Antibiotic-Loaded Hyperbranched Polyester Embedded into Peptide-Enriched Silk Fibroin for the Treatment of Orthopedic or Dental Infections

Regulation of the Degradation Properties of Tyrosinase-Catalyzed Crosslinking Silk Membranes for Superficial Wound Repair

Appropriate biodegradability to meet the demands of wound repair is critical for superficial wound repair membrane applications. Tyrosinase-catalyzed crosslinking SF (c-SF) membranes were constructed and regulated the degradation behavior in this study. The crosslinking degree of the c-SF membranes could be adjusted by reaction ratios of tyrosinase against SF (TYR/SF). Upon reaching a TYR/SF ratio of 20/6000, the degree of crosslinking increased to 88.17 ± 0.20%, without obvious changes in the crystal structure. The degradation behavior was regulated by the TYR/SF ratio and the degradation environment. All c-SF membranes remained stable after immersion without collagenase but showed an adjustable degradation behavior in the presence of collagenase. As the TYR/SF ratio increased, the residual weights increased from 23.31 ± 1.35% to 60.12 ± 0.82% after 7 days of degradation, occurring with low increased amounts of β-sheet structure and free amino acids. This work provides a new c-SF membrane with controllable rapid degradability and favorable cytocompatibility, which can help to meet requirements for biodegradable superficial wound repair membranes.

Silk Fibroin/ZnO Coated TiO2 Nanotubes for Improved Antimicrobial Effect of Ti Dental Implants

The aim of the present research is to develop a novel hybrid coating for a Ti dental implant that combines nature-inspired biomimetic polymers and TiO2 nanostructures with an entrapped ZnO antimicrobial agent. ZnO was used in other studies to cover the surface of Ti or Ti-Zr to reduce the need of clinical antibiotics, prevent the onset of peri-implantitis, and increase the success rate of oral clinical implantation. We developed an original coating that represents a promising approach in clinical dentistry. The titanium surface was first anodized to obtain TiO2 nanotubes (NT). Subsequently, on the NT surface, silk fibroin isolated from Bombyx mori cocoons was deposited as nanofibers using the electrospun technique. For an improved antibacterial effect, ZnO nanoparticles were incorporated in this biopolymer using three different methods. The surface properties of the newly created coatings were assessed to establish how they are influenced by the most important features: morphology, wettability, topography. The evaluation of stability by electrochemical methods in simulated physiological solutions was discussed more in detail, considering that it could bring necessary information related to the behavior of the implant material. All samples had improved roughness and hydrophilicity, as well as corrosion stability (with protection efficiency over 80%). The antibacterial test shows that the functional hybrid coating has good antibacterial activity because it can inhibit the proliferation of Staphylococcus aureus up to 53% and Enterococcus faecalis up to 55%. All Ti samples with the modified surface have proven superior properties compared with unmodified TiNT, which proved that they have the potential to be used as implant material in dentistry.

Vancomycin-nanofunctionalized peptide-enriched silk fibroin to prevent methicillin-resistant Staphylococcus epidermidis-induced femoral nonunions in rats

Introduction

Implant-related infections and infected fractures are significant burdens in orthopedics. Staphylococcus epidermidis is one of the main causes of bone infections related to biofilm formation upon implants. Current antibiotic prophylaxis/therapy is often inadequate to prevent biofilm formation and results in antibiotic resistance. The development of bioactive materials combining antimicrobial and osteoconductive properties offers great potential for the eradication of microorganisms and for the enhancement of bone deposition in the presence of infections. The purpose of this study is to prevent the development of methicillin-resistant S. epidermidis (MRSE)-infected nonunion in a rat model.

Methods

To this end, a recently developed in our laboratories bioactive material consisting of antibiotic-loaded nanoparticles based on carboxylic acid functionalized hyperbranched aliphatic polyester (CHAP) that are integrated into peptide-enriched silk fibroin sponges with osteoconductive properties (AFN-PSF) was employed, whose biocompatibility and microbiological tests provided proof of its potential for the treatment of both orthopedic and dental infections. In particular, non-critical femoral fractures fixed with plates and screws were performed in Wistar rats, which were then randomly divided into three groups: 1) the sham control (no infection, no treatment); 2) the control group, infected with MRSE and treated with peptide-enriched silk fibroin sponges incorporating non-drug-loaded functionalized nanoparticles (PSF); 3) the treated group, infected with MRSE and treated with peptide-enriched silk fibroin sponges incorporating vancomycin-loaded functionalized nanoparticles (AFN-PSF). After 8 weeks, bone healing and osteomyelitis were clinically assessed and evaluated by micro-CT, microbiological and histological analyses.

Results

The sham group showed no signs of infection and complete bone healing. The PSF group failed to repair the infected fracture, displaying 75% of altered bone healing and severe signs of osteomyelitis. The AFN-PSF treated group reached 70% of fracture healing in the absence of signs of osteomyelitis, such as abscesses in the cortical and intraosseous compartments and bone necrosis with sequestra.

Discussion

AFN-PSF sponges have proven effective in preventing the development of infected nonunion in vivo. The proposed nanotechnology for local administration of antibiotics can have a significant impact on patient health in the case of orthopedic infections.