Shifting focus from bacteria to host neutrophil extracellular traps of biodegradable pure Zn to combat implant centered infection

The widespread use of orthopedic implants to support or replace bones is increasingly threatened by the risk of incurable bacterial infections,impenetrable microbial biofilms,and irreversible antibiotic resistance.In the past,the development of anti-infective biomaterials focused solely on direct antibacterial properties while ignoring the host’s immune response.Inspired by the clearance of infection by the innate neutrophil response and partici-pation in anti-infectious immunity of Zn ions,we report an innovative neutrophil extracellular traps(NETs)strategy,induced by biodegradable pure Zn,which achieved therapeutic efficacy toward biomaterial-related infections.Our in vitro and in vivo data showed that pure Zn was favorable for NETs formation by promoting the release of DNA fibers and granule proteins in a reactive oxygen species(ROS)-dependent manner,thereby retraining and degrading bacteria with an efficiency of up to 99.5%.Transcriptome analysis revealed that cytoskeletal rearrangement and toll-like receptor(TLR)signaling pathway were also involved in Zn-induced NETs formation.Furthermore,the in vivo results of a Staphylococcus aureus(S.aureus)-infected rat model veri-fied that pure Zn potentiated the bactericidal capability of neutrophils around implants,and promoted osseointegration in S.aureus-infected rat femurs.This antibacterial immunity concept lays a foundation for the development of other antibacterial biomaterials and holds great promise for treating orthopedic infections.

Reducing bacterial adhesion to titanium surfaces using low intensity alternating electrical pulses

BACKGROUND Orthopedic implant-related infection remains one of the most serious complications after orthopedic surgery.In recent years,there has been an increased scientific interest to improve prevention and treatment strategies.However,many of these strategies have focused on chemical measures.AIM To analyze the effect of alternating current electrical fields on bacterial adherence to titanium surfaces.METHODS Staphylococcus aureus(S.aureus)and Escherichia coli(E.coli)were exposed to 6.5 V electrical currents at different frequencies:0.5 Hz,0.1 Hz,and 0.05 Hz.After exposure,a bacterial count was then performed and compared to the control model.Other variables registered included the presence of electrocoagulation of the medium,electrode oxidation and/or corrosion,and changes in pH of the medium.RESULTS The most effective electrical model for reducing S.aureus adhesion was 6.5 V alternating current at 0.05 Hz achieving a 90%adhesion reduction rate.For E.coli,the 0.05 Hz frequency model also showed the most effective results with a 53%adhesion reduction rate,although these were significantly lower than S.aureus.Notable adhesion reduction rates were observed for S.aureus and E.coli in the studied conditions.However,the presence of electrode oxidation makes us presume these conditions are not optimal for in vivo use.CONCLUSION Although our findings suggest electrical currents may be useful in preventing bacterial adhesion to metal surfaces,further research using other electrical conditions must be examined to consider their use for in vivo trials.