Thermosensitive hydrogels have been widely used in the biotechnology field as carriers for controlled drug release, and can be an alternative for the prevention and treatment of peri-implant inflammations. Thus, the present study aims to develop a new hydrogel based on poly (N-vinylcaprolactam) polymer for controlled release of tetracycline (TC) and evaluate its properties and composition, its antibacterial activity in vitro and in situ, as well as its interaction with cells in vitro and in vivo. Initially, the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) of TC will be determined to establish the initial drug concentration to be incorporated into the hydrogel. Thus, the following groups will be tested: (1) Hydrogel without the addition of TC as a control; (2) Hydrogel + TC at the concentration determined by MBC; (3) Hydrogel + TC with five times the concentration determined by MBC; and (4) Hydrogel + TC with ten times the concentration determined by MBC. Three studies will be conducted: in the study 1 in vitro the hydrogel in different concentrations of TC will be characterized in relation to morphology using scanning electron microscopy (SEM), molecular structure by Fourier transform infrared spectroscopy (FTIR), critical solution temperature by visible ultraviolet spectroscopy (UV/VIS), gelation time through the tilt method, swelling ratio by assessing liquid absorption, rheological properties by means of a rheometer and degradation through loss of mass after immersion in a solution containing the enzyme collagenase type II. TC release will be evaluated by high performance liquid chromatography (HPLC) after 1, 3, 7 and 15 days. The atomic force microscopy will be performed to evaluate how TC release occurs. The adhesion of the hydrogel to titanium will be analyzed by the shear test. The antimicrobial activity of the hydrogel will be evaluated in vitro using a microcosm model through the quantification of colony forming units (CFU/mL), microbial composition analysis by DNA-DNA checkerboard and structural analysis of the biofilm by SEM and confocal laser microscopy. Qualitative and quantitative analyzes will be performed to confirm the absence of toxicity of the hydrogel when in contact with human gingival fibroblast (HGF) cells. In the study 2 in situ, the most appropriate TC concentration according to the results of study 1 will be used to verify the antibacterial effectiveness of the hydrogel by quantifying CFU/mL, microbial composition analysis by DNA-DNA checkerboard and live and dead cells by confocal laser microscopy. Finally, the new material will be investigated regarding its effects on the inflammatory response and consequent influence on the healing process in an animal model. Herein, an implant will be installed at the tibia of each rat, in both sides, totaling two implants per animal. In order to mimic the infectious environment, the implants corresponding to the experimental group will be contaminated, in vitro, and the biofilm developed onto them will be removed by scaling, simulating a clinical stage, as mandatory step to be performed prior to the treatment proposed. Then, the hydrogel containing TC will be applied around the threads exposed by the bone defect, simulating bone resorption. Therefore, analyses to confirm the microbial viable colonies and microbial profile on the implants after treatment will be performed by CFU/mL, and DNA-DNA checkerboard, respectively. Additionally, the histopathological features of inflammation will be studied through histological analysis and the expression levels of inflammatory cytokines will be quantified by Multiplex technology. Quantitative data will be subjected to appropriate statistical analysis with a 5% significance level.
News published in Agência FAPESP Newsletter about the scholarship: