Novel gelatin-polyoxometalate based self-assembled pH responsive hydrogels: formulation and in vitro characterization

Development and evaluation of bioinspired pH-responsive sericin-chitosan-based hydrogel for controlled colonic delivery of PETase: Harnessing PETase-triggered degradation of microplastics

The gravity of threats posed by microplastic pollution to the environment cannot be overestimated. Being ubiquitous in the living environment, microplastics reach humans through the food chain causing various hazardous effects. Microplastics can be effectively degraded by PETase enzymes. The current study reports, for the first time, a hydrogel-encapsulated, bioinspired colonic delivery of PETase. A free radical polymerization-assisted hydrogel system was synthesized from sericin, chitosan, and acrylic acid using N,N'-methylenebisacrylamide as a crosslinker and ammonium persulfate as an initiator. The hydrogel was characterized with FTIR, PXRD, SEM, and thermal analysis to confirm the development of a stabilized hydrogel system. The hydrogel showed 61 % encapsulation efficiency, maximum swelling, and cumulative PETase release (96 %) at pH 7.4. The mechanism of PETase release exhibited the Higuchi pattern of release with an anomalous transport mechanism. SDS-PAGE analysis confirmed the preservation of the post-release structural integrity of PETase. The released PETase exhibited concentration- and time-dependent degradation of polyethylene terephthalate in vitro. The developed hydrogel system exhibited the intended features of a stimulus-sensitive carrier system that can be efficiently used for the colonic delivery of PETase.

Polyoxometalate-Containing Supramolecular Gels

Supramolecular gels are important soft materials with various applications, which are fabricated through hydrogen bonding, π-π stacking, electrostatic or host-guest interactions. Introducing functional groups, especially inorganic components, is an efficient strategy to obtain gels with robust architecture and high performance. Polyoxometalates (POMs), as a class of negatively-charged clusters, have defined structures and multiple interaction sites, resulting in their potential as building blocks for constructing POM-containing supramolecular gels. The introduction of POMs into gels not only provides strong driving forces for the formation of gels due to the characteristics of charged cluster and oxygen-rich surface, but also brings new properties sourcing from unique electronic structures of POMs. Though many POM-containing gels have been reported, a comprehensive review is still absent. Herein, the concept of POM-containing gels is discussed, following with the design strategies and driving forces. To better understand the results in the literature, detailed examples, which are classified into several categories based on the types of organic components, are presented to illustrate the gelation process and gel structures. Moreover, applications of POM-containing gels in energy chemistry, sustainable chemistry and other aspects are also reviewed, as well as the future developments of this field. This article is protected by copyright. All rights reserved.

Dual-Crosslinked Dynamic Hydrogel Incorporating {Mo154 } with pH and NIR Responsiveness for Chemo-Photothermal Therapy

Polyoxometalates are an emerging class of molecular clusters, with well-defined structures and chemical compositions that are produced through simple, low-cost, and highly reproducible methods. In particular, the wheel-shaped cluster {Mo154 } is a promising photothermal agent due to its intervalence charge transfer transitions. However, its toxicity hinders its systemic administration, being the development of a localized delivery system still incipient. Herein, an injectable and self-healing hydrogel of easy preparation and administration is developed, incorporating both {Mo154 } and doxorubicin for synergistic photothermal and chemotherapy applications. The hydrogel is composed of benzylaldehyde functionalized polyethylene glycol, poly(N-isopropylacrylamide) functionalized chitosan and {Mo154 }. The gelation occurs within 60 s at room temperature, and the dual crosslinking by Schiff base and electrostatic interactions generates a dynamic network, which enables self-healing after injection. Moreover, the hydrogel delivers chemotherapeutic drugs, with a release triggered by dual near infra-red (NIR) radiation and pH changes. This stimuli-responsive release system along with the photothermal conversion ability of the hydrogel allows the simultaneous combination of photothermal and chemotherapy. This synergic system efficiently ablates the cancer tumor in vivo with no systemic toxicity. Overall, this work paves the way for the development of novel {Mo154 }-based systems, incorporated in self-healing and injectable hydrogels for dual chemo-photothermal therapy.

Gelatin-based hydrogels as potential biomaterials for colonic delivery of oxaliplatin

In present investigation, gelatin-based (AA-co-AMPS) hydrogels were prepared using N, N'-Methylenebisacrylamide (MBA) as a cross-linker and ammonium per sulfate (APS) as an initiator. The successful crosslinking and network formation was confirmed by Fourier transform infrared spectroscopy (FT IR). Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) investigations proved the higher thermal stability and successful entrapment of oxaliplatin (OXP) in the polymeric network. X-ray diffraction (XRD) confirmed the loss in crystallinity of the drug after loading in the hydrogel. Scanning electron microscopy (SEM) revealed the porous surface of the hydrogel. The newly formed hydrogels were responsive to change in pH. The swelling, drug loading and drug release was increased with increase in concentration of acrylic acid (AA) while gelatin and 2-acrylamido 2-methylpronesulfonic acid (AMPS) were found to act inversely. The in-vitro enzymatic degradation study showed that the blank hydrogels were more stable against the blank PBS than the collagenase and lysozyme. MTT-assay proved that the blank hydrogels were cyto-compatible while free OXP as well as OXP-loaded hydrogels showed dose dependent controlled cytotoxicity against Vero, MCF-7 and HCT-116 cell lines. The preliminary safety evaluation and oral tolerability showed that the hydrogel suspension was biocompatible and well tolerable upto 4000 mg/kg of body weight without causing any hematological or histopathological changes in rabbits.

Facile Synthesis of Chitosan Based-(AMPS-co-AA) Semi-IPNs as a Potential Drug Carrier: Enzymatic Degradation, Cytotoxicity, and Preliminary Safety Evaluation

OBJECTIVE

The study describes the development of chitosan-based (AMPS-co-AA) semi-IPN hydrogels using free radical polymerization technique.

METHODS

The resulting hydrogels were characterized using Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), X-Ray diffraction (XRD), and Scanning Electron Microscopy (SEM). The successful crosslinking of chitosan, 2- Acrylamido-2-Methylpropane Sulfonic Acid (AMPS), and Acrylic Acid (AA) was confirmed by FT IR. Unloaded and drug-loaded hydrogels exhibited higher thermal stability after crosslinking compared to the individual components. XRD confirmed the decrease in crystallinity after hydrogel formation and molecular dispersion of Oxaliplatin (OXP) in the polymeric network. SEM showed rough, vague and nebulous surface resulting from crosslinking and loading of OXP.

RESULTS

The experimental results revealed that swelling and drug release were influenced by the pH of the medium being low at acidic pH and higher at basic pH. Increasing the concentration of chitosan and AA enhanced the swelling, drug loading and drug release while AMPS was found to act inversely.

CONCLUSION

It was confirmed that the hydrogels were degraded more by specific enzyme lysozyme as compared to the non-specific enzyme collagenase. In-vitro cytotoxicity suggested that the unloaded hydrogels were non-cytotoxic while crude drug and drug-loaded hydrogel exhibited dose-dependent cytotoxicity against HCT-116 and MCF-7. Results of acute oral toxicity on rabbits demonstrated that the hydrogels are non-toxic up to 3900 mg/kg after oral administration, as no toxicity or histopathological changes were observed in comparison to control rabbits. These pH-sensitive hydrogels appear to provide an ideal basis as a safe carrier for oral drug delivery.

Elastomeric and pH-responsive hydrogels based on direct crosslinking of the poly(glycerol sebacate) pre-polymer and gelatin

The synthesis and biomedical applications of novel elastomeric, pH-responsive, biocompatible and biodegradable copolymer hydrogels based on poly(glycerol sebacate) and gelatin.