Near-infrared light-responsive alginate hydrogels based on diselenide-containing cross-linkage for on demand degradation and drug release

Berberine carried gelatin/sodium alginate hydrogels with antibacterial and EDTA-induced detachment performances

Most existing hydrogel wound dressings lack gentle detachment property. In this work, novel hydrogels with anti-bacterial and induced detachment properties were prepared. Both gelatin (G) and sodium alginate (SA) are natural polymer materials. The G/SA hydrogels were prepared by dual cross-linking. The addition of SA significantly improves the mechanical properties of composite hydrogels. The tensile modulus and elongation at break of the G/SA hydrogels with 2.0% SA could reach 99.23 ± 2.18 kPa and 85.47 ± 5.01%, respectively. In addition, the interconnected porous network and high swelling ratio (over 9.99 ± 0.33) are beneficial to the transmission of oxygen and absorption of exudates to accelerate the healing of wound. Subsequently, berberine (BBR) was loaded into the G/SA hydrogels. The BBR/G/SA hydrogels show sustained drug release for 168 h and exhibit anti-bacterial effect against Staphylococcus aureus. The results of L929 cells cultured with the hydrogel extracts indicate good biocompatibility. Finally, results of EDTA-induced detachment performances demonstrate that the hydrogels could be removed from the wound as the internal structure destroyed. All illustrated results above demonstrated the BBR carried G/SA hydrogels have potential used as wound dressing materials in future.

Recent Development of Alginate-Based Materials and Their Versatile Functions in Biomedicine, Flexible Electronics, and Environmental Uses

Alginate is a natural polysaccharide that is easily chemically modified or compounded with other components for various types of functionalities. The alginate derivatives are appealing not only because they are biocompatible so that they can be used in biomedicine or tissue engineering but also because of the prospering bioelectronics that require various biomaterials to interface between human tissues and electronics or to serve as electronic components themselves. The study of alginate-based materials, especially hydrogels, have repeatedly found new frontiers over recent years. In this Review, we document the basic properties of alginate, their chemical modification strategies, and the recent development of alginate-based functional composite materials. The newly thrived functions such as ionically conductive hydrogel or 3D or 4D cell culturing matrix are emphasized among other appealing potential applications. We expect that the documentation of relevant information will stimulate scientific efforts to further develop biocompatible electronics or smart materials and to help the research domain better address the medicine, energy, and environmental challenges faced by human societies.

Near-infrared photothermal liposomal nanoantagonists for amplified cancer photodynamic therapy

Photodynamic therapy (PDT) has been demonstrated to be a promising strategy for the treatment of cancer, while its therapeutic efficacy is often compromised due to excessive concentrations of glutathione (GSH) as a reactive oxygen species (ROS) scavenger in cancer cells. Herein, we report the development of near-infrared (NIR) photothermal liposomal nanoantagonists (PLNAs) for amplified PDT through through the reduction of intracellular GSH biosynthesis. Such PLNAs were constructed via encapsulating a photosensitizer, indocyanine green (ICG) and a GSH synthesis antagonist, l-buthionine sulfoximine (BSO) into a thermal responsive liposome. Under NIR laser irradiation at 808 nm, PLNAs generate mild heat via a ICG-mediated photothermal conversion effect, which leads to the destruction of thermal responsive liposomes for a controlled release of BSO in a tumor microenvironment, ultimately reducing GSH levels. This amplifies intracellular oxidative stresses and thus synergizes with PDT to afford an enhanced therapeutic efficacy. Both in vitro and in vivo data verify that PLNA-mediated phototherapy has an at least 2-fold higher efficacy in killing cancer cells and inhibiting tumor growth compared to sole PDT. This study thus demonstrates a NIR photothermal drug delivery nanosystem for amplified photomedicine.

An On-Demand Dissoluble Chitosan Hydrogel Containing Dynamic Diselenide Bond

A new kind of on-demand dissolution hydrogel is successfully synthesized by modification of chitosan using γ-selenobutyrolactone. The chitosan hydrogel with different selenium contents is formed by ring opening of γ-selenobutyrolactone with the amines of D-glucosamine units on the chitosan backbone. The structure of the hydrogel was confirmed by 1H NMR, XRD and XPS. Its physical and biological properties were evaluated by rheology characterization, degradation tests and cytotoxicity test. The hydrogel showed excellent biocompatibility and good degradation properties under oxidation or reduction conditions. All the evidence demonstrated that this type of material has good prospects for dressing applications.

A Review of Polysaccharide-Zinc Oxide Nanocomposites as Safe Coating for Fruits Preservation

Safe coating formulated from biopolymer can be an alternative for better packaging for fruits. Among biopolymers used for safe coating, polysaccharides attracted more attention due to its biocompatibility and edibility. However, polysaccharide-based materials have weaknesses such as low water barrier and mechanical properties which result in lower capability on preserving the coated fruits. Hence, the incorporation of nanoparticles (NPs) such as zinc oxide (ZnO) is expected to increase the ability of polysaccharide-based coating for the enhancement of fruit shelf life. In this review paper, the basic information and the latest updates on the incorporation of ZnO NPs into the polysaccharide-based safe coating for fruit are presented. Various research has investigated polysaccharide-ZnO nanocomposite safe coating to prolong the shelf life of fruits. The polysaccharides used include chitosan, alginate, carrageenan, cellulose, and pectin. Overall, polysaccharide-ZnO nanocomposites can improve the shelf life of fruits by reducing weight loss, maintaining firmness, reducing the ripening process, reducing respiration, reducing the oxidation process, and inhibiting microbial growth. Finally, the challenges and potential of ZnO NPs as an active agent in the safe coating application are also discussed.

On-Demand Dissoluble Diselenide-Containing Hydrogel

On-demand dissolution of hydrogels is being increasingly studied for their potential use in burn wound dressing applications. Herein, a dynamic diselenide-containing hydrogel is developed through a very simple one-pot and two-step process starting from the selenol functionalization of a partially hydrolyzed poly(2-ethyl-2-oxazoline) with γ-butyroselenolactone. The hydrogel spontaneously cross-links via an in situ oxidation of the selenol functionalities in air. The gelation process and the final viscoelastic properties of the gel are characterized by rheological experiments. The mechanical properties of those new diselenide-containing hydrogels are easily tuned by varying the concentration of γ-butyroselenolactone. The materials also show good skin adhesion and UV light responsiveness. A unique feature of the hydrogel is its capability to be fully and rapidly dissolved on-demand, via oxidation or reduction of the diselenide cross-links, making them particularly attractive for burn wound dressing applications.

Structural reorganization and crack-healing properties of hydrogels based on dynamic diselenide linkages

We report the dynamic behavior of diselenide-containing hydrophilic polyurethanes and hydrogels based on diselenide exchange reactions in an aqueous media. Diselenide-containing linear and cross-linked polyurethanes were synthesized via polyaddition reactions using diselenide-containing diol in combination with pyridinium diol that enhances the hydrophilicity of the polymer chains. The obtained linear polyurethanes underwent photo-induced diselenide exchange reactions with small diselenide compounds and degraded to smaller fragments, confirming the dynamicity of the obtained hydrophilic polyurethanes. The prepared hydrogels displayed characteristic large swelling behavior based on the structural reorganization through diselenide exchange either under photo-irradiation at 365 nm or even in the dark at room temperature. The diselenide-containing hydrogels also showed crack-healing behavior under the same exchanging conditions, presenting the utility of diselenide linkages as simple and useful units to offer high dynamicity to hydrogels.

Construction of functional curdlan hydrogels with bio-inspired polydopamine for synergistic periodontal antibacterial therapeutics

Curdlan, a bacteria-derived polysaccharide resource, possesses substantial potential for periodontal antimicrobial delivery. Here, the facile engineering of a functionalized curdlan/polydopamine (PDA) composite hydrogels was reported. The physiochemical evaluations of composite hydrogels proved their tunable properties associated with concentration of PDA including pore size, rheological property and swelling behavior. We have systematically assessed biocompatibility in vitro and found these hydrogels toxicity-free. Moreover, photothermal performance upon near infrared light (NIR) exposure was conducted and eventually indicated the best matches for antibacterial application. The acetate chlorhexidine (CHX) was chosen as a model antimicrobial and the release profiles demonstrated the entrapped CHX could be triggered and nicely controlled by NIR. The optimized bacteriostatic rate reached 99.9 %. Overall, we aimed to provide new curdlan-based hydrogels for periodontal antibacterial treatment by combining photothermal effect and antimicrobial simultaneously.

Stimuli-Responsive Hydrogels for Local Post-Surgical Drug Delivery

Currently, surgical operations, followed by systemic drug delivery, are the prevailing treatment modality for most diseases, including cancers and trauma-based injuries. Although effective to some extent, the side effects of surgery include inflammation, pain, a lower rate of tissue regeneration, disease recurrence, and the non-specific toxicity of chemotherapies, which remain significant clinical challenges. The localized delivery of therapeutics has recently emerged as an alternative to systemic therapy, which not only allows the delivery of higher doses of therapeutic agents to the surgical site, but also enables overcoming post-surgical complications, such as infections, inflammations, and pain. Due to the limitations of the current drug delivery systems, and an increasing clinical need for disease-specific drug release systems, hydrogels have attracted considerable interest, due to their unique properties, including a high capacity for drug loading, as well as a sustained release profile. Hydrogels can be used as local drug performance carriers as a means for diminishing the side effects of current systemic drug delivery methods and are suitable for the majority of surgery-based injuries. This work summarizes recent advances in hydrogel-based drug delivery systems (DDSs), including formulations such as implantable, injectable, and sprayable hydrogels, with a particular emphasis on stimuli-responsive materials. Moreover, clinical applications and future opportunities for this type of post-surgery treatment are also highlighted.

Immobilization of algicidal bacterium Shewanella sp. IRI-160 and its application to control harmful dinoflagellates

Shewanella sp. IRI-160 is an algicidal bacterium isolated from Delaware Inland Bays. It secretes water-soluble compounds that inhibit the growth of dinoflagellates. Previous research indicated that this bacterium does not have a negative impact on other algal species. In this research, Shewanella sp. IRI-160 was immobilized to different porous matrices, including agarose, alginate hydrogel, cellulosic sponge, and polyester foam. The retention of Shewanella sp. IRI-160 on or within these matrices was examined at 4 and 25 °C for 12 days. Results indicated that alginate was superior in terms of cell retention, with >99% of Shewanella cells retained in the matrix after 12 days. Shewanella sp. IRI-160 cells were then immobilized within alginate beads to evaluate algicidal effects on harmful dinoflagellates Karlodinium veneficum and Prorocentrum minimum at bacterial concentrations of 10⁶ to 10⁸ cells mL^-1. The effects on dinoflagellates were compared to non-harmful cryptophyte Rhodomonas sp., as well as the effects of free-living bacteria on these species. Results indicated that immobilized Shewanella sp. IRI-160 in alginate beads were as effective as the free-living bacteria to control the growth of K. veneficum and P. minimum, while no negative impacts of immobilized Shewanella sp. IRI-160 on the non-harmful control species Rhodomonas sp. were observed. Overall, this study suggests that immobilized Shewanella sp. IRI-160 may be used as an environmentally friendly approach to prevent or mitigate the blooms of harmful dinoflagellates and provides insight and directions for future studies.