Adsorption and thermal properties of the bovine serum albumin–silicon dioxide system

Abstract

The adsorption, electrokinetic, thermal and stability properties of the silicon dioxide (silica, SiO 2 )/ bovine serum albumin (BSA) system were determined. All measurements were carried out as a function of solution pH value. The highest amount of BSA absorbed on the silica surface was observed at pH 4.6 [the value close to the BSA isoelectric point (pI)], which is primarily related to the packed albumin conformation and the lack of adsorbentadsorbate electrostatic repulsion. At pH 4.6, largest mass decrease was also noticed (thermogravimetric measurements). At pH 3, 7.6 and 9, the adsorption levels were much lower. This phenomenon is associated with the electrostatic repulsion between the BSA macromolecules and the silica particles as well as the expanded BSA structure. During biopolymer adsorption, the whole solid surface is coated with the albumin macromolecules. Then, the properties of the silica particles become similar to those of the BSA macromolecules. In the presence of albumin, the silica pH iep point is identical to the BSA pI value. It should also be noted that the albumin adsorption affects the SiO 2 suspension stability. The greatest change was observed at pH 3. Under these conditions, the BSA addition causes electrosteric system stabilization.

Adsorption of bovine serum albumin on silicon dioxide nanoparticles: Impact of pH on nanoparticle–protein interactions

“…56 The measured zeta potentials are not linear. 37 This suggests that there are compounding effects. One such effect is the protonation and deprotonation of functional groups in the amino acid residues within BSA as a function of pH.…”

“…13,27 The adsorption of proteins, including BSA, on nanoparticle surfaces has been investigated in terms of impacts on nanoparticle aggregation, protein coverage, and protein structure. [27][28][29][30][31][32][33] Investigations on the effects of pH have been conducted and shown that protein adsorption is the greatest at or near the isoelectric point, [34][35][36][37] and there is not necessarily a pH-dependent trend for protein adsorption to nanoparticle surfaces away from the isoelectric point. 37 Aggarwal et al conducted a study on pure silica and zirconia nanoparticle surfaces and a mixture of nanoparticle surfaces and found that the composite surface better retains the native protein structure upon adsorption.…”

“…41,42 pH-dependent studies of proteins on nanoparticle surfaces have indicated that the isoelectric point of the protein corresponds to the greatest adsorption onto the nanoparticle surface, independent of the point of zero charge for the nanoparticle substrate. [34][35][36][37] However, other studies indicate that the isoelectric point of the substrate determines maximum protein adsorption. 48,50 Quantification of protein adsorption has been done in the past using ATR-FTIR spectroscopy in an equilibrium state; however, here we use thermogravimetric analysis (TGA) to determine the number of protein molecules which adsorb to a nanoparticle surface.…”

“…48,50 Quantification of protein adsorption has been done in the past using ATR-FTIR spectroscopy in an equilibrium state; however, here we use thermogravimetric analysis (TGA) to determine the number of protein molecules which adsorb to a nanoparticle surface. 37,40 Previous studies of BSA adsorption have focused primarily on secondary structure analysis rather than protein surface coverage. 13,31,33,51,52 In this study, we combine ATR-FTIR spectroscopy and TGA to obtain the time-and pH-dependent spectra of BSA on SiO 2 and quantify the adsorption and the structure of BSA on the surface.…”

Impact of adsorption of poly(aspartic acid) and its copolymers with polyethylene glycol on thermal characteristic of Cr2O3

“…The interactions between various polymers and the solid particles using the thermogravimetric methods are subject of numerous research [38][39][40][41][42][43][44][45][46][47][48][49][50]. Figures 7-10 present the TG, DTA and DTG curves for the chromium (III) oxide samples, both unmodified and modified with the adsorption layer formed by the analyzed homo-and copolymers.…”