Functionalization of the PLLA surface with a femtosecond laser: Tailored substrate properties for cellular response

Abstract

In this paper we present the possibilities of using a femtosecond fiber laser (τ = 260 fs, λ = 1030 nm) to modify a PLLA surface. Three types of developed structures S1, S2, S3 differed significantly in topography and surface morphology. Thanks to the use of pulse overlapping in both scanning directions, the structures S1 and S2 were highly homogeneous, while in structure S3 the parallel grooves were obtained by pulse overlapping in one direction. The modified surfaces were examined for morphology (scanning electron microscopy), roughness (optical profilometry), wettability (measurement of the contact angle) and changes in the chemical structure of the polymer (infrared spectroscopy, gel permeation chromatography). The possibility of modifying these surface properties in a broad range was also discussed. The conducted cellular studies showed that there was no cytotoxicity with regard to all samples and that the pace of fibroblast colonization of samples S1 was higher compared to that of the control during the first 24 h of experiment. Moreover, the ability of S. aureus (pathogenic bacteria) and of a biotechnologically useful fungus Saccharomyces boulardii to colonize the manufactured structures was also assessed. In this case, no significant differences in the number of biofilm-forming cells were observed between the analyzed samples and the control setting. Obtained results indicate that applicability of such surface modifications should be further investigated, especially for the development of bone implants and these biotechnological processes in which microbes are used to produce the desired yield of product.

Keywords

• Femtosecond laser
• Surface structuring
• poly(l-lactide)
• PLLA
• Osteoblasts
• Fibroblasts