Enhancement of the Interaction between Bovine Serum Albumin and Quercetin by Quaternary Ammonium Chitosan: Multispectroscopic Insights into Photophysics, Bioaccessibility, and Bioactivity.

Quercetin (Que)-encapsulated bovine serum albumin (BSA) nanoparticles incorporated with quaternary ammonium chitosan (HACC) were prepared successfully. The nanoparticles were characterized by Fourier transform infrared (FT-IR) spectroscopy, and their morphology was examined using scanning electron microscopy (SEM). Dynamic light scattering (DLS) analysis showed that the Que-BSA-HACC nanoparticles ranged in size from 233 to 276 nm with an encapsulation efficiency of up to 62%. The effects of HACC on the interaction between BSA and Que were investigated by using multispectroscopic techniques. The introduction of HACC increased the binding constant of the complex, indicating an enhanced binding affinity. The Que-BSA-HACC interaction was predominantly driven by hydrophobic and electrostatic interactions. Moreover, the nanoparticles exhibited an enhanced quercetin release under simulated gastrointestinal conditions. The nanoparticles also exhibited enhanced antioxidant and anti-inflammatory activities compared to free Que, which was attributed to improved aqueous dispersibility. In contrast, cytotoxicity studies against SW-620 cells revealed that blank BSA-HACC nanoparticles exhibited comparable antiproliferative effects, suggesting that the carrier matrix plays a major role in the observed activity. These findings contribute to the development of novel flavonoid-based delivery systems.