Abstract
The aim of this study was to characterize the influence of functionalization of synthetic poly-(L-lactic acid) (PLLA) nanofibers on mechanical properties such as maximum load, elongation, and Young's modulus. Furthermore, the impact of osteoblast growth on the various nanofiber scaffolds stability was determined. Nanofiber matrices composed of PLLA, PLLA-collagen, or BMP-2–incorporated PLLA were produced from different solvents by electrospinning. Standardized test samples of each nanofiber scaffold were subjected to failure protocol before or after incubation in the presence of osteoblasts over a period of 22 days under osteoinductive conditions. PLLA nanofibers electrospun from hexafluoroisopropanol (HFIP) showed a higher strain and tended to have increased maximum loads and Young's modulus compared to PLLA fibers spun from dichloromethane. In addition, they had a higher resistance during incubation in the presence of cells. Functionalization by incorporation of growth factors increased Young's modulus, independent of the solvent used. However, the incorporation of growth factors using the HFIP system resulted in a loss of strain. Similar results were observed when PLLA was blended with different ratios of collagen. Summarizing the results, this study indicates that different functionalization strategies influence the mechanical stability of PLLA nanofibers. Therefore, an optimization of nanofibers should not only account for the optimization of biological effects on cells, but also has to consider the stability of the scaffold.
Highlights
Electrospinning is a simple and effective fabrication technique for producing randomly orientated nanofiber scaffolds
We demonstrated that the incorporation of growth factors like BMP-2 into the poly(l-lactic acid) (PLLA) nanofibers[20] or blending the PLLA with collagen in different ratios[26] is a suitable method in enhancing the osteoinductivity of PLLA nanofiber scaffolds
The average thickness of the nanofiber scaffolds used in this study varied between 0.021 and 0.074 mm, and the density of the scaffolds ranged from 0.206 to 0.414 g/cm3 depending on the solvent as well as on the functionalization technique
Summary
Electrospinning is a simple and effective fabrication technique for producing randomly orientated nanofiber scaffolds. With respect to tissue engineering, these matrices offer great advantages[1,2] due to the fact that they mimic the extracellular matrix[3,4], and allow growth and differentiation of different cell types[5]. These nanofibers can be produced by a broad spectrum of polymers, including biocompatible as well as biodegradable polymers, such as poly(glycolic acid) (PGA), poly(l-lactic acid) (PLLA), poly(ε caprolactone) (PCL), polyurethanes, polyphosphazenes, collagen, gelatin, and chitosan, and copolymers from the corresponding monomers in various compositions[4,6]. We demonstrated that the incorporation of growth factors like BMP-2 into the PLLA nanofibers[20] or blending the PLLA with collagen in different ratios[26] is a suitable method in enhancing the osteoinductivity of PLLA nanofiber scaffolds
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