Characterisation of bovine serum albumin–fucoidan conjugates prepared via the Maillard reaction

Bovine serum albumin (BSA)–fucoidan conjugates were prepared by the Maillard reaction (60 °C and 79% relative humidity for 96 h), and were then identified by sodium dodecyl sulphate–polyacrylamide gel electrophoresis (SDS–PAGE) and size-exclusion chromatography (SEC). Molecular characteristics of the BSA–fucoidan conjugates were investigated, using atomic force microscopy (AFM), dynamic light scattering (DLS), fluorescence spectroscopy, and circular dichroism spectroscopy. SDS–PAGE patterns provided evidence for the covalent bonding between BSA and fucoidan. SEC profiles showed that about 1.5–2.0 mol of fucoidan were covalently linked to 1 mol of BSA, resulting in high-molecular-weight compositions (conjugates). AFM images and DLS results indicated that most particles in the conjugates were nano-structured and more spherical than those of a regular BSA–fucoidan mixture. The fluorescence intensity and maximum emission wavelength of the conjugates together revealed that the BSA molecules had converted from an ordered conformation into a partially folded molten globule state.