Nijia Song

Toward the Next-Generation Nanomedicines: Design of Multifunctional Multiblock Polyurethanes for Effective Cancer Treatment

Specific accumulation of therapeutics at tumor sites to improve in vivo biodistribution and therapeutic efficacy of anticancer drugs is a major challenge for cancer therapy. Herein, we demonstrate a new generation of intelligent nanosystem integrating multiple functionalities in a single carrier based on multifunctional multiblock polyurethane (MMPU). The smart nanocarriers equipped with stealth, active targeting, and internalizable properties can ferry paclitaxel selectively into tumor tissue, rapidly enter cancer cells, and controllably release their payload in response to an intracellular acidic environment, thus resulting in an improved biodistribution and excellent antitumor activity in vivo. Our work provides a facile and versatile approach for the design and fabrication of smart intracellular targeted nanovehicles for effective cancer treatment, and opens a new era in the development of biodegradable polyurethanes for next-generation nanodelivery systems.

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.

The degradation and biocompatibility of waterborne biodegradable polyurethanes for tissue engineering

To better investigate the degradation and biocompatibility of waterborne biodegradable polyurethanes for tissue engineering, a series of new waterborne biodegradable polyurethanes (PEGPUs) with low degree of crosslinking was synthesized using IPDI, BDO and L-lysine as hard segments, PCL and PEG as soft segment. The bulk structures and properties of the prepared polyurethanes were characterized by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), tensile mechanical tests and water contact angle (WCA) measurements. The degree of microphase separation was slightly improved because of the lowered crosslinking degree of these PEGPUs in comparison with the high cross-linking degree samples, leading to good mechanical properties, as indicated by DSC and stress-strain data. Moreover, biodegradability of the polyurethanes was evaluated in phosphate buffer solutions (PBS) under different pH values and enzymatic solution at pH 7.4 through weight loss monitoring. The results suggested that the degradation of these PEGPUs was closely related to their bulk and surface properties. And the degradation products didn’t show apparent inhibition effect against fibroblasts in vitro. These studies demonstrated that the waterborne biodegradable polyurethanes could find potential use in soft tissue engineering and tissue regeneration.

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.

The preliminary study of immune superparamagnetic iron oxide nanoparticles for the detection of lung cancer in magnetic resonance imaging

To improve the sensitive and specific detection of metastasis of lung cancer, this study fabricated immune superparamagnetic iron oxide nanoparticles (SPIONs) used in magnetic resonance (MR) immumoimaging. These SPIONs were coated with oleic acid and carboxymethyl dextran, and then conjugated to mouse anti-CD44v6 monoclonal antibody. The physicochemical properties of magnetic nanoparticles without monoclonal antibody were characterized by X-ray powder diffraction (XRD), thermogravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FTIR). The sizes of the nanoparticles were determined by dynamic light scattering measurements (DLS) and transmission electron microscope (TEM). Coated nanoparticles could well disperse in water with low dosage of CMD as the Fe/CMD ratio is 1/1 and 2/1 (w/w). Importantly, these SPIONs have relatively high saturation magnetization, as measured by vibrating sample magnetometer (VSM). They could efficiently become the transversal relaxation times (T2) contrast agent to improve detection limit through measured in vitro magnetic resonance imaging (MRI) and actively target human lung adenocarcinoma (A549) cells in vitro cell culture. Thus, these immune SPIONs are potentially useful for lung tumor-targeting diagnosis.

Gemini quaternary ammonium-incorporated biodegradable multiblock polyurethane micelles for brain drug delivery

Brain drug delivery is still facing significant challenges due to the low permeability of the blood–brain barrier (BBB). To overcome such an insurmountable obstacle, we developed gemini quaternary ammonium (GQA) as a cell penetrating molecule incorporated into biodegradable multiblock poly(e-caprolactone urethanes)s (BMPUs) drug nanocarriers for improvement of drug accumulation in brain parenchyma. The zeta potential of Dox-loaded GQA-BMPUs micelles was around 26 mV with a mean particle size near 100 nm. It was found that GQA-BMPUs micelles achieved steadily time-dependent and concentration-dependent Dox accumulation in human brain microvascular endothelial cells (HBMECs) much higher than GQA-free BMPUs micelles and free Dox, as confirmed by flow cytometry and confocal laser scanning microscopy (CLSM) experiments. Meanwhile, no pronounced cytotoxicity was noticed in GQA-BMPUs micelles and GQA-free BMPUs micelles, and Dox associated cytotoxicity might be reduced once encapsulated into micelles. More importantly, CLSM of brain sections showed higher accumulation of Dox-loaded GQA-BMPUs micelles in the subcortical area after administrated intravenously, while no Dox accumulation was observed in either Dox-BMPUs micelles or free Dox formulation. Coupling with in vivo pharmacokinetics, biodistribution and histological toxicity studies, the results show that GQA introduced into drug nanocarriers is a promising avenue to transport therapeutic agents across BBB and improve brain drug accumulation.

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.