Effects of degree of substitution on stearic acid-modified Bletilla striata polysaccharides nanoparticles and interactions between nanoparticles and bovine serum albumin

Three kinds of stearic acid (SA)-modified Bletilla striata polysaccharides (BSPs-SA) conjugates with different degrees of substitution (DS) values of SA moiety were synthesized. The impacts of the DS values on the properties of BSPs-SA self-aggregated nanoparticles were determined. The interactions between bovine serum albumin (BSA) and the BSPs-SA nanoparticles were characterized using spectroscopic observations. The cytotoxicity was measured through 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) method. The critical aggregation concentration and the average particle sizes reduced from 16.81 μg/mL to 3.09 μg/mL and 192.70 nm to 125.29 nm when the DS values of SA segment increased from 4.98% to 12.94%, respectively. The cumulative release percentage of docetaxel in BSPs-SA nanoparticles decreased whereas encapsulation efficiency and loading capacity increased along with the DS increase of SA moiety. The fluorescence and ultraviolet results demonstrated that the conformation of BSA did not show significant change after incubating with BSPs-SA nanoparticles. Besides, the mass ratio of BSA/BSPs-SA affected their affinity intensity. The inhibition capability of cell proliferation of docetaxel-loaded BSPs-SA nanoparticles against 4T1 was superior to that of Duopafei^®. BSPs-SA nanoparticles may become a promising nanocarrier for anticancer drugs by adjusting the DS values of the hydrophobic SA groups.