V.H. Giang Phan

Stimuli-Sensitive Injectable Hydrogels Based on Polysaccharides and Their Biomedical Applications

Stimuli-sensitive injectable polymeric hydrogels are one of the promising delivery vehicles for the controlled release of bioactive agents. In aqueous solutions, these polymers are able to switch sol-to-gel transitions in response to various stimuli including pH, temperature, light, enzyme and magnetic field. Therapeutic agents, including chemotherapeutic agents, protein drugs or cells, are easily mixed with the low-viscous polymer solution at room temperature. Therapeutic-agents-containing solutions are readily injected into target sites through syringe or catheter, which could form hydrogel depot and serve as bioactive molecules release carriers. In particular, they are convenient for in vivo injection in a minimally invasive manner. Owing to their ease of handling, hydrogel scaffolds encapsulated with a wide array of therapeutic agents including growth factors, cells or fillers have been used in regeneration or filling of the defect area. Therefore, injectable hydrogels found a variety of biomedical applications, such as drug delivery and tissue engineering. Here, we summarize the chemical designs and recent developments of polysaccharide-based injectable hydrogels, giving a special attention to hydrogels prepared using amphiphilic polysaccharides for biomedical applications. Advantages and future perspectives of polysaccharide-based injectable hydrogels are highlighted.

Poly(amino carbonate urethane)-based biodegradable, temperature and pH-sensitive injectable hydrogels for sustained human growth hormone delivery

In this study, a new pH-/temperature-sensitive, biocompatible, biodegradable, and injectable hydrogel based on poly(ethylene glycol)-poly(amino carbonate urethane) (PEG-PACU) copolymers has been developed for the sustained delivery of human growth hormone (hGH). In aqueous solutions, PEG-PACU-based copolymers existed as sols at low pH and temperature (pH 6.0, 23 °C), whereas they formed gels in the physiological condition (pH 7.4, 37 °C). The physicochemical characteristics, including gelation rate, mechanical strength and viscosity, of the PEG-PACU hydrogels could be finely tuned by varying the polymer weight, pH and temperature of the copolymer. An in vivo injectable study in the back of Sprague-Dawley (SD) rats indicated that the copolymer could form an in situ gel, which exhibited a homogenous porous structure. In addition, an in vivo biodegradation study of the PEG-PACU hydrogels showed controlled degradation of the gel matrix without inflammation at the injection site and the surrounding tissue. The hGH-loaded PEG-PACU copolymer solution readily formed a hydrogel in SD rats, which subsequently inhibited the initial hGH burst and led to the sustained release of hGH. Overall, the PEG-PACU-based copolymers prepared in this study are expected to be useful biomaterials for the sustained delivery of hGH.

Pancreatic cancer therapy using an injectable nanobiohybrid hydrogel

Nanobiohybrid hydrogels, which are composed of inorganic nanoparticles and biodegradable polymeric hydrogels, have received special attention in the field of drug and protein delivery. These systems exploit the unique advantages of each component to improve the efficacy of the therapeutic agents and minimize undesirable side effects. The objective of this study was to develop a gemcitabine-loaded nanobiohybrid hydrogel to overcome the limitations of this anticancer drug, such as the very short half-life of gemcitabine (GEM) in plasma, the systemic toxicity from high-dose therapy, and the need for repeated administration during treatment. The proposed injectable nanobiohybrid hydrogel for controlled release of GEM was prepared through intercalation and adsorption of GEM to interlayer galleries and surfaces of montmorillonite (MMT) nanoparticles (forming MMT–GEM complexes), followed by the dispersion of the MMT–GEM complexes into the injectable, biodegradable, temperature-sensitive poly(e-caprolactone-co-lactide)-b-poly(ethylene glycol)-b-poly(e-caprolactone-co-lactide) hydrogel. The MMT–GEM complex and the nanobiohybrid hydrogel were characterized by X-ray diffraction analysis, particle size and zeta potential measurements, Fourier transform infrared spectroscopy, and scanning electron microscopy. Improvements in the properties of nanobiohybrid hydrogel in comparison with the pristine hydrogel were confirmed through sol–gel phase transition diagram, rheological measurement, and in vivo stability. The non-cytotoxicity of the nanobiohybrid hydrogel was proven by MTT assay using the 293T cell line. Compared with the pristine hydrogel, the in vitro GEM release from the nanobiohybrid hydrogel showed a considerably prolonged GEM release time and a much lower initial burst. The antitumor efficacy studies on pancreatic tumor-bearing mice revealed a significant inhibition of tumor growth. Hence, these findings demonstrate that the nanobiohybrid hydrogel is a desirable carrier for controlled release of GEM in the treatment of pancreatic cancer.

Microneedle arrays coated with charge reversal pH-sensitive copolymers improve antigen presenting cells-homing DNA vaccine delivery and immune responses

Abstract Successful delivery of a DNA vaccine to antigen‐presenting cells and their subsequent stimulation of CD4+ and CD8+ T cell immunity remains an inefficient process. In general, the delivery of prophylactic vaccines is mainly mired by low transfection efficacy, poor immunogenicity, and safety issues from the materials employed. Currently, several strategies have been exploited to improve immunogenicity, but an effective strategy for safe and pain‐free delivery of DNA vaccines is complicated. Herein, we report the rapid delivery of polyplex‐based DNA vaccines using microneedle arrays coated with a polyelectrolyte multilayer assembly of charge reversal pH‐responsive copolymer and heparin. The charge reversal pH‐responsive copolymer, composed of oligo(sulfamethazine)‐b‐poly(ethylene glycol)‐b‐poly(amino urethane) (OSM‐b‐PEG‐b‐PAEU), was used as a triggering layer in the polyelectrolyte multilayer assembly on microneedles. Charge reversal characteristics of this copolymer, that is, the OSM‐b‐PEG‐b‐PAEU copolymer exhibit, positive charge at low pH (pH 4.03) and becoming negative charge when exposed to physiological pH conditions (pH 7.4), allowing the facile assembly and disassembly of polyelectrolyte multilayers. The electrostatic repulsion between heparin and OSM‐b‐PEG‐b‐PAEU charge reversal copolymer triggered the release of DNA vaccines. DNA vaccines laden on microneedles are effectively transfected into RAW 264.7 macrophage cells in vitro. Vaccination of BALB/c mice by DNA vaccine‐loaded microneedle arrays coated with a polyelectrolyte multilayer generated antigen‐specific robust immune responses. These findings provide potential strategy of charge reversal pH‐responsive copolymers coated microneedles for DNA vaccine delivery. Graphical abstract Figure. No Caption available.

Injectable hydrogel-incorporated cancer cell-specific cisplatin releasing nanogels for targeted drug delivery

Cisplatin (CDDP) is a well-known anticancer agent, and it has been widely used to treat various solid tumors during clinical cancer therapy. Nevertheless, therapeutic applications of CDDP are hampered by its severe side effects. Although CDDP can be encapsulated into nano-scale drug delivery formulations to improve its physicochemical properties, the lack of stability in the formulation and cancer cell-specific targetability have prompted the exploration of novel vectors for the targeted delivery of CDDP. Here, we introduce CDDP-bearing chondroitin sulfate nanogels (CS-nanogels) that are synthesized through a chelating ligand-metal coordination cross-linking reaction, and then incorporated into pH- and temperature-responsive bioresorbable poly(ethylene glycol)-poly(β-aminoester urethane) (PEG-PAEU) hydrogels for cancer cell-specific delivery of CDDP. The CS-nanogels released from the hydrogels exhibit a pH-dependent release of CDDP. CDDP was released slowly under physiological conditions (pH 7.4), whereas the release of CDDP was triggered under acidic conditions (pH 5.0). Confocal microscopy images demonstrated that fluorescein-5-thiosemicarbazide-labeled CS-nanogels released from the hydrogels selectively bound to the A549 lung carcinoma cell line through the overexpressing CD44 receptor but not to NIH 3T3 cells. An in vitro cytotoxicity test indicated that CS-nanogels released from the hydrogels effectively inhibited the growth of A549 lung carcinoma cells. Subcutaneous injection of CS-nanogel-loaded PEG-PAEU copolymer sols into the dorsal region of Sprague-Dawley rats spontaneously formed a viscoelastic gel without causing noticeable inflammation at the injection site and was found to be bioresorbable in eight weeks. Overall, the injectable hydrogel-incorporated CS-nanogels were demonstrated to be a useful formulation for the targeted delivery of CDDP.

Bioengineered robust hybrid hydrogels enrich the stability and efficacy of biological drugs

ABSTRACT Biological drugs are exquisitely tailored components offering the advantages of high specificity and efficacy that are considered safe for treating diseases. Nevertheless, the effectiveness of biological drugs is limited by their inherent short biological half‐life and poor stability in vivo. Herein, we engineered a novel delivery platform based on hybrid injectable hydrogels, in which pH‐ and temperature‐responsive biodegradable copolymers were site‐specifically coupled to the sulfhydryl group of human serum albumin, which effectively enhances the stability and circulation half‐life of the biological drug, recombinant uricase enzyme (Uox). The albumin ligand conjugated to the Uox allowed specific‐binding of the enzyme within the protein shell, and the synthetic polymers effectively shield the protein‐enzyme complex. Such close confinement exhibits strong resistance towards various physical, chemical and therapeutically relevant stressors such as temperature, pH and proteases. Subcutaneous administration of Uox‐loaded bioengineered hybrid hydrogel improved the pharmacokinetics by prolonging its circulation half‐life. As a consequence, the bioengineered hybrid hydrogel normalized the serum uric acid level in hypoxanthine/potassium oxonate‐induced hyperuricemia mice, and no obvious side effects were observed in the major organs. The characteristic of the bioengineered hydrogel networks applicable to a variety of biological drugs by simple mixing that unlock the possibility of adapting biological drugs to therapeutic applications. Graphical abstract Figure. No caption available.

Smart vaccine delivery based on microneedle arrays decorated with ultra-pH-responsive copolymers for cancer immunotherapy

Despite the tremendous potential of DNA-based cancer vaccines, their efficacious delivery to antigen presenting cells to stimulate both humoral and cellular response remains a major challenge. Although electroporation-based transfection has improved performance, an optimal strategy for safe and pain-free vaccination technique remains elusive. Herein, we report a smart DNA vaccine delivery system in which nanoengineered DNA vaccine was laden on microneedles (MNs) assembled with layer-by-layer coating of ultra-pH-responsive OSM-(PEG-PAEU) and immunostimulatory adjuvant poly(I:C), a synthetic double stranded RNA. Transcutaneous application of MN patches onto the mice skin perforate the stratum corneum with minimal cell damage; subsequent disassembly at the immune-cell-rich epidermis/dermis allows the release of adjuvants and DNA vaccines, owing to the ultra-sharp pH-responsive nature of OSM-(PEG-PAEU). The released adjuvant and DNA vaccine can enhance dendritic cell maturation and induce type I interferons, and thereby produce antigen-specific antibody that can achieve the antibody-dependent cell-mediated cytotoxicity (ADCC) and CD8+ T cell to kill cancer cells. Strikingly, transcutaneous application of smart vaccine formulation in mice elicited 3-fold greater frequencies of Anti-OVA IgG1 serum antibody and 3-fold excess of cytotoxic CD8+ T cell than soluble DNA vaccine formulation. As a consequence, the formulation rejected the murine B16/OVA melanoma tumors in C57BL/6 mice through the synergistic activation of antigen-specific ADCC and cytotoxic CD8+ T cells. The maneuvered use of vaccine and adjuvant poly(I:C) in MNs induces humoral and cellular immunity, which provides a promising vaccine technology that shows improved efficacy, compliance, and safety.

Bioinspired pH- and Temperature-Responsive Injectable Adhesive Hydrogels with Polyplexes Promotes Skin Wound Healing

Despite great potential, the delivery of genetic materials into cells or tissues of interest remains challenging owing to their susceptibility to nuclease degradation, lack of permeability to the cell membrane, and short in vivo half-life, which severely restrict their widespread use in therapeutics. To surmount these shortcomings, we developed a bioinspired in situ-forming pH- and temperature-sensitive injectable hydrogel depot that could control the delivery of DNA-bearing polyplexes for versatile biomedical applications. A series of multiblock copolymer, comprised of water-soluble poly(ethylene glycol) (PEG) and pH- and temperature-responsive poly(sulfamethazine ester urethane) (PSMEU), has been synthesized as in situ-forming injectable hydrogelators. The free-flowing PEG-PSMEU copolymer sols at high pH and room temperature (pH 8.5, 23 °C) were transformed to stable gel at the body condition (pH 7.4, 37 °C). Physical and mechanical properties of hydrogels, including their degradation rate and viscosity, are elegantly controlled by varying the composition of urethane ester units. Subcutaneous administration of free-flowing PEG-PSMEU copolymer sols to the dorsal region of Sprague-Dawley rats instantly formed hydrogel depot. The degradation of the hydrogel depot was slow at the beginning and found to be bioresorbable after two months. Cationic protein or DNA-bearing polyplex-loaded PEG-PSMEU copolymer sols formed stable gel and controlled its release over 10 days in vivo. Owing to the presence of urethane linkages, the PEG-PSMEU possesses excellent adhesion strength to wide range of surfaces including glass, plastic, and fresh organs. More importantly, the hydrogels effectively adhered on human skin and peeled easily without eliciting an inflammatory response. Subcutaneous implantation of PEG-PSMEU copolymer sols effectively sealed the ruptured skin, which accelerated the wound healing process as observed by the skin appendage morphogenesis. The bioinspired in situ-forming pH- and temperature-sensitive injectable adhesive hydrogel may provide a promising platform for myriad biomedical applications as controlled delivery vehicle, adhesive, and tissue regeneration.