- Email: [email protected]
poly(L -lactic acid) nanofibers scaffold
Materials Letters 171 (2016) 178–181
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Cell adhesion behavior of poly(ε-caprolactone)/poly(L-lactic acid) nanofibers scaffold Zeeshan Khatri a,b,n, Abdul Wahab Jatoi a,b, Farooq Ahmed a, Ick-Soo Kim b,nn a
Nanomaterial Research Lab, Department of Textile Engineering, Mehran University of Engineering and Technology, Jamshoro 76060, Pakistan Nano Fusion Technology Research Group, Division of Frontier Fibers, Institute for Fiber Engineering (IFES), Interdisciplinary Cluster for Cutting Edge Research (ICCER), Shinshu University, Tokida 3-15-1, Ueda, Nagano Prefecture 386-8567, Japan
b
art ic l e i nf o
a b s t r a c t
Article history: Received 14 December 2015 Received in revised form 10 February 2016 Accepted 13 February 2016 Available online 17 February 2016
Biodegradable nanofiberous tubes are being investigated and developed for nerve tissue regeneration. The poly (ε-caprolactone) and poly (L-lactic acid) offer competitive candidacy due to higher stability by former and better biodegradability of the latter. Exploiting these characteristics of both the polymers, we present our study on generation of nanofiber tubes from pure PCL, pure PLLA and their blends (PCL/ PLLA). The nanofibers were electrospun and collected on 2 cm diameter rotating collector. The samples were analyzed for cell adhesion, tensile strength, homogeneity, chemical analysis by FTIR. The results show comparatively enhanced cell adhesion in PLLA samples and blends with higher PLLA proportion. Contrary, samples with higher PCL proportion depicted better tensile strength. FTIR results demonstrated PCL and PLLA characteristic peaks in their blends. The results confirm suitability of PCL/PLLA nanofiberous tubes for nerve tissue regeneration and tissue growth. & 2016 Elsevier B.V. All rights reserved.
Keywords: Biomaterials Fiber technology Poly (ε-caprolactone) Poly(L-Lactic acid) Cell attachment Nanofibers tube
1. Introductıon Biodegradability of the polymers is a well desired characteristic for fabrication of nerve tissue regeneration scaffolds [1,2] offering advantage of elimination of post operative surgery necessary for removal of the conduits in case of non-biodegradable materials [3]. However, selection of a suitable polymer or polymer blend is a fundamental consideration for success of the implant. The commonly used polymers used so for tissue regeneration applications are PCL [4,5], PLLA [6,7], PLGA [8], PLCL [9], PLLA-PDLA [10], PLGAPCL [3], SF [11] and P(LLA-CL) [12]. Synthesis of implants composed of polymer blends offers a suitable choice to obtain tailored properties and improved performances in terms of physical and biological characteristics [13]. PCL in general offers mechanical strength to the structure, higher permeability and suitable cell adherence characteristics [14,15]. However, the PLLA on the other hand endow exceptional biodegradation [16] and has been referred for faster biodegradation n
Corresponding author at: Nanomaterial Research Lab, Department of Textile Engineering, Mehran University of Engineering and Technology, Jamshoro 76060, Pakistan. nn Correspondence to: Nano Fusion Technology Research Group, Shinshu University, 3-15-1, Tokida, Ueda City, Nagano 386-8567, Japan. E-mail addresses: [email protected] (Z. Khatri), [email protected] (I.-S. Kim). http://dx.doi.org/10.1016/j.matlet.2016.02.061 0167-577X/& 2016 Elsevier B.V. All rights reserved.
but slow permeation potential [17]. To exploit these differing characteristics of both these polymers we attempted to carry out comparative analysis of these polymers and fabricated their electrospun nanofibers in order to investigate their combined cell culture potential and mechanical stability of the nanofibers. The PCL, PLLA and their three blends were electrospun in to tubular form in order to simulate nerve conduit by collecting the nanofibers on 2 cm diameter collector. The nano-fibrous structure of the polymer conduits offers higher surface area and porous structure for cell adherence and growth [18]. The results exhibited substantial cell growth on the samples hence confirmation of suitability of the nanofiber conduits for nerve tissue regeneration.
2. Materials and methods 2.1. Materials Poly(ε-caprolactone) (PCL: Mw 80,000), poly(L-Lactic Acid) (PLLA: Mw 143,000), DMF, chloroform and acetone were purchased from Sigma Aldrich, Japan. PCL solution 12% (w/w) was prepared using DMF: chloroform (1:9) while PLLA 8% (w/w) using chloroform: acetone (3:1) solvents. Five formulations such as pure PCL and PLLA, PCL/PLLA 1:1, PCL/PLLA 1:2 and PCL/PLLA 2:1 were prepared and stirred for 24 h at 50 °C prior to electrospinning.
Z. Khatri et al. / Materials Letters 171 (2016) 178–181
179
Fig. 1. FTIR spectrum of (a) PCL (b) PCL/PLLA 2:1 (c) PCL/PLLA 1:1 (d) PCL/PLLA 1:2 (e) PLLA.
Fig. 2. TEM images (a) Tensile strength of the nanofibers (b).
2.2. Method
2.4. Cell culture
Electrospinning spinning apparatus (Har-100*12, Matsusada Co., Tokyo, Japan) was used for nanofiber formation. The nanofibers were collected on 2 cm rotating collector. Needle tip to collector distance was maintained 12 cm and 12 kV voltage was supplied.
The murine fibroblast L929 cells (2104 cells/well) were utilized for L929 in-vitro growth test. Fibrous RSF and RSF/TMOS electrospun-fibers were treated with CH3OH (50%) at room temperature for 60 min followed by vacuum drying for 24 h prior to utilization. Tissue culture dishes (TCDs) were incubated at 37 °C (5% CO2 in atmosphere) using Eagle's MEM supplemented by FBS (5%), penicillin/streptomycin (105U and 0.1 g L1MEM respectively) and 2 mM L-glutamine.
2.3. Characterization All the samples were characterized for morphology by scanning electron microscope (SEM, S-3000N by Hitachi, Japan) and transmission electron microscopy (JEOL model 2010 Fas TEM). Chemical analysis of the samples was conducted using Fourier transform infrared spectroscopy (FTIR, IR Prestige-21, Shimatzu, Japan). Testing of the mechanical property of the nonwoven nanofibers was performed according to ASTM D-638 using a universal testing machine (Tensilon RTC1250A; A&D Company Ltd, Japan). The crosshead speed was set at 5.0 mm/min.
3. Results and discussion 3.1. FTIR analysis The FTIR results of PCL, PLLA and PCL/PLLA blends are described in Fig. 1. The PCL spectrum (Fig. 1a) depicts characteristic peaks of carbonyl stretching (CO) at 1722 cm 1, COC stretching (asymm.) at 1238 cm 1, COC stretching (symm.) at 1164 cm 1, CH2 stretching
180
Z. Khatri et al. / Materials Letters 171 (2016) 178–181
Fig. 3. SEM images showing cell adhesion behavior of (a1) PCL for 1 h cs (a2) PCL for 6 h cs (a3) PCL for 6 h cs ; (b1) PCL/PLLA 2:1 for 1 h cs (b11) PCL/PLLA 2:1 for 6 h cs (b111) PCL/PLLA 2:1 for 24 h cs ; (c1) PCL/PLLA 1:1 for 1 h cs (c11) PCL/PLLA 1:1 for 6 h cs (c111) PCL/PLLA 1:1 for 24 h cs; (d1) PCL/PLLA 1:2 for 1 h cs (d11) PCL/PLLA 1:2 for 6 h cs (d111) PCL/PLLA 1:2 for 24 h cs; (e1) PLLA 1 h cs (e11) PLLA for 6 h cs (e111) PLLA for 24 h cs ; (f1) TCD 1 h cs (f11) TCD for 6 h cs (f111) TCD for 24 h cs (cs, cell seeding; TCD, tissue culture dish).
Z. Khatri et al. / Materials Letters 171 (2016) 178–181
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adhesion on PLLA samples and those with higher proportion of PLLA (Fig. 4e and f) and lower in pure PCL samples. For analysis on cs, the cell adhesion was observed to substantially increase almost all the samples; particularly 24cs demonstrated higher growth.
4. Conclusion
Fig. 4. Cell adhesion rate for (a) TCD (b) PCL (c) PCL/PLLA 2:1 (d) PCL/PLLA 1:1 (e) PCL/PLLA 1:2 (f) PLLA.
(asymm.) at 2945 cm 1 and CH2 stretching (symm.) at 2865 cm 1 . The PLLA spectrum (Fig. 1e) shows characteristic peaks of carbonyl stretching (CO) at 1750 cm 1, CH2 bending 1452 cm 1, CH2 deformation (symm.) at 1382 cm 1, 1267 cm 1, 1180 cm 1 and 1082 cm 1 ether (COC) stretching. The corresponding peaks of PCL/ PLLA blends (Fig. 1b–d) represent related peaks of both the PCL and PLLA with respective to proportion of each polymer, justifying homogeneity in the blends.
The PCL, PLLA and PCL/PLLA electrospun tubular scaffolds were successfully prepared and characterized for cell culture. The phase homogeneity (no phase separation) of the blends was confirmed by TEM images. The cell adhesion, tensile strength and morphological studies conclude success of all the scaffolds for tissue regeneration owing to substantial cell adhesion. Blends with higher proportion of PLLA show higher cell adhesion while those with enhanced PCL demonstrated better mechanical strength.
Acknowledgements This work was supported by Grants for Excellent Graduate Schools, MEXT, Japan.
References
3.2. TEM analysis The TEM results for all the three PCL/PLLA blends shown in Fig. 2a were determined in order to observe phase separation analysis. The results reported show homogeneous blends without any phase separation. 3.3. Mechanical properties In order to evaluate the structural and mechanical strength of the nanofiberous tube, tensile strength tests were conducted and results are reported in Fig. 2b. The analysis of the figure shows higher tensile strength for PCL and the scaffolds with higher PCL contents. This is no doubt due to higher mechanical stability of the PCL nanofibers. The PLLA nanofibers due to their lower mechanical stability exhibit low tensile strength. The tensile strengths of blends are observed to remain in between PCL and PLLA. 3.4. Cell adhesion Cell adhesion tests were conducted for 1 h, 6 h and 24 h in order to determine fibroblast L929 cell's growth on PCL, PCL/PLLA blends, PLLA and TCDs. The SEM images given in Fig. 3 depict cell adhesion on respective nanofibers for mentioned times. The result show higher cell adhesion on the PLLA nanofibers (Fig. 3e) and the composites with its higher proportion (Fig. 3d). The PCL/PLLA 1:1 blend (Fig. 3c) can also be observed to possess enhanced cell adhesion in comparison to pure PCL nanofibers (Fig. 3a). The cell adhesion and growth was observed to increase with cell seeding (cs) time. For example for 24 h cs, higher number of cells can be observed along with their growth in size. The cell adhesion and proliferation is also observed on the TCD with substantial growth for 24 h cs.The number of cell adhered during the experiment on the samples were counted and the results are reported in terms of cell adhesion % in Fig. 4. The results show comparatively larger cell
[1] M.P. Prabhakaran, L. Ghasemi-Mobarakeh, S. Ramakrishna, Electrospun composite nanofibers for tissue regeneration, J. Nanosci. Nanotechnol. 11 (4) (2011) 3039–3057. [2] B.D. Ulery, L.S. Nair, C.T. Laurencin, Biomedical applications of biodegradable polymers, J. Polym. Sci. B: Polym. Phys. 49 (12) (2011) 832–864. [3] S. Panseri, et al., Electrospun micro-and nanofiber tubes for functional nervous regeneration in sciatic nerve transections, BMC Biotechnol. 8 (1) (2008) 39. [4] S.H. Ku, C.B. Park, Human endothelial cell growth on mussel-inspired nanofiber scaffold for vascular tissue engineering, Biomaterials 31 (36) (2010) 9431–9437. [5] S.J. Lee, et al., The use of thermal treatments to enhance the mechanical properties of electrospun poly (ɛ-caprolactone) scaffolds, Biomaterials 29 (10) (2008) 1422–1430. [6] F. Yang, et al., Fabrication of nano-structured porous PLLA scaffold intended for nerve tissue engineering, Biomaterials 25 (10) (2004) 1891–1900. [7] S. Patra, A. Easteal, D. Bhattacharyya, Parametric study of manufacturing poly (lactic) acid nanofibrous mat by electrospinning, J. Mater. Sci. 44 (2) (2009) 647–654. [8] T. Bini, et al., Poly (l-lactide-co-glycolide) biodegradable microfibers and electrospun nanofibers for nerve tissue engineering: an in vitro study, J. Mater. Sci. 41 (19) (2006) 6453–6459. [9] L. Tian, et al., Emulsion electrospun vascular endothelial growth factor encapsulated poly (l-lactic acid-co-ε-caprolactone) nanofibers for sustained release in cardiac tissue engineering, J. Mater. Sci. 47 (7) (2012) 3272–3281. [10] X. Zong, et al., Structure and process relationship of electrospun bioabsorbable nanofiber membranes, Polymer 43 (16) (2002) 4403–4412. [11] B. Marelli, et al., Compliant electrospun silk fibroin tubes for small vessel bypass grafting, Acta Biomater. 6 (10) (2010) 4019–4026. [12] C. Xu, et al., Aligned biodegradable nanofibrous structure: a potential scaffold for blood vessel engineering, Biomaterials 25 (5) (2004) 877–886. [13] F.C. Pavia, V. La Carrubba, V. Brucato, Tuning of biodegradation rate of PLLA scaffolds via blending with PLA, Int. J. Mater. Form. 2 (1) (2009) 713–716. [14] S.J. Hollister, Porous scaffold design for tissue engineering, Nat. Mater. 4 (7) (2005) 518–524. [15] R.A. Gross, B. Kalra, Biodegradable polymers for the environment, Science 297 (5582) (2002) 803–807. [16] J. Zeng, et al., Enzymatic degradation of poly (l‐lactide) and poly (ε‐caprolactone) electrospun fibers, Macromol. Biosci. 4 (12) (2004) 1118–1125. [17] K. Kim, et al., Control of degradation rate and hydrophilicity in electrospun non-woven poly (D, L-lactide) nanofiber scaffolds for biomedical applications, Biomaterials 24 (27) (2003) 4977–4985. [18] Z. Khatri, et al., Preparation and characterization of electrospun poly (ε-caprolactone)-poly (l-lactic acid) nanofiber tubes, J. Mater. Sci. 48 (10) (2013) 3659–3664.
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Cell adhesion behavior of poly(ε-caprolactone)/poly(L-lactic acid) nanofibers scaffold Zeeshan Khatri a,b,n, Abdul Wahab Jatoi a,b, Farooq Ahmed a, Ick-Soo Kim b,nn a
Nanomaterial Research Lab, Department of Textile Engineering, Mehran University of Engineering and Technology, Jamshoro 76060, Pakistan Nano Fusion Technology Research Group, Division of Frontier Fibers, Institute for Fiber Engineering (IFES), Interdisciplinary Cluster for Cutting Edge Research (ICCER), Shinshu University, Tokida 3-15-1, Ueda, Nagano Prefecture 386-8567, Japan
b
art ic l e i nf o
a b s t r a c t
Article history: Received 14 December 2015 Received in revised form 10 February 2016 Accepted 13 February 2016 Available online 17 February 2016
Biodegradable nanofiberous tubes are being investigated and developed for nerve tissue regeneration. The poly (ε-caprolactone) and poly (L-lactic acid) offer competitive candidacy due to higher stability by former and better biodegradability of the latter. Exploiting these characteristics of both the polymers, we present our study on generation of nanofiber tubes from pure PCL, pure PLLA and their blends (PCL/ PLLA). The nanofibers were electrospun and collected on 2 cm diameter rotating collector. The samples were analyzed for cell adhesion, tensile strength, homogeneity, chemical analysis by FTIR. The results show comparatively enhanced cell adhesion in PLLA samples and blends with higher PLLA proportion. Contrary, samples with higher PCL proportion depicted better tensile strength. FTIR results demonstrated PCL and PLLA characteristic peaks in their blends. The results confirm suitability of PCL/PLLA nanofiberous tubes for nerve tissue regeneration and tissue growth. & 2016 Elsevier B.V. All rights reserved.
Keywords: Biomaterials Fiber technology Poly (ε-caprolactone) Poly(L-Lactic acid) Cell attachment Nanofibers tube
1. Introductıon Biodegradability of the polymers is a well desired characteristic for fabrication of nerve tissue regeneration scaffolds [1,2] offering advantage of elimination of post operative surgery necessary for removal of the conduits in case of non-biodegradable materials [3]. However, selection of a suitable polymer or polymer blend is a fundamental consideration for success of the implant. The commonly used polymers used so for tissue regeneration applications are PCL [4,5], PLLA [6,7], PLGA [8], PLCL [9], PLLA-PDLA [10], PLGAPCL [3], SF [11] and P(LLA-CL) [12]. Synthesis of implants composed of polymer blends offers a suitable choice to obtain tailored properties and improved performances in terms of physical and biological characteristics [13]. PCL in general offers mechanical strength to the structure, higher permeability and suitable cell adherence characteristics [14,15]. However, the PLLA on the other hand endow exceptional biodegradation [16] and has been referred for faster biodegradation n
Corresponding author at: Nanomaterial Research Lab, Department of Textile Engineering, Mehran University of Engineering and Technology, Jamshoro 76060, Pakistan. nn Correspondence to: Nano Fusion Technology Research Group, Shinshu University, 3-15-1, Tokida, Ueda City, Nagano 386-8567, Japan. E-mail addresses: [email protected] (Z. Khatri), [email protected] (I.-S. Kim). http://dx.doi.org/10.1016/j.matlet.2016.02.061 0167-577X/& 2016 Elsevier B.V. All rights reserved.
but slow permeation potential [17]. To exploit these differing characteristics of both these polymers we attempted to carry out comparative analysis of these polymers and fabricated their electrospun nanofibers in order to investigate their combined cell culture potential and mechanical stability of the nanofibers. The PCL, PLLA and their three blends were electrospun in to tubular form in order to simulate nerve conduit by collecting the nanofibers on 2 cm diameter collector. The nano-fibrous structure of the polymer conduits offers higher surface area and porous structure for cell adherence and growth [18]. The results exhibited substantial cell growth on the samples hence confirmation of suitability of the nanofiber conduits for nerve tissue regeneration.
2. Materials and methods 2.1. Materials Poly(ε-caprolactone) (PCL: Mw 80,000), poly(L-Lactic Acid) (PLLA: Mw 143,000), DMF, chloroform and acetone were purchased from Sigma Aldrich, Japan. PCL solution 12% (w/w) was prepared using DMF: chloroform (1:9) while PLLA 8% (w/w) using chloroform: acetone (3:1) solvents. Five formulations such as pure PCL and PLLA, PCL/PLLA 1:1, PCL/PLLA 1:2 and PCL/PLLA 2:1 were prepared and stirred for 24 h at 50 °C prior to electrospinning.
Z. Khatri et al. / Materials Letters 171 (2016) 178–181
179
Fig. 1. FTIR spectrum of (a) PCL (b) PCL/PLLA 2:1 (c) PCL/PLLA 1:1 (d) PCL/PLLA 1:2 (e) PLLA.
Fig. 2. TEM images (a) Tensile strength of the nanofibers (b).
2.2. Method
2.4. Cell culture
Electrospinning spinning apparatus (Har-100*12, Matsusada Co., Tokyo, Japan) was used for nanofiber formation. The nanofibers were collected on 2 cm rotating collector. Needle tip to collector distance was maintained 12 cm and 12 kV voltage was supplied.
The murine fibroblast L929 cells (2104 cells/well) were utilized for L929 in-vitro growth test. Fibrous RSF and RSF/TMOS electrospun-fibers were treated with CH3OH (50%) at room temperature for 60 min followed by vacuum drying for 24 h prior to utilization. Tissue culture dishes (TCDs) were incubated at 37 °C (5% CO2 in atmosphere) using Eagle's MEM supplemented by FBS (5%), penicillin/streptomycin (105U and 0.1 g L1MEM respectively) and 2 mM L-glutamine.
2.3. Characterization All the samples were characterized for morphology by scanning electron microscope (SEM, S-3000N by Hitachi, Japan) and transmission electron microscopy (JEOL model 2010 Fas TEM). Chemical analysis of the samples was conducted using Fourier transform infrared spectroscopy (FTIR, IR Prestige-21, Shimatzu, Japan). Testing of the mechanical property of the nonwoven nanofibers was performed according to ASTM D-638 using a universal testing machine (Tensilon RTC1250A; A&D Company Ltd, Japan). The crosshead speed was set at 5.0 mm/min.
3. Results and discussion 3.1. FTIR analysis The FTIR results of PCL, PLLA and PCL/PLLA blends are described in Fig. 1. The PCL spectrum (Fig. 1a) depicts characteristic peaks of carbonyl stretching (CO) at 1722 cm 1, COC stretching (asymm.) at 1238 cm 1, COC stretching (symm.) at 1164 cm 1, CH2 stretching
180
Z. Khatri et al. / Materials Letters 171 (2016) 178–181
Fig. 3. SEM images showing cell adhesion behavior of (a1) PCL for 1 h cs (a2) PCL for 6 h cs (a3) PCL for 6 h cs ; (b1) PCL/PLLA 2:1 for 1 h cs (b11) PCL/PLLA 2:1 for 6 h cs (b111) PCL/PLLA 2:1 for 24 h cs ; (c1) PCL/PLLA 1:1 for 1 h cs (c11) PCL/PLLA 1:1 for 6 h cs (c111) PCL/PLLA 1:1 for 24 h cs; (d1) PCL/PLLA 1:2 for 1 h cs (d11) PCL/PLLA 1:2 for 6 h cs (d111) PCL/PLLA 1:2 for 24 h cs; (e1) PLLA 1 h cs (e11) PLLA for 6 h cs (e111) PLLA for 24 h cs ; (f1) TCD 1 h cs (f11) TCD for 6 h cs (f111) TCD for 24 h cs (cs, cell seeding; TCD, tissue culture dish).
Z. Khatri et al. / Materials Letters 171 (2016) 178–181
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adhesion on PLLA samples and those with higher proportion of PLLA (Fig. 4e and f) and lower in pure PCL samples. For analysis on cs, the cell adhesion was observed to substantially increase almost all the samples; particularly 24cs demonstrated higher growth.
4. Conclusion
Fig. 4. Cell adhesion rate for (a) TCD (b) PCL (c) PCL/PLLA 2:1 (d) PCL/PLLA 1:1 (e) PCL/PLLA 1:2 (f) PLLA.
(asymm.) at 2945 cm 1 and CH2 stretching (symm.) at 2865 cm 1 . The PLLA spectrum (Fig. 1e) shows characteristic peaks of carbonyl stretching (CO) at 1750 cm 1, CH2 bending 1452 cm 1, CH2 deformation (symm.) at 1382 cm 1, 1267 cm 1, 1180 cm 1 and 1082 cm 1 ether (COC) stretching. The corresponding peaks of PCL/ PLLA blends (Fig. 1b–d) represent related peaks of both the PCL and PLLA with respective to proportion of each polymer, justifying homogeneity in the blends.
The PCL, PLLA and PCL/PLLA electrospun tubular scaffolds were successfully prepared and characterized for cell culture. The phase homogeneity (no phase separation) of the blends was confirmed by TEM images. The cell adhesion, tensile strength and morphological studies conclude success of all the scaffolds for tissue regeneration owing to substantial cell adhesion. Blends with higher proportion of PLLA show higher cell adhesion while those with enhanced PCL demonstrated better mechanical strength.
Acknowledgements This work was supported by Grants for Excellent Graduate Schools, MEXT, Japan.
References
3.2. TEM analysis The TEM results for all the three PCL/PLLA blends shown in Fig. 2a were determined in order to observe phase separation analysis. The results reported show homogeneous blends without any phase separation. 3.3. Mechanical properties In order to evaluate the structural and mechanical strength of the nanofiberous tube, tensile strength tests were conducted and results are reported in Fig. 2b. The analysis of the figure shows higher tensile strength for PCL and the scaffolds with higher PCL contents. This is no doubt due to higher mechanical stability of the PCL nanofibers. The PLLA nanofibers due to their lower mechanical stability exhibit low tensile strength. The tensile strengths of blends are observed to remain in between PCL and PLLA. 3.4. Cell adhesion Cell adhesion tests were conducted for 1 h, 6 h and 24 h in order to determine fibroblast L929 cell's growth on PCL, PCL/PLLA blends, PLLA and TCDs. The SEM images given in Fig. 3 depict cell adhesion on respective nanofibers for mentioned times. The result show higher cell adhesion on the PLLA nanofibers (Fig. 3e) and the composites with its higher proportion (Fig. 3d). The PCL/PLLA 1:1 blend (Fig. 3c) can also be observed to possess enhanced cell adhesion in comparison to pure PCL nanofibers (Fig. 3a). The cell adhesion and growth was observed to increase with cell seeding (cs) time. For example for 24 h cs, higher number of cells can be observed along with their growth in size. The cell adhesion and proliferation is also observed on the TCD with substantial growth for 24 h cs.The number of cell adhered during the experiment on the samples were counted and the results are reported in terms of cell adhesion % in Fig. 4. The results show comparatively larger cell
[1] M.P. Prabhakaran, L. Ghasemi-Mobarakeh, S. Ramakrishna, Electrospun composite nanofibers for tissue regeneration, J. Nanosci. Nanotechnol. 11 (4) (2011) 3039–3057. [2] B.D. Ulery, L.S. Nair, C.T. Laurencin, Biomedical applications of biodegradable polymers, J. Polym. Sci. B: Polym. Phys. 49 (12) (2011) 832–864. [3] S. Panseri, et al., Electrospun micro-and nanofiber tubes for functional nervous regeneration in sciatic nerve transections, BMC Biotechnol. 8 (1) (2008) 39. [4] S.H. Ku, C.B. Park, Human endothelial cell growth on mussel-inspired nanofiber scaffold for vascular tissue engineering, Biomaterials 31 (36) (2010) 9431–9437. [5] S.J. Lee, et al., The use of thermal treatments to enhance the mechanical properties of electrospun poly (ɛ-caprolactone) scaffolds, Biomaterials 29 (10) (2008) 1422–1430. [6] F. Yang, et al., Fabrication of nano-structured porous PLLA scaffold intended for nerve tissue engineering, Biomaterials 25 (10) (2004) 1891–1900. [7] S. Patra, A. Easteal, D. Bhattacharyya, Parametric study of manufacturing poly (lactic) acid nanofibrous mat by electrospinning, J. Mater. Sci. 44 (2) (2009) 647–654. [8] T. Bini, et al., Poly (l-lactide-co-glycolide) biodegradable microfibers and electrospun nanofibers for nerve tissue engineering: an in vitro study, J. Mater. Sci. 41 (19) (2006) 6453–6459. [9] L. Tian, et al., Emulsion electrospun vascular endothelial growth factor encapsulated poly (l-lactic acid-co-ε-caprolactone) nanofibers for sustained release in cardiac tissue engineering, J. Mater. Sci. 47 (7) (2012) 3272–3281. [10] X. Zong, et al., Structure and process relationship of electrospun bioabsorbable nanofiber membranes, Polymer 43 (16) (2002) 4403–4412. [11] B. Marelli, et al., Compliant electrospun silk fibroin tubes for small vessel bypass grafting, Acta Biomater. 6 (10) (2010) 4019–4026. [12] C. Xu, et al., Aligned biodegradable nanofibrous structure: a potential scaffold for blood vessel engineering, Biomaterials 25 (5) (2004) 877–886. [13] F.C. Pavia, V. La Carrubba, V. Brucato, Tuning of biodegradation rate of PLLA scaffolds via blending with PLA, Int. J. Mater. Form. 2 (1) (2009) 713–716. [14] S.J. Hollister, Porous scaffold design for tissue engineering, Nat. Mater. 4 (7) (2005) 518–524. [15] R.A. Gross, B. Kalra, Biodegradable polymers for the environment, Science 297 (5582) (2002) 803–807. [16] J. Zeng, et al., Enzymatic degradation of poly (l‐lactide) and poly (ε‐caprolactone) electrospun fibers, Macromol. Biosci. 4 (12) (2004) 1118–1125. [17] K. Kim, et al., Control of degradation rate and hydrophilicity in electrospun non-woven poly (D, L-lactide) nanofiber scaffolds for biomedical applications, Biomaterials 24 (27) (2003) 4977–4985. [18] Z. Khatri, et al., Preparation and characterization of electrospun poly (ε-caprolactone)-poly (l-lactic acid) nanofiber tubes, J. Mater. Sci. 48 (10) (2013) 3659–3664.