Thanks to medical progress, there are now a number of implants that assist or replace bodily functions, for example hip replacements or artificial knee joints. Although surgery is performed under sterile conditions, bacteria may settle on implant surfaces and cause an infection. Inflamed tissue around the implant is painful and can lead to sepsis. In the worst-case scenario, the implant will have to be removed again. In the »Synthesis, Structure & Biological Effects of Ultrasmall (1–2 nm) Bimetallic Silver-Platinum Nanoparticles« project, ISAS researchers are examining the antimicrobial activities of nanoparticles: Do they counteract the growth of bacteria on the surface of the implant or kill them? And does this mean that nanoparticles are suitable for coating implant surfaces?
Using silver and platinum to improve implant coatings
Silver has antimicrobial properties; platinum, on the other hand, is known for its osteopromotive properties – it boosts bone growth. These characteristics make a combination of the two materials especially interesting for clinical use with bone implants. For their analyses, the project team consisting of researchers from ISAS, the University of Duisburg-Essen and Forschungszentrum Jülich are developing silver-platinum nanoparticles (Ag Pt-NPs) of one to two nanometres. This small size maximizes the surface-volume ratio of the particles, which are more reactive than large particles. The researchers intend to promote the antimicrobial effectiveness of the particles in this way.
Searching for the optimum mixing ratio
The influence of such small nanoparticles on cells that are roughly the size of proteins has, however, been poorly understood to date. In particular, how the cells absorb the nanoparticles is largely unknown at present, as are their cellular and microbiological effects. Plus, it is hardly possible to image such small nanoparticles using conventional imaging methods. Consequently, the project team is investigating accumulations of Ag Pt-NPs in order to analyse the influence of Ag Pt-NPs on bacteria and what are known as mesenchymal stem cells, which are cells of the supportive and connective tissue. The researchers at ISAS are using cell culture assays and confocal microscopy as well as flow cytometry to conduct these investigations. The objective is to produce ultrasmall pure and alloyed NPs and to analyse them in detail. This data will then make it possible to produce new transplant alloys that better protect the bones from the settling of bacteria and excessive bone loss.