Enhanced Vitamin D3 Adsorption Through Novel Hydrophobic Halloysite-Alginate Biopolymer Composites

Abstract

This study presents a sustainable strategy to enhance polymer encapsulation, adsorption, and functional properties by chemically modifying sodium alginate with hydrophobic groups. Hydrophobic alginate derivatives were synthesized via a solvent-free method using hexadecyl trimethylammonium bromide, resulting in nanoparticles capable of effectively capturing non-polar compounds. To further improve compatibility within alginate-based biocomposites, halloysite nanotubes were modified through ball milling and surfactant-assisted treatments. The resulting nanocomposites (MBHA and MHHA) exhibited significantly enhanced adsorption and controlled release behavior, as confirmed by FTIR analysis of hexadecyl alginate ester conjugation. Vitamin D₃ adsorption followed the Langmuir isotherm, with high correlation coefficients (R² = 0.998 for MBHA and R² = 0.991 for MHHA), indicating monolayer adsorption on a homogenous surface. Kinetic modeling revealed that the adsorption process adhered to a pseudo-second-order model (R² = 0.9969 for MBHA and R² = 0.999 for MHHA), suggesting that chemisorption was the dominant rate-controlling mechanism. These results demonstrate the critical role of surface modification in designing nano-engineered biopolymers with superior adsorption, stability, and release profiles, offering sustainable applications in medicine, agriculture, and environmental remediation.

Keywords: alginate-based delivery systems; biopolymer nanocomposites; controlled release; encapsulation efficiency; halloysite nanotubes; polymeric nanocarriers; vitamin D3 adsorption.

Figure 1

Current popular polymers for nanocarrier fabrication.

Figure 2

Schema of modified HNTs via two approaches.

Figure 3

FTIR spectra comparing pure and modified samples, showing characteristic ester and alkyl group peaks.

Figure 4

FTIR analysis of pure and modified HNTs, showing changes in the OH-group and CH₂ vibration regions.

Figure 5

FTIR spectra of final biocomposites (MBHA, MHHA) showing the incorporation of modified halloysite and alginate components.

Figure 6

XRD patterns of modified samples and final biocomposites: (a) pure and modified HNTs; (b) MBHA and MHHA.

Figure 7

SEM images of pure and modified HNTs, and final biocomposites MBHA and MHHA, showing morphological differences.

Figure 8

Comparison of vitamin D₃ adsorption efficiency between modified and unmodified biocomposite samples.

Figure 9

Contact angle values demonstrating the increased hydrophobicity of MHHA and MBHA biocomposites after surface modification.

Figure 10

Adsorption isotherms of vitamin D₃ at varying concentrations on MBHA and MHHA biocomposites.

Figure 11

In vitro cumulative release profiles of vitamin D₃ from MBHA and MHHA composites in PBS (pH 7.4) over time. Error bars represent ± standard deviation (n = 3).