STRUCTURAL CHARACTERIZATION OF KOJIC ACID IN POLYMER-PROTEIN-BASED HYDROGELS

The use of traditional treatments for inflammatory dermatoses is being replaced by innovative treatments using bioactives due to better biocompatibility and fewer adverse effects. In this context, kojic acid (KA) has demonstrated therapeutic potential due its anti-inflammatory properties. However, because of the high instability of this molecule, the use of nanostructures for its protection has become an interesting strategy. Moreover, the application of chitosan (CS) and sericin (SER) to deliver KA in pharmaceutical formulations for the treatment of dermatitis is advantageous. The polymer-protein-based hydrogels were formulated using 1% KA, 3% CS and three different concentrations of SER (1.5%, 3% and 6%). The analysis of the formulations by Fourier Transform Infrared Spectroscopy with Attenuated Total Reflectance (FTIR-ATR) allowed the identification of functional groups through the peaks observed in the range of 4000 and 700 cm⁻¹. Release profiles were obtained across cellulose acetate membranes (MWCO 15 kDa). FTIR patterns showed shifts of the bands of SER (-NH₂ at 1635 cm⁻¹ and 1520 cm⁻¹), CS (C-O at 1149 cm⁻¹), and C=O stretching at 1602 cm⁻¹ and C-O-C stretching at 1218 cm⁻¹ for KA, indicating the interaction between the hydrogels components and indirectly confirming that KA is involved in the hydrogels structuring. KA release data were best fitted to the Korsmeyer-Peppas model with Krel = 0.41 ± 0.03 h^-n, 0.380 ± 0.008 h^-n, and 0.372 ± 0.007 h^-n for 1.5% SER, 3% SER, and 6% SER, respectively, indicating that KA release from the polymer network is determined by Fickian diffusion. Furthermore, the influence of SER concentration on KA release parameters was noted, since different release constant values were observed for 1.5%, 3 % SER, and 6% SER. FTIR-ATR confirmed the strong interaction between the biopolymers and the bioactive, a fact observed by the changes in the bands among the different formulations. The in vitro release tests also corroborate these analyses, showing a decrease in the diffusion speed of KA as the concentration of SER increased, which shows a strong interaction between SER and KA.

This work was supported by Conselho Nac. Des. Cient. Tecnológico (CNPq #308819/2022-5) and by Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP #2022/04173-6).