Highly Stable and Fine-Textured Hybrid Microspheres for Entrapment of Cosmetic Active Ingredients

Abstract

This study details the preparation and application of supramolecular host-guest inclusion complexes entrapping biomineralized microspheres for long-term storage and their pH-responsive behavior. The microspheres were assembled using a CaCO₃ synthesis process coupled with cyclodextrin-tetrahydrocurcumin (CD-THC) inclusion complexes, forming fine-textured and mechanically stable hybrid materials. The products were successfully characterized using field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), and particle size analysis (PSA). Various parameters such as the Brunauer-Emmett-Teller (BET) surface area, single point total pore volume, and pore size via adsorption/desorption analysis were also determined. The obtained THC-entrapped hybrid microspheres contained as high as 20 wt % THC loading and were very stable, preserving 90% of the initial concentration over four weeks of storage at different temperatures, largely limiting THC leaching and indicating high stability in a physiological environment. In addition, the pH-responsive release of THC from the hybrid microspheres was observed, showing potential use for application to weakly acidic skin surfaces. To our knowledge, this is the first demonstration of antiaging cosmetic formulation technology using biomineralization based on the co-synthesis of CaCO₃ and CD-THC complexes.

Figure 1

Schematic illustrations of the CD–THC inclusion complex preparation (A) and the entrapping of the CD–THC inclusion complexes in hybrid microspheres (B). The CD–THC inclusion complex was prepared by vigorous stirring, leading to nanosized materials, which were then entrapped via the co-synthesis method during CaCO₃ crystallization.

Figure 2

(A) SEM images, (B) energy-dispersive X-ray spectroscopy (EDS), and (C) particle size distribution of the hybrid microspheres.

Figure 3

(A) FT-IR spectrum (B) XRD patterns, and (C) N₂ adsorption–desorption curve of the prepared hybrid microspheres.

Figure 4

(A) Cumulative release of THC and GL from the hybrid microsphere suspensions in PBS buffers at pH 7.4; (B) cumulative release behavior of THC from the hybrid microsphere suspensions at pH 7.4 and 5.5 at RT; and (C) stabilities of the hybrid microspheres at different temperatures (4, 25, and 45 °C, as well as cycling). The stability was defined as the ratio of the residual concentration at each time point to the initial concentration of each sample. All samples were measured thrice for standard deviation. The standard deviation is represented by error bars in the figure.