Nanoencapsulation of ascorbic acid loaded in pluronic® F127 coated by chitosan-alginate polyelectrolyte complex and application of a direct quantification method to enhance its accuracy

Abstract

Ascorbic acid (AA) is an active ingredient in numerous food, pharmaceutical, and cosmetic products. Due to its high instability and reactivity, encapsulation is a strategy to enhance its bioavailability. However, encapsulating AA is challenging, and assessing its encapsulation efficiency (EE) also poses difficulties because the indirect method typically used is inappropriate for AA, as it does not consider AA's degradation kinetics. The composite nanoparticles (NPs) were prepared by using three biocompatible polymers - pluronic® F127 (PLX), alginate (ALG), and chitosan (CS). PLX micelles loaded with six distinct AA amounts (1 to 20 mg) were coated by CS-ALG polyelectrolyte complex (PEC). SEM images indicated that NPs have an almost spherical shape, while TEM images confirm the presence of PLX micelles within the NPs. The average particle size ranged from 291 to 399 nm, with a Zeta potential exceeding 34 mV and a polydispersity index of <0.32 for AA-loaded NPs formulations. Regarding the inconsistencies in AA quantification, we applied a colorimetric method for quantifying AA directly in the NPs and for accurately quantifying AA in release studies (pH 5.5 and 7.4). CS-ALG PEC NPs showed suitable properties for short-term topical treatments, delivering AA at a constant rate over time.

Keywords: Alginate; Ascorbic acid; Chitosan; Colorimetric method; Pluronic; Polyelectrolyte complex.