Construction Of Environment-responsive Lipid Nanocarriers And Applications In The Treatment Of Tumor And Inflammation

As the nanocarriers that have been widely concerned for more than a decade,lipid nanoparticles play an important role in targeted delivery of chemotherapy and gene therapy of tumor.Lipid nanoparticles have a long-acting,slow-release effect,and the drug release of lipid nanoparticles has the characteristics of biphasic release,rapid release in early stage and slow release in later stage,and slow release at the target site may affect the drug efficacy.While maintaining the stability in the systemic circulation,the environment-responsive drug delivery system can specifically respond to endogenous or exogenous stimuli such as physics,chemistry,biology,etc.,and can also achieve responsive drug delivery at the target site to improve efficacy and reduce side effects.However,the drug delivery systems currently modified by these means are mainly polymer micelles with controllable structure.Since lipids are basically natural components with few modifiable structures,there are few reports on environment-responsive lipid nanoparticles.In this paper,environment-responsive lipid nanoparticles were designed for tumor therapy,and based on which modification was performed to design another environment-responsive lipid nanoparticles for inflammation treatment.The contents are as follows:First,disulfide bonds-contained dithiodipropionic acid(DTPA)was used to covalently link quercetin(Qu)and P-glycoprotein(P-gp)inhibitory glyceryl caprylate-caprate(Gcc)to obtain Qu-SS-Gcc lipid nanoparticles(Qu-SS-Gcc LNPs),and designed a lipid nanoparticles drug delivery system with redox-sensitive and P-gp inhibitory characters.Qu-SS-Gcc LNPs had the particle size of about 87.8 nm.Paclitaxel(PTX)was used as the model drug to prepare PTX-loaded Qu-SS-Gcc LNPs(PTX/Qu-SS-Gcc LNPs).The drug loading and encapsulation efficiency of PTX/Qu-SS-Gcc LNPs were 8.6%and 93.5%,respectively.The results of in vitro drug release and fluorescence resonance energy transfer(FRET)ratio under different reducing conditions indicated that PTX/Qu-SS-Gcc LNPs could achieve rapid and complete drug release only under 10 mM GSH.The presence of Qu was also detected by differential scanning calorimetry,reflecting the redox-responsive character of Qu-SS-Gcc LNPs.Normal liver cells(L-02)and murine breast cancer cells(4T1)were used as normal and tumor cell models,respectively.FRET results showed that PTX/Qu-SS-Gcc LNPs could respond to high concentrations of reducing substances in tumor cells,nanocarriers cleaved rapidly and released the entrapped drug,meanwhile Qu generated by cleavage inhibited P-gp by binding to P-gp sites,which reduced drug efflux and had excellent proliferation inhibition effect to tumor cell.However,PTX/Qu-SS-Gcc LNPs did not suffer large-scale cleavage in normal cells,and had low toxicity to normal cells.In situ 4T1 tumor mice were used as animal model.In vivo imaging technique showed that Qu-SS-Gcc LNPs were mainly distributed in the tumor,liver and spleen after intravenous injection.The pharmacodynamics of mice showed that PTX/Qu-SS-Gcc LNPs had better anti-tumor effect compared with Taxo(?)and nonredox-sensitive PTX-loaded monostearin solid lipid nanoparticles,the tumor inhibition rate could reach 73.1%and the biosafety was high.Further studies were carried out to utilize the esterase-sensitive character of the ester bonds of DTPA covalently-linked Qu and Gcc in Qu-SS-Gcc LNPs,and chitosan(CSO)was modified on the surface to design an environment-responsive drug delivery system with colon-targeting property.Dexamethasone(Dex)was used as model drug to obtain CSO-modified Dex-loaded Qu-SS-Gcc LNPs(CSO/Dex/LNPs)for the treatment of ulcerative colitis.The encapsulation efficiency and drug loading of CSO/Dex/LNPs were 93.1%and 8.1%,respectively,as determined by high performance liquid chromatography.In vitro release results showed that both Dex/LNPs and CSO/Dex/LNPs had esterase-responsive property,which could release drug rapidly in esterase-containing simulated intestinal fluid.The human colorectal adenocarcinoma cell(Caco-2)monolayer was used as the intestinal cell barrier model.Transmembrane resistance measurement and permeation results showed that Dex/LNPs had a protective effect to lipopolysaccharide(LPS)-stimulated Caco-2 cell monolayer and could increase the expression of E-cadherin in LPS-stimulated Caco-2 cells.The anti-inflammatory effect of Dex/LNPs on LPS-stimulated mouse leukemia cells of monocyte macrophage cells(Raw 264.7)were investigated by enzyme-linked immunosorbent assay(ELISA)and Griess assay.The results showed that Dex/LNPs could reduce the expression of TNF-?,IL-6 and NO significantly in LPS-stimulated Raw 264.7 cells.C57BL/6 mice were used to construct the colitis mouse model.The in vivo distribution results showed that CSO/LNPs had colon-targeting property and had strong retention ability in the colon of colitis mice.The anti-inflammatory effect of CSO/Dex/LNPs in colitis mice showed that CSO/Dex/LNPs had better anti-inflammatory effect than Dex,which could reduce colonic atrophy and histomorphological change,increase the expression of E-cadherin in colon.Meanwhile the expression of TNF-?,IL-6 and NO in CSO/Dex/LNPs-treated mice were 37.4%,35.5%and 33.2%,respectively,compared to that in only DSS-treated mice.The redox-sensitive and P-gp-inhibitory lipid nanoparticles drug delivery system constructed in this study and CSO modified colon-targeting esterase-sensitive lipid nanoparticles drug delivery system can achieve rapid drug release in tumor or colonic inflammation sites,respectively,which provide new strategies and new ideas for the construction and application of environment-responsive lipid nanocarriers.