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

Therapeutic-Gas-Responsive Hydrogel

Nitric oxide (NO) is a crucial signaling molecule with various functions in physiological systems. Due to its potent biological effect, the preparation of responsive biomaterials upon NO having temporally transient properties is a challenging task. This study represents the first therapeutic-gas (i.e., NO)-responsive hydrogel by incorporating a NO-cleavable crosslinker. The hydrogel is rapidly swollen in response to NO, and not to other gases. Furthermore, the NO-responsive gel is converted to enzyme-responsive gels by cascade reactions from an enzyme to NO production for which the NO precursor is a substrate of the enzyme. The application of the hydrogel as a NO-responsive drug-delivery system is proved here by revealing effective protein drug release by NO infusion, and the hydrogel is also shown to be swollen by the NO secreted from the cultured cells. The NO-responsive hydrogel may prove useful in many applications, for example drug-delivery vehicles, inflammation modulators, and as a tissue scaffold.

Engineering highly swellable dual-responsive protein-based injectable hydrogels: the effects of molecular structure and composition in vivo

Stimuli-responsive hydrogels, known as smart hydrogels, are three-dimensional amphiphilic or hydrophilic polymer networks that are able to change their volume or phase, and other properties, including viscosity, structure, and dimension, in response to changes in pH, temperature, and magnetic or electric field. Highly swellable, dual-responsive bovine serum albumin (BSA)-based injectable hydrogels are prepared here by the chemical conjugation of pH- and temperature-responsive oligo(sulfamethazine acrylate-co-N-isopropylacrylamide) (oligo(SMA-co-NIPAM)) copolymers on the surface of BSA through carbodiimide-mediated chemistry. The pH- and temperature-responsive oligomer-bearing BSA conjugates show rapid sol-to-gel phase transition properties. Specifically, the free-flowing conjugates at high pH (pH 8.4, 23 °C) are transformed to a viscoelastic gel under physiological conditions (pH 7.4, 37 °C). The swelling ratio, gel strength, and pore size of the BSA hydrogel were tuned by altering the conjugation ratio of the oligo(SMA-co-NIPAM) copolymers of various lengths and compositions to BSA. Subcutaneously administered BSA conjugate sols into the dorsal region of Sprague-Dawley rats formed an in situ gel. When the oligo(NIPAM) content in the hydrogel was high, the degradation rate of BSA hydrogels was remarkably slow, and two weeks after in vivo administration, the hydrogels with high oligo(NIPAM) had swollen more than 4-fold. An in vivo biodegradation study demonstrated that no necrosis or hemorrhage was observed in the tissues with the hydrogels. The concurrent stimuli-responsivity under physiological conditions and high elasticity suggest that these smart hydrogels may open a new avenue for hydrogel applications.

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.

Injectable in situ cross-linking chitosan-hyaluronic acid based hydrogels for abdominal tissue regeneration

Abdominal wall defect caused by open abdomen (OA) or abdominal trauma is a serious issue since it induces several clinical problems. Although a variety of prosthetic materials are commonly employed, complications occur including host soft tissue response, fistula formation and chronic patient discomfort. Recently, abundant natural polymers have been used for injectable hydrogel synthesis in tissue regeneration. In this study, we produced the chitosan - hyaluronic acid (CS/HA) hydrogel and investigated its effects on abdominal tissue regeneration. The physical and biological properties of the hydrogel were demonstrated to be suitable for application in abdominal wounds. In a rat model simulating open abdomen and large abdominal wall defect, rapid cellular response, sufficient ECM deposition and marked neovascularization were found after the application of the hydrogel, compared to the control group and fibrin gel group. Further, the possible mechanism of these findings was studied. Cytokines involved in angiogenesis and cellular response were increased and the skew toward M2 macrophages credited with the functions of anti-inflammation and tissue repair was showed in CS/HA hydrogel group. These findings suggested that CS/HA hydrogel could prevent the complications and was promising for abdominal tissue regeneration.

Perspective highlights on biodegradable polymeric nanosystems for targeted therapy of solid tumors

Introduction: Polymeric nanoparticles (NPs) formulated using biodegradable polymers offer great potential for development of de novo drug delivery systems (DDSs) capable of delivering a wide range of bioactive agents. They can be engineered as advanced multifunctional nanosystems (NSs) for simultaneous imaging and therapy known as theranostics or diapeutics.

Methods: A brief prospective is provided on biomedical importance and applications of biodegradable polymeric NSs through reviewing the recently published literature.

Results: Biodegradable polymeric NPs present unique characteristics, including: nanoscaled structures, high encapsulation capacity, biocompatibility with non-thrombogenic and non-immunogenic properties, and controlled-/sustained-release profile for lipophilic and hydrophilic drugs. Once administered in vivo, all classes of biodegradable polymers (i.e., synthetic, semi-synthetic, and natural polymers) are subjected to enzymatic degradation; and hence, transformation into byproducts that can be simply eliminated from the human body. Natural and semi-synthetic polymers have been shown to be highly stable, much safer, and offer a non-/less-toxic means for specific delivery of cargo drugs in comparison with synthetic polymers. Despite being biocompatible and enzymatically-degradable, there are some drawbacks associated with these polymers such as batch to batch variation, high production cost, structural complexity, lower bioadhesive potential, uncontrolled rate of hydration, and possibility of microbial spoilage. These pitfalls have bolded the importance of synthetic counterparts despite their somewhat toxicity.

Conclusion: Taken all, to minimize the inadvertent effects of these polymers and to engineer much safer NSs, it is necessary to devise biopolymers with desirable chemical and biochemical modification(s) and polyelectrolyte complex formation to improve their drug delivery capacity in vivo.

AgNP and rhEGF-incorporating synergistic polyurethane foam as a dressing material for scar-free healing of diabetic wounds

Synergistic polyurethane foams comprised of AgNPs and rhEGF (AgNP/rhEGF-PUFs) were developed to treat diabetic wounds, which exhibited complete wound closure.

pH-Sensitive sulfamethazine-based hydrogels as potential embolic agents for transcatheter vascular embolization

After delivery through a catheter, a three-dimensional hydrogel network was formed upon the change of environmental pH, and thus block the targeted blood vessels, as presented in white color under the fluoroscopic angiogram.