Abstract
Titanium implants are widely used clinically, but postoperative implant infection remains a potential severe complication. The purpose of this study was to investigate the antibacterial activity of nano-silver(Ag)-functionalized Ti surfaces against epidemic Staphylococcus from the perspective of the regulation of biofilm-related genes and based on a bacteria-cell co-culture study. To achieve this goal, two representative epidemic Staphylococcus strains, Staphylococcus epidermidis (S. epidermidis, RP62A) and Staphylococcus aureus (S. aureus, USA 300), were used, and it was found that an Ag-nanoparticle-modified Ti surface could regulate the expression levels of biofilm-related genes (icaA and icaR for S. epidermidis; fnbA and fnbB for S. aureus) to inhibit bacterial adhesion and biofilm formation. Moreover, a novel bacteria-fibroblast co-culture study revealed that the incorporation of Ag nanoparticles on such a surface can help mammalian cells to survive, adhere and spread more successfully than Staphylococcus. Therefore, the modified surface was demonstrated to possess a good anti-infective capability against both sessile bacteria and planktonic bacteria through synergy between the effects of Ag nanoparticles and ion release. This work provides new insight into the antimicrobial action and mechanism of Ag-nanoparticle-functionalized Ti surfaces with bacteria-killing and cell-assisting capabilities and paves the way towards better satisfying the clinical needs.
Highlights
Adhesive bacteria, but this contact-killing surface could not exert an antiseptic effect on planktonic bacteria due to a lack of silver ion release[8]
Previous studies of the anti-biofilm properties of modified biomaterials have concentrated on the ica-dependent biofilm mechanism which plays an undeniably important role in staphylococcal biofilm development[8,33]; increasing evidences begin to emphasize the existence of an ica-independent biofilm mechanism, which is involved in the pathogenesis of biomaterial-related infections, in both S. aureus and S. epidermidis[34,35]
The entire process of fabricating specimens is illustrated in Fig. 1; this process consisted of a two-step strategy of plasma electrolytic oxidation for the formation of TiO2 coatings and hydrothermal chemical treatment for the loading of Ag nanoparticles
Summary
Adhesive bacteria, but this contact-killing surface could not exert an antiseptic effect on planktonic bacteria due to a lack of silver ion release[8]. Considering the bacterially contaminated perioperative period[41], we intended to discover whether our proposed modified coating could help mammalian cells to win the race for occupying the implant surface; and if so, the prophylaxis for BAI could be perfectly implemented. To this end, we first prepared porous titania coatings on Ti surfaces, followed by hydrothermal treatment to refine titania grains and deposit Ag nanoparticles, with the intent of compensating for the potential cytotoxicity of Ag+ by means of a synergistic effect between the hierarchical topography and chemical composition of the surface. We determined whether the fibroblast cells were favoured with respect to occupation of the modified surfaces through an in vitro bacteria-cell co-culture experiment
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