Aiming at developing new topical antibacterial formulations to treat staphylococcal infections, two pyrazoles (3c and 4b) previously reported for having antibacterial effects especially against staphylococci, were formulated as hydrogels (R1HG-3c and R1HG-4b). Particularly, we first synthtized and characterized a cationic polystyrene-based resin (R1). Secondly, R1 was used as gelling agent to formulate 3c and 4b and obtain R1HG-3c and R1HG-4b. Thanks to the high hydro-philicity, high-level porosity, and excellent swelling capabilities of R1, R1HG-3c and R1HG-4b were achieved with an equilibrium degree of swelling (EDS) of 765% (R1HG-3c) and 675% (R1HG-4b), as well as an equilibrium water content (EWC) of 88% and 87%, respectively. By chemometric-assisted attenuated total reflectance (ATR) Fourier transform infrared (FTIR) analyses, the chemical structure of soaked and dried gels was investigated, while their morphology was explored by optical and scanning electronic microscopy (OM and SEM). The water release profiles and the related kinetics of R1HG-3c and R1HG-4b were inspected by weight loss studies, while their stability over time was assessed both by monitoring their inversion properties to detect possible impairments of the 3D network and by chemometric-assisted ATR-FTIR spectroscopy to detect possible structural changes. The flow and dynamic rheological characterization of the gels was evaluated by determining their viscosity vs. shear rate, applying the Cross rheological equation to achieve the curves of shear stress vs. shear rate, and by performing amplitude and frequency sweep experiments. Finally, their content in NH3+ groups, known to promote the antibacterial effects, was determined by potentiometric titrations. Collectively, the favorable physicochemical characteristic of R1HG-3c and R1HG-4b, as well as the demonstrated antibacterial effects of their ingredients (3c and 4b) against multi drug resistant (MDR) staphylococci, possibly further improved by the cationic R1, support the future development of the pyrazole-enriched gels reported here as new weapons to treat severe skin and wound infections sustained by MDR bacteria of staphylococcal species.
Hydrogel Formulations of Antibacterial Pyrazoles Applying a Synthetic Polystyrene-Based Cationic Resin as Gelling Material
Silvana Alfei;Guendalina Zuccari;Gian Carlo Schito;Eleonora Russo;Carla Villa;Chiara Brullo
2023-01-01
Abstract
Aiming at developing new topical antibacterial formulations to treat staphylococcal infections, two pyrazoles (3c and 4b) previously reported for having antibacterial effects especially against staphylococci, were formulated as hydrogels (R1HG-3c and R1HG-4b). Particularly, we first synthtized and characterized a cationic polystyrene-based resin (R1). Secondly, R1 was used as gelling agent to formulate 3c and 4b and obtain R1HG-3c and R1HG-4b. Thanks to the high hydro-philicity, high-level porosity, and excellent swelling capabilities of R1, R1HG-3c and R1HG-4b were achieved with an equilibrium degree of swelling (EDS) of 765% (R1HG-3c) and 675% (R1HG-4b), as well as an equilibrium water content (EWC) of 88% and 87%, respectively. By chemometric-assisted attenuated total reflectance (ATR) Fourier transform infrared (FTIR) analyses, the chemical structure of soaked and dried gels was investigated, while their morphology was explored by optical and scanning electronic microscopy (OM and SEM). The water release profiles and the related kinetics of R1HG-3c and R1HG-4b were inspected by weight loss studies, while their stability over time was assessed both by monitoring their inversion properties to detect possible impairments of the 3D network and by chemometric-assisted ATR-FTIR spectroscopy to detect possible structural changes. The flow and dynamic rheological characterization of the gels was evaluated by determining their viscosity vs. shear rate, applying the Cross rheological equation to achieve the curves of shear stress vs. shear rate, and by performing amplitude and frequency sweep experiments. Finally, their content in NH3+ groups, known to promote the antibacterial effects, was determined by potentiometric titrations. Collectively, the favorable physicochemical characteristic of R1HG-3c and R1HG-4b, as well as the demonstrated antibacterial effects of their ingredients (3c and 4b) against multi drug resistant (MDR) staphylococci, possibly further improved by the cationic R1, support the future development of the pyrazole-enriched gels reported here as new weapons to treat severe skin and wound infections sustained by MDR bacteria of staphylococcal species.
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