ABSTRACT
Placenta, an important organ, mediates the exchange of nutrients and metabolites between mother and fetus. The transporters, including ATP-binding cassette (ABC) transporters and solute carrier (SLC), expressed in the syncytiotrophoblast play a vital role in substance exchange. Some transporters, such as organic cation transporters (OCTs) and organic anion transporters (OATs), mediate the uptake of endogenous substances and drugs. Some transporters, such as P-glycoprotein (P-gp), breast cancer resistance protein (BCRP) and multidrug resistance-associated proteins (MRPs), can excrete their substrates from the syncytiotrophoblast to the maternal circulation. However, the expression and activity of these transporters are not uniform throughout the gestation period, since they can be affected by physiological and pathological changes during pregnancy or drugs. Thus, an understanding of the role of placental transporters and the variation in their expression and activity in response to physiological and pathological changes is essential for efficient and safe therapy during pregnancy, and it also has important value in the development of drug treatment in pregnancy.
ABSTRACT
<p><b>AIM</b>To elevate the encapsulation efficiency, decrease the burst release and improve the release of protein entrapped in poly (lactic-co-glycolic acid) (PLGA) microspheres. The bovine serum albumin (BSA) composite microspheres of alginate-chitosan-PLGA were prepared and the release characteristics of BSA from this composite microspheres were studied.</p><p><b>METHODS</b>The much smaller calcium alginate microcapsules were first prepared by a modified emulsification method in an isopropyl alcohol-washed way and coated with chitosan, then the alginate-chitosan microcapsules were further entrapped in PLGA to form the composite microspheres. The protein concentration was determined using a BCA protein assay kit. The release profiles were changed with various formulation factors.</p><p><b>RESULTS</b>The average diameter of the composite microcapsules was about 30 microm. Comparing with 60% to 70% of the conventional PLGA microspheres, the average encapsulation efficiency was more than 80%, and the burst releases in phosphate buffer solution of the composite microspheres decreased from 40% and 50% to 25% and further to 5% in saline solution.</p><p><b>CONCLUSION</b>The novel composite microspheres were prepared, the drug encapsulation efficiency increased and the burst release decreased. The desired release profiles could be obtained by regulating the ratios of PLG and PLA in the composite microspheres.</p>