Recombinant human serum albuminfrom OsrHSA (Wuhan Healthgen)

Polyhydroxystearic acid (PHSA) is widely used as an oil-soluble dispersant for metal oxide particles in cosmetics. PHSA is essentially polydisperse. In this study, we investigated the size-dependent adsorption of PHSA oligomers to titanium dioxide nanoparticles (TiO₂NPs) by gel permeation chromatography. In dispersions with a medium of diethyl sebacate, a good solvent for PHSA, the total adsorbed mass of PHSA increased and became saturated as the PHSA concentration increased. Above the saturation point of the adsorbed mass, small PHSA oligomers increasingly adsorbed with increasing PHSA concentration, while the adsorption of large oligomers decreased. This can be explained by the entropic penalty related to the conformational constraint in the adsorbed layer and the advantage of the total gain of the PHSA-TiO₂NP interaction for the adsorption of small PHSA oligomers. In contrast, the addition of cyclic silicones, acting as poor solvents for PHSA, to the above dispersions resulted in enhanced adsorption of large PHSA oligomers, while there was no change in the adsorption of small oligomers. The enhanced adsorption of large oligomers was more apparent when cyclic silicones were added to the dispersions with high PHSA concentrations. We propose that cyclic silicones are not favorable for large PHSA oligomers and the poor solvency of the mixed solvent causes shrinking of the adsorbed PHSA oligomers on the TiO₂NPs, which generates additional space for adsorption. The effect of the ring size of the cyclic silicone was also systematically investigated.

To solve the large size faultiness of Oryza sativa recombinant human serum albumin nanoparticle (OsrHSA NP), the structural discrepancies between OsrHSA and plasma-derived human serum albumin (pdHSA) were analyzed deeply in this research. It demonstrated that there were some subtle structural discrepancies located in subdomain IA and IIA between OsrHSA and pdHSA, which included peptide backbone, disulphide bridge and some amino acids. Firstly, the structural discrepancies were investigated through literature comparison, it inferred that the structural discrepancies resulted from the fatty acid (FA) binding to OsrHSA at site 2 of subdomain IA and IIA. To form a cavity for accommodation of FA molecule in OsrHSA, the peptide backbone structure of subdomain IA and IIA would change, accompanied by the conformational transition of disulphide bridges and side chain structure change of some amino acids in subdomain IA and IIA. These alterations induced the exposure of tryptophan (Trp) and tyrosine (Tyr) residues in subdomain IA and IIA and the decrease of net negative charges of molecular surface. The former would promote more OsrHSA molecules aggregate, and the latter would weaken the electrostatic repulsion. As a result, the size of OsrHSA NP was more extensive than that of pdHSA NP (175.84 ± 15.63 nm vs. 31.67 ± 1.31 nm) when the concentration of Dimethyl Sulphoxide (DMSO) was 30% (v/v). In this study, the experimental scheme of OsrHSA NP preparation was improved. There were two changes in the enhanced preparation scheme: pH 8.2 PBS buffer and 63% DMSO. It indicated that the improved OsrHSA NP carrier was comparable to the pdHSA NP carrier. The size and drug loading of paclitaxel-loaded improved OsrHSA NP were 53.57 ± 3.63 nm and 7.25 ± 0.46% (w/w), and those of docetaxel-loaded improved OsrHSA NP were 44.75 ± 2.26 nm and 8.43 ± 0.74% (w/w). Moreover, both NPs exhibited good stability for 168 h at 7.4 pH values. It is established that the improved OsrHSA NP is comparable to the pdHSA NP as a taxane delivery system.