Zhicheng Pan

Construction of Targeting-Clickable and Tumor-Cleavable Polyurethane Nanomicelles for Multifunctional Intracellular Drug Delivery

New strategies for the construction of versatile nanovehicles to overcome the multiple challenges of targeted delivery are urgently needed for cancer therapy. To address these needs, we developed a novel targeting-clickable and tumor-cleavable polyurethane nanomicelle for multifunctional delivery of antitumor drugs. The polyurethane was synthesized from biodegradable poly(ε-caprolactone) (PCL) and L-lysine ethyl ester diisocyanate (LDI), further extended by a new designed L-cystine-derivatized chain extender bearing a redox-responsive disulfide bond and clickable alkynyl groups (Cys-PA), and finally terminated by a detachable methoxyl-poly(ethylene glycol) with a highly pH-sensitive benzoic-imine linkage (BPEG). The obtained polymers show attractive self-assembly characteristics and stimuli-responsiveness, good cytocompatibility, and high loading capacity for doxorubicin (DOX). Furthermore, folic acid (FA) as a model targeting ligand was conjugated to the polyurethane micelles via an efficient click reaction. The decoration of FA results in an enhanced cellular uptake and improved drug efficacy toward FA-receptor positive HeLa cancer cells in vitro. As a proof-of-concept, this work provides a facile approach to the design of extracellularly activatable nanocarriers for tumor-targeted and programmed intracellular drug delivery.

Synthesis and characterization of biodegradable polyurethanes with folate side chains conjugated to hard segments

In this study, a novel folate-conjugated chain extender (LDDFA) was designed and synthesized to enhance site-specific intracellular delivery of drug carriers against folate receptor overexpressing tumors. A series of biodegradable polyurethanes containing high folate content were prepared using poly(e-caprolactone) (PCL) and poly(ethylene glycol) (PEG) as soft segments, and 1,3-propanediol (PDO), L-lysine ethyl ester diisocyanate (LDI) and LDDFA as hard segments. The resultant polyurethanes were characterized with proton nuclear magnetic resonance spectroscopy (1H NMR), Fourier-transform infrared (FTIR) spectroscopy and gel permeation chromatography (GPC). The folate contents were quantitatively analyzed with ultraviolet (UV) spectrophotometry. The folate-conjugated polymers could self-assemble into micelles with particularly loose hydrophobic cores and exhibiting low critical micelle concentration (CMC) in aqueous solution, in which folic acid (FA) molecules were located in the micelle shells and the PEG segments were in the outer corona, as confirmed by pyrene fluorescence probe techniques, transmission electron microscopy (TEM), dynamic lighting scattering (DLS), and dissipative particle dynamics (DPD) simulation. The folate-conjugated polyurethane micelles displayed enhanced drug loading capacity for doxorubicin (DOX), sustained drug release, preferential internalization by the human epidermoid carcinoma cell line (KB cells) and pronounced cytotoxicity compared to polyurethane micelles without FA, as verified by typical confocal microscopy images (CLSM) and methyl tetrazolium (MTT) assay, respectively. Our present work provides a new route for the preparation of folate-conjugated polyurethanes with high FA content, which could be a good candidate for active targeting conjugates for multifunctional carriers to achieve efficient drug delivery.

Multifunctional Mixed Micelles Cross-Assembled from Various Polyurethanes for Tumor Therapy

A challenge in the development of multifunctional drug delivery systems is to establish a reasonable and effective synthetic route for multifunctional polymer preparation. Herein, we propose a unique protocol to prepare multifunctional micelles by a cross-assembly process using three different functional polyurethanes incorporating acidic sensitive hydrazone, folic acid for active targeting, and gemini quaternary ammonium (GQA) as efficient cell uptake ligands, respectively. These multifunctional mixed micelles (GFHPMs) have been endowed tunable particle sizes and zeta potential and a unique three-order-layer cross-assemble structure. Their drug-loading contents have been significantly improved, and drug release profiles displayed controlled release of their payloads under acid condition. The folate and GQA ligands showed a synergistic effect to enhance the cell uptake. Biodistribution and antitumor effect of these micelles were systematically investigated in vivo, the mixed micelles could penetrate into the depths of tumors, and drug concentrations in tumors reached the maximum of 6.5% ID/g at 24 h, resulting in an excellent therapeutic effect that the volumes of tumors treated with GFHPM are five times smaller than those treated with blank micelles. Our present work provides an effective approach to the design of multifunctional nanocarriers for tumor-targeted and programmed intracellular drug delivery.

Surface Distribution and Biophysicochemical Properties of Polymeric Micelles Bearing Gemini Cationic and Hydrophilic Groups.

Polymeric micelles containing cationic gemini quaternary ammonium (GQA) groups have shown enhanced cellular uptake and efficient drug delivery, while the incorporation of poly(ethylene glycol) (PEG) corona can potentially reduce the absorption of cationic carriers by opsonic proteins and subsequent uptake by mononuclear phagocytic system (MPS). To understand the interactions of GQA and PEG groups and their effects on the biophysicochemical characteristics of nanocarriers, a series of polyurethane micelles containing GQA and different molecular weights of PEG were prepared and carefully characterized. It was found that the GQA and PEG groups are unevenly distributed on the micellar surface to form two kinds of hydrophilic domains. As a result, the particle surface with some defects cannot be completely shielded by the PEG corona. Despite this, the longer PEG chains with a brush conformation provide superior stabilization and steric repulsion against the absorption of proteins and, thus, can reduce the cytotoxicity, protein absorption, and MPS uptake of micelles to some extent. This study provides a new understanding on the interactions between PEG chains and cationic groups and a guideline for the design and fabrication of safe and effective drug delivery systems.

Preparation and characterization of controlled heparin release waterborne polyurethane coating systems

In this study, to improve hemocompatibility of biomedical materials, a waterborne polyurethane (WPU)/heparin release coating system (WPU/heparin) is fabricated via simply blending biodegradable WPU emulsions with heparin aqueous solutions. The surface compositions and hydrophilicity of these WPU/heparin blend coatings are characterized by attenuated total reflectance infrared spectroscopy (ATR-FTIR) and water contact angle measurements. These WPU/heparin blend coatings show effectively controlled release of heparin, as determined by the toluidine blue method. Furthermore, the biocompatibility and anticoagulant activity of these blend coatings are evaluated based on the protein adsorption, platelet adhesion, activated partial thromboplastin time (APTT), thrombin time (TT), hemolysis, and cytotoxicity. The results indicate that better hemocompatibility and cytocompatilibity are obtained due to blending heparin into this waterborne polyurethane. Thus, the WPU/heparin blend coating system is expected to be valuable for various biomedical applications.

Effect of Trastuzumab on the Micellization Properties,Endocytic Pathways and Antitumor Activities of Polyurethane-based Drug Delivery System

Polyurethane micelles (PM)-based nanovehicles have shown great potential in targeted delivery of therapeutics and diagnostics into tumors. However, the pathways of PMs entering cancer cells and the action mechanism of targeting ligands have yet to be understood. In this contribution, the actively-targeted PM were developed using trastuzumab as a model targeting group. It was found that PM were mainly taken up by SKOV-3 tumor cells via a micropinocytosis process, while the incorporation of trastuzumab to PM enabled a receptor-mediated endocytosis of nanocarriers in cancer cells, leading to more efficient cell entry and enhanced anticancer efficacy of chemotherapeutic drugs both in vitro and in vivo. This study is advantageous to the understanding of the action mechanism of trastuzumab, and significant for the construction of improved formulations for targeted delivery and precise therapy.