*Article* **Grafted Microparticles Based on Glycidyl Methacrylate, Hydroxyethyl Methacrylate and Sodium Hyaluronate: Synthesis, Characterization, Adsorption and Release Studies of Metronidazole**

**Aurica Ionela Gugoasa <sup>1</sup> , Stefania Racovita <sup>2</sup> , Silvia Vasiliu <sup>2</sup> and Marcel Popa 1,3,\***

	- <sup>3</sup> Academy of Romanian Scientists, Splaiul Independentei Street No. 54, 050085 Bucharest, Romania

**Citation:** Gugoasa, A.I.; Racovita, S.; Vasiliu, S.; Popa, M. Grafted Microparticles Based on Glycidyl Methacrylate, Hydroxyethyl Methacrylate and Sodium Hyaluronate: Synthesis, Characterization, Adsorption and Release Studies of Metronidazole. *Polymers* **2022**, *14*, 4151. https:// doi.org/10.3390/polym14194151

Academic Editors: Lorenzo Antonio Picos Corrales, Angel Licea-Claverie and Grégorio Crini

Received: 27 August 2022 Accepted: 25 September 2022 Published: 3 October 2022

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**Abstract:** Three types of precursor microparticles based on glycidyl methacrylate, hydroxyethyl methacrylate and one of the following three crosslinking agents (mono-, di- or triethylene glycol dimethacrylate) were prepared using the suspension polymerization technique. The precursor microparticles were subsequently used to obtain three types of hybrid microparticles. Their synthesis took place by grafting sodium hyaluronate, in a basic medium, to the epoxy groups located on the surface of the precursor microparticles. Both types of the microparticles were characterized by: FTIR spectroscopy, epoxy groups content, thermogravimetric analysis, dimensional analysis, grafting degree of sodium hyaluronate, SEM and AFM analyses, and specific parameters of porous structures (specific surface area, pore volume, porosity). The results showed that the hybrid microparticles present higher specific surface areas, higher swelling capacities as well as higher adsorption capacities of antimicrobial drugs (metronidazole). To examine the interactions between metronidazole and the precursor/hybrid microparticles the adsorption equilibrium, kinetic and thermodynamic studies were carried out. Thus, it was determined the performance of the polymer systems in order to select a polymer–drug system with a high efficiency. The release kinetics reflect that the release mechanism of metronidazole in the case of hybrid microparticles is a complex mechanism characteristic of anomalous or non-Fickian diffusion.

**Keywords:** grafted microparticles; sodium hyaluronate; crosslinked microparticles; metronidazole adsorption; adsorption isotherm; adsorption kinetics; metronidazole release
