Poster Presentation 50th International Society for the Study of the Lumbar Spine Annual Meeting 2024

Antimicrobial functionalization of custom-made vertebral implants by nanostructured metal-based films opposes infection by multi-drug resistant S. aureus (#62)

GABRIELA GRAZIANI 1 2 , Maria Sartori 3 , Daniele Ghezzi 4 , Donato Monopoli 5 , Martina Cappelletti 4 , Enrico Sassoni 6 , Marco Boi 2 , Nicola Baldini 2 7 , Milena Fini 3 8
  1. Department of Chemistry, Materials and Chemical Engineering "Giulio Natta", Polytechnic University of Milan, Milano, --- SELECT ONE ---, Italy
  2. Biomedical Sciences and Technologies and Nanobiotechnologies, IRCCS Istituto Ortopedico Rizzoli (Rizzolo Orthopaedic Institute), Bologna, Italy
  3. Complex Structure Surgical Sciences and Technologies, IRCCS Istituto Ortopedico Rizzoli (Rizzolo Orthopaedic Institute), Bologna, Italy
  4. Department of Pharmacy and Biotechnology, University of Bologna, Bologna, Italy
  5. ITC Instituto Tecnológico de Canarias, Las Palmas de gran Canaria, Spain
  6. Department of Civil, Chemical, Environmental and Materials Engineering, University of Bologna, Bologna, Italy
  7. Department of Biomedical and Neuromotor Sciences, University of Bologna, Bologna, Italy
  8. Scientific Direction, IRCCS Istituto Ortopedico Rizzoli (Rizzolo Orthopaedic Institute), Bologna, Italy

Introduction

Vertebral body replacement is among the most challenging orthopaedic procedures, burdened by a 45.5% complication rate and driving research for new solutions1-2.

Among the complications, infection is particularly critical, as it has high incidence (up to 20%, largely varying depending on the pathology, site, surgical approach and comorbidities), potentially leads to a fatal evolution and correlates with impaired bone regeneration and mechanical instability3,4.

3D-printed custom made titanium implants permit to optimise implant geometry and mechanical properties, hence favouring osteointegration and stability. Hence, they are being increasingly used, even for complex surgeries such as spinal column reconstruction after en-bloc resection of tumors, with promising clinical results5. However, to date, the issue of infection remains unmet.

Here, for the first time, we propose to address infection of custom-made spine implants by functionalization with new silver-based nanostructured films. These are obtained by Ionized Jet Deposition, a plasma-assisted deposition technique which guarantees nanostructuring (allowing tuning of Ag release) and nanoscale thickness (avoiding delamination), both preventing toxicity. To further mitigate interference with bone regeneration, mixed Ag and bone apatite coatings are also proposed.

 

Methods

Coatings are obtained by deposition of Ag, and Ag -bone apatite composites, onto standard and custom-made vertebral prostheses. 
Composition and morphology of the films and homogeneity of substrate coating are investigated (FEG-SEM/EDS, FT-IR). Biocompatibility is assessed in vitro (fibroblasts, MSCs). Coatings efficacy is demonstrated in vitro against gram + and gram – strains (S. aureus, E. coli, E. faecalis, P. aeruginosa), in terms of reduction of bacterial viability, adhesion to substrate and biofilm formation (using a specifically developed approach based on the Calgary Biofilm Device). For Ag-based films, efficacy is also tested in an in vivo rabbit model, using a multidrug resistant strain of S. aureus (MRSA, S. aureus USA 300 at 102 CFU/mL).
Statistical analysis is performed by SPSS/PC + Statistics TM 25.0 software, one-way ANOVA and post-hoc Sheffè test. Data are reported as Mean ± standard Deviation at a significance level of p <0.05. 

 Results

All films are nanostructured and have the same composition of the target. Remarkable efficacy is found in vitro for Ag films against all gram+ and gram- bacteria (complete inhibition of planktonic growth, reduction of biofilm formation >50% for all strains). No cytotoxic effects are evidenced in vitro for Ag-based films (with/without bone apatite, <5% reduction in viability compared to ctr), nor in vivo, where no negative alterations are observed following implantation of the coatings.

Ag and Ag-bone apatite films can inhibit MRSA strain in vivo (99.99% and 86.20% reduction against ctr, respectively, with 2/5 and 1/5 animals being sterile and not being included in the count).

Discussion

New antibacterial metal-based films are proposed and validated in vitro and in vivo, showing that nanostructured silver films can oppose infection of custom-made vertebral prostheses.

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