Antimicrobial Effect of Nano-Rough Titanium Surfaces: Reduction of Microbial Adhesion and Mechanisms of Reduction

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With up to 600,000 cases and 40,000 deaths per year in Germany, hospital-acquired infections (nosocomial infections) are a major socio-economic problem. Implants account for up to 45% of all nosocomial infections. These biomaterials associated infections (BAIs) are most frequently associated with microbial colonization on the materials surfaces of the indwelling medical devices. BAIs occur with approximately 2-6 % of traumatology and orthopedic implants. Osteosynthesis, the alignment and fixation of bone fractures with mostly metallic biomaterials, is associated with infection of up to 40% in patients with open bone fractures. Titanium implants are most often used in the field of osteosynthesis. The possibilities of infection control have been complicated in recent years due to an increase in antibiotic resistant strains of bacteria. With a simultaneous increase of the number of medical device implantations in elderly patients who are more susceptible to infections because of their frail general health state, the need for fresh and different approaches to fight BAIs is apparent. Most implants used today have no defense mechanisms against microbial colonization and, therefore, are often the starting point of local or systemic infections. The presently discussed solutions, such as metals (e.g. silver or copper) or antibiotic-containing implant coatings have disadvantages (cytotoxicity, unfavorable active substance release kinetics, limited duration of action, promoting the development of drug resistance, etc.) and, with few exceptions, yielded unsatisfactory results under clinical conditions. A fresh approach to reduce microbial adhesion on biomaterials surfaces and, thus, potentially reduce the number of BAIs is using nano-rough or nanostructured biomaterials, e.g. on titanium implants for bone contact. Preliminary research results of our groups are encouraging: on titanium surfaces with roughnesses from 2 to 6 nm, we observed a statistically significantly lower microbial adhesion on the rougher surfaces compared to the smoother surfaces. However, how nano-roughness interferes with pathogenic microbes is yet unclear and the mechanism of adhesion on nano-rough surfaces is an enigma. We, therefore, aim to unravel the causal relationship between nano-roughness of titanium and microbial adhesion. A major obstacle to gain knowledge and scientific progress in the field of nano-rough antimicrobial biomaterials is the current substantial lack of cooperation between materials scientists and microbiologists. This project will help to close the gaps in understanding the mechanisms of microbial adhesion on nano-rough surfaces as well as promote synergistic cooperation between the two disciplines.