# Biopolymer Casein–Pullulan Coating of Fe3O4 Nanocomposites for Xanthohumol Encapsulation and Delivery

## TL;DR

This study creates a biopolymer-coated magnetic nanoparticle system to improve the stability and controlled release of xanthohumol, a potential drug for theranostic applications.

## Contribution

A novel casein–pullulan hybrid coating is developed for Fe3O4 nanoparticles to enhance colloidal stability and enable xanthohumol encapsulation.

## Key findings

- Uncoated Fe3O4 nanoparticles showed poor stability with large sizes and high polydispersity.
- The optimal biopolymer coating reduced particle size and improved zeta potential for better colloidal stability.
- Xanthohumol was effectively encapsulated with sustained release over 120 hours following Fickian diffusion.

## Abstract

Introduction: Magnetic nanoparticles are widely investigated as multifunctional platforms for drug delivery and theranostic applications, yet their biomedical implementation is hindered by aggregation, limited colloidal stability, and insufficient biocompatibility. Hybrid biopolymer coatings can mitigate these issues while supporting drug incorporation. Aim: This study aimed to develop casein–pullulan-coated Fe3O4 nanocomposites loaded with xanthohumol, enhancing stability and enabling controlled release for potential theranostic use. Methods: Fe3O4 nanoparticles were synthesized through co-precipitation and incorporated into a casein–pullulan matrix formed via polymer complexation and glutaraldehyde crosslinking. A 32 full factorial design evaluated the influence of casein:pullulan ratio and crosslinker concentration on physicochemical performance. Nanocomposites were characterized for size, zeta potential, morphology, composition, and stability, while drug loading, encapsulation efficiency, and release profiles were determined spectrophotometrically. Molecular docking was performed to examine casein–pullulan interactions. Results: Uncoated Fe3O4 nanoparticles aggregated extensively, displaying mean sizes of ~292 nm, zeta potential of +80.95 mV and high polydispersity (PDI above 0.2). Incorporation into the biopolymer matrix improved colloidal stability, yielding particles of ~185 nm with zeta potentials near –35 mV. TEM and SEM confirmed spherical morphology and uniform magnetic core incorporation. The optimal formulation, consisting of a 1:1 casein:pullulan ratio with 1% glutaraldehyde, achieved 5.7% drug loading, 68% encapsulation efficiency, and sustained release of xanthohumol up to 84% over 120 h, fitting Fickian diffusion (Korsmeyer–Peppas R2 = 0.9877, n = 0.43). Conclusions: Casein–pullulan hybrid coatings significantly enhance Fe3O4 nanoparticle stability and enable controlled release of xanthohumol, presenting a promising platform for future targeted drug delivery and theranostic applications.