Yanxin Qi

Doxorubicin-Loaded Carborane-Conjugated Polymeric Nanoparticles as Delivery System for Combination Cancer Therapy

Carborane-conjugated amphiphilic copolymer nanoparticles were designed to deliver anticancer drugs for the combination of chemotherapy and boron neutron capture therapy (BNCT). Poly(ethylene glycol)-b-poly(L-lactide-co-2-methyl-2(2-dicarba-closo-dodecarborane)propyloxycarbonyl-propyne carbonate) (PLMB) was synthesized via the versatile reaction between decaborane and side alkynyl groups, and self-assembled with doxorubicin (DOX) to form drug-loaded nanoparticles. These DOX@PLMB nanoparticles could not only suppress the leakage of the boron compounds into the bloodstream due to the covalent bonds between carborane and polymer main chains, but also protect DOX from initial burst release at physiological conditions because of the dihydrogen bonds between DOX and carborane. It was demonstrated that DOX@PLMB nanoparticles could selectively deliver boron atoms and DOX to the tumor site simultaneously in vivo. Under the combination of chemotherapy and BNCT, the highest tumor suppression efficiency without reduction of body weight was achieved. This polymeric nanoparticles delivery system could be very useful in future chemoradiotherapy to obtain improved therapeutic effect with reduced systemic toxicity.

Time-programmed DCA and oxaliplatin release by multilayered nanofiber mats in prevention of local cancer recurrence following surgery

Local recurrence following surgery in cancer treatment remains a major clinical challenge. To increase antitumor activity but maintain toxicity in an acceptable level in prevention of local cancer recurrence, we demonstrated a dual drug-loaded multilayered fiber mats strategy, in which DCA and oxaliplatin were co-electrospun into the distinct layer of resultant fabrics and the oxaliplatin-loaded fibers layer was sealed between the basement film layer and other two fibers layers. The dual drug-loaded multilayered fiber mats exhibit time-programmed dual release behavior and synergistic effect upon cancer cells. Nontoxic DCA selectively promotes apoptosis of cancer cells through modulating cellular metabolism, and oxaliplatin subsequently kills the remained cancer cells in a low concentration. After implantation on the resection margin of cervical carcinoma on a murine model, the dual drug-loaded multilayered fiber mats displayed enhanced anti-recurrence efficacy and decreased side toxic effects over 30days compared with drug-loaded monolayered fiber mats. The time-programmed combination of DCA and oxaliplatin within multilayered nanofiber mats appears to be a promising strategy for local cancer treatment following resection.

Single-Stimulus Dual-Drug Sensitive Nanoplatform for Enhanced Photoactivated Therapy

Photoactivated therapy has become a complementary and attractive modality for traditional cancer treatment. Herein, we demonstrated a novel single-stimulus dual-drug sensitive nanoplatform, Cur-loaded Dex-Pt(N3) nanoparticles (Cur@DPNs) for enhanced photoactivated therapy. The developed Cur@DPNs could be photoactivated by UVA light to simultaneously generate instant reactive oxygen species from Cur for fast photodynamic therapy and release lasting Pt(II) from Pt(N3) for long-acting photochemotherapy. Compared with small free drugs and individual photoactivated therapy, Cur@DPNs exhibited enhanced photoactivated cytotoxicity and in vivo antitumor efficacy with low systemic toxicity accompanied. Therefore, the single-stimulus dual-drug sensitive nanoplatform is convinced to be a promising strategy for multidrug delivery, site-selective and combinational photoactivated therapy in the near future.

Asymmetric copolymer vesicles to serve as a hemoglobin vector for ischemia therapy

Self-aggregated vesicles have been considered to be promising candidates for hemoglobin-based oxygen carriers. Here, amphiphilic hetero-triblock copolymers are designed and synthesized with the capacity to self-assemble into polymer vesicles (polymersomes). Conceivably, vesicles are formed with asymmetric membranes, which achieve enhanced encapsulation efficiency of hemoglobin (Hb) beyond the diblock counterpart. Furthermore, hemoglobin-loaded vesicles (HbV) are fabricated with high Hb content and submicron particle sizes. The gas-binding capability, oxygen affinity and methemoglobin (metHb) level of the HbV dispersions are all comparable to the natural erythrocytes. In vitro HbV stability studies further reveal that the encapsulation of Hb within vesicles can greatly avoid the existence of free Hb and shows no interference with cells, especially for blood components. To evaluate the efficacy on ischemia reperfusion, HbV suspended in a plasma expander is transfused as a resuscitation fluid into an acute anemia rat model. Results demonstrate that the combined infusion of the plasma expander with HbV effectively ameliorates the lethal shock symptom and reduces short-term mortality. Concurrently, rats transfused with HbV are void of the acute tubular necrosis caused by the filtration of dissociated Hb dimers from glomeruli. We envision that the oxygen carriers derived from polymer self-assembly technology will become an alternative strategy for future development of blood substitutes.

Amphiphilic Polycarbonates from Carborane-Installed Cyclic Carbonates as Potential Agents for Boron Neutron Capture Therapy

Carboranes with rich boron content have showed significant applications in the field of boron neutron capture therapy. Biodegradable derivatives of carborane-conjugated polymers with well-defined structure and tunable loading of boron atoms are far less explored. Herein, a new family of amphiphilic carborane-conjugated polycarbonates was synthesized by ring-opening polymerization of a carborane-installed cyclic carbonate monomer. Catalyzed by TBD from a poly(ethylene glycol) macroinitiator, the polymerization proceeded to relatively high conversions (>65%), with low polydispersity in a certain range of molecular weight. The boron content was readily tuned by the feed ratio of the monomer and initiator. The resultant amphiphilic polycarbonates self-assembled in water into spherical nanoparticles of different sizes depending on the hydrophilic-to-hydrophobic ratio. It was demonstrated that larger nanoparticles (PN150) were more easily subjected to protein adsorption and captured by the liver, and smaller nanoparticles (PN50) were more likely to enter cancer cells and accumulate at the tumor site. PN50 with thermal neutron irradiation exhibited the highest therapeutic efficacy in vivo. The new synthetic method utilizing amphiphilic biodegradable boron-enriched polymers is useful for developing more-selective and -effective boron delivery systems for BNCT.

Insight into the fabrication of polymeric particle based oxygen carriers

For the sake of protein stability and targeted application as blood substitutes, formulation customization of hemoglobin-loaded polymeric particles (HbP) was conducted via a double emulsion method. Screening of the emulsification parameters was firstly performed for the stability of Hb, and the structure and functions of recovered Hb could be well preserved via CD and UV-vis spectroscopy investigation. In the optimized conditions, Hb was loaded into the polymeric matrix formed of three material compositions. They were poly(ϵ-caprolactone)(PCL), poly(ethylene glycol)-block-poly(allyl glycidyl ether) (functionalized with mercaptopropionic acid)-block-poly(ϵ-caprolactone) (PEG-PAGE(MPA)-PCL), and the blend of the two polymers. The morphology, internal structure, in vitro leakage and hemocompatibility of the HbP products were characterized in detail, and the encapsulation mechanism was explored by the combined analysis of the encapsulation efficiency, non-specific protein adsorption and in vitro leakage studies. Results showed that the burst release effect found in homopolymers could be alleviated by use of block copolymers due to the reduced protein adsorption, and completely avoided by further cross-linking of particles through carbonyl-amino condensation reactions. The amphiphilic copolymers showed relatively high stability in blood and no interference with blood components compared with hydrophobic PCL. These results suggest that both the optimization of emulsion formation and material composition are prerequisite for stable formulations of Hb encapsulated in polymeric particles.

Protein-Resistant Biodegradable Amphiphilic Graft Copolymer Vesicles as Protein Carriers

The protein adsorption and self-assembly behavior of biocompatible graft copolymer, poly(lactide-co-diazidomethyl trimethylene carbonate)-g-poly(ethylene glycol) [P(LA-co-DAC)-g-PEG], were systematically studied. The graft copolymers showed enhanced resistance to non-specific protein adsorption compared with their block copolymer counterparts, indicative of the increased effect of PEG density beyond PEG length. Diverse nanostructures including vesicles can be assembled from the amphiphilic graft copolymers with well-defined nano-sizes. Hemoglobin (Hb), as a model protein, can be entrapped in the formed vesicles and keep the gas-binding capacity. The reduced release rate of Hb from graft copolymer vesicles indicated the relatively stable membrane packing compared with block copolymer counterpart.

Novel multi-sensitive pseudo-poly(amino acid) for effective intracellular drug delivery

Novel intracellular pH, glutathione (GSH) and reactive oxygen species (ROS)-responsive nanoparticles were obtained using mPEG2k-block-redox dual sensitive chain-block-mPEG2k (PRDSP) which was prepared by Cu(I)-catalyzed azide–alkyne cycloaddition (CuAAC) click polymerization. The disulfide bond, peroxalate ester and triazole units were regularly and repeatedly arranged in the hydrophobic blocks. The disulfide bond was GSH-sensitive and the peroxalate ester structure could be disrupted by acid and hydrogen peroxide. In addition, the triazole units are capable of forming pH-responsive hydrogen bonds. Dynamic Light Scattering (DLS) and transmission electron microscopy (TEM) were used to investigate the pH, GSH and ROS sensitivity of the PRDSP nanoparticles (NPs). The results indicated that the average diameter, size distribution and morphology greatly changed upon adding GSH/H2O2 or modulating the pH. As the preloaded model anticancer drug, doxorubicin (DOX) was quickly released from DOX-loaded PRDSP (PRDSP@DOX) NPs by addition of 10 mM glutathione (GSH), or 10 mM H2O2 or under acidic conditions rather than under physiological conditions. Confocal laser scanning microscopy (CLSM) and flow cytometric analyses revealed that PRDSP@DOX could effectively deliver DOX into the cytoplasm and nucleus of cells. Therefore, PRDSP NPs may be a promising redox heterogeneity-sensitive carrier for efficient and controlled anticancer drug release.

Synthesis of the Hemoglobin‐Conjugated Polymer Micelles by Thiol Michael Addition Reactions

Amphiphilic triblock copolymers mPEG-b-PMAC-b-PCL are synthesized using methoxyl poly(ethylene glycol), cyclic carbonic ester monomer including acryloyl group, and ε-caprolactone. Copolymers are self-assembled into core-shell micelles in aqueous solution. Thiolated hemoglobin (Hb) is conjugated with micelles sufficiently through thiol Michael addition reaction to form hemoglobin nanoparticles (HbNs) with 200 nm in diameter. The conjugation of Hb onto the micelle surface is further confirmed by X-ray photoelectron spectroscopy. Feeding ratio of copolymer micelles to Hb at 1:3 would lead to the highest hemoglobin loading efficiency 36.7 wt%. The UV results demonstrate that the gas transporting capacity of HbNs is well remained after Hb is conjugated with polymeric micelles. Furthermore, the obtained HbNs have no obvious detrimental effects on blood components in vitro. This system may thus have great potential as one of the candidates to be developed as oxygen carriers and provide a reference for the modification of protein drugs.

Synthesis and sequence-controlled self-assembly of amphiphilic triblock copolymers based on functional poly(ethylene glycol)

Given the increasing prosperity of multifunctional poly(ethylene glycol) (mf-PEG), an amphiphilic triblock copolymer, poly(ethylene glycol)-block-poly(e-caprolactone)-block-poly(allyl glycidyl ether) (mPEG-PCL-PAGE), was synthesized by a combination of living ring-opening polymerization (ROP) and click chemistry. A post-modification of the allyl groups can be achieved via a radical mediated thiol–ene reaction to prepare copolymers bearing side-chain carboxylic or amino groups [mPEG-PCL-PAGE(R)]. The chemical structures and compositions of these polymers were systematically characterized using Fourier transform infrared spectroscopy (FT-IR), proton nuclear magnetic resonance spectroscopy (1H NMR) and gel permeation chromatography (GPC). The copolymers could readily assemble into micelles in aqueous solution as confirmed by fluorescence spectroscopy, dynamic light scattering (DLS), transmission electron microscopy (TEM) and zeta potential measurements. MTT and hemocompatibility assays indicated that the micelles showed no associated cytotoxicity and could be potentially used for nanomedicine. Intriguingly, the specific sequence of [mPEG-PCL-PAGE(R)] showed pH-induced morphology transformation, while the corresponding polymer with a middle PAGE segment [mPEG-PAGE(R)-PCL] did not, which, we propose, was attributed to the tunable hydrophilicity and distinctive folding of the molecular chain at varied pH values. This finding offers a route to regulate the self-assembly behaviors in polymer systems by controlling the block sequence.