Electrospun Scaffold from Poly-(3hydroxybutyrate) and Type I-Collagen Blend for Tissue Engineering

INTRODUCTION Different strategies have been employed to improve physiochemical and biomimetic properties of synthetic polymers for medical applications. Electrospinning has been reported to be one of simplest, least expensive and most versatile processing techniques for modulating the bioactivity of synthetic polymers1,2. Poly(3-hydroxybutyrate) (PHB) is a thermoplastic polyester produced by bacteria, well-known as biodegradable, biocompatible and nontoxic, but only partially biomimetic3. In order to improve cell attachment on synthetic substrates, the addition of natural polymers, such as collagen, is a key option4,5. In this study, we report on an electrospun nano-fibrous scaffold with different contents of a bio-derived thermoplastic synthetic polymer, i.e. PHB, and a naturally occurring polymer, i.e. type I-collagen (Col). EXPERIMENTAL METHODS PHB and type I-collagen were dissolved in 1,1,1,3,3,3-hexafluoro-2-isopropanol (HFIP) in different mass ratios and the resulting solutions were electrospun onto a rotating cylindrical collector. The thermal and mechanical properties of the nano-fibrous membrane scaffolds were analyzed by means of differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and tensile tests; the chemical nature and the morphology were investigated by Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). Biodegradation tests were also performed to evaluate the resistance of the scaffolds to collagenase, while the cytocompatibility with respect to NIH 3T3 fibroblasts was assessed by means of MTT assay. RESULTS AND DISCUSSION The major issue for the preparation of nanofibers via electrospinning was the optimization of both solution concentration and electrospinning parameters for the specific blend. As indicated in Figure 1, a 2% (wt/v) of Col/PHB solutions (a. 0:100; b. 30:70; c. 50:50) produced electrospun uniform nanofibers with a controllable diameter between 300 to 700 nm. The presence of collagen in Col/PHB blends was investigated with DSC, TGA and FT-IR. The latter particularly showed absorptions at 3324, 1585 and 1656 cm-1, respectively N-H stretching, amide I and amide II bands of collagen. These strong peaks increased further in 50:50 Col/PHB, confirming a major content of collagen in the latter membrane. As expected, the mechanical properties of the scaffolds were affected by the Col/PHB ratio: higher compliance was detected when increasing the collagen content. On the other hand, the increase of collagen led to scaffolds with lower resistance to enzymatic degradation. MTT assays demonstrated that all of the nano-fibrous blends under investigation were cytocompatible. Further ongoing experiments suggest that the presence of collagen favors cell attachment and proliferation. CONCLUSION Blending PHB and collagen is a suitable approach for the creation of electrospun biomimetic scaffolds with reproducible morphology, thus being a promising method for the development of standard operating procedures in tissue engineering. Moreover, the versatility of the process allows modulating the bio-chemical and mechanical properties of the scaffolds. The promotion of cell adhesion by collagen shows promise for the development of tissue engineered medical devices tailored to selected applications.