gms | German Medical Science

Objectives: In order to develop net-shaped warp knitted connection implants, to enable reconstruction of tendons and muscles after hip, knee or shoulder megaendoprosthesis-surgeries a stepwise study was performed. The main objective here was to obtain biomaterial constructs with promising biocompatible and antimicrobial properties to avoid postoperative infections. Therefore, amino polysaccharide chitosan (CHS) was selected in combination with silk fibroin (SF) as an alternative choice to non-resorbable polymers to reduce healing disturbances due to infections, ensure long-term resorbability and thus provide a significant improvement in endoprosthetic care.

Methods: Considering the influence of CHS antibacterial activity, two different degrees of deacetylation (DDA) were tested in the current study. Fine filaments of CHS were prepared. To evaluate the antibacterial effect and biocompatibility of the chitosan yarns in combination with silk yarns, crocheted constructs with a diameter of approximately 8 mm were produced (Table 1 [Tab. 1]). All samples were gamma-sterilized (25 kGy) and tested for antimicrobial properties against Gram positive (S. capitis) and Gram negative (P. stutzeri) bacteria in a contact test over 24 h. Furthermore, samples in triplicates were seeded with normal human dermal fibroblasts (NHDFs) and adipose tissue derived mesenchymal stem cells (MSCs) and cell proliferation and metabolic activity were evaluated over 21 days, by quantifying cell DNA and measuring activity of cytosolic lactate dehydrogenase (LDH), respectively.

Results: CHS/SF combination in the sample 1 revealed the lowest antimicrobial effect against both tested bacteria, while samples 3 and 4 were the most effective ones. Surprisingly, sample 5 containing only SF could also fight both bacteria stains, while number 2 was more effective against Gram+ than Gram-. These results suggest that a DDA value of 85.9 is more favourable than a value of 90.1 in terms of the antibacterial properties of chitosan. DNA and LDH evaluations showed that NHDF preferred CHS/SF combinations in groups 2 and 3. On the other hand side, MSC did not grow well on the samples 2, but their proliferation was and metabolic activity significantly increased on samples from the group 3.

Conclusions: Considering observed human cell responses and effectiveness against Gram+ and Gram- bacteria, findings of the presented study suggest that the most suitable ratio of CHS and SF in constructs was 50%:50% when CHS of DDA 85,9%.