Preparation of polyamide-6/chitosan composite nanofibers by a single solvent system via electrospinning for biomedical applications

Abstract

This work was focused on preparation and characterizations of chitosan blended polyamide-6 nanofibers by a new single solvent system via electrospinning process for human osteoblastic (HOB) cell culture applications. The morphological, structural and thermal properties of the polyamide-6/chitosan nanofibers were analyzed by using field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), Fourier transform-infrared (FT-IR) spectroscopy, Raman spectroscopy, differential scanning calorimetry (DSC) and thermogravimetry (TGA). SEM images revealed that the nanofibers were well-oriented and had good incorporation of chitosan. FT-IR results indicated that the amino groups of chitosan existed in the blended nanofibers. TGA analysis revealed that the onset degradation temperature was decreased with increasing chitosan content in the blended nanofibers. The morphological features of the cells attached on nanofibers were confirmed by SEM. The adhesion, viability and proliferation properties of osteoblast cells on the polyamide-6/chitosan blended nanofibers were analyzed by in vitro cell compatibility test.

Introduction

Application of electrospinning to biologically significant polymers has increased since the electrospun membranes were identified as a candidate for tissue engineering constructs [1], [2], [3]. The nanofibers produced by electrospinning method have showed unique characteristics such as very high surface area-to-volume ratio and high porosity with very small pores size. In our previous studies, the formation of high aspect ratio nanofibers and the role of solvent systems for producing such kind of structures was reported [4], [5]. Electrospun nanofibers have become promising materials for many biomedical applications such as wound dressing, drug delivery and scaffold for tissue engineering [6], [7], [8], [9]. In particular, polyamide-6 is a biodegradable, biocompatible and synthetic polymeric material which has good mechanical and physical properties [10], [11]. Recently, the feasibility of incorporating non-electrospinnable inorganic nanoparticles into polymer to form composite nanofibers has revealed electrospinning as an attractive technique to meet several specific functional applications [12], [13], [14], [15], [16]. The physical and biological properties of the nanofibrous scaffolds are strongly determined by the materials chemical composition. To date, there were some reports based on different electrospun nanofibrous scaffolds, such as chitosan/poly(caprolactone) [17], poly(vinyl alcohol)/chitosan [18], chitosan/nylon-6/silver [11] and chitosan based nanofibrous membranes [19], [20] that were analyzed and explored for potential bone regeneration applications.

Chitosan is a natural nontoxic biopolymer derived by the deacetylation of chitin, possessing unique polycationic, chelating, and film-forming properties due to the presence of active amino and hydroxyl functional groups. As a natural polymer, chitosan intrinsically exhibits enticing properties such as biocompatibility, biodegradability, antimicrobial activity, non-toxicity and its adequate absorption capabilities. Owing to these properties, chitosan is widely used in many different fields, including medicine, food and chemical engineering, pharmaceuticals, nutrition, and agriculture [21], [22], [23], [24], [25]. Chitosan in the nanofiber mats format has a great potential to be widely used in various applications derived from its biocompatibility and biodegradability. Although the electrospinning of nylon-6 and chitosan complex nanofibers was reported in one recent study [26], however, the formation of high aspect ratio nanofibers in polyamide-6/chitosan composites and its in vitro cytotoxic analysis based on these peculiar structures was not reported so far. Therefore, we take the advantage from both chitosan and polyamide-6 by blending them into composite nanofibrous scaffolds.

In this work, we describe the one step preparation of polyamide-6/chitosan blended nanofibers scaffolds via electrospinning for the osteoblastic cell culture applications. The detailed osteoblastic cell compatibility was evaluated for the electrospun sub-nanofibers formed due to structural changes with single solvent system. The morphology of the resulting nanofibers was analyzed by field-emission scanning electron microscopy (FE-SEM). Then, the enhancement of the structural and thermal properties of electrospun polyamide-6/chitosan composite nanofibers was demonstrated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). Finally, the cytocompatibility of the polyamide-6/chitosan composite nanofibrous scaffold with different amount of chitosan was studied by using MTT (3-[4,5-dimethylthiazol-2-yl]2,5-diphenyl tetrazolium bromide) test and lactate dehydrogensae (LDH) measurements.