Green Selective Oxidized Microcrystalline Cellulose and Its Use in Encapsulation of Lavender Essential Oils

Abstract

Microcrystalline cellulose (MCC) has emerged as a promising bio-based material due to its abundance, degradability, and biocompatibility. This study focuses on the chemical modification of MCC to enhance its amphiphilicity and use to encapsulate lavender essential oil (LO) for cosmetic applications. MCC was selectively oxidized by a green process using 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) and ozone co-oxidants. The reaction mechanisms and the chemical structures of the oxidized MCC products were examined by iodometric titration, UV-Vis, and FTIR spectroscopy. The degree of oxidation (DO), i.e., the conversion of  -OH to -COOH/-COO- groups, is dependent on the reaction time and acid concentration, in which a suitable sample with optimum carboxylate content was obtained using 0.1 M H₂SO₄ and 2-hour ozonation time. The resulting amphiphilic MCC was employed to encapsulate LO in an ethanol/water medium. The effect of the ethanol/water ratio on the stability and encapsulation efficiency of LO-loaded MCC (LO@MCC) was studied. Zeta potential measurement, SEM, and FTIR spectroscopy were used to confirm the encapsulation and morphology of the materials. An appropriate ethanol/water ratio (60/40) led to a high encapsulation efficiency (EE%) and high loading capacity (LC%) of 79.1 and 30.8 %. The results confirm that in the oxidation process, MCC molecules were oxidized, converting hydroxyl groups to carboxylates. Chain scission also occurred, leading to soluble small-sized MCC, while most remained insoluble fragments with high surface charges, forming stable dispersing particles. In the LO encapsulation process, the soluble MCC acts as a surfactant and shell structure, forming LO-encapsulated droplets deposited on the dispersing MCC particles. The materials have a high potential for use in cosmetic applications.

Keywords: Microcrystalline cellulose, Encapsulation, Lavender oil, TEMPO, Selective oxidation