Initial biological evaluation of nanofiber and microwire biomaterials

Abstract Due to the direct long-term contact with living tissue, the biocompatibility of implants is particularly demanding. In this context, biointegration of implants highly depends on cell colonialization on the surface or in the gap between implant and tissue, as well as cell ingrowth in porous implant structures. Fibrous material is predestined based on two variable parameters, fiber thickness and pore size. Various applications in implant coating, stenting, wound treatment, bone surgery, or cardiovascular field are possible. Coating with cell-friendly material can significantly improve the biocompatibility of the underlying material. In this study, the biocompatibility of medical device samples made of microwire and nanofiber substrates was compared according to ISO 10993-5. In particular, a metal tissue of microwire (stainless steel, 316L) and polymeric nanofiber nonwoven poly-L-lactic acid (PLLA) as well as titanium (Ti) sputtered variants thereof (316L-Ti, PLLA-Ti) were tested in vitro. In order to evaluate their environmental compatibility and their effects on L929 cell line (murine fibroblasts) evaluation was performed via direct contact with 30,000 cells per 48-well in non-adherent plates for 48 h and 96 h. The metabolic activity of cells was determined via CellQuanti-Blue assay, morphological analysis were done using fluorescence staining phalloidin and DAPI. Briefly outlined, microwires were colonized immediately, whereas initially spherical cells settled on nanofiber substrates and later coalesced forming a common cell cluster. The results show independency of structure, ultrathin titanium coating improves cell viability. The findings indicate that the idea of making a surface appealing to cells has potential. It can therefore be assumed that physical vapor deposition (PVD) sputtering of Ti on implant surfaces is a suitable approach to maintain or improve their biocompatibility, regardless of the surface structure of the implants.