Collagen/PCL Nanofibers Electrospun in Green Solvent by DOE Assisted Process. An Insight into Collagen Contribution

Abstract

Collagen, thanks to its biocompatibility, biodegradability and weak antigenicity, is widely used in dressings and scaffolds, also as electrospun fibers. Its mechanical stability can be improved by adding polycaprolactone (PCL), a synthetic and biodegradable aliphatic polyester. While previously collagen/PCL combinations were electrospun in solvents such as hexafluoroisopropanol (HFIP) or trifluoroethanol (TFE), more recently literature describes collagen/PCL nanofibers obtained in acidic aqueous solutions. A good morphology of the fibers represents in this case still a challenge, especially for high collagen/PCL ratios. In this work, thanks to preliminary rheological and physicochemical characterization of the solutions and to a Design of Experiments (DOE) approach on process parameters, regular and dimensionally uniform fibers were obtained with collagen/PCL ratios up to 1:2 and 1:1 w/w. Collagen ratio appeared relevant for mechanical strength of dry and hydrated fibers. WAXS and FTIR analysis showed that collagen denaturation is related both to the medium and to the electrospinning process. After one week in aqueous environment, collagen release was complete and a concentration dependent stimulatory effect on fibroblast growth was observed, suggesting the fiber suitability for wound healing. The positive effect of collagen on mechanical properties and on fibroblast biocompatibility was confirmed by a direct comparison of nanofiber performance after collagen substitution with gelatin.

Biomaterials for Soft Tissue Repair and Regeneration: A Focus on Italian Research in the Field

“…These polymers present the advantage of good mechanical resistance and of possible modulation of the degradation times, but a disadvantage is that they are quite hydrophobic. The presence of CL in mixture with them improved the material wettability, and the positive interaction with the biological substrates, due also to the maintenance of CL recognition sites for cell adhesion [ 97 ]. The literature reports different studies on this subject, demonstrating the still recent interest towards this aspect.…”

“…In Miele et al [ 97 ], soluble CL was electrospun together with PCL in 90% acetic acid at different PCL and CL ratios adjusting the process parameters thanks to the results of a design of experiments. In the dry state, the addition of CL up to the 1:1 weight ratio in the formulation drastically decreased elongation and increased the Young’s modulus and a more fragile material, with poor deformability, was obtained.…”

“…The PCL-CL blend seemed in this case an effective combination of PCL capability to support the cell growth and CL improvement of wettability and cell growth stimulation despite the solubilization in the fiber microenvironment. In this case, the co-electrospun system can be seen as a PCL scaffold loaded with CL, and slowly releasing it, to exploit its compatibility and cell stimulation activity [ 97 ].…”

“…Most of the properties of the collagen-based systems, such as biocompatibility and biodegradability derive from the natural origin and chemical structure of the material, and are more affected by modifications such as cross-linking than by the scaffold type. Similarly, the mechanical properties in hydrated conditions such as those encountered after application to target tissues, are also dependent on fast collagen dissolution [ 97 ], unless one of the strategies previously described and schematically recalled in Table 2 are put in action. The crosslinking strategy seems the principal factor responsible for reaching high elastic modulus values, with different results depending more on the kind of crosslinking process than on the scaffold type [ 80 ].…”

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“…The mechanical properties of silk fibroin fibers can be altered through methanol treatment after electrospinning, which increases β-sheet crystallinity and reduces water solubility ( 153 ). In case of collagen protein, care needs to be taken during electrospinning because denaturation may occur at high voltage ( 154 ). Collagen is often co-electrospun with other synthetic polymers such as polycaprolactone (PCL) to increase fiber stability ( 155 ).…”