In situ hydrogel constructed by starch-based nanoparticles via a Schiff base reaction

Biomimetic Nanozyme-Decorated Smart Hydrogel for Promoting Chronic Refractory Wound Healing

Chronic refractory wounds have become a serious threat to human health and are characterized by prolonged inflammation, recurrent bacterial infections, and elevated ROS levels. However, current therapeutic strategies usually target a unilateral healing function and are unable to tackle the complexity and sensitivity of chronic refractory wound healing. This study fabricated a biomimetic nanozyme based on rhein (Cu-rhein NSs), which effectively mimics the activity of superoxide dismutase (SOD) for scavenging various free radicals. Additionally, zinc oxide microspheres (ZnO MSs) were prepared to enhance the antibacterial activity and mechanical properties of the modified hydrogel. Cu-rhein NSs and ZnO MSs were comodified onto an extracellular matrix-mimetic dual-network smart hydrogel constructed from oxidized sodium alginate, gelatin, and borax via dynamic borate and Schiff base bonds. The smart hydrogel presented the good biocompatibility and targeted the unique acidic microenvironment with high oxidative stress of chronic refractory wounds, intelligently releasing bionic nanozymes to effectively eliminate bacteria, reduce inflammatory responses, and scavenge multiple free radicals for reducing ROS. In vivo experiments on the rat model based on diabetic infection showed that the smart hydrogel could effectively eliminate bacteria, promote vascular regeneration and collagen deposition, reduce inflammatory response, and accelerate the healing of diabetic-infected wounds (almost complete healing within 14 days). The advantages of an intelligent, biomimetic tissue regeneration cascade management strategy against diabetic infected wound healing are highlighted.

Oxidation-induced starch molecular degradation: A comprehensive kinetic investigation using NaClO/NaBr/TEMPO system

Starch degradation often coincides with its chemical modification, and understanding how chemical modification influences starch degradation is vital for determining the properties of the resultant modified products. This work investigates the effect of oxidation on starch molecular degradation, examining factors such as oxidation degree, reaction kinetics, and degradation patterns during 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated starch oxidation under varying conditions, including reaction time, pH, temperature, and concentrations of NaBr, TEMPO, and NaClO. Results emphasize that extended reaction durations primarily lead to β-elimination, causing α-1,4 linkage cleavages. pH 8.5 favored non-selective oxidation, while pH 11 enhanced β-elimination, both slowing the reaction rate and severely damaging starch chains (Mw of 8.8 × 105 g/mol and 7.2 × 105 g/mol, respectively). Elevated temperature from 0 to 30 °C significantly expedited both selective and non-selective oxidation, dramatically reducing molecular mass to 8.1 × 105 g/mol. Increasing concentrations of NaBr and TEMPO boost the reaction rate with minimal impact on molecular mass. Meanwhile, increasing NaClO concentration from 0.2 to 2.2 mmol/g-starch not only affects the reaction rate but also reinforces β-elimination, enhancing molecular degradation. This study is insightful for starch modification to achieve desired oxidation levels and chain lengths by controlling reaction conditions, offering potential advancements in oxidized starch-based materials like nano micelles.

Facile preparation of interpenetrating network hydrogel adsorbent from starch- chitosan for effective removal of methylene blue in water

Hydrogels based on biopolymers have attracted considerable interest in the last decades. Herein, an interpenetrating network hydrogel (IPN-Gel) adsorbent from starch-chitosan was fabricated facilely in one-pot through tandem Schiff base reaction and photopolymerization. First, aldehyde starch (DAS) was synthesized by the reaction of soluble starch with sodium periodate. Afterward, acrylamide (AM), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), polyethylene glycol dimethacrylate (PEGDMA), photoinitiator, chitosan and DAS were dissolved in water to obtain a clear solution. Schiff base reaction between chitosan and DAS took place quickly to form the first network, and then photopolymerization of AM, AMPS, and PEGDMA occurred under ultraviolet radiation to form the second network. The preparation conditions of the as-prepared IPN-Gel were optimized with two indexes of gel mass fraction and swelling ratio. Its swelling behavior with pH and temperature change was explored. Finally, its adsorption performance was characterized with methylene blue (MB) as a model contaminant. The maximum adsorption capacity of IPN-Gel can reach 2039 mg·g-1 at pH =10. Its adsorption performance accords with Langmuir isothermal model and pseudo-second-order kinetic model and it was mainly controlled by chemisorption. This strategy is expected to found broad application prospects in the preparation of hydrogel adsorbents.

Trends in sustainable chitosan-based hydrogel technology for circular biomedical engineering: A review

Eco-friendly materials have emerged in biomedical engineering, driving major advances in chitosan-based hydrogels. These hydrogels offer a promising green alternative to conventional polymers due to their non-toxicity, biodegradability, biocompatibility, environmental friendliness, affordability, and easy accessibility. Known for their remarkable properties such as drug encapsulation, delivery capabilities, biosensing, functional scaffolding, and antimicrobial behavior, chitosan hydrogels are at the forefront of biomedical research. This paper explores the fabrication and modification methods of chitosan hydrogels for diverse applications, highlighting their role in advancing climate-neutral healthcare technologies. It reviews significant scientific advancements and trends chitosan hydrogels focusing on cancer diagnosis, drug delivery, and wound care. Additionally, it addresses current challenges and green synthesis practices that support a circular economy, enhancing biomedical sustainability. By providing an in-depth analysis of the latest evidence on climate-neutral management, this review aims to facilitate informed decision-making and foster the development of sustainable strategies leveraging chitosan hydrogel technology. The insights from this comprehensive examination are pivotal for steering future research and applications in sustainable biomedical solutions.

Hydrogels Based on Proteins Cross-Linked with Carbonyl Derivatives of Polysaccharides, with Biomedical Applications

Adding carbonyl groups into the hydrogel matrix improves the stability and biocompatibility of the hydrogels, making them suitable for different biomedical applications. In this review article, we will discuss the use of hydrogels based on polysaccharides modified by oxidation, with particular attention paid to the introduction of carbonyl groups. These hydrogels have been developed for several applications in tissue engineering, drug delivery, and wound healing. The review article discusses the mechanism by which oxidized polysaccharides can introduce carbonyl groups, leading to the development of hydrogels through cross-linking with proteins. These hydrogels have tunable mechanical properties and improved biocompatibility. Hydrogels have dynamic properties that make them promising biomaterials for various biomedical applications. This paper comprehensively analyzes hydrogels based on cross-linked proteins with carbonyl groups derived from oxidized polysaccharides, including microparticles, nanoparticles, and films. The applications of these hydrogels in tissue engineering, drug delivery, and wound healing are also discussed.

A Comprehensive Review of Hydrogel-Based Drug Delivery Systems: Classification, Properties, Recent Trends, and Applications

As adaptable biomaterials, hydrogels have shown great promise in several industries, which include the delivery of drugs, engineering of tissues, biosensing, and regenerative medicine. These hydrophilic polymer three-dimensional networks have special qualities like increased content of water, soft, flexible nature, as well as biocompatibility, which makes it excellent candidates for simulating the extracellular matrix and promoting cell development and tissue regeneration. With an emphasis on their design concepts, synthesis processes, and characterization procedures, this review paper offers a thorough overview of hydrogels. It covers the various hydrogel material types, such as natural polymers, synthetic polymers, and hybrid hydrogels, as well as their unique characteristics and uses. The improvements in hydrogel-based platforms for controlled drug delivery are examined. It also looks at recent advances in bioprinting methods that use hydrogels to create intricate tissue constructions with exquisite spatial control. The performance of hydrogels is explored through several variables, including mechanical properties, degradation behaviour, and biological interactions, with a focus on the significance of customizing hydrogel qualities for particular applications. This review paper also offers insights into future directions in hydrogel research, including those that promise to advance the discipline, such as stimuli-responsive hydrogels, self-healing hydrogels, and bioactive hydrogels. Generally, the objective of this review paper is to provide readers with a detailed grasp of hydrogels and all of their potential uses, making it an invaluable tool for scientists and researchers studying biomaterials and tissue engineering.

Effective wound healing on diabetic mice by adhesive antibacterial GNPs-lysine composited hydrogel

Current trends in wound care research focus on creating dressings for diverse wound types, aiming to effectively control the wound healing process. We proposed a wound dressing composed of oxidized hyaluronic acid and amine gelatin with embedded lysine-modified gelatin nanoparticles (HGel-GNPs-lysine). This dressing improves mechanical properties and reduces degradation rates. The storage modulus for HGel-GNPs-lysine was 3,800 Pa, exceeding that of HGel (1,750 Pa). The positively charged surface of GNPs-lysine effectively eliminated Escherichia coli and Staphylococcus aureus. In a diabetic mice model (C57BL/6), HGel-GNPs-lysine immobilized with basic-fibroblast growth factor promoted granulation tissue thickness and collagen density. Gene expression analysis indicated that HGel-GNPs-lysine reduced inflammation and enhanced angiogenesis. This study highlights that HGel-GNPs-lysine could offer alternative treatment strategies for regulating the inflammatory response at the injury site in wound dressing applications.

Green Synthesis of Low-Glycemic Amylose-Lipid Nanocomposites by High-Speed Homogenization and Formulation into Hydrogel

In this research, we focused on the production of amylose-lipid nanocomposite material (ALN) through a green synthesis technique utilizing high-speed homogenization. Our aim was to investigate this novel material's distinctive physicochemical features and its potential applications as a low-glycemic gelling and functional food ingredient. The study begins with the formulation of the amylose-lipid nanomaterial from starch and fatty acid complexes, including stearic, palmitic, and lauric acids. Structural analysis reveals the presence of ester carbonyl functionalities, solid matrix structures, partial crystallinities, and remarkable thermal stability within the ALN. Notably, the ALN exhibits a significantly low glycemic index (GI, 40%) and elevated resistance starch (RS) values. The research extends to the formulation of ALN into nanocomposite hydrogels, enabling the evaluation of its anthocyanin absorption capacity. This analysis provides valuable insights into the rheological properties and viscoelastic behavior of the resulting hydrogels. Furthermore, the study investigates anthocyanin encapsulation and retention by ALN-based hydrogels, with a particular focus on the influence of pH and physical cross-link networks on the uptake capacity presenting stearic-acid (SA) hydrogel with the best absorption capacity. In conclusion, the green-synthesized (ALN) shows remarkable functional and structural properties. The produced ALN-based hydrogels are promising materials for a variety of applications, such as medicine administration, food packaging, and other industrial purposes.

Polysaccharide-based nanoassemblies: From synthesis methodologies and industrial applications to future prospects

Polysaccharides, due to their remarkable features, have gained significant prominence in the sustainable production of nanoparticles (NPs). High market demand and minimal production cost, compared to the chemically synthesised NPs, demonstrate a drive towards polysaccharide-based nanoparticles (PSNPs) benign to environment. Various approaches are used for the synthesis of PSNPs including cross-linking, polyelectrolyte complexation, and self-assembly. PSNPs have the potential to replace a wide diversity of chemical-based agents within the food, health, medical and pharmacy sectors. Nevertheless, the considerable challenges associated with optimising the characteristics of PSNPs to meet specific targeting applications are of utmost importance. This review provides a detailed compilation of recent accomplishments in the synthesis of PSNPs, the fundamental principles and critical factors that govern their rational fabrication, as well as various characterisation techniques. Noteworthy, the multiple use of PSNPs in different disciplines such as biomedical, cosmetics agrochemicals, energy storage, water detoxification, and food-related realms, is accounted in detail. Insights into the toxicological impacts of the PSNPs and their possible risks to human health are addressed, and efforts made in terms of PSNPs development and optimising strategies that allow for enhanced delivery are highlighted. Finally, limitations, potential drawbacks, market diffusion, economic viability and future possibilities for PSNPs to achieve widespread commercial use are also discussed.

Enhanced Osteogenesis Potential of MG-63 Cells through Sustained Delivery of VEGF via Liposomal Hydrogel

The challenges of using VEGF to promote osteoblastic differentiation include a short half-life and a narrow therapeutic window. A carrier system combining hydrogel and liposomes may improve the therapeutic efficacy of VEGF for bone regeneration. This study aimed to investigate the effects of delivery of VEGF via liposomal hydrogel on the osteogenesis of MG-63 cells. Liposomal hydrogel scaffold was fabricated and then characterized in terms of the morphological and chemical properties using FESEM and FTIR. In 2.5D analysis, the MG-63 cells were cultured on liposomal hydrogel + VEGF as the test group. The osteogenic effects of VEGF were compared with the control groups, i.e., hydrogel without liposomes + VEGF, osteogenic medium (OM) supplemented with a bolus of VEGF, and OM without VEGF. Cell morphology, viability, and differentiation and mineralization potential were investigated using FESEM, MTT assay, ALP activity, and Alizarin red staining. The characterization of scaffold showed no significant differences in the morphological and chemical properties between hydrogel with and without liposomes (p > 0.05). The final 2.5D culture demonstrated that cell proliferation, differentiation, and mineralization were significantly enhanced in the liposomal hydrogel + VEGF group compared with the control groups (p < 0.05). In conclusion, liposomal hydrogel can be used to deliver VEGF in a sustained manner in order to enhance the osteogenesis of MG-63 cells.

Immunoinducible Carbon Dot-Incorporated Hydrogels as a Photothermal-Derived Antigen Depot to Trigger a Robust Antitumor Immune Response

Immunogenic tumor cell death (ICD) induced by photothermal therapy (PTT) fails to elicit a robust antitumor immune response partially due to its inherent immunosuppressive microenvironment and poor antigen presentation. To address these issues, we developed an immunoinducible carbon dot-incorporated hydrogel (iCD@Gel) through a dynamic covalent Schiff base reaction using mannose-modified aluminum-doped carbon dots (M/A-CDs) as a cross-linking agent. The M/A-CDs possessed superior photothermal conversion efficiency and served as nanocarriers to load cytosine-phosphate-guanine oligodeoxynucleotides (CpG ODNs) for inducing the maturation of dendritic cells (DCs) via mannose receptor-mediated targeting delivery. Upon intratumoral injection, the as-prepared iCD@Gel induced ICD, and damage-associated molecular patterns (DAMPs) were released via photothermal ablation under 808 nm NIR irradiation. Subsequently, the iCD@Gel synergized with the DAMPs to significantly promote the maturation and antigen cross-presentation ability of DCs. This work provides a promising strategy to develop carbon dot-based therapeutic hydrogels for photothermal therapy and immune activation.

Are Natural Compounds a Promising Alternative to Synthetic Cross-Linking Agents in the Preparation of Hydrogels?

The main aim of this review is to assess the potential use of natural cross-linking agents, such as genipin, citric acid, tannic acid, epigallocatechin gallate, and vanillin in preparing chemically cross-linked hydrogels for the biomedical, pharmaceutical, and cosmetic industries. Chemical cross-linking is one of the most important methods that is commonly used to form mechanically strong hydrogels based on biopolymers, such as alginates, chitosan, hyaluronic acid, collagen, gelatin, and fibroin. Moreover, the properties of natural cross-linking agents and their advantages and disadvantages are compared relative to their commonly known synthetic cross-linking counterparts. Nowadays, advanced technologies can facilitate the acquisition of high-purity biomaterials from unreacted components with no additional purification steps. However, while planning and designing a chemical process, energy and water consumption should be limited in order to reduce the risks associated with global warming. However, many synthetic cross-linking agents, such as N,N'-methylenebisacrylamide, ethylene glycol dimethacrylate, poly (ethylene glycol) diacrylates, epichlorohydrin, and glutaraldehyde, are harmful to both humans and the environment. One solution to this problem could be the use of bio-cross-linking agents obtained from natural resources, which would eliminate their toxic effects and ensure the safety for humans and the environment.

Multifunctional all-in-one adhesive hydrogel for the treatment of perianal infectious wounds

Postoperative wound of perianal infectious disease represents a common but unique refractory wound in clinical practice. The reasons that hinder the wound healing process include not only the severe bacterial infection of the wound itself and the narrow and deep shape of the wound, but also its frequent bacterial contact. Therefore, the development of biofunctional dressings to aid in therapy is essential. In this study, we synthesized a new type of dressing comprising a hydrogel host based on the Schiff base principle and catechol groups between polydopamine, oxidized dextran, and quaternized chitosan, and then loaded it with traditional Chinese medicine molecules. These formed an integrated hydrogel for accelerated wound repair in a perianal infection model. The prepared hydrogels exhibited excellent wet tissue adhesion, antifouling, morphological variability, suitable swelling properties, and complete degradability, as well as remarkable contact antibacterial ability and the ability to rapidly scavenge free radicals. Hemostatic experiments showed excellent hemostatic properties, as the integrated hydrogel could instantly gel to seal the hemorrhage. Hemocompatibility and in vitro cell experiments showed that the integrated hydrogel had good biosafety and significantly promoted cell proliferation, which in turn accelerated the repair of infected whole cortexes in rats. A histomorphological evaluation showed that the integrated hydrogel promoted the recovery of normal anatomical tissue in rats by promoting the formation of collagen fibers and inhibiting inflammation. The results showed that this multifunctional integrated hydrogel has great potential for the treatment of continuously infected skin regeneration, providing a promising therapeutic strategy for postoperative wound healing in perianal infectious diseases.

Hofmeister effect-enhanced gelatin/oxidized dextran hydrogels with improved mechanical properties and biocompatibility for wound healing

Compared with other types of hydrogels, natural derived hydrogels possess intrinsic advantages of degradability and biocompatibility. However, due to the low mechanical strength, their potential applications in biomedical areas are limited. In this study, Hofmeister effect-enhanced gelatin/oxidized dextran (Gel/O-Dex) hydrogels were designed with improved mechanical properties and biocompatibility to accelerate wound healing. Gel and O-Dex were chemically crosslinked through Schiff base reaction of aldehyde and amino groups. After soaking in kosmotrope solutions physical crosslinking domains were induced by Hofmeister effect including α-helix structures, hydrophobic interaction regions and helical junction zones among Gel molecular chains. The type of anions played different influence on the properties of hydrogels, which was consistent with the order of Hofmeister series. Particularly, H₂PO₄^- treated hydrogels showed enhanced mechanical strength and fatigue resistance superior to that of Gel/O-Dex hydrogels. The underlying mechanism was that the physical crosslinking domains sustained additional mechanical stress and dissipated energy through cyclic association and dissociation process. Furthermore, Hofmeister effect only induced polymer chain entanglements without triggering any chemical reaction. Due to Hofmeister effect of H₂PO₄^- ions, aldehyde groups were embedded in the center of entangled polymer chains that resulted in better biocompatibility. In the full-thickness skin defects of SD rats, Hofmeister effect-enhanced Gel/O-Dex hydrogels by H₂PO₄^- ions accelerated wound healing and exhibited better histological morphology than ordinary hydrogels. Therefore, Hofmeister effect by essential inorganic anions is a promising method of improving mechanical properties and biocompatibility of natural hydrogels to promote medical translation in the field of wound healing from bench to clinic. STATEMENT OF SIGNIFICANCE: Hofmeister effect enhanced hydrogel mechanical properties in accordance with the order of Hofmeister series through physical crosslinking that induced α-helix structures, hydrophobic interaction regions and helical junction zones among Gel molecular chains. Due to the Hofmeister effect of H₂PO₄^- ions, aldehyde groups were embedded in the center of entangled polymer chains that resulted in better biocompatibility. Hofmeister effect-enhanced Gel/O-Dex hydrogels through H₂PO₄^- ions accelerated wound healing and exhibited better histological morphology than ordinary hydrogels. Therefore, Hofmeister effect by essential inorganic anions is a promising method to improve mechanical properties and biocompatibility of natural hydrogels for their medical applications..

Progress and prospects of modified starch-based carriers in anticancer drug delivery

Recently, the role of starch-based carrier systems in anticancer drug delivery has gained considerable attention. Although there are same anticancer drugs, difference in their formulations account for unique therapeutic effects. However, the exploration on the effect-enhancing of anticancer drugs and their loading system by modified starch from the perspective of carrier regulation is still limited. Moreover, research on the reduced toxicity of the anticancer drugs due to modified starch as the drug carrier mediated by the intestinal microenvironment is lacking, but worth exploring. In this review, we examined the effect of modified starch on the loading and release properties of anticancer drugs, and the effect of resistant starch and its metabolites on intestinal microecology during inflammation. Particularly, the interactions between modified starch and drugs, and the effect of resistant starch on gene expression, protein secretion, and inflammatory factors were discussed. The findings of this review could serve as reference for the development of anticancer drug carriers in the future.

An all-in-one CO gas therapy-based hydrogel dressing with sustained insulin release, anti-oxidative stress, antibacterial, and anti-inflammatory capabilities for infected diabetic wounds

To effectively treat diabetic wounds, the development of versatile medical dressings that can long-term regulate blood glucose and highly effective anti-oxidative stress, antibacterial and anti-inflammatory are critical. Here, an all-in-one CO gas-therapy-based versatile hydrogel dressing (ICOQF) was developed via the dynamic Schiff base reaction between the amino groups on quaternized chitosan (QCS) and the aldehyde groups on benzaldehyde-terminated F108 (F108-CHO) micelles. CORM-401 (an oxidant-sensitive CO-releasing molecules) was encapsulated in the hydrophobic core of F108-CHO micelles and insulin was loaded in the three-dimensional network structure of ICOQF. The dynamic Schiff base bonds not only endowed ICOQF with good tissue adhesion, injectability and self-healing, but also gave it sustained and controllable insulin release ability. In addition, ICOQF could quickly generate CO in inflamed wound tissue by consuming reactive oxygen species. The generated CO could effectively anti-oxidative stress by activating the expression of heme oxygenase; antibacterial by inducing the rupture of bacterial cell membranes and mitochondrial dysfunction and inhibiting the synthesis of adenosine triphosphate; and anti-inflammatory by inhibiting the proliferation of activated macrophages and promoting the polarization of the M1 phenotype to the M2 phenotype. Due to these outstanding properties, ICOQF significantly promoted the healing of STZ-induced MRSA-infected diabetic wounds accompanied by good biocompatibility. This study clearly shows that ICOQF is a versatile hydrogel dressing with great application potential for the management of diabetic wounds. STATEMENT OF SIGNIFICANCE: The development of some versatile hydrogel dressings that can not only provide a prolonged and controlled insulin release property but also utilize a non-antibiotic treatment modality for highly effective antibacterial, anti-inflammatory, and anti-oxidative stress effects is vital for the successful treatment of diabetic wounds. Herein, we developed an all-in-one CO gas-therapy-based versatile hydrogel dressing (ICOQF) with sustained and controllable insulin release abilities. Moreover, ICOQF could not only quickly release CO in the inflamed wound tissue by consumption of reactive oxygen species but also utilize the generated CO to highly effectively anti-oxidative stress, antibacterial, and anti-inflammatory. ICOQF therapy substantially promoted the healing of STZ-induced MRSA-infected diabetic wounds. Overall, this work provides a multifunctional hydrogel dressing for the management of diabetic wounds.

pH-Sensitive nanoparticles based on amphiphilic imidazole/cholesterol modified hydroxyethyl starch for tumor chemotherapy

pH-Responsive nanoparticles (NPs) have emerged as an effective antitumor drug delivery system, promoting the drugs accumulation in the tumor and selectively releasing drugs in tumoral acidic microenvironment. Herein, we developed a new amphiphilic modified hydroxyethyl starch (HES) based pH-sensitive nanocarrier of antitumor drug delivery. HES was first modified by hydrophilic imidazole and hydrophobic cholesterol to obtain an amphiphilic polymer (IHC). Then IHC can self-assemble to encapsulate doxorubicin (DOX) and form doxorubicin-loaded nanoparticles (DOX/IHC NPs), which displayed good stability for one week storage and acidic sensitive long-term sustained release of DOX. As a result, cancer cell endocytosed DOX/IHC NPs could continuously release doxorubicin into cytoplasm and nucleus to effectively kill cancer cells. Additionally, DOX/IHC NPs could be effectively enriched in the tumor tissue, showing enhanced tumor growth inhibition effect compared to free doxorubicin. Overall, our amphiphilic modified HES-based NPs possess a great potential as drug delivery system for cancer chemotherapy.

Synthesis and characterization of electroconductive hydrogels based on oxidized alginate and polypyrrole-grafted gelatin as tissue scaffolds

Electroconductive biocompatible hydrogels with tunable properties have extensively been taken into account in tissue engineering applications due to their potential to provide suitable microenvironmental responses for the cells. In the present study, novel electroconductive hydrogels are designed and synthesized by reacting oxidized alginate with polypyrrole-grafted gelatin copolymer (PPy-g-gelatin) via formation of a Schiff-base linkage. The influence of the composition and the concentration of the components on the compressive modulus and functional performance of the hydrogels is investigated. The conductivity of the hydrogels measured by a two-probe method increased by increasing the level of polypyrrole-grafted gelatin, and a conductivity of 0.7753 S m^-1 was exhibited by the hydrogel composed of 8% w/v polypyrrole-grafted gelatin (oxidized alginate:gelatin:polypyrrole-grafted gelatin; 30 : 35 : 35% v/v). The hydrogel compressive modulus was shown to be enhanced by increasing the total concentration of hydrogel. The characteristic features of the prepared hydrogels, including swelling ratio, volume fraction, cross-link density, and mesh size, are also studied and analyzed. Besides, the conductive hydrogels have a smaller mesh size and higher cross-link density than the non-conductive hydrogels. However, the hydrogels with high cross-link density, small mesh size, and large pore size presented higher electroconductivity as a result of easier movement of the ions throughout the hydrogel. These conductive hydrogels exhibited electrical conductivity and biodegradability with cell viability, implying potential as scaffolds for tissue engineering.

An amylopectin-enabled skin-mounted hydrogel wearable sensor

Self-adhesiveness is highly desirable for conformal and seamless wearable electronics.

Polysaccharide nanoparticles: from fabrication to applications

The present review highlights the developments in polysaccharide nanoparticles with a particular focus on applications in biomedicine, cosmetics and food.

Ternary nano-biocomposite films using synergistic combination of bacterial cellulose with chitosan and gelatin for tissue engineering applications

Ternary nano-biocomposite films of bacterial cellulose-chitosan-gelatin (BC-C-G) were fabricated by immersing the BC pellicles into chitosan and gelatin mixture and subsequently freeze-drying. Scanning electron microscopy (SEM) images of the nano-biocomposite films revealed the presence of interconnected pores, with fibre diameter 20-150 nm. The composite films have a porosity of 95.3%, and showed good hydrophilicity with swelling ratio of 19 ± 1.8 and in vitro degradability. X-ray diffraction, attenuated total reflectance Fourier transform infrared spectroscopy, and thermogravimetric (TG) analysis results showed some interactions among the molecules of BC, gelatin, and chitosan within the film. The composite film offered good matrix for adhesion and proliferation of L929 fibroblasts cells as indicated by the cell attachment study, FE-SEM of cell-film constructs and cytocompatibility assay. Thus, the nano-biocomposite films of BC-C-G could be of paramount importance as tissue engineering scaffold. The "all-natural" ternary polymer composite films of BC-C-G have not been evaluated before for biomedical applications.

Dynamic crosslinked and injectable biohydrogels as extracellular matrix mimics for the delivery of antibiotics and 3D cell culture

Antibiotics are widely used in clinical medicine. As an important member, vancomycin often plays an irreplaceable role in some serious infections but for its use, there is still a lack of suitable carriers and effective formulations. To find a vancomycin carrier with potential for clinical applications, a new class of poly(γ-glutamic acid)/dextran-based injectable hydrogels have been constructed through dynamic covalent hydrazone linkages. Adipic dihydrazide (ADH)-grafted poly(γ-glutamic acid) (PGAADH) and sodium periodate-oxidized dextran (OD) precursors were synthesized; then, the hydrogels were formed by blending PGAADH and OD buffer solutions without any additives under physiological conditions. The newly formed precursor structures, mechanical properties, morphologies, hydrogel degradation profiles, and the interaction between the drug and precursors were investigated with FTIR spectroscopy, 1H NMR spectroscopy, rheological experiments, compression tests, SEM, and isothermal titration calorimetric (ITC) measurements. The resulting hydrogels exhibited excellent antibacterial ability and ideal variable performances. Moreover, the hydrogels exhibited different drug release kinetics and mechanisms and were applied effectively towards the controlled release of vancomycin. Significantly, benefitting from the reversibly cross-linked systems and the excellent biocompatibility, the hydrogels can work as the ideal material for HeLa cell culture, leading to encapsulated cells with higher viability and capacity that is proliferative. Therefore, the injectable PGAADH/OD hydrogels demonstrated attractive properties for future applications in pharmaceutics and tissue engineering.

New Developments in Medical Applications of Hybrid Hydrogels Containing Natural Polymers

New trends in biomedical applications of the hybrid polymeric hydrogels, obtained by combining natural polymers with synthetic ones, have been reviewed. Homopolysaccharides, heteropolysaccharides, as well as polypeptides, proteins and nucleic acids, are presented from the point of view of their ability to form hydrogels with synthetic polymers, the preparation procedures for polymeric organic hybrid hydrogels, general physico-chemical properties and main biomedical applications (i.e., tissue engineering, wound dressing, drug delivery, etc.).

Photopolymerized Starchstarch Nanoparticle (SNP) network hydrogels

Starch is an attractive biomaterial given its low cost and high protein repellency, but its use in forming functional hydrogels is limited by its high viscosity and crystallinity. Herein, we demonstrate the use of fully amorphous starch nanoparticles (SNPs) as functional hydrogel building blocks that overcome these challenges. Methacrylation of SNPs enables hydrogel formation via photopolymerization, with the low viscosity of SNPs enabling facile preparation of pre-gel suspensions of up to 35 wt% SNPs relative to <10 wt% with linear starch. Small angle neutron scattering indicates a significantly different microstructure in SNP-based hydrogels compared to linear starch-based hydrogels due to the balance between inter- and intra-particle crosslinks, consistent with SNPs forming denser and stiffer hydrogels. Functionalized SNPs are highly cytocompatible at degree of substitution values <0.25 and, once gelled, can effectively repel cell adhesion. The physicochemical versatility and biological functionality of SNP-based hydrogels offer potential in various applications.

Dialdehyde-β-cyclodextrin-crosslinked carboxymethyl chitosan hydrogel for drug release

A simple method was proposed for preparing the dialdehyde-β-cyclodextrin (DA-β-CD) cross-linked carboxymethyl chitosan (CMCS) hydrogels for drug delivery. DA-β-CD was yielded from the sodium periodate oxidation of β-CD. Phenolphthalein (PhP) was adopted as a model drug to study the drug loading and releasing properties of the obtained hydrogels. The results show that the ability of the hydrogel to load drug is affected by the aldehyde content of DA-β-CD. The inclusion constant of DA-β-CD toward PhP is lower than that of the original β-CD and decreased with the rising of the aldehyde content. An increased cross-linking degree between DA-β-CD and CMCS slows the PhP release to some extent. In comparison with glyoxal/CMCS, DA-β-CD/CMCS presents better PhP release properties. Only 19.2 % of PhP loaded in glyoxal/CMCS was released within 24 h. Half of PhP loaded in DA-β-CD/CMCS was released in 2 h and about 90 % was released within 12 h.

Synthesis and Characterization of pH-Sensitive Inulin Conjugate of Isoniazid for Monocyte-Targeted Delivery

The use of particles for monocyte-mediated delivery could be a more efficient strategy and approach to achieve intracellular targeting and delivery of antitubercular drugs to host macrophages. In this study, the potential of inulin microparticles to serve as a drug vehicle in the treatment of chronic tuberculosis using a monocytes-mediated drug targeting approach was evaluated. Isoniazid (INH) was conjugated to inulin via hydrazone linkage in order to obtain a pH-sensitive inulin-INH conjugate. The conjugate was then characterized using proton nuclear magnetic resonance (¹HNMR), Fourier transform infrared spectroscopy (FTIR) as well as in vitro, cellular uptake and intracellular Mycobacterium tuberculosis (Mtb) antibacterial efficacy. The acid-labile hydrazone linkage conferred pH sensitivity to the inulin-INH conjugate with ~95, 77 and 65% of the drug released after 5 h at pH 4.5, 5.2, and 6.0 respectively. Cellular uptake studies confirm that RAW 264.7 monocytic cells efficiently internalized the inulin conjugates into endocytic compartments through endocytosis. The intracellular efficacy studies demonstrate that the inulin conjugates possess a dose-dependent targeting effect against Mtb-infected monocytes. This was through efficient internalization and cleavage of the hydrazone bond by the acidic environment of the lysosome, which subsequently released the isoniazid intracellularly to the Mtb reservoir. These results clearly suggest that inulin conjugates can serve as a pH-sensitive intracellular drug delivery system for TB treatment.

Progress in pectin based hydrogels for water purification: Trends and challenges

Pectin is one of the finest natural polymer which has drawn great attention because of its applications in different fields. Due to the quintessential structure of pectin, it can be transformed into variety of useful products. It can be utilized as a blend in many polymers to make a mixture or a composite material. Owing to considerable collection in chemical conformation and cross-linking mechanism, different pectin based hydrogels have been prepared for different characteristics in pharmaceutical and bio-medical sites. Inventive properties of hydrogels like volubility, swellability, solvability and hydrophilicity make them better alternative for wastewater treatment. Recently, pectin based hydrogels have demonstrated excellent performance to eliminate various metal ions and dyes from the polluted water. The adsorption characteristics of pectin based hydrogels can be upgraded by using nanoparticles, which prompts to the development of hydrogel nano-composites. In this review article, we have summarized a comprehensive assessment in the direction of using pectin based hydrogels to remove toxic pollutants from aqueous solution. Sodium acrylate-co-N-isopropylacrylamide based pectin hydrogel has demonstrated the maximum adsorption capacities of 265.49, 137.43, 54.86, 53.86, 51.72 and 50.01 mg g^-1 for the adsorption of methyl violet, methylene blue, Pb(II), Cu(II), Co(II) and Zn(II) respectively. We have also discussed the pectin structure, properties and applications in this article.

Some Properties of Chemical Cross-Linking Biohydrogel from Starch and Chitosan

Chemical cross-linking was developed to prepare starch and chitosan-based hydrogels. First, the precursor of starch was synthesized through the reaction of carboxymethylation with sodium monochloroacetate, and then chitosan was grafted by using methacrylic acid as cross-linker. In this research, sago and cassava starches were used and mixed with chitosan, and the effect of methacrylic acid concentration was investigated to determine the grafting parameters and hydrogel characteristics. Compared to native starch and carboxymethylated starch, hydrogels from both starches have high ability to swell and high capacity to absorb water and oil. The highest grafting yield, grafting efficiency, and monomer conversion were achieved by experiment using 0.550 g of methacrylic acid per g of CMS-chitosan mixture. These hydrogels have a good potency as biodegradable absorbents for pharmaceutical and industrial application.

Nonmagnetic Hypertonic Saline-Based Implant for Breast Cancer Postsurgical Recurrence Prevention by Magnetic Field/pH-Driven Thermochemotherapy

Magnetic-mediated hyperthermia (MMT) is emerging as one of the promising techniques, which could synergistically treat cancer along with current treatment techniques such as chemotherapy and radiotherapy and trigger on-demand release of therapeutic macromolecules. However, the low specific absorption rate and potential in vivo toxicity of magnetic nanomaterials as the MMT mediators restrict the new advancements in MMT treatment. Herein, for the first trial, the unique inductive heating property of hypertonic saline (HTS), a clinically applied solution exhibiting several physiological effects under alternative magnetic field (AMF), was systematically investigated. Though without magnetic property, due to the dipolar polarization under the electromagnetic radiation, HTS can induce enough high and rapid temperature increase upon exposure under AMF. Based on such an observation, PEG-based HTS hydrogel was fabricated for the inhibition of unwanted diffusion of ions so as to ensure the ideal temperature rise at the targeted region for a longer time. Furthermore, an anticancer drug (doxorubicin) was also incorporated into the hydrogel to achieve the magnetic field/pH stimuli-responsive drug-sustainable release as well as synergistic thermochemotherapy. The potential application of the drug-loaded HTS-PEG-injectable hydrogel for breast cancer postsurgical recurrence prevention is demonstrated. Significant in vivo suppression of two kinds of breast cancer models was achieved by the hybrid hydrogel system. This work explores a new biomedical use of clinical HTS and a promising cancer treatment protocol based on HTS-PEG hydrogel for magnetic hyperthermia combined with stimuli-responsive chemotherapy for breast cancer postsurgical recurrence prevention.

Smart Starch-Poly( N-isopropylacrylamide) Hybrid Microgels: Synthesis, Structure, and Swelling Behavior

In this study, we present hybrid microgels made of starch nanoparticles (SNPs) and poly( N-isopropylacrylamide) [p(NIPAM)]. SNPs were formed through nanoprecipitation. Hybrid microgels were prepared by surfactant-free precipitation polymerization (SFPP) or in the presence of surfactant precipitation polymerization (PP) at different NIPAM/SNP ratios. Dynamic light scattering results of hybrid microgels synthesized by SFPP revealed changes in volume phase transition temperature according to SNP amount, where the increase in the hydrophilic content caused small shifts in the lower critical solution temperature (LCST), reaching nearly 35 °C. Colloidal stability was improved with the SNP content, leading to increased stability because of the hydroxyl groups. Small-angle X-ray scattering indicates a core-shell structure above the LCST, where SNPs chains cover a p(NIPAM) core. Swelling curves experimentally obtained were analyzed using the Flory-Rehner model, where the interaction parameter (χ) has been modeled either by a series expansion of the swelling ratio or by a Hill-like equation for a cooperative thermotropic transition.

Schiff base-containing dextran nanogel as pH-sensitive drug delivery system of doxorubicin: Synthesis and characterization

Stimuli-responsive hydrogels have been widely researched as carrier systems, due to their excellent biocompatibility and responsiveness to external physiologic environment factors. In this study, dextran-based nanogel with covalently conjugated doxorubicin (DOX) was developed via Schiff base formation using the inverse microemulsion technique. Since the Schiff base linkages are acid-sensitive, drug release profile of the DOX-loaded nanogel would be pH-dependent. In vitro drug release studies confirmed that DOX was released much faster under acidic condition (pH 2.0, 5.0) than that at pH 7.4. Approximately 66, 28, and 9% of drug was released in 72 h at pH 2.0, 5.0, and 7.4, respectively. Cell uptake by the human breast cancer cell (MCF-7) demonstrated that the DOX-loaded dextran nanogel could be internalized through endocytosis and distributed in endocytic compartments inside tumor cells. These results indicated that the Schiff base-containing nanogel can serve as a pH-sensitive drug delivery system. And the presence of multiple aldehyde groups on the nanogel are available for further conjugations of targeting ligands or imaging probes.

Superhydrophobic coatings on gelatin-based films: fabrication, characterization and cytotoxicity studies

As a degradable natural biomaterial, gelatin has good biocompatibility and nontoxicity, but gelatin is easily soluble in water which has limited its application. In order to solve this tough defect, superhydrophobic gelatin films (GSF) were prepared by first grafting silica nanoparticles onto gelatin films and then modifying silica nanoparticles with a fluorosilane coupling agent (FAS). Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), a particle size analyzer, a contact angle instrument (CA), X-ray photoelectron spectroscopy (XPS), a universal materials tester and an Incucyte™ Zoom system were used to characterize the morphology, molecular interactions, superhydrophobic performance, and cytotoxicity. Results show that GSF₃₀₀ modified by silica nanoparticles with a particle size of 303 nm has the largest contact angle (158.6°). At the same time, the contact angle is still more than 150° after 48 hours of infiltration in water. These results indicate that GSF₃₀₀ has strong long-term water resistance. In addition, GSF₃₀₀ has good mechanical strength, durability and nontoxicity. Therefore, such a durable, robust and superhydrophobic film has good potential applications in various functional biomedical aspects.

As a degradable natural biomaterial, gelatin has good biocompatibility and nontoxicity, but gelatin is easily soluble in water which has limited its application.

Synthesis of oxidized β-cyclodextrin with high aqueous solubility and broad-spectrum antimicrobial activity

Oxidized β-cyclodextrins with different oxidation levels were prepared using hydrogen peroxide as the oxidant and copper sulfate as the catalyst. The physicochemical, antimicrobial and antifungal properties of oxidized β-cyclodextrin were systematically studied. The results showed that the oxidation level of oxidized β-cyclodextrin was successfully controlled by adjusting the dosage of hydrogen peroxide. The aqueous solubility of oxidized β-cyclodextrin was highly improved as expected. However, oxidation changed the morphology and partly reduced the crystallinity of oxidized β-cyclodextrin due to the introduced carbonyl and carboxyl groups. It is interesting that oxidized β-cyclodextrin presented a broad-spectrum antimicrobial activity, which was efficiently improved with the increasing oxidation level. Growth of A. niger spores was efficiently inhibited in the presence of oxidized β-cyclodextrin. Moreover, oxidized β-cyclodextrin could effectively extend the storage time of apple. In summary, oxidized β-cyclodextrin shows potential as antimicrobial and antifungal agents in food industry.