pH-INDUCED STRUCTURAL TRANSITIONS IN BSA HARD CORONA ON GOLD NANOPARTICLES MODULATE CURCUMIN LOADING AND RELEASE BEHAVIOR

M.P. SAMANT, V. JAISWAL, GAURI RAUT, P.M. DONGRE^#

https://www.doi.org/10.59277/RJB.2026.2.01

*Department of Biophysics, University of Mumbai, Mumbai, India

The protein – nanoparticle corona structure directly determines nanoparticle

stability, cellular uptake, and therapeutic outcome in biological media. In this study, we prepared a

bovine serum albumin-gold nanoparticle hard corona (BSA-GNP HC) to examine the effects of pH

on colloidal stability and curcumin binding. Dynamic light scattering and zeta potential

measurements showed pH-dependent behavior governed by protein protonation at the nanoparticle

surface. The corona remained stable at pH 7,6, and 2, with zeta potentials of –12.3 mV (pH 7) and

+10.5 mV (pH 2), and a hydrodynamic diameter of about ~42 nm. At pH 4, near the BSA isoelectric

point, the zeta potential was nearly zero (–1.04 mV), which produced strong aggregation and a

particle size of ~846 nm; at pH 5, the size was about 69 nm, indicating partial destabilization.

UV-Visible and fluorescence spectroscopy confirmed reversible structural changes between

dispersed and aggregated states. Curcumin binding, quantified by fluorescence quenching, was

measurable at pH 7 and 6, higher at pH 2, and not detectable at pH 4, where aggregation likely

blocked binding sites. These data show that the BSA-GNP HC operates as a reversible

supramolecular assembly controlled by protonation-dependent surface charge, suitable for

pH-sensitive drug delivery in acidic environments.

Key words: Gold nanoparticles, protein corona, bovine serum albumin, hard corona, pH-responsive behavior, curcumin binding, drug delivery

Corresponding author’ e-mail: drpmdongre@yahoo.co.in