Degradation of internal fixation materials based on antibacterial and absorbable silk containing different gentamicin concentrations

Abstract

Adding gentamicin to silk fibroin enhances both the antibacterial performance and degradation rate of silk-based materials. The increased material degradation rate can affect the strength of early internal fixation, resulting in internal fixation failure. This study sought to adjust the gentamicin concentration to control the material degradation rate, thereby better meeting clinical application requirements. The in vitro degradation, water absorption rate, and expansion rate of silk-based materials containing different gentamicin concentrations were studied. A gentamicin-loaded silk-based screw was implanted into the femurs of New Zealand rabbits. Micro-computed tomography was used to measure the screw diameter, which was then used to calculate the degradation rate. The specimens were stained with hematoxylin and eosin and Masson’s trichrome. The in vitro results revealed increasing material degradation rates with increasing gentamicin concentration but no significant differences in water absorption rates with different gentamicin concentrations. The degradation rates of gentamicin-loaded (4 mg/g) silk-based rod-like materials were approximately 11.08% at three months in vitro and 9.4% in the animal experiment. The time for complete degradation was predicted from the fitting curve to be approximately 16 months. No inflammatory hyperplasia was observed in bone or soft tissue. The degradation and biocompatibility of the material containing 4 mg/g gentamicin meet clinical application requirements, and previous experimental results demonstrate good antibacterial performance of materials containing this gentamicin concentration.

Redefining Surgical Materials: Applications of Silk Fibroin in Osteofixation and Fracture Repair

“…The electronic search initially identified 245 silk-related orthopedic/plastic surgery studies, which ultimately yielded 33 studies for full-text reviews (Figure 1). After thorough assessment and subsequent exclusion, 15 studies from 2014 to 2023 were included for quantitative analysis (Table S1) [6,[15][16][17][18][19][20][21][22][23][24][25][26][27][28]. These consisted of seven in vitro experimental studies and eight in vivo experimental studies.…”

“…They observed no statistically significant difference in the bending strength between the PSSs and GSSs. However, there was a notable increase in the degradation rate of the GSS groups compared to the PSS groups, which was statistically significant [20]. The most effective concentration for inhibiting the growth of S. aureus and E. coli was found to be 16 mg of gentamicin per 1 g of silk, a feature absent in the PSS groups lacking antimicrobial activity [20].…”

“…However, there was a notable increase in the degradation rate of the GSS groups compared to the PSS groups, which was statistically significant [20]. The most effective concentration for inhibiting the growth of S. aureus and E. coli was found to be 16 mg of gentamicin per 1 g of silk, a feature absent in the PSS groups lacking antimicrobial activity [20]. Consequently, GSSs may hold potential for reducing the risk of implant-related infections during the postoperative period.…”

“…Shi et al developed silk screws loaded with gentamicin (GSSs) alongside pure silk screws (PSSs) containing varying concentrations of gentamicin to evaluate their antimicrobial properties, strength, and gentamicin release [20]. They observed no statistically significant difference in the bending strength between the PSSs and GSSs.…”

“…Shi et al evaluated their previously developed gentamicin-loaded silk-based material in a rabbit model, discovering that screws containing 4 mg of gentamicin per 1 g of silk were securely affixed to the femurs and exhibited rough surfaces [20]. These screws made close contact with the bone cortex, and their surfaces were covered with a substantial amount of soft tissue.…”