Synthesis and characterization of new injectable and degradable dextran-based hydrogels

A photo-modulated nitric oxide delivering hydrogel for the accelerated healing of biofilm infected chronic wounds

Biofilm infection and impaired healing of chronic wounds are posing tremendous challenges in clinical practice. In this study, we presented a versatile antimicrobial hydrogel capable of delivering nitric oxide (NO) in a controllable manner to dissipate biofilms, eliminate microorganisms, and promote the healing of chronic wounds. This hydrogel was constructed by Schiff-base crosslinking of oxidized dextran and antimicrobial peptide ε-poly-lysine, further encapsulating photothermal nanoparticles bearing NO donor. This hydrogel could continuously and slowly release NO, effectively dissipating biofilms, and promoting the proliferation of mouse fibroblasts and the migration of endothelial cells. Upon exposure to NIR laser irradiation, the hydrogel generated hyperthermia and rapidly released NO, resulting in the efficient elimination of a broad spectrum of drug-resistant Gram-positive/negative bacterial and fungal biofilms through the synergistic effects of NO, photothermal therapy, and the antibacterial peptide. Notably, the hydrogel demonstrated exceptional in vivo therapeutic outcomes in accelerating the healing process of mice diabetic wounds infected with methicillin-resistant Staphylococcus aureus by successfully eliminating biofilm infection, regulating inflammation, and facilitating angiogenesis and collagen deposition. Overall, this proposed hydrogel shows great promise in accommodating the various demands of the complex repair process of chronic wounds infected with biofilms. STATEMENT OF SIGNIFICANCE: The presence of biofilm infections and underlying dysfunctions in the healing process made chronic wound become stuck in the inflammation stage and difficult to heal. This work developed a NIR laser-modulated three-stage NO-releasing versatile antimicrobial hydrogel (DEPN) exhibiting good therapeutic efficacy for chronic wound. This DEPN hydrogel could inherently and slowly released NO to disperse biofilm. Upon NIR laser irradiation, the DEPN hydrogel generated hyperthermia and induced a rapid burst release of NO effectively eliminating a broad spectrum of drug-resistant bacterial and fungal biofilms. Subsequently, the DEPN hydrogel continually release NO slowly to promote the tissue remolding. This DEPN hydrogel displays great potential in treatment of chronic wounds infected with biofilm.

Dynamic bond crosslinked maca polysaccharide hydrogels with reactive oxygen species scavenging and antibacterial effects on infected wound healing

In this study, a polysaccharide fragment with antioxidant and reactive oxygen species (ROS) scavenging activities was extracted from Maca (Lepidium meyenii Walp.) and subjected to structural analyses. The fragment, characterized by the α-D-Glcp-(1 → terminal group of the main chain linked to the →4)-Glcp-(1 → end unit through an O-6 bond and the O-3 bond of 1-3-4Glcp, was modified by introducing dialdehyde structures on its glucose units. It was then crosslinked with N-carboxymethyl chitosan via the Schiff base reaction to create a multifunctional hydrogel with antibacterial and ROS scavenging properties. Polyvinyl alcohol was incorporated to form a double crosslinked gel network, and the addition of silver nanoparticles enhanced its antibacterial efficacy. This gel system can scavenge excess ROS, mitigate wound inflammation, eradicate harmful bacteria, and aid in the restoration of skin microecology. The multifunctional maca polysaccharide hydrogel shows significant potential as a medical dressing for the treatment of infected wounds.

A novel injectable hydrogel prepared from phenylboronic acid modified gelatin and oxidized-dextran for bone tissue engineering

Complicated fractures have always been challenging in orthopaedics. Designing a multifunctional biomaterial that can contribute to the treatment of fractures using a simple operation remains challenging. Here, we developed a trinity hydrogel system consisting of hydrogel prepared from phenylboronic acid modified gelatin and oxidized-dextran, lithium and cobalt co-doped mesoporous bioactive glass nanoparticles (MBGNs), and irisin. This hydrogel material exhibits considerable injectability, fat-to-shape, and self-healing characteristics. In addition, compared to hydrogel prepared from gelatin and oxidized-dextran, the hydrogel material presented a noticeable enhancement in compression stress and adhesion strength towards porcine bone fragments, which enables it more effectively splice bone fragments during surgery. Based on the various interactions between irisin and the hydrogel network, the system exhibited a clear sustained release of irisin. Based on the results of in vitro cell tests, the hydrogel material showed good cytocompatibility. And it also considerably enhanced the in vitro pro-osteogenic and pro-angiogenic capacities of bone marrow mesenchymal stromal cells (BMSCs) and human umbilical vein endothelial cells (HUVECs). In vivo experimental results indicated that this hydrogel considerably improved the repair of cranial defects in rats. The current study provides a feasible strategy for the treatment of bone fractures and stimulation of fracture healing.

Nanohybrid dual-network chitosan-based hydrogels: Synthesis, characterization, quicken infected wound healing by angiogenesis and immune-microenvironment regulation

Infectious wounds are difficult to heal because of vascular damage and immune imbalance. The multi-functional hydrogel dressing can regulate vascular regeneration and immune microenvironment through continuous supply of bioactive ingredients to the wound site, which can effectively accelerate the healing speed of infected wounds. In this work, a multifunctional dual-network hydrogel (QCMOD) with good injectability, stability, self-healing and adhesion was designed by combining methacrylic anhydride-modified quaternized chitosan (QCM) with oxidized dextran (OD) via Schiff base reaction and photo-crosslinked polymerization. Subsequently, MgO/Icariin composite nanoparticles with icariin coating were prepared and loaded in QCMOD hydrogel to establish nanohybrid dual-network chitosan-based hydrogels (QCMOD@MI), which possessed a controlled release of Mg2+ and icariin as well as the ability of guiding physiological behavior in wound healing progress. In vitro results showed the nanohybrid hydrogel reduced bacterial infection and possessed multiple physiological functions including promoting cell migration, angiogenesis and reducing secretion of inflammatory factors. In vivo, the nanohybrid hydrogel showed excellent pro-healing abilities for infected full-thickness wounds by reducing bacterial infections and improving the microenvironment of ischemia and inflammation. This study provides a new paradigm for the design of multifunctional bioactive hydrogels and the obtained hydrogel is expected to become a new type of functional dressing.

Dextran-Based Injectable Hydrogel Composites for Bone Regeneration

Currently, bone infections caused by diseases or injuries are a major health issue. In addition, the conventional therapeutic approaches used to treat bone diseases or injuries present several drawbacks. In the area of tissue engineering, researchers have been developing new alternative therapeutic approaches, such as scaffolds, to promote the regeneration of injured tissues. Despite the advantages of these materials, most of them require an invasive surgical procedure. To overcome these problems, the main focus of this work was to develop scaffolds for bone regeneration, which can be applied using injectable hydrogels that circumvent the use of invasive procedures, while allowing for bone regeneration. Throughout this work, injectable hydrogels were developed based on a natural polymer, dextran, along with the use of two inorganic compounds, calcium β-triphosphate and nanohydroxyapatite, that aimed to reinforce the mechanical properties of the 3D mesh. The materials were chemically characterized considering the requirements for the intended application: the swelling capacity was evaluated, the degradation rate in a simulated physiological environment was assessed, and compression tests were performed. Furthermore, vancomycin was incorporated into the polymeric matrices to obtain scaffolds with antibacterial performance, and their drug release profile was assessed. The cytotoxic profile of the hydrogels was assessed by an MTS assay, using osteoblasts as model cells. The data obtained demonstrated that dextran-based hydrogels were successfully synthesized, with a drug release profile with an initial burst between 50 and 80% of the drug. The hydrogels possess fair biocompatibility. The swelling capacity showed that the stability of the samples and their degradation profile is compatible with the average time period required for bone regeneration (usually about one month) and have a favorable Young's modulus (200-300 kPa). The obtained hydrogels are well-suited for bone regeneration applications such as infections that occur during implantation or bone graft substitutes with antibiotics.

A biodegradable injectable fluorescent polyurethane-oxidized dextran hydrogel for non-invasive monitoring

Hydrogels have been extensively used in the field of biomedical engineering. In order to achieve non-invasive and real-time visualization of the in vivo status of hydrogels, we designed a fluorescent polyurethane-oxidized dextran (PU-OD) hydrogel with good injectability and self-healing properties, which was cross-linked from a tetraphenyl ethylene (TPE)-containing fluorescent polyurethane emulsion with oxidized dextran by dynamic acylhydrazone bonds. The hydrogel can be used as a visual platform for drug delivery as well as monitoring its own degradation. The network structure of the hydrogel gave it drug-loading capability, and the acylhydrazone bond enabled its pH-responsive drug release. Meanwhile, the PU-OD hydrogel could undergo fluorescence resonance transfer with doxorubicin hydrochloride, showing its potential application in monitoring drug release. In addition, fluorometric and weighing methods were performed to monitor the degradation behavior of the hydrogels in vivo and in vitro, respectively, showing that the non-invasive fluorometric method can be consistent with the invasive weighing method. This work highlights that the introduction of aggregation-induced emission molecules into polyurethanes provides a visual platform that allows for non-invasive monitoring of the material without affecting its own function, which is convenient and less damaging to the body or animals. Consequently, it possesses excellent and promising potential in biomedical materials technologies.

Biocompatible scaffolds based on collagen and oxidized dextran for endothelial cell survival and function in tissue engineering

Angiogenesis is a vital step in tissue regeneration. Hence, the current study aimed to prepare oxidized dextran (Odex)/collagen (Col)-hydrogels with laminin (LMN), as an angiogenic extracellular matrix (ECM) component, for promoting human umbilical vein endothelial cell (HUVEC) proliferation and function. Odex/Col scaffolds were constructed at various concentrations and temperatures. Using oscillatory rheometry, scanning electron microscopy (SEM), and cell viability testing, the scaffolds were characterized, and then HUVEC proliferation and function was compared with or without LMN. The gelation time could be modified by altering the Odex/Col mass ratio as well as the temperature. SEM showed that Odex/Col hydrogels had a more regular three-dimensional (3D) porous structure than the Col hydrogels. Moreover, HUVECs grew faster in the Col scaffold (12 mg/mL), whereas the Odex (30 mg/mL)/Col (6 mg/mL) scaffold exhibited the lowest apoptosis index. Furthermore, the expression level of vascular endothelial growth factor (VEGF) mRNA in the group without LMN was higher than that with LMN, and the Odex (30 mg/mL)/Col (6 mg/mL) scaffold without LMN had the highest VEGF protein secretion, allowing the cells to survive and function effectively. Odex/Col scaffolds, with or without LMN, are proposed as a tissue engineering construct to improve HUVEC survival and function for angiogenesis.

Formation of substituted dioxanes in the oxidation of gum arabic with periodate

Renewable polysaccharide feedstocks are of interest in bio-based food packaging, coatings and hydrogels. Their physical properties often need to be tuned by chemical modification, e.g. by oxidation using periodate, to introduce carboxylic acid, ketone or aldehyde functional groups. The reproducibility required for application on an industrial scale, however, is challenged by uncertainty about the composition of product mixtures obtained and of the precise structural changes that the reaction with periodate induces. Here, we show that despite the structural diversity of gum arabic, primarily rhamnose and arabinose subunits undergo oxidation, whereas (in-chain) galacturonic acids are unreactive towards periodate. Using model sugars, we show that periodate preferentially oxidises the anti 1,2-diols in the rhamnopyranoside monosaccharides present as terminal groups in the biopolymer. While formally oxidation of vicinal diols results in the formation of two aldehyde groups, only traces of aldehydes are observed in solution, with the main final products obtained being substituted dioxanes, both in solution and in the solid state. The substituted dioxanes form most likely by the intramolecular reaction of one aldehyde with a nearby hydroxyl group, followed by hydration of the remaining aldehyde to form a geminal diol. The absence of significant amounts of aldehyde functional groups in the modified polymer impacts crosslinking strategies currently attempted in the preparation of renewable polysaccharide-based materials.

CuS Hybrid Hydrogel for Near-Infrared-Enhanced Infected Wound Healing: A Gelatin-Assisted Synthesis and Direct Incorporation Strategy

Developing antibacterial hydrogels, with good mechanical strength and self-healing ability to resist bacterial invasion and accelerate skin regeneration, is critical for infected full-thickness skin wound treatment. Herein, we report a gelatin-assisted synthesis and direct incorporation strategy to construct a CuS hybrid hydrogel for infected wound healing applications. CuS nanodots (NDs) were synthesized directly inside a gelatin host matrix (Gel-CuS), and these tightly confined and evenly distributed CuS NDs displayed superb dispersibility and stability against oxidation. Gel-CuS was then used to crosslink with oxidized dextran (ODex) to form a Gel-CuS-8/ODex hydrogel (8 stands for the concentration of CuS, in mM) via a facile Schiff-base reaction, which exhibited improved mechanical properties, excellent adhesion and self-healing ability, suitable swelling and degradation behavior, and good biocompatibility. The Gel-CuS-8/ODex hydrogel can act as an efficient antibacterial agent due to its photothermal and photodynamic properties under a 1064 nm laser irradiation. Furthermore, in animal experiments, when being applied as wound dressing, the Gel-CuS-8/ODex hydrogel significantly promoted infected full-thickness cutaneous wound healing through improved epidermis and granulation tissue formation and accelerated generation of new blood vessels, hair follicles, and collagen deposition after proper near-infrared irradiation treatment. This work provides a promising strategy to synthesize functional inorganic nanomaterials tightly and evenly embedded inside modified natural hydrogel networks for wound healing applications.

Inflammation-modulating antibacterial hydrogel sustained release asiaticoside for infection wound healing

Wound infection and persistent inflammation are considered to be the main reasons for hindering wound healing. In this study, we developed an innovative hydrogel dressing, EPL-DA/ODEX/AMs, as a platform to inhibit bacteria and inflammation and promote wound healing. Polylysine (EPL) has cationic properties and can effectively disrupt bacterial cell membranes for antibacterial purposes. Polylysine-grafted levodopa (EPL-DA) with abundant amino and catechol groups can be cross-linked with oxidized dextran through Schiff base reaction to form antibacterial hydrogels with good adhesion and mechanical properties. In addition, asiaticoside, which can effectively inhibit inflammation and promote collagen regeneration, is made into PLGA microspheres to effectively deliver asiaticoside to the wound. The innovative antibacterial hydrogel of EPL-DA/ODEX/AMs may become a competitive wound dressing for infected wound.

Indirect co-culture of islet cells in 3D biocompatible collagen/laminin scaffold with angiomiRs transfected mesenchymal stem cells

Diabetes is an autoimmune disease in which the pancreatic islets produce insufficient insulin. One of the treatment strategies is islet isolation, which may damage these cells as they lack vasculature. Biocompatible scaffolds are one of the efficient techniques for dealing with this issue. The current study is aimed to determine the effect of transfected BM-MSCS with angiomiR-126 and -210 on the survival and functionality of islets loaded into a 3D scaffold via laminin (LMN). AngiomiRs/Poly Ethylenimine polyplexes were transfected into bone marrow-mesenchymal stem cells (BM-MSCs), followed by 3-day indirect co-culturing with islets laden in collagen (Col)-based hydrogel scaffolds containing LMN. Islet proliferation and viability were significantly increased in LMN-containing scaffolds, particularly in the miRNA-126 treated group. Insulin gene expression was superior in Col scaffolds, especially, in the BM-MSCs/miRNA-126 treated group. VEGF was upregulated in the LMN-containing scaffolds in both miRNA-treated groups, specifically in the miRNA-210, leading to VEGF secretion. MiRNAs' target genes showed no downregulation in LMN-free scaffolds; while a drastic downregulation was seen in the LMN-containing scaffolds. The highest insulin secretion was recorded in the Oxidized dextran (Odex)/Col^LMN+ group with miRNA-126. LMN-containing biocompatible scaffolds, once combined with angiomiRs and their downstream effectors, promote islets survival and restore function, leading to enhanced angiogenesis and glycemic status.

Injectable Dopamine-Polysaccharide In Situ Composite Hydrogels with Enhanced Adhesiveness

Polysaccharide bio-adhesives used for non-invasive repair often show weak mechanical strength and tissue adhesion, even when covalently modified with dopamine (DA) from mussel proteins and its derivatives. Low cohesion of the polysaccharide adhesives and easy oxidation of DA may result in the low adhesion properties of the polysaccharide-DA adhesives. In this work, we aimed to prepare a series of injectable hydrogel adhesives to improve their cohesion and adhesion by in situ mixing DA with the polysaccharide without covalent modification. The injectable and rapid curing adhesives were prepared by mixing oxidized dextran (ODE) and chitosan (CS) through a Schiff base reaction in the presence (or absence) of DA. The gelation time of the adhesive was customized to be less than 20 s by controlling the amount of ODE, regardless of the amount of DA. Multi-cross-linked (MC) hydrogels were further prepared by adding cross-linking agents such as sodium periodate (NaIO₄) and ferric trichloride (FeCl₃), and their sol-gel transitions were easily adjusted by changing the amounts of the cross-linking agents. The MC-FeCl₃ hydrogel adhesive displayed good tissue adhesion with a lap shear adhesion strength of 345 kPa, which was 43 times that of fibrin glue. Results from Raman spectra, texture profile analyses, and atomic force microscopy images confirmed the enhanced adhesion induced by a higher cohesion of MC-FeCl₃, owing to the coordination of Fe³⁺ and DA and non-covalent and covalent bonds of DA. Moreover, the adhesives showed good biodegradability and biocompatibility. These results demonstrate that the injectable and sticky hydrogels with good adhesion are promising materials for tissue repair.

In situ self-assembly of amphiphilic dextran micelles and superparamagnetic iron oxide nanoparticle-loading as magnetic resonance imaging contrast agents

Polymeric micelles have long been considered as promising nanocarrier for hydrophobic drugs and imaging probes, due to their nanoscale particle size, biocompatibility and ability to loading reasonable amount of cargoes. Herein, a facile method for dextran micelles preparation was developed and their performance as carriers of superparamagnetic iron oxide (SPIO) nanocrystals was evaluated. Amphiphilic dextran (Dex-g-OA) was synthesized via the Schiff base reactions between oxidized dextran and oleylamine, and self-assembled in situ into nano-size micelles in the reaction systems. The self-assembling behaviors of the amphiphilic dextran were identified using fluorescence resonance energy transfer technique by detection the energy transfer signal between the fluorophore pairs, Cy5 and Cy5.5. Hydrophobic SPIO nanoparticles (Fe₃O₄ NPs) were successfully loaded into the dextran micelles via the in situ self-assembly process, leading to a series of Fe₃O₄ NPs-loaded micelle nanocomposites (Fe₃O₄@Dex-g-OA) with good biocompatibility, superparamagnetism and strongly enhanced T ₂ relaxivity. At the magnetic field of 0.5 T, the Fe₃O₄@Dex-g-OA nanocomposite with particle size of 116.2 ± 53.7 nm presented a higher T ₂ relaxivity of 327.9 mM Fe - 1 ·s^-1. The prepared magnetic nanocomposites hold the promise to be used as contrast agents in magnetic resonance imaging.

Aptamer/Hydroxyapatite-Functionalized Titanium Substrate Promotes Implant Osseointegration via Recruiting Mesenchymal Stem Cells

Endowing bone regeneration materials with both stem cell recruitment and osteoinduction properties is a key factor in promoting osseointegration of titanium (Ti) implants. In this study, Apt19s-grafted oxidized hyaluronic acid (OHA) was deposited onto a protein-mediated biomineralization hydroxyapatite (HAp) coating of Ti. HAp was achieved by the treatment of lysozyme and tris(2-carboxyethyl) phosphonate mixture and then soaked in calcium ion (Ca²⁺) solution to obtain functional Ti substrate (Ti/HAp/OHA-Apt). In vitro studies confirmed that Ti/HAp/OHA-Apt could effectively maintain the sustained release of Apt19s from Ti for 7 days. The released Apt19s significantly enhanced the migration of bone marrow mesenchymal stem cells (MSCs), which was reflected by the experiment of transwell assay, wound healing, and zymogram detection. Compared with pure Ti, Ti/HAp/OHA-Apt was able to adjust the adsorption of functional proteins at the Ti-based interface to expose their active sites, which significantly increased the expression of adhesion-associated proteins (vinculin and tensin) in MSCs to promote their adhesion on Ti-based interface. In vitro cell experiments of alkaline phosphatase activity staining, mineralization detection, and expression of osteogenesis-related genes showed that Ti/HAp/OHA-Apt significantly enhanced the osteogenic differentiation ability of MSCs, which may be highly related to the porous structure of hydroxyapatite on Ti interface. In vivo test of Micro-CT, H&E staining, and histochemical staining further confirmed that Ti/HAp/OHA-Apt was able to promote MSC recruitment at the peri-implant interface to form new bone. This work provides a new approach to develop functional Ti-based materials for bone defect repair.

Recent advances in polysaccharide-based in situ forming hydrogels

Polysaccharides comprise an important class of natural polymers; they are abundant, diverse, polyfunctional, typically benign, and are biodegradable. Using polysaccharides to design in situ forming hydrogels is an attractive and important field of study since many polysaccharide-based hydrogels exhibit desirable characteristics including self-healing, responsiveness to environmental stimuli, and injectability. These characteristics are particularly useful for biomedical applications. This review will discuss recent discoveries in polysaccharide-based in situ forming hydrogels, including network architecture designs, curing mechanisms, physical and chemical properties, and potential applications.

Elucidating the degradation mechanism of a self-degradable dextran-based medical adhesive

We developed a self-degradable medical adhesive, LYDEX, consisting of periodate-oxidized aldehyde-functionalized dextran (AD) and succinic anhydride-treated ε-poly-l-lysine (SAPL). After gelation and adhesion of LYDEX by Schiff base bond formation between the AD aldehyde groups and SAPL amino groups, molecular degradation associated with the Maillard reaction is initiated, but the detailed degradation mechanism remains unknown. Herein, we elucidated the degradation mechanism of LYDEX by analyzing the main degradation products under typical solution conditions in vitro. The degradation of the LYDEX gel with a sodium periodate/dextran content of 2.5/20 was observed using gel permeation chromatography and infrared and ¹H NMR spectroscopy. The AD ratio in the AD-SAPL mixture increased as the molecular weight decreased with the degradation time. This discovery of LYDEX self-degradability is useful for clarifying other polysaccharide hydrogel degradation mechanisms, and valuable for the use of LYDEX in medical applications, such as hemostatic or sealant materials.

Recent Progress on Polysaccharide-Based Hydrogels for Controlled Delivery of Therapeutic Biomolecules

A plethora of applications using polysaccharides have been developed in recent years due to their availability as well as their frequent nontoxicity and biodegradability. These polymers are usually obtained from renewable sources or are byproducts of industrial processes, thus, their use is collaborative in waste management and shows promise for an enhanced sustainable circular economy. Regarding the development of novel delivery systems for biotherapeutics, the potential of polysaccharides is attractive for the previously mentioned properties and also for the possibility of chemical modification of their structures, their ability to form matrixes of diverse architectures and mechanical properties, as well as for their ability to maintain bioactivity following incorporation of the biomolecules into the matrix. Biotherapeutics, such as proteins, growth factors, gene vectors, enzymes, hormones, DNA/RNA, and antibodies are currently in use as major therapeutics in a wide range of pathologies. In the present review, we summarize recent progress in the development of polysaccharide-based hydrogels of diverse nature, alone or in combination with other polymers or drug delivery systems, which have been implemented in the delivery of biotherapeutics in the pharmaceutical and biomedical fields.

Facile preparation of chitosan-dopamine-inulin aldehyde hydrogel for drug delivery application

Chitosan-based hydrogels are a suitable and versatile system for the design of localized and controlled drug delivery systems. In the current study, a hydrogel based on chitosan (CS), Dopamine (DA), and Inulin aldehyde (IA) was fabricated without the further use of catalyst or initiators. The effect of the IA contents as a crosslinking agent on the properties of the prepared hydrogel was studied. The crosslinking reaction between CS and IA was verified by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). Various characteristics of the CS/DA/IA hydrogels were further assessed utilizing swelling experiment, in vitro drug release, in vitro cytotoxicity assay. The drug-loaded hydrogels represented the sustained release of Indomethacin according to the in vitro drug release test in acidic (pH = 4), basic (pH = 10) medium as well as physiological condition (pH = 7). Finally, the CS/DA/IA hydrogels exhibited appropriate cytocompatibility against the L-929 fibroblast cell line according to the direct contact MTT assay.

Dual responsive dextran-graft-poly (N-isopropylacrylamide)/doxorubicin prodrug via Schiff base reaction

Stimulus-responsive nanoparticles stand out in studies for cancer treatment since these systems can promote a selective release of the drug in tumor tissues and cells, minimizing the effects caused by conventional chemotherapy. Dextran-graft-poly (N-isopropylacrylamide) copolymers were synthesized via Schiff base formation. The synthesis of copolymers was confirmed by Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance (NMR) and the analyses of dynamic light scattering (DLS) showed that the copolymers were thermal and pH dual-responsive. The chemotherapy drug doxorubicin (DOX) was conjugated to the copolymers via Schiff base formation, obtaining nanoparticles by self-assembling with size smaller than 130 nm. A higher percentage of doxorubicin was released at pH 5.0 (59.1 ± 2.1%) compared to physiological pH (34.9 ± 4.8%), confirming a pH-sensitive release profile. The in vitro cytotoxicity assay demonstrated that DOX-loaded nanoparticles can inhibit cancer cell proliferation and promote reduced cytotoxicity in non-tumor cells. The D_45kP_30k-DOX nanoparticles induced morphological changes in HCT-116 cells suggesting cell death and the cell uptake assay indicated that the nanoparticles can be internalized by endocytosis. Therefore, DOX-loaded nanoparticles exhibited potential as smart systems for cancer treatment.

A multifunctional shape-adaptive and biodegradable hydrogel with hemorrhage control and broad-spectrum antimicrobial activity for wound healing

Hemorrhage is the leading cause of preventable death of injured military and civilian patients, and subsequent infection risks endanger their lives or impede the healing of their wounds. Here, we report an injectable biodegradable hydrogel with hemostatic, antimicrobial, and healing-promoting properties. The hydrogel was prepared by dynamic cross-linking of a natural polysaccharide (dextran) with antimicrobial peptide ε-poly-l-lysine (EPL) and encapsulating base fibroblast growth factor (bFGF). The amino groups of EPL were allowed to react with the aldehyde of oxidized dextran (OD) through the Schiff-base reaction for the generation of hydrogels that have fast self-healing and injectable characteristics and adapt to the shapes of wounds. The prepared OD/EPL hydrogels promoted blood clotting in vitro and stopped bleeding in a rat liver injury model within 6 min through their platelet-aggregating ability and sealing effect. These hydrogels exhibited inherent antimicrobial effects without the use of antibiotics and effectively killed a broad spectrum of pathogenic microbes, including Gram-positive methicillin-resistant Staphylococcus aureus (MRSA), Gram-negative Escherichia coli, and Pseudomonas aeruginosa and fungus Candida albicans in vitro. Moreover, these OD/EPL hydrogels were compatible with mammalian cells in vitro and in vivo and biodegradable in the mouse body. The loaded bFGF can be released sustainably, and it can promote angiogenesis, endothelial cell migration, and consequently accelerate the healing of wounds. The OD/EPL hydrogel inhibited MRSA infection in a rat full-thickness skin wound model and promoted healing. This kind of multifunctional hydrogel is a promising wound dressing for the emergency treatment of acute deep or penetrating injuries.

Antibacterial, hemostasis, adhesive, self-healing polysaccharides-based composite hydrogel wound dressing for the prevention and treatment of postoperative adhesion

Herein, we fabricated novel self-healing, in situ injectable, biodegradable, and non-toxic hydrogels anti-adhesion barrier materials composed of N, O-carboxymethyl chitosan (N,O-CS) and oxidized dextran (ODA) without requiring any chemical cross-linking agent or external stimuli triggers for the prevention and treatment of post-operative peritoneal adhesions. The N,O-CS/ODA hydrogels have a good suitable gelation time, good cytocompatibility and hemocompatibility, good antibacterial activity, excellent biodegradable and biocompatible, and can effectively inhibit the adhesion of fibroblasts to the wound, thereby suggesting that N,O-CS/ODA hydrogels are suitable for preventing post-operative adhesion. Meanwhile, a rat injury sidewall-cecum abrasion model is developed to investigate the efficacy of these hydrogels in achieving post-operative anti-adhesion. A significant reduction of peritoneal adhesions (10% rat with lower score adhesion) is observed in the N,O-CS/ODA-hydrogel-treated group compared with the commercial hydrogel and control groups. These results demonstrated that N,O-CS/ODA hydrogel could effectively prevent post-operative peritoneal adhesion without side effects. Therefore, the N,O-CS/ODA hydrogels with multi-functional properties exhibit great potential for the prevention and treatment of postoperative adhesion.

Development of macroscopically ordered liquid crystalline hydrogels from biopolymers with robust antibacterial activity for controlled drug delivery applications

Macroscopically ordered liquid crystalline hydrogel with antibacterial activity for controlled drug delivery applications.

A conductive dual-network hydrogel composed of oxidized dextran and hyaluronic-hydrazide as BDNF delivery systems for potential spinal cord injury repair

Spinal cord injury (SCI) often causes neuronal death and axonal degeneration. In this study, we report a new strategy for preparing injectable and conductive polysaccharides-based hydrogels that could sustainably deliver brain-derived neurotrophic factor (BDNF) for SCI repair. We used poly(lactic-co-glycolic acid) (PLGA) as a carrier to encapsulate BDNF. The resulting microspheres were then modified with tannic acid (TA). The polysaccharides-based hydrogel composed of oxidized dextran (Dex) and hyaluronic acid-hydrazide (HA) was mixed with TA-modified microspheres to form the ultimate BDNF@TA-PLGA/Dex-HA hydrogel. Our results showed that the hydrogel had properties similar to natural spinal cords. Specifically, the hydrogel had soft mechanical properties and high electrical conductivity. The cross-sectional morphology of the hydrogel exhibited a continuous and porous structure. The swelling and degradation behaviors of the Dex-HA hydrogel in vitro indicated the incorporation of TA into hydrogel matrix could improve the stability of the hydrogel matrix as well as extend the release time of BDNF from the matrix. Furthermore, results from immunostaining and real-time PCR demonstrated that BDNF@TA-PLGA/Dex-HA hydrogel could promote the differentiation of neural stem cells (NSCs) into neurons and inhibit astrocyte differentiation in vitro. These results show the great potential of this hydrogel as a biomimetic material in SCI regeneration.

Hydrogel Network Dynamics Regulate Vascular Morphogenesis

Matrix dynamics influence how individual cells develop into complex multicellular tissues. Here, we develop hydrogels with identical polymer components but different crosslinking capacities to enable the investigation of mechanisms underlying vascular morphogenesis. We show that dynamic (D) hydrogels increase the contractility of human endothelial colony-forming cells (hECFCs), promote the clustering of integrin β1, and promote the recruitment of vinculin, leading to the activation of focal adhesion kinase (FAK) and metalloproteinase expression. This leads to the robust assembly of vasculature and the deposition of new basement membrane. We also show that non-dynamic (N) hydrogels do not promote FAK signaling and that stiff D- and N-hydrogels are constrained for vascular morphogenesis. Furthermore, D-hydrogels promote hECFC microvessel formation and angiogenesis in vivo. Our results indicate that cell contractility mediates integrin signaling via inside-out signaling and emphasizes the importance of matrix dynamics in vascular tissue formation, thus informing future studies of vascularization and tissue engineering applications.

Promising alternative gum: Extraction, characterization, and oxidation of the galactomannan of Cassia fistula

Galactomannan extracted from Cassia fistula seed endosperm present little data related to the its structural characterization. This study reports the chemical characterization of the galactomannan from Cassia fistula (CF) and their oxidized derivatives. The extracted CF presented a yield of 26.5% (w/w) and the intrinsic viscosity [η] was 9.73 dL/g. 1D and 2D nuclear magnetic resonance spectroscopy (NMR) confirmed that the polysaccharide has a backbone of 4-linked β-D-mannose units, and contains galactose units as pending groups. These galactose units are linked to the central core through a (1→6) linkage and the galactomannan presented Man/Gal ratio of 3.1/1. The galactomannan from Cassia fistula presents low cytotoxicity in Vero cells with a CC₅₀ > 1000 μg/ml. The properties of CF resemble other commercially important galactomannans such as Locust bean gum. Three oxidized derivatives of CF were produced by periodate oxidation, which were carefully characterized by different structural techniques. It was observed that as the degree of oxidation increased, there was an increase in the Man/Gal ratio and a reduction in molar mass and viscosity. The polialdehyde produced may be explored as a versality material to react with amine group of the protein and amined polysaccharide to produce biomaterials.

White-light-emitting hydrogels with self-healing properties and adjustable emission colors

White-light-emitting soft materials with self-healing properties show extensive applications in many fields. Herein, a novel self-healing hydrogel is successfully fabricated using oxidized dextran (Odex) and dithiodipropionate dihydrazide (TPH). Carbon dots (CDs), Riboflavin (Ri) and Rhodamine B (RhB) are incorporated into the gel matrix to produce white light emission through fluorescence resonance energy transfer (FRET) process, thus achieving excellent Commission Internationale de L'eclairage (CIE) coordinate value of (0.30, 0.33). The emission colors can be easily tuned via changing proportions of three emitters or the excitation wavelength. When the hydrogels are coated on an ultraviolet light-emitting diodes (UV LED), the hydrogel coating converts UV light to white light and repairs itself in 20 h while a hole is dug from it. Thanks to reversible exchanging reactions of acylhydrazone and disulfide bonds in hydrogel networks, the hydrogel coating exhibits perfect self-healing property in a wide range of pH (from 5 to 9 except for 7). The excellent emission and self-healing properties of hydrogels have great value in practical applications.

The Application of Hydrogels Based on Natural Polymers for Tissue Engineering

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Hydrogels are known as polymer-based networks with the ability to absorb water and other body fluids. Because of this, the hydrogels are used to preserve drugs, proteins, nutrients or cells. Hydrogels possess great biocompatibility, and properties like soft tissue, and networks full of water, which allows oxygen, nutrients, and metabolites to pass. Therefore, hydrogels are extensively employed as scaffolds in tissue engineering. Specifically, hydrogels made of natural polymers are efficient structures for tissue regeneration, because they mimic natural environment which improves the expression of cellular behavior.

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Producing natural polymer-based hydrogels from collagen, hyaluronic acid (HA), fibrin, alginate, and chitosan is a significant tactic for tissue engineering because it is useful to recognize the interaction between scaffold with a tissue or cell, their cellular reactions, and potential for tissue regeneration. The present review article is focused on injectable hydrogels scaffolds made of biocompatible natural polymers with particular features, the methods that can be employed to engineer injectable hydrogels and their latest applications in tissue regeneration.

A shear-thinning electrostatic hydrogel with antibacterial activity by nanoengineering of polyelectrolytes

Injectable shear-thinning hydrogels can be prepared by the non-covalent interactions between hydrophilic polymers. Although electrostatic force is a typical non-covalent interaction, direct mixing of two oppositely charged polyelectrolytes usually leads to a complex coacervate rather than an injectable hydrogel. Herein, a facile approach is proposed to prepare a shear-thinning hydrogel by nanoengineering of polyelectrolytes. Nanosized cationic micelles with electroneutral shells were prepared by mixing methoxyl poly(ethylene glycol)-block-poly(ε-caprolactone) and poly(ε-caprolactone)-block-poly(hexamethylene guanidine) hydrochloride-block-poly(ε-caprolactone) in an aqueous solution. When sodium carboxymethyl cellulose was added into the micellar solution, the outer poly(ethylene glycol) shell of mixed micelles prevented the instant electrostatic interaction between poly(hexamethylene guanidine) hydrochloride segments and sodium carboxymethyl cellulose, resulting in a homogenous shear-thinning electrostatic (STES) hydrogel. Because of the cationic poly(hexamethylene guanidine) hydrochloride segments, this hydrogel exhibits strong antibacterial activity against both Gram-positive and Gram-negative bacteria. Furthermore, the poly(ε-caprolactone) core of the mixed micelles can efficiently encapsulate a hydrophobic drug. In this work, curcumin-loaded STES hydrogel prepared by this method was used as wound dressing material that can promote wound healing even in infected wounds by further reducing bacterial infection via releasing curcumin. The present study provides a facile strategy to prepare shear-thinning antibacterial hydrogels from polyelectrolytes, which has great potential in biomedical application.

Controlling the degradation of cellulose scaffolds with Malaprade oxidation for tissue engineering

Cellulose scaffolds, whose biodegradation can be controlled through the reaction with amine compounds in the human body, were developed for tissue engineering applications.

Oxidized Dextran as a Macromolecular Crosslinker Stabilizes the Zein/Caseinate Nanocomplex for the Potential Oral Delivery of Curcumin

In this study, we prepared complex nanoparticles from a combination of two proteins and one polysaccharide for the encapsulation and delivery of lipophilic bioactive compounds. Two proteins, zein and sodium caseinate (NaCas), provided a hydrophobic core for the encapsulation of a lipophilic compound (curcumin), while a polysaccharide dialdehyde, oxidized dextran, served as the coating material and macromolecular crosslinker to create covalent linkage with two proteins for stabilization purposes. The heating time and crosslinker concentration were optimized to achieve the desirable colloidal stability in simulated gastric and intestinal fluids. Our results suggested that heating time played a more important role than the concentration of oxidized dextran. The optimized complex nanoparticles had a particle size of around 150 nm with a PDI < 0.1 and negative surface charge. Morphological observation by transmission electron microscopy revealed a spherical shape and uniform size distribution. Fourier transform infrared and fluorescence spectroscopies evidenced the formation of Schiff base complex, confirming the validity of covalent crosslinking. Furthermore, the complex nanoparticles demonstrated superior encapsulation properties for curcumin, showing an efficiency of >90% at 10% loading. A rather slow kinetic release profile of curcumin from complex nanoparticles was observed under simulated gastrointestinal conditions. The complex nanoparticles prepared from zein, NaCas, and oxidized dextran hold promising potential for the oral delivery of lipophilic bioactive compounds.

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.

Biodegradable pH-sensitive prospidine-loaded dextran phosphate based hydrogels for local tumor therapy

The paper focuses on the development of drug delivery systems based on hydrogels of dextran phosphate (DP) for local cancer therapy. The hydrogels were characterized by physicochemical properties including functional group content, morphology, gel fraction, pH-responsive swelling. The desirable pH-sensitive drug release behavior of these hydrogels was demonstrated by a drug release test with Prospidine-loaded hydrogels (DP-Pr hydrogels) at different pH values. In vitro degradation of the DP-Pr hydrogels was determined under simulated physiological conditions. The cytotoxicity of the blank DP hydrogels and DP-Pr hydrogels with different Pr concentrations was evaluated with HeLa and HЕр-2 cells. Investigations of antitumor efficiency in vivo showed that administration of DP-Pr hydrogels in comparison with an aqueous solution of Pr results in the increase of antitumor activity, prolongation of therapeutic action and growth of a number of animals cured. Therefore, such pH-responsive DP hydrogels could be promising candidates as drug delivery carriers.

Preparation and Characterization of Oxidized Inulin Hydrogel for Controlled Drug Delivery

Inulin-based hydrogels are useful carriers for the delivery of drugs in the colon-targeted system and in other biomedical applications. In this project, inulin hydrogels were fabricated by crosslinking oxidized inulin with adipic acid dihydrazide (AAD) without the use of a catalyst or initiator. The physicochemical properties of the obtained hydrogels were further characterized using different techniques, such as swelling experiments, in vitro drug release, degradation, and biocompatibility tests. The crosslinking was confirmed with Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), and differential scanning calorimetry (DSC). In vitro releases of 5-fluorouracil (5FU) from the various inulin hydrogels was enhanced in acidic conditions (pH 5) compared with physiological pH (pH 7.4). In addition, blank gels did not show any appreciable cytotoxicity, whereas 5FU-loaded hydrogels demonstrated efficacy against HCT116 colon cancer cells, which further confirms the potential use of these delivery platforms for direct targeting of 5-FU to the colon.

Dextran Aldehyde in Biocatalysis: More Than a Mere Immobilization System

Dextran aldehyde (dexOx), resulting from the periodate oxidative cleavage of 1,2-diol moiety inside dextran, is a polymer that is very useful in many areas, including as a macromolecular carrier for drug delivery and other biomedical applications. In particular, it has been widely used for chemical engineering of enzymes, with the aim of designing better biocatalysts that possess improved catalytic properties, making them more stable and/or active for different catalytic reactions. This polymer possesses a very flexible hydrophilic structure, which becomes inert after chemical reduction; therefore, dexOx comes to be highly versatile in a biocatalyst design. This paper presents an overview of the multiple applications of dexOx in applied biocatalysis, e.g., to modulate the adsorption of biomolecules on carrier surfaces in affinity chromatography and biosensors design, to serve as a spacer arm between a ligand and the support in biomacromolecule immobilization procedures or to generate artificial microenvironments around the enzyme molecules or to stabilize multimeric enzymes by intersubunit crosslinking, among many other applications.

Injectable in situ dual-crosslinking hyaluronic acid and sodium alginate based hydrogels for drug release

A series of injectable in situ dual-crosslinking hydrogels (HA/ALG) based on oxidized sodium alginate (oxi-ALG) and hyaluronic acid modified with thiol and hydrazide (HA-SH/CDH) were prepared via hydrazone bonds and disulfide bonds. The chemical structures, morphologies, rheological properties, gelling time, swelling ratio, degradation rate and drug release behavior of hydrogels were investigated. HA/ALG hydrogels exhibited tunable gelling time, rheological properties, swelling ratio and degradation rate with varying precursor concentrations. The gelling time of HA/ALG hydrogels ranged from 157 s to 955 s, the values of yield stress of HA2/ALG2, HA3/ALG3 and HA4/ALG4 hydrogels were 1724, 4349 and 5306 Pa, and the degradation percentage of HA2/ALG2, HA3/ALG3 and HA4/ALG4 hydrogels were about 64%, 51% and 42% after incubating 35 days, respectively. Bovine serum albumin (BSA) was used as a model drug to investigate the drug controlled release properties, and the in vitro cumulative release percentage of BSA from HA2/ALG2, HA3/ALG3 and HA4/ALG4 drug-loaded hydrogels were about 79%, 72% and 69% after 20 days. The series of injectable in situ dual-crosslinking HA/ALG hydrogels could be an attractive candidate for drug delivery system, tissue engineering and regenerative medicine.