The Diels-Alder Cross-Linked Gelatin/Dextran Nanocomposite Hydrogels with Silver Nanoparticles for Wound Healing Applications: Synthesis, Characterization, and In Vitro Evaluation.

Wound healing involves a sophisticated biological process that relies on ideal conditions to advance through various stages of repair. Modern wound dressings are designed to imitate the natural surroundings around cells and offer properties such as moisture regulation, strength, and antimicrobial defense to boost healing. A recent research project unveiled a new type of gelatin (Gel)/dextran (Dex) hydrogels, linked through Diels-Alder (D-A) reactions, loaded with silver nanoparticles (Ag-NPs) for cutting-edge wound treatment. Gel and Dex were chemically modified to form the hydrogels via the D-A reaction. The hydrogels were enriched with Ag-NPs at varying levels. Thorough analyses of the hydrogels using methods like NMR, FT-IR, and SEM were carried out to assess their structure and nanoparticle integration. Rheological tests displayed that the hydrogels had favorable mechanical attributes, particularly when Ag-NPs were included. The hydrogels demonstrated controlled swelling, responsiveness to pH changes, and were non-toxic. Testing against E. coli showcased the strong antibacterial activity of the nanocomposite hydrogels in a concentration-dependent manner. This investigation showcased the promise of these bioactive nanocomposite hydrogels in promoting speedy wound healing by maintaining a moist environment, offering an antimicrobial shield, and ensuring mechanical support at the wound site.

Exploring the Progress of Hyaluronic Acid Hydrogels: Synthesis, Characteristics, and Wide-Ranging Applications.

This comprehensive review delves into the world of hyaluronic acid (HA) hydrogels, exploring their creation, characteristics, research methodologies, and uses. HA hydrogels stand out among natural polysaccharides due to their distinct features. Their exceptional biocompatibility makes them a top choice for diverse biomedical purposes, with a great ability to coexist harmoniously with living cells and tissues. Furthermore, their biodegradability permits their gradual breakdown by bodily enzymes, enabling the creation of temporary frameworks for tissue engineering endeavors. Additionally, since HA is a vital component of the extracellular matrix (ECM) in numerous tissues, HA hydrogels can replicate the ECM's structure and functions. This mimicry is pivotal in tissue engineering applications by providing an ideal setting for cellular growth and maturation. Various cross-linking techniques like chemical, physical, enzymatic, and hybrid methods impact the mechanical strength, swelling capacity, and degradation speed of the hydrogels. Assessment tools such as rheological analysis, electron microscopy, spectroscopy, swelling tests, and degradation studies are employed to examine their attributes. HA-based hydrogels feature prominently in tissue engineering, drug distribution, wound recovery, ophthalmology, and cartilage mending. Crafting HA hydrogels enables the production of biomaterials with sought-after qualities, offering avenues for advancements in the realm of biomedicine.

Self-Signal-Triggered Drug Delivery System for Tumor Therapy Using Cancer Cell Membrane-Coated Biocompatible Mn3O4 Nanocomposites.

In anti-cancer metastasis treatment, precise drug delivery to cancer cells remains a challenge. Innovative nanocomposites are developed to tackle these issues effectively. The approach involves the creation of manganese oxide (Mn3O4) nanoparticles (NPs) and their functionalization using trisodium citrate to yield functionalized Mn3O4 NPs (F-Mn3O4 NPs), with enhanced water solubility, stability, and biocompatibility. Subsequently, the chemotherapeutic drug doxorubicin (DOX) is encapsulated with Mn3O4 NPs, resulting in DOX/Mn3O4 NPs. To achieve cell-specific targeting, These NPs are coated with HeLa cell membranes (HCM), forming HCM/DOX/Mn3O4. For further refinement, a transferrin (Tf) receptor is integrated with cracked HCM to create Tf-HCM/DOX/Mn3O4 nanocomposites (NC) with specific cell membrane targeting capabilities. The resulting Tf-HCM/DOX/Mn3O4 NC exhibits excellent drug encapsulation efficiency (97.5%) and displays triggered drug release when exposed to NIR laser irradiation in the tumor's environment (pH 5.0 and 6.5). Furthermore, these nanocomposites show resistance to macrophage uptake and demonstrate homotypic cancer cell targeting specificity, even in the presence of other tumor cells. In vitro toxicity tests show that Tf-HCM/DOX/Mn3O4 NC achieves significant anticancer activity against HeLa and BT20 cancer cells, with percentages of 76.46% and 71.36%, respectively. These results indicate the potential of Tf-HCM/DOX/Mn3O4 NC as an effective nanoplatform for chemo-photothermal therapy.

Injectable and Multifunctional Hydrogels Based on Poly(N-acryloyl glycinamide) and Alginate Derivatives for Antitumor Drug Delivery.

Chemotherapy is a conventional treatment that uses drugs to kill cancer cells; however, it may induce side effects and may be incompletely effective, leading to the risk of tumor recurrence. To address this issue, we developed novel injectable thermal/near-infrared (NIR)-responsive hydrogels to control drug release. The injectable hydrogel formulation was composed of biocompatible alginates, poly(N-acryloyl glycinamide) (PNAGA) copolymers with an upper critical solution temperature, and NIR-responsive cross-linkers containing coumarin groups, which were gelated through bioorthogonal inverse electron demand Diels-Alder reactions. The hydrogels exhibited quick gelation times (120-800 s) and high drug loading efficiencies (>90%). The hydrogels demonstrated a higher percentage of drug release at 37 °C than that at 25 °C due to the enhanced swelling behavior of temperature-responsive PNAGA moieties. Upon NIR irradiation, the hydrogels released most of the entrapped doxorubicin (DOX) (97%) owing to the cleavage of NIR-sensitive coumarin ester groups. The hydrogels displayed biocompatibility with normal cells, while induced antitumor activity toward cancer cells. DOX/hydrogels treated with NIR light inhibited tumor growth in nude mice bearing tumors. In addition, the injected hydrogels emitted red fluorescence upon excitation at a green wavelength, so that the drug delivery and hydrogel degradation in vivo could be tracked in the xenograft model.

NIR-responsive carboxymethyl-cellulose hydrogels containing thioketal-linkages for on-demand drug delivery system.

Near-infrared (NIR) light-responsive hydrogels have emerged as a highly promising strategy for effective anticancer therapy owing to the remotely controlled release of chemotherapeutic molecules with minimal invasive manner. In this study, novel NIR-responsive hydrogels were developed from reactive oxygen species (ROS)-cleavable thioketal cross-linkers which possessed terminal tetrazine groups to undergo a bio-orthogonal inverse electron demand Diels Alder click reaction with norbornene modified carboxymethyl cellulose. The hydrogels were rapidly formed under physiological conditions and generated N2 gas as a by-product, which led to the formation of porous structures within the hydrogel networks. A NIR dye, indocyanine green (ICG) and chemotherapeutic doxorubicin (DOX) were co-encapsulated in the porous network of the hydrogels. Upon NIR-irradiation, the hydrogels showed spatiotemporal release of encapsulated DOX (>96 %) owing to the cleavage of thioketal bonds by interacting with ROS generated from ICG, whereas minimal release of encapsulated DOX (<25 %) was observed in the absence of NIR-light. The in vitro cytotoxicity results revealed that the hydrogels were highly cytocompatible and did not induce any toxic effect on the HEK-293 cells. In contrast, the DOX + ICG-encapsulated hydrogels enhanced the chemotherapeutic effect and effectively inhibited the proliferation of Hela cancer cells when irradiated with NIR-light.

Application of Cartilage Extracellular Matrix to Enhance Therapeutic Efficacy of Methotrexate.

BACKGROUND: Rheumatoid arthritis (RA) is characterized by chronic inflammation and joint damage. Methotrexate (MTX), a commonly used disease-modifying anti-rheumatic drug (DMARD) used in RA treatment. However, the continued use of DMARDs can cause adverse effects and result in limited therapeutic efficacy. Cartilage extracellular matrix (CECM) has anti-inflammatory and anti-vascular effects and promotes stem cell migration, adhesion, and differentiation into cartilage cells. METHODS: CECM was assessed the dsDNA, glycosaminoglycan, collagen contents and FT-IR spectrum of CECM. Furthermore, we determined the effects of CECM and MTX on cytocompatibility in the SW 982 cells and RAW 264.7 cells. The anti-inflammatory effects of CECM and MTX were assessed using macrophage cells. Finally, we examined the in vivo effects of CECM in combination with MTX on anti-inflammation control and cartilage degradation in collagen-induced arthritis model. Anti-inflammation control and cartilage degradation were assessed by measuring the serum levels of RA-related cytokines and histology. RESULTS: CECM in combination with MTX had no effect on SW 982, effectively suppressing only RAW 264.7 activity. Moreover, anti-inflammatory effects were enhanced when low-dose MTX was combined with CECM. In a collagen-induced arthritis model, low-dose MTX combined with CECM remarkably reduced RA-related and pro-inflammatory cytokine levels in the blood. Additionally, low-dose MTX combined with CECM exerted the best cartilage-preservation effects compared to those observed in the other therapy groups. CONCLUSION: Using CECM as an adjuvant in RA treatment can augment the therapeutic effects of MTX, reduce existing drug adverse effects, and promote joint tissue regeneration.

Facile Fabrication of NIR-Responsive Alginate/CMC Hydrogels Derived through IEDDA Click Chemistry for Photothermal-Photodynamic Anti-Tumor Therapy.

Novel chemically cross-linked hydrogels derived from carboxymethyl cellulose (CMC) and alginate (Alg) were prepared through the utilization of the norbornene (Nb)-methyl tetrazine (mTz) click reaction. The hydrogels were designed to generate reactive oxygen species (ROS) from an NIR dye, indocyanine green (ICG), for combined photothermal and photodynamic therapy (PTT/PDT). The cross-linking reaction between Nb and mTz moieties occurred via an inverse electron-demand Diels-Alder chemistry under physiological conditions avoiding the need for a catalyst. The resulting hydrogels exhibited viscoelastic properties (G' ~ 492-270 Pa) and high porosity. The hydrogels were found to be injectable with tunable mechanical characteristics. The ROS production from the ICG-encapsulated hydrogels was confirmed by DPBF assays, indicating a photodynamic effect (with NIR irradiation at 1-2 W for 5-15 min). The temperature of the ICG-loaded hydrogels also increased upon the NIR irradiation to eradicate tumor cells photothermally. In vitro cytocompatibility assessments revealed the non-toxic nature of CMC-Nb and Alg-mTz towards HEK-293 cells. Furthermore, the ICG-loaded hydrogels effectively inhibited the metabolic activity of Hela cells after NIR exposure.

Reduction-Responsive Chitosan-Based Injectable Hydrogels for Enhanced Anticancer Therapy.

Selective delivery of anticancer drug molecules to the tumor site enhances local drug dosages, which leads to the death of cancer cells while simultaneously minimizing the negative effects of chemotherapy on other tissues, thereby improving the patient's quality of life. To address this need, we developed reduction-responsive chitosan-based injectable hydrogels via the inverse electron demand Diels-Alder reaction between tetrazine groups of disulfide-based cross-linkers and norbornene groups of chitosan derivatives, which were applied to the controlled delivery of doxorubicin (DOX). The swelling ratio, gelation time (90-500 s), mechanical strength (G'~350-850 Pa), network morphology, and drug-loading efficiency (≥92%) of developed hydrogels were investigated. The in vitro release studies of the DOX-loaded hydrogels were performed at pH 7.4 and 5.0 with and without DTT (10 mM). The biocompatibility of pure hydrogel and the in vitro anticancer activity of DOX-loaded hydrogels were demonstrated via MTT assay on HEK-293 and HT-29 cancer cell lines, respectively.

The effect of molecular weight and chemical structure of cross-linkers on the properties of redox-responsive hyaluronic acid hydrogels.

In this work, we investigated the effect of the size and the chemical structure of crosslinkers on the properties of hyaluronic acid-based hydrogels prepared via an inverse electron demand Diels-Alder reaction. Hydrogels having loose and dense networks were designed by cross-linkers with and without polyethylene glycol (PEG) spacers of different molecular weights (1000 and 4000 g/mol). The study showed that the properties of hydrogels such as swelling ratios (20-55 times), morphology, stability, mechanical strength (storage modulus in the range 175-858 Pa), and drug loading efficiency (87 % ~ 90 %) were greatly influenced by the addition of PEG and changing its molecular weight in the cross-linker. Particularly, the presence of PEG chains in redox- responsive crosslinkers increased the doxorubicin release (85 %, after 168 h) and the degradation rate (96 %, after 10 d) of hydrogels in the simulated reducing medium (10 mM DTT). The in vitro cytotoxicity experiments conducted for HEK-293 cells revealed that the formulated hydrogels were biocompatible, which could be a promising candidate for drug delivery applications.

Redox-Responsive Comparison of Diselenide and Disulfide Core-Cross-Linked Micelles for Drug Delivery Application.

In this study, diselenide (Se-Se) and disulfide (S-S) redox-responsive core-cross-linked (CCL) micelles were synthesized using poly(ethylene oxide)2k-b-poly(furfuryl methacrylate)1.5k (PEO2k-b-PFMA1.5k), and their redox sensitivity was compared. A single electron transfer-living radical polymerization technique was used to prepare PEO2k-b-PFMA1.5k from FMA monomers and PEO2k-Br initiators. An anti-cancer drug, doxorubicin (DOX), was incorporated into PFMA hydrophobic parts of the polymeric micelles, which were then cross-linked with maleimide cross-linkers, 1,6-bis(maleimide) hexane, dithiobis(maleimido) ethane and diselenobis(maleimido) ethane via Diels-Alder reaction. Under physiological conditions, the structural stability of both S-S and Se-Se CCL micelles was maintained; however, treatments with 10 mM GSH induced redox-responsive de-cross-linking of S-S and Se-Se bonds. In contrast, the S-S bond was intact in the presence of 100 mM H2O2, while the Se-Se bond underwent de-crosslinking upon the treatment. DLS studies revealed that the size and PDI of (PEO2k-b-PFMA1.5k-Se)2 micelles varied more significantly in response to changes in the redox environment than (PEO2k-b-PFMA1.5k-S)2 micelles. In vitro release studies showed that the developed micelles had a lower drug release rate at pH 7.4, whereas a higher release was observed at pH 5.0 (tumor environment). The micelles were non-toxic against HEK-293 normal cells, which revealed that they could be safe for use. Nevertheless, DOX-loaded S-S/Se-Se CCL micelles exhibited potent cytotoxicity against BT-20 cancer cells. Based on these results, the (PEO2k-b-PFMA1.5k-Se)2 micelles can be more sensitive drug carriers than (PEO2k-b-PFMA1.5k-S)2 micelles.

Redox-Responsive Core-Cross-Linked Micelles of Miktoarm Poly(ethylene oxide)-b-poly(furfuryl methacrylate) for Anticancer Drug Delivery.

The physiological instability of nanocarriers, premature drug leakage during blood circulation, and associated severe side effects cause compromised therapeutic efficacy, which have significantly hampered the progress of nanomedicines. The cross-linking of nanocarriers while keeping the effectiveness of their degradation at the targeted site to release the drug has emerged as a potent strategy to overcome these flaws. Herein, we have designed novel (poly(ethylene oxide))2-b-poly(furfuryl methacrylate) ((PEO2K)2-b-PFMAnk) miktoarm amphiphilic block copolymers by coupling alkyne-functionalized PEO (PEO2K-C≡H) and diazide-functionalized poly(furfuryl methacrylate) ((N3)2-PFMAnk) via click chemistry. (PEO2K)2-b-PFMAnk self-assembled to form nanosized micelles (mikUCL) with hydrodynamic radii in the range of 25∼33 nm. The hydrophobic core of mikUCL was cross-linked by a disulfide-containing cross-linker using the Diels-Alder reaction to avoid unwanted leakage and burst release of a payload. As expected, the resulting core-cross-linked (PEO2K)2-b-PFMAnk micelles (mikCCL) exhibited superior stability under a normal physiological environment and were de-cross-linked to rapidly release doxorubicin (DOX) upon exposure to a reduction environment. The micelles were compatible with HEK-293 normal cells, while DOX-loaded micelles (mikUCL/DOX and mikCCL/DOX) induced high antitumor activity in HeLa and HT-29 cells. mikCCL/DOX preferentially accumulated at the tumor site and was more efficacious than free DOX and mikUCL/DOX for tumor inhibition in HT-29 tumor-bearing nude mice.

Indole-3-carbinol induces apoptosis in AGS cancer cells via mitochondrial pathway.

Indole-3-carbinol is produced from the cruciferous vegetables and broadly investigated for their various biological effects in in-vitro and in-vivo aspects. However, the anticancer activity of I3C and its molecular mechanisms have not been investigated in human adeno gastro carcinoma (AGS) cells. In our study of AGS cells, nuclear condensation was observed by 4',6-diamidino-2-phenylindole (DAPI) staining, cell death was confirmed by a cell viability assay, and fragmented DNA was observed at the IC50 dose by a DNA fragmentation assay. Apoptosis was evaluated by the qPCR technique. Treatment of the AGS cells with I3C at different concentrations has drastically decreased cell proliferation and differentiation. By releasing cytochrome-c from mitochondria in the intrinsic pathway, I3C prevents the multiplication of AGS cells and initiates apoptosis. The WST-1 assay result showed that I3C treatment against AGS cells had considerably reduced the viability of the cells. Furthermore, RT-qPCR showed the fold change among the expressed proteins compared with reference gene ß-actin. Molecular docking revealed that I3C showed a strong binding affinity for the apoptotic protein 3DCY. The results show the caspase group of proteins contribute to the core of apoptotic machinery. I3C and its metabolites target a variety of components of cell-cycle control via distinct signaling pathways in light of the rapid development of tumors and oncogenesis. The translational significance of I3C and its metabolites in cancer is highlighted by their wide range of antitumor activity and low toxicity. Furthermore, the novel prodrug I3C, which has overlapping underlying mechanisms, could encourage new strategies to decrease oncogenesis.

NIR-degradable and biocompatible hydrogels derived from hyaluronic acid and coumarin for drug delivery and bio-imaging.

In this work, bioorthogonal and photodegradable hydrogels derived from norbornene (Nb) functionalized hyaluronic acid and a water soluble coumarin-based cross-linker possessing terminal tetrazine (Tz) groups, were developed for NIR-responsive release of doxorubicin (DOX). The inverse electron demand Diels-Alder cross-linking reaction between Nb and Tz functionalities formed the hydrogels at physiological conditions, whereas N2 gas liberated during the reaction created pores in the hydrogels. The gelation time ranges (about 5-20 min) and the viscoelastic behavior (G' ~ 346-1380 Pa) demonstrated that the resulting hydrogels were injectable and possessed tunable mechanical properties. Moreover, hydrogels released the encapsulated DOX upon NIR irradiation, owing to the NIR-responsive cleavage of coumarin-ester, and consequently, induced anti-tumor activity in BT-20 cancer cells. Additionally, the hydrogels could be excited at various wavelengths of the visible spectrum and can emit green to red fluorescence, demonstrating their simultaneous photo-responsive drug release and bio-imaging applications.

Tissue Engineered Mini-Cornea Model for Eye Irritation Test.

BACKGROUND: Eye irritation tests with animals have been conducted for a long time. However, the subjective decision to irritation, the anatomic/physiologic difference between species and humans, and ethical issues are crucial problems. Various research groups have paid attention to alternative testing methods. In these senses, we fabricated in vitro mini-cornea models with immortalized human corneal epithelial cells (iHCECs) and keratocytes (iHCKs) and used them for irritation tests. This study hypothesized that our mini-cornea model could present different viability tendencies according to test chemicals with different irritancy levels. METHODS: Cells used in this study were characterized with cornea-specific markers by immunocytochemistry and western blot. To make a three-dimensional hemisphere construct like cornea stroma, we cultured iHCKs under modified culture conditions verified by matrix formation and total collagen content. iHCECs were seeded on the construct and cultured at an air-liquid interface. The model was treated with 2-phenoxyethanol, triton X-100, sodium lauryl sulfate, and benzalkonium chloride. RESULTS: iHCECs and iHCKs presented their specific cell markers. In modifying the culture condition, the group treating ascorbic acid (200 µg/ml) presented an intact cellular matrix and included the highest collagen content; thus, we used this condition to fabricate the mini-cornea model. The model shows hemisphere shape and homogenous cell distributions in histological analysis. We observed different sensitivity tendencies by types of chemicals, and the model's viability significantly decreased when the chemical concentration increased. CONCLUSION: In this study, we performed and observed irritation tests using a tissue-engineered mini-cornea model and considered to apply as an alternative approach for animal tests.

Anti-Osteoarthritic Effects of Cartilage-Derived Extracellular Matrix in a Rat Osteoarthritis Model.

BACKGROUND: The extracellular matrix (ECM) has many functions, such as segregating tissues, providing support, and regulating intercellular communication. Cartilage-derived ECM (CECM) can be prepared via consecutive processes of chemical decellularization and enzyme treatment. The purpose of this study was to improve and treat osteoarthritis (OA) using porcine knee articular CECM. METHODS: We assessed the rheological characteristics and pH of CECM solutions. Furthermore, we determined the effects of CECM on cell proliferation and cytotoxicity in the chondrocytes of New Zealand rabbits. The inhibitory effect of CECM on tumor necrosis factor (TNF)-α-induced cellular apoptosis was assessed using New Zealand rabbit chondrocytes and human synoviocytes. Finally, we examined the in vivo effects of CECM on inflammation control and cartilage degradation in an experimental OA-induced rat model. The rat model of OA was established by injecting monosodium iodoacetate into the intra-articular knee joint. The rats were then injected with CECM solution. Inflammation control and cartilage degradation were assessed by measuring the serum levels of proinflammatory cytokines and C-telopeptide of type II collagen and performing a histomorphological analysis. RESULTS: CECM was found to be biocompatible and non-immunogenic, and could improve cell proliferation without inducing a toxic reaction. CECM significantly reduced cellular apoptosis due to TNF-α, significantly improved the survival of cells in inflammatory environments, and exerted anti-inflammatory effects. CONCLUSION: Our findings suggest that CECM is an appropriate injectable material that mediates OA-induced inflammation.

Fast Absorbent and Highly Bioorthogonal Hydrogels Developed by IEDDA Click Reaction for Drug Delivery Application.

In this work, we engineered highly biocompatible and fast absorbent injectable hydrogels derived from norbornene (Nb)-functionalized hyaluronic acid (HA-Nb) and a water-soluble cross-linker possessing tetrazine (Tz) functional groups on both ends of polyethylene glycol (PEG-DTz). The by-product (nitrogen gas) of the inverse electron demand Diels−Alder (IEDDA) cross-linking reaction carved porosity in the resulting hydrogels. By varying the molar ratio of HA-Nb and PEG-DTz (Nb:Tz = 10:10, 10:5, 10:2.5), we were able to formulate hydrogels with tunable porosity, gelation time, mechanical strength, and swelling ratios. The hydrogels formed quickly (gelation time < 100 s), offering a possibility to use them as an injectable drug delivery system. The experimental data showed rapid swelling and a high swelling ratio thanks to the existence of PEG chains and highly porous architectures of the hydrogels. The hydrogels were able to encapsulate a high amount of curcumin (~99%) and released the encapsulated curcumin in a temporal pattern. The PEG-DTz cross-linker, HA-Nb, and the resulting hydrogels showed no cytotoxicity in HEK-293 cells. These fast absorbent hydrogels with excellent biocompatibility fabricated from HA-Nb and the IEDDA click-able cross-linker could be promising drug carriers for injectable drug delivery applications.

Reduction-responsive and bioorthogonal carboxymethyl cellulose based soft hydrogels cross-linked via IEDDA click chemistry for cancer therapy application.

In this work, novel biocompatible and reduction-responsive soft hydrogels were formulated from norbornene (Nb)-functionalized carboxymethyl cellulose (CMCNb). To cross-link the CMC-Nb via a highly bioorthogonal inverse electron demand Diels-Alder (IEDDA) reaction, we employed a water-soluble and reduction-responsive diselenide-based cross-linker possessing two terminal tetrazine (Tz) groups with varying molar concentrations (Nb/Tz molar ratios of 10/10, 10/05, and 10/2.5). The N2 microbubbles liberated as a by-product during the IEDDA reaction generated in-situ pores in hydrogel networks. The resulting hydrogels had highly porous structures and relatively soft mechanical properties (storage moduli in the range 74 ⁓160 Pa). The hydrogels showed high swelling ratios (>35 times), tunable gelation times (1-5 min), and excellent doxorubicin (DOX) loading efficiencies (>85 %). The hydrogels exhibited stimuli-responsive and fast release of DOX (99 %, after 12 h) in the presence of 10 mmol of glutathione as compared to the normal PBS solution (38 %). The cytotoxic effects of blank hydrogels were not observed against HEK-239 cells, while the DOX-encapsulated hydrogels exhibited anti-tumor activity in BT-20 cancer cells. The results indicate potential applications of the CMC-based soft hydrogels in injectable drug delivery systems.

Dual cross-linked chitosan/alginate hydrogels prepared by Nb-Tz 'click' reaction for pH responsive drug delivery.

A novel physically and chemically double-crosslinked hydrogel derived from chitosan oligosaccharide/alginate (COS/Alg) was developed by using norbornene (Nb)-tetrazine (Tz) click reaction for ketoprofen delivery. The properties of the hydrogel were evaluated by rheological, FTIR, TGA, XRD, SEM, swelling and drug release studies. The Nb-Tz chemical cross-linking facilitated outstanding hydrophobic drug loading (44% wt/wt of ketoprofen) and sustained release through a hydrophobic interaction mechanism between the drug and the used polysaccharides. The COS/Alg electrostatics network (10/10 of NH2/COOH molar ratio) generated the pH responsiveness, suppressing the release in simulated gastric fluid (below 10% for 2 h) and enhancing the release in simulated intestinal fluids (up to 84% for 24 h). The prepared hydrogel was non-toxic to human HEK-293 cells (95% cell viability). This work opens up a potential approach for preparing hydrophilic hydrogels from natural polysaccharides that can be used in the delivery of hydrophobic drugs.

Multi-stimuli responsive hydrogels derived from hyaluronic acid for cancer therapy application.

One of the most promising strategies for the controlled release of therapeutic molecules is stimuli-responsive and biodegradable hydrogels developed from natural polymers. However, current strategies to development stimuli-responsive hydrogels lack precise control over drug release profile and use cytotoxic materials during preparation. To address these issues, multi-stimuli responsive hydrogels derived from hyaluronic acid and diselenide based cross-linker were developed for the controlled release of doxorubicin (DOX). Hydrogels were rapidly formed via an inverse electron demand Diels-Alder click chemistry and encapsulated DOX/indocyanine green (ICG) in their porous networks. The hydrogels showed a rapid release of DOX in acidic (pH 5), reducing (10 mmol DTT), and oxidizing medium (0.5% H2O2), and after NIR irradiation. The in vitro experiments demonstrated that hydrogels were highly cytocompatible and the DOX-loaded hydrogels induced similar anti-tumor effect as compared to that of the free-DOX. Furthermore, DOX + ICG loaded hydrogels increased the antitumor efficacy of DOX after NIR irradiation.

Injectable and biocompatible alginate-derived porous hydrogels cross-linked by IEDDA click chemistry for reduction-responsive drug release application.

In this work, novel injectable and reduction-responsive hydrogels were successfully prepared via inverse electron demand Diels-Alder reaction between alginate-norbornene and a water-soluble PEG based disulfide cross-linker. The reduction-responsive cross-linker was designed to contain a PEG chain within two disulfide linkages, and two terminal tetrazine groups. The resulting hydrogels possessed high swelling ratios, porous morphology, excellent drug loading efficiency (~92%), and suitable mechanical properties. The drug release experiments demonstrated that the hydrogels released more than 90% of the encapsulated doxorubicin (DOX) in the presence of 10 mM glutathione while a minimal DOX release (<25%) was measured in physiological buffer (PBS, pH = 7.4) after 11 d. The cross-linker and hydrogels did not exhibit any apparent cytotoxicity to fibroblast cells. In contrast, DOX-loaded hydrogels induced anti-tumor activity against cancer cells. The injectable and reduction-responsive hydrogels hold great potential as a biomaterial for stimuli responsive drug delivery applications.