Analysis of the physicochemical properties of polylactic acid‑based preparations used for injection

Abstract

This study aimed to determine the basic physicochemical properties (viscosity, pH, particle size, distribution, and stability) of a formulation based on polylactic acid (PDLLA – 42.5 mg) and sodium hyaluronate (HA ‑ 7.5 mg) and a formulation based on polylactic acid (PDLLA – 170 mg) and sodium hyaluronate (HA – 30 mg). The following objectives were addressed: determining the viscosity and pH of the formulation solutions at control points of 30 minutes, 12 hours, and 24 hours; determining the particle size, distribution, and stability; and the presence of BDDE. The viscosity results of the formulation solutions at control points of 12 and 24 hours were similar for both formulations. At the 30‑minute post‑dilution checkpoint, the viscosity differed. This may be due to the biodegradation of hyaluronic acid in PDLLA‑170 mg, as its content differs in the two solutions. The pH of the PDLLA‑42.5 mg solutions at the 30‑minute, 12‑hour, and 24‑hour checkpoints showed a slight decrease, while that of the PDLLA‑170 mg solution remained virtually unchanged throughout the experiment. Furthermore, the changes in pH for both solutions can be considered insignificant. The particle size of the PDLLA‑42.5 mg solutions after dehydration ranged from 20 µm to 40 µm, while that of the PDLLA‑170 mg solutions ranged from 40 µm to 80 µm. Particle distribution and stability parameters for PDLLA‑42.5 mg solutions showed minor changes over time, while for particles from PDLLA‑170 mg solutions, these parameters remained virtually unchanged over the course of the experiment. For both solutions, these parameters remained within normal limits. The presence of BDDE in both PDLLA solutions was not confirmed.