<i>In Vivo</i> Biostimulatory Efficacy of Ascorbic Acid-Loaded Poly(lactic-<i>co</i>-glycolic Acid) Nanoparticles Hydrogel for Dermal Remodeling

Synthetic, biocompatible, and biodegradable polymers such as poly-l-lactic acid (PLLA) and polycaprolactone (PCL) are used in the form of microparticles (25–200 μm) dispersed in injectable hydrogels for collagen biostimulation through mechanical stimuli and subclinical inflammatory responses. However, their clinical application is limited by adverse effects, including nodule formation and vascular occlusion. As an alternative, nanoparticles based on poly(lactic-<i>co</i>-glycolic acid) (PLGA), a synthetic, biocompatible, and biodegradable copolymer, loaded with ascorbic acid (AA), a potent antioxidant with pro-collagenic activity, may provide enhanced dermal retention, reduced macrophage recognition, and minimized adverse effects. This study developed AA-loaded PLGA nanoparticles incorporated into a hydrogel and evaluated their potential for <i>in vivo</i> dermal biostimulation. Nanoparticles were prepared by nanoprecipitation and characterized by dynamic light scattering (DLS) to determine average diameter and polydispersity index (PDI), zeta potential to assess surface charge, and transmission electron microscopy (TEM) to examine morphology. AA encapsulation efficiency was assessed spectrophotometrically. Cytotoxicity was evaluated by the MTT assay using epithelial, macrophage, and fibroblast cells. The hydrogel was evaluated for stability and spreadability. The biostimulatory potential of the formulations was assessed <i>in vivo</i> by measuring hydroxyproline levels, collagen production, and dermal remodeling. The nanoparticles exhibited an average diameter below 300 nm, a moderately monodisperse distribution (PDI <0.2), spherical morphology, and high AA encapsulation efficiency (>94%). Biocompatibility was confirmed in epithelial and fibroblast cells (viability >70%), with cytotoxicity observed only in macrophages at higher concentrations (<70%). <i>In vivo</i>, AA-loaded PLGA nanoparticles (AANps) induced a 28% increase in collagen production at 30 days, although this effect declined by 60 days. Collagen fibers remained denser and more organized, suggesting ongoing tissue remodeling. Prospectively, after one month, the AANps hydrogel developed in this study could promote a more pronounced collagen increase compared to commercial products such as calcium hydroxylapatite (CaHA) microparticles and PLLA microparticles. These findings suggest that the AA-loaded PLGA nanoparticle hydrogel is a promising strategy for dermal remodeling.