RESUMO
Due to the advantages of polymer micelles and the anticancer activity of doxorubicin (DOX), the polymer micelle of DOX is expected to be used for drug delivery in anticancer applications. As a biocompatible and biodegradable polymer, amphiphilic copolymer heparosan-adipic dihydrazide-vitamin E succinate (KV) can be self-assembled to form micelles with core-shell structure in aqueous phase. In this article, KV conjugates with two different degrees of substitution (DS) were synthesized to load DOX and were characterized by 1H NMR. The size distribution, morphology, zeta potential and release behavior in vitro of the DOX-loaded micelles were studied. In vitro cytotoxicity was investigated by MTT assay against MGC80-3 and COS7 cells. The cellular uptake of the DOX-loaded micelles was observed by fluorescence microscopy and flow cytometry. The 1H NMR spectra results confirmed the KV polymers were successfully conjugated and the degree of VES grafted on heparosan polysaccharide were 12% and 25%. Briefly, the micelles with two different DS were expressed as KV12 and KV25. The DOX-loaded micelles could resist serum adsorption because of the negative charge on the surface. The average particle size measured by dynamic light scattering (DLS) method was 140-150 nm and the TEM results indicated that the morphology of DOX-loaded micelles were spherical. The encapsulation efficiency and drug loading were 80% and 10%-15%, respectively. The DOX-loaded micelles had sustained release behavior and the cumulative release of DOX/KV12 was slightly higher than DOX/KV25. Moreover, the viabilities of cells which were co-incubated with blank micelles were greater than 90%. It is clear that the blank micelles almost non-toxic to both cells. The IC50 of drug-loaded micelles against COS7 cells was much higher than that of MGC80-3 cells and the DOX/KV12 exhibited greater cytotoxicity. The cellular uptake of DOX/KV on MGC80-3 was greater than COS7 cells. In this study, KV polymer micelles have a sustained drug release activity and have a good selectivity to tumor cells, so it would be a potential carrier in drug delivery.
RESUMO
In this study, the endocytosis pathway of heparosan and its intracellular distribution were investigated in MCF-7 tumor cells and COS7 normal cells. The endocytosis inhibition and cellular probe location experiments showed that MCF-7 tumor cells took heparosan more efficiently and selectively than COS7 cells. The cellular uptake of heparosan was energy-dependent in both MCF-7 tumor cells and COS7 normal cells. Moreover, the major endocytosis pathway of heparosan into MCF-7 tumor cells was caveolin-mediated endocytosis and macropinocytosis. The internalized heparosan was mainly located in lysosomes of the cells.
RESUMO
Heparosan is the start point for chemoenzymatic synthesis of heparin and it is of great significance to efficiently synthesize heparosan in microorganisms. The effects of overexpressing key enzyme genes of the UDP-glucuronic acid (UDP-GlcUA) pathway (pgcA, gtaB and tuaD) or the UDP-N-acetyl-glucosamine (UDP-GlcNAc) pathway (glmS, glmM and glmU) on the heparosan production and molecular mass were analyzed in the constructed heparosan-producing Bacillus subtilis ((1.71±0.08) g/L). On this basis, heparosan production was increased to (2.89±0.11) g/L with the molecular mass of (75.90±1.18) kDa through co-overexpressing the tuaD, gtaB, glmU, glmM and glmS genes in shake flask cultivation. In the 3 L fed-batch fermentation, heparosan production was improved to (7.25±0.36) g/L with the molecular mass of (46.66±2.71) kDa, providing the potential for heparosan industrial production.