EGFR Targeted Polymersomes Nanomedicines For Treating Orthotopic Tumors In Mice

As drug nanocarriers,polymersomes are facing many challenges,such as short blood circulation,poor cell selectivity,low uptake and slow intracellular drug release,nonbiodegradable materials or cumbersome preparations.There is still no polymersome nanomedicines advanced into clinical trials.Therefore,to address these problems,in this thesis we designed GE11 peptide-modified,reduction-sensitive disulfide-crosslinked biodegradable polymersome nanomedicines for targeted therapy of orthotopic tumors in mice.In chapter 2,we designed and synthesized copolymer polyethylene glycol-b-poly(trimethylene carbonate-co-1,2-dithiolan-trimethylene carbonate)(PEG-P(TMC-DTC))and GE11 coupled GE11-PEG-P(TMC-DTC).They self-assembled and automatically crosslinked to form polymersomes GE11-PS.Via pH gradient method DOX·HCl could be efficiently loaded into polymersomes yielding GE11-PS-DOX nanomedicine.We utilized DLS,TEM,MTT assays,flowcytometry and CLSM to characterize their physicochemical properties,stability,reduction sensitivity,cytotoxicity and targetability.It was found that GE11-PS-DOX has small size(76-80 nm)and high stability under physiological conditions,and in cytoplasmic mimicking reduction conditions DOX·HCl was quickly released.In SMMC-7721 cells that over-expresses EGFR,GE11-PS-DOX with 10% GE11 surface density showed the most prominent targetability and tumor suppression,illustrating the receptor mediated endocytosis pathway of GE11-PS-DOX.Moreover,in vivo studies in mice focusing on pharmacokinetics,ex vivo imaging,biodistribution and therapeutic effects were performed.It was revealed that GE11-PS-DOX had long blood circulation time with elimination half-life of 8.27 h.It enriched ca.13%ID/g at the tumor site in mice bearing subcutaneous SMMC-7721 liver tumor,which was 2-fold that of non-targeting PS-DOX.Even in mice bearing orthotopic SMMC-7721 liver tumor,accumulation at the tumor site in the liver tissue could be clearly identified.It is particularly interesting that GE11-PS-DOX significantly prolonged the survival rate of mice bearing orthotopic liver tumor without side effects and 50% complete regression(still alive on 180 d)was achieved.In chapter 3,we extended this platform technology by active loading of irinotecan hydrochloride(CPT-11)yielding GE11-PS-CPT and used for targeted therapy of EGFR overexpressing colorectal carcinoma.This polymersome nanomedicine was characterized in terms of physicochemical properties and antitumor activity both in cellular level and in animal level.It was discovered that although GE11 surface density of GE11-PS-CPT have strong yet different influence on cellular behavior of two colorectal cancer cells HCT-116 and CMT-93,which both displayed good targetability and decent internalization.Furthermore,the preliminary therapeutic studies on mice bearing orthotopic CMT-93 tumors indicated that GE11-PS-CPT could greatly inhibit the tumor growth and metastasis during treatment and within 4 cycles of administration after the treatment.Therefore,the polymersome nanomedicine GE11-PS is simple yet versatile,nontoxic and robust in the body,and possesses the properties of high accumulation in tumor site,targeted internalization and fast intracellular drug release as well as tumor growth inhibition,and thus has potential for clinical translation.