Matrix Metalloproteinase Responsive Multifunctional Nanocarriers For Cancer Therapy

Cancer is one of the biggest health burden and the leading causes of morbidity and mortality worldwide.Surgery,radiotherapy and chemotherapy are three major clinical options for treating cancer.Conventional chemotherapy,as the most commonly used anticancer pharmacotherapy,faces sevearl issues including poor drug response,serious adverse effects,and multidrug resistance(MDR).Although nanotechnology-based new drug delivery systems that have shown advantages over conventional drug carriers,the issues,like nanomaterials’ toxicity,nanoparticle’s stability/immature drug leakage,and low disease targetability,need to be addressed.In addition,the inter-individual variation,especially in the pharmacokinetic properties and drug response,significantly influences the therapeutic outcome of anticancer drugs.Therefore,the drug delivery system that can specifically and precisely target the tumor becomes an imperative requirement for future cancer treatment.Thanks to the advances in cancer biology and materials science,various tumor microenvironment responsive biomaterials based on the differences between the pathological feature of the tumorous and normal tissues have been developed for the construction of the tumor-targeted delivery system.Among them,matrix metalloproteinase(MMP)responsive nanomaterials have attracted a lot of attention.The first generation of the MMP-sensitive nanocarriers mainly target the tumor at the tissue level,while most anticancer drugs need to take action inside cancer cells,more specifically in their target organelles.The aim of this study is to develop novel matrix metalloproteinase-responsive nanomaterials/nanomedicine to improve drugs’ cancer targetabitliy and efficacy and decrease drugs’ adverse effects and resistance,and to reveal the mechanisms underlying the tumor targeting,drug delivery,and cancer sensitization.The study includes three parts,including:In the first part,we synthesized and explored the matrix metalloproteinase substrate-containing amphiphilic block copolymer(PEG-pp-PE)as the micelle building block,tumor targeting moiety,and P-glycoprotein inhibitor.As a micelle building block,the properties of PEG-pp-PE were studied.Using two well-known P-gp inhibitors:verapamil(small molecules)and TPGS(amphiphilic biomaterials)as the positive control,we investigate the inhibitory effects of PEG2k-pp-PE on P-glycoprotein.The mechanism of anti-Pgp effect was further studied.The results showed that P-gp inhibitors(PEG-pp-PE,Verapamil and TPGS)could inhibit the efflux of drugs to increase the accumulation of intracellular drugs,thereby enhance the drug effect in the multidrug resistant ovarian cancer cells(NCI/ADR-RES)in the monolayer cells and the multicellular tumor spheroids.We concluded that the inhibition of drug efflux was highly associated with the down-regulation of P-gp,the increase in the plasma membrane fluidity,and the inhibition of the P-gp ATPase activity.In the second part,we build an MMP2-triggered folate-targeted mixed micelle using two major functional polymers:PEG5k-pp-PE and FA-PEG2k-PE,and evaluated their tumor targetability both in vitro and in vivo.Dasatinib,as a model drug,can be loaded into the hydrophobic phospholipid core of the micelles with a sustained release behavior.In the tumor(MMP-2 rich)microenvironment,the outer protective layer,PEG5k,would be detached after MMP2-mediated cleavage,exposing the previously hidden folic acids on the micelle surface.This transformation led to the increased cellular uptake,deeper intratumor penetration and stronger antitumor activity in various in vitro models.In addition,the multifunctional micelles could effectively overcome the multidrug resistance and significantly increased the sensitivity of the drug-resistant tumor cells to dasatinib.Excellent physiochemical properties and good stability of the mixed micelles showed a prolonged circulation time,reduced accumulation in healthy tissues,enhanced tumor targeting effect and anti-tumor efficacy in the tumor-bearing mice.In the last part,we designed and synthesized a novel "all-in-one" multifunctional nanomaterial,which is able to self-assemble into a micelle structure for matrix metalloproteinase-2 sensitive tumor targeting and cell-penetrating peptide-mediated intracellular drug delivery.The "all-in-one" micelle maintains micellar structure intact in the physiological condition and in the presence of MMP-2 as well,preventing the immature drug leakage.The MMP-2 triggered TAT exposure on the micelle surface resulted in high drug uptake and penetration in both the monolayer tumor cells and drug-resistant tumor cell spheres,leading to high anticancer activity.In the tumor-bearing mice,the "all-in-one" micelles could significantly prolong the residence time of DiR in the tumor.