Surface treatment strategies to combat implant-related infection from the beginning

Abstract

Orthopaedic implants are recognised as important therapeutic devices in the successful clinical management of a wide range of orthopaedic conditions. However, implant-related infections remain a challenging and not uncommon issue in patients with implanted instrumentation or medical devices. Bacterial adhesion and formation of biofilm on the surface of the implant represent important processes towards progression of infection. Given the intimate association between infection and the implant surface, adequate treatment of the implant surface may help mitigate the risk of infection. This review summarises the current surface treatment technologies and their role in prevention of implant-related infection from the beginning.

Translational potential of this article: Despite great technological advancements, the prevalence of implant-related infections remains high. Four main challenges can be identified. (i) Insufficient mechanical stability can cause detachment of the implant surface coating, altering the antimicrobial ability of functionalized surfaces. (ii) Regarding drug-loaded coatings, a stable drug release profile is of vital importance for achieving effective bactericidal effect locally; however, burst release of the loaded antibacterial agents remains common. (iii) Although many coatings and modified surfaces provide superior antibacterial action, such functionalisation of surfaces sometimes has a detrimental effect on tissue biocompatibility, impairing the integration of the implants into the surrounding tissue. (iv) Biofilm eradication at the implant surface remains particularly challenging. This review summarised the recent progress made to address the aforementioned problems. By providing a perspective on state-of-the-art surface treatment strategies for medical implants, we hope to support the timely adoption of modern materials and techniques into clinical practice.

Keywords: Implant; Infection; Orthopaedic; Prevention.

Figure 1

(A) AFM images of nanostructured Ormostamp surfaces (a–f represent structures with different scale); (B) profiles of nanostructured Ormostamp surfaces (a–f extracted from AFM images); (C) characterisation of Staphylococcus aureus viability on various nanostructured surfaces. Images were obtained using SYTO9 and propidium iodide staining followed by fluorescence microscopy. Fluorescent images a–f correspond, respectively, to structures a–f shown in panel (A). Green and red colours indicate live and dead cells, respectively. Scale bar: 20 μm. (D) Bactericidal activities of various nanostructured surfaces. Error bars represent standard errors for at least three images. The statistical significance was determined for each data set using the unpaired, parametric, two-tailed t test. *p < 0.001 versus the control substrate. This figure was adapted from the figures in the study by Wu et al . Copyright (2018) Journal of Nanobiotechnology. AFM, atomic force microscopy.

Figure 2

(A) Confocal laser scanning microscopy analysis of bacterial viability on different surfaces. (1) Smooth Ti; (2) NT-H80; (3) NT-H120; (4) NT-H160; (5) NT-H200 incubated with Staphylococcus aureus (ATCC 43300) for (a) 6 h; (b) 24 h; (c) 48 h and (d) 72 h. The arrow head indicates biofilm. The scale bar is 50 μm. (B) Number of viable bacteria adhered on smooth Ti and NT-H surfaces at 6 h. The number of viable bacteria was counted and normalised to the counts from the smooth Ti control for each bacterial strain. (C) Scanning electron microscopy image of titanium without modification (Ti), titania nanotubes without drug-loading (NT, with diameters of 160 nm), chitosan-loaded titania nanotubes (NT-C) and HACC-loaded titania nanotubes (NT-H). Attachment and spreading of human bone marrow–derived mesenchymal stem cells (hMSCs) on various specimens. (D) Cell attachment assay. Evaluations were conducted using the Cell Counting Kit-8. *p < 0.05 versus Ti; **p < 0.01 versus other groups; ^#p < 0.05 versus NT-C; ^##p < 0.01 versus Ti and NT-C. Panels in this figure were adapted from figures in the studies by Lin et al and Yang et al , . Copyright (2016) Materials (Basel) and (2016) Bone Research. HAAC = hydroxypropyltrimethyl ammonium chloride chitosan.