Redox-Responsive Gold Nanoparticles Coated with Hyaluronic Acid and Folic Acid for Application in Targeting Anticancer Therapy.

Methotrexate (MTX) has poor water solubility and low bioavailability, and cancer cells can become resistant to it, which limits its safe delivery to tumor sites and reduces its clinical efficacy. Herein, we developed novel redox-responsive hybrid nanoparticles (NPs) from hyaluronic acid (HA) and 3-mercaptopropionic acid (MPA)-coated gold NPs (gold@MPA NPs), which were further conjugated with folic acid (FA). The design of FA-HA-ss-gold NPs aimed at enhancing cellular uptake specifically in cancer cells using an active FA/HA dual targeting strategy for enhanced tumor eradication. MTX was successfully encapsulated into FA-HA-ss-gold NPs, with drug encapsulation efficiency (EE) as high as >98.7%. The physicochemical properties of the NPs were investigated in terms of size, surface charges, wavelength reflectance, and chemical bonds. MTX was released in a sustained manner in glutathione (GSH). The cellular uptake experiments showed effective uptake of FA-HA-ss-gold over HA-ss-gold NPs in the deep tumor. Moreover, the release studies provided strong evidence that FA-HA-ss-gold NPs serve as GSH-responsive carriers. In vitro, anti-tumor activity tests showed that FA-HA-ss-gold/MTX NPs exhibited significantly higher cytotoxic activity against both human cervical cancer (HeLa) cells and breast cancer (BT-20) cells compared to gold only and HA-ss-gold/MTX NPs while being safe for human embryonic kidney (HEK-293) cells. Therefore, this present study suggests that FA-HA-ss-gold NPs are promising active targeting hybrid nanocarriers that are stable, controllable, biocompatible, biodegradable, and with enhanced cancer cell targetability for the safe delivery of hydrophobic anticancer drugs.

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.

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.

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.

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.

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.

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.

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.

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.

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.