A promising approach based on quorum quenching to reduce biofilm formation on titanium surface

Nowadays, the healthcare system is facing an increasingly pressing challenge: bacterial resistance. Since their first use, antibiotics have been crucial for treating various infections, thereby increasing patients' life expectancy and leading to fundamental discoveries in the field of medicine. However, the improper use and abuse of these drugs have contributed to the development of bacterial antibiotic resistance. This resistance threatens not only the effectiveness of antibiotic drugs but also the ability to effectively treat both common and complex infections. Today, cases of bacterial infections that cannot be treated due to bacteria's resistance to common drugs are becoming more frequent. Also, in orthopedic and dental fields, many cases of bacterial infections have been identified. When this occurs, most of the time, patients must undergo further surgical treatment, resulting in additional discomfort and higher costs for the healthcare service. Consequently, bacterial infection is now one of the two main causes of prosthetic failure. The key element of bacterial resistance is biofilm, a layer composed of various bacteria that aggregate and adhere to a surface, such as an orthopedic prosthesis or a dental implant. During the biofilm maturation process, bacteria produce an extracellular matrix (EPS) that protects the bacterial colony from the patient's immune system or antibiotics. Therefore, new strategies must be found to prevent and manage bacterial infections. One strategy is to interfere with the communication mechanism of bacterial cells, known as quorum sensing, which regulates the expression of genes involved in biofilm formation and the production of virulence factors. This technique is called quorum quenching and involves interrupting bacterial communication by acting on signal molecules, autoinducers, or various actors in the communication circuit, such as synthase or receptors of signal molecules. The most well-known method of quorum quenching is enzymatic degradation of autoinducers. These enzymes, including lactonases, degrade the signal molecule, thus interrupting bacterial gene expression. This strategy is very promising because it does not have bactericidal effect and therefore does not contribute to the survival of resistant strains. The purpose of this thesis is to synthetize lactonases active as quorum quenching enzymes and to evaluate whether a titanium surface functionalized with lactonase has anti-biofilm properties. At the Institute of Molecular Genetics and Genetic Engineering (IMGGE, Belgrade), a lactonase (ST1-Bacillus licheniformis, extracted from a Bacillus) was produced and characterized. Preliminary studies have shown that the enzyme is capable of reducing the expression of genes involved in both the quorum sensing mechanism and the production of virulence factors of the Pseudomonas aeruginosa bacterium. However, the same results have not been observed with the bacteria E. coli and S. aureus. Subsequently, the functionalization of titanium surfaces was carried out to confirm the preliminary results.