| BackgroundPoly(lactic-co-glycolic acid) (PLGA) is a biodegradable, biocompatible, and non-toxic copolymer, and is frequently used in the preparation of nanoparticles (NPs) loaded with anticancer drugs. Moreover, PLGA can increase the solubility, stability and absorption of drugs.Chitosan (CHI), a biodegradable, biocompatible, and cationic polysaccharide, is produced by deacetylation of chitin. It is considered as an ideal surface modifier for PLGA NPs.7-Ethyl-10-hydroxycamptothecin (SN-38) is an active metabolite of irinotecan. The cytotoxicity activity on cancer cells of SN-38 is almost 1000-fold more potent than irinotecan in vitro. However, the oral bioavailability of SN-38 is extremely low, due to its poor water-solubility and low intestinal permeation.AimTo investigate the potential application of CHI modified PLGA NPs (CHI/PLGA NPs) for improving the oral absorption of SN-38, SN-38 loaded CHI/PLGA NPs (CHI/PLGA/SN-38 NPs) were prepared, and both the physicochemical characteristics and in vitro release profile of NPs were investigated. Furthermore, the potential of the novel delivery system was evaluated in vitro and in vivo. Finally, the mechanism for the improvement of drug absorption was explored.Methods1. CHI/PLGA/SN-38 NPs were prepared according to oil-in-water (O/W) emulsion solvent evaporation method. CHI was absorbed onto the surface of PLGA NPs through electrostatic interaction. The particle size and Zeta potential were measured by Zetasizer nano analyser. The surface morphology of NPs was observed using a scanning electron microscope. Differential scanning calorimetry (DSC), X-ray powder diffractometry (XRD), and Fourier transform infrared (FTIR) spectra were applied to examine the physicochemical structures of NPs. UV-vis spectrophotometer was used to evaluate the encapsulation efficiency, drug loading content, and in vitro drug release of the NPs.2. In situ single-pass intestinal perfusion (SPIP) in rats was applied in exploring the the effects and mechanisms on CHI/PLGA NPs improving oral absorption of SN-38 at the animal level.3. Drug accumulation, uptake, efflux, and cytotoxicity investigations on Caco-2 cells were used to explore effects and mechanisms on CHI/PLGA NPs improving oral absorption of SN-38 at the cellular and molecular levels.Results1. CHI/PLGA/SN-38 NPs were spherical-shaped with smooth surface and exhibited an average size of 209 nm. After CHI was coated onto the surface of PLGA, the Zeta potential of the NPs was reversed to positive. DSC, XRD, and FTIR results showed that SN-38 was successfully entrapped into PLGA NPs coated with CHI. The encapsulation efficiency and drug loading content were 71.83% and 6.79%, respectively. In vitro release studies displayed markedly inhibited drug release in the simulated gastric condition as compared with that in the intestinal condition.2. SPIP studies indicated a dramatic improvement of drug absorption as a result of the synergistic effect between CHI and PLGA on P-glycoprotein (P-gp) inhibition.3. CHI/PLGA NPs showed high cellular uptake and low efflux for drugs in Caco-2 cells. The cytotoxicity studies revealed that CHI/PLGA NPs had a transient effect on the membrane integrity, but did not have an influence on cell viability. CHI/PLGA NPs were mainly internalized in the form of intact NPs, thus escaping the recognition of enterocyte P-gp and avoiding efflux into the apical part of the enterocytes. After partial release of drugs inside the enterocytes, CHI/PLGA interfered with the microenvironment of P-gp and further weakened the P-gp-mediated efflux.ConclusionCHI/PLGA NPs could improve the oral absorption of SN-38 via P-gp inhibition. The present study might provide a new insight into the design of novel nano drug delivery system that those pharmacological inactive excipients can serve as P-gp modulators to enhance the absorption of P-gp substrate drugs instead of traditional active compounds. |
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