Novel Nanogel Enhances Mucoadhesion And Penetrability Of 10-hydroxycamptothecin In Orthotopic Bladder Cancer

Objective: A reduction-sensitive polypeptide nanogel was synthesized.The solution properties,HCPT release profiles,cell internalization,cytotoxicity and apoptosis in vitro,and mucoadhesiveness,penetrability,tissue distribution,antitumor efficacy,and systemic toxicity in vivo of NG/HCPT were systematically investigated.Methods: A positively charged disulfide-core-crosslinked polypeptide nanogel of poly(L-lysine)–poly(L-phenylalanine-co-L-cystine)(PLL–P(LP-co-LC))was developed to deliver 10-hydroxycamptothecin(HCPT).The loading nanogel was noted as NG/HCPT.The solution properties,HCPT release profiles,cell internalization,cytotoxicity and apoptosis in vitro,and mucoadhesiveness,penetrability tissue distribution,antitumor efficacy,and systemic toxicity in vivo of NG/HCPT were systematically investigated.Result: The NG/HCPT exhibited spherical morphology with an average diameter of around 65 nm,which was obtained from TEM measurements.Furthermore,the hydrodynamic radius(R_h)of NG/HCPT detected by DLS was 65.9 ± 0.4 nm.In addition,NG/HCPT was positively charged in PBS at p H 7.4 with zeta potential of 16.3±1.4 m V.The NG/HCPT possessed excellent stability under physiological conditions but rapid structural swelling and HCPT release in the reductive microenvironment.The half maximal inhibitory concentration(IC50)value of NG/HCPT was determined as 2.7 mg/L,which was lower than that of free HCPT(i.e.,7.9 mg/L)after 24 h coincubation.The free HCPT and NG/HCPT resulted in 3.5% and 8.9% early apoptotic cells,and 12.0% and 13.6% late apoptotic cells,respectively.The NG/HCPT showed superior mucoadhesiveness and penetrability within bladder wall.The NG/HCPT was highly selectively accumulated in bladder tissues and rarely in other organs.NG/HCPT induced remarkable tumor growth inhibition as compared with those with both PBS and free HCPT.The tumor necrosis areas was up to 46.3%±2.2% in the NG/HCPT group,which is about 3.8 times larger than that of free HCPT group(p < 0.01).However,there was only 1.5%±1.0% in the control group treated with PBS.The signal of PARP in NG/HCPT group was 2.2 times higher than that of the free HCPT group.The signal percentage of PCNA between the NG/HCPT and free HCPT groups was 11.4%.Conclusion1.A reduction-responsive cationic polypeptide nanogel was successfully synthesized through the sequential ROP of ZLL NCA,and LP NCA and LC NCA,and the subsequent deprotection.2.Compared with free HCPT,the reduction-sensitive property made the nanogel more accurately release HCPT and promote accumulation in T24 cells in vitro.3.The improved mucoadhesive and permeation properties of NG/HCPT could significantly inhibit tumor growth in an orthotopic bladder cancer model.The smart polypeptide nanogel paves the way for intravesical instillation of chemotherapy for patients with NMIBC.