Injectable hydrogels delivering therapeutic agents for disease treatment and tissue engineering

Tailoring hyaluronic acid hydrogels: Impact of cross-linker length and density on skin rejuvenation as injectable dermal fillers and their potential effects on the MAPK signaling pathway suppression

Hyaluronic acid (HA) hydrogels, obtained through cross-linking, provide a stable 3D environment that is important for controlled delivery and tissue engineering applications. Cross-linking density has a significant impact on the physicochemical properties of hydrogels, including their shape stability, mechanical stiffness and macromolecular diffusivity. However, often cross-linking chemistries require photoinitiator and catalyst that may be toxic and cause unwanted tissue response. Here, we prepared a series of HA hydrogel with varying cross-linker length and cross-linking density, which can be obtained by altering the feed ratio of three different cross-linkers from small molecules to macromolecules (e.g., 1,4-butanediol diglycidyl ether (BDDE), ferulic acid (FA), pluronic (PLU)), to ameliorate skin wrinkles in mice models. HA cross-linked with FA and PLU exhibited enzyme and temperature-dependent sol-to-gel phase transition, respectively, and the gels possess good injectability. In vitro test confirmed that HA hydrogels co-cultured with RAW 264.7 and HDF cells showed good biocompatibility. In particular, HA cross-linked with PLU stimulated the growth of HDF cells and HaCaT cells. HA cross-linked with PLU suppressed the expression levels of proteins involved in collagen degradation including mitogen-activated protein kinases (ERK, JNK, p38) and matrix metalloproteases (MMP-1, MMP-3, and MMP-9) resulting in increased deposition of Collagen I. The free-flowing sols of HA hydrogel precursors are subcutaneously injected into the back of BALB/c mice and form stable gels at the dermis layer and found to be non-toxic. More importantly, HA hydrogel cross-linked with PLU showed an enhanced anti-wrinkling effect in the wrinkled mice model. Thus, properties of HA hydrogels such as injectability, biocompatibility, and good anti-wrinkling effect altered through varying cross-linking density must be considered in the context of soft tissue engineering applications.

In-situ hyaluronic acid-tyramine hydrogels prolong the release of extracellular vesicles and enhance stability

Hydrogels can provide a hydrated environment to encapsulate extracellular vesicles (EVs) while offering promising solutions to some of the challenges that limit their therapeutic potential, e.g. rapid clearance and propensity for enzymatic degradation and aggregation. This study explores the use of a hyaluronic acid-tyramine (HA-TA) hydrogel to prolong the delivery and enhance the stability of EVs. EVs were obtained from lentiviral-transduced HEK293T cells expressing luciferase and eGFP to enable easy quantification. Two encapsulation strategies were evaluated: (1) pre-loading, where EVs were mixed with HA-TA (2.58 % degree of substitution) precursor solution and subsequently crosslinked with 2 U/mL horseradish peroxidase (HRP) and 0.05 mM H2O2; and (2) post-loading, where EVs were soaked into pre-formed dehydrated hydrogels. Both methods improved EV stability over 7 days at 37 °C compared to free EVs. The pre-loading approach was ultimately selected due to its ability to give rapid in situ gelation within one minute. Controlled in vitro release of EVs from the pre-loaded hydrogels was observed to extend beyond 7 days, as determined by CD9 ELISA. The released EVs maintained their bioactivity, as evidenced by effective internalisation into ARPE-19 and H9c2 cell lines, with performance comparable to fresh EVs. The EV release profile could be varied by modifying the hydrogel concentration. These findings underscore the potential of HA-TA hydrogels for localised, sustained, EV delivery with preserved functionality.

Local antibiotic delivery: Recent basic and translational science insights in orthopedics

BACKGROUND

Infections remain a significant challenge in orthopedic settings despite advancements in preventive measures. Antibiotics are the primary defense against infections, but optimal delivery methods to the infection site are still being investigated. This review aims to examine existing approaches for local drug delivery from a basic science perspective.

RECENT FINDINGS

Achieving adequate antibiotic concentration at the infection site is challenging due to compromised vasculature in ischemic conditions. Local administration methods, including antibiotic-loaded carriers such as impregnated bone grafts and various bone substitutes, are being explored as alternatives to systemic antibiotic use.

SUMMARY

Various materials, including polymethyl methacrylate (PMMA), hydroxyapatite, calcium phosphate/sulfate, bone glass, and hydrogel, are being investigated for local antibiotic delivery. Some of these materials possess inherent antibacterial properties due to their chemical interactions. The selection of appropriate antibiotics, their dosage, release kinetics from the carrier material, physical behavior of the material/graft, and biocompatibility are key areas for further investigation in basic science research.

Injectable hyaluronic acid-based hydrogel niches to create localized and time-controlled therapy delivery

The use of hydrogel-based niches for therapy delivery enables the concentration of active components and cells in a targeted area. This approach enhances efficacy while minimizing systemic side effects by spatially controlling the release of the therapy. Precise tuning of the matrix's chemical properties and control of both material degradation and release profile of biologically active components are required to reduce the optimal dose and extend its therapeutic effect. Here we aimed to develop an injectable hydrogel that can fulfill all these requirements. We designed a system based on hyaluronic acid, crosslinked via click-reaction with multi-arm polyethyleneglycol and functionalized with RGD peptides. Additionally, we incorporated thiol-modified heparin into the formulation, which provides specific binding sites for cytokines. Our results indicate that heparin incorporation can delay cytokine release, while the release of nanocarriers can be regulated by adjusting the crosslinking degree. This design modulates pore size and degradation time, while preserving the injectability of the niche. In conclusion, this system offers a versatile and efficient delivery platform suitable for therapeutic applications in a wide range of diseases.

Physical stimuli-responsive DNA hydrogels: design, fabrication strategies, and biomedical applications

Physical stimuli-responsive DNA hydrogels hold immense potential for tissue engineering due to their inherent biocompatibility, tunable properties, and capacity to replicate the mechanical environment of natural tissue, making physical stimuli-responsive DNA hydrogels a promising candidate for tissue engineering. These hydrogels can be tailored to respond to specific physical triggers such as temperature, light, magnetic fields, ultrasound, mechanical force, and electrical stimuli, allowing precise control over their behavior. By mimicking the extracellular matrix (ECM), DNA hydrogels provide structural support, biomechanical cues, and cell signaling essential for tissue regeneration. This article explores various physical stimuli and their incorporation into DNA hydrogels, including DNA self-assembly and hybrid DNA hydrogel methods. The aim is to demonstrate how DNA hydrogels, in conjunction with other biomolecules and the ECM environment, generate dynamic scaffolds that respond to physical stimuli to facilitate tissue regeneration. We investigate the most recent developments in cancer therapies, including injectable DNA hydrogel for bone regeneration, personalized scaffolds, and dynamic culture models for drug discovery. The study concludes by delineating the remaining obstacles and potential future orientations in the optimization of DNA hydrogel design for the regeneration and reconstruction of tissue. It also addresses strategies for surmounting current challenges and incorporating more sophisticated technologies, thereby facilitating the clinical translation of these innovative hydrogels.

Revolutionizing Drug Delivery: The Impact of Advanced Materials Science and Technology on Precision Medicine

Recent progress in material science has led to the development of new drug delivery systems that go beyond the conventional approaches and offer greater accuracy and convenience in the application of therapeutic agents. This review discusses the evolutionary role of nanocarriers, hydrogels, and bioresponsive polymers that offer enhanced drug release, target accuracy, and bioavailability. Oncology, chronic disease management, and vaccine delivery are some of the applications explored in this paper to show how these materials improve the therapeutic results, counteract multidrug resistance, and allow for sustained and localized treatments. The review also discusses the translational barriers of bringing advanced materials into the clinical setting, which include issues of biocompatibility, scalability, and regulatory approval. Methods to overcome these challenges include surface modifications to reduce immunogenicity, scalable production methods such as microfluidics, and the harmonization of regulatory systems. In addition, the convergence of artificial intelligence (AI) and machine learning (ML) is opening new frontiers in material science and personalized medicine. These technologies allow for predictive modeling and real-time adjustments to optimize drug delivery to the needs of individual patients. The use of advanced materials can also be applied to rare and underserved diseases; thus, new strategies in gene therapy, orphan drugs development, and global vaccine distribution may offer new hopes for millions of patients.

Development of an injectable salicylic acid-choline eutectic hydrogel for enhanced treatment of periodontitis

Periodontitis, a chronic inflammatory disease triggered by dental plaque, often presents challenges in management, particularly in severe cases where mechanical debridement alone may be insufficient. As a result, adjunctive therapies, particularly localized drug delivery systems with both antimicrobial and anti-inflammatory properties, are essential to enhance the efficacy of periodontitis management. In this study, we developed a multifunctional hydrogel by incorporating a salicylic acid-choline deep eutectic solvent (DES) into a chitosan/β-glycerol phosphate sodium (CS/GP) hydrogel matrix for the treatment of periodontitis. The DES-CS/GP hydrogel demonstrated favorable physicochemical properties, including gelation and injectability, making it highly suitable for application in the oral cavity. The hydrogel effectively inhibited the growth of key periodontal pathogens, Porphyromonas gingivalis and Fusobacterium nucleatum, and significantly downregulated the expression of pro-inflammatory cytokines TNF-α and IL-1β in vitro. Cytocompatibility assessments showed over 80% cell viability in human gingival fibroblasts, human gingival epithelial cells, and human oral keratinocytes over 5 days treated with DES-CS/GP, with fluorescence microscopy confirming robust cytoskeletal integrity. Furthermore, the hydrogel enhanced permeability through gingival tissues in vitro. In a rat model of periodontitis, the hydrogel significantly mitigated bone loss, reduced bacterial loads of P. g, and suppressed TNF-α and IL-1β expression in gingival tissues. These findings underscore the hydrogel's potential as a safe and effective adjunctive therapy for periodontitis, offering a combination of antimicrobial, anti-inflammatory, and tissue-permeating properties with high biosafety and ease of application.

In situ forming and self-crosslinkable protein hydrogels for localized cancer therapy and topical wound healing

Proteins, inherently biocompatible and biodegradable, face a challenge in forming stable hydrogels without external chemical crosslinkers. Here, we construct a ring-shaped trimeric SpyTag-fused Proliferating Cell Nuclear Antigen Protein (ST-PCNA) as a core protein building block, and a dumbbell-shaped tandem dimeric SpyCatcher (SC-SC) as a bridging component. Self-crosslinked PCNA/SC-SC Protein (2SP) hydrogels are successfully formed by simply mixing the solutions of ST-PCNA and SC-SC, without chemical crosslinkers. During their formation by mixing, various cargo molecules, including anti-cancer drugs, photosensitizers, and functional proteins, are efficiently incorporated, producing cargo@2SP hydrogels. Most of the entrapped cargo molecules gradually release as the hydrogels erode. Anti-cancer drug- or photosensitizer-incorporated 2SP hydrogels are successfully formed through localized injection beneath the 4 T1 tumor in mice. The localized gradual release of drugs in physiological microenvironment substantially suppresses tumor growth, and highly localized photosensitizers retained in the 2SP hydrogels raises the local temperature above 45 °C upon laser irradiation, resulting in a significant suppression of tumor growth. Additionally, the topical administration of growth factor proteins-incorporated 2SP hydrogels to the incision wound area effectively regenerates the skin, with rapid reconstruction of extracellular matrix. The injectable and self-crosslinkable 2SP hydrogels developed here offer promise as novel biocompatible scaffolds for local therapy.

Hydrogels of dialdehyde starch and gelatin cross-linked with potential application as tissue adhesives

Invasive surgical methods are the current standard for hemostasis and wound closure. In recent years, injectable hydrogels prepared from natural biomacromolecules have shown promise as tissue adhesives to overcome their shortcomings due to their high hydrophilicity and biocompatibility, but the inherent properties of unmodified biomolecules remain a major challenge in their application. In this paper, a hydrogel (DS/Gel-CDH) with self-healing, injectable and adhesive functions was constructed by Schiff base crosslinking between carbonyl hydrazide modified gelatin (Gel-CDH) and dialdehyde starch (DS). The adhesion strength of the hydrogel (34.92 kPa) is much better than that of commercially available protein adhesives (17.44 kPa). In addition, Cytotoxicity and hemolysis tests showed that the hydrogel was non-cytotoxic (cell survival rate was 96.9 %) and could be used as biomaterial in contact with blood. The rats skin incision wound model further confirmed that this hydrogel can adhere to the wound and promote healing. H&E and MT staining showed no signs of toxicity in the tissue around the wound, and IL-6 and IL-1β staining showed no inflammatory reaction. It is proved that the hydrogel has good biocompatibility and degradability in vivo. The results indicate that the multifunctional the DS/Gel-CDH hydrogels are a promising and effective tissue adhesive material.

Structured Polymers Enable the Sustained Delivery of Glucocorticoids within the Intra-Articular Space

Intra-articular glucocorticoid injections are effective in controlling inflammation and pain in arthritides but restricted by short duration of action and risk of joint degeneration. Controlled drug release using biocompatible hydrogels offers a unique solution, but limitations of in situ gelation restrict their application. Gellan sheared hydrogels (GSHs) retain the advantages of hydrogels, however their unique microstructures lend themselves to intra-articular application - capable of shear thinning under force but restructuring at rest to enhance residence. This study examined GSHs for extended intra-articular glucocorticoid delivery of prednisolone (10 mg mL-1); demonstrating links between material mechanics, steroid release, and preclinical assessment of efficacy in synoviocyte culture and transgenic(TNF)197Gkl (TNFtg) murine model of arthritis. GSHs demonstrated sustained release, with typical Fickian profiles over 18 days. Moreover, systems showed good stability under extended culture, with inherent cell-compatibility and suppression of inflammatory synoviocyte activation. In TNFtg animals, GSHs suppressed synovitis (70.08%, p < 0.05), pannus formation (45.01%, p < 0.05), and increased articular cartilage (82.23%, p < 0.05) relative to vehicle controls. The extended profile of steroid release from injectable GSH formulations holds promise in the treatment and management of inflammatory arthritides such as rheumatoid and osteoarthritis, representing a step-change in intra-articular drug delivery to suppress long-term joint inflammation.

Progress in injectable hydrogels for hard tissue regeneration in the last decade

Bone disorders have increased with increasing the human lifespan, and despite the tissue's ability to self-regeneration, in many congenital problems and hard fractures, bone grafting such as autograft, allograft, and biomaterials implantation through surgery is traditionally used. Because of the adverse effects of these methods, the emergence of injectable hydrogels without the need for surgery and causing more pain for the patient is stunning to develop a new pattern for hard tissue engineering. These materials are formed with various natural and synthetic polymers with a crosslinked network through various chemical methods such as click chemistry, Michael enhancement, Schiff's base and enzymatic reaction and physical interactions with high water absorption which can mimic the environment of cells. The purpose of this research is to review the capabilities of this class of materials in hard tissue regeneration in the last decade through adaptable physical and chemical properties, the ability to fill defect sites with an irregular shape, and the ability to grow hormones or release drugs, in response to external stimuli.

Zn(II) Coordination Polymer: Luminescence Sensing for Fe3+ Ion and Used as Metal Gel Particles Against Lung Cancer

Presented here is a new Zn(II) coordination polymer, namely [Zn2(L)2(bpe)]n (1, H2L = 4-({2-[(4-carboxyphenoxy)methyl]phenyl}methoxy)benzoic acid, bpe = 1,2-bis(4-pyridinyl)ethane), which has been hydrothermally synthesized via the mixed-ligand strategy. Moreover, compound 1 emits intense luminescence at room temperature, and can be used as a luminescent sensor for the detection of Fe3+ in water solution with high selectivity and sensitivity. As representatives of natural polysaccharides, hyaluronic acid (HA) and carboxymethyl chitosan (CMCS) have good biocompatibility. A new type of HA/CMCS gel particles loaded with Paclitaxel drug metal-organic framework was prepared by chemical synthesis method and its micromorphology was studied. Finally, biological experiments were conducted to evaluate the new system's effect on the activity of human lung cancer cells.

Polymeric Drug Delivery Systems in Biomedicine

Our review examines the key aspects of using polymeric carriers in biomedicine. The section "Polymers for Biomedicine" provides an overview of different types of polymers, their structural features and properties that determine their use as drug delivery vehicles. The section "Polymeric Carriers" characterizes the role of polymeric delivery systems in modern medicine. The main forms of polymeric carriers are described, as well as their key advantages for drug delivery. The section "Preclinical and Clinical Trials of Polymeric Drug Carriers" reviews the examples of clinical and preclinical studies of polymeric forms used for antitumor therapy, therapy for bacterial and infectious diseases. The final section "Targeted Drug Delivery Systems" is devoted to the discussion of approaches, as well as ligands that provide targeted drug delivery using polymeric carriers. We have paid special attention to modern approaches for increasing the efficacy of antibacterial therapy using vector molecules.

Stimuli-responsive, methyl cellulose-based, interpenetrating network hydrogels: Non-covalent design, injectability, and controlled release

This paper demonstrates the molecular design of stimuli-responsive, methyl cellulose-based, injectable hydrogels consisting of two orthogonal supramolecular networks. Rapidly injectable hydrogels that undergo autonomous gelation without permanent cross-links are crucial for biomedical applications due to minimal invasiveness, adaptability to irregular target sites, and precise spatiotemporal control. However, they often lack sufficient mechanical strength, physicochemical stability, and high biocompatibility. Herein, we develop a molecular design of a non-covalent double-network system by strategically incorporating specific host-guest cross-linking sites into a thermo-responsive network, which is reinforced by interpenetration with a cellulose-based network via their sequential formation. The resulting hydrogel, composed of non-cytotoxic materials, demonstrates high cell viability (>90 %) until its concentration of 25 mg mL-1, rapid self-healing within 1 min, suitable injection pressure (1.1 kPa), and drug release behavior controllable by heat, chemicals, or ultrasound. Therefore, the hydrogel could be loaded with diclofenac (3.5 mg mL-1), a non-steroidal anti-inflammatory drug, and treat osteoarthritis when injected into a rat knee joint, achieving results comparable to those in a control group without osteoarthritis. This system thus holds promise for the delivery of various drugs as a responsive vector, offering synergistic effects via the inclusion of functional polymeric networks or exogenous additives for bio- or environment-related applications.

Recent Advances and Developments in Injectable Conductive Polymer Gels for Bioelectronics

Soft matter bioelectronics represents an emerging and interdisciplinary research frontier aiming to harness the synergy between biology and electronics for advanced diagnostic and healthcare applications. In this context, a whole family of soft gels have been recently developed with self-healing ability and tunable biological mimetic features to act as a tissue-like space bridging the interface between the electronic device and dynamic biological fluids and body tissues. This review article provides a comprehensive overview of electroactive polymer gels, formed by noncovalent intermolecular interactions and dynamic covalent bonds, as injectable electroactive gels, covering their synthesis, characterization, and applications. First, hydrogels crafted from conducting polymers (poly(3,4-ethylene-dioxythiophene) (PEDOT), polyaniline (PANi), and polypyrrole (PPy))-based networks which are connected through physical interactions (e.g., hydrogen bonding, π-π stacking, hydrophobic interactions) or dynamic covalent bonds (e.g., imine bonds, Schiff-base, borate ester bonds) are addressed. Injectable hydrogels involving hybrid networks of polymers with conductive nanomaterials (i.e., graphene oxide, carbon nanotubes, metallic nanoparticles, etc.) are also discussed. Besides, it also delves into recent advancements in injectable ionic liquid-integrated gels (iongels) and deep eutectic solvent-integrated gels (eutectogels), which present promising avenues for future research. Finally, the current applications and future prospects of injectable electroactive polymer gels in cutting-edge bioelectronic applications ranging from tissue engineering to biosensing are outlined.

Nanotechnology in Drug Delivery: Anatomy and Molecular Insight into the Self-Assembly of Peptide-Based Hydrogels

The bioavailability, release, and stability of pharmaceuticals under physicochemical conditions is the major cause of drug candidates failing during their clinical trials. Therefore, extensive efforts have been invested in the development of novel drug delivery systems that are able to transport drugs to a desired site and improve bioavailability. Hydrogels, and peptide hydrogels in particular, have been extensively investigated due to their excellent biocompatibility and biodegradability properties. However, peptide hydrogels often have weak mechanical strength, which limits their therapeutic efficacy. Therefore, a number of methods for improving their rheological properties have been established. This review will cover the broad area of drug delivery, focusing on the recent developments in this research field. We will discuss the variety of different types of nanocarrier drug delivery systems and then, more specifically, the significance and perspectives of peptide-based hydrogels. In particular, the interplay of intermolecular forces that govern the self-assembly of peptide hydrogels, progress made in understanding the distinct morphologies of hydrogels, and applications of non-canonical amino acids in hydrogel design will be discussed in more detail.

Zn@TA assisted dual cross-linked 3D printable glycol grafted chitosan hydrogels for robust antibiofilm and wound healing

Rapid regeneration of the injured tissue or organs is necessary to achieve the usual functionalities of the damaged parts. However, bacterial infections delay the regeneration process, a severe challenge in the personalized healthcare sector. To overcome these challenges, 3D-printable multifunctional hydrogels of Zn/tannic acid-reinforced glycol functionalized chitosan for rapid wound healing were developed. Polyphenol strengthened intermolecular connections, while glutaraldehyde stabilized 3D-printed structures. The hydrogel exhibited enhanced viscoelasticity (G'; 1.96 × 104 Pa) and adhesiveness (210 kPa). The dual-crosslinked scaffolds showed remarkable antibacterial activity against Bacillus subtilis (∼81 %) and Escherichia coli (92.75 %). The hydrogels showed no adverse effects on human dermal fibroblasts (HDFs) and macrophages (RAW 264.7), indicating their superior biocompatibility. The Zn/TA-reinforced hydrogels accelerate M2 polarization of macrophages through the activation of anti-inflammatory transcription factors (Arg-1, VEGF, CD163, and IL-10), suggesting better immunomodulatory effects, which is favorable for rapid wound regeneration. Higher collagen deposition and rapid re-epithelialization occurred in scaffold-treated rat groups vis-à-vis controls, demonstrating superior wound healing. Taken together, the developed multifunctional hydrogels have great potential for rapidly regenerating bacteria-infected wounds in the personalized healthcare sector.

Form Equals Function: Influence of Coacervate Architecture on Drug Delivery Applications

Complex coacervates, formed through electrostatic interactions between oppositely charged polymers, present a versatile platform for drug delivery, providing rapid assembly, selective encapsulation, and responsiveness to environmental stimuli. The architecture and properties of coacervates can be tuned by controlling structural and environmental design factors, which significantly impact the stability and delivery efficiency of the drugs. While environmental design factors such as salt, pH, and temperature play a crucial role in coacervate formation, structural design factors such as polymer concentration, polymer structure, mixing ratio, and chain length serve as the core framework that shapes coacervate architecture. These elements modulate the phase behavior and material properties of coacervates, allowing for a highly tunable system. In this review, we primarily analyze how these structural design factors contribute to the formation of diverse coacervate architecture, ranging from bulk coacervates to polyion complex micelles, vesicles, and cross-linked gels, though environmental design factors are considered. We then examine the effectiveness of these architectures in enhancing the delivery and efficacy of drugs across various administration routes, such as noninvasive (e.g., oral and transdermal) and invasive delivery. This review aims to provide foundational insights into the design of advanced drug delivery systems by examining how the origin and chemical structure of polymers influence coacervate architecture, which in turn defines their material properties. We then explore how the architecture can be tailored to optimize drug delivery for specific administration routes. This approach leverages the intrinsic properties derived from the coacervate architecture to enable targeted, controlled, and efficient drug release, ultimately enhancing therapeutic outcomes in precision medicine.

pH factors in chronic wound and pH-responsive polysaccharide-based hydrogel dressings

Chronic wounds present a significant healthcare challenge marked by complexities such as persistent bleeding, inhibited cell proliferation, dysregulated inflammation, vulnerability to infection, and compromised tissue remodeling. Conventional wound dressings often prove inadequate in addressing the intricate requirements of chronic wound healing, leading to slow healing and heightened susceptibility to infections in patients with prolonged medical conditions. Bacterial biofilms in chronic wounds pose an additional challenge due to drug resistance. Advanced wound dressings have emerged as promising tools in expediting the healing process. Among these, pH-responsive polysaccharide-based hydrogels exhibit immense prospect by adapting their functions to dynamic wound conditions. Despite their potential, the current literature lacks a thorough review of these wound dressings. This review bridges this gap by meticulously examining factors related to chronic wounds, current strategies for healing, and the mechanisms and potential applications of pH-responsive hydrogel wound dressings as an emerging therapeutic solution. Special focus is given to their remarkable antibacterial properties and significant self-healing abilities. It further explores the pH-monitoring functions of these dressings, elucidating the associated pH indicators. This synthesis of knowledge aims to guide future research and development in the field of pH-responsive wound dressings, providing valuable insights into their potential applications in wound care.

Stimulus-responsive biomacromolecule wound dressings for enhanced drug delivery in chronic wound healing: A review

Addressing the challenge of poor wound healing in chronic wounds remains complex, as the underlying physiological mechanisms are still not fully understood. Traditional wound dressings often fail to meet the specific needs of the chronic wound healing process. Recently, considerable interest has shifted toward employing biomacromolecule-based smart wound dressings to facilitate wound healing. These stimuli-responsive dressings have undergone substantial development to manage local drug delivery, demonstrating promising therapeutic effects in treating chronic wound defects. They have displayed improved drug release profiles both in vitro and in vivo. Recently, there have been advancements in the development of innovative dual and multi-stimuli responsive dressings that react to combinations of signals including pH-temperature, pH-enzyme, pH-ROS, pH-glucose, pH-NIR, and multiple stimuli. This paper offers an in-depth review of recent progress in responsive wound dressings based on biomacromolecules, with a specific focus on their design, drug release capabilities, and therapeutic advantages.

Anti-inflammatory dressing based on hyaluronic acid and hydroxyethyl starch for wound healing

Eliminating persistent inflammation and choosing dressings that provide the best healing environment is key to promoting wound healing. Dynamic and reversible hydrogels have attracted much attention because of their capacity to adapt to irregular wound surfaces. Herein, oxidized hydroxyethyl starch (OHES) and hyaluronic acid (HA-ADH) were crosslinked via the dynamic acylhydrazone bond to form an anti-inflammatory function hydrogel (HA-ADH/OHES@XT) that could release xanthatin (XT) slowly. The HA-ADH/OHES hydrogels showed an appropriate gelation time, notable water-retaining capacity, self-healing, suitable biodegradability, and good biocompatibility for wound healing applications. In vivo experiments demonstrated that HA-ADH/OHES@XT hydrogels promoted tissue regeneration and wound healing at a rate of approximately 89.1 % on day 20 by reducing inflammation, increasing collagen deposition, and promoting re-epithelialization, indicating their great potential as a wound dressing.

A Review of Advanced Hydrogel Applications for Tissue Engineering and Drug Delivery Systems as Biomaterials

Hydrogels are known for their high water retention capacity and biocompatibility and have become essential materials in tissue engineering and drug delivery systems. This review explores recent advancements in hydrogel technology, focusing on innovative types such as self-healing, tough, smart, and hybrid hydrogels, each engineered to overcome the limitations of conventional hydrogels. Self-healing hydrogels can autonomously repair structural damage, making them well-suited for applications in dynamic biomedical environments. Tough hydrogels are designed with enhanced mechanical properties, enabling their use in load-bearing applications such as cartilage regeneration. Smart hydrogels respond to external stimuli, including changes in pH, temperature, and electromagnetic fields, making them ideal for controlled drug release tailored to specific medical needs. Hybrid hydrogels, made from both natural and synthetic polymers, combine bioactivity and mechanical resilience, which is particularly valuable in engineering complex tissues. Despite these innovations, challenges such as optimizing biocompatibility, adjusting degradation rates, and scaling up production remain. This review provides an in-depth analysis of these emerging hydrogel technologies, highlighting their transformative potential in both tissue engineering and drug delivery while outlining future directions for their development in biomedical applications.

Lysozyme-Responsive Hydrogels of Chitosan-Streptomycin Conjugates for the On-Demand Release of Biofilm-Dispersing Enzymes for the Efficient Eradication of Oral Biofilms

Hydrogels with controlled degradation and sustained antibiofilm activity are promising biomaterials for the treatment of oral infections such as periodontitis or caries. In this article, an in situ forming chitosan-streptomycin hydrogel is developed that can target established bacterial biofilms in response to lysozyme, an enzyme that is overexpressed in saliva during oral infections. When the new hydrogel is applied to simulated oral biofilms, the overexpressed lysozyme degrades the hydrogel and releases chitosan-streptomycin oligosaccharides that can eradicate the biofilm. This work has shown that the coupling of chitosan and streptomycin can have a synergistic effect and that the new hydrogel based on chitosan-streptomycin conjugate can effectively combat biofilms of E. coli, S. aureus, and P. aeruginosa formed in vitro achieving a significant reduction in the biomass of the biofilm and a substantial reduction in the population of viable bacteria in established biofilms. Finally, the CS-Str hydrogel loaded with biofilm-disrupting enzymes, in particular, DNase I and/or DspB, showed a significantly increased ability to reduce the biofilm biomass of P. aeruginosa and S. aureus (by over 84% and up to 92%, respectively), resulting in a drastic reduction in cell viability, which fell below 4% for P. aeruginosa and below 5% for S. aureus.

Development and evaluation of an injectable ChitHCl-MgSO4-DDA hydrogel for bone regeneration: In vitro and in vivo studies on cell migration and osteogenesis enhancement

Nonunion and delayed union of the bone are situations in orthopedic surgery that can occur even if the bone alignment is correct and there is sufficient mechanical stability. Surgeons usually apply artificial bone grafts in bone fracture gaps or in bone defect sites for osteogenesis to improve bone healing; however, these bone graft materials have no osteoinductive or osteogenic properties, and fit the morphology of the fracture gap with difficulty. In this study, we developed an injectable chitosan-based hydrogel with MgSO4 and dextran oxidative, with the purpose to improve bone healing through introducing an engineered chitosan-based hydrogel. The developed hydrogel can gelate and fit with any morphology or shape, has good biocompatibility, can enhance the cell-migration capacity, and can improve extracellular calcium deposition. Moreover, the amount of new bone formed by injecting the hydrogel in the bone tunnel was assessed by an in vivo test. We believe this injectable chitosan-based hydrogel has great potential for application in the orthopedic field to improve fracture gap healing.

Polyethylene Glycol-Based Polymer-Drug Conjugates: Novel Design and Synthesis Strategies for Enhanced Therapeutic Efficacy and Targeted Drug Delivery

Due to their potential to enhance therapeutic results and enable targeted drug administration, polymer-drug conjugates that use polyethylene glycol (PEG) as both the polymer and the linker for drug conjugation have attracted much research. This study seeks to investigate recent developments in the design and synthesis of PEG-based polymer-drug conjugates, emphasizing fresh ideas that fill in existing knowledge gaps and satisfy the increasing need for more potent drug delivery methods. Through an extensive review of the existing literature, this study identifies key challenges and proposes innovative strategies for future investigations. The paper presents a comprehensive framework for designing and synthesizing PEG-based polymer-drug conjugates, including rational molecular design, linker selection, conjugation methods, and characterization techniques. To further emphasize the importance and adaptability of PEG-based polymer-drug conjugates, prospective applications are highlighted, including cancer treatment, infectious disorders, and chronic ailments.

Advances in the Development of Granular Microporous Injectable Hydrogels with Non-spherical Microgels and Their Applications in Tissue Regeneration

Granular microporous hydrogels are emerging as effective biomaterial scaffolds for tissue engineering due to their improved characteristics compared to traditional nanoporous hydrogels, which better promote cell viability, cell migration, cellular/tissue infiltration, and tissue regeneration. Recent advances have resulted in the development of granular hydrogels made of non-spherical microgels, which compared to those made of spherical microgels have higher macroporosity, more stable mechanical properties, and better ability to guide the alignment and differentiation of cells in anisotropic tissue. The development of these hydrogels as an emerging research area is attracting increasing interest in regenerative medicine. This review first summarizes the fabrication techniques available for non-spherical microgels with different aspect-ratios. Then, it introduces the development of granular microporous hydrogels made of non-spherical microgels, their physicochemical characteristics, and their applications in tissue regeneration. The limitations and future outlook of research on microporous granular hydrogels are also critically discussed.

Functionalized hydrogels as smart gene delivery systems to treat musculoskeletal disorders

Despite critical advances in regenerative medicine, the generation of definitive, reliable treatments for musculoskeletal diseases remains challenging. Gene therapy based on the delivery of therapeutic genetic sequences has strong value to offer effective, durable options to decisively manage such disorders. Furthermore, scaffold-mediated gene therapy provides powerful alternatives to overcome hurdles associated with classical gene therapy, allowing for the spatiotemporal delivery of candidate genes to sites of injury. Among the many scaffolds for musculoskeletal research, hydrogels raised increasing attention in addition to other potent systems (solid, hybrid scaffolds) due to their versatility and competence as drug and cell carriers in tissue engineering and wound dressing. Attractive functionalities of hydrogels for musculoskeletal therapy include their injectability, stimuli-responsiveness, self-healing, and nanocomposition that may further allow to upgrade of them as "intelligently" efficient and mechanically strong platforms, rather than as just inert vehicles. Such functionalized hydrogels may also be tuned to successfully transfer therapeutic genes in a minimally invasive manner in order to protect their cargos and allow for their long-term effects. In light of such features, this review focuses on functionalized hydrogels and demonstrates their competence for the treatment of musculoskeletal disorders using gene therapy procedures, from gene therapy principles to hydrogel functionalization methods and applications of hydrogel-mediated gene therapy for musculoskeletal disorders, while remaining challenges are being discussed in the perspective of translation in patients. STATEMENT OF SIGNIFICANCE: Despite advances in regenerative medicine, the generation of definitive, reliable treatments for musculoskeletal diseases remains challenging. Gene therapy has strong value in offering effective, durable options to decisively manage such disorders. Scaffold-mediated gene therapy provides powerful alternatives to overcome hurdles associated with classical gene therapy. Among many scaffolds for musculoskeletal research, hydrogels raised increasing attention. Functionalities including injectability, stimuli-responsiveness, and self-healing, tune them as "intelligently" efficient and mechanically strong platforms, rather than as just inert vehicles. This review introduces functionalized hydrogels for musculoskeletal disorder treatment using gene therapy procedures, from gene therapy principles to functionalized hydrogels and applications of hydrogel-mediated gene therapy for musculoskeletal disorders, while remaining challenges are discussed from the perspective of translation in patients.

Biocompatible and nondegradable microcapsules using an ethylamine-bridged EGCG dimer for successful therapeutic cell transplantation

Conventional alginate microcapsules are widely used for encapsulating therapeutic cells to reduce the host immune response. However, the exchange of monovalent cations with divalent cations for crosslinking can lead to a sol-gel phase transition, resulting in gradual degradation and swelling of the microcapsules in the body. To address this limitation, we present a biocompatible and nondegradable epigallocatechin-3-gallate (EGCG)-based microencapsulation with ethylamine-bridged EGCG dimers (EGCG(d)), denoted as 'Epi-Capsules'. These Epi-Capsules showed increased physical properties and Ca2+ chelating resistance compared to conventional alginate microcapsules. Horseradish peroxidase (HRP) treatment is very effective in increasing the stability of Epi-Capsule((+)HRP) due to the crosslinking between EGCG(d) molecules. Interestingly, the Epi-Capsules(oxi) using a pre-oxidized EGCG(d) can support long-term survival (>90 days) of xenotransplanted insulin-secreting islets in diabetic mice in vivo, which is attributed to its structural stability and reactive oxygen species (ROS) scavenging for lower fibrotic activity. Collectively, this EGCG-based microencapsulation can create Ca2+ chelating-resistance and anti-oxidant activity, which could be a promising strategy for cell therapies for diabetes and other diseases.

Multibiofunctional Self-healing Adhesive Injectable Nanocomposite Polysaccharide Hydrogel

Injectable hydrogels with good antimicrobial and antioxidant properties, self-healing characteristics, suitable mechanical properties, and therapeutic effects have great practical significance for developing treatments for pressing healthcare challenges. Herein, we have designed a novel, self-healing injectable hydrogel composite incorporating cross-linked biofunctional nanomaterials by mixing alginate aldehyde (Ox-Alg), quaternized chitosan (QCS), adipic acid dihydrazide (ADH), and copper oxide nanosheets surface functionalized with folic acid as the bioligand (F-CuO). Gelation was achieved under physiological conditions via the dynamic Schiff base cross-linking mechanism. The developed nanocomposite injectable hydrogel demonstrated the fast self-healing ability essential to bear deformation and outstanding antibacterial properties along with ROS scavenging ability. Furthermore, the optimized formulation of our F-CuO-embedded injectable hydrogel exhibited excellent cytocompatibility, blood compatibility, and in vitro wound healing performance. Taken together, the F-CuO nanosheet cross-linked injectable hydrogel composite presented herein offers a promising candidate biomaterial with multifunctional properties to develop solutions for addressing clinical challenges.

Bacterial-Infection-Triggered Release of Antibacterial Aldehyde from Triblock Copolyether Hydrogels

Bacterial infections pose a significant threat to public health worldwide. Hydrogel-based biomaterials have proven to be particularly useful in addressing persistent bacterial infections due to their stimuli-responsive degradability, high biocompatibility, ability to release antibacterial agents on demand, and long-lasting antibacterial activity. Herein, we fabricated ABA-type triblock copolyether hydrogels, wherein, hexanal, a bioactive aldehyde with antibacterial activity, was affixed to the hydrophobic micellar core via acetal linkage. The hydrogel exhibited degradation under acidic environment via the hydrolysis of acetal linkages, leading to the concomitant release of hexanal to exhibit highly potent bactericidal activity against both Escherichia coli and Staphylococcus aureus. Furthermore, a dual-mode release of the model therapeutic agent Nile Red from the hydrophobic micellar core of the hydrogel in conjunction with hexanal was demonstrated using this system. We anticipate that this study will provide a new platform for the development of hydrogels with tailorable release profiles for biologically active compounds that are activated by the acidification triggered by bacterial infection.

A Comprehensive Review of Nanoparticles: From Classification to Application and Toxicity

Nanoparticles are structures that possess unique properties with high surface area-to-volume ratio. Their small size, up to 100 nm, and potential for surface modifications have enabled their use in a wide range of applications. Various factors influence the properties and applications of NPs, including the synthesis method and physical attributes such as size and shape. Additionally, the materials used in the synthesis of NPs are primary determinants of their application. Based on the chosen material, NPs are generally classified into three categories: organic, inorganic, and carbon-based. These categories include a variety of materials, such as proteins, polymers, metal ions, lipids and derivatives, magnetic minerals, and so on. Each material possesses unique attributes that influence the activity and application of the NPs. Consequently, certain NPs are typically used in particular areas because they possess higher efficiency along with tenable toxicity. Therefore, the classification and the base material in the NP synthesis hold significant importance in both NP research and application. In this paper, we discuss these classifications, exemplify most of the major materials, and categorize them according to their preferred area of application. This review provides an overall review of the materials, including their application, and toxicity.

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.

Unrestricted molecular motions enable mild photothermy for recurrence-resistant FLASH antitumor radiotherapy

Ultrahigh dose-rate (FLASH) radiotherapy is an emerging technology with excellent therapeutic effects and low biological toxicity. However, tumor recurrence largely impede the effectiveness of FLASH therapy. Overcoming tumor recurrence is crucial for practical FLASH applications. Here, we prepared an agarose-based thermosensitive hydrogel containing a mild photothermal agent (TPE-BBT) and a glutaminase inhibitor (CB-839). Within nanoparticles, TPE-BBT exhibits aggregation-induced emission peaked at 900 nm, while the unrestricted molecular motions endow TPE-BBT with a mild photothermy generation ability. The balanced photothermal effect and photoluminescence are ideal for phototheranostics. Upon 660-nm laser irradiation, the temperature-rising effect softens and hydrolyzes the hydrogel to release TPE-BBT and CB-839 into the tumor site for concurrent mild photothermal therapy and chemotherapy, jointly inhibiting homologous recombination repair of DNA. The enhanced FLASH radiotherapy efficiently kills the tumor tissue without recurrence and obvious systematic toxicity. This work deciphers the unrestricted molecular motions in bright organic fluorophores as a source of photothermy, and provides novel recurrence-resistant radiotherapy without adverse side effects.

Injectable Hydrogels: A Paradigm Tailored with Design, Characterization, and Multifaceted Approaches

Biomaterials denoting self-healing and versatile structural integrity are highly curious in the biomedicine segment. The injectable and/or printable 3D printing technology is explored in a few decades back, which can alter their dimensions temporarily under shear stress, showing potential healing/recovery tendency with patient-specific intervention toward the development of personalized medicine. Thus, self-healing injectable hydrogels (IHs) are stunning toward developing a paradigm for tissue regeneration. This review comprises the designing of IHs, rheological characterization and stability, several benchmark consequences for self-healing IHs, their translation into tissue regeneration of specific types, applications of IHs in biomedical such as anticancer and immunomodulation, wound healing and tissue/bone regeneration, antimicrobial potentials, drugs, gene and vaccine delivery, ocular delivery, 3D printing, cosmeceuticals, and photothermal therapy as well as in other allied avenues like agriculture, aerospace, electronic/electrical industries, coating approaches, patents associated with therapeutic/nontherapeutic avenues, and numerous futuristic challenges and solutions.

Intra-Articular Injectable Biomaterials for Cartilage Repair and Regeneration

Osteoarthritis is a degenerative joint disease characterized by cartilage deterioration and subsequent inflammatory changes in the underlying bone. Injectable hydrogels have emerged as a promising approach for controlled drug delivery in cartilage therapies. This review focuses on the latest developments in utilizing injectable hydrogels as vehicles for targeted drug delivery to promote cartilage repair and regeneration. The pathogenesis of osteoarthritis is discussed to provide a comprehensive understanding of the disease progression. Subsequently, the various types of injectable hydrogels used for intra-articular delivery are discussed. Specifically, physically and chemically crosslinked injectable hydrogels are critically analyzed, with an emphasis on their fabrication strategies and their capacity to encapsulate and release therapeutic agents in a controlled manner. Furthermore, the potential of incorporating growth factors, anti-inflammatory drugs, and cells within these injectable hydrogels are discussed. Overall, this review offers a comprehensive guide to navigating the landscape of hydrogel-based therapeutics in osteoarthritis.

Application of Scaffold-Based Drug Delivery in Oral Cancer Treatment: A Novel Approach

This comprehensive review consolidates insights from two sources to emphasize the transformative impact of scaffold-based drug delivery systems in revolutionizing oral cancer therapy. By focusing on their core abilities to facilitate targeted and localized drug administration, these systems enhance therapeutic outcomes significantly. Scaffolds, notably those coated with anti-cancer agents such as cisplatin and paclitaxel, have proven effective in inhibiting oral cancer cell proliferation, establishing a promising avenue for site-specific drug delivery. The application of synthetic scaffolds, including Poly Ethylene Glycol (PEG) and poly(lactic-co-glycolic acid) (PLGA), and natural materials, like collagen or silk, in 3D systems has been pivotal for controlled release of therapeutic agents, executing diverse anti-cancer strategies. A key advancement in this field is the advent of smart scaffolds designed for sequential cancer therapy, which strive to refine drug delivery systems, minimizing surgical interventions, accentuating the significance of 3D scaffolds in oral cancer management. These systems, encompassing local drug-coated scaffolds and other scaffold-based platforms, hold the potential to transform oral cancer treatment through precise interventions, yielding improved patient outcomes. Local drug delivery via scaffolds can mitigate systemic side effects typically associated with chemotherapy, such as nausea, alopecia, infections, and gastrointestinal issues. Post-drug release, scaffolds foster a conducive environment for non-cancerous cell growth, adhering and proliferation, demonstrating restorative potential. Strategies for controlled and targeted drug delivery in oral cancer therapy span injectable self-assembling peptide hydrogels, nanocarriers, and dual drug-loaded nanofibrous scaffolds. These systems ensure prolonged release, synergistic effects, and tunable targeting, enhancing drug delivery efficiency while reducing systemic exposure. Smart scaffolds, capable of sequential drug release, transitioning to cell-friendly surfaces, and enabling combinatorial therapy, hold the promise to revolutionize treatment by delivering precise interventions and optimized outcomes. In essence, scaffold-based drug delivery systems, through their varied forms and functionalities, are reshaping oral cancer therapy. They target drug delivery efficiency, diminish side effects, and present avenues for personalization. Challenges like fabrication intricacy, biocompatibility, and scalability call for additional research. Nonetheless, the perspective on scaffold-based systems in oral cancer treatment is optimistic, as ongoing advancements aim to surmount current limitations and fully leverage their potential in cancer therapy.

A natural hydrogel complex improves intervertebral disc degeneration by correcting fatty acid metabolism and inhibiting nucleus pulposus cell pyroptosis

The degeneration of intervertebral discs is strongly associated with the occurrence of pyroptosis in nucleus pulposus (NP) cells. This pyroptosis is characterized by abnormal metabolism of fatty acids in the degenerative pathological state, which is further exacerbated by the inflammatory microenvironment and degradation of the extracellular matrix. In order to address this issue, we have developed a fibrin hydrogel complex (FG@PEV). This intricate formulation amalgamates the beneficial attributes of platelet extravasation vesicles, contributing to tissue repair and regeneration. Furthermore, this complex showcases exceptional stability, gradual-release capabilities, and a high degree of biocompatibility. In order to substantiate the biological significance of FG@PEV in intervertebral disc degeneration (IVDD), we conducted a comprehensive investigation into its potential mechanism of action through the integration of RNA-seq sequencing and metabolomics analysis. Furthermore, these findings were subsequently validated through experimentation in both in vivo and in vitro models. The experimental results revealed that the FG@PEV intervention possesses the capability to reshape the inflammatory microenvironment within the disc. It also addresses the irregularities in fatty acid metabolism of nucleus pulposus cells, consequently hindering cellular pyroptosis and slowing down disc degeneration through the regulation of extracellular matrix synthesis and degradation. As a result, this injectable gel system represents a promising and innovative therapeutic approach for mitigating disc degeneration.

Injectable hydrogels based on biopolymers for the treatment of ocular diseases

Injectable hydrogels based on biopolymers, fabricated utilizing diverse chemical and physical methodologies, exhibit exceptional physical, chemical, and biological properties. They have multifaceted applications encompassing wound healing, tissue regeneration, and across diverse scientific realms. This review critically evaluates their largely uncharted potential in ophthalmology, elucidating their diverse applications across an array of ocular diseases. These conditions include glaucoma, cataracts, corneal disorders (spanning from age-related degeneration to trauma, infections, and underlying chronic illnesses), retina-associated ailments (such as diabetic retinopathy, retinitis pigmentosa, and age-related macular degeneration (AMD)), eyelid abnormalities, and uveal melanoma (UM). This study provides a thorough analysis of applications of injectable hydrogels based on biopolymers across these ocular disorders. Injectable hydrogels based on biopolymers can be customized to have specific physical, chemical, and biological properties that make them suitable as drug delivery vehicles, tissue scaffolds, and sealants in the eye. For example, they can be engineered to have optimum viscosity to be injected intravitreally and sustain drug release to treat retinal diseases. Their porous structure and biocompatibility promote cellular infiltration to regenerate diseased corneal tissue. By accentuating their indispensable role in ocular disease treatment, this review strives to present innovative and targeted approaches in this domain, thereby advancing ocular therapeutics.

Interpenetrating gelatin/alginate mixed hydrogel: The simplest method to prepare an autoclavable scaffold

The choice of sterilization method for hydrogels used for cell culture influences the ease of preparing the gel. We prepared interpenetrating gelatin/calcium alginate hydrogels containing 1% (w/v) alginate and 1-16% (w/v) gelatin by molding with the mixture of gelatin/sodium alginate solution, followed by the addition of calcium ions by incubation in calcium chloride solution. It is the simplest method to prepare autoclavable gelatin/sodium hydrogel. We measured various properties of the hydrogels including volume, Young's modulus in the compression test, storage modulus, and loss modulus in the dynamic viscoelasticity measurement. The gelatin/alginate hydrogel can be easily fabricated into any shape by this method. After autoclave treatment, the hydrogel was shrunk to smaller than the original shape in similar figures. The shape of the gelatin/alginate hydrogel can be designed into any shape with the reduction ratio of the volume. Human osteosarcoma (HOS) cells adhered to the gelatin/alginate hydrogel and then proliferated. Gelatin/calcium alginate hydrogels with a high concentration are considered to be autoclavable culture substrates because of their low deformation and gelatin elution rate after autoclaving and the high amount of cells attached to the hydrogels.

Smart responsive in situ hydrogel systems applied in bone tissue engineering

The repair of irregular bone tissue suffers severe clinical problems due to the scarcity of an appropriate therapeutic carrier that can match dynamic and complex bone damage. Fortunately, stimuli-responsive in situ hydrogel systems that are triggered by a special microenvironment could be an ideal method of regenerating bone tissue because of the injectability, in situ gelatin, and spatiotemporally tunable drug release. Herein, we introduce the two main stimulus-response approaches, exogenous and endogenous, to forming in situ hydrogels in bone tissue engineering. First, we summarize specific and distinct responses to an extensive range of external stimuli (e.g., ultraviolet, near-infrared, ultrasound, etc.) to form in situ hydrogels created from biocompatible materials modified by various functional groups or hybrid functional nanoparticles. Furthermore, "smart" hydrogels, which respond to endogenous physiological or environmental stimuli (e.g., temperature, pH, enzyme, etc.), can achieve in situ gelation by one injection in vivo without additional intervention. Moreover, the mild chemistry response-mediated in situ hydrogel systems also offer fascinating prospects in bone tissue engineering, such as a Diels-Alder, Michael addition, thiol-Michael addition, and Schiff reactions, etc. The recent developments and challenges of various smart in situ hydrogels and their application to drug administration and bone tissue engineering are discussed in this review. It is anticipated that advanced strategies and innovative ideas of in situ hydrogels will be exploited in the clinical field and increase the quality of life for patients with bone damage.

An innovative Fuller's earth-based film-forming formulation for skin decontamination, through removal and entrapment of an organophosphorus compound, paraoxon-ethyl

Organophosphorus compounds (OPs), such as VX, pose a significant threat due to their neurotoxic and hazardous properties. Skin decontamination is essential to avoid irreversible effects. Fuller's earth (FE), a phyllosilicate conventionally employed in powder form, has demonstrated decontamination capacity against OPs. The aim of this study was to develop a formulation that forms a film on the skin, with a significant OP removal capacity (>95 %) coupled with sequestration capabilities, favorable drying time and mechanical properties to allow for easy application and removal, particularly in emergency context. Various formulations were prepared using different concentrations of polyvinyl alcohol (PVA), FE and surfactants. Their removal and sequestration capacity was tested using paraoxon-ethyl (POX), a chemical that simulates the behavior of VX. Formulations with removal capacity levels surpassing 95 % were mechanically characterized and cell viability assays were performed on Normal Human Dermal Fibroblast (NHDF). The four most promising formulations were used to assess decontamination efficacy on pig ear skin explants. These formulations showed decontamination levels ranging from 84.4 ± 4.7 % to 96.5 ± 1.3 %, which is equivalent to current decontamination methods. These results suggest that this technology could be a novel and effective tool for skin decontamination following exposure to OPs.

Novel Injectable Hydrogel Formulations and Gas Chromatography Analysis of the Residual Crosslinker in Formulations Intended for Pharmaceutical and Cosmetic Applications

Novel hyaluronic acid (HA) crosslinked with pentaerythritol tetra-acrylate (PT) injectable hydrogels was invented. These injectable hydrogel/dermal filler formulations were synthesised using HA and the acrylate PT as a crosslinker under basic pH conditions using thermal crosslinking methods (oven heating), which provides a simple, safe, and eco-friendly method for crosslinking in 4 h under 45 °C. Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) analyses were conducted to represent the difference between the formulations in terms of peak formation and pore size, respectively. The crosslinking was partial as is considered to be typical for dermal injectable fillers. The rheological properties of these formulations showed that these novel dermal injectables are highly promising, and the newly developed fillers could be used with better results for dermal anti-wrinkle corrections, shaping, and volumising reasons. Furthermore, crosslinker (PT) residual analysis was carried out to state the formulations that are valid and acceptable for intradermal usage. The results from the GC method validation revealed it was a suitable method for this study. The GC analysis of all five injectable hydrogel/filler formulations demonstrated the formulations HA-PT 1, 2, 3 and 4 were formulated using (0.05-0.1)% w/w PT containing residual PT monomers within the safe limits that were determined to be below (0.008% w/w). This work has shown the development of a novel injectable hydrogel/filler formulation for pharmaceutical and cosmetic applications can be prepared in a more sustainable and simple way using pentaerythritol tetra-acrylate as a crosslinker agent, which holds great promise for the industry's future advancement.

Advances in Hydrogel-Based Drug Delivery Systems

Hydrogels, with their distinctive three-dimensional networks of hydrophilic polymers, drive innovations across various biomedical applications. The ability of hydrogels to absorb and retain significant volumes of water, coupled with their structural integrity and responsiveness to environmental stimuli, renders them ideal for drug delivery, tissue engineering, and wound healing. This review delves into the classification of hydrogels based on cross-linking methods, providing insights into their synthesis, properties, and applications. We further discuss the recent advancements in hydrogel-based drug delivery systems, including oral, injectable, topical, and ocular approaches, highlighting their significance in enhancing therapeutic outcomes. Additionally, we address the challenges faced in the clinical translation of hydrogels and propose future directions for leveraging their potential in personalized medicine and regenerative healthcare solutions.

Chitin: A versatile biopolymer-based functional therapy for cartilage regeneration

Chitin is the second most abundant biopolymer and its inherent biological characteristics make it ideal to use for tissue engineering. For many decades, its properties like non-toxicity, abundant availability, ease of modification, biodegradability, biocompatibility, and anti-microbial activity have made chitin an ideal biopolymer for drug delivery. Research studies have also shown many potential benefits of chitin in the formulation of functional therapy for cartilage regeneration. Chitin and its derivatives can be processed into 2D/3D scaffolds, hydrogels, films, exosomes, and nano-fibers, which make it a versatile and functional biopolymer in tissue engineering. Chitin is a biomimetic polymer that provides targeted delivery of mesenchymal stem cells, especially of chondrocytes at the injected donor sites to accelerate regeneration by enhancing cell proliferation and differentiation. Due to this property, chitin is considered an interesting polymer that has a high potential to provide targeted therapy in the regeneration of cartilage. Our paper presents an overview of the method of extraction, structure, properties, and functional role of this versatile biopolymer in tissue engineering, especially cartilage regeneration.

Bionanofactory for green synthesis of collagen nanoparticles, characterization, optimization, in-vitro and in-vivo anticancer activities

Collagen nanoparticles (collagen-NPs) are promising biological polymer nanoparticles due to their exceptional biodegradability and biocompatibility. Collagen-NPs were bio-fabricated from pure marine collagen using the cell-free supernatant of a newly isolated strain, Streptomyces sp. strain NEAA-3. Streptomyces sp. strain NEAA-3 was identified as Streptomyces plicatus strain NEAA-3 based on its cultural, morphological, physiological properties and 16S rRNA sequence analysis. The sequence data has been deposited under accession number OR501412.1 in the GenBank database. The face-centered central composite design (FCCD) was used to improve collagen-NPs biosynthesis. The maximum yield of collagen-NPs was 9.33 mg/mL with a collagen concentration of 10 mg/mL, an initial pH of 7, an incubation time of 72 h, and a temperature of 35 °C. Using the desirability function approach, the collagen-NPs biosynthesis obtained after FCCD optimization (9.53 mg/mL) was 3.92 times more than the collagen-NPs biosynthesis obtained before optimization process (2.43 mg/mL). The TEM analysis of collagen-NPs revealed hollow sphere nanoscale particles with an average diameter of 33.15 ± 10.02 nm. FTIR spectra confirmed the functional groups of the collagen, collagen-NPs and the cell-free supernatant that are essential for the efficient capping of collagen-NPs. The biosynthesized collagen-NPs exhibited antioxidant activity and anticancer activity against HeP-G2, MCF-7 and HCT116 cell lines. Collagen-NPs assessed as an effective drug loading carrier with methotrexate (MTX), a chemotherapeutic agent. The TEM analysis revealed that the average size of MTX-loaded collagen-NPs was 35.4 ± 8.9 nm. The percentages of drug loading (DL%) and encapsulation efficiency (EE%) were respectively 22.67 and 45.81%.

Soft Injectable Sutures for Dose-Controlled and Continuous Drug Delivery

Transdermal drug delivery offers a promising alternative to traditional methods such as oral ingestion and hypodermic injection. Hypodermic injections are painful, while oral ingestion requires higher doses due to enzymatic degradation and poor absorption. While microneedles address the pain issue, they are limited to delivering small amounts of drugs and can be impractical due to peeling off with motion and sweat. Herein, this work proposes soft injectables using drug-carrying sutures for painless and localized sustained delivery in the dermis. These sutures can remain in place during delivery and are suitable for all skin types. Surgical sutures can also serve as open capillary microfluidic channels carrying drug from a wearable drug reservoir to enable long-term (weeks to months) transdermal drug delivery. The experiments focus on delivering 5-fluorouracil (5-FU), a cancer drug, and rhodamine B, a drug model. A fixed-length suture of 60 cm delivers 0.43 mg of 5-flurouracil in 15 min. The experiments also demonstrate a continuous drug delivery of rhodamine B for over 8 weeks at a rate of 0.0195 mL h-1 . The results highlight that soft injectable sutures are promising candidates for long-term sustained delivery of varying quantities of drugs over weeks period compared to hypodermic injection, oral ingestion, or microneedles.

Neurodiagnostic and neurotherapeutic potential of graphene nanomaterials

Graphene has emerged as a highly promising nanomaterial for a variety of advanced technologies, including batteries, energy, electronics, and biotechnologies. Its recent contribution to neurotechnology is particularly noteworthy because its superior conductivity, chemical resilience, biocompatibility, thermal stability, and scalable nature make it well-suited for measuring brain activity and plasticity in health and disease. Graphene-mediated compounds are microfabricated in two central methods: chemical processes with natural graphite and chemical vapor deposition of graphene in a film form. They are widely used as biosensors and bioelectronics for neurodiagnostic and neurotherapeutic purposes in several brain disorders, such as Parkinson's disease, stroke, glioma, epilepsy, tinnitus, and Alzheimer's disease. This review provides an overview of studies that have demonstrated the technical advances of graphene nanomaterials in neuroscientific and clinical applications. We also discuss current limitations and future demands in relation to the clinical application of graphene, highlighting its potential technological and clinical significance for treating brain disorders. Our review underscores the potential of graphene nanomaterials as powerful tools for advancing the understanding of the brain and developing new therapeutic strategies.

Elastic Macroporous Matrix-Supported In Situ Formation of Injectable Extracellular Matrix-Like Hydrogel for Carrying Growth Factors and Living Cells

Hydrogels loaded with biologics hold great potential for various biomedical applications such as regenerative medicine. However, biologics may lose bioactivity during hydrogel preparation, shipping, and storage. While many injectable hydrogels do not have this issue, they face a dilemma between fast gelation causing the difficulty of injection and slow gelation causing the escape of solutions from an injection site. The purpose of this study is to develop an affinity hydrogel by integrating a pre-formed elastic macroporous matrix and an injectable hydrogel. The data shows that the macroporous hydrogel matrix can hold a large volume of solutions for the formation of in situ injectable hydrogels loaded with growth factors or living cells. The cells can proliferate in the composite hydrogels. The growth factors can be stably sequestered and sustainably released due to the presence of aptamers. When both living cells and growth factors are loaded together into the hydrogels, cells can proliferate under culture conditions with a reduced serum level. Therefore, a macroporous and elastic matrix-supported formation of aptamer-functionalized injectable hydrogels is a promising method for developing the carriers of biologics.

Injectable hydrogels as emerging drug-delivery platforms for tumor therapy

Tumor therapy continues to be a prominent field within biomedical research. The development of various drug carriers has been propelled by concerns surrounding the side effects and targeting efficacy of various chemotherapeutic drugs and other therapeutic agents. These carriers strive to enhance drug concentration at tumor sites, minimize systemic side effects, and improve therapeutic outcomes. Among the reported delivery systems, injectable hydrogels have emerged as an emerging candidate for the in vivo delivery of chemotherapeutic drugs due to their minimal invasive drug delivery properties. This review systematically summarizes the composition and preparation methodologies of injectable hydrogels and further highlights the delivery mechanisms of diverse drugs using these hydrogels for tumor therapy, along with an in-depth discussion on the optimized therapeutic efficiency of drugs encapsulated within the hydrogels. The work concludes by providing a dynamic forward-looking perspective on the potential challenges and possible solutions of the in situ injectable hydrogels for non-surgical and real-time diagnostic applications.