Optimization of thermoresponsive chitosan/β-glycerophosphate hydrogels for injectable neural tissue engineering application

A thermosensitive chitosan hydrogel loaded with Thonningianin A nanoparticles promotes diabetic wound healing by modulating oxidative stress and angiogenesis

Diabetic wounds are difficult to heal because of persistent oxidative stress and limited angiogenesis. However, traditional wound dressings cannot address these issues simultaneously. In this study, a thermosensitive chitosan (CS) hydrogel loaded with Thonningianin A (TA) nanoparticles (TA-NPs) was constructed. First, TA-NPs were developed via the nanoprecipitation technique. CS was subsequently combined with β‑sodium glycerophosphate (β-GP) to prepare a thermosensitive hydrogel matrix (CS/β-GP). Finally, composite hydrogels (TA-NPs@Gel) with antioxidant and angiogenesis-promoting properties were synthesized by incorporating TA-NPs into a CS/β-GP hydrogel matrix. Characterization revealed that the TA-NPs were uniformly spherical, with a particle size of 186.30 ± 1.15 nm and a zeta potential of -35.07 ± 0.61 mV. Scanning electron microscopy and Fourier transform infrared spectroscopy confirmed the successful integration of TA-NPs into the hydrogel matrix. Both in vitro and in vivo studies demonstrated that TA-NPs@Gel exhibited potent antioxidant and angiogenic effects, significantly accelerating wound healing in a diabetic mouse model. Network pharmacology predictions indicated that TA-NPs@Gel promoted diabetic wound healing through the HIF-1 signaling pathway. Overall, the integration of TA-NPs into a hydrogel system has broad therapeutic potential for the treatment of diabetic wounds.

A novel approach for the co-delivery of 5-fluorouracil and everolimus for breast cancer combination therapy: stimuli-responsive chitosan hydrogel embedded with mesoporous silica nanoparticles

BACKGROUND

Breast cancer remains one of the leading causes of death among women globally, with traditional therapies often limited by challenges such as drug resistance and significant side effects. Combination therapies, coupled with nanotechnology-based co-delivery systems, offer enhanced efficacy by targeting multiple pathways in cancer progression. In this study, we developed an injectable, stimuli-responsive nanosystem using a chitosan hydrogel embedded with mesoporous silica nanoparticles for the co-administration of 5-fluorouracil and everolimus. This approach aims to optimize controlled drug release, enhance the synergistic anticancer effect, and overcome challenges associated with co-loading different therapeutic agents.

METHODS

Various techniques were employed to characterize the nanoparticles and the hydrogel. Cell uptake, apoptosis, and proliferation of 4T1 breast cancer cells were evaluated by flow cytometry and Resazurin assay, respectively. The Balb/C mice model of breast cancer, which received the therapeutical nanoplatforms subcutaneously near the tumoral region was used to examine tumor size and lung metastases.

RESULTS

The results revealed that the nanoparticles had a suitable loading capacity and high cellular uptake. The drug release was pH-sensitive and synergistic. By incorporating nanoparticles into the hydrogel, the cell death rate and apoptosis of 4T1 breast cancer cells increased significantly, due to the synergistic effects of co-delivered drugs. Additionally, the combination treatment groups showed a significant reduction in tumor size and lung metastasis compared to the monotherapy and control groups.

CONCLUSIONS

These findings underscore the potential of the nanocomposite used to develop a novel co-delivery system to enhance therapeutic outcomes, reduce side effects, and provide a promising new strategy for future cancer treatments.

Curdlan/chitosan NIR-responsive in situ forming gel: An injectable scaffold for the treatment of epiphyseal plate injury

Premature closure of the epiphyseal plate inducing by the formation of bone bridges after epiphyseal plate injury, can lead to limb shortening and angular deformity, causing adverse effects on the growth and development of adolescents. Therefore, preventing the formation of bone bridges has become the primary task for children with epiphyseal plate fractures. In our study, a novel near-infrared (NIR)-responsive bone repair scaffold (CGCB), namely black phosphorus (BP)-loaded in-situ gel based on curdlan (CUD), β-glycerophosphate (GP) and chitosan (CS), was developed. In vitro studies confirmed that the CGCB can promote the differentiation and migration of chondrocytes and has potential cartilage repair ability. A drilled model of epiphyseal plate injury further confirmed that CGCB can promote the repair of epiphyseal plate injury and NIR irradiation combined with CGCB significantly repaired the injury site by increasing expression of Sox9 and Aggrecan. The above findings indicate that the near-infrared (NIR) responsive bone repair scaffold (CGCB) can effectively inhibit bone bridge formation, prevent early closure of the epiphyseal plate, and provide new ideas for repairing epiphyseal plate defects in children.

Design and characterization of a ROS-responsive antibacterial composite hydrogel for advanced full-thickness wound healing

Full-thickness skin wounds remian a significant and pressing challenge. In this study, we introduce a novel composite hydrogel, CS + GA + Zn-HA. This hydrogel is formulated by incorporating 1 % (1 g/100 mL) of bioactive Zinc-substituted hydroxyapatite nanoparticles (Zn-HA) and 0.2 % (0.2 g/100 mL) of Gallic acid (GA) into chitosan (CS) hydrogels. A 56 % β-glycerophosphate sodium (β-GP) solution serves as the cross-linking agent, and the hydrogel is formed at 37 °C. This composite hydrogel can effectively modulate the wound microenvironment, facilitating comprehensive skin wound healing within two weeks. Physicochemical characterization demonstrates that this hydrogel is thermosensitive, with remarkable swelling behavior, mechanical strength, and drug-delivery performance. In vitro, the GA-incorporated hydrogels possess outstanding reactive oxygen species (ROS) scavenging and antioxidant properties, protecting L929 cells from hydrogen peroxide-induced oxidative damage. The combination of Zn-HA nanoparticles and GA not only augments the functionality of the hydrogel and decreases its degradation rate but also enables the controlled release of curcumin. Moreover, it provides a suitable immune microenvironment in terms of biological effects and significantly boosts the hydrogel's antibacterial ability, as demonstrated by an 89.2 % reduction in E. coli and a 53.6 % reduction in S. aureus. Benefiting from these properties, the CS + GA + Zn-HA composite hydrogel significantly promotes granulation tissue formation, re-epithelialization, angiogenesis, and wound closure in vivo. In conclusion, our research highlights the potential of the CS + GA + Zn-HA hydrogel as a multifunctional scaffold in tissue engineering, providing valuable insights for the design of future wound dressings for diverse wound types.

Structural, mechanical, and cytocompatibility characteristics of hybrid scaffolds from chitosan/decellularized testicular ECM

Tissue engineering has facilitated the development of novel therapeutic strategies for male reproductive disorders. Decellularized extracellular matrix (ECM) scaffolds provide a wide range of functional components that promote cellular behavior. This research aimed to develop reinforced scaffolds for testicular tissue engineering by combining testicular ECM (TE) derived pre-gel with chitosan (CS) solution at varying ratios (TE25/CS75, TE50/CS50, and TE75/CS25). To determine the optimum ratio of TE to CS solution, final scaffold properties were investigated including pore size, porosity, mechanical strength, swelling ratio, degradation rate followed by in-vitro biological evaluations. All groups revealed an interconnected porous structure with high porosity (from 76.6 % to 90.9 %) and adequate pore sizes (between 50 and 226 μm), while the pores of TE50/CS50 scaffold were distributed more uniformly. The mechanical properties of scaffolds were enhanced by combining CS with TE, whereas their swelling ratio decreased. It was observed that the scaffolds' degradation rate rose substantially as the ratio of TE to CS increased. The MTT assay revealed that none of the scaffolds exhibited cytotoxic properties. The results of this study demonstrated that all fabricated hybrid scaffolds, especially the TE50/CS50, have potential for testicular tissue engineering applications.

Facile Synthesis of Thermoresponsive Alternating Copolymers with Tunable Phase-Transition Temperatures

A series of novel amphiphilic alternating CPEG copolymers were synthesized through an amine-epoxy click reaction comprising aliphatic amine and polyethylene glycol diglycidyl ether (PEGDE). These polymers were characterized in detail via nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), Fourier-transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA) to confirm the successful synthesis. Due to their amphiphilic structure, these polymers display thermoresponsiveness, with tunable cloud points (Tcps) that are adjustable from 20.8 °C to 46.8 °C by altering the side-chain length of the aliphatic amine, varying the mixing ratios of copolymers, the solution's pH, and salt additions. This tunable thermoresponsive behavior positions CPEG copolymers as promising candidates for a range of functional material applications.

Physically crosslinked chitosan/αβ-glycerophosphate hydrogels enhanced by surface-modified cyclodextrin: An efficient strategy for controlled drug release

This study reports physically crosslinked chitosan/αβ-glycerophosphate (CS/GP) hydrogels containing surface-modified cyclodextrin for efficient controlled drug release. Highly water-soluble β-cyclodextrin-grafted L-serine (CD-g-Ser) compounds were synthesized, and employed as an effective carrier of berberine hydrochloride (Ber) for CS/GP hydrogels. Various characterizations, including gelation time determination, scanning electron microscopy, and viscosity measurement, indicated that the introduction of CD-g-Ser led to increased crosslinking degree, improved temperature sensitivity, and shortened sol-gel phase transition time of the hydrogel. Meanwhile, the sustained release ability for Ber was achieved due to the hydrophobic association between cyclodextrin and Ber. It was observed that within 4 h, the hydrogel containing CD-g-Ser released 40 % of Ber, while the CS/GP hydrogel without CD-g-Ser released 65 % of Ber. Furthermore, in vitro bacteriostasis experiments confirmed the drug-loaded hydrogel had an excellent antibacterial effect against E. coli and S. aureus (diameter of the inhibition zone up to (16.4 and 34.7) mm, respectively), low hemolysis rate (<2 %), and high cell viability (>90 %). The findings indicate that the physical crosslinked CS hydrogel can be used as a new drug delivery system, and its excellent antibacterial effect makes it a potential wound dressing candidate.

Temperature-Responsive Injectable Composite Hydrogels Based on Poly(N-Isopropylacrylamide), Chitosan, and Hemp-Derived Cellulose Nanocrystals

Injectable and temperature-responsive Poly(N-Isopropylacrylamide) (PNIPAAm)/Chitosan composite hydrogels reinforced with cellulose nanocrystals (CNCs) were successfully fabricated via photopolymerization. 0.1-3% (w/v) of cellulose nanocrystals were incorporated into the PNIPAAm/chitosan matrix to form thermo-responsive injectable composite hydrogels. FT-IR spectra confirmed the successful formation of these hydrogels, highlighting the characteristic peaks PNIPAAm, chitosan and CNCs. The inclusion of CNCs led to a reduced pore size as compared to the control hydrogels. The mechanical properties of the hydrogel were characterized under various temperature conditions. Rheology tests showed that storage modulus (G') increased significantly above 30 °C, indicating gel-like behavior. Thermogravimetric analysis showed thermal stability up to 300 °C. The volume phase transition temperatures (VPTT) of the hydrogels were found to be in the range of 34-38 °C, close to physiological body temperature. The equilibrium swelling ratio (ESR) of the CNC-containing hydrogels was higher than that of the control. In vitro studies with Human Dermal Fibroblast adult (HDFa) cells showed the hydrogels to be non-toxic, suggesting their potential for biomedical applications.

Thermosensitive Hydrogels as Targeted and Controlled Drug Delivery Systems: Potential Applications in Transplantation

Drug delivery in transplantation plays a vital role in promoting graft survival, preventing rejection, managing complications, and contributing to positive patient outcomes. Targeted and controlled drug delivery can minimize systemic effects. Thermosensitive hydrogels, due to their unique sol-gel transition properties triggered by thermo-stimuli, have attracted significant research interest as a potential drug delivery system in transplantation. This review describes the current status, characteristics, and recent applications of thermosensitive hydrogels for drug delivery. Studies aimed at improving allotransplantation outcomes using thermosensitive hydrogels are then elaborated on. Finally, the challenges and opportunities associated with their use are discussed. Understanding the progress of research will serve as a guide for future improvements in their application as a means of targeted and controlled drug delivery in translational therapeutic applications for transplantation.

Synthesis and Characterization of a Novel Chitosan-Based Nanoparticle-Hydrogel Composite System Promising for Skin Wound Drug Delivery

As a natural preservative, nisin is widely used in the food industry, while its application in biomedicine is limited due to its susceptibility to interference from external conditions. In this study, a nanoparticle-hydrogel composite system was designed to encapsulate and release nisin. Nisin nanoparticles were identified with a smooth, spherical visual morphology, particle size of 122.72 ± 4.88 nm, polydispersity coefficient of 0.473 ± 0.063, and zeta potential of 23.89 ± 0.37 mV. Based on the sample state and critical properties, three temperature-sensitive hydrogels based on chitosan were ultimately chosen with a rapid gelation time of 112 s, outstanding reticular structure, and optimal swelling ratio of 239.05 ± 7.15%. The composite system exhibited the same antibacterial properties as nisin, demonstrated by the composite system's inhibition zone diameter of 17.06 ± 0.83 mm, compared to 20.20 ± 0.58 mm for nisin, which was attributed to the prolonged release effect of the hydrogel at the appropriate temperature. The composite system also demonstrated good biocompatibility and safety, making it suitable for application as short-term wound dressings in biomedicine due to its low hemolysis rate of less than 2%. In summary, our nanoparticle-based hydrogel composite system offers a novel application form of nisin while ensuring its stability, thereby deepening and broadening the employment of nisin.

Vancomycin-Loaded Sol-Gel System for In Situ Coating of Artificial Bone to Prevent Surgical Site Infections

Surgical site infections (SSIs) related to implants have always been a major challenge for clinical doctors and patients. Clinically, doctors may directly apply antibiotics into the wound to prevent SSIs. However, this strategy is strongly associated with experience of doctors on the amount and the location of antibiotics. Herein, an in situ constructable sol-gel system is developed containing antibiotics during surgical process and validated the efficacy against SSIs in beagles. The system involves chitosan (CS), β-glycerophosphate (β-GP) and vancomycin (VAN), which can be adsorbed onto porous hydroxyapatite (HA) and form VAN-CS/β-GP@HA hydrogel in a short time. The VAN concentration from VAN-CS/β-GP@HA hydrogel is higher than minimum inhibitory concentration (MIC) against Staphylococcus aureus (S. aureus) at the 21st day in vitro. In an in vivo canine model for the prevention of SSIs in the femoral condyle, VAN-CS/β-GP@HA exhibits excellent biocompatibility, antimicrobial properties, and promotion of bone healing. In all, the CS/β-GP instant sol-gel system is able to in situ encapsulate antibiotics and adhere on artificial bone implants during the surgery, effectively preventing SSIs related to implants.

Prolonged joint cavity retention of tranexamic acid achieved by a solid-in-oil-in-gel system: A preliminary study

Tranexamic acid (TXA) is an anti-fibrinolysis agent widely used in postoperative blood loss management. As a highly water-soluble drug, TXA is suffering from rapid clearance from the action site, therefore, large amount of drug is required when administered either by intravenously or topically. In this study, a TXA preparation with prolonged action site residence was designed using the nano-micro strategy. TXA nanoparticles were dispersed in oil by emulsification followed by lyophilization to give a solid-in-oil suspension, which was used as the oil phase for the preparation of TXA-loaded solid-in-oil-in-water (TXA@S/O/W) system. The particle size of TXA in oil was 207.4 ± 13.50 nm, and the particle size of TXA@S/O/W was 40.5 μm. The emulsion-in-gel system (TXA@S/O/G) was prepared by dispersing TXA@S/O/W in water solution of PLGA-b-PEG-b-PLGA (PPP). And its gelling temperature was determined to be 26.6 ℃ by a rheometer. Sustained drug release was achieved by TXA@S/O/G with 72.85 ± 7.52 % of TXA released at 120 h. Formulation retention at the joint cavity was studied by live imaging, and the fluorescent signals dropped gradually during one week. Drug escape from the injection site via drainage and absorption was investigated by a self-made device and plasma TXA concentration determination, respectively. TXA@S/O/G showed the least drug drainage during test, while more than 70 % of drug was drained in TXA@S/O/W group and TXA solution group. Besides, low yet steady plasma TXA concentration (less than 400 ng/mL) was found after injecting TXA@S/O/G into rat knees at a dosage of 2.5 mg/kg, which was much lower than those of TXA dissolved in PPP gel or TXA solution. In conclusion, sustained drug release as well as prolonged action site retention were simultaneously achieved by the designed TXA@S/O/G system. More importantly, due to the steady plasma concentration, this strategy could be further applied to other highly water-soluble drugs with needs on sustained plasma exposure.

Decellularized porcine peripheral nerve based injectable hydrogels as a Schwann cell carrier for injured spinal cord regeneration

Objective.To develop a clinically relevant injectable hydrogel derived from decellularized porcine peripheral nerves and with mechanical properties comparable to native central nervous system (CNS) tissue to be used as a delivery vehicle for Schwann cell transplantation to treat spinal cord injury (SCI).Approach.Porcine peripheral nerves (sciatic and peroneal) were decellularized by chemical decellularization using a sodium deoxycholate and DNase (SDD) method previously developed by our group. The decellularized nerves were delipidated using dichloromethane and ethanol solvent and then digested using pepsin enzyme to form injectable hydrogel formulations. Genipin was used as a crosslinker to enhance mechanical properties. The injectability, mechanical properties, and gelation kinetics of the hydrogels were further analyzed using rheology. Schwann cells encapsulated within the injectable hydrogel formulations were passed through a 25-gauge needle and cell viability was assessed using live/dead staining. The ability of the hydrogel to maintain Schwann cell viability against an inflammatory milieu was assessedin vitrousing inflamed astrocytes co-cultured with Schwann cells.Mainresults. The SDD method effectively removes cells and retains extracellular matrix in decellularized tissues. Using rheological studies, we found that delipidation of decellularized porcine peripheral nerves using dichloromethane and ethanol solvent improves gelation kinetics and mechanical strength of hydrogels. The delipidated and decellularized hydrogels crosslinked using genipin mimicked the mechanical strength of CNS tissue. The hydrogels were found to have shear thinning properties desirable for injectable formulations and they also maintained higher Schwann cell viability during injection compared to saline controls. Usingin vitroco-culture experiments, we found that the genipin-crosslinked hydrogels also protected Schwann cells from astrocyte-mediated inflammation.Significance. Injectable hydrogels developed using delipidated and decellularized porcine peripheral nerves are a potential clinically relevant solution to deliver Schwann cells, and possibly other therapeutic cells, at the SCI site by maintaining higher cellular viability and increasing therapeutic efficacy for SCI treatment.

Chitosan alchemy: transforming tissue engineering and wound healing

Chitosan, a biopolymer acquired from chitin, has emerged as a versatile and favorable material in the domain of tissue engineering and wound healing. Its biocompatibility, biodegradability, and antimicrobial characteristics make it a suitable candidate for these applications. In tissue engineering, chitosan-based formulations have garnered substantial attention as they have the ability to mimic the extracellular matrix, furnishing an optimal microenvironment for cell adhesion, proliferation, and differentiation. In the realm of wound healing, chitosan-based dressings have revealed exceptional characteristics. They maintain a moist wound environment, expedite wound closure, and prevent infections. These formulations provide controlled release mechanisms, assuring sustained delivery of bioactive molecules to the wound area. Chitosan's immunomodulatory properties have also been investigated to govern the inflammatory reaction during wound healing, fostering a balanced healing procedure. In summary, recent progress in chitosan-based formulations portrays a substantial stride in tissue engineering and wound healing. These innovative approaches hold great promise for enhancing patient outcomes, diminishing healing times, and minimizing complications in clinical settings. Continued research and development in this field are anticipated to lead to even more sophisticated chitosan-based formulations for tissue repair and wound management. The integration of chitosan with emergent technologies emphasizes its potential as a cornerstone in the future of regenerative medicine and wound care. Initially, this review provides an outline of sources and unique properties of chitosan, followed by recent signs of progress in chitosan-based formulations for tissue engineering and wound healing, underscoring their potential and innovative strategies.

Exosomes encapsulated in hydrogels for effective central nervous system drug delivery

The targeted delivery of pharmacologically active molecules, metabolites, and growth factors to the brain parenchyma has become one of the major challenges following the onset of neurodegeneration and pathological conditions. The therapeutic effect of active biomolecules is significantly impaired after systemic administration in the central nervous system (CNS) because of the blood-brain barrier (BBB). Therefore, the development of novel therapeutic approaches capable of overcoming these limitations is under discussion. Exosomes (Exo) are nano-sized vesicles of endosomal origin that have a high distribution rate in biofluids. Recent advances have introduced Exo as naturally suitable bio-shuttles for the delivery of neurotrophic factors to the brain parenchyma. In recent years, many researchers have attempted to regulate the delivery of Exo to target sites while reducing their removal from circulation. The encapsulation of Exo in natural and synthetic hydrogels offers a valuable strategy to address the limitations of Exo, maintaining their integrity and controlling their release at a desired site. Herein, we highlight the current and novel approaches related to the application of hydrogels for the encapsulation of Exo in the field of CNS tissue engineering.

Recent Applications of Chitosan and Its Derivatives in Antibacterial, Anticancer, Wound Healing, and Tissue Engineering Fields

Chitosan, a versatile biopolymer derived from chitin, has garnered significant attention in various biomedical applications due to its unique properties, such as biocompatibility, biodegradability, and mucoadhesiveness. This review provides an overview of the diverse applications of chitosan and its derivatives in the antibacterial, anticancer, wound healing, and tissue engineering fields. In antibacterial applications, chitosan exhibits potent antimicrobial properties by disrupting microbial membranes and DNA, making it a promising natural preservative and agent against bacterial infections. Its role in cancer therapy involves the development of chitosan-based nanocarriers for targeted drug delivery, enhancing therapeutic efficacy while minimising side effects. Chitosan also plays a crucial role in wound healing by promoting cell proliferation, angiogenesis, and regulating inflammatory responses. Additionally, chitosan serves as a multifunctional scaffold in tissue engineering, facilitating the regeneration of diverse tissues such as cartilage, bone, and neural tissue by promoting cell adhesion and proliferation. The extensive range of applications for chitosan in pharmaceutical and biomedical sciences is not only highlighted by the comprehensive scope of this review, but it also establishes it as a fundamental component for forthcoming research in biomedicine.

Injectable Hydrogels for Nervous Tissue Repair-A Brief Review

The repair of nervous tissue is a critical research field in tissue engineering because of the degenerative process in the injured nervous system. In this review, we summarize the progress of injectable hydrogels using in vitro and in vivo studies for the regeneration and repair of nervous tissue. Traditional treatments have not been favorable for patients, as they are invasive and inefficient; therefore, injectable hydrogels are promising for the treatment of damaged tissue. This review will contribute to a better understanding of injectable hydrogels as potential scaffolds and drug delivery system for neural tissue engineering applications.

Advances in chitosan and chitosan derivatives for biomedical applications in tissue engineering: An updated review

In recent years, chitosan (CS) has received much attention as a functional biopolymer for various applications, especially in the biomedical field. It is a natural polysaccharide created by the chemical deacetylation of chitin (CT) that is nontoxic, biocompatible, and biodegradable. This natural polymer is difficult to process; however, chemical modification of the CS backbone allows improved use of functional derivatives. CS and its derivatives are used to prepare hydrogels, membranes, scaffolds, fibers, foams, and sponges, primarily for regenerative medicine. Tissue engineering (TE), currently one of the fastest-growing fields in the life sciences, primarily aims to restore or replace lost or damaged organs and tissues using supports that, combined with cells and biomolecules, generate new tissue. In this sense, the growing interest in the application of biomaterials based on CS and some of its derivatives is justifiable. This review aims to summarize the most important recent advances in developing biomaterials based on CS and its derivatives and to study their synthesis, characterization, and applications in the biomedical field, especially in the TE area.

Implantation of In Situ Gelling Systems for the Delivery of Chemotherapeutic Agents

Implantation is a modern method of administering chemotherapeutic agents, with a highly targeted effect and better patient tolerance due to the low frequency of administration. Implants are capable of controlled release, which makes them a viable alternative to infusional chemotherapy, allowing patients to enjoy a better quality of life without the need for prolonged hospitalization. Compared to subcutaneous implantation, intratumoral implantation has a number of significant advantages in terms of targeting and side effects, but this area of chemotherapy is still poorly understood in terms of clinical trials. At the same time, there are more known developments of drugs in the form of implants and injections for intratumoral administration. The disadvantages of classical intratumoral implants are the need for surgical intervention to install the system and the increased risk of tumor rupture noted by some specialists. The new generation of implants are in situ implants-systems formed in the tumor due to a phase transition (sol-gel transition) under the influence of various stimuli. Among this systems some are highly selective for a certain type of malignant neoplasm. Such systems are injected and have all the advantages of intratumoral injections, but due to the phase transition occurring in situ, they form depot forms that allow the long-term release of chemotherapeutic agents.

Use of Chitosan as a Precursor for Multiple Applications in Medicinal Chemistry: Recent Significant Contributions

Chitosan (CS) is a polymer made up of mainly deacetylated β-1,4 D-glucosamine units, which is part of a large group of D-glucosamine oligomers known as chitooligosaccharides, which can be obtained from chitin, most abundant natural polymer after cellulose and central component of the shrimp exoskeleton. It is known that it can be used for the development of materials, among which its use stands out in wastewater treatment (removal of metal ions, dyes, and as a membrane in purification processes), food industry (anti-cholesterol and fat, packaging material, preservative, and food additive), agriculture (seed and fertilizer coating, controlled release agrochemicals), pulp and paper industry (surface treatment, adhesive paper), cosmetics (body creams, lotions, etc.), in the engineering of tissues, wound healing, as excipients for drug administration, gels, membranes, nanofibers, beads, microparticles, nanoparticles, scaffolds, sponges, and diverse biological ones, specifically antibacterial and antifungal activities. This article reviews the main contributions published in the last ten years regarding the use and application of CS in medical chemistry. The applications exposed here involve regenerative medicine in the design of bioprocesses and tissue engineering, Pharmaceutical sciences to obtain biomaterials, polymers, biomedicine, and the use of nanomaterials and nanotechnology, toxicology, and Clinical Pharmaceuticals, emphasizing the perspectives and the direction that can take research in this area.

Chitosan scaffolds: Expanding horizons in biomedical applications

Chitosan, a natural polysaccharide from chitin, shows promise as a biomaterial for various biomedical applications due to its biocompatibility, biodegradability, antibacterial activity, and ease of modification. This review overviews "chitosan scaffolds" use in diverse biomedical applications. It emphasizes chitosan's structural and biological properties and explores fabrication methods like gelation, electrospinning, and 3D printing, which influence scaffold architecture and mechanical properties. The review focuses on chitosan scaffolds in tissue engineering and regenerative medicine, highlighting their role in bone, cartilage, skin, nerve, and vascular tissue regeneration, supporting cell adhesion, proliferation, and differentiation. Investigations into incorporating bioactive compounds, growth factors, and nanoparticles for improved therapeutic effects are discussed. The review also examines chitosan scaffolds in drug delivery systems, leveraging their prolonged release capabilities and ability to encapsulate medicines for targeted and controlled drug delivery. Moreover, it explores chitosan's antibacterial activity and potential for wound healing and infection management in biomedical contexts. Lastly, the review discusses challenges and future objectives, emphasizing the need for improved scaffold design, mechanical qualities, and understanding of interactions with host tissues. In summary, chitosan scaffolds hold significant potential in various biological applications, and this review underscores their promising role in advancing biomedical science.

Physico‐chemical properties and in‐vitro biocompatibility of thermo‐sensitive hydrogel developed with enhanced antimicrobial activity for soft tissue engineering

Smart materials such as thermo‐sensitive in situ forming hydrogels can be effective agents in drug delivery and tissue regeneration with minimal invasion. Injection method would avoid complex surgical procedures facilitating rapid recovery process. In this research, we report the fabrication of an easy, reproducible thermo‐sensitive hydrogel constituting of chitosan (CHI), glycerol phosphate (GP) with variable quantity of ‐poly‐l‐lysine (PS). Fourier‐transform infrared spectra exhibited hydrogel formation where interactions between CHI and GP were seen. The gelation kinetics presented gelation time of 8 min at physiological temperature. The results indicated an increase in degradation rate with the passage of time. Contact angles measurements were employed to observe hydrophilic characteristics which were shown to be favorable. Mechanical strength was determined to be in the range of ~0.1–0.6 MPa for all the hydrogels. Due to intrinsic antibacterial features of CHI and PS, the hydrogels showed potent antibacterial activity against Escherichia coli, Staphylococcus aureus, and Methicillin‐resistant S. aureus (MR‐SA). Interestingly, PS's addition in the hydrogel resulted in potent antibacterial activity against clinically relevant MR‐SA. The hydrogels can hence be delivered to a specific target for localized treatments where the potential of inhibiting multidrug resistant strain is clinically relevant. Biocompatibility of the hydrogels was seen by an overall increase in cell viability of mouse fibroblast cells and scratch assay revealed favorable migration potential. Proangiogenic Vascular endothelial growth factor (VEGF)'s expression showed a gradual increase with increasing concentration of PS, whereas one composition demonstrated a slight increase in the expression of cytosolic prostaglandin E synthase (cPGES) as determined by RT‐PCR. Overall, an increase in PS content of the hydrogels resulted in simultaneously enhanced antibacterial efficiency and marked increase in fibroblast cell viability, hence, reiterating their potential as potent antibacterial agents that can be explored as wound healing agents. In conclusion, novel antibacterial thermo‐sensitive hydrogels were synthesized with a potential of regulating proangiogenic and tissue regeneration factors that highlight their role as wound healing agents.

Long-termin vitroculture of 3D brain tissue model based on chitosan thermogel

Methods for studying brain function and disease heavily rely onin vivoanimal models,ex-vivotissue slices, and 2D cell culture platforms. These methods all have limitations that significantly impact the clinical translatability of results. Consequently, models able to better recapitulate some aspects ofin vivohuman brain are needed as additional preclinical tools. In this context, 3D hydrogel-basedin vitromodels of the brain are considered promising tools. To create a 3D brain-on-a-chip model, a hydrogel capable of sustaining neuronal maturation over extended culture periods is required. Among biopolymeric hydrogels, chitosan-β-glycerophosphate (CHITO-β-GP) thermogels have demonstrated their versatility and applicability in the biomedical field over the years. In this study, we investigated the ability of this thermogel to encapsulate neuronal cells and support the functional maturation of a 3D neuronal network in long-term cultures. To the best of our knowledge, we demonstrated for the first time that CHITO-β-GP thermogel possesses optimal characteristics for promoting neuronal growth and the development of an electrophysiologically functional neuronal network derived from both primary rat neurons and neurons differentiated from human induced pluripotent stem cells (h-iPSCs) co-cultured with astrocytes. Specifically, two different formulations were firstly characterized by rheological, mechanical and injectability tests. Primary nervous cells and neurons differentiated from h-iPSCs were embedded into the two thermogel formulations. The 3D cultures were then deeply characterized by immunocytochemistry, confocal microscopy, and electrophysiological recordings, employing both 2D and 3D micro-electrode arrays. The thermogels supported the long-term culture of neuronal networks for up to 100 d. In conclusion, CHITO-β-GP thermogels exhibit excellent mechanical properties, stability over time under culture conditions, and bioactivity toward nervous cells. Therefore, they are excellent candidates as artificial extracellular matrices in brain-on-a-chip models, with applications in neurodegenerative disease modeling, drug screening, and neurotoxicity evaluation.

Hydrogel Tissue Bioengineered Scaffolds in Bone Repair: A Review

Large bone defects due to trauma, infections, and tumors are difficult to heal spontaneously by the body's repair mechanisms and have become a major hindrance to people's daily lives and economic development. However, autologous and allogeneic bone grafts, with their lack of donors, more invasive surgery, immune rejection, and potential viral transmission, hinder the development of bone repair. Hydrogel tissue bioengineered scaffolds have gained widespread attention in the field of bone repair due to their good biocompatibility and three-dimensional network structure that facilitates cell adhesion and proliferation. In addition, loading natural products with nanoparticles and incorporating them into hydrogel tissue bioengineered scaffolds is one of the most effective strategies to promote bone repair due to the good bioactivity and limitations of natural products. Therefore, this paper presents a brief review of the application of hydrogels with different gel-forming properties, hydrogels with different matrices, and nanoparticle-loaded natural products loaded and incorporated into hydrogels for bone defect repair in recent years.

Design and fabrication of dysprosium impregnated polyvinyl alcohol hydrogels. Physiochemical, mechanical, bioimaging and in vitro evaluation

Tissue engineering has gained prominence during the past decade since it offers a key solution to defects associated with the tissue regeneration. The limited healing potential of the cartilage tissue damage has significant clinical implications. Herein, dysprosium (Dy3+) impregnated polyvinyl alcohol (PVA) hydrogels have been developed to enhance the therapeutic efficacy, enabling simultaneous diagnostic imaging and antibacterial drug delivery for potential applications in articular cartilage. Based on the favorable imaging features, Dy3+ impregnated PVA hydrogels with enhanced stability were formed through successive steps of repeated cycles of freezing at - 30 °C for 21 h, thawing at 25 °C for 4 h and lyophilization. The tensile and compression tests of the hydrogels respectively determined a maximum of 3.88 and 1.58 MPa, which reflected better compatibility towards cartilage. The hydrogels fetched a sustained drug release for a period of 12 h with an associated swelling ratio of 80%. The potential of the resultant hydrogels in image diagnosis has been deliberated through their blue and yellow emissions in the visible region. Further, the computed tomography (CT) and magnetic resonance imaging characteristics of the hydrogels respectively accomplished a maximum of 343 Hounsfiled units (HU) and relaxivity of 7.25 mM-1s-1. The cytocompatibility of the hydrogels is also determined through in vitro tests performed in Murine pro B cell line (BA/F3) and human Megakaryocyte cell line (Mo7e) cell lines.

Mitigating Metal-Organic Framework (MOF) Toxicity for Biomedical Applications

Metal-organic frameworks (MOFs) are a novel class of crystalline porous materials, consisting of metal ions and organic linkers. These hybrid materials possess exceptional porosity and specific surface area, which have recently garnered significant interest due to their potential applications in gas separation and storage, energy storage, biomedical imaging, and drug delivery. As MOFs are being explored for biomedical applications, it is essential to comprehensively assess their toxicity. Although nearly ninety thousand MOFs have been investigated, evaluating and optimizing their physico-chemical properties in relevant biological systems remain critical for their clinical translation. In this review article, we first provide a brief classification of MOFs based on their chemical structures. We then conduct a comprehensive evaluation of in vitro and in vivo studies that assess the biocompatibility of MOFs. Additionally, we discuss various approaches to mitigate the critical factors associated with MOF toxicity. To this end, the effects of chemistry, particle size, morphology, and particle aggregation are examined. To better understand MOFs' potential toxicity to living organisms, we also delve into the toxicity mechanisms of nanoparticles (NPs). Furthermore, we introduce and evaluate strategies such as surface modification to reduce the inherent toxicity of MOFs. Finally, we discuss current challenges, the path to clinical trials, and new research directions.

Chitosan Hydrogels for Water Purification Applications

Chitosan-based hydrogels have gained significant attention for their potential applications in water treatment and purification due to their remarkable properties such as bioavailability, biocompatibility, biodegradability, environmental friendliness, high pollutants adsorption capacity, and water adsorption capacity. This article comprehensively reviews recent advances in chitosan-based hydrogel materials for water purification applications. The synthesis methods, structural properties, and water purification performance of chitosan-based hydrogels are critically analyzed. The incorporation of various nanomaterials into chitosan-based hydrogels, such as nanoparticles, graphene, and metal-organic frameworks, has been explored to enhance their performance. The mechanisms of water purification, including adsorption, filtration, and antimicrobial activity, are also discussed in detail. The potential of chitosan-based hydrogels for the removal of pollutants, such as heavy metals, organic contaminants, and microorganisms, from water sources is highlighted. Moreover, the challenges and future perspectives of chitosan-based hydrogels in water treatment and water purification applications are also illustrated. Overall, this article provides valuable insights into the current state of the art regarding chitosan-based hydrogels for water purification applications and highlights their potential for addressing global water pollution challenges.

Glucose-Responsive Microgel Comprising Conventional Insulin and Curcumin-Laden Nanoparticles: a Potential Combination for Diabetes Management

Successful management of type 2 diabetes mellitus (T2DM), a complex and chronic disease, requires a combination of anti-hyperglycemic and anti-inflammatory agents. Here, we have conceptualized and tested an integrated "closed-loop mimic" in the form of a glucose-responsive microgel (GRM) based on chitosan, comprising conventional insulin (INS) and curcumin-laden nanoparticles (nCUR) as a potential strategy for effective management of the disease. In addition to mimicking the normal, on-demand INS secretion, such delivery systems display an uninterrupted release of nCUR to combat the inflammation, oxidative stress, lipid metabolic abnormality, and endothelial dysfunction components of T2DM. Additives such as gum arabic (GA) led to a fivefold increased INS loading capacity compared to GRM without GA. The GRMs showed excellent in vitro on-demand INS release, while a constant nCUR release is observed irrespective of glucose concentrations. Thus, this study demonstrates a promising drug delivery technology that can simultaneously, and at physiological/pathophysiological relevance, deliver two drugs of distinct physicochemical attributes in the same formulation.

Injectable hydrogels in central nervous system: Unique and novel platforms for promoting extracellular matrix remodeling and tissue engineering

Repairing central nervous system (CNS) is difficult due to the inability of neurons to recover after damage. A clinically acceptable treatment to promote CNS functional recovery and regeneration is currently unavailable. According to recent studies, injectable hydrogels as biodegradable scaffolds for CNS tissue engineering and regeneration have exceptionally desirable attributes. Hydrogel has a biomimetic structure similar to extracellular matrix, hence has been considered a 3D scaffold for CNS regeneration. An interesting new type of hydrogel, injectable hydrogels, can be injected into target areas with little invasiveness and imitate several aspects of CNS. Injectable hydrogels are being researched as therapeutic agents because they may imitate numerous properties of CNS tissues and hence reduce subsequent injury and regenerate neural tissue. Because of their less adverse effects and cost, easier use and implantation with less pain, and faster regeneration capacity, injectable hydrogels, are more desirable than non-injectable hydrogels. This article discusses the pathophysiology of CNS and the use of several kinds of injectable hydrogels for brain and spinal cord tissue engineering, paying particular emphasis to recent experimental studies.