Multifunctional smart hydrogels: potential in tissue engineering and cancer therapy

Smart hydrogel-based trends in future tendon injury repair: A review

Despite advances in tissue engineering for tendon repair, rapid functional repair is still challenging due to its specificity and is prone to complications such as postoperative infections and tendon adhesions. Smart responsive hydrogels provide new ideas for tendon therapy with their flexibly designed three-dimensional cross-linked polymer networks that respond to specific stimuli. In recent years, a variety of smart-responsive hydrogels have been developed for the treatment of tendon disorders, showing great research promise and ability to address complex challenges. This article provides a comprehensive review of recent advances in the field of smart-responsive hydrogels for the treatment of tendon disorders, with a special focus on their response properties to different physical, chemical and biological stimuli. The multiple functional properties of these innovative materials are discussed in depth, including excellent biocompatibility and biodegradability, excellent mechanical properties, biomimetic structural design, convenient injectability, and unique self-healing capabilities. These properties enable the smart-responsive hydrogels to demonstrate significant advantages in solving difficult problems in the treatment of tendon disorders, such as precise drug delivery, tendon adhesion prevention and postoperative infection control. In addition, the article looks at the future prospects of smart-responsive hydrogels and analyses the challenges they may face in achieving widespread application.

Chitosan-based hydrogels in cancer therapy: Drug and gene delivery, stimuli-responsive carriers, phototherapy and immunotherapy

Nanotechnology has transformed the oncology sector by particularly targeting cancer cells and enhancing the efficacy of conventional therapies, not only improving efficacy of conventional therapeutics, but also reducing systemic toxicity. Environmentally friendly materials are the top choice for treating cancer. Chitosan, sourced from chitin, is widely used with its derivatives for the extensive synthesis or modification of nanostructures. Chitosan has been deployed to develop hydrogels, as 3D polymeric networks capable of water absorption with wide biomedical application. The chitosan hydrogels are biocompatible and biodegradable structures that can deliver drugs, genes or a combination of them in cancer therapy. Increased tumor ablation, reducing off-targeting feature and protection of genes against degradation are benefits of using chitosan hydrogels in cancer therapy. The efficacy of cancer immunotherapy can be improved by chitosan hydrogels to prevent emergence of immune evasion. In addition, chitosan hydrogels facilitate photothermal and photodynamic therapy for tumor suppression. Chitosan hydrogels can synergistically integrate chemotherapy, immunotherapy, and phototherapy in cancer treatment. Additionally, chitosan hydrogels that respond to stimuli, specifically thermo-sensitive hydrogels, have been developed for inhibiting tumors.

Methods to achieve tissue-mimetic physicochemical properties in hydrogels for regenerative medicine and tissue engineering

Hydrogels are water-swollen polymeric matrices with properties that are remarkably similar in function to the extracellular matrix. For example, the polymer matrix provides structural support and adhesion sites for cells in much of the same way as the fibers of the extracellular matrix. In addition, depending on the polymer used, bioactive sites on the polymer may provide signals to initiate certain cell behavior. However, despite their potential as biomaterials for tissue engineering and regenerative medicine applications, fabricating hydrogels that truly mimic the physicochemical properties of the extracellular matrix to physiologically-relevant values is a challenge. Recent efforts in the field have sought to improve the physicochemical properties of hydrogels using advanced materials science and engineering methods. In this review, we highlight some of the most promising methods, including crosslinking strategies and manufacturing approaches such as 3D bioprinting and granular hydrogels. We also provide a brief perspective on the future outlook of this field and how these methods may lead to the clinical translation of hydrogel biomaterials for tissue engineering and regenerative medicine applications.

Stimulus-Responsive Hydrogels for Targeted Cancer Therapy

Cancer is a highly heterogeneous disease and remains a global health challenge affecting millions of human lives worldwide. Despite advancements in conventional treatments like surgery, chemotherapy, and immunotherapy, the rise of multidrug resistance, tumor recurrence, and their severe side effects and the complex nature of the tumor microenvironment (TME) necessitates innovative therapeutic approaches. Recently, stimulus-responsive nanomedicines designed to target TME characteristics (e.g., pH alterations, redox conditions, enzyme secretion) have gained attention for their potential to enhance anticancer efficacy while minimizing the adverse effects of chemotherapeutics/bioactive compounds. Among the various nanocarriers, hydrogels are intriguing due to their high-water content, adjustable mechanical characteristics, and responsiveness to external and internal stimuli, making them promising candidates for cancer therapy. These properties make hydrogels an ideal nanocarrier for controlled drug release within the TME. This review comprehensively surveys the latest advancements in the area of stimulus-responsive hydrogels for cancer therapy, exploring various stimuli-responsive mechanisms, including biological (e.g., pH, redox), chemical (e.g., enzymes, glucose), and physical (e.g., temperature, light), as well as dual- or multi-stimuli responsiveness. Furthermore, this review addresses the current developments and challenges in hydrogels in cancer treatment. Our aim is to provide readers with a comprehensive understanding of stimulus-responsive hydrogels for cancer treatment, offering novel perspectives on their development for cancer therapy and other medical applications.

Modeling of Magnetic Scaffolds as Drug Delivery Platforms for Tissue Engineering and Cancer Therapy

Magnetic scaffolds (MagSs) are magneto-responsive devices obtained by the combination of traditional biomaterials (e.g., polymers, bioceramics, and bioglasses) and magnetic nanoparticles. This work analyzes the literature about MagSs used as drug delivery systems for tissue repair and cancer treatment. These devices can be used as innovative drugs and/or biomolecules delivery systems. Through the application of a static or dynamic stimulus, MagSs can trigger drug release in a controlled and remote way. However, most of MagSs used as drug delivery systems are not optimized and properly modeled, causing a local inhomogeneous distribution of the drug's concentration and burst release. Few physical-mathematical models have been presented to study and analyze different MagSs, with the lack of a systematic vision. In this work, we propose a modeling framework. We modeled the experimental data of drug release from different MagSs, under various magnetic field types, taken from the literature. The data were fitted to a modified Gompertz equation and to the Korsmeyer-Peppas model (KPM). The correlation coefficient (R2) and the root mean square error (RMSE) were the figures of merit used to evaluate the fitting quality. It has been found that the Gompertz model can fit most of the drug delivery cases, with an average RMSE below 0.01 and R2>0.9. This quantitative interpretation of existing experimental data can foster the design and use of MagSs for drug delivery applications.

Recent Research Progress on Polyamidoamine-Engineered Hydrogels for Biomedical Applications

Hydrogels are three-dimensional crosslinked functional materials with water-absorbing and swelling properties. Many hydrogels can store a variety of small functional molecules to structurally and functionally mimic the natural extracellular matrix; hence, they have been extensively studied for biomedical applications. Polyamidoamine (PAMAM) dendrimers have an ethylenediamine core and a large number of peripheral amino groups, which can be used to engineer various polymer hydrogels. In this review, an update on the progress of using PAMAM dendrimers for multifunctional hydrogel design was given. The synthesis of these hydrogels, which includes click chemistry reactions, aza-Michael addition, Schiff base reactions, amidation reactions, enzymatic reactions, and radical polymerization, together with research progress in terms of their application in the fields of drug delivery, tissue engineering, drug-free tumor therapy, and other related fields, was discussed in detail. Furthermore, the biomedical applications of PAMAM-engineered nano-hydrogels, which combine the advantages of dendrimers, hydrogels, and nanoparticles, were also summarized. This review will help researchers to design and develop more functional hydrogel materials based on PAMAM dendrimers.

Smart Hydrogel Swelling State Detection Based on a Power-Transfer Transduction Principle

Stimulus-responsive (smart) hydrogels are a promising sensing material for biomedical contexts due to their reversible swelling change in response to target analytes. The design of application-specific sensors that utilize this behavior requires the development of suitable transduction concepts. The presented study investigates a power-transfer-based readout approach that is sensitive to small volumetric changes of the smart hydrogel. The concept employs two thin film polyimide substrates with embedded conductive strip lines, which are shielded from each other except at the tip region, where the smart hydrogel is sandwiched in between. The hydrogel's volume change in response to a target analyte alters the distance and orientation of the thin films, affecting the amount of transferred power between the two transducer parts and, consequently, the measured sensor output voltage. With proper calibration, the output signal can be used to determine the swelling change of the hydrogel and, consequently, to quantify the stimulus. In proof-of-principle experiments with glucose- and pH-sensitive smart hydrogels, high sensitivity to small analyte concentration changes was found along with very good reproducibility and stability. The concept was tested with two exemplary hydrogels, but the transduction principle in general is independent of the specific hydrogel material, as long as it exhibits a stimulus-dependent volume change. The application vision of the presented research is to integrate in situ blood analyte monitoring capabilities into standard (micro)catheters. The developed sensor is designed to fit into a catheter without obstructing its normal use and, therefore, offers great potential for providing a universally applicable transducer platform for smart catheter-based sensing.

Advances and Trends of Photoresponsive Hydrogels for Bone Tissue Engineering

The development of static hydrogels as an optimal choice for bone tissue engineering (BTE) remains a difficult challenge primarily due to the intricate nature of bone healing processes, continuous physiological functions, and pathological changes. Hence, there is an urgent need to exploit smart hydrogels with programmable properties that can effectively enhance bone regeneration. Increasing evidence suggests that photoresponsive hydrogels are promising bioscaffolds for BTE due to their advantages such as controlled drug release, cell fate modulation, and the photothermal effect. Here, we review the current advances in photoresponsive hydrogels. The mechanism of photoresponsiveness and its advanced applications in bone repair are also elucidated. Future research would focus on the development of more efficient, safer, and smarter photoresponsive hydrogels for BTE. This review is aimed at offering comprehensive guidance on the trends of photoresponsive hydrogels and shedding light on their potential clinical application in BTE.

Smart Biomaterials in Biomedical Applications: Current Advances and Possible Future Directions

Smart biomaterials with the capacity to alter their properties in response to an outside stimulus or from within the environment around them have picked up significant attention in the biomedical community. This is primarily due to the interest in their biomedical applications that may be anticipated from them in a considerable number of dynamic structures and devices. Shape-memory materials are some of these materials that have been exclusively used for these applications. They exhibit unique structural reconfiguration features they adapt as per the provided environmental conditions and can be designed for their enhanced biocompatibility. Numerous research initiatives have focused on these smart biocompatible materials over the last few decades to enhance their biomedical applications. Shape-memory materials play a significant role in this regard to meet new surgical and medical devices' requirements for special features and utility cases. Because of the favorable design variety, different biomedical shape-memory materials can be developed by modifying their chemical and physical behaviors to accommodate the desired requirements. In this review, recent advances and characteristics of smart biomaterials for biomedical applications are described. The authors also discuss about their clinical translations in tissue engineering, drug delivery, and medical devices.

Highly deformable and strongly magnetic semi-interpenetrating hydrogels based on alginate or cellulose

The effective implementation of many of the applications of magnetic hydrogels requires the development of innovative systems capable of withstanding a substantial load of magnetic particles to ensure exceptional responsiveness, without compromising their reliability and stability. To address this challenge, double-network hydrogels have emerged as a promising foundation, thanks to their extraordinary mechanical deformability and toughness. Here, we report a semi-interpenetrating polymer networks (SIPNs) approach to create diverse magnetic SIPNs hydrogels based on alginate or cellulose, exhibiting remarkable deformability under certain stresses. Achieving strong responsiveness to magnetic fields is a key objective, and this characteristic is realized by the incorporation of highly magnetic iron microparticles at moderately large concentrations into the polymer network. Remarkably, the SIPNs hydrogels developed in this research accommodate high loadings of magnetic particles without significantly compromising their physical properties. This feature is essential for their use in applications that demand robust responsiveness to applied magnetic fields and overall stability, such as a hydrogel luminescent oxygen sensor controlled by magnetic fields that we designed and tested as proof-of-concept. These findings underscore the potential and versatility of magnetic SIPNs hydrogels based on carbohydrate biopolymers as fundamental components in driving the progress of advanced hydrogels for diverse practical implementations.

Quince seed mucilage/β-cyclodextrin/Mmt-Na+-co-poly (methacrylate) based pH-sensitive polymeric carriers for controlled delivery of Capecitabine

In current work, quince seed mucilage and β-Cyclodextrin based pH regulated hydrogels were developed using aqueous free radical polymerization to sustain Capecitabine release patterns and to overcome its drawbacks, such as high dose frequency, short half-life, and low bioavailability. Developed networks were subjected to thermal analysis, Fourier transforms infrared spectroscopy, powder x-ray diffraction, elemental analysis, scanning electron microscopy, equilibrium swelling, and in-vitro release investigations to assess the network system's stability, complexation, morphology, and pH responsiveness. Thermally stable pH-responsive cross-linked networks were formed. Nanocomposite hydrogels were prepared by incorporating Capecitabine-containing clay into the swollen hydrogels. All the formulations exhibited equilibrium swelling ranging from 67.98 % to 92.98 % at pH 7.4. Optimum Capecitabine loading (88.17 %) was noted in the case of hydrogels, while it was 74.27 % in nanocomposite hydrogels. Excellent gel content (65.88 %-93.56 %) was noticed among developed formulations. Elemental analysis ensured the successful incorporation of Capecitabine. Nanocomposite hydrogels released 80.02 % longer than hydrogels after 30 h. NC hydrogels had higher t1/2 (10.57 h), AUC (121.52 μg.h/ml), and MRT (18.95 h) than hydrogels in oral pharmacokinetics. These findings imply that the pH-responsive carrier system may improve Capecitabine efficacy and reduce dosing frequency in cancer therapy. Toxicity profiling proved the system's safety, non-toxicity, and biocompatibility.

The microspheres/hydrogels scaffolds based on the proteins, nucleic acids, or polysaccharides composite as carriers for tissue repair: A review

There are many studies on specific macromolecules and their contributions to tissue repair. Macromolecules have supporting and protective effects in organisms and can help regrow, reshape, and promote self-repair and regeneration of damaged tissues. Macromolecules, such as proteins, nucleic acids, and polysaccharides, can be constructed into hydrogels for the preparation of slow-release drug agents, carriers for cell culture, and platforms for gene delivery. Hydrogels and microspheres are fabricated by chemical crosslinking or mixed co-deposition often used as scaffolds, drug carriers, or cell culture matrix, provide proper mechanical support and nutrient delivery, a well-conditioned environment that to promote the regeneration and repair of damaged tissues. This review provides a comprehensive overview of recent developments in the construction of macromolecules into hydrogels and microspheres based on the proteins, nucleic acids, polysaccharides and other polymer and their application in tissue repair. We then discuss the latest research trends regarding the advantages and disadvantages of these composites in repair tissue. Further, we examine the applications of microspheres/hydrogels in different tissue repairs, such as skin tissue, cartilage, tumor tissue, synovial, nerve tissue, and cardiac repair. The review closes by highlighting the challenges and prospects of microspheres/hydrogels composites.

A Review of Research Progress on the Performance of Intelligent Polymer Gel

Intelligent polymer gel, as a popular polymer material, has been attracting much attention for its application. An intelligent polymer gel will make corresponding changes to adapt to the environment after receiving stimuli; therefore, an intelligent polymer gel can play its role in many fields. With the research on intelligent polymer gels, there is great potential for applications in the fields of drug engineering, molecular devices, and biomedicine in particular. The strength and responsiveness of the gels can be improved under different configurations in different technologies to meet the needs in these fields. There is no discussion on the application of intelligent polymer gels in these fields; therefore, this paper reviews the research progress of intelligent polymer gel, describes the important research of some intelligent polymer gel, summarizes the research progress and current situation of intelligent polymer gel in the environment of external stimulation, and discusses the performance and future development direction of intelligent polymer gel.

2-Hydroxyethyl Methacrylate/Gelatin/Alginate Scaffolds Reinforced with Nano TiO2 as a Promising Curcumin Release Platform

The idea of this study was to create a new scaffolding system based on 2-hydroxyethyl methacrylate, gelatin, and alginate that contains titanium(IV) oxide nanoparticles as a platform for the controlled release of the bioactive agent curcumin. The innovative strategy to develop hybrid scaffolds was the modified porogenation method. The effect of the scaffold composition on the chemical, morphology, porosity, mechanical, hydrophilicity, swelling, degradation, biocompatibility, loading, and release features of hybrid scaffolds was evaluated. A porous structure with interconnected pores in the range of 52.33–65.76%, favorable swelling capacity, fully hydrophilic surfaces, degradability to 45% for 6 months, curcumin loading efficiency above 96%, and favorable controlled release profiles were obtained. By applying four kinetic models of release, valuable parameters were obtained for the curcumin/PHEMA/gelatin/alginate/TiO2 release platform. Cytotoxicity test results depend on the composition of the scaffolds and showed satisfactory cell growth with visible cell accumulation on the hybrid surfaces. The constructed hybrid scaffolds have suitable high-performance properties, suggesting potential for further in vivo and clinical studies.

Chitosan and Pectin Hydrogels for Tissue Engineering and In Vitro Modeling

Hydrogels are fascinating biomaterials that can act as a support for cells, i.e., a scaffold, in which they can organize themselves spatially in a similar way to what occurs in vivo. Hydrogel use is therefore essential for the development of 3D systems and allows to recreate the cellular microenvironment in physiological and pathological conditions. This makes them ideal candidates for biological tissue analogues for application in the field of both tissue engineering and 3D in vitro models, as they have the ability to closely mimic the extracellular matrix (ECM) of a specific organ or tissue. Polysaccharide-based hydrogels, because of their remarkable biocompatibility related to their polymeric constituents, have the ability to interact beneficially with the cellular components. Although the growing interest in the use of polysaccharide-based hydrogels in the biomedical field is evidenced by a conspicuous number of reviews on the topic, none of them have focused on the combined use of two important polysaccharides, chitosan and pectin. Therefore, the present review will discuss the biomedical applications of polysaccharide-based hydrogels containing the two aforementioned natural polymers, chitosan and pectin, in the fields of tissue engineering and 3D in vitro modeling.

The recent advancement in the PLGA-based thermo-sensitive hydrogel for smart drug delivery

To date, hydrogels have opened new prospects for potential applications for drug delivery. The thermo-sensitive hydrogels have the great potential to provide more effective and controllable release of therapeutic/bioactive agents in response to changes in temperature. PLGA is a safe FDA-approved copolymer with good biocompatibility and biodegradability. Recently, PLGA-based formulation have attracted a lot of interest for thermo-sensitive hydrogels. Thermo-sensitive PLGA-based hydrogels provide the delivery system with good spatial and temporal control, and have been widely applied in drug delivery. This review is focused on the recent progression of the thermo-sensitive and biodegradable PLGA-based hydrogels that have been reported for smart drug delivery to the different organs. Eventually, future perspectives and challenges of thermo-sensitive PLGA-based hydrogels are discussed briefly.

Manuka Honey/2-Hydroxyethyl Methacrylate/Gelatin Hybrid Hydrogel Scaffolds for Potential Tissue Regeneration

Scaffolding biomaterials are gaining great importance due to their beneficial properties for medical purposes. Targeted biomaterial engineering strategies through the synergy of different material types can be applied to design hybrid scaffolding biomaterials with advantageous properties for biomedical applications. In our research, a novel combination of the bioactive agent Manuka honey (MHo) with 2-hydroxyethyl methacrylate/gelatin (HG) hydrogel scaffolds was created as an efficient bioactive platform for biomedical applications. The effects of Manuka honey content on structural characteristics, porosity, swelling performance, in vitro degradation, and in vitro biocompatibility (fibroblast and keratinocyte cell lines) of hybrid hydrogel scaffolds were studied using Fourier transform infrared spectroscopy, the gravimetric method, and in vitro MTT biocompatibility assays. The engineered hybrid hydrogel scaffolds show advantageous properties, including porosity in the range of 71.25% to 90.09%, specific pH- and temperature-dependent swelling performance, and convenient absorption capacity. In vitro degradation studies showed scaffold degradability ranging from 6.27% to 27.18% for four weeks. In vitro biocompatibility assays on healthy human fibroblast (MRC5 cells) and keratinocyte (HaCaT cells) cell lines by MTT tests showed that cell viability depends on the Manuka honey content loaded in the HG hydrogel scaffolds. A sample containing the highest Manuka honey content (30%) exhibited the best biocompatible properties. The obtained results reveal that the synergy of the bioactive agent, Manuka honey, with 2-hydroxyethyl methacrylate/gelatin as hybrid hydrogel scaffolds has potential for biomedical purposes. By tuning the Manuka honey content in HG hydrogel scaffolds advantageous properties of hybrid scaffolds can be achieved for biomedical applications.

Light responsive hydrogels for controlled drug delivery

Light is an easy acquired, effective and non-invasive external stimulus with great flexibility and focusability. Thus, light responsive hydrogels are of particular interests to researchers in developing accurate and controlled drug delivery systems. Light responsive hydrogels are obtained by incorporating photosensitive moieties into their polymeric structures. Drug release can be realized through three major mechanisms: photoisomerization, photochemical reaction and photothermal reaction. Recent advances in material science have resulted in great development of photosensitizers, such as rare metal nanostructures and black phosphorus nanoparticles, in order to respond to a variety of light sources. Hydrogels incorporated with photosensitizers are crucial for clinical applications, and the use of ultraviolet and near-infrared light as well as up-conversion nanoparticles has greatly increased the therapeutic effects. Existing light responsive drug delivery systems have been utilized in delivering drugs, proteins and genes for chemotherapy, immunotherapy, photodynamic therapy, gene therapy, wound healing and other applications. Principles associated with site-specific targeting, metabolism, and toxicity are used to optimize efficacy and safety, and to improve patient compliance and convenience. In view of the importance of this field, we review current development, challenges and future perspectives of light responsive hydrogels for controlled drug delivery.

Advancing intestinal organoid technology to decipher nano-intestine interactions and treat intestinal disease

With research burgeoning in nanoscience and nanotechnology, there is an urgent need to develop new biological models that can simulate native structure, function, and genetic properties of tissues to evaluate the adverse or beneficial effects of nanomaterials on a host. Among the current biological models, three-dimensional (3D) organoids have developed as powerful tools in the study of nanomaterial-biology (nano-bio) interactions, since these models can overcome many of the limitations of cell and animal models. A deep understanding of organoid techniques will facilitate the development of more efficient nanomedicines and further the fields of tissue engineering and personalized medicine. Herein, we summarize the recent progress in intestinal organoids culture systems with a focus on our understanding of the nature and influencing factors of intestinal organoid growth. We also discuss biomimetic extracellular matrices (ECMs) coupled with nanotechnology. In particular, we analyze the application prospects for intestinal organoids in investigating nano-intestine interactions. By integrating nanotechnology and organoid technology, this recently developed model will fill the gaps left due to the deficiencies of traditional cell and animal models, thus accelerating both our understanding of intestine-related nanotoxicity and the development of nanomedicines.

Recent Advances in Biodegradable Polymers and Their Biological Applications: A Brief Review

The rising significance of the field of biopolymers has driven the rapid progress of this distinctive class of polymeric materials in the past decades. Biodegradable polymers have acquired much attention because they play an essential role in humans' lives due to their specific tunable electrical conductivity and biodegradability characteristics, making them fascinating in many applications. Herein, we debated the recent progress in developing biodegradable polymers and their applications. Initially, we introduce the basics of conducting and biodegradable polymers, trailed by debates about the effective strategies currently used to develop biopolymers. Special importance will focus on the uses of biodegradable polymers in drug delivery and tissue engineering, as well as wound healing, demonstrating the recent findings, and uses of several biodegradable polymers in modern biological uses. In this review, we have provided comprehensive viewpoints on the latest progress of the challenges and future prospects involving biodegradable polymers' advancement and commercial applications.

Prodrug and Glucose Oxidase Coloaded Photodynamic Hydrogels for Combinational Therapy of Melanoma

With the advantages of high safety and selectivity, photodynamic therapy (PDT) has been widely used for cancer treatments, while the anticancer efficacy is often limited because of its relying on oxygen concentrations. Therefore, sole PDT fails to achieve the desired therapeutic effect for hypoxic tumors. To address this issue, we herein report the construction of prodrug and glucose oxidase (GOx) coloaded alginate (ALG) hydrogels for PDT-combined chemotherapy of melanoma. The hydrogels are in situ formed in tumor sites after injection of ALG solution containing semiconducting polymer nanoparticles, hypoxia-responsive prodrug tirapazamine (TPZ), and GOx, which is based on chelation of ALG by endogenous Ca²⁺. Due to the presence of semiconducting polymer nanoparticles acting as photosensitizers, the hydrogels mediate PDT to produce singlet oxygen (¹O₂) for directly killing tumor cells, in which oxygen is consumed to create a more hypoxic tumor microenvironment. Moreover, the loaded GOx within hydrogels can deplete oxygen to further aggravate tumor hypoxia. As such, TPZ is effectively activated by hypoxia to cause cancer cell death via chemotherapy. Thus, the hydrogels with laser irradiation achieve a combinational action of PDT with chemotherapy to almost completely eradicate tumors, leading to a much higher therapeutic efficacy relative to sole PDT. This study will provide a promising injectable hydrogel platform for effective treatments of cancer.

Advancements in the Use of Hydrogels for Regenerative Medicine: Properties and Biomedical Applications

Due to their particular water absorption capacity, hydrogels are the most widely used scaffolds in biomedical studies to regenerate damaged tissue. Hydrogels can be used in tissue engineering to design scaffolds for three-dimensional cell culture, providing a novel alternative to the traditional two-dimensional cell culture as hydrogels have a three-dimensional biomimetic structure. This material property is crucial in regenerative medicine, especially for the nervous system, since it is a highly complex and delicate structure. Hydrogels can move quickly within the human body without physically disturbing the environment and possess essential biocompatible properties, as well as the ability to form a mimetic scaffold in situ. Therefore, hydrogels are perfect candidates for biomedical applications. Hydrogels represent a potential alternative to regenerating tissue lost after removing a brain tumor and/or brain injuries. This reason presents them as an exciting alternative to highly complex human physiological problems, such as injuries to the central nervous system and neurodegenerative disease.

In Vitro and In Vivo Biocompatible and Controlled Resveratrol Release Performances of HEMA/Alginate and HEMA/Gelatin IPN Hydrogel Scaffolds

Scaffold hydrogel biomaterials designed to have advantageous biofunctional properties, which can be applied for controlled bioactive agent release, represent an important concept in biomedical tissue engineering. Our goal was to create scaffolding materials that mimic living tissue for biomedical utilization. In this study, two novel series of interpenetrating hydrogel networks (IPNs) based on 2-hydroxyethyl methacrylate/gelatin and 2-hydroxyethyl methacrylate/alginate were crosslinked using N-ethyl-N'-(3-dimethyl aminopropyl)carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS). Characterization included examining the effects of crosslinker type and concentration on structure, morphological and mechanical properties, in vitro swelling, hydrophilicity as well as on the in vitro cell viability (fibroblast cells) and in vivo (Caenorhabditis elegans) interactions of novel biomaterials. The engineered IPN hydrogel scaffolds show an interconnected pore morphology and porosity range of 62.36 to 85.20%, favorable in vitro swelling capacity, full hydrophilicity, and Young's modulus values in the range of 1.40 to 7.50 MPa. In vitro assay on healthy human fibroblast (MRC5 cells) by MTT test and in vivo (Caenorhabditis elegans) survival assays show the advantageous biocompatible properties of novel IPN hydrogel scaffolds. Furthermore, in vitro controlled release study of the therapeutic agent resveratrol showed that these novel scaffolding systems are suitable controlled release platforms. The results revealed that the use of EDC and the combination of EDC/NHS crosslinkers can be applied to prepare and tune the properties of the IPN 2-hydroxyethyl methacrylate/alginate and 2-hydroxyethyl methacrylate/gelatin hydrogel scaffolds series, which have shown great potential for biomedical engineering applications.

Therapeutic application of hydrogels for bone-related diseases

Bone-related diseases caused by trauma, infection, and aging affect people’s health and quality of life. The prevalence of bone-related diseases has been increasing yearly in recent years. Mild bone diseases can still be treated with conservative drugs and can be cured confidently. However, serious bone injuries caused by large-scale trauma, fractures, bone tumors, and other diseases are challenging to heal on their own. Open surgery must be used for intervention. The treatment method also faces the problems of a long cycle, high cost, and serious side effects. Studies have found that hydrogels have attracted much attention due to their good biocompatibility and biodegradability and show great potential in treating bone-related diseases. This paper mainly introduces the properties and preparation methods of hydrogels, reviews the application of hydrogels in bone-related diseases (including bone defects, bone fracture, cartilage injuries, and osteosarcoma) in recent years. We also put forward suggestions according to the current development status, pointing out a new direction for developing high-performance hydrogels more suitable for bone-related diseases.

Bilayer Hydrogels for Wound Dressing and Tissue Engineering

A large number of different skin diseases such as hits, acute, and chronic wounds dictate the search for alternative and effective treatment options. The wound healing process requires a complex approach, the key step of which is the choice of a dressing with controlled properties. Hydrogel-based scaffolds can serve as a unique class of wound dressings. Presented on the commercial market, hydrogel wound dressings are not found among proposals for specific cases and have a number of disadvantages—toxicity, allergenicity, and mechanical instability. Bilayer dressings are attracting great attention, which can be combined with multifunctional properties, high criteria for an ideal wound dressing (antimicrobial properties, adhesion and hemostasis, anti-inflammatory and antioxidant effects), drug delivery, self-healing, stimulus manifestation, and conductivity, depending on the preparation and purpose. In addition, advances in stem cell biology and biomaterials have enabled the design of hydrogel materials for skin tissue engineering. To improve the heterogeneity of the cell environment, it is possible to use two-layer functional gradient hydrogels. This review summarizes the methods and application advantages of bilayer dressings in wound treatment and skin tissue regeneration. Bilayered hydrogels based on natural as well as synthetic polymers are presented. The results of the in vitro and in vivo experiments and drug release are also discussed.

Recent Advances of Stimuli-Responsive Polysaccharide Hydrogels in Delivery Systems: A Review

Hydrogels obtained from natural polymers have received widespread attention for their excellent biocompatible property, nontoxicity, easy gelation, and functionalization. Polysaccharides can regulate the gut microbiota and improve the intestinal microenvironment, thus exerting the healthy effect of intestinal immunity. In an active substance delivery system, the extent and speed of the substance reaching its target are highly dependent on the carrier. Thus, the smart active substance delivery systems are gradually increasing. The smart polysaccharide-hydrogels possess the ability in response to external stimuli through changing their volume phase and structure, which are applied in various fields. Natural polysaccharide-based hydrogels possess excellent characteristics of environmental friendliness, good biocompatibility, and abundant sources. According to the response type, natural polysaccharide-based hydrogels are usually divided into stimulus-responsive hydrogels, including internal response (pH, temperature, enzyme, redox) and external response (light, electricity, magnetism) hydrogels. The delivery system based on polysaccharides can exert their effects in the gastrointestinal tract. At the same time, polysaccharides may also take part in regulating the brain signals through the microbiota-gut-brain axis. Therefore, natural polysaccharide-hydrogels are considered as promising biomaterials, which can be designed as delivery systems for regulating the gut-brain axis. This article reviews the research advance of stimulus-responsive hydrogels, which focus on the types, response characteristics, and applications for polysaccharide-based smart hydrogels as delivery systems.

Dendrobium officinale Enzyme Changing the Structure and Behaviors of Chitosan/γ-poly(glutamic acid) Hydrogel for Potential Skin Care

Hydrogels have been widespreadly used in various fields. But weak toughness has limited their further applications. In this study, Dendrobium officinale enzyme (DOE) was explored to improve chitosan/γ-poly(glutamic acid) (CS/γ-PGA) hydrogel in the structure and properties. The results indicated that DOE with various sizes of ingredients can make multiple noncovalent crosslinks with the skeleton network of CS/γ-PGA, significantly changing the self-assembly of CS/γ-PGA/DOE hydrogel to form regular protuberance nanostructures, which exhibits stronger toughness and better behaviors for skin care. Particularly, 4% DOE enhanced the toughness of CS/γ-PGA/DOE hydrogel, increasing it by 116%. Meanwhile, water absorption, antioxygenation, antibacterial behavior and air permeability were increased by 39%, 97%, 27% and 52%.

Criteria for the design of tissue-mimicking phantoms for the standardization of biophotonic instrumentation

A lack of accepted standards and standardized phantoms suitable for the technical validation of biophotonic instrumentation hinders the reliability and reproducibility of its experimental outputs. In this Perspective, we discuss general criteria for the design of tissue-mimicking biophotonic phantoms, and use these criteria and state-of-the-art developments to critically review the literature on phantom materials and on the fabrication of phantoms. By focusing on representative examples of standardization in diffuse optical imaging and spectroscopy, fluorescence-guided surgery and photoacoustic imaging, we identify unmet needs in the development of phantoms and a set of criteria (leveraging characterization, collaboration, communication and commitment) for the standardization of biophotonic instrumentation.

Cutting-Edge Progress in Stimuli-Responsive Bioadhesives: From Synthesis to Clinical Applications

With the advent of "intelligent" materials, the design of smart bioadhesives responding to chemical, physical, or biological stimuli has been widely developed in biomedical applications to minimize the risk of wounds reopening, chronic pain, and inflammation. Intelligent bioadhesives are free-flowing liquid solutions passing through a phase shift in the physiological environment due to stimuli such as light, temperature, pH, and electric field. They possess great merits, such as ease to access and the ability to sustained release as well as the spatial transfer of a biomolecule with reduced side effects. Tissue engineering, wound healing, drug delivery, regenerative biomedicine, cancer therapy, and other fields have benefited from smart bioadhesives. Recently, many disciplinary attempts have been performed to promote the functionality of smart bioadhesives and discover innovative compositions. However, according to our knowledge, the development of multifunctional bioadhesives for various biomedical applications has not been adequately explored. This review aims to summarize the most recent cutting-edge strategies (years 2015-2021) developed for stimuli-sensitive bioadhesives responding to external stimuli. We first focus on five primary categories of stimuli-responsive bioadhesive systems (pH, thermal, light, electric field, and biomolecules), their properties, and limitations. Following the introduction of principal criteria for smart bioadhesives, their performances are discussed, and certain smart polymeric materials employed in their creation in 2015 are studied. Finally, advantages, disadvantages, and future directions regarding smart bioadhesives for biomedical applications are surveyed.

Bio-Hybrid Hydrogels Incorporated into a System of Salicylic Acid-pH/Thermosensitive Nanocarriers Intended for Cutaneous Wound-Healing Processes

In this paper, the preparation method of bio-hybrid hydrogels incorporated into a system of salicylic acid-pH/thermosensitive nanocarriers to speed up the wound-healing process was developed. This combination creates a dual drug delivery system, which releases the model hydrophobic active substance-salicylic acid-in a gradual and controlled manner for an extended time. Our research team has determined the various properties of bio-hybrid hydrogels based on their physicochemical (swelling degree, and degradation), structural (FT-IR), morphological (SEM), and mechanical (elongation tests) traits. Moreover, empty pH/thermosensitive nanocarriers and their salicylic acid-containing systems were characterized using the following methods: DLS, TG/DTG, and DSC. Additionally, salicylic acid release profiles directly from thermosensitive nanocarriers were compared to the bio-hybrid matrix. These studies were conducted in PBS (pH = 7.4) for 7 days using the USP4 method. To evaluate the antibacterial properties of the obtained materials, the inhibition of growth of Staphylococcus aureus, Escherichia coli, Candida albicans, and Aspergillus niger-as the main microorganisms responsible for human infections-were tested. The obtained results indicated that the pH/thermosensitive nanocarrier-salicylic acid system and bio-hybrid hydrogels are characterized by antibacterial activity against both S. aureus and E. coli.

Hybrid in situ- forming injectable hydrogels for local cancer therapy

Injectable in situ forming hydrogels are amongst the efficient local drug delivery systems for cancer therapy. Providing a 3D hydrogel network within the target tissue capable of sustained release of the chemotherapeutics made them attractive candidates for increasing the therapeutic index. Remarkable swelling properties, mechanical strength, biocompatibility, wide composition variety and tunable polymeric moieties have led to preparation of injectable hydrogels which also could be used as cavity adaptive chemotherapeutic-loaded implants to prevent post -surgical cancer recurrence. Implementation of various polymers, nanoparticles, peptide and proteins and different crosslinking chemistry facilitated the fabrication of hybrid hydrogels with favorable characteristics such as stimuli sensitive platforms or multifunctional systems. In the current review, we focused on design and fabrication strategies of injectable in situ forming hydrogels and summarized recent hybrid hydrogels used for local cancer therapy.

Tumor redox microenvironment modulating composite hydrogels for enhanced sonodynamic therapy of colorectal cancer

Effective treatment of colorectal cancer is important to improve the quality of life for patients, which however remains a great challenge in the clinic. Herein, we report the construction of...

Self-healing polysaccharide-based injectable hydrogels with antibacterial activity for wound healing

Because the wound is difficult to heal, repeated bacterial infection will lead to complex clinical problems. Therefore, it is necessary to find an effective method to strengthen the healing process and resist bacterial infection. Hydrogels have many advantages, such as injectability and self-healing under physiological conditions, so they have been widely studied in recent years. Hydrogels can keep the wound moist and promote the wound healing. In addition, the growth of bacteria can be obviously inhibited by hydrogels themself or by doping some antibacterial active substances. Based on this, herein, this review highlighted the preparation and properties of different polysaccharide-based injectable hydrogels, and discuss their biological applications in antibacterial therapy for wound healing in recent years.

A Transparent, Highly Stretchable, Solvent-Resistant, Recyclable Multifunctional Ionogel with Underwater Self-Healing and Adhesion for Reliable Strain Sensors

Ionogels have gained increasing attentions as a flexible conductive material. However, it remains a big challenge to integrate multiple functions into one gel that can be widely applied in various complex scenes. Herein, a kind of multifunctional ionogels with a combination of desirable properties, including transparency, high stretchability, solvent and temperature resistance, recyclability, high conductivity, underwater self-healing ability, and underwater adhesiveness is reported. The ionogels are prepared via one-step photoinitiated polymerization of 2,2,2-trifluoroethyl acrylate and acrylamide in a hydrophobic ionic liquid. The abundant noncovalent interactions including hydrogen bonding and ion-dipole interactions endow the ionogels with excellent mechanical strength, resilience, and rapid self-healing capability at room temperature, while the fluorine-rich polymeric matrix brings in high tolerance against water and various organic solvents, as well as tough underwater adhesion on different substrates. Wearable strain sensors based on the ionogels can sensitively detect and differentiate large body motions, such as bending of limbs, walking and jumping, as well as subtle muscle movements, such as pronunciation and pulse. It is believed that the designed ionogels will show great promises in wearable devices and ionotronics.

Anisotropic Silver Nanoparticles Gel Exhibits Antibacterial Action and Reduced Scar Formation on Wounds Contaminated with Methicillin-Resistant Staphylococcus pseudintermedius (MRSP) in a Mice Model

Simple Summary

Wound infection in animals with antimicrobial resistant bacteria, especially Staphylococcus pseudintermedius, plays an important role in the delay of wound healing. In this work, the antimicrobial and wound healing activities of gels containing anisotropic AgNPs were evaluated on wounds contaminated with Methicillin-resistant Staphylococcus pseudintermedius in a mice model. The results show that anisotropic AgNPs gel is effective in eliminating bacteria and preventing pus formation. Furthermore, anisotropic AgNPs gel exhibits improved collagen alignment that supports scar disappearance.

Abstract

Staphylococcus pseudintermedius (S. pseudintermedius) infected wounds can cause seriously delayed wound healing processes in animals. Antimicrobial agents that have antimicrobial and wound healing efficacy have become an essential tool for overcoming this problem. In our previous study, anisotropic AgNPs have been reported to have antimicrobial efficiency against animal and human pathogens, and could be suitable as antimicrobial agents for infected wounds. Here, antimicrobial and wound healing activities of anisotropic AgNPs gels were assessed in vivo. BALB/cAJcl mice wounds were infected by Methicillin-resistant Staphylococcus pseudintermedius (MRSP). Then, antibacterial and wound healing activities were evaluated by bacterial cell count, wound contraction, digital capture, and histology. The results show that anisotropic AgNPs gels could eliminate all bacterial cell infected wounds within 7 days, the same as povidone iodine. Wound healing activity was evaluated by wound contraction (%). The results showed 100% wound contraction in groups treated with anisotropic AgNPs gels within 14 days that was not significantly different from povidone iodine and control gel without AgNPs. However, the digital capture of wounds on day 4 showed that anisotropic AgNPs gel prevented pus formation and reduced scar appearance within 21 days. The histology results exhibit improved collagen fiber alignment that supports scar disappearance. In conclusion, these results indicate that anisotropic AgNPs gels are suitable for treating infected wounds. The gel is effective in eliminating bacteria that supports the natural process of wound repair and also causes reduced scar formation.

Novel Chitosan-Silica Hybrid Hydrogels for Cell Encapsulation and Drug Delivery

Hydrogels constructed from naturally derived polymers provide an aqueous environment that encourages cell growth, however, mechanical properties are poor and degradation can be difficult to predict. Whilst, synthetic hydrogels exhibit some improved mechanical properties, these materials lack biochemical cues for cells growing and have limited biodegradation. To produce hydrogels that support 3D cell cultures to form tissue mimics, materials must exhibit appropriate biological and mechanical properties. In this study, novel organic-inorganic hybrid hydrogels based on chitosan and silica were prepared using the sol-gel technique. The chemical, physical and biological properties of the hydrogels were assessed. Statistical analysis was performed using One-Way ANOVAs and independent-sample t-tests. Fourier transform infrared spectroscopy showed characteristic absorption bands including amide II, Si-O and Si-O-Si confirming formation of hybrid networks. Oscillatory rheometry was used to characterise the sol to gel transition and viscoelastic behaviour of hydrogels. Furthermore, in vitro degradation revealed both chitosan and silica were released over 21 days. The hydrogels exhibited high loading efficiency as total protein loading was released in a week. There were significant differences between TC₂G and C₂G at all-time points (p < 0.05). The viability of osteoblasts seeded on, and encapsulated within, the hydrogels was >70% over 168 h culture and antimicrobial activity was demonstrated against Pseudomonas aeruginosa and Enterococcus faecalis. The hydrogels developed here offer alternatives for biopolymer hydrogels for biomedical use, including for application in drug/cell delivery and for bone tissue engineering.

Dual-Crosslinked Dynamic Hydrogel Incorporating {Mo154 } with pH and NIR Responsiveness for Chemo-Photothermal Therapy

Polyoxometalates are an emerging class of molecular clusters, with well-defined structures and chemical compositions that are produced through simple, low-cost, and highly reproducible methods. In particular, the wheel-shaped cluster {Mo154 } is a promising photothermal agent due to its intervalence charge transfer transitions. However, its toxicity hinders its systemic administration, being the development of a localized delivery system still incipient. Herein, an injectable and self-healing hydrogel of easy preparation and administration is developed, incorporating both {Mo154 } and doxorubicin for synergistic photothermal and chemotherapy applications. The hydrogel is composed of benzylaldehyde functionalized polyethylene glycol, poly(N-isopropylacrylamide) functionalized chitosan and {Mo154 }. The gelation occurs within 60 s at room temperature, and the dual crosslinking by Schiff base and electrostatic interactions generates a dynamic network, which enables self-healing after injection. Moreover, the hydrogel delivers chemotherapeutic drugs, with a release triggered by dual near infra-red (NIR) radiation and pH changes. This stimuli-responsive release system along with the photothermal conversion ability of the hydrogel allows the simultaneous combination of photothermal and chemotherapy. This synergic system efficiently ablates the cancer tumor in vivo with no systemic toxicity. Overall, this work paves the way for the development of novel {Mo154 }-based systems, incorporated in self-healing and injectable hydrogels for dual chemo-photothermal therapy.

pH-Responsive Nanocomposite Based Hydrogels for the Controlled Delivery of Ticagrelor; In Vitro and In Vivo Approaches

Background

Ticagrelor (TG), an antiplatelet drug is employed to treat patients with acute coronary syndrome, but its inadequate oral bioavailability due to poor solubility and low permeability restricts its effectiveness.

Purpose

This contemporary work was aimed to design a novel pH-sensitive nanocomposite hydrogel (NCH) formulation incorporating thiolated chitosan (TCH) based nanoparticles (NPs) of Ticagrelor (TG), to enhance its oral bioavailability for effectively inhibiting platelet aggregation.

Methods

NCHs were prepared by free radical polymerization technique, using variable concentrations of chitosan (CH) as biodegradable polymer, acrylic acid (AA) as a monomer, N,N-methylene bisacrylamide (MBAA) as cross-linker, and potassium persulphate (KPS) as initiator.

Results

The optimum hydrogel formulation was selected for fabricating NCHs, considering porosity, sol-gel fraction, swelling studies, drug loading capacity, and TG’s in vitro release as determining factors. Outcomes of the studies have shown that the extent of hydrogel swelling and drug release was comparatively greater at higher pH (7.4). Moreover, an amplifying trend was observed for drug loading and hydrogel swelling by increasing AA content, while it declined by increasing MBAA. The NCHs were evaluated by various physicochemical techniques and the selected formulation was subjected to in vivo bioavailability studies, confirming enhancement of bioavailability as indicated by prolonged half-life and multifold increase in area under the curve (AUC) as compared to pure TG.

Conclusion

The results suggest that NCHs demonstrated a pH-responsive, controlled behavior along with enhanced bioavailability. Thus NCHs can be effectively utilized as efficient delivery systems for oral delivery of TG to reduce the risk of myocardial infarction.

From Supramolecular Hydrogels to Multifunctional Carriers for Biologically Active Substances

Supramolecular hydrogels are 3D, elastic, water-swelled materials that are held together by reversible, non-covalent interactions, such as hydrogen bonds, hydrophobic, ionic, host-guest interactions, and metal-ligand coordination. These interactions determine the hydrogels' unique properties: mechanical strength; stretchability; injectability; ability to self-heal; shear-thinning; and sensitivity to stimuli, e.g., pH, temperature, the presence of ions, and other chemical substances. For this reason, supramolecular hydrogels have attracted considerable attention as carriers for active substance delivery systems. In this paper, we focused on the various types of non-covalent interactions. The hydrogen bonds, hydrophobic, ionic, coordination, and host-guest interactions between hydrogel components have been described. We also provided an overview of the recent studies on supramolecular hydrogel applications, such as cancer therapy, anti-inflammatory gels, antimicrobial activity, controlled gene drug delivery, and tissue engineering.