Zengshi Zha

Matrix Metalloproteinase-Responsive Multifunctional Peptide-Linked Amphiphilic Block Copolymers for Intelligent Systemic Anticancer Drug Delivery

The amphiphilic block copolymer anticancer drug nanocarriers clinically used or in the progress of clinical trials frequently suffer from modest final therapeutic efficacy due to a lack of intelligent features. For example, the biodegradable amphiphilic block copolymer, poly(ethylene glycol)-b-poly(d,l-lactide) (PEG-PDLLA) has been approved for clinical applications as a paclitaxel (PTX) nanocarrier (Genexol-PM) due to the optimized pharmacokinetics and biodistribution; however, a lack of intelligent features limits the intracellular delivery in tumor tissue. To endow the mediocre polymer with smart properties via a safe and facile method, we introduced a matrix metalloproteinase (MMP)-responsive peptide GPLGVRGDG into the block copolymer via efficient click chemistry and ring-opening polymerization to prepare PEG-GPLGVRGDG-PDLLA (P1). P1 was further self-assembled into micellar nanoparticles (NPs) to load PTX, which show MMP-2-triggered dePEGylation due to cleavage of the peptide linkage. Moreover, the residual VRGDG sequences are retained on the surface of the NPs after dePEGylation, which can serve as ligands to facilitate the cellular uptake. The cytotoxicity of PTX loaded in P1 NPs against 4T1 cells is significantly enhanced as compared with free PTX or PTX-loaded PEG-GPLGVRG-PDLLA (P2) and PEG-PDLLA (P3) NPs. In vivo studies confirmed that PTX-loaded P1 NPs show prolonged blood circulation, which are similar to P2 and P3 NPs but exhibit more-efficient accumulation in the tumor site. Ultimately, PTX-loaded P1 NPs display statistically significant improvement of antitumor activity against tumor-bearing mice via systemic administration. Therefore, the strategy by facile incorporation of a responsive peptide linkage between PEG and PDLLA is a promising approach to improving the therapeutic efficacy of anticancer-drug-loaded amphiphilic block copolymer micelles.

Intracellular glutathione-depleting polymeric micelles for cisplatin prodrug delivery to overcome cisplatin resistance of cancers

&NA; The intrinsic or acquired cisplatin resistance of cancer cells frequently limits the final therapeutic efficacy. Detoxification by the high level of intracellular glutathione (GSH) plays critical roles in the majority of cisplatin‐resistant cancers. In this report, we designed an amphiphilic diblock copolymer composed of poly(ethylene glycol) (PEG) and polymerized phenylboronic ester‐functionalized methacrylate (PBEMA), PEG‐b‐PBEMA, which can self‐assemble into micelles in aqueous solutions to load hydrophobic cisplatin prodrug (Pt(IV)). Pt(IV)‐loaded PEG‐b‐PBEMA micelles (PtBE‐Micelle) reverse cisplatin‐resistance of cancer cells through improving cellular uptake efficiency and reducing intracellular GSH level. We found that the cellular uptake amount of platinum from PtBE‐Micelle was 6.1 times higher than that of free cisplatin in cisplatin‐resistant human lung cancer cells (A549R). Meanwhile, GSH concentration of A549R cells was decreased to 32% upon treatment by PEG‐b‐PBEMA micelle at the phenyl borate‐equivalent concentration of 100 &mgr;M. PtBE‐Micelle displayed significantly higher cytotoxicity toward A549R cells with half maximal inhibitory concentration (IC50) of cisplatin‐equivalent 0.20 &mgr;M compared with free cisplatin of 33.15 &mgr;M and Pt(IV)‐loaded PEG‐b‐poly(&egr;‐caprolactone) micelles of cisplatin‐equivalent 0.75 &mgr;M. PtBE‐Micelle can inhibit the growth of A549R xenograft tumors effectively. Accordingly, PEG‐b‐PBEMA micelles show great potentials as drug delivery nanocarriers for platinum‐based chemotherapy toward cisplatin‐resistant cancers.

Smart Asymmetric Vesicles with Triggered Availability of Inner Cell-Penetrating Shells for Specific Intracellular Drug Delivery

Smart nanocarriers attract considerable interest in the filed of precision nanomedicine. Dynamic control of the interaction between nanocarriers and cells offers the feasibility that in situ activates cellular internalization at the targeting sites. Herein, we demonstrate a novel class of enzyme-responsive asymmetric polymeric vesicles self-assembled from matrix metalloproteinase (MMP)-cleavable peptide-linked triblock copolymer, poly(ethylene glycol)-GPLGVRG-b-poly(ε-caprolactone)-b-poly(3-guanidinopropyl methacrylamide) (PEG-GPLGVRG-PCL-PGPMA), in which the cell-penetrating PGPMA segments asymmetrically distribute in the outer and inner shells with fractions of 9% and 91%, respectively. Upon treatment with MMP-2 to cleave the stealthy PEG shell, the vesicles undergo morphological transformation into fused multicavity vesicles and small nanoparticles, accompanied by redistribution of PGPMA segments with 76% exposed to the outside. The vesicles after dePEGylation show significantly increased cellular internalization efficiency (∼10 times) as compared to the original ones due to the triggered availability of cell-penetrating shells. The vesicles loading hydrophobic anticancer drug paclitaxel (PTX) in the membrane exhibit significantly enhanced cytotoxicity against MMP-overexpressing HT1080 cells and multicellular spheroids. The proposed vesicular system can serve as a smart nanoplatform for in situ activating intracellular drug delivery in MMP-enriched tumors.

Thiolactone Chemistry-Based Combinatorial Methodology to Construct Multifunctional Polymers for Efficacious Gene Delivery

Hydrophobic segments and amino moieties in polymeric nonviral gene vectors play important roles in overcoming a cascade of barriers for efficient gene delivery. However, it remains a great challenge to facilely construct well-defined multifunctional polymers through optimization of the amino and hydrophobic groups. Herein, we choose thiolactone chemistry to perform the ring opening reaction of varying hydrophobic groups-modified thiolactones by various amines to generate mercapto groups for further Michael addition reaction with poly[2-(acryloyloxy)ethyl methacrylate] (PAOEMA). Based on the combinatorial methodology, a series of multifunctional polymers were prepared and screened. The polymer (P3D) from tetraethylenepentamine and heptafluorobutyric acid-functionalized thiolactone is the most efficacious one with significantly higher gene transfection efficiency and lower cytotoxicity compared with polyethylenimine (PEI) (branched average Mw ∼ 25 000 Da) and Lipofectamine 2000. Cellular uptake and intracellular distribution studies indicate that P3D complexes show high-efficiency endocytosis and excellent endosomal escape. Accordingly, thiolactone chemistry-based combinatorial methodology allows for facile integration of multifunctional groups to prepare simultaneous efficacious and low-cytotoxic gene delivery vectors.

Integrated Nanoparticles To Synergistically Elevate Tumor Oxidative Stress and Suppress Antioxidative Capability for Amplified Oxidation Therapy

The improved antioxidant system of cancer cells renders them well-adaptive to the intrinsic oxidative stress in tumor tissues. On the other hand, cancer cells are more sensitive to elevated tumor oxidative stress as compared with normal cells due to their deficient reactive oxygen species-eliminating systems. Oxidation therapy of cancers refers to the strategy of killing cancer cells through selectively increasing the oxidative stress in tumor tissues. In this article, to amplify the oxidation therapy, we develop integrated nanoparticles with the properties to elevate tumor oxidative stress and concurrently suppress the antioxidative capability of cancer cells. The amphiphilic block copolymer micelles of poly(ethylene glycol)-b-poly[2-((((4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzyl)oxy)carbonyl)oxy)ethyl methacrylate] (PEG-b-PBEMA) are integrated with palmitoyl ascorbate (PA) to form hybrid micelles (PA-Micelle). PA molecules at pharmacologic concentrations serve as a prooxidant to upregulate the hydrogen peroxide (H2O2) level in tumor sites and the PBEMA segment exhibits H2O2-triggered release of quinone methide for glutathione depletion to suppress the antioxidative capability of cancer cells, which synergistically and selectively kill cancer cells for tumor growth suppression. Given the significantly low side toxicity against normal tissues, this novel integrated nanoparticle design represents a novel class of nanomedicine systems for high-efficiency oxidation therapy with the potentials to be translated to clinical applications.

Oxygen-independent combined photothermal/photodynamic therapy delivered by tumor acidity-responsive polymeric micelles

ABSTRACT Tumor hypoxia strikingly restricts photodynamic therapy (PDT) efficacy and limits its clinical applications in cancer therapy. The ideal strategy to address this issue is to develop oxygen‐independent PDT systems. Herein, the rationally designed tumor pH‐responsive polymeric micelles are devised to realize oxygen‐independent combined PDT and photothermal therapy (PTT) under near‐infrared light (NIR) irradiation. The triblock copolymer, poly(ethylene glycol)‐b‐poly(&egr;‐caprolactone)‐b‐poly(2‐(piperidin‐1‐yl)ethyl methacrylate) (PEG‐b‐PCL‐b‐ PPEMA), was prepared to co‐encapsulate cypate and singlet oxygen donor (diphenylanthracene endoperoxide, DPAE) via self‐assembly to obtain the micellar delivery system (C/O@N‐Micelle). C/O@N‐Micelle showed remarkable tumor accumulation and improved cellular internalization (2.1 times) as the pH value was changed from 7.4 during blood circulation to 6.8 in tumor tissues. The micelles could produce a potent hyperthermia for PTT of cypate under 808 nm NIR irradiation, which simultaneously induced thermal cycloreversion of DPAE generating abundant singlet oxygen for PDT without participation of tumor oxygen. Finally, the photothermally triggered PDT and PTT combination achieved efficient tumor ablation without remarkable systemic toxicity in an oxygen‐independent manner. This work represents an efficient strategy for oxygen‐independent combined PDT and PTT of cancers under NIR irradiation through co‐encapsulation of cypate and DPAE into tumor pH‐responsive polymeric micelles. Graphical abstract Figure. No caption available.

Sustained and Bioresponsive Two-Stage Delivery of Therapeutic miRNA via Polyplex Micelle-Loaded Injectable Hydrogels for Inhibition of Intervertebral Disc Fibrosis

Intervertebral disc degeneration (IDD) is frequently caused by gradual pathological changes inside intervertebral discs (IVDs) and progressive fibrosis. MicroRNA-29 (miR-29) family possesses potent fibrosis suppression capability, but their application for treatment of chronic IDD is limited due to lack of suitable local delivery systems. In this report, given various overexpressed matrix metalloproteinases (MMPs) during IDD, injectable MMP-degradable hydrogels encapsulating MMP-responsive polyplex micelles are developed for sustained and bioresponsive delivery of miR-29a into nucleus pulposus cells via a two-stage process. Cationic block copolymers are designed to complex miR-29a, and subsequently mixed with the poly(ethylene glycol) (PEG) gelation precursors and MMP-cleavable peptide cross-linkers for in situ formation of polyplex micelle-encapsulated hydrogels in the diseased IVDs. In the presence of MMPs, the polyplex micelles are first released by MMP cleavage of the hydrogels, and subsequently, MMPs-responsive detachment of PEG shells from polyplex micelles contributes to efficient cellular uptake and endosomal escape. MiR-29a is demonstrated to effectively silence the expression of MMP-2, inhibit the fibrosis process, and reverse IDD in animal models through blocking the β-catenin translocation pathway from the cytoplasm to the nucleus. This two-stage bioresponsive local miRNA delivery system represents a novel and promising strategy for the treatment of chronic IDD.