Injectable hydrogels for delivering biotherapeutic molecules

Sustained Release Studies of Metformin Hydrochloride Drug Using Conducting Polymer/Gelatin-Based Composite Hydrogels

The present work highlights the synthesis and characterization of conducting polymer (CP)-based composite hydrogels with gelatin (GL-B) for their application as drug delivery vehicles. The spectral, morphological, and rheological properties of the synthesized hydrogels were explored, and morphological studies confirmed formation of an intense interpenetrating network. Rheological measurements showed variation in the flow behavior with the type of conducting polymer. The hydrogels showed a slow drug release rate of about 10 h due to the presence of the conducting polymer. The release kinetics were fitted in various mathematical models and were best fit in first order for PNA-, POPD-, and PANI-based GL-B hydrogels, and the PVDF/GL-B hydrogel was best fit in the zero-order models. The drug release was found to follow the order: POPD/GL-B > PANI/GL-B > PVDF/GL-B.

Nanoparticles incorporated hydrogels for delivery of antimicrobial agents: developments and trends

The prevention and treatment of microbial infections is an imminent global public health concern due to the poor antimicrobial performance of the existing antimicrobial regime and rapidly emerging antibiotic resistance in pathogenic microbes. In order to overcome these problems and effectively control bacterial infections, various new treatment modalities have been identified. To attempt this, various micro- and macro-molecular antimicrobial agents that function by microbial membrane disruption have been developed with improved antimicrobial activity and lesser resistance. Antimicrobial nanoparticle-hydrogels systems comprising antimicrobial agents (antibiotics, biological extracts, and antimicrobial peptides) loaded nanoparticles or antimicrobial nanoparticles (metal or metal oxide) constitute an important class of biomaterials for the prevention and treatment of infections. Hydrogels that incorporate nanoparticles can offer an effective strategy for delivering antimicrobial agents (or nanoparticles) in a controlled, sustained, and targeted manner. In this review, we have described an overview of recent advancements in nanoparticle-hydrogel hybrid systems for antimicrobial agent delivery. Firstly, we have provided an overview of the nanoparticle hydrogel system and discussed various advantages of these systems in biomedical and pharmaceutical applications. Thereafter, different hybrid hydrogel systems encapsulating antibacterial metal/metal oxide nanoparticles, polymeric nanoparticles, antibiotics, biological extracts, and antimicrobial peptides for controlling infections have been reviewed in detail. Finally, the challenges and future prospects of nanoparticle-hydrogel systems have been discussed.

Injecting hope: chitosan hydrogels as bone regeneration innovators

Spontaneous bone regeneration encounters substantial restrictions in cases of bone defects, demanding external intervention to improve the repair and regeneration procedure. The field of bone tissue engineering (BTE), which embraces a range of disciplines, offers compelling replacements for conventional strategies like autografts, allografts, and xenografts. Among the diverse scaffolding materials utilized in BTE applications, hydrogels have demonstrated great promise as templates for the regeneration of bone owing to their resemblance to the innate extracellular matrix. In spite of the advancement of several biomaterials, chitosan (CS), a natural biopolymer, has garnered significant attention in recent years as a beneficial graft material for producing injectable hydrogels. Injectable hydrogels based on CS formulations provide numerous advantages, including their capacity to absorb and preserve a significant amount of water, their minimally invasive character, the existence of porous structures, and their capability to adapt accurately to irregular defects. Moreover, combining CS with other naturally derived or synthetic polymers and bioactive materials has displayed its effectiveness as a feasible substitute for traditional grafts. We aim to spotlight the composition, production, and physicochemical characteristics and practical utilization of CS-based injectable hydrogels, explicitly focusing on their potential implementations in bone regeneration. We consider this review a fundamental resource and a source of inspiration for future research attempts to pioneer the next era of tissue-engineering scaffold materials.

Hydrogel: a new material for intravesical drug delivery after bladder cancer surgery

The standard treatment for non-muscle invasive bladder cancer (NMIBC) is transurethral resection of bladder tumor (TURBT). However, this procedure may miss small lesions or incompletely remove them, resulting in cancer recurrence or progression. As a result, intravesical instillation of chemotherapy or immunotherapy drugs is often used as an adjunctive treatment after TURBT to prevent cancer recurrence. In the traditional method, drugs are instilled into the patient's bladder through a urinary catheter under sterile conditions. However, this treatment exposes the bladder mucosa to the drug directly, leading to potential side effects like chemical cystitis. Furthermore, this treatment has several limitations, including a short drug retention period, susceptibility to urine dilution, low drug permeability, lack of targeted effect, and limited long-term clinical efficacy. Hydrogel, a polymer material with a high-water content, possesses solid elasticity and liquid fluidity, making it compatible with tissues and environmentally friendly. It exhibits great potential in various applications. One emerging use of hydrogels is in intravesical instillation. By employing hydrogels, drug dilution is minimized, and drug absorption, retention, and persistence in the bladder are enhanced due to the mucus-adhesive and flotation properties of hydrogel materials. Furthermore, hydrogels can improve drug permeability and offer targeting capabilities. This article critically examines the current applications and future prospects of hydrogels in the treatment of bladder cancer.

Designed modular protein hydrogels for biofabrication

Designing proteins that fold and assemble over different length scales provides a way to tailor the mechanical properties and biological performance of hydrogels. In this study, we designed modular proteins that self-assemble into fibrillar networks and, as a result, form hydrogel materials with novel properties. We incorporated distinct functionalities by connecting separate self-assembling (A block) and cell-binding (B block) domains into single macromolecules. The number of self-assembling domains affects the rigidity of the fibers and the final storage modulus G' of the materials. The mechanical properties of the hydrogels could be tuned over a broad range (G' = 0.1 - 10 kPa), making them suitable for the cultivation and differentiation of multiple cell types, including cortical neurons and human mesenchymal stem cells. Moreover, we confirmed the bioavailability of cell attachment domains in the hydrogels that can be further tailored for specific cell types or other biological applications. Finally, we demonstrate the versatility of the designed proteins for application in biofabrication as 3D scaffolds that support cell growth and guide their function. STATEMENT OF SIGNIFICANCE: Designed proteins that enable the decoupling of biophysical and biochemical properties within the final material could enable modular biomaterial engineering. In this context, we present a designed modular protein platform that integrates self-assembling domains (A blocks) and cell-binding domains (B blocks) within a single biopolymer. The linking of assembly domains and cell-binding domains this way provided independent tuning of mechanical properties and inclusion of biofunctional domains. We demonstrate the use of this platform for biofabrication, including neural cell culture and 3D printing of scaffolds for mesenchymal stem cell culture and differentiation. Overall, this work highlights how informed design of biopolymer sequences can enable the modular design of protein-based hydrogels with independently tunable biophysical and biochemical properties.

A biocompatible double network hydrogel based on poly (acrylic acid) grafted onto sodium alginate for doxorubicin hydrochloride anticancer drug release

This study involved the synthesis of a new biocompatible slow-release hydrogel named poly (acrylic acid) grafted onto sodium alginate (poly (AA-g-SA)) double network hydrogel (DNH). The hydrogel was created by polymerization of acrylic acid grafted onto sodium alginate polysaccharide using crosslinkers N,N'-methylenebisacrylamide and calcium chloride via free radical polymerization. The water absorbency of the poly (AA-g-SA) double network hydrogel was improved by optimizing the quantities of ammonium persulfate initiator, pH-sensitive monomer of acrylic acid, and crosslinkers. Various analytical techniques including attenuated total reflection Fourier-transformed infrared (ATR-FTIR), X-ray diffraction analysis (XRD), X-ray photoelectron spectroscopy (XPS), thermal gravimetric analysis (TGA), field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), atomic force microscopy (AFM), and Brunauer-Emmett-Teller specific surface area analysis (BET) were used to characterize the synthesized hydrogels. The swelling and on-off switching behaviors of the hydrogels were investigated in deionized (DI) water at different temperatures and pH values. The optimum poly (AA-g-SA) DNH was tested for in vitro release of a hydrophilic chemotherapeutic drug, doxorubicin hydrochloride (DOX). The eco-friendly hydrogel favorably optimized the DOX slow release owing to its swelling rate, high absorption and regeneration capabilities. The findings of this study may have significant implications for medical and scientific research.

Enhanced protective efficacy of an OprF/PcrV bivalent DNA vaccine against Pseudomonas aeruginosa using a hydrogel delivery system

Pseudomonas aeruginosa (PA) is one of the leading pathogens responsible for hospital-acquired infections. With the increasing antibiotic resistance of PA, clinical treatment has become increasingly challenging. DNA vaccines represent a promising approach for combating PA infection. However, the immune response induced by a single antigen is limited, and combination vaccines hold greater therapeutic potential. The highly conserved OprF and PcrV genes are attractive candidate antigens for vaccine development, but the poor delivery of such vaccines has limited their clinical application. In this study, we constructed an OprF/PcrV bivalent DNA vaccine, and a polyaspartamide/polyethylene glycol di-aldehyde (PSIH/PEG DA) hydrogel was formulated to improve DNA delivery. The OprF/PcrV DNA vaccine formulated with the PSIH/PEG DA hydrogel was carefully characterized in vitro and in vivo and showed suitable compatibility. The PSIH/PEG DA hydrogel formulation induced a mixed Th1/Th2/Th17 immune response in mice, leading to a significant increase in antibody titers, lymphocyte proliferation rates, and cytokine levels compared to those in mice treated with single or combined vaccines. The PSIH/PEG DA hydrogel delivery system significantly enhanced the immune protection of the DNA vaccine in a murine pneumonia model, as revealed by the reduced bacterial burden and inflammation in the mouse lungs and increased survival rate. In conclusion, the PSIH/PEG DA hydrogel delivery system can further enhance the immune efficacy of the combination OprF/PcrV DNA vaccine. This research provides a novel optimized strategy for the prevention and treatment of PA infection using DNA vaccines.

Commercial hydrogel product for drug delivery based on route of administration

Hydrogels are hydrophilic, three-dimensional, cross-linked polymers that absorb significant amounts of biological fluids or water. Hydrogels possess several favorable properties, including flexibility, stimulus-responsiveness, versatility, and structural composition. They can be categorized according to their sources, synthesis route, response to stimulus, and application. Controlling the cross-link density matrix and the hydrogels' attraction to water while they're swelling makes it easy to change their porous structure, which makes them ideal for drug delivery. Hydrogel in drug delivery can be achieved by various routes involving injectable, oral, buccal, vaginal, ocular, and transdermal administration routes. The hydrogel market is expected to grow from its 2019 valuation of USD 22.1 billion to USD 31.4 billion by 2027. Commercial hydrogels are helpful for various drug delivery applications, such as transdermal patches with controlled release characteristics, stimuli-responsive hydrogels for oral administration, and localized delivery via parenteral means. Here, we are mainly focused on the commercial hydrogel products used for drug delivery based on the described route of administration.

Nano-Micron Combined Hydrogel Microspheres: Novel Answer for Minimal Invasive Biomedical Applications

Hydrogels, key in biomedical research for their hydrophilicity and versatility, have evolved with hydrogel microspheres (HMs) of micron-scale dimensions, enhancing their role in minimally invasive therapeutic delivery, tissue repair, and regeneration. The recent emergence of nanomaterials has ushered in a revolutionary transformation in the biomedical field, which demonstrates tremendous potential in targeted therapies, biological imaging, and disease diagnostics. Consequently, the integration of advanced nanotechnology promises to trigger a new revolution in the realm of hydrogels. HMs loaded with nanomaterials combine the advantages of both hydrogels and nanomaterials, which enables multifaceted functionalities such as efficient drug delivery, sustained release, targeted therapy, biological lubrication, biochemical detection, medical imaging, biosensing monitoring, and micro-robotics. Here, this review comprehensively expounds upon commonly used nanomaterials and their classifications. Then, it provides comprehensive insights into the raw materials and preparation methods of HMs. Besides, the common strategies employed to achieve nano-micron combinations are summarized, and the latest applications of these advanced nano-micron combined HMs in the biomedical field are elucidated. Finally, valuable insights into the future design and development of nano-micron combined HMs are provided.

A novel injectable sericin hydrogel with strong fluorescence for tracing

Hydrogel systems with strong fluorescence, as convenient tracers or bio-probes, have attracted much attention in biomedical engineering. Currently, most hydrogels endowed fluorescent properties due to modifying additional fluorophores. However, these fluorophores owing to photobleaching and toxicity limit the practical applications of hydrogels. Herein, we prepared a novel self-luminescence hydrogel through double crosslinking glutaraldehyde and hydrogen peroxide/horseradish peroxidase (H2O2/HRP) with sericin protein. The double cross-linked sericin hydrogel exhibits strong green and red intrinsic fluorescence which can be excited over a wide range of wavelengths. Moreover, this hydrogel with strong intrinsic fluorescence could penetrate thick pigskin tissue, which has potential application in implantable bio-tracer areas. In addition to the above unique properties, this sericin hydrogel possesses two types of micropore structures with high porosity, swelling properties, pH-responsive degradability, super elasticity, injectability, viscosity, and excellent biocompatibility. The investigation could significantly expand the scope of protein hydrogels in biomedical applications.

Recent advances in fabricating injectable hydrogels via tunable molecular interactions for bio-applications

Hydrogels with three-dimensional structures have been widely applied in various applications because of their tunable structures, which can be easily tailored with desired functionalities. However, the application of hydrogel materials in bioengineering is still constrained by their limited dosage flexibility and the requirement of invasive surgical procedures. Compared to traditional hydrogels, injectable hydrogels, with shear-thinning and/or in situ formation properties, simplify the implantation process and reduce tissue invasion, which can be directly delivered to target sites using a syringe injection, offering distinct advantages over traditional hydrogels. These injectable hydrogels incorporate physically non-covalent and/or dynamic covalent bonds, granting them self-healing abilities to recover their structural integrity after injection. This review summarizes our recent progress in preparing injectable hydrogels and discusses their performance in various bioengineering applications. Moreover, the underlying molecular interaction mechanisms that govern the injectable and functional properties of hydrogels were characterized by using nanomechanical techniques such as surface forces apparatus (SFA) and atomic force microscopy (AFM). The remaining challenges and future perspectives on the design and application of injectable hydrogels are also discussed. This work provides useful insights and guides future research directions in the field of injectable hydrogels for bioengineering.

Injectable smart stimuli-responsive hydrogels: pioneering advancements in biomedical applications

Hydrogels have established their significance as prominent biomaterials within the realm of biomedical research. However, injectable hydrogels have garnered greater attention compared with their conventional counterparts due to their excellent minimally invasive nature and adaptive behavior post-injection. With the rapid advancement of emerging chemistry and deepened understanding of biological processes, contemporary injectable hydrogels have been endowed with an "intelligent" capacity to respond to various endogenous/exogenous stimuli (such as temperature, pH, light and magnetic field). This innovation has spearheaded revolutionary transformations across fields such as tissue engineering repair, controlled drug delivery, disease-responsive therapies, and beyond. In this review, we comprehensively expound upon the raw materials (including natural and synthetic materials) and injectable principles of these advanced hydrogels, concurrently providing a detailed discussion of the prevalent strategies for conferring stimulus responsiveness. Finally, we elucidate the latest applications of these injectable "smart" stimuli-responsive hydrogels in the biomedical domain, offering insights into their prospects.

Poly(ethylene Glycol) Methyl Ether Methacrylate-Based Injectable Hydrogels: Swelling, Rheological, and In Vitro Biocompatibility Properties with ATDC5 Chondrogenic Lineage

Here, we present the synthesis of a series of chemical homopolymeric and copolymeric injectable hydrogels based on polyethylene glycol methyl ether methacrylate (PEGMEM) alone or with 2-dimethylamino ethyl methacrylate (DMAEM). The objective of this study was to investigate how the modification of hydrogel components influences the swelling, rheological attributes, and in vitro biocompatibility of the hydrogels. The hydrogels' networks were formed via free radical polymerization, as assured by 1H nuclear magnetic resonance spectroscopy (1H NMR). The swelling of the hydrogels directly correlated with the monomer and the catalyst amounts, in addition to the molecular weight of the monomer. Rheological analysis revealed that most of the synthesized hydrogels had viscoelastic and shear-thinning properties. The storage modulus and the viscosity increased by increasing the monomer and the crosslinker fraction but decreased by increasing the catalyst. MTT analysis showed no potential toxicity of the homopolymeric hydrogels, whereas the copolymeric hydrogels were toxic only at high DMEAM concentrations. The crosslinker polyethylene glycol dimethacrylate (PEGDMA) induced inflammation in ATDC5 cells, as detected by the significant increase in nitric oxide synthase type II activity. The results suggest a range of highly tunable homopolymeric and copolymeric hydrogels as candidates for cartilage regeneration.

Peptide-Hydrogel Nanocomposites for Anti-Cancer Drug Delivery

Cancer is the second leading cause of death globally, but conventional anticancer drugs have side effects, mainly due to their non-specific distribution in the body in both cancerous and healthy cells. To address this relevant issue and improve the efficiency of anticancer drugs, increasing attention is being devoted to hydrogel drug-delivery systems for different kinds of cancer treatment due to their high biocompatibility and stability, low side effects, and ease of modifications. To improve the therapeutic efficiency and provide multi-functionality, different types of nanoparticles (NPs) can be incorporated within the hydrogels to form smart hydrogel nanocomposites, benefiting the advantages of both counterparts and suitable for advanced anticancer applications. Despite many papers on non-peptide hydrogel nanocomposites, there is limited knowledge about peptide-based nanocomposites, specifically in anti-cancer drug delivery. The aim of this short but comprehensive review is, therefore, to focus attention on the synergies resulting from the combination of NPs with peptide-based hydrogels. This review, which includes a survey of recent advances in this kind of material, does not aim to be an exhaustive review of hydrogel technology, but it instead highlights recent noteworthy publications and discusses novel perspectives to provide valuable insights into the promising synergic combination of peptide hydrogels and NPs for the design of novel anticancer drug delivery systems.

A Sterile, Injectable, and Robust Sericin Hydrogel Prepared by Degraded Sericin

The application of sericin hydrogels is limited mainly due to their poor mechanical strength, tendency to be brittle and inconvenient sterilization. To address these challenges, a sericin hydrogel exhibiting outstanding physical and chemical properties along with cytocompatibility was prepared through crosslinking genipin with degraded sericin extracted from fibroin deficient silkworm cocoons by the high temperature and pressure method. Our reported sericin hydrogels possess good elasticity, injectability, and robust behaviors. The 8% sericin hydrogel can smoothly pass through a 16 G needle. While the 12% sericin hydrogel remains intact until its compression ratio reaches 70%, accompanied by a compression strength of 674 kPa. 12% sericin hydrogel produce a maximum stretch of 740%, with breaking strength and tensile modulus of 375 kPa and 477 kPa respectively. Besides that, the hydrogel system demonstrated remarkable cell-adhesive capabilities, effectively promoting cell attachment and, proliferation. Moreover, the swelling and degradation behaviors of the hydrogels are pH responsiveness. Sericin hydrogel releases drugs in a sustained manner. Furthermore, this study addresses the challenge of sterilizing sericin hydrogels (sterilization will inevitably lead to the destruction of their structures). In addition, it challenges the prior notion that sericin extracted under high temperature and pressure is difficult to directly cross-linked into a stable hydrogel. This developed hydrogel system in this study holds promise to be a new multifunctional platform expanding the application area scope of sericin.

Injectable hydrogels for personalized cancer immunotherapies

The field of cancer immunotherapy has shown significant growth, and researchers are now focusing on effective strategies to enhance and prolong local immunomodulation. Injectable hydrogels (IHs) have emerged as versatile platforms for encapsulating and controlling the release of small molecules and cells, drawing significant attention for their potential to enhance antitumor immune responses while inhibiting metastasis and recurrence. IHs delivering natural killer (NK) cells, T cells, and antigen-presenting cells (APCs) offer a viable method for treating cancer. Indeed, it can bypass the extracellular matrix and gradually release small molecules or cells into the tumor microenvironment, thereby boosting immune responses against cancer cells. This review provides an overview of the recent advancements in cancer immunotherapy using IHs for delivering NK cells, T cells, APCs, chemoimmunotherapy, radio-immunotherapy, and photothermal-immunotherapy. First, we introduce IHs as a delivery matrix, then summarize their applications for the local delivery of small molecules and immune cells to elicit robust anticancer immune responses. Additionally, we discuss recent progress in IHs systems used for local combination therapy, including chemoimmunotherapy, radio-immunotherapy, photothermal-immunotherapy, photodynamic-immunotherapy, and gene-immunotherapy. By comprehensively examining the utilization of IHs in cancer immunotherapy, this review aims to highlight the potential of IHs as effective carriers for immunotherapy delivery, facilitating the development of innovative strategies for cancer treatment. In addition, we demonstrate that using hydrogel-based platforms for the targeted delivery of immune cells, such as NK cells, T cells, and dendritic cells (DCs), has remarkable potential in cancer therapy. These innovative approaches have yielded substantial reductions in tumor growth, showcasing the ability of hydrogels to enhance the efficacy of immune-based treatments. STATEMENT OF SIGNIFICANCE: As cancer immunotherapy continues to expand, the mode of therapeutic agent delivery becomes increasingly critical. This review spotlights the forward-looking progress of IHs, emphasizing their potential to revolutionize localized immunotherapy delivery. By efficiently encapsulating and controlling the release of essential immune components such as T cells, NK cells, APCs, and various therapeutic agents, IHs offer a pioneering pathway to amplify immune reactions, moderate metastasis, and reduce recurrence. Their adaptability further shines when considering their role in emerging combination therapies, including chemoimmunotherapy, radio-immunotherapy, and photothermal-immunotherapy. Understanding IHs' significance in cancer therapy is essential, suggesting a shift in cancer treatment dynamics and heralding a novel period of focused, enduring, and powerful therapeutic strategies.

Curcumin-loaded methacrylate pullulan with grafted carboxymethyl-β-cyclodextrin to form hydrogels for wound healing: In vitro evaluation

A pullulan (Pul)-derivative hydrogel was developed by introducing methacrylate (MA) groups and β-cyclodextrin (βCD) to form a Pul-βCD-MA hydrogel by UV cross-linking. The MA was expected to improve the hydrogel's mechanical properties and the βCD to increase the solubility of curcumin. Pul-βCD-MA was successfully synthesized, as confirmed by the 1H NMR and FTIR spectra. Hydrogels were formed at Pul-βCD-MA concentrations of 5 %, 7.5 %, or 10 % w/v. Pul-βCD-MA showed enhanced curcumin solubility compared to Pul or Pul-MA. The morphological analysis of the hydrogel showed a porous structure. The concentration of βCD affected the hydrogels' mechanical properties, and the 7.5 % hydrogel (with or without curcumin) did not fracture. The cumulative release of curcumin in the 7.5 % Pul-βCD-MA hydrogel was 60 % over 8 h. The release profile fit the Korsmeyer-Peppas model. In vitro cytotoxicity tests revealed that hydrogels were biocompatible with human primary dermal fibroblast cells. Curcumin-loaded Pul-βCD-MA hydrogels significantly accelerated wound healing compared to Pul-βCD-MA hydrogels without curcumin loading. Therefore, the Pul derivative's hydrogel may be a promising material for wound healing.

In Situ Gelling Hydroxypropyl Cellulose Formulation Comprising Cannabidiol-Loaded Block Copolymer Micelles for Sustained Drug Delivery

Cannabidiol (CBD) is a natural terpenophenolic compound with known pharmacological activities, but the poor solubility of CBD in water limits its widespread use in medicine and pharmacy. Polymeric (nano)carriers demonstrated high potential for enhancing the solubility and therapeutic activity of lipophilic drugs such as CBD. Here, we report the elaboration of a novel hydroxypropyl cellulose (HPC)-based in situ gelling formulation for controlled delivery of CBD. In the first stage, nanosized polymeric micelles from poly(ethylene oxide)-block-poly(α-cinnamyl-ε-caprolactone-co-ε-caprolactone) (PEO-b-P(CyCL-co-CL) diblock copolymers) were used to increase the solubility of CBD in water. Different copolymers were assessed, and the carrier with the highest encapsulation efficiency (EE) and drug loading capacity (DLC) was selected for further elaboration of nanocomposite in situ gel formulations. Next, the sol-to-gel transition behavior of HPC as a function of K2SO4 concentration in the aqueous solution was investigated by microcalorimetry and dynamic oscillatory rheology, and the optimal formulation capable of forming a physical gel under physiological conditions was determined. Finally, injectable nanocomposite hydrogels comprising cannabidiol were fabricated, and their drug release profile and cytotoxicity against human tumor cell lines were evaluated. The in situ gels exhibited prolonged drug release over 12 h, controlled by gel erosion, and the cytotoxicity of formulated cannabidiol was comparable with that of a free drug.

Nano-residronate loaded κ-carrageenan-based injectable hydrogels for bone tissue regeneration

Bone tissue possesses intrinsic regenerative capabilities to address deformities; however, its ability to repair defects caused by severe fractures, tumor resections, osteoporosis, joint arthroplasties, and surgical reconsiderations can be hindered. To address this limitation, bone tissue engineering has emerged as a promising approach for bone repair and regeneration, particularly for large-scale bone defects. In this study, an injectable hydrogel based on kappa-carrageenan-co-N-isopropyl acrylamide (κC-co-NIPAAM) was synthesized using free radical polymerization and the antisolvent evaporation technique. The κC-co-NIPAAM hydrogel's cross-linked structure was confirmed using Fourier transform infrared spectra (FTIR) and nuclear magnetic resonance (1H NMR). The hydrogel's thermal stability and morphological behavior were assessed using thermogravimetric analysis (TGA) and scanning electron microscopy (SEM), respectively. Swelling and in vitro drug release studies were conducted at varying pH and temperatures, with minimal swelling and release observed at low pH (1.2) and 25 °C, while maximum swelling and release occurred at pH 7.4 and 37oC. Cytocompatibility analysis revealed that the κC-co-NIPAAM hydrogels were biocompatible, and hematoxylin and eosin (H&E) staining demonstrated their potential for tissue regeneration and enhanced bone repair compared to other experimental groups. Notably, digital x-ray examination using an in vivo bone defect model showed that the κC-co-NIPAAM hydrogel significantly improved bone regeneration, making it a promising candidate for bone defects.

Unveiling pro-angiogenesis and drug delivery using dual-bio polymer with bio-ceramic based nanocomposite hydrogels

In regenerative medicine, blood vessel development is of utmost importance as it enables the restoration of blood flow to tissues, and facilitate rapid vascularization in clinical tissue-engineered grafts. Herein, we fabricate the nanocomposite hydrogels from BG (clinophosinaite), alginate, Polyethylene glycol (PEG) and Dexamethasone (DEX) for the dual applications of drug delivery and angiogenesis assay. The hydrogels were fabricated through cross-linking approach and termed as alginate/PEG (A), alginate/PEG/clinophosinaite (AC), and alginate/PEG/clinophosinaite/DEX (ACD) that further subjected to structural characterization, using powder X-ray diffraction, and fourier-transform infrared spectroscopy. Porous nanostructures and sheets were imaged using field emission scanning electron microscopy (FESEM), which aid in nutrient and oxygen transport to support angiogenesis. The nanocomposite hydrogels evidently demonstrated good hemocompatibility and fully hydrophilic (30.20°). By means of liquid displacement technique, the nanocomposite hydrogel achieves 47% of porosity with the compressive strength about 0.04 MPa. In alginate/PEG/clinophosinaite and alginate/PEG/clinophosinaite/DEX systems, water absorption capacity reached 85% in 6 h and maintained 90% retention after 12 h. Further, leachable tests revealed that the hydrogel had not deformed even after 24 h. In vitro drug release studies evidently divulge sustainable delivery of DEX from alginate/PEG/clinophosinaite/DEX hydrogel with superior characteristics for drug release. The angiogenesis assay also evidently revealed that the AC and ACD hydrogels, demonstrated higher angiogenic properties with, promoted blood vessel development.

Polysaccharide-Based Nanogels to Overcome Mucus, Skin, Cornea, and Blood-Brain Barriers: A Review

Nanocarriers have been extensively developed in the biomedical field to enhance the treatment of various diseases. However, to effectively deliver therapeutic agents to desired target tissues and enhance their pharmacological activity, these nanocarriers must overcome biological barriers, such as mucus gel, skin, cornea, and blood-brain barriers. Polysaccharides possess qualities such as excellent biocompatibility, biodegradability, unique biological properties, and good accessibility, making them ideal materials for constructing drug delivery carriers. Nanogels, as a novel drug delivery platform, consist of three-dimensional polymer networks at the nanoscale, offering a promising strategy for encapsulating different pharmaceutical agents, prolonging retention time, and enhancing penetration. These attractive properties offer great potential for the utilization of polysaccharide-based nanogels as drug delivery systems to overcome biological barriers. Hence, this review discusses the properties of various barriers and the associated constraints, followed by summarizing the most recent development of polysaccharide-based nanogels in drug delivery to overcome biological barriers. It is expected to provide inspiration and motivation for better design and development of polysaccharide-based drug delivery systems to enhance bioavailability and efficacy while minimizing side effects.

Injectable hydrogels for cartilage and bone tissue regeneration: A review

Annually, millions of patients suffer from irreversible injury owing to the loss or failure of an organ or tissue caused by accident, aging, or disease. The combination of injectable hydrogels and the science of stem cells have emerged to address this persistent issue in society by generating minimally invasive treatments to augment tissue function. Hydrogels are composed of a cross-linked network of polymers that exhibit a high-water retention capacity, thereby mimicking the wet environment of native cells. Due to their inherent mechanical softness, hydrogels can be used as needle-injectable stem cell carrier materials to mend tissue defects. Hydrogels are made of different natural or synthetic polymers, displaying a broad portfolio of eligible properties, which include biocompatibility, low cytotoxicity, shear-thinning properties as well as tunable biological and physicochemical properties. Presently, novel ongoing developments and native-like hydrogels are increasingly being used broadly to improve the quality of life of those with disabling tissue-related diseases. The present review outlines various future and in-vitro applications of injectable hydrogel-based biomaterials, focusing on the newest ongoing developments of in-situ forming injectable hydrogels for bone and cartilage tissue engineering purposes.

Crosstalk between ferroptosis and chondrocytes in osteoarthritis: a systematic review of in vivo and in vitro studies

Purpose

Recent scientific reports have revealed a close association between ferroptosis and the occurrence and development of osteoarthritis (OA). Nevertheless, the precise mechanisms by which ferroptosis influences OA and how to hobble OA progression by inhibiting chondrocyte ferroptosis have not yet been fully elucidated. This study aims to conduct a comprehensive systematic review (SR) to address these gaps.

Methods

Following the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020, we conducted a comprehensive search of the Embase, Ovid, ProQuest, PubMed, Scopus, the Cochrane Library, and Web of Science databases to identify relevant studies that investigate the association between ferroptosis and chondrocytes in OA. Our search included studies published from the inception of these databases until January 31st, 2023. Only studies that met the predetermined quality criteria were included in this SR.

Results

In this comprehensive SR, a total of 21 studies that met the specified criteria were considered suitable and included in the current updated synthesis. The mechanisms underlying chondrocyte ferroptosis and its association with OA progression involve various biological phenomena, including mitochondrial dysfunction, dysregulated iron metabolism, oxidative stress, and crucial signaling pathways.

Conclusion

Ferroptosis in chondrocytes has opened an entirely new chapter for the investigation of OA, and targeted regulation of it is springing up as an attractive and promising therapeutic tactic for OA.

Systematic review registration

https://inplasy.com/inplasy-2023-3-0044/, identifier INPLASY202330044.

Hydrogel-Based Biomaterial as a Scaffold for Gingival Regeneration: A Systematic Review of In Vitro Studies

BACKGROUND

Hydrogel is considered a promising scaffold biomaterial for gingival regeneration. In vitro experiments were carried out to test new potential biomaterials for future clinical practice. The systematic review of such in vitro studies could synthesize evidence of the characteristics of the developing biomaterials. This systematic review aimed to identify and synthesize in vitro studies that assessed the hydrogel scaffold for gingival regeneration.

METHODS

Data on experimental studies on the physical and biological properties of hydrogel were synthesized. A systematic review of the PubMed, Embase, ScienceDirect, and Scopus databases was conducted according to the Preferred Reporting System for Systematic Reviews and Meta-Analyses (PRISMA) 2020 statement guidelines. In total, 12 original articles on the physical and biological properties of hydrogels for gingival regeneration, published in the last 10 years, were identified.

RESULTS

One study only performed physical property analyses, two studies only performed biological property analyses, and nine studies performed both physical and biological property analyses. The incorporation of various natural polymers such as collagen, chitosan, and hyaluronic acids improved the biomaterial characteristics. The use of synthetic polymers faced some drawbacks in their physical and biological properties. Peptides, such as growth factors and arginine-glycine-aspartic acid (RGD), can be used to enhance cell adhesion and migration. Based on the available primary studies, all studies successfully present the potential of hydrogel characteristics in vitro and highlight the essential biomaterial properties for future periodontal regenerative treatment.

Biopolymer-Based Nanogel Approach in Drug Delivery: Basic Concept and Current Developments

Due to their increased surface area, extent of swelling and active substance-loading capacity and flexibility, nanogels made from natural and synthetic polymers have gained significant interest in scientific and industrial areas. In particular, the customized design and implementation of nontoxic, biocompatible, and biodegradable micro/nano carriers makes their usage very feasible for a range of biomedical applications, including drug delivery, tissue engineering, and bioimaging. The design and application methodologies of nanogels are outlined in this review. Additionally, the most recent advancements in nanogel biomedical applications are discussed, with particular emphasis on applications for the delivery of drugs and biomolecules.

High-Strength, High-Water-Retention Hemicellulose-Based Hydrogel and Its Application in Urea Slow Release

The use of fertilizer is closely related to crop growth and environmental protection in agricultural production. It is of great significance to develop environmentally friendly and biodegradable bio-based slow-release fertilizers. In this work, porous hemicellulose-based hydrogels were created, which had excellent mechanical properties, water retention properties (the water retention ratio in soil was 93.8% after 5 d), antioxidant properties (76.76%), and UV resistance (92.2%). This improves the efficiency and potential of its application in soil. In addition, electrostatic interaction and coating with sodium alginate produced a stable core-shell structure. The slow release of urea was realized. The cumulative release ratio of urea after 12 h was 27.42% and 11.38%, and the release kinetic constants were 0.0973 and 0.0288, in aqueous solution and soil, respectively. The sustained release results demonstrated that urea diffusion in aqueous solution followed the Korsmeyer-Peppas model, indicating the Fick diffusion mechanism, whereas diffusion in soil adhered to the Higuchi model. The outcomes show that urea release ratio may be successfully slowed down by hemicellulose hydrogels with high water retention ability. This provides a new method for the application of lignocellulosic biomass in agricultural slow-release fertilizer.

Exploring the Interplay of Antimicrobial Properties and Cellular Response in Physically Crosslinked Hyaluronic Acid/ε-Polylysine Hydrogels

The reduction of tissue cytotoxicity and the improvement of cell viability are of utmost significance, particularly in the realm of green chemistry. Despite substantial progress, the threat of local infections remains a concern. Therefore, hydrogel systems that provide mechanical support and a harmonious balance between antimicrobial efficacy and cell viability are greatly needed. Our study explores the preparation of physically crosslinked, injectable, and antimicrobial hydrogels using biocompatible hyaluronic acid (HA) and antimicrobial ε-polylysine (ε-PL) in different weight ratios (10 wt% to 90 wt%). The crosslinking was achieved by forming a polyelectrolyte complex between HA and ε-PL. The influence of HA content on the resulting HA/ε-PL hydrogel physicochemical, mechanical, morphological, rheological, and antimicrobial properties was evaluated, followed by an inspection of their in vitro cytotoxicity and hemocompatibility. Within the study, injectable, self-healing HA/ε-PL hydrogels were developed. All hydrogels showed antimicrobial properties against S. aureus, P. aeruginosa, E. coli, and C. albicans, where HA/ε-PL 30:70 (wt%) composition reached nearly 100% killing efficiency. The antimicrobial activity was directly proportional to ε-PL content in the HA/ε-PL hydrogels. A decrease in ε-PL content led to a reduction of antimicrobial efficacy against S. aureus and C. albicans. Conversely, this decrease in ε-PL content in HA/ε-PL hydrogels was favourable for Balb/c 3T3 cells, leading to the cell viability of 152.57% for HA/ε-PL 70:30 and 142.67% for HA/ε-PL 80:20. The obtained results provide essential insights into the composition of the appropriate hydrogel systems able to provide not only mechanical support but also the antibacterial effect, which can offer opportunities for developing new, patient-safe, and environmentally friendly biomaterials.

Multifunctional chitosan/alginate hydrogel incorporated with bioactive glass nanocomposites enabling photothermal and nitric oxide release activities for bacteria-infected wound healing

It is highly desirable to develop novel multifunctional wound dressing materials capable of delivering active molecules capable of resolving bacterial infections and replenishment of appropriate growth factors for bacteria-infected wound healing. Polysaccharides have numerous biomedical benefits and have been widely used to construct biomaterial scaffolds. Herein, multifunctional chitosan/alginate hydrogel decorated with β-cyclodextrin (β-CD) modified polydopamine (PDA)-bioactive glass (BG) nanoparticles (NPs) integrating photothermal performance and nitric-oxide release activities for the treatment of bacterially infected wounds is presented. As the NO precursor N,N'-di-sec-butyl-N,N'-dinitroso-1,4-phenylenediamine (BNN6) encapsulated into the hydrophobic cavity of β-CD on the PDA-coated BG NPs, the resultant NO@CD-PDA/BG NPs, are imparted with the feature of NIR triggered NO release and desired PTT/NO synergetic antibacterial effects. Furthermore, the release of NO, Ca, and Si ions from the NO@CD-PDA/BG NPs, has the benefit of regulating inflammation, promoting fibroblast proliferation, and stimulating angiogenesis. Besides, the chitosan/alginate hydrogel scaffolds provided a suitable microenvironment to accelerate wound healing. By applying the multifunctional chitosan/alginate nanocomposite hydrogel to S. aureus-infected full-thickness skin defect mouse model, the authors demonstrated that chitosan/alginate nanocomposite hydrogel has multiple functions in preventing bacterial infections, accelerating angiogenesis and wound regeneration, indicating promising application in wound healing.

Piperine Liposome-Embedded in Hyaluronan Hydrogel as an Effective Platform for Prevention of Postoperative Peritoneal Adhesion

This study aimed to prepare piperine (PIP) loaded liposomes in hyaluronic acid (HA) hydrogel to provide a hybrid superstructure for postoperative adhesion prevention. Liposomes were prepared using thin-film hydration method. The optimised formulation was characterised by size, SEM, TEM, FTIR, encapsulation efficiency (EE)% (w/w), and release pattern. Liposome-in-hydrogel formulation was investigated by rheology, SEM, and release studies. The efficacy was evaluated in a rat peritoneal abrasion model. EE% (w/w) increased with increasing lipid concentration from 10 to 30; however, a higher percentage of Chol reduced EE% (w/w). The optimised liposome (EE: 68.10 ± 4.18% (w/w), average diameter: 513 ± 14.67 nm, PDI: 0.15 ± 0.04) was used for hydrogel embedding. No sign of adhesion in 5/8 rats and no collagen deposition confirmed the in vivo effectiveness of the optimised formulation. Overall, providing a sustained delivery of PIP, the developed liposome-in-hydrogel formulation can be a promising carrier to prevent postoperative adhesion.

Pharmacokinetic Evaluation of Thermosensitive Sustained Release Formulations Developed for Subcutaneous Delivery of Protein Therapeutics

Injectable, thermosensitive hydrogels, constructed from cross-linked polymers, can offset the limitations of other sustained release delivery systems, overcome constrains of available therapies, and improve patient compliance to chronic therapy. The goal of this project was to identify and evaluate such sustained release, in situ formulations that can help achieve prolonged exposure of protein therapeutics with a short systemic half-life. Natural polymers were used to develop injectable, thermosensitive in situ hydrogels and single-chain variable fragment (scFv) of trastuzumab was used as the model protein with a short half-life. The three polymer combinations tested were: (1) Chitosan and β-glycerophosphate, (2) Chitosan, β-glycerophosphate, and Hyaluronic Acid, and (3) Hyaluronic Acid and Dextran. In vitro drug release experiments were conducted, using different combinations of various polymer concentrations and different drug loading amounts, to identify optimal combinations with prolonged and controlled drug release while exhibiting minimal burst release effect. Select formulations were injected subcutaneously in normal mice to evaluate the pharmacokinetics of scFv for 14 days and identify drug release kinetics in vivo. A two-compartment PK model was also established to quantitatively characterize the release kinetics and disposition of scFv following in vivo administration of the hydrogels. The scFv was undetectable in plasma after 4 and 24 hours following intravenous and subcutaneous administration, respectively. However, all three hydrogel systems were found to provide controlled release of scFv in vivo and maintain detectable concentrations of scFv for at least 14 days. The results suggested that subcutaneous injection of thermosensitive in situ hydrogels may be used to achieve sustained exposure of protein therapeutics which have a very short half-life and thus require frequent administration.

Supramolecular hydrogel for programmable delivery of therapeutics to cancer multidrug resistance

Multidrug resistance (MDR) has been considered as a major adversary in oncologic chemotherapy. To simultaneously overcome drug resistance and inhibit tumor growth, it is essential to develop a drug delivery system that can carry and release multiple therapeutic agents with spatiotemporal control. In this study, we developed a hydrogel containing an enzyme-cleavable peptide motif, with a network structure formed by 4-armed polyethylene glycol (PEG) crosslinked by complementary nucleic acid sequences. Hydrogen bond formation between nucleobase pairing allows the hydrogel to be injectable, and the peptide motif grants deliberate control over hydrogel degradation and the responsive drug release. Moreover, MDR-targeted siRNAs are complexed with stearyl-octaarginine (STR-R8), while doxorubicin (Dox) is intercalated with DNA and nanoclay structures in this hydrogel to enhance therapeutic efficacy and overcome MDR. The results show a successful configuration of a hydrogel network with in situ gelation property, injectability, and degradability in the presence of tumor-associated enzyme, MMP-2. The synergistic effect by combining MDR-targeted siRNAs and Dox manifests with the enhanced anti-cancer effect on drug resistant breast cancer cells in both in vitro and in vivo tumor models. We suggest that with the tailor-designed hydrogel system, multidrug resistance in tumor cells can be significantly inhibited by the co-delivery of multiple therapeutics with spatial-temporal control release.

Metal-coordination synthesis of a natural injectable photoactive hydrogel with antibacterial and blood-aggregating functions for cancer thermotherapy and mild-heating wound repair

Photothermal therapy (PTT) is a promising approach for treating cancer. However, it suffers from the formation of local lesions and subsequent bacterial infection in the damaged area. To overcome these challenges, the strategy of mild PTT following the high-temperature ablation of tumors is studied to achieve combined tumor suppression, wound healing, and bacterial eradication using a hydrogel. Herein, Bi₂S₃ nanorods (NRs) are employed as a photothermal agent and coated with hyaluronic acid to obtain BiH NRs with high colloidal stability. These NRs and allantoin are loaded into an injectable Fe³⁺-coordinated hydrogel composed of sodium alginate (Alg) and Farsi gum (FG), which is extracted from Amygdalus scoparia Spach. The hydrogel can be used for localized cancer therapy by high-temperature PTT, followed by wound repair through the combination of mild hyperthermia and allantoin-mediated induction of cell proliferation. In addition, an outstanding blood clotting effect is observed due to the water-absorbing ability and negative charge of FG and Alg as well as the porous structure of hydrogels. The hydrogels also eradicate infection owing to the local heat generation and intrinsic antimicrobial activity of the NRs. Lastly, in vivo studies reveal an efficient photothermal-based tumor eradication and accelerated wound healing by the hydrogel.

Fucoidan in Pharmaceutical Formulations: A Comprehensive Review for Smart Drug Delivery Systems

Fucoidan is a heterogeneous group of polysaccharides isolated from marine organisms, including brown algae and marine invertebrates. The physicochemical characteristics and potential bioactivities of fucoidan have attracted substantial interest in pharmaceutical industries in the past few decades. These polysaccharides are characterized by possessing sulfate ester groups that impart negatively charged surfaces, low/high molecular weight, and water solubility. In addition, various promising bioactivities have been reported, such as antitumor, immunomodulatory, and antiviral effects. Hence, the formulation of fucoidan has been investigated in the past few years in diverse pharmaceutical dosage forms to be able to reach their site of action effectively. Moreover, they can act as carriers for various drugs in value-added drug delivery systems. The current work highlights the attractive biopharmaceutical properties of fucoidan being formulated in oral, inhalable, topical, injectable, and other advanced formulations treating life-quality-affecting diseases. Therefore, the present work points out the current status of fucoidan pharmaceutical formulations for future research transferring their application from in vitro and in vivo studies to clinical application and market availability.

Application of injectable hydrogels in cancer immunotherapy

Immunotherapy is a revolutionary and promising approach to cancer treatment. However, traditional cancer immunotherapy often has the disadvantages of limited immune response rate, poor targeting, and low treatment index due to systemic administration. Hydrogels are drug carriers with many advantages. They can be loaded and transported with immunotherapeutic agents, chemical anticancer drugs, radiopharmaceuticals, photothermal agents, photosensitizers, and other therapeutic agents to achieve controlled release of drugs, extend the retention time of drugs, and thus successfully trigger anti-tumor effects and maintain long-term therapeutic effects after administration. This paper reviews recent advances in injectable hydrogel-based cancer immunotherapy, including immunotherapy alone, immunotherapy with combination chemotherapy, radiotherapy, phototherapy, and DNA hydrogel-based immunotherapy. Finally, we review the potential and limitations of injectable hydrogels in cancer immunotherapy.

One-Step Preparation of an Injectable Hydrogel Scaffold System Capable of Sequential Dual-Growth Factor Release to Maximize Bone Regeneration

Numerous growth factors are involved in the natural bone healing process, which is precisely controlled in a time- and concentration-dependent manner. Mimicking the secretion pattern of growth factors could be an effective means to maximize the bone regeneration effect. However, achieving the sequential delivery of various growth factors without the use of multiple materials or complex scaffold designs is challenging. Herein, an injectable poly(organophosphazene) hydrogel scaffold (IPS) encapsulating bone morphogenetic protein (BMP)-2 and TGFβ-1 (IPS_BT) is studied to mimic the sequential secretion of growth factors involved in natural bone healing. The IPS_BT system is designed to release TGFβ-1 slowly while retaining BMP-2 for a longer period of time. When IPS_BT is injected in vivo, the hydrogel is replaced by bone tissue. In addition, angiogenic (CD31 and alpha-smooth muscle actin (α-SMA)) and stemness (Nanog and SOX2) markers are highly upregulated in the early stages of bone regeneration. The IPS system developed here has promising applications in tissue engineering because 1) various amounts of the growth factors can be loaded in one step, 2) the release pattern of each growth factor can be controlled via differences in their molecular interactions, and 3) the injected IPS can be degraded and replaced with regenerated bone tissue.

Polymeric Nanocomposite Hydrogel Scaffolds in Craniofacial Bone Regeneration: A Comprehensive Review

Nanocomposite biomaterials combine a biopolymeric matrix structure with nanoscale fillers. These bioactive and easily resorbable nanocomposites have been broadly divided into three groups, namely natural, synthetic or composite, based on the polymeric origin. Preparing such nanocomposite structures in the form of hydrogels can create a three-dimensional natural hydrophilic atmosphere pivotal for cell survival and new tissue formation. Thus, hydrogel-based cell distribution and drug administration have evolved as possible options for bone tissue engineering and regeneration. In this context, nanogels or nanohydrogels, created by cross-linking three-dimensional polymer networks, either physically or chemically, with high biocompatibility and mechanical properties were introduced as promising drug delivery systems. The present review highlights the potential of hydrogels and nanopolymers in the field of craniofacial tissue engineering and bone regeneration.

A novel injectable hydrogel containing polyetheretherketone for bone regeneration in the craniofacial region

Polyetheretherketone (PEEK) is an organic material introduced as an alternative for titanium implants. Injectable hydrogels are the most promising approach for bone regeneration in the oral cavity to fill the defects with irregular shapes and contours conservatively. In the current study, injectable Aldehyde-cellulose nanocrystalline/silk fibroin (ADCNCs/SF) hydrogels containing PEEK were synthesized, and their bone regeneration capacity was evaluated. Structure, intermolecular interaction, and the reaction between the components were assessed in hydrogel structure. The cytocompatibility of the fabricated scaffolds was evaluated on human dental pulp stem cells (hDPSCs). Moreover, the osteoinduction capacity of ADCNCs/SF/PEEK hydrogels on hDPSCs was evaluated using Real-time PCR, Western blot, Alizarin red staining and ALP activity. Bone formation in critical-size defects in rats' cranial was assessed histologically and radiographically. The results confirmed the successful fabrication of the hydrogel and its osteogenic induction ability on hDPSCs. Furthermore, in in vivo phase, bone formation was significantly higher in ADCNCs/SF/PEEK group. Hence, the enhanced bone regeneration in response to PEEK-loaded hydrogels suggested its potential for regenerating bone loss in the craniofacial region, explicitly surrounding the dental implants.

Optimization of an Injectable Hydrogel Depot System for the Controlled Release of Retinal-Targeted Hybrid Nanoparticles

A drawback in the development of treatments that can reach the retina is the presence of barriers in the eye that restrain compounds from reaching the target. Intravitreal injections hold promise for retinal delivery, but the natural defenses in the vitreous can rapidly degrade or eliminate therapeutic molecules. Injectable hydrogel implants, which act as a reservoir, can allow for long-term drug delivery with a single injection into the eye, but still suffer due to the fast clearance of the released drugs when traversing the vitreous and random diffusion that leads to lower pharmaceutic efficacy. A combination with HA-covered nanoparticles, which can be released from the gel and more readily pass through the vitreous to increase the delivery of therapeutic agents to the retina, represents an advanced and elegant way to overcome some of the limitations in eye drug delivery. In this article, we developed hybrid PLGA-Dotap NPs that, due to their hyaluronic acid coating, can improve in vivo distribution throughout the vitreous and delivery to retinal cells. Moreover, a hydrogel implant was developed to act as a depot for the hybrid NPs to better control and slow their release. These results are a first step to improve the treatment of retinal diseases by protecting and transporting the therapeutic treatment across the vitreous and to improve treatment options by creating a depot system for long-term treatments.

Polysaccharides-Based Injectable Hydrogels: Preparation, Characteristics, and Biomedical Applications

Polysaccharides-based injectable hydrogels are a unique group of biodegradable and biocompatible materials that have shown great potential in the different biomedical fields. The biomolecules or cells can be simply blended with the hydrogel precursors with a high loading capacity by homogenous mixing. The different physical and chemical crosslinking approaches for preparing polysaccharide-based injectable hydrogels are reviewed. Additionally, the review highlights the recent work using polysaccharides-based injectable hydrogels as stimuli-responsive delivery vehicles for the controlled release of different therapeutic agents and viscoelastic matrix for cell encapsulation. Moreover, the application of polysaccharides-based injectable hydrogel in regenerative medicine as tissue scaffold and wound healing dressing is covered.

Loss of multipotency in adipose-derived stem cells after culture in temperature-responsive injectable polymer hydrogels

Adipose-derived stem cells (AdSCs), a type of mesenchymal stem cell, are expected to be applicable to regenerative medicine and cellular delivery systems. The maintenance of cell multipotency and control of the differentiation direction are important for these applications. However, the differentiation direction of these cells is widely believed to depend on the physical properties of their scaffold. In this study, we explored whether the multipotency of AdSCs, that is, their ability to differentiate into multiple cells, is maintained when they are removed from injectable polymer (IP) hydrogels with various degrees of cross-linking and induced to differentiate into osteoblasts and adipocytes. We confirmed that AdSCs cultured in IP hydrogels maintained an undifferentiated state. However, their differentiation into osteoblasts and adipocytes cannot be ensured; specifically, the multipotency of AdSCs may decrease when they are cultured in IP hydrogels. When cultured in an IP hydrogel with extreme softness and poor cell adhesion properties, the AdSCs remained in an undifferentiated state, but their multipotency was reduced. These results provide important insights into stem cell delivery systems using IP hydrogels.

Intraperitoneal administration of thermosensitive hydrogel Co-loaded with norcantharidin nanoparticles and oxaliplatin inhibits malignant ascites of hepatocellular carcinoma

Malignant ascites is a common complication of some advanced cancers. Although intraperitoneal (IP) administration of chemotherapy drugs is routinely used to treat cancerous ascites, conventional drugs have poor retention and therefore need to be administered frequently to maintain a sustained anti-tumor effect. In this study, a thermosensitive hydrogel composite loaded with norethindrone nanoparticles (NPs) and oxaliplatin (N/O/Hydrogel) was developed to inhibit ascites of hepatocellular carcinoma (HCC) through IP injection. N/O/Hydrogel induced apoptosis in the H22 cells in vitro, and significantly inhibited ascites formation, tumor cell proliferation and micro-angiogenesis in a mouse model of advanced HCC with ascites, and prolonged the survival of tumor-bearing mice. Histological examination of the major organs indicated that the hydrogel system is safe. Taken together, the N/O/Hydrogel system is a promising platform for in-situ chemotherapy of malignant ascites.

Polysaccharide-based hydrogels for drug delivery and wound management: a review

INTRODUCTION

Polysaccharide-based hydrogels (PBHs) offer several advantages over their synthetic counterparts. Their natural origin contributes to their nontoxicity, high biocompatibility, and in vivo biodegradability. Their properties can be tuned finely to obtain hydrogels with desired mechanical, structural, and chemical properties.

AREAS COVERED

Such versatile characteristics have potentiated the use of PBHs for the delivery of drugs, vaccines, protein and peptide therapeutics, genes, cells, probiotics, bacteriophages, and other therapeutic agents. Recent advances in hydrogel-based formulations such as nanogels, microgels, microneedles, hydrogel beads, nanocarrier-loaded hydrogels, and complexation hydrogels have enabled the precise delivery of a wide range of therapeutics. This review aims to give a holistic overview of hydrogels in the delivery of a variety of therapeutics through different routes.

EXPERT OPINION

PBHs have been used to enable the oral delivery of vaccines and other biologicals, thereby allowing self-administration of life-saving vaccines during public health emergencies. There is a lack of commercialized wound dressings for the treatment of chronic wounds. PBH-based wound dressings, especially those based on chitosan and loaded with actives and growth factors, have the potential to help in the long-term treatment of such wounds. Recent developments in the 3D printing of hydrogels can enable the quick and large-scale production of drug-loaded hydrogels.

Clay-Based Nanocomposite Hydrogels for Biomedical Applications: A Review

In recent decades, new and improved materials have been developed with a significant interest in three-dimensional (3D) scaffolds that can cope with the diverse needs of the expanding biomedical field and promote the required biological response in multiple applications. Due to their biocompatibility, ability to encapsulate and deliver drugs, and capacity to mimic the extracellular matrix (ECM), typical hydrogels have been extensively investigated in the biomedical and biotechnological fields. The major limitations of hydrogels include poor mechanical integrity and limited cell interaction, restricting their broad applicability. To overcome these limitations, an emerging approach, aimed at the generation of hybrid materials with synergistic effects, is focused on incorporating nanoparticles (NPs) within polymeric gels to achieve nanocomposites with tailored functionality and improved properties. This review focuses on the unique contributions of clay nanoparticles, regarding the recent developments of clay-based nanocomposite hydrogels, with an emphasis on biomedical applications.

Application of Nano-Inspired Scaffolds-Based Biopolymer Hydrogel for Bone and Periodontal Tissue Regeneration

This review’s objectives are to provide an overview of the various kinds of biopolymer hydrogels that are currently used for bone tissue and periodontal tissue regeneration, to list the advantages and disadvantages of using them, to assess how well they might be used for nanoscale fabrication and biofunctionalization, and to describe their production processes and processes for functionalization with active biomolecules. They are applied in conjunction with other materials (such as microparticles (MPs) and nanoparticles (NPs)) and other novel techniques to replicate physiological bone generation more faithfully. Enhancing the biocompatibility of hydrogels created from blends of natural and synthetic biopolymers can result in the creation of the best scaffold match to the extracellular matrix (ECM) for bone and periodontal tissue regeneration. Additionally, adding various nanoparticles can increase the scaffold hydrogel stability and provide a number of biological effects. In this review, the research study of polysaccharide hydrogel as a scaffold will be critical in creating valuable materials for effective bone tissue regeneration, with a future impact predicted in repairing bone defects.

Advanced injectable hydrogels for cartilage tissue engineering

The rapid development of tissue engineering makes it an effective strategy for repairing cartilage defects. The significant advantages of injectable hydrogels for cartilage injury include the properties of natural extracellular matrix (ECM), good biocompatibility, and strong plasticity to adapt to irregular cartilage defect surfaces. These inherent properties make injectable hydrogels a promising tool for cartilage tissue engineering. This paper reviews the research progress on advanced injectable hydrogels. The cross-linking method and structure of injectable hydrogels are thoroughly discussed. Furthermore, polymers, cells, and stimulators commonly used in the preparation of injectable hydrogels are thoroughly reviewed. Finally, we summarize the research progress of the latest advanced hydrogels for cartilage repair and the future challenges for injectable hydrogels.

Injectable Hybrid-Crosslinked Hydrogels as Fatigue-Resistant and Shape-Stable Skin Depots

Injectable hydrogels have gained considerable attention, but they are typically mechanically weak and subject to repeated physiological stresses in the body. Herein, we prepared polyurethane diacrylate (EPC-DA) hydrogels, which are injectable and can be photocrosslinked into fatigue-resistant implants. The mechanical properties can be tuned by changing photocrosslinking conditions, and the hybrid-crosslinked EPC-DA hydrogels exhibited high stability and sustained release properties. In contrast to common injectable hydrogels, EPC-DA hydrogels exhibited excellent antifatigue properties with >90% recovery during cyclic compression tests and showed shape stability after application of force and immersion in an aqueous buffer for 35 days. The EPC-DA hydrogel formed a shape-stable hydrogel depot in an ex vivo porcine skin model, with establishment of a temporary soft gel before in situ fixing by UV crosslinking. Hybrid crosslinking using injectable polymeric micelles or nanoparticles may be a general strategy for producing hydrogel implants resistant to physiological stresses.

Deciphering the focuses and trends in skin regeneration research through bibliometric analyses

Increasing attention to skin regeneration has rapidly broadened research on the topic. However, no bibliometric analysis of the field’s research trends has yet been conducted. In response to this research gap, this study analyzed the publication patterns and progress of skin regeneration research worldwide using a bibliometric analysis of 1,471 papers comprising 1,227 (83.4%) original articles and 244 (16.6%) reviews sourced from a Web of Science search. Publication distribution was analyzed by country/region, institution, journal, and author. The frequency of keywords was assessed to prepare a bibliometric map of the development trends in skin regeneration research. China and the United States were the most productive countries in the field: China had the greatest number of publications at 433 (29.4%) and the United States had the highest H-index ranking (59 with 15,373 citations or 31.9%). Author keywords were classified into four clusters: stem cell, biomaterial, tissue engineering, and wound dressing. “Stem cells,” “chitosan,” “tissue engineering,” and “wound dressings” were the most frequent keywords in each cluster; therefore, they reflected the field’s current focus areas. “Immunomodulation,” “aloe vera,” “extracellular vesicles,” “injectable hydrogel,” and “three-dimensional (3D) bioprinting” were relatively new keywords, indicating that biomaterials for skin regeneration and 3D bioprinting are promising research hotspots in the field. Moreover, clinical studies on new dressings and techniques to accelerate skin regeneration deserve more attention. By uncovering current and future research hotspots, this analysis offers insights that may be useful for both new and experienced scholars striving to expand research and innovation in the field of skin regeneration.