Anodised TiO2 nanotubes as a scaffold for antibacterial silver nanoparticles on titanium implants

Abstract

Medical grade titanium alloy is widely used for bone/dental implants, but the material alone has no innate antimicrobial properties that would reduce infection risk following surgery. However, silver nanoparticles (Ag NPs) are known to be antibacterial. This study investigated the growth of Ag NPs on titanium dioxide nanotubes (TiO NTs) on Ti-6Al-4V discs. The TiO NTs were grown on the Ti alloy using an electrochemical method, and then decorated with Ag NPs. The Ag NPs were synthesised by chemical reduction using δ-gluconolactone. A silver ammonia solution (silver nitrate + liquid ammonia) was used as the source of silver. Two separate approaches were used: (1) The δ-gluconolactone was mixed with the silver ammonia and then exposed to the TiO NTs (the 'mixing method'), which produced micron-sized clusters of the Ag NPs. (2) The TiO NTs were exposed to the silver ammonia first and then to δ-gluconolactone (the 'sequential addition method'), which resulted in the formation of nano-sized clusters of the nanoparticles. The Ag-TiO composites were confirmed by scanning electron microscopy and the elements analysed using energy dispersive X-ray spectroscopy (EDS). The composite coatings were exposed to a simulated body fluid for 24 h in order to determine the total Ag released. The release from the micron-sized clusters from the mixing method (14.6 ± 0.67 ppm) was higher than that from the nano-sized clusters (4.05 ± 0.36 ppm) when 0.015 M of silver ammonia was used. Additionally, Staphylococcus aureus, was cultured on the composite coatings for 24 h. Both the micron- and nano-sized clusters of the Ag NPs were found to be antibacterial using the Live/Dead assay. Overall, δ-gluconolactone was successfully used to reduce silver to Ag NPs on the surface of TiO NTs. The sequential addition method was the preferred method of synthesis because of its slower silver release, better coverage of the Ag-NPs on the TiO NTs and strong antibacterial properties.

Biomedical Applications of Silver Nanoparticles: An Up-to-Date Overview

“…In terms of superior antimicrobial activity, promising results were reported with respect to the incorporation of silver-based nanosystems within adhesive resins [ 156 , 157 ], orthodontic cements [ 158 , 159 ], and dental composites [ 160 , 161 , 162 ]. In addition to being used as antimicrobial filling agents within multifunctional biomaterials, another attractive and challenging dental application of AgNPs relies on their potential use as biostatic or biocide coatings for conventional titanium-based dental implants [ 163 , 164 ]. Though AgNPs proved to be efficient and effective agents in dental practice, they remain controversial candidates for this specific area of research, due to their variable toxicity in biological systems.…”

Microstructure and Properties of Nanostructured Coating on Ti6Al4V

“…Such problems may include allergic or inflammatory reactions associated with medical devices, such as orthopedic, traumatology, surgery, or dental implants. Indeed, excellent biocompatibility of implants with bone tissue with restrictions due to the possibility of bacterial infections persists as the main problems in biomedicine [4].…”

“…As the NT applied on the surface of skeletal/dental implants are mainly intended to prevent implant rejection and consequently prevent life-threatening secondary surgeries [4], the impact of the structural and morphological aspects of TiO 2 NT on their application as implant coating is significant. It has been already remarked using in vitro studies that the morphology and composition of TiO 2 NT influence biocompatibility [8,12], thereby showing bioactivity of bone cells on titanium implant surfaces.…”

Efficacy and safety of alpha lipoic acid-capped silver nanoparticles for oral applications

“…[1][2][3][4][5] AgNPs are a promising alternative antimicrobial agent that are increasingly being used in clinically applied biomaterials to inhibit microbial colonisation and subsequent infection. [6][7][8][9] They are already clinically used in wound dressings, catheters and implants, for prophylactic and/or therapeutic treatment. 10 The resulting antimicrobial properties of AgNPs have been attributed to a variety of physiochemical characteristics including size, shape, and surface functionalisation/capping agent.…”