suction pump and dried in hot air oven at 120 oC for 4 h. The sample was designated as SW-LZnO. The above process was followed by the increasing of zinc nitrate concentration from 12.5 % to 25 % and designates as SW-HZnO. 2.3. Coating of SW-ZnO NPs on cotton fabrics About 0.5 g of SW-LZnO NPs was dissolved in 20 ml of PVA and stirred for 1 h with magnetic stirrer at room temperature. The mixture was sonicated for 30 min improve the dispersion of SW-LZnO NPs particles in the solution. About 4 g of bioscoured cotton fabric was immersed in the SW-LZnO NPs into PVA solution for 30 min and padded in the padding mangle, squeezed between two squeezing rollers for 80% wet pick-up. The padded fabric was dried in an oven at 70oC for 10 min and cured in an oven at 150oC for 5 min [43]. The cured fabric was washed well with 1% sodium hydroxide solution, neutralised with 1% acetic acid, washed again and air-dried. The above process was repeated by replacing SW-LZnO with SW-HZnO and seaweed extracts. 2.4. Characterizations FT-IR spectra were recorded for seaweed capped zinc oxide nanoparticles using FTIR, SHIMADZU. Samples (0.02 g) were mixed with potassium bromide (KBr) and IR spectra were scanned over wave number range of 4000-400 cm-1. The optical absorption spectra of all the samples were obtained by use of a JASCO UV-Vis NIR (V-670) in the wavelength range of 200 - 800 nm. X-ray diffraction (XRD) studies were carried out in a 2θ range of 10– 80o using an X-ray diffractometer ((X'Pert PRO diffractometer) with Cu Kα radiation 5
(λ = 0.15406 nm). Nitrogen adsorption-desorption isotherms were performed with an ASAP 2020 Micromeritics analyzer at 77 K. The specific surface areas were determined by Brunauer – Emmett – Teller (BET) method. The pore size distribution was calculated according to the Berrett-Joyner-Halenda (BJH) method. The surface morphology of ZnO NPs treated cotton fabric samples were observed using FEI quanta FEG 250 instrument operated in an accelerating voltage at 10 kV. The elemental analysis of ZnO NPs treated cotton fabric was performed using EDAX, which is an attachment to the HR-SEM. 2.5. Antibacterial test The antibacterial activities of pure cotton, seaweed extracts and SW-ZnO NPs coated cotton fabrics were investigated by two techniques viz. agar diffusion method and reduction of colony forming units (CFU) of two strains of gram positive microorganism, staphylococcus (S. aureus), streptococcus pyogenes (S. pyogenes) and two strains of gram negative microorganism Escherichia coli (E. coli), Klbesiella aerogenes (K. aeroenes) [44]. For qualitative measurements, the samples were put together to form a circular zone, and the antimicrobial activity was tested using modified agar diffusion assay. The plates were kept at 37oC overnight incubation. After incubation, inhibition zone was measured with zone measurement scale. The diameter of the zone of inhibition was then examined directly underneath and around the sample. The inhibition cleared a zone in and around the sample determined the efficiency of the antibacterial agent to inhibit the growth of bacteria. The uncoated cotton fabric was used as blank or negative control and the standard antibiotic Amikacin used as positive control. All the experiment was conducted in triplicate under the same set of conditions. The study of the cell reduction activity of coated samples was performed using the colony count method. One gram of fabric was cut into small pieces and added with approximate volume of 106 CFU/ml of the gram positive and gram negative bacteria in 6
Muller-Hinton broth and incubated at 37oC on shaking platform at 250 rpm for 24 h. Control broth with untreated cotton fabric was also used. The antibacterial activity was expressed in terms of the percent reduction of the organism after contact with the test specimen compared to the number of bacterial cells surviving after contact with the control. The percentage of CFU was calculated by the following equation
Reduction in CFU (%) =
CA C
x 100%
--------- (1)
Where, C and A are the bacterial colonies of the untreated and the treated cotton fabrics respectively.
3. Result and Discussions 3.1. FT-IR Spectroscopy FT-IR analysis was used to study the interaction between the nano ZnO and seaweed. Fig. 1a-c demonstrates FT-IR spectra of seaweed, SW-LZnO and SW-HZnO. The characteristic peaks of seaweed (Fig.1 a) due to cellulosic macromolecule appear at 3409 cm1
(O-H stretching), 2921 cm-1 (C-H stretching), 1429 cm-1 (C-H wagging), 1369 cm-1 (C-H
bending) and 1032 cm-1 (C-O stretching) [45]. The peaks at 670 and 601 cm-1 were attributed to asymmetric and symmetric O=S=O deformation of a sulphate group [46-49]. Fig. 1a-b show FT-IR spectra of synthesized SW-ZnO NPs indicates a broad peak at 3355 cm-1 related to O-H vibration. The strong symmetric stretching C=O and C-O presented at 1508 and 1386 cm-1 respectively. The peak at 1042 cm-1 relates to C-O-C groups. The presence of C=O, C-O and C-O-C in FT-IR spectra could be due to zinc salt precursor [50]. The ZnO peak also appeared at 426 cm-1 related to Zn-O bonds [51]. Seaweed consists of two major bioactive compounds such as β-D-mannuronic and α-L-guluronic acids which have the functional 7
groups of -COO- and -OH sites. These groups may bind the zinc ions present in the reaction mixture and can stabilize nanoparticles from formation of agglomeration [42]. 3.2. UV-Visible Spectroscopy Fig. 2a-b shows the UV–Vis absorbance of SW-ZnO NPs with different levels of concentration of zinc precursors. An absorption peak appeared at 366 and 370 nm for SWLZnO and SW-HZnO, respectively, while the peak in the bulk ZnO appeared at 372 nm. The absorption peak of seaweed extract capped ZnO NPs exhibited an obvious blue-shift phenomenon due to the quantum confinement effect. The UV absorbance and intensity of the peak varied ZnO NPs from the concentration of zinc nitrate, which is commonly attributed to charge transfer from the valence to a conduction band of nanostructures or particles that have wide particle size distribution [52-53]. The band gap energies of all samples were calculated using the following equation (ahv)2 ED (hv Eg) (2)
where α is the optical absorption coefficient, hν is the photon energy, Eg is the direct band gap and ED is the constant. The extrapolation of the linear portion of the graph (αhν) 2 versus hν when extrapolating to the zero is a direct band gap (Eg) value. The calculated band gap energy was 3.2 and 3.16 eV for SW-LZnO and SW-HZnO samples respectively. The insert Fig. 2 show the absorption spectrum of seaweed extracts in methanol solvents show the three absorption peak at 328, 408 and 667 nm which are characteristics of the seaweed [54]. 3.3. X-ray diffraction analysis Fig. 3a-b shows the XRD patterns of SW-ZnO NPs of SW-LZnO and SW-HZnO. It can be seen from the figure that the XRD pattern could be assigned to hexagonal ZnO, which is in good agreement with that of the standard card JCPDS card #36-1451. These peaks are presented in the SW-ZnO NPs are almost similar to those of the pure ZnO and no peaks
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assigned to seaweed were observed. This might to be content of seaweed layer was too small to be determined [55]. The particle sizes that are calculated from Debye-Schere’s equation (D = 0.94 λ/β cos θ) are 28 and 24 nm for SW-LZnO and SW-HZnO, respectively. Which is mainly depends on the zinc ion concentration is varied from the zinc nitrate. 3.4. BET analysis The porous feature of the SW-ZnO NPs was characterized by BET analysis. Fig. 4 present the nitrogen adsorption-desorption isotherms and BJH pore size distribution curves of SW-ZnO NPs. According to the IUPAC classification [56], the loop observed would be ascribed as type H3 hysteresis loops, indicating the existence of abundant pores. The average pore diameter is around 33.541 nm and the BET surface area of the material is 28.2836 m2/g. The single crystalline phase and porous nature of the SW-ZnO NPs makes it a promising candidate for environment treatment.
3.5. Surface morphology and elemental analysis coated of cotton fabric The surface morphology of the uncoated, seaweed extract and SW-ZnO NPs treated cotton fabric was investigated by HR-SEM and illustrated in Fig.5a-d It was observed from the HR-SEM image of the uncoated cotton fabric (Fig. 5a), grooves and fibrils could be easily observed on the surface of the fibre. While the surface morphology of the treated cotton fabrics were covered with seaweed extract as shown in Fig. 5b. It was also detected with SW-ZnO NPs were well dispersed on surface of the treated fabrics samples (Fig. 5c and d), however, there is some of ZnO NPs aggregated and form large particles will be easily removed from the fibre surface with washing due to the physical adsorption of these particles
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to the outer surface cotton fabrics, on the contrary, the smaller nanoparticles will easily enter deeper and adhere strongly into the pores of fabrics. Chemical composition of uncoated cotton, seaweed extract and SW-ZnO NPs coated cotton fabric obtained by EDAX spectrum are shown in Fig. 6. The uncoated cotton fabric is shown in (Fig. 6a) only for carbon and oxygen element. In Fig 6b show the seaweed content elements such as aluminium, silica, sulphur, silver, calcium, titanium and nickel. Seaweed is a natural polymer that contains polysaccharide and some inorganic elements. A number of studies [57-59] have reported the existence of metals, the relative proportions and the association of the inorganic elements are largely dependent on the cultivation environment and harvesting history. These elements are improving the properties of cotton fabrics. SWZnO NPs coated cotton fabric confirm the presence of Zn, O, and C elements related to cellulose, and nano ZnO (Fig. 6c). It is then proved that the seaweed extracts and SW-ZnO NPs are coated on cotton fabric surfaces.
3.6. Antibacterial activity of SW-ZnO NPs coated cotton fabric The antibacterial property of cotton fabrics were reported as a mean value of the inhibition zone in Table 2. It was calculated according to the following equation:
W=
T D 2
-----------
(3)
Where W is the width of the inhibition zone in mm, and T is the total diameter of test specimens and clear zone, and D is the diameter of the test specimen. It was not seen any inhibition zone surround of uncoated cotton fabric against two types of bacteria. However, 10
the seaweed extracts and SW-ZnO NPs coated cotton fabric presented a clear inhibition zone, and its width was larger against Gram-positive type bacteria compared to Gram-negative type bacteria (Table 1). The greater sensitivity of Gram-positive compared to Gram-negatives bacteria to ZnO nanoparticles is probably due to their difference in the cell membrane structure. The cell membrane of the Gram-negative bacteria composes of lipids, proteins and lipopolysaccharides and cannot provide effective protection [60]. The antibacterial properties of ZnO nanoparticles can be due to reactive oxygen species, probable production of free radicals, and metal ions release [61]. Moreover, it was reported that the antibacterial activity of ZnO nanoparticles depends on the morphology [62]. The SW-HZnO NPs coated cotton fabric presented a large inhibition zone width compared to SW-LZnO NPs coated cotton fabric, because the high concentration of zinc content increase the antibacterial activity. 3.6.1. Colony forming unit The antibacterial activity of SW-ZnO NPs treated cotton before and after washing against gram positive and gram negative bacterial are displayed in Table 2. It was found that the SW-ZnO NPs treated cotton fabrics has more efficient against bacteria while the bacterial reduction of untreated cotton fabric is zero but the SW-ZnO NPs treated cotton fabric reached sufficient value (96.3%) when the cotton fabrics treated with the lowest concentration of zinc nitrate solution. It is also found that the bacterial reduction of cotton fabrics increases marginally with increasing zinc oxide nanoparticles. The particular mechanism of the antibacterial activity of ZnO is still a matter of dispute. Some researchers consider that it might be a consequence of the generation of hydrogen peroxide (H2O2) on its surface [63]. Parallel results were observed against E.coli with insignificant reduction. 3.7. UV blocking studies
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Fig. 7a-d shows the UV transmittance and UV blocking properties of uncoated, seaweed extracts and SW-ZnO NPs coated cotton fabric samples in the range of 200-400 nm. The curve (a) is the UV transmittance curve of the uncoated cotton fabric, demonstrating that almost 49 % of the UV light can penetrate into the uncoated cotton fabric. In curve (b) seaweed extracts coated samples, the transmittance values decreases, which confirm the presence of UV blocking material of seaweed extracts are coated in cotton fabric. UV blocking properties of the SW-ZnO NPs coated cotton fabrics (curve c and d) were compared. Absorption of ZnO blow its band gap, especially at UV (358 -400 nm) portion that can generate highly reactive chemical intermediates, such as hydroxyl and oxygen radicals [64]. It shows that at high concentration SW-ZnO NPs decrease in the value of transmittance compared to lower concentration of SW-ZnO NPs coated cotton fabric and the values are shown in Table 3. UV-blocking results revealed that when the ratio of ZnO increases, the UV blocking efficiency is also increases. 4. Conclusions SW-ZnO NPs were prepared by simple chemical precipitation method in two level of concentration of zinc nitrate such as lower 12.5% and higher 25% are used. FTIR spectra revealed that the chemical interaction between the seaweed and ZnO nanoparticles and confirm the attachment seaweed moieties to ZnO due to the formation of a seaweed-zinc ion network. The hexagonal wurtzite structures with crystallite size of 28 - 24 nm for SW-ZnO NPs were analysed using by XRD. The prepared SW-ZnO NPs were coated with cotton fabric in pad dry cure method. The seaweed extracts and SW-ZnO NPs coated cotton fabric surface morphology and chemical compositions were confirmed by HR-SEM and EDAX. The studies on antibacterial activity of the SW-ZnO NPs coated cotton fabric showed substantial killing efficiency against gram positive and gram negative bacteria because of consistent interfacial contact between the bacterial species and SW-ZnO NPs on the cotton 12
fabric. The UV protection value of SW-ZnO NPs coated cotton fabric was found to be 43-45. Hence, from the view point of biomedical applications, the SW-ZnO NPs coated cotton fabric may be utilized as antibacterial fabrics for wound dressing application in the bacterial prone zone and UV protection application. Acknowledgements The authors would like to thank the University Grant Commission, New Delhi, for providing the financial assistance to the first author under UGC-BSR Fellowship and DST PURSE for providing funds to purchase of HR-SEM to the Department of Industrial chemistry, Alagappa University.
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22
Figure Captions Fig. 1. FT-IR spectra of (a) seaweed (b) SW-LZnO and (c) SW-HZnO.
Fig. 2. UV-Visible spectra of (a) SW-LZnO, (b) SW-HZnO and inset the seaweed.
23
Fig. 3. XRD patterns of (a) SW-LZnO and (b) SW-HZnO.
Fig. 4. N2 adsorption – desorption isotherm of the SW-HZnO. Inset the corresponding pore size distribution of SW-HZnO.
24
Fig. 5. HR-SEM images of (a) uncoated (b) seaweed extract (c) SW-LZnO and (d) SWHZnO coated cotton fabrics.
Fig. 6. EDAX spectrum of (a) uncoated (b) seaweed extract (c) SW-LZnO and (d) SWHZnOcoated cotton fabrics.
25
Fig. 7. Transmittance versus wavelength for different coated samples in UV analysis (a) uncoated (b) seaweed extract (c) SW-LZnO and (d) SW-HZnO coated cotton fabrics.
26
Table Captions Table 1 Antibacterial inhibition (mm) zone for uncoated, seaweed extract, SW-ZnO NPs coated cotton fabrics. Samples
Gram +ve
Gram -ve
S. aureus
S. pyogenes
Uncoated cotton fabric
0
0
Seaweed extract coated
5 + 0.46
SW-LZnO NPs coated SW-HZnO NPs coated
E.coli
K.aerogens
0
7 + 0.87
0
13 + 0.26
10 + 0.33
32 + 0.42 30 + 0.32
27 + 0.39
26 + 0.58
33 + 0.71 30 + 0.89
29 + 0.28
27 + 0.51
Table 2 Antibacterial activity of uncoated, seaweed and SW-ZnO NPs coated cotton fabrics by colony count method.
Bacterial cell reduction (R %) Samples
Gram +ve
Gram +ve
S. aureus
S. pyogenes
E. coli
K. aerogens
Uncoated cotton fabric
0
0
0
0
Seaweed extracts coated
69
72
70
75
SW-LZnO NPs coated
97
96
94
93
SW-HZnO NPs coated
98
97
97
95
27
Table 3 UV protection values of uncoated, seaweed extracts and SW-ZnO NPs coated cotton fabric.
Sample
UPF value
Protection value
Uncoated cotton fabric
7
Not considerable
Seaweed extracts coated cotton fabric
48
Excellent
SW-LZnO NPs coated cotton fabric
43
Good
SW-HZnO NPs coated cotton fabric
45
Very good
28
S0141-8130(17)31783-X http://dx.doi.org/doi:10.1016/j.ijbiomac.2017.07.097 BIOMAC 7905
To appear in:
International Journal of Biological Macromolecules
Received date: Revised date: Accepted date:
19-5-2017 2-7-2017 15-7-2017
Please cite this article as: R.Pandimurugan, S.Thambidurai, UV protection and antibacterial properties of seaweed capped ZnO nanoparticles coated cotton fabrics, International Journal of Biological Macromoleculeshttp://dx.doi.org/10.1016/j.ijbiomac.2017.07.097 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. 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.
UV protection and antibacterial properties of seaweed capped ZnO nanoparticles coated cotton fabrics R.Pandimurugan, S.Thambidurai*
Bio-nanomaterials Research Lab, Department of Industrial chemistry, School of Chemical Sciences, Alagappa University, Karaikudi-630003, Tamil Nadu, India.
Email: [email protected] (S.Thambidurai) Tel.: +91 4565 228836; fax: +91 4565 225202.
Research highlights
The SW-ZnO NPs were synthesized by simple chemical precipitation methods.
As synthesized nanoparticles coated with cotton fabric by pad dry cure techniques.
For comparison to seaweed extracts also coated in coated fabric
Study the antibacterial and UV protection properties of all coated cotton fabrics.
ABSTRACT Seaweed capped zinc oxide nanoparticles (SW-ZnO NPs) were prepared by simple chemical precipitation method of zinc nitrate in the presence of seaweed. The synthesised 1
SW-ZnO NPs were characterised by FT-IR, UV-Visible spectroscopy, XRD and BET analysis. These metal oxides were coated on cotton fabric using pad dry cure technique. The SW-ZnO NPs coated cotton fabrics, the surface morphology and chemical composition was analysed by HR-SEM with EDAX. The antibacterial activity of uncoated cotton, seaweed extract and SW-ZnO NPs coated cotton fabrics were investigated against Gram positive (S. aureus and S. pyogenes) and Gram negative (E. coli and K. aerogens). It showed that SW-ZnO NPs coated cotton fabric has higher antibacterial activity than other test samples against both bacteria’s. Finally, a UV-protection property of the coated cotton fabric was also tested. Keywords: Zinc oxide, Seaweed, Cotton fabric, Antibacterial activity, UV protection.
1. Introduction Cotton is one of the most abundant and widely used natural fibres in the world. Owing to its strong absorption capability, high specific surface, porous structure, bio-degradable and less cost, use of cotton has been extended from wear to technical textiles [1-3]. Despite the excellent properties of cotton fabrics, some characters like the inherently hydrophilic property, impotent antibacterial activity, low strength and poor sensitivity to the UV light, confine their wide applications, especially in some high-ends areas for medicine, personal healthcare, functional textile and self-cleaning [4-6]. Therefore, value addition to cotton by functionalization has generated considerable academic and industrial attention, not only due to their potential use in physical, thermal, biological and medical protection, but also meet the constantly evolving demand from consumers for advanced materials. Apart from the esthetical purpose of cotton, the value added cotton materials have become a basis for many industrial and technical applications [7-12].
2
Bio-nanocomposite, a new generation of bio-nanocomposite materials, signifies an emerging field in the frontier of nanotechnology, materials science, life science [13-14]. Bio nanocomposite is composed of a natural polymer matrix and organic/inorganic filler with at least one dimension on the nanometer scale. These bio-nanocomposites show the remarkable advantages of biodegradability and biocompatibility in various medical, agricultural, drug release and packaging application [15]. Seaweeds are the potential renewable resources in the marine environment. About 6000 species of seaweeds have been identified and grouped into different classes viz., green (Chlorophytes), brown (Pheophytes) and red (Rhodophytes) algae. Generally, Macro algae of seaweed have a wide range of industrial and medical applications because of having bioactive compounds such as amines, sulphates, carboxyl and hydroxyl groups [16]. Recently, the synthesis of metal oxide is based semiconductor nanoparticles using seaweed extract from various solvents has been reported. For example, synthesis of silver and gold nanoparticles by using brown seaweed extract as a reducing and stabilizing agent [17-21]. ZnO NPs is one of the various inorganic compounds, which imparts antibacterial properties to textiles [22-23]. It also regards as an excellent UV blocking property over a board range of UV wavelengths with a wide direct band gap (3.37 eV) and large excitation binding energy (60 meV) [24-25] The treatment of cotton fabrics using ZnO NPs for improved UV radiation protection has been achieved by various methods including wet chemical method [26], homogeneous precipitation methods [27], and hydrothermal method [28-29]. There is considerable interest in organic-inorganic hybrid materials. A variety of organic polymers have been introduced into organic networks to afford the hybrid materials with or without covalent bond between the polymer and inorganic components, respectively [30]. In the recent years, many researchers are interested in coated cotton fabric using different metal oxides such as TiO2 NPs [31] ZnO NPs [32-35] Au NPs [36], Ag:ZnO NPs
3
[37], SiO2 coated ZnO NPs [38] and SiO2@AgNPs [39] applied to acquire for antibacterial and UV-blocking properties. The inorganic UV blockers are more desirable than organic UV blockers due to their high efficiency at low concentration. In fact, ZnO NPs is well known of its non-toxicity as well as chemically stable under exposure to both high temperature and UV radiation. In addition, nanoparticles are significantly more effective in blocking the UV radiation more than the bulk materials, due to the fact that nanoparticles have a large surface area to volume ratio [40-41]. In this study, we prepared the seaweed capped zinc oxide nanoparticles (SW-ZnO NPs) and applied to cotton fabric by pad dry cure method for enhancing multifunctional properties of antibacterial activity and UV-protection. Furthermore, the characterization of prepared seaweed capped ZnO NPs discussed by means FT-IR, UV-Vis, XRD, BET, HRSEM and EDAX. 2. Experimental 2.1. Material The analytical grade of zinc nitrate (95% pure) and sodium hydroxide (98% pure) were purchased from Fischer Chemic Ltd, Chennai, India. For the brown seaweed of padina tetrastromatica was collected from the Gulf of Mannar, Tamil Nadu, India and washed with seawater followed by thorough washing with fresh water and under air shade. Finally, the dried samples were grind well to fine powder and stored in air tight plastic bag at room temperature. Deionized water was used in all experiment. 2.2. Preparation of seaweed capped zinc oxide nanoparticles (SW-ZnO NPs) The method of preparation of SW-ZnO NPs can be found in our recent paper [42]. Briefly, 12.5 g of zinc nitrate was dissolved in 100 ml distilled water to obtain a 12.5 % of zinc salt solution and 0.5 g of dried seaweed powder was poured into the solution and then 4
the mixture was stirred for 2 h at 80oC to assist the electrostatic attraction of Zn2+ onto the seaweed. After cooling the mixture at room temperature, 25% of fresh sodium hydroxide was drop wise added to the above mixture and left to react for 24 hours. The supernatant clear solution was drained and remaining was washed with distilled water for several times. Finally, the precipitate was filtered using suction pump and dried in hot air oven at 120 oC for 4 h. The sample was designated as SW-LZnO. The above process was followed by the increasing of zinc nitrate concentration from 12.5 % to 25 % and designates as SW-HZnO. 2.3. Coating of SW-ZnO NPs on cotton fabrics About 0.5 g of SW-LZnO NPs was dissolved in 20 ml of PVA and stirred for 1 h with magnetic stirrer at room temperature. The mixture was sonicated for 30 min improve the dispersion of SW-LZnO NPs particles in the solution. About 4 g of bioscoured cotton fabric was immersed in the SW-LZnO NPs into PVA solution for 30 min and padded in the padding mangle, squeezed between two squeezing rollers for 80% wet pick-up. The padded fabric was dried in an oven at 70oC for 10 min and cured in an oven at 150oC for 5 min [43]. The cured fabric was washed well with 1% sodium hydroxide solution, neutralised with 1% acetic acid, washed again and air-dried. The above process was repeated by replacing SW-LZnO with SW-HZnO and seaweed extracts. 2.4. Characterizations FT-IR spectra were recorded for seaweed capped zinc oxide nanoparticles using FTIR, SHIMADZU. Samples (0.02 g) were mixed with potassium bromide (KBr) and IR spectra were scanned over wave number range of 4000-400 cm-1. The optical absorption spectra of all the samples were obtained by use of a JASCO UV-Vis NIR (V-670) in the wavelength range of 200 - 800 nm. X-ray diffraction (XRD) studies were carried out in a 2θ range of 10– 80o using an X-ray diffractometer ((X'Pert PRO diffractometer) with Cu Kα radiation 5
(λ = 0.15406 nm). Nitrogen adsorption-desorption isotherms were performed with an ASAP 2020 Micromeritics analyzer at 77 K. The specific surface areas were determined by Brunauer – Emmett – Teller (BET) method. The pore size distribution was calculated according to the Berrett-Joyner-Halenda (BJH) method. The surface morphology of ZnO NPs treated cotton fabric samples were observed using FEI quanta FEG 250 instrument operated in an accelerating voltage at 10 kV. The elemental analysis of ZnO NPs treated cotton fabric was performed using EDAX, which is an attachment to the HR-SEM. 2.5. Antibacterial test The antibacterial activities of pure cotton, seaweed extracts and SW-ZnO NPs coated cotton fabrics were investigated by two techniques viz. agar diffusion method and reduction of colony forming units (CFU) of two strains of gram positive microorganism, staphylococcus (S. aureus), streptococcus pyogenes (S. pyogenes) and two strains of gram negative microorganism Escherichia coli (E. coli), Klbesiella aerogenes (K. aeroenes) [44]. For qualitative measurements, the samples were put together to form a circular zone, and the antimicrobial activity was tested using modified agar diffusion assay. The plates were kept at 37oC overnight incubation. After incubation, inhibition zone was measured with zone measurement scale. The diameter of the zone of inhibition was then examined directly underneath and around the sample. The inhibition cleared a zone in and around the sample determined the efficiency of the antibacterial agent to inhibit the growth of bacteria. The uncoated cotton fabric was used as blank or negative control and the standard antibiotic Amikacin used as positive control. All the experiment was conducted in triplicate under the same set of conditions. The study of the cell reduction activity of coated samples was performed using the colony count method. One gram of fabric was cut into small pieces and added with approximate volume of 106 CFU/ml of the gram positive and gram negative bacteria in 6
Muller-Hinton broth and incubated at 37oC on shaking platform at 250 rpm for 24 h. Control broth with untreated cotton fabric was also used. The antibacterial activity was expressed in terms of the percent reduction of the organism after contact with the test specimen compared to the number of bacterial cells surviving after contact with the control. The percentage of CFU was calculated by the following equation
Reduction in CFU (%) =
CA C
x 100%
--------- (1)
Where, C and A are the bacterial colonies of the untreated and the treated cotton fabrics respectively.
3. Result and Discussions 3.1. FT-IR Spectroscopy FT-IR analysis was used to study the interaction between the nano ZnO and seaweed. Fig. 1a-c demonstrates FT-IR spectra of seaweed, SW-LZnO and SW-HZnO. The characteristic peaks of seaweed (Fig.1 a) due to cellulosic macromolecule appear at 3409 cm1
(O-H stretching), 2921 cm-1 (C-H stretching), 1429 cm-1 (C-H wagging), 1369 cm-1 (C-H
bending) and 1032 cm-1 (C-O stretching) [45]. The peaks at 670 and 601 cm-1 were attributed to asymmetric and symmetric O=S=O deformation of a sulphate group [46-49]. Fig. 1a-b show FT-IR spectra of synthesized SW-ZnO NPs indicates a broad peak at 3355 cm-1 related to O-H vibration. The strong symmetric stretching C=O and C-O presented at 1508 and 1386 cm-1 respectively. The peak at 1042 cm-1 relates to C-O-C groups. The presence of C=O, C-O and C-O-C in FT-IR spectra could be due to zinc salt precursor [50]. The ZnO peak also appeared at 426 cm-1 related to Zn-O bonds [51]. Seaweed consists of two major bioactive compounds such as β-D-mannuronic and α-L-guluronic acids which have the functional 7
groups of -COO- and -OH sites. These groups may bind the zinc ions present in the reaction mixture and can stabilize nanoparticles from formation of agglomeration [42]. 3.2. UV-Visible Spectroscopy Fig. 2a-b shows the UV–Vis absorbance of SW-ZnO NPs with different levels of concentration of zinc precursors. An absorption peak appeared at 366 and 370 nm for SWLZnO and SW-HZnO, respectively, while the peak in the bulk ZnO appeared at 372 nm. The absorption peak of seaweed extract capped ZnO NPs exhibited an obvious blue-shift phenomenon due to the quantum confinement effect. The UV absorbance and intensity of the peak varied ZnO NPs from the concentration of zinc nitrate, which is commonly attributed to charge transfer from the valence to a conduction band of nanostructures or particles that have wide particle size distribution [52-53]. The band gap energies of all samples were calculated using the following equation (ahv)2 ED (hv Eg) (2)
where α is the optical absorption coefficient, hν is the photon energy, Eg is the direct band gap and ED is the constant. The extrapolation of the linear portion of the graph (αhν) 2 versus hν when extrapolating to the zero is a direct band gap (Eg) value. The calculated band gap energy was 3.2 and 3.16 eV for SW-LZnO and SW-HZnO samples respectively. The insert Fig. 2 show the absorption spectrum of seaweed extracts in methanol solvents show the three absorption peak at 328, 408 and 667 nm which are characteristics of the seaweed [54]. 3.3. X-ray diffraction analysis Fig. 3a-b shows the XRD patterns of SW-ZnO NPs of SW-LZnO and SW-HZnO. It can be seen from the figure that the XRD pattern could be assigned to hexagonal ZnO, which is in good agreement with that of the standard card JCPDS card #36-1451. These peaks are presented in the SW-ZnO NPs are almost similar to those of the pure ZnO and no peaks
8
assigned to seaweed were observed. This might to be content of seaweed layer was too small to be determined [55]. The particle sizes that are calculated from Debye-Schere’s equation (D = 0.94 λ/β cos θ) are 28 and 24 nm for SW-LZnO and SW-HZnO, respectively. Which is mainly depends on the zinc ion concentration is varied from the zinc nitrate. 3.4. BET analysis The porous feature of the SW-ZnO NPs was characterized by BET analysis. Fig. 4 present the nitrogen adsorption-desorption isotherms and BJH pore size distribution curves of SW-ZnO NPs. According to the IUPAC classification [56], the loop observed would be ascribed as type H3 hysteresis loops, indicating the existence of abundant pores. The average pore diameter is around 33.541 nm and the BET surface area of the material is 28.2836 m2/g. The single crystalline phase and porous nature of the SW-ZnO NPs makes it a promising candidate for environment treatment.
3.5. Surface morphology and elemental analysis coated of cotton fabric The surface morphology of the uncoated, seaweed extract and SW-ZnO NPs treated cotton fabric was investigated by HR-SEM and illustrated in Fig.5a-d It was observed from the HR-SEM image of the uncoated cotton fabric (Fig. 5a), grooves and fibrils could be easily observed on the surface of the fibre. While the surface morphology of the treated cotton fabrics were covered with seaweed extract as shown in Fig. 5b. It was also detected with SW-ZnO NPs were well dispersed on surface of the treated fabrics samples (Fig. 5c and d), however, there is some of ZnO NPs aggregated and form large particles will be easily removed from the fibre surface with washing due to the physical adsorption of these particles
9
to the outer surface cotton fabrics, on the contrary, the smaller nanoparticles will easily enter deeper and adhere strongly into the pores of fabrics. Chemical composition of uncoated cotton, seaweed extract and SW-ZnO NPs coated cotton fabric obtained by EDAX spectrum are shown in Fig. 6. The uncoated cotton fabric is shown in (Fig. 6a) only for carbon and oxygen element. In Fig 6b show the seaweed content elements such as aluminium, silica, sulphur, silver, calcium, titanium and nickel. Seaweed is a natural polymer that contains polysaccharide and some inorganic elements. A number of studies [57-59] have reported the existence of metals, the relative proportions and the association of the inorganic elements are largely dependent on the cultivation environment and harvesting history. These elements are improving the properties of cotton fabrics. SWZnO NPs coated cotton fabric confirm the presence of Zn, O, and C elements related to cellulose, and nano ZnO (Fig. 6c). It is then proved that the seaweed extracts and SW-ZnO NPs are coated on cotton fabric surfaces.
3.6. Antibacterial activity of SW-ZnO NPs coated cotton fabric The antibacterial property of cotton fabrics were reported as a mean value of the inhibition zone in Table 2. It was calculated according to the following equation:
W=
T D 2
-----------
(3)
Where W is the width of the inhibition zone in mm, and T is the total diameter of test specimens and clear zone, and D is the diameter of the test specimen. It was not seen any inhibition zone surround of uncoated cotton fabric against two types of bacteria. However, 10
the seaweed extracts and SW-ZnO NPs coated cotton fabric presented a clear inhibition zone, and its width was larger against Gram-positive type bacteria compared to Gram-negative type bacteria (Table 1). The greater sensitivity of Gram-positive compared to Gram-negatives bacteria to ZnO nanoparticles is probably due to their difference in the cell membrane structure. The cell membrane of the Gram-negative bacteria composes of lipids, proteins and lipopolysaccharides and cannot provide effective protection [60]. The antibacterial properties of ZnO nanoparticles can be due to reactive oxygen species, probable production of free radicals, and metal ions release [61]. Moreover, it was reported that the antibacterial activity of ZnO nanoparticles depends on the morphology [62]. The SW-HZnO NPs coated cotton fabric presented a large inhibition zone width compared to SW-LZnO NPs coated cotton fabric, because the high concentration of zinc content increase the antibacterial activity. 3.6.1. Colony forming unit The antibacterial activity of SW-ZnO NPs treated cotton before and after washing against gram positive and gram negative bacterial are displayed in Table 2. It was found that the SW-ZnO NPs treated cotton fabrics has more efficient against bacteria while the bacterial reduction of untreated cotton fabric is zero but the SW-ZnO NPs treated cotton fabric reached sufficient value (96.3%) when the cotton fabrics treated with the lowest concentration of zinc nitrate solution. It is also found that the bacterial reduction of cotton fabrics increases marginally with increasing zinc oxide nanoparticles. The particular mechanism of the antibacterial activity of ZnO is still a matter of dispute. Some researchers consider that it might be a consequence of the generation of hydrogen peroxide (H2O2) on its surface [63]. Parallel results were observed against E.coli with insignificant reduction. 3.7. UV blocking studies
11
Fig. 7a-d shows the UV transmittance and UV blocking properties of uncoated, seaweed extracts and SW-ZnO NPs coated cotton fabric samples in the range of 200-400 nm. The curve (a) is the UV transmittance curve of the uncoated cotton fabric, demonstrating that almost 49 % of the UV light can penetrate into the uncoated cotton fabric. In curve (b) seaweed extracts coated samples, the transmittance values decreases, which confirm the presence of UV blocking material of seaweed extracts are coated in cotton fabric. UV blocking properties of the SW-ZnO NPs coated cotton fabrics (curve c and d) were compared. Absorption of ZnO blow its band gap, especially at UV (358 -400 nm) portion that can generate highly reactive chemical intermediates, such as hydroxyl and oxygen radicals [64]. It shows that at high concentration SW-ZnO NPs decrease in the value of transmittance compared to lower concentration of SW-ZnO NPs coated cotton fabric and the values are shown in Table 3. UV-blocking results revealed that when the ratio of ZnO increases, the UV blocking efficiency is also increases. 4. Conclusions SW-ZnO NPs were prepared by simple chemical precipitation method in two level of concentration of zinc nitrate such as lower 12.5% and higher 25% are used. FTIR spectra revealed that the chemical interaction between the seaweed and ZnO nanoparticles and confirm the attachment seaweed moieties to ZnO due to the formation of a seaweed-zinc ion network. The hexagonal wurtzite structures with crystallite size of 28 - 24 nm for SW-ZnO NPs were analysed using by XRD. The prepared SW-ZnO NPs were coated with cotton fabric in pad dry cure method. The seaweed extracts and SW-ZnO NPs coated cotton fabric surface morphology and chemical compositions were confirmed by HR-SEM and EDAX. The studies on antibacterial activity of the SW-ZnO NPs coated cotton fabric showed substantial killing efficiency against gram positive and gram negative bacteria because of consistent interfacial contact between the bacterial species and SW-ZnO NPs on the cotton 12
fabric. The UV protection value of SW-ZnO NPs coated cotton fabric was found to be 43-45. Hence, from the view point of biomedical applications, the SW-ZnO NPs coated cotton fabric may be utilized as antibacterial fabrics for wound dressing application in the bacterial prone zone and UV protection application. Acknowledgements The authors would like to thank the University Grant Commission, New Delhi, for providing the financial assistance to the first author under UGC-BSR Fellowship and DST PURSE for providing funds to purchase of HR-SEM to the Department of Industrial chemistry, Alagappa University.
13
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Figure Captions Fig. 1. FT-IR spectra of (a) seaweed (b) SW-LZnO and (c) SW-HZnO.
Fig. 2. UV-Visible spectra of (a) SW-LZnO, (b) SW-HZnO and inset the seaweed.
23
Fig. 3. XRD patterns of (a) SW-LZnO and (b) SW-HZnO.
Fig. 4. N2 adsorption – desorption isotherm of the SW-HZnO. Inset the corresponding pore size distribution of SW-HZnO.
24
Fig. 5. HR-SEM images of (a) uncoated (b) seaweed extract (c) SW-LZnO and (d) SWHZnO coated cotton fabrics.
Fig. 6. EDAX spectrum of (a) uncoated (b) seaweed extract (c) SW-LZnO and (d) SWHZnOcoated cotton fabrics.
25
Fig. 7. Transmittance versus wavelength for different coated samples in UV analysis (a) uncoated (b) seaweed extract (c) SW-LZnO and (d) SW-HZnO coated cotton fabrics.
26
Table Captions Table 1 Antibacterial inhibition (mm) zone for uncoated, seaweed extract, SW-ZnO NPs coated cotton fabrics. Samples
Gram +ve
Gram -ve
S. aureus
S. pyogenes
Uncoated cotton fabric
0
0
Seaweed extract coated
5 + 0.46
SW-LZnO NPs coated SW-HZnO NPs coated
E.coli
K.aerogens
0
7 + 0.87
0
13 + 0.26
10 + 0.33
32 + 0.42 30 + 0.32
27 + 0.39
26 + 0.58
33 + 0.71 30 + 0.89
29 + 0.28
27 + 0.51
Table 2 Antibacterial activity of uncoated, seaweed and SW-ZnO NPs coated cotton fabrics by colony count method.
Bacterial cell reduction (R %) Samples
Gram +ve
Gram +ve
S. aureus
S. pyogenes
E. coli
K. aerogens
Uncoated cotton fabric
0
0
0
0
Seaweed extracts coated
69
72
70
75
SW-LZnO NPs coated
97
96
94
93
SW-HZnO NPs coated
98
97
97
95
27
Table 3 UV protection values of uncoated, seaweed extracts and SW-ZnO NPs coated cotton fabric.
Sample
UPF value
Protection value
Uncoated cotton fabric
7
Not considerable
Seaweed extracts coated cotton fabric
48
Excellent
SW-LZnO NPs coated cotton fabric
43
Good
SW-HZnO NPs coated cotton fabric
45
Very good
28