Valorization of Sugarcane By-Products through Synthesis of Biogenic Amorphous Silica Microspheres for Sustainable Cosmetics

Abstract

Ashes from sugarcane by-product incineration were used to synthesize silica powders through alkaline hot extraction, followed by ethanol/acid precipitation or the sol–gel method. Both production methods allowed amorphous spherical silica microparticles with sizes ranging from 1–15 μm and 97% purity to be obtained. Water absorption ranged from 135–155 mL/100 g and 150–250 mL/100 g for precipitated silica and silica gel, respectively, while oil absorption ranged from 305 to 390 and from 250 to 350 mL/100 g. The precipitation with ethanol allowed the recovery of 178 g silica/kg ash, with a lab process cost of EUR 28.95/kg, while the sol-gel process showed a yield of 198 g silica/kg ash with a cost of EUR 10.89/kg. The experimental data suggest that ash from sugarcane by-products is a promising source to be converted into a competitive value-added product, minimizing the environmental impact of disposal problems.

Silica Microparticles from Sugarcane By-Products as an Encapsulation System for Retinoids Aimed at Topical Sustained Release

“…Regarding the particle size, the different formulations yielded microparticles with average sizes ranging from 4.8 to 10.4 μm ( Table 2 ), which are slightly larger values than the average diameters of empty silica microparticles, ca. 3.9 μm [ 21 ].…”

“…Finally, at 720 cm −1 , the stretching of aliphatic ether compounds and the C=C bending of alkene were disubstituted (cis). The spectra for silica microparticles mainly present a large band between 1240–1040 cm −1 , which represents the asymmetric stretching vibrations of siloxane covalent bonds [ 21 ]. The spectra for retinol-loaded silica microparticles are mainly composed of the 1240–1040 cm −1 band of silica, and some peaks that are also present in retinol, such as 2925–2850 cm −1 and 1740 cm −1 .…”

“…Additionally, the potential for irritation and dryness associated with retinol use may exacerbate existing skin conditions, making it crucial for individuals to use retinol products judiciously. While amorphous silica is documented as “Generally Recognized As Safe” (GRAS) by the FDA and has found extensive use in cosmetics as well as being a food additive, it is important to note that data gathered from in vitro toxicity and compatibility assessments are subject to variation based on factors such as cell type, particle size and shape, and potential contaminants [ 21 ]. The encapsulation of retinol into silica particles not only shields retinol from external factors that can degrade its stability but also controls its release, reducing the risk of irritation and toxicity [ 24 ].…”

“…Silica microspheres were produced from sugarcane bagasse ashes, according to Costa et al, with slight modifications [ 21 ]. Briefly, nickel-plated stainless steel crucibles were used to mix ash and sodium hydroxide and placed into a muffle oven at 350 °C for 20 min.…”

“…Incorporation of retinoids in topical delivery systems may enhance their stability and bioavailability, through protection from light, temperature, and oxygen, and may also reduce some potential side effects, such as skin irritation, through the controlled release of retinol [ 17 ]. Recently, our research group has developed silica particles from sugarcane ash as a sustainable source [ 21 ]. Thus, we propose using biogenic silica extracted from sugarcane bagasse ash to produce biocompatible encapsulation systems for retinoids, increasing their stability and skin activity.…”