Injectable Thermoresponsive Hydrogel Formed by Alginate-g-Poly(N-isopropylacrylamide) That Releases Doxorubicin-Encapsulated Micelles as a Smart Drug Delivery System

Recent advances in smart hydrogels derived from polysaccharides and their applications for wound dressing and healing

Owing to their inherent biocompatibility and biodegradability, hydrogels derived from polysaccharides have emerged as promising candidates for wound management. However, the complex nature of wound healing often requires the development of smart hydrogels---intelligent materials capable of responding dynamically to specific physical or chemical stimuli. Over the past decade, an increasing number of stimuli-responsive polysaccharide-based hydrogels have been developed to treat various types of wounds. While a range of hydrogel types and their versatile functions for wound management have been discussed in the literature, there is still a need for a review of the crosslinking strategies used to create smart hydrogels from polysaccharides. This review provides a comprehensive overview of how stimuli-responsive hydrogels can be designed and made using five key polysaccharides: chitosan, hyaluronic acid, alginate, dextran, and cellulose. Various methods, such as chemical crosslinking, dynamic crosslinking, and physical crosslinking, which are used to form networks within these hydrogels, ultimately determine their ability to respond to stimuli, have been explored. This article further looks at different polysaccharide-based hydrogel wound dressings that can respond to factors such as reactive oxygen species, temperature, pH, glucose, light, and ultrasound in the wound environment and discusses how these responses can enhance wound healing. Finally, this review provides insights into how stimuli-responsive polysaccharide-based hydrogels can be developed further as advanced wound dressings in the future.

Smart hydrogel: A new platform for cancer therapy

Cancer is a significant contributor to mortality worldwide, posing a significant threat to human life and health. The unique bioactivity, ability to precisely control drug release, and minimally invasive properties of hydrogels are indispensable attributes that facilitate optimal performance in cancer therapy. However, conventional hydrogels lack the ability to dynamically respond to changes in the surrounding environment, withstand drastic changes in the microenvironment, and trigger drug release on demand. Therefore, this review focuses on smart-responsive hydrogels that are capable of adapting and responding to external stimuli. We comprehensively summarize the raw materials, preparation, and cross-linking mechanisms of smart hydrogels derived from natural and synthetic materials, elucidate the response principles of various smart-responsive hydrogels according to different stimulation sources. Further, we systematically illustrate the important role played by hydrogels in modern cancer therapies within the context of therapeutic principles. Meanwhile, the smart hydrogel that uses machine learning to design precise drug delivery has shown great prospects in cancer therapy. Finally, we present the outlook on future developments and make suggestions for future related work. It is anticipated that this review will promote the practical application of smart hydrogels in cancer therapy and contribute to the advancement of medical treatment.

Injectable and implantable hydrogels for localized delivery of drugs and nanomaterials for cancer chemotherapy: A review

Multiple chemotherapeutic strategies have been developed to tackle the complexity of cancer. Still, the outcome of chemotherapeutic regimens remains impaired by the drugs' weak solubility, unspecific biodistribution and poor tumor accumulation after systemic administration. Such constraints triggered the development of nanomaterials to encapsulate and deliver anticancer drugs. In fact, the loading of drugs into nanoparticles can overcome most of the solubility concerns. However, the ability of systemically administered drug-loaded nanomaterials to reach the tumor site has been vastly overestimated, limiting their clinical translation. The drugs' and drug-loaded nanomaterials' systemic administration issues have propelled the development of hydrogels capable of performing their direct/local delivery into the tumor site. The use of these macroscale systems to mediate a tumor-confined delivery of the drugs/drugs-loaded nanomaterials grants an improved therapeutic efficacy and, simultaneously, a reduction of the side effects. The manufacture of these hydrogels requires the careful selection and tailoring of specific polymers/materials as well as the choice of appropriate physical and/or chemical crosslinking interactions. Depending on their administration route and assembling process, these matrices can be classified as injectable in situ forming hydrogels, injectable shear-thinning/self-healing hydrogels, and implantable hydrogels, each type bringing a plethora of advantages for the intended biomedical application. This review provides the reader with an insight into the application of injectable and implantable hydrogels for performing the tumor-confined delivery of drugs and drug-loaded nanomaterials.

Advances in biomaterials and regenerative medicine for diabetic foot ulcer therapy

Diabetic foot ulcer (DFU), a severe complication of diabetes mellitus, presents significant clinical challenges due to its rapid deterioration and high morbidity rates. While conventional therapies exist kinds of limitations, their clinical utility is frequently constrained. Recent advancements in biomedical engineering have introduced innovative therapeutic modalities, particularly nanomaterials and hydrogels. However, emerging technologies face translational barriers including immature manufacturing processes leading to elevated costs, and insufficient long-term safety data due to limited clinical validation periods. Current clinical studies remain constrained by small cohort sizes and preliminary-stage investigations. The purpose of this study was to review traditional primary treatment and simultaneously combine clinical data to increase the speed of innovative safety, cost, and effectiveness indicator testing.

Advancing agricultural efficiency and sustainability: Bio-inspired superabsorbent hydrogels for slow and controlled release fertilizers

Bio-inspired superabsorbent hydrogels (BiSAHs) represent a versatile polymeric material class that has garnered significant interest due to their multifunctional attributes and extensive range of applications. A thorough examination of the literature and patents on BiSAHs highlights their critical role across diverse sectors. This review provides an in-depth analysis of BiSAHs, focusing on their classification, synthesis methodologies, and potential applications in agriculture. It critically examines biopolymer-based SAHs as soil conditioners and slow and controlled, focusing on their classification, synthesis methodologies, and potential applications in agriculture. It critically examines biopolymer-based SAHs as soil conditioners and slow and controlled-release fertilizers, elucidating the mechanisms governing water retention, swelling capacity, and nutrient release kinetics. The review further presents detailed case studies illustrating the enhancement of crop growth and productivity facilitated by BiSAHs and their effectiveness as agrochemical carriers. Moreover, it explores the role of SAHs in crop protection, particularly in mitigating adverse abiotic stresses such as heavy metal toxicity, salinity, and drought. The ecological, economic, and societal impacts of BiSAH-based controlled-release fertilizers are evaluated, providing a balanced perspective on their sustainability. Ultimately, the review offers insights into future directions and emerging advancements in the development and application of BiSAHs in agricultural settings.

Nutraceutical benefits of seaweeds and their phytocompounds: a functional approach to disease prevention and management

Seaweeds (SWD), macroalgae or sea vegetables are a diverse group of over 9000 macroscopic and multicellular marine algae taxonomically classified (based on morphology and pigmentation) as green, brown and red algae. With microalgae, SWD represents one of the most researched oceanic resources turned to as treasure troves of bioactive compounds with ethnomedicinal, pharmaceutical, cosmeceutical and dietetic end-uses for millennia. This review compiles the nutraceutical uses of SWD and their bioactive compounds in nutrition and traditional management of diseases, offering future perspectives on using this group of organisms to improve human life. The review reveals that the nutraceutical application of SWD as nutrient-dense marine foods for treating diseases may be correlated with their inherent biosynthesis and possession of minerals, vitamins, dietary fibres and bioactive compounds. Compounds of algal origin have been validated and found to elicit antimicrobial, anti-inflammatory, free radical scavenging (antioxidant), antiproliferative and antidiabetic activities, among others. © 2025 Society of Chemical Industry.

A β-cyclodextrin-based supramolecular modular system creating micellar carriers for codelivery of doxorubicin and siRNA for potential combined chemotherapy and immunotherapy

The combination of chemotherapy and gene therapy holds promise in treating cancer. A key strategy is to use small interfering RNAs (siRNAs) to silence programmed death-ligand 1 (PD-L1) expression in cancer cells, disrupting tumor immune evasion and enhancing anticancer treatments, particularly when used in conjunction with chemotherapy drugs such as doxorubicin (Dox). However, effective codelivery of drugs and genes requires carefully designed carriers and complex synthesis procedures. To address this challenge, we propose a convenient modular self-assembly system for creating multifunctional micellar carriers that can efficiently codeliver both Dox and siRNA, where micelles are formed by cationic amphiphilic supramolecular architectures that are constructed through host-guest interactions between β-cyclodextrin (β-CD) and adamantane (Ad) to incorporate various functional polymer segments, such as low-molecular-weight polyethylenimine (oligoethylenimine, OEI), poly(ethylene glycol) (PEG), and polycaprolactone (PCL), at adjustable ratios. The supramolecular micellar carrier systems can be easily optimized to achieve excellent structural stability, drug and gene loading, and delivery efficiency, resulting in significant anticancer effects from Dox delivery and simultaneous inhibition of PD-L1 due to the siRNA delivery. Therefore, this modular supramolecular strategy offers a sophisticated, adaptable, and straightforward approach to creating multifunctional micellar carriers, with potential for drug- and gene-based immune-assisted cancer therapy.

Smart Poly(N-isopropylacrylamide)-Based Hydrogels: A Tour D'horizon of Biomedical Applications

Hydrogels are innovative materials characterized by a water-swollen, crosslinked polymeric network capable of retaining substantial amounts of water while maintaining structural integrity. Their unique ability to swell or contract in response to environmental stimuli makes them integral to biomedical applications, including drug delivery, tissue engineering, and wound healing. Among these, "smart" hydrogels, sensitive to stimuli such as pH, temperature, and light, showcase reversible transitions between liquid and semi-solid states. Thermoresponsive hydrogels, exemplified by poly(N-isopropylacrylamide) (PNIPAM), are particularly notable for their sensitivity to temperature changes, transitioning near their lower critical solution temperature (LCST) of approximately 32 °C in water. Structurally, PNIPAM-based hydrogels (PNIPAM-HYDs) are chemically versatile, allowing for modifications that enhance biocompatibility and functional adaptability. These properties enable their application in diverse therapeutic areas such as cancer therapy, phototherapy, wound healing, and tissue engineering. In this review, the unique properties and behavior of smart PNIPAM are explored, with an emphasis on diverse synthesis methods and a brief note on biocompatibility. Furthermore, the structural and functional modifications of PNIPAM-HYDs are detailed, along with their biomedical applications in cancer therapy, phototherapy, wound healing, tissue engineering, skin conditions, ocular diseases, etc. Various delivery routes and patents highlighting therapeutic advancements are also examined. Finally, the future prospects of PNIPAM-HYDs remain promising, with ongoing research focused on enhancing their stability, responsiveness, and clinical applicability. Their continued development is expected to revolutionize biomedical technologies, paving the way for more efficient and targeted therapeutic solutions.

Engineering Multiresponsive Alginate/PNIPAM/Carbon Nanotube Nanocomposite Hydrogels as On-Demand Drug Delivery Platforms

Second near-infrared (NIR-II) responsive hydrogels have shown significant potential in biomedical applications due to their excellent remote actuation property and the high tissue penetrations of the NIR-II light. Nevertheless, hydrogels with a single NIR-II light response may not meet the diverse requirements and complex conditions of clinical applications. Here, a novel multi-responsive nanocomposite hydrogel with enhanced suitability for controlled drug release is developed. This nanocomposite hydrogel is constructed by combining alginate dialdehyde (ADA), polyethyleneimine (PEI), poly(N-isopropylacrylamide) (PNIPAM), and phenylboronic acid-modified polyethyleneimine (PBA-PEI) functionalized multi-walled carbon nanotubes (PP-CNT) through the formation of dynamic covalent bonds (i.e., imine bonds and boronate ester bonds), forming ADA/PEI/PNIPAM/PP-CNT (APN/PP-CNT) hydrogel. PNIPAM is incorporated into the hydrogel network to facilitate drug release triggered by its aggregation when subjected to the high temperatures produced by NIR-II light irradiation. The dynamic covalent bonds and CNT in the network provide the APN/PP-CNT nanocomposite hydrogels with responsiveness to multiple stimuli, including pH, hydrogen peroxide, temperature, and NIR-II light. The APN/PP-CNT nanocomposite hydrogel performs effective NIR-II light responsiveness in both in vitro and in vivo drug release, highlighting its potential as a promising drug delivery platform.

Tumor microenvironment as a target for developing anticancer hydrogels

OBJECTIVE

It has been reported that cancer cells get protected by a complex and rich multicellular environment i.e. the tumor microenvironment (TME) consisting of varying immune cells, endothelial cells, dendritic cells, fibroblasts, etc. This manuscript is aimed at the characteristic features of TME considered as potential target(s) for developing smart anticancer hydrogels.

SIGNIFICANCE

The stimuli-specific drug delivery systems especially hydrogels that can respond to the characteristic features of TME are fabricated for treating cancer. For developing anticancer formulations, TME targeting can be considered an alternative way as it enhances the cytotoxic potential and reduces the unwanted effects. This manuscript shall be of quite interest to academicians, researchers, and clinicians engaged in oncology.

METHODS

The manuscript was prepared by using the data available in the public domain in online resources such as Google Scholar, PubMed, Science Direct, Scopus, Web of Science, Research Gate, etc.

RESULTS

Smart hydrogels, sensitive to some specific features of TME such as low pH, high concentration of glutathione, specific enzymes, etc., are promising anticancer formulations as these improve the efficacy and lower the side effects of chemotherapy.

CONCLUSION

The stimuli-responsive hydrogels have been gaining more attention for delivering cytotoxic drugs to the TME in response to specific stimuli. The stimuli-responsive hydrogels, comprising of cytotoxic drug(s) and specific polymers have some special features such as similarity with biological matrix, ability to respond to various internal as well as external stimuli, improved permeability, porosity, biocompatibility, resemblance with soft living tissues, etc.; and are considered as the promising anticancer candidates.

Synthesis and Characterization of Lipid-Polyzwitterion Diblock Copolymers for Optimizing Micelle Formation to Enhance Anticancer Drug Delivery in 2D and 3D Cell Cultures

Amphiphilic polymers with distinct polarity differences, known as sharp polarity contrast polymers (SPCPs), have gained much attention for their ability to form micelles with low critical micelle concentrations (CMCs) and potential in anticancer drug delivery. This study addresses the limited research on structure-property relationships of SPCPs by developing various SPCPs and exploring their physicochemical properties and biological applications. Specifically, the superhydrophobic aliphatic palmitoyl (Pal) was coupled to the superhydrophilic zwitterionic poly(2-methacryloyloxyethyl phosphorylcholine) (pMPC) to form Pal-pMPC diblock copolymers. Adjusting the lengths of hydrophilic chains allowed the creation of structures with varying hydrophilic-hydrophobic ratios for micelle formation. Comprehensive evaluations were carried out, including particle size, CMC, chain exchange rates, cellular uptake efficiency, and anticancer effectiveness. Our findings indicate that micelles with optimal hydrophilic-hydrophobic ratios significantly enhanced cellular uptake and cytotoxicity in both two-dimensional (2D) and three-dimensional (3D) tumor models, offering valuable insights for designing SPCPs for anticancer drug delivery.

Alginate Heterografted Copolymer Thermo-Induced Hydrogel Reinforced by PAA-g-P(boc-L-Lysine): Effects on Hydrogel Thermoresponsiveness

In this article, we report on the alginate heterografted by Poly(N-isopropyl acrylamide-co-N-tert-butyl acrylamide) and Poly(N-isopropyl acrylamide) (ALG-g-P(NIPAM86-co-NtBAM14)-g-PNIPAM) copolymer thermoresponsive hydrogel, reinforced by substituting part of the 5 wt% aqueous formulation by small amounts of Poly(acrylic acid)-g-P(boc-L-Lysine) (PAA-g-P(b-LL)) graft copolymer (up to 1 wt%). The resulting complex hydrogels were explored by oscillatory and steady-state shear rheology. The thermoresponsive profile of the formulations were affected remarkably by increasing the PAA-g-P(b-LL) component of the polymer blend. Especially, the sol-gel behavior altered to soft gel-strong gel behavior due to the formation of a semi-interpenetrating network based on the hydrophobic self-organization of the PAA-g-P(b-LL). In addition, the critical characteristics, namely Tc,thermothickening (temperature above which the viscosity increases steeply) and ΔT (transition temperature window), shifted and broadened to lower temperatures, respectively, due to the influence of the hydrophobic side chains P(b-LL) on the LCST of the PNIPAM-based grafted chains of the alginate. The effect of ionic strength was also examined, showing that this is another important factor affecting the thermoresponsiveness of the hydrogel. Again, the thermoresponsive profile of the hydrogel was changed significantly by the presence of salt. All the formulations showed self-healing capability and tolerance injectability, suitable for potential bioapplications in living bodies.

Advances in cancer diagnosis and therapy by alginate-based multifunctional hydrogels: A review

The field of oncology has been changed by the application of hydrogels. These 3D polymeric networks have demonstrated significant promise in the treatment of cancer and can boost the efficacy of conventional therapeutics including chemotherapy and immunotherapy. Noteworthy, the development of biocompatible and effective hydrogels has been of interest. In this case, alginate as a biopolymer and carbohydrate polymer has been used to modify or synthesis multifunctional nanoparticles for the treatment of human diseases, especially cancer. Therefore, highlighting the function of alginate in the development of hydrogels in cancer therapy can provide new insights for improving outcome and survival rate of patients. Alginate hydrogels improve the specific and selective delivery of cargo and therefore, they reduce the systemic toxicity of drugs, while they enhance anti-cancer activity. Alginate hydrogels protect the genes against degradation by enzymes and increase blood circulation time. The alginate hydrogels can respond to the specific stimuli in the tumor microenvironment including pH, redox and light to improve the site-specific release of cargo. The nanoparticles can be incorporated in the structure of alginate hydrogels to augment their anti-cancer activity. In addition, alginate hydrogels can accelerate immunotherapy and phototherapy through delivery of immunomodulators and photosensitizers, respectively.

Alginate as a Sustainable and Biodegradable Material for Medical and Environmental Applications-The Case Studies

Alginates are salts of alginic acid derived mainly from sea algae of the genus brown algae. They are also synthesized by some bacteria. They belong to negatively charged polysaccharides exhibiting some rheological properties. High plasticity and the ability to modify the structure are the reasons for their application in numerous industries. Moreover, when in contact with the living tissue, they do not trigger an immune response, and for this reason they are the most often tested materials for medical applications. The paper discusses the latest applications, including 3D bioprinting, drug delivery systems, and sorptive properties. Recognizing alginates as biomaterials, it emphasizes the necessity for precise processing and modification to industrialize them for specific uses. This review aims to provide a thorough understanding of the advancements in alginate research, underscoring their potential for innovative applications.

Recent Advances in Superabsorbent Hydrogels Derived from Agro Waste Materials for Sustainable Agriculture: A Review

Superabsorbent hydrogels made from agro waste materials have the potential to promote sustainable agriculture and environmental sustainability. These hydrogels not only help reduce water consumption and increase crop yields but also contribute to minimizing waste and lowering greenhouse gas emissions. Recent research on superabsorbent hydrogels derived from agro wastes has focused on the preparation of hydrogels based on natural polymers isolated from agro wastes, such as cellulose, hemicellulose, and lignin. This review provides an in-depth examination of hydrogels developed from raw agro waste materials and natural polymers extracted from agro wastes, highlighting that these studies start with raw wastes as the main materials. The utilization strategies for specific types of agro wastes are comprehensively described. This review outlines different methods utilized in the production of these hydrogels, including physical cross-linking techniques such as dissolution-regeneration and freeze-thawing, as well as chemical cross-linking methods involving various cross-linking agents and graft polymerization techniques such as free radical polymerization, microwave-assisted polymerization, and γ radiation graft polymerization. Specifically, this review explores the applications of agro waste-based superabsorbent hydrogels in enhancing soil properties such as water retention and slow-release of fertilizers for sustainable agriculture.

Recent progress in stimuli-responsive polymeric micelles for targeted delivery of functional nanoparticles

Stimuli-responsive polymeric micelles have emerged as a revolutionary approach for enhancing the in vivo stability, biocompatibility, and targeted delivery of functional nanoparticles (FNPs) in biomedicine. This article comprehensively reviews the preparation methods of these polymer micelles, detailing the innovative strategies employed to introduce stimulus responsiveness and surface modifications essential for precise targeting. We delve into the breakthroughs in utilizing these micelles to selectively deliver various FNPs including magnetic nanoparticles, upconversion nanoparticles, gold nanoparticles, and quantum dots, highlighting their transformative impact in the biomedical realm. Concluding, we present an insight into the current research landscape, addressing the challenges at hand, and envisioning the future trajectory in this burgeoning domain. Join us as we navigate the exciting confluence of polymer science and nanotechnology in reshaping biomedical solutions.

4D Printing for Biomedical Applications

4D (bio-)printing endows 3D printed (bio-)materials with multiple functionalities and dynamic properties. 4D printed materials have been recently used in biomedical engineering for the design and fabrication of biomedical devices, such as stents, occluders, microneedles, smart 3D-cell engineered microenvironments, drug delivery systems, wound closures, and implantable medical devices. However, the success of 4D printing relies on the rational design of 4D printed objects, the selection of smart materials, and the availability of appropriate types of external (multi-)stimuli. Here, this work first highlights the different types of smart materials, external stimuli, and design strategies used in 4D (bio-)printing. Then, it presents a critical review of the biomedical applications of 4D printing and discusses the future directions of biomedical research in this exciting area, including in vivo tissue regeneration studies, the implementation of multiple materials with reversible shape memory behaviors, the creation of fast shape-transformation responses, the ability to operate at the microscale, untethered activation and control, and the application of (machine learning-based) modeling approaches to predict the structure-property and design-shape transformation relationships of 4D (bio)printed constructs.

Development of Injectable Thermosensitive Nanocomposite Hydrogel for Ratiometric Drug Delivery to Treat Drug Resistant Chondrosarcoma In Vivo

Chondrosarcoma(CS), a prevalent primary malignant bone tumor, frequently exhibits chemotherapy resistance attributed to upregulated anti-apoptosis pathways such as the Bcl-2 family. In this manuscript, a new strategy is presented to augment chemosensitivity and mitigate systemic toxicity by harnessing a nano-enabled drug delivery hydrogel platform. The platform utilizes "PLGA-PEG-PLGA", an amphiphilic triblock copolymer combining hydrophilic polyethylene glycol (PEG) and hydrophobic polylactide glycolide (PLGA) blocks, renowned for its properties conducive to crafting a biodegradable, temperature-sensitive hydrogel. This platform is tailored to encapsulate a ratiometrically designed dual-loaded liposomes containing a first-line chemo option for CS, Doxorubicin (Dox), plus a calculated amount of small molecule inhibitor for anti-apoptotic Bcl-2 pathway, ABT-737. In vitro and in vivo evaluations demonstrate successful Bcl-2 suppression, resulting in the restoration of Dox sensitivity, evident through impeded tumor growth and amplified necrosis rates at the tumor site. This delivery system showcases remarkable thermal responsiveness, injectability, and biodegradability, all finely aligned with the clinical demands of CS treatment. Collectively, this study introduces a transformative avenue for tackling drug resistance in CS chemotherapy, offering significant clinical potential.

Injectable hydrogels based on alginates grafted with LCST side-chains of different chemistry

A homologous series of thermoassociating copolymers was prepared by grafting onto alginates different amounts of three different temperature responsive polymers: poly(N-isopropylacrylamide), poly(di(ethylene glycol)methacrylate) and poly(ethylene oxide-co-propylene oxide). From a large set of analytical techniques combining rheology, calorimetry, NMR and SAXS, the relevant parameters controlling the sol/gel transition and the gel properties, mainly the degree of entanglement of macromolecules and the fraction of responsive stickers, were highlighted and interpreted objectively by considering the particularities of the phase diagrams of LCST polymers. Complementary analyses were implemented to investigate adhesiveness, injectabilty, gel swelling and molecular release in physiological environment of thermogelling formulations. In particular, it is shown that steady shear experiments allow to predict the injection forces by taking into account the characteristics of the system (syringe and needle), and that the rapid gelation of the formulations when they are heated at 37 °C delays the release of small molecules into the environment. The overall set of data is discussed in the framework of scaling relations in order to draw quantitative guidelines for the design of injectable thermoresponsive hydrogels.

Tailor-Made Polysaccharides for Biomedical Applications

Polysaccharides (PSAs) are carbohydrate-based macromolecules widely used in the biomedical field, either in their pure form or in blends/nanocomposites with other materials. The relationship between structure, properties, and functions has inspired scientists to design multifunctional PSAs for various biomedical applications by incorporating unique molecular structures and targeted bulk properties. Multiple strategies, such as conjugation, grafting, cross-linking, and functionalization, have been explored to control their mechanical properties, electrical conductivity, hydrophilicity, degradability, rheological features, and stimuli-responsiveness. For instance, custom-made PSAs are known for their worldwide biomedical applications in tissue engineering, drug/gene delivery, and regenerative medicine. Furthermore, the remarkable advancements in supramolecular engineering and chemistry have paved the way for mission-oriented biomaterial synthesis and the fabrication of customized biomaterials. These materials can synergistically combine the benefits of biology and chemistry to tackle important biomedical questions. Herein, we categorize and summarize PSAs based on their synthesis methods, and explore the main strategies used to customize their chemical structures. We then highlight various properties of PSAs using practical examples. Lastly, we thoroughly describe the biomedical applications of tailor-made PSAs, along with their current existing challenges and potential future directions.

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.

Design of smart temperature-sensitive terpolymeric hydrogel for multi-applications in liquid chromatography

Hydrogels with a unique three-dimensional network structure have been widely used in a variety of fields. However, hydrogels are prone to swelling under water-rich conditions, which severely limits their application in liquid chromatography. Therefore, producing a hydrogel with reliable performance and good mechanical property is essential. Smart temperature-sensitive chromatographic packings have attracted extensive attentions in recent years. In this work, sodium 4-styrenesulfonate and 1-octadecene were introduced into the poly(N-isopropylacrylamide) hydrogel to improve mechanical property and separation performance. As a consequence, a smart temperature-sensitive terpolymeric hydrogel modified silica stationary phase (ION-hydrogel@SiO2) was synthesized for multimode liquid chromatographic separation. It was found that this new ION-hydrogel@SiO2 column exhibited excellent chromatographic separation ability for a wide range of analytes. To a certain extent, this new column has a higher chromatographic separation efficiency compared to the commercial C18 column and XAmide column. Moreover, the use of low proportion of organic phase in chromatographic separation is conducive to the realization of green chromatography. By investigating the chromatographic separation mechanism, it has been demonstrated that the hydrogen bonding interaction is primarily responsible for the temperature-sensitive behavior of the hydrogel. Finally, the ION-hydrogel@SiO2 column was used for the determination of pyridoxine in the commercially available tablet samples. In conclusion, this study presents a feasible idea for the development of novel copolymer hydrogels as liquid chromatographic stationary phases.

A Remarkable Impact of pH on the Thermo-Responsive Properties of Alginate-Based Composite Hydrogels Incorporating P2VP-PEO Micellar Nanoparticles

A heterograft copolymer with an alginate backbone, hetero-grafted by polymer pendant chains displaying different lower critical solution temperatures (LCSTs), combined with a pH-responsive poly(2-vinyl pyridine)-b-poly(ethylene oxide) (P2VP-b-PEO) diblock copolymer forming micellar nanoparticles, was investigated in aqueous media at various pHs. Due to its thermo-responsive side chains, the copolymer forms hydrogels with a thermo-induced sol-gel transition, above a critical temperature, Tgel (thermo-thickening). However, by lowering the pH of the medium in an acidic regime, a remarkable increase in the elasticity of the formulation was observed. This effect was more pronounced in low temperatures (below Tgel), suggesting secondary physical crosslinking, which induces significant changes in the hydrogel thermo-responsiveness, transforming the sol-gel transition to soft gel-strong gel. Moreover, the onset of thermo-thickening shifted to lower temperatures followed by the broadening of the transition zone, implying intermolecular interactions between the uncharged alginate backbone with the PNIPAM side chains, likely through H-bonding. The shear-thinning behavior of the soft gel in low temperatures provides injectability, which allows potential applications for 3D printing. Furthermore, the heterograft copolymer/nanoparticles composite hydrogel, encapsulating a model hydrophobic drug in the hydrophobic cores of the nanoparticles, was evaluated as a pH-responsive drug delivery system. The presented tunable drug delivery system might be useful for biomedical potential applications.

Hyaluronic Acid-Conjugated Thermoresponsive Polymer-Based Bioformulation Enhanced Wound Healing and Gut Barrier Repair of a TNBS-Induced Colitis Injury Ex Vivo Model in a Dynamic Perfusion Device

Impairment of intestinal epithelium is a typical feature of inflammatory bowel disease (IBD) that causes leakage of bacteria and antigens from the intestinal lumen and thus results in persistent immune activation. Hence, healing and regeneration of the damaged gut mucosa is a promising therapeutic approach to achieve deep remission in IBD. Currently, available systemic therapies have moderate effects and are often associated with numerous side effects and malignancies. In this study, we aimed to develop a topical therapy by chemically conjugating a temperature-responsive polymer, i.e., poly(N-isopropylacrylamide), along with hyaluronic acid to obtain a sprayable therapeutic formulation that upon colon instillation adheres to the damaged gut mucosa due to its temperature-induced phase transition and mucoadhesive properties. An ex vivo adhesion experiment demonstrates that this therapeutic formulation forms a thin physical coating on the mucosal lining at a physiological temperature within 5 min. Physicochemical characterization of (P(NIPAM-co-NTBAM)-HA) established this formulation to be biocompatible, hemo-compatible, and non-immunogenic. Prednisolone was encapsulated within the polymer formulation to achieve maximum therapeutic efficacy in the case of IBD-like conditions as assessed in a custom-fabricated perfusion-based ex vivo model system. Histological analysis suggests that the prednisolone-encapsulated polymer formulation nearly restored the mucosal architecture after 2,4,6-trinitrobenzenesulfonic acid-induced damage. Furthermore, a significant (p ≤ 0.001) increase in mRNA levels of Muc-2 and ZO-1 in treated groups further confirmed the mucosal epithelial barrier restoration.

Structure-activity relationships of bioactive polysaccharides extracted from macroalgae towards biomedical application: A review

Macroalgae are valuable and structurally diverse sources of bioactive compounds among marine resources. The cell walls of macroalgae are rich in polysaccharides which exhibit a wide range of biological activities, such as anticoagulant, antioxidant, antiviral, anti-inflammatory, immunomodulatory, and antitumor activities. Macroalgae polysaccharides (MPs) have been recognized as one of the most promising candidates in the biomedical field. However, the structure-activity relationships of bioactive polysaccharides extracted from macroalgae are complex and influenced by various factors. A clear understanding of these relationships is indeed critical in developing effective biomedical applications with MPs. In line with these challenges and knowledge gaps, this paper summarized the structural characteristics of marine MPs from different sources and relevant functional and bioactive properties and particularly highlighted those essential effects of the structure-bioactivity relationships presented in biomedical applications. This review not only focused on elucidating a particular action mechanism of MPs, but also intended to identify a novel or potential application of these valued compounds in the biomedical field in terms of their structural characteristics. In the last, the challenges and prospects of MPs in structure-bioactivity elucidation were further discussed and predicted, where they were emphasized on exploring modern biotechnology approaches potentially applied to expand their promising biomedical applications.

Enhancing the Properties of Self-Healing Gelatin Alginate Hydrogels by Hofmeister Mediated Electrostatic Effect

The cross-linker-free hydrogels have gained attention due to their lack of need for chemically modified polymers, resulting in better biocompatibility. The hydrogel properties can be enhanced by altering physical forces such as electrostatics and H-bonds. Tuning the physical interactions between polymers, salts, and plasticisers can unlock new horizons in material properties. This article examines four different salts and mixtures to determine their impact on gelatin-alginate biomaterial design. Drug release, swelling, and rheological properties are represented using a 3-D plot, and optimum samples are identified. It is concluded that kosmotropes yield better release and swelling results than chaotropes. The physical interactions of these salts with polymers are explained using DLS and FTIR/ATR studies, and these findings are corroborated with release, swelling, and rheological analyses. Another aspect of the biomaterial, self-healing property, is also considered. A 3-D plot is prepared using release kinetics, gel strength, and recovery percentage (three important factors for self-healing hydrogels). Chaotropes are identified as better candidates for self-healing behaviour. However, when considering gel strength, release, and self-healing, kosmotropes are favourable. Hence, different salts can be selected based on the desired application for hydrogels. It is also concluded that electrostatic forces hinder the formation of H-bonds between polymer chains.

Advances in injectable hydrogel: Design, functional regulation, and biomedical applications

Recently, injectable hydrogels have been considered smart materials and have been widely researched for their use as scaffolds. They resemble the extracellular matrix of native tissue and have the capability for homogeneous mixing with therapeutic agents. It can be implanted into living bodies with minimal invasiveness and usability for irregularly shaped sites. Such unique features make the injectable hydrogels as promising materials in tissue engineering, drug delivery system, and gene/protein delivery. This review article provides a comprehensive overview of the different mechanisms employed in the preparation of injectable hydrogel, as well as a detailed exploration of its applications in the biomedical field. Furthermore, the article highlights the critical importance of developing injectable hydrogels as market‐viable products, highlighting their potential impact in the field of regenerative medicine.

Development of a thermosensitive hydrogel based on Polaxamer 407 and gellan gum with inclusion complexes (Sulfobutylated-β-cyclodextrin-Farnesol) as a local drug delivery system

This work proposes the development of a thermosensitive local drug release system based on Polaxamer 407, also known as Pluronic® F-127 (PF-127), Gellan Gum (GG) and the inclusion complex Sulfobutylated-β-cyclodextrin (CD) with Farnesol (FOH). Rheological properties of the hydrogels and their degradation were studied. According to the rheological results, a solution of 20% w/v of PF-127 forms a strong gel with a gelling temperature of about 25 °C (storage modulus of 15,000 Pa). The addition of the GG increased the storage modulus (optimal concentration of 0.5 % w/v) twofold without modifying the gelling temperature. Moreover, including 0.5% w/v of GG also increased 6 times the degradation time of the hydrogel. Regarding the inclusion complex, the addition of free CD decreased the viscosity and the gel strength since polymer chains were included in CD cavity without affecting the gelling temperature. Contrarily, the inclusion complex CD-FOH did not significantly modify any property of the formulation because the FOH was hosted in the CD. Furthermore, a mathematical model was developed to adjust the degradation time. This model highlights that the addition of the GG decreases the number of released chains from the polymeric network (which coincides with an increase in the storage modulus) and that the free CD reduces the degradation rate, protecting the polymeric chains. Finally, FOH release was quantified with a specific device, that was designed and printed for this type of system, observing a sustainable drug release (similar to FOH aqueous solubility, 8 μM) dependent on polymer degradation.

Dual-Targeted Nanoparticle-in-Microparticle System for Ulcerative Colitis Therapy

Conventional oral therapy for ulcerative colitis (UC) is associated with premature release or degradation of drugs in the harsh gastrointestinal environment, resulting in reduced therapeutic effectiveness. Consequently, the present study aims to develop a dual-targeted delivery system with a nanoparticle-in-microparticle (nano-in-micro) structure. The prepared Asiatic Acid-loaded delivery system (AA/CDM-BT-ALG) has pH-sensitive properties. Cellular uptake evaluation confirms that nanoparticles exhibit targeted absorption by macrophages and Caco-2 cells through mannose (Man) receptor and biotin-mediated endocytosis, respectively. Therefore, this mechanism effectively enhances intracellular drug concentration. Additionally, the biodistribution study conducted on the gastrointestinal tract of mice indicates that the colon of the microspheres group shows higher fluorescence intensity with longer duration than the other groups. This finding indicates that the microspheres exhibit selective accumulation in areas of colon inflammation. In vivo experiments in colitis mice showed that AA/CDM-BT-ALG significantly alleviates the histopathological characteristics of the colon, reduced neutrophil, and macrophage infiltration, and decreases pro-inflammatory cytokine expression. Furthermore, the effect of AA/CDM-BT-ALG on colitis is validated to be closely related to the TLR4/MyD88/NF-κB signaling pathway. The present findings suggest that the development of a dual-targeted delivery system is accomplished effectively, with the potential to serve as a drug-controlled release system for treating UC.

Thermo-Responsive Hydrogels Coupled with Photothermal Agents for Biomedical Applications

Intelligent hydrogels are materials with abilities to change their chemical nature or physical structure in response to external stimuli showing promising potential in multitudinous applications. Especially, photo-thermo coupled responsive hydrogels that are prepared by encapsulating photothermal agents into thermo-responsive hydrogel matrix exhibit more attractive advantages in biomedical applications owing to their spatiotemporal control and precise therapy. This work summarizes the latest progress of the photo-thermo coupled responsive hydrogel in biomedical applications. Three major elements of the photo-thermo coupled responsive hydrogel, i.e., thermo-responsive hydrogel matrix, photothermal agents, and construction methods are introduced. Furthermore, the recent developments of these hydrogels for biomedical applications are described with some selected examples. Finally, the challenges and future perspectives for photo-thermo coupled responsive hydrogels are outlined.

Phase transition and potential biomedical applications of thermoresponsive compositions based on polysaccharides, proteins and DNA: A review

Smart thermoresponsive polymers have long attracted attention as materials of a great potential for biomedical applications, mainly for drug delivery, tissue engineering and wound dressing, with a special interest to injectable hydrogels. Poly-N-isopropylacrylamide (PNIPAM) is the most important synthetic thermoresponsive polymer due to its physiologically relevant transition temperature. However, the use of unmodified PNIPAM encounters such problems as low biodegradability, low drug loading capacity, slow response to thermal stimuli, and insufficient mechanical robustness. The use of natural polysaccharides and proteins in combinations with PNIPAM, in the form of grafted copolymers, IPNs, microgels and physical mixtures, is aimed at overcoming these drawbacks and creating dual-functional materials with both synthetic and natural polymers' properties. When developing such compositions, special attention should be paid to preserving their key property, thermoresponsiveness. Addition of hydrophobic and hydrophilic fragments to PNIPAM is known to affect its transition temperature. This review covers various classes of natural polymers - polysaccharides, fibrous and non-fibrous proteins, DNA - used in combination with PNIPAM for the prospective biomedical purposes, with a focus on their phase transition temperatures and its relation to the natural polymer's structure.

Algal Phycocolloids: Bioactivities and Pharmaceutical Applications

Seaweeds are abundant sources of diverse bioactive compounds with various properties and mechanisms of action. These compounds offer protective effects, high nutritional value, and numerous health benefits. Seaweeds are versatile natural sources of metabolites applicable in the production of healthy food, pharmaceuticals, cosmetics, and fertilizers. Their biological compounds make them promising sources for biotechnological applications. In nature, hydrocolloids are substances which form a gel in the presence of water. They are employed as gelling agents in food, coatings and dressings in pharmaceuticals, stabilizers in biotechnology, and ingredients in cosmetics. Seaweed hydrocolloids are identified in carrageenan, alginate, and agar. Carrageenan has gained significant attention in pharmaceutical formulations and exhibits diverse pharmaceutical properties. Incorporating carrageenan and natural polymers such as chitosan, starch, cellulose, chitin, and alginate. It holds promise for creating biodegradable materials with biomedical applications. Alginate, a natural polysaccharide, is highly valued for wound dressings due to its unique characteristics, including low toxicity, biodegradability, hydrogel formation, prevention of bacterial infections, and maintenance of a moist environment. Agar is widely used in the biomedical field. This review focuses on analysing the therapeutic applications of carrageenan, alginate, and agar based on research highlighting their potential in developing innovative drug delivery systems using seaweed phycocolloids.

Injectable Thermoresponsive Hydrogels for Cancer Therapy: Challenges and Prospects

The enervating side effects of chemotherapeutic drugs have necessitated the use of targeted drug delivery in cancer therapy. To that end, thermoresponsive hydrogels have been employed to improve the accumulation and maintenance of drug release at the tumour site. Despite their efficiency, very few thermoresponsive hydrogel-based drugs have undergone clinical trials, and even fewer have received FDA approval for cancer treatment. This review discusses the challenges of designing thermoresponsive hydrogels for cancer treatment and offers suggestions for these challenges as available in the literature. Furthermore, the argument for drug accumulation is challenged by the revelation of structural and functional barriers in tumours that may not support targeted drug release from hydrogels. Other highlights involve the demanding preparation process of thermoresponsive hydrogels, which often involves poor drug loading and difficulties in controlling the lower critical solution temperature and gelation kinetics. Additionally, the shortcomings in the administration process of thermosensitive hydrogels are examined, and special insight into the injectable thermosensitive hydrogels that reached clinical trials for cancer treatment is provided.

A new approach to the development and assessment of doxorubicin-loaded nanoliposomes for the treatment of osteosarcoma in 2D and 3D cell culture systems

Doxorubicin (DOX) is an effective anticancer drug used for the treatment of osteosarcoma. Liposomal nanocarriers for doxorubicin administration are now regarded as one of the most promising approaches to overcome multiple drug resistance and adverse side effects. The use of hydrogel as a 3D scaffold to mimic the cellular environment and provide comparable biological conditions for deeper investigations of cellular processes has attracted considerable attention. This study aimed to evaluate the impact of liposomal doxorubicin on the osteosarcoma cell line in the presence of alginate hydrogel as a three-dimensional scaffold. Different liposomal formulations based on cholesterol, phospholipids, and surfactants containing doxorubicin were developed using the thin-layer hydration approach to improve therapeutic efficacy. The final selected formulation was superficially modified using DSPE-mPEG2000. A three-dimensional hydrogel culture model with appropriate structure and porosity was synthesized using sodium alginate and calcium chloride as crosslinks for hydrogel. Then, the physical properties of liposomal formulations, such as mechanical and porosity, were characterized. The toxicity of the synthesized hydrogel was also assessed. Afterward, the cytotoxicity of nanoliposomes was analyzed on the Saos-2 and HFF cell lines in the presence of a three-dimensional alginate scaffold using the MTT assay. The results indicated that the encapsulation efficiency, the amount of doxorubicin released within 8 h, the mean size of vesicles, and the surface charge were 82.2%, 33.0%, 86.8 nm, and -4.2 mv, respectively. As a result, the hydrogel scaffolds showed sufficient mechanical resistance and suitable porosity. The MTT assay demonstrated that the synthesized scaffold had no cytotoxicity against cells, while nanoliposomal DOX exhibited marked toxicity against the Saos-2 cell line in the 3D culture medium of alginate hydrogel compared to the free drug in the 2D culture medium. Our research showed that the 3D culture model physically resembles the cellular matrix, and nanoliposomal DOX with proper size could easily penetrate into cells and cause higher cytotoxicity compared to the 2D cell culture.

Structures, Properties, and Bioengineering Applications of Alginates and Hyaluronic Acid

In recent years, polymeric materials have been used in a wide range of applications in a variety of fields. In particular, in the field of bioengineering, the use of natural biomaterials offers a possible new avenue for the development of products with better biocompatibility, biodegradability, and non-toxicity. This paper reviews the structural and physicochemical properties of alginate and hyaluronic acid, as well as the applications of the modified cross-linked derivatives in tissue engineering and drug delivery. This paper summarizes the application of alginate and hyaluronic acid in bone tissue engineering, wound dressings, and drug carriers. We provide some ideas on how to replace or combine alginate-based composites with hyaluronic-acid-based composites in tissue engineering and drug delivery to achieve better eco-economic value.

Multifunctional thermosensitive hydrogel based on alginate and P(NIPAM-co-HEMIN) composites for accelerated diabetic wound healing

Non-healing wounds in patients with diabetes are a concerning issue associated with amputation and a high mortality rate. These wounds are exacerbated by oxidative stress and microbial infections resulting from hyperglycemia. Therefore, advanced materials for repairing wound beds must be identified urgently. This paper introduces a topically applicable composite hydrogel with thermosensitive properties and presents the antibacterial and antioxidant activities in mice with diabetes-induced wounds. This composite is developed by combining poly N-isopropyl acrylamide (NIPAM)-copolymerized HEMIN (NIPAM-co-HEMIN) and amine-modified alginate (ALG-EDA) biomaterials, with Ag nanoparticles (AgNPs) incorporated into the system as an antibacterial agent. Results of antibacterial tests show that the p(NIPAM-co-HEMIN)/ALG-EDA/AgNP composite system is effective against E. coli and S. aureus. Additionally, the AgNP composite exhibits low cellular toxicity in NIH3T3 and CT-2A cell lines. The wounds in diabetic mice treated with the composite system healed in <12 days, and the composite system accelerated the healing process by increasing collagen synthesis. In conclusion, the biocomposite reported herein is highly promising for repairing diabetic skin wounds and treating infections caused by bacterial microbes.

Functional Enhancement of Guar Gum−Based Hydrogel by Polydopamine and Nanocellulose

The development of green, biomedical hydrogels using natural polymers is of great significance. From this viewpoint, guar gum (GG) has been widely used for hydrogel preparation; however, its mechanical strength and adhesion often cannot satisfy the biomedical application. Therefore, in the present study, gelatin and a cellulose nanocrystal (CNC) were first applied to overcome the defects of guar gum hydrogel. Dopamine was self−polymerized into polydopamine (PDA) on the gelatin chain at alkaline condition, and gelatin−polydopamine (Gel−PDA) further cross−linked with guar gum and CNC via the borate−didiol bond, intramolecular Schiff base reaction, and Michael addition. CNC not only interacted with guar gum using borate chemistry but also acted as a mechanical reinforcer. The obtained Gel−PDA+GG+CNC hydrogel had an excellent self−healing capacity, injectability, and adhesion due to the catechol groups of PDA. Moreover, dopamine introduction caused a significant increase in the anti−oxidant activity. This hydrogel was cyto− and hemo−compatible, which implies a potential usage in the medical field.

Thermo-Responsive Injectable Hydrogels Formed by Self-Assembly of Alginate-Based Heterograft Copolymers

Polysaccharide-based graft copolymers bearing thermo-responsive grafting chains, exhibiting LCST, have been designed to afford thermo-responsive injectable hydrogels. The good performance of the hydrogel requires control of the critical gelation temperature, Tgel. In the present article, we wish to show an alternative method to tune Tgel using an alginate-based thermo-responsive gelator bearing two kinds of grafting chains (heterograft copolymer topology) of P(NIPAM86-co-NtBAM14) random copolymers and pure PNIPAM, differing in their lower critical solution temperature (LCST) about 10 °C. Interestingly, the Tgel of the heterograft copolymer is controlled from the overall hydrophobic content, NtBAM, of both grafts, implying the formation of blended side chains in the crosslinked nanodomains of the formed network. Rheological investigation of the hydrogel showed excellent responsiveness to temperature and shear. Thus, a combination of shear-thinning and thermo-thickening effects provides the hydrogel with injectability and self-healing properties, making it a good candidate for biomedical applications.

Recent advances in hydrogels for preventing tumor recurrence

Malignant tumors remain a high-risk disease with high mortality all over the world. Among all the cancer treatments, surgery is the primary approach in the clinical treatment of tumors. However, tumor invasion and metastasis pose challenges for complete tumor resection, accompanied by high recurrence rates and reduced quality of life. Hence, there is an urgent need to explore effective adjuvant therapies to prevent postoperative tumor recurrence and relieve the pain of the patients. Nowadays, the booming local drug delivery systems which can be applied as postoperative adjuvant therapies have aroused people's attention, along with the rapid development in the pharmaceutical and biological materials fields. Hydrogels are a kind of unique carrier with prominent biocompatibility among a variety of biomaterials. Due to their high similarity to human tissues, hydrogels which load drugs/growth factors can prevent rejection reactions and promote wound healing. In addition, hydrogels are able to cover the postoperative site and maintain sustained drug release for the prevention of tumor recurrence. In this review, we survey controlled drug delivery hydrogels such as implantable, injectable and sprayable formulations and summarize the properties required for hydrogels used as postoperative adjuvant therapies. The opportunities and challenges in the design and clinical application of these hydrogels are also elaborated.

Orthogonally crosslinked alginate conjugate thermogels with potential for cell encapsulation

Hydrogels with more than one mode of crosslinking have gained interest due to improved control over hydrogel properties such as mechanical strength using multiple stimuli. In this work, sodium alginate was covalently conjugated onto thermoresponsive polyurethanes to prepare hybrid polymers (EPC-Alg) that are responsive to both temperature and Ca²⁺, forming orthogonally crosslinked hydrogels which are non-toxic to cells. Notably, the crosslinks are fully reversible, allowing for gel strength to be modulated via selective removal of either stimulus, or complete deconstruction of the hydrogel network by removing both stimuli. Higher alginate fractions increased the hydrophilicity and Ca²⁺ response of the EPC-Alg hydrogel, enabling tunable modulation of the thermal stability, stiffness and gelation temperatures. The EPC-Alg hydrogel could sustain protein release for a month and encapsulate neural spheroids with high cell viability after 7-day culture, demonstrating feasibility towards 3D cell encapsulation in cell-based biomedical applications such as cell encapsulation and cell therapy.

Recent advances in conductive hydrogels: classifications, properties, and applications

Hydrogel-based conductive materials for smart wearable devices have attracted increasing attention due to their excellent flexibility, versatility, and outstanding biocompatibility. This review presents the recent advances in multifunctional conductive hydrogels for electronic devices. First, conductive hydrogels with different components are discussed, including pure single network hydrogels based on conductive polymers, single network hydrogels with additional conductive additives (i.e., nanoparticles, nanowires, and nanosheets), double network hydrogels based on conductive polymers, and double network hydrogels with additional conductive additives. Second, conductive hydrogels with a variety of functionalities, including self-healing, super toughness, self-growing, adhesive, anti-swelling, antibacterial, structural color, hydrophobic, anti-freezing, shape memory and external stimulus responsiveness are introduced in detail. Third, the applications of hydrogels in flexible devices are illustrated (i.e., strain sensors, supercapacitors, touch panels, triboelectric nanogenerator, bioelectronic devices, and robot). Next, the current challenges facing hydrogels are summarized. Finally, an imaginative but reasonable outlook is given, which aims to drive further development in the future.

Smart Stimuli-responsive Alginate Nanogels for Drug Delivery Systems and Cancer Therapy: A Review

Nanogels are three-dimensional networks at the nanoscale level that can be fabricated through physical or chemical processes using polymers. These nanoparticles' biocompatibility, notable stability, efficacious drug-loading capacity, and ligand-binding proficiency make them highly suitable for employment as drug-delivery vehicles. In addition, they exhibit the ability to react to both endogenous and exogenous stimuli, which may include factors such as temperature, illumination, pH levels, and a diverse range of other factors. This facilitates the consistent administration of the drug to the intended site. Alginate biopolymers have been utilized to encapsulate anticancer drugs due to their biocompatible nature, hydrophilic properties, and cost-effectiveness. The efficacy of alginate nano gel-based systems in cancer treatment has been demonstrated through multiple studies that endorse their progress toward clinical implementation. This paper comprehensively reviews alginate and its associated systems in drug delivery systems.

Advances in Algin and Alginate-Hybrid Materials for Drug Delivery and Tissue Engineering

In this review, we aim to provide a summary of recent research advancements and applications of algin (i.e., alginic acid) and alginate-hybrid materials (AHMs) in medical fields. Algin/alginate are abundant natural products that are chemically inert and biocompatible, and they have superior gelation properties, good mechanical strengths, and biodegradability. The AHMs have been widely applied in wound dressing, cell culture, tissue engineering, and drug delivery. However, medical applications in different fields require different properties in the AHMs. The drug delivery application requires AHMs to provide optimal drug loading, controlled and targeted drug-releasing, and/or visually guided drug delivery. AHMs for wound dressing application need to have improved mechanical properties, hydrophilicity, cell adhesion, and antibacterial properties. AHMs for tissue engineering need improved mechanical properties that match the target organs, superior cell affinity, and cell loading capacity. Various methods to produce AHMs that meet different needs were summarized. Formulations to form AHMs with improved stability, drug/cell-loading capacity, cell adhesion, and mechanical properties are active research areas. This review serves as a road map to provide insights into the strategies to develop AHMs in medical applications.

Developments on the Smart Hydrogel-Based Drug Delivery System for Oral Tumor Therapy

At present, an oral tumor is usually treated by surgery combined with preoperative or postoperative radiotherapies and chemotherapies. However, traditional chemotherapies frequently result in substantial toxic side effects, including bone marrow suppression, malfunction of the liver and kidneys, and neurotoxicity. As a new local drug delivery system, the smart drug delivery system based on hydrogel can control drug release in time and space, and effectively alleviate or avoid these problems. Environmentally responsive hydrogels for smart drug delivery could be triggered by temperature, photoelectricity, enzyme, and pH. An overview of the most recent research on smart hydrogels and their controlled-release drug delivery systems for the treatment of oral cancer is given in this review. It is anticipated that the local drug release method and environment-responsive benefits of smart hydrogels will offer a novel technique for the low-toxicity and highly effective treatment of oral malignancy.

Thermo-Sensitive Poly (N-isopropylacrylamide-co-polyacrylamide) Hydrogel for pH-Responsive Therapeutic Delivery

Stimuli-response polymeric nanoparticles have emerged as a carrier system for various types of therapeutic delivery. In this study, we prepared a dual pH- and thermo-sensitive copolymer hydrogel (HG) system (PNIPAm-co-PAAm HG), using N-isopropyl acrylamide (NIPAm) and acrylamide (AAm) as comonomers. The synthesized PNIPAm-co-PAAm HG was characterized using various instrumental characterizations. Moreover, the PNIPAm-co-PAAm HG's thermoresponsive phase transition behavior was investigated, and the results showed that the prepared HG responds to temperature changes. In vitro drug loading and release behavior of PNIPAm-co-PAAm HG was investigated using Curcumin (Cur) as the model cargo under different pH and temperature conditions. The PNIPAm-co-PAAm HG showed pH and temperature-responsive drug release behavior and demonstrated about 65% Cur loading efficiency. A nearly complete release of the loaded Cur occurred from the PNIPAm-co-PAAm HG over 4 h at pH 5.5 and 40 °C. The cytotoxicity study was performed on a liver cancer cell line (HepG2 cells), which revealed that the prepared PNIPAm-co-PAAm HG showed good biocompatibility, suggesting that it could be applied as a drug delivery carrier. Moreover, the in vitro cytocompatibility test (MTT assay) results revealed that the PNIPAm-co-PAAm HG is biocompatible. Therefore, the PNIPAm-co-PAAm HG has the potential to be useful in the delivery of drugs in solid tumor-targeted therapy.

Nanomaterials based on thermosensitive polymer in biomedical field

The progress of nanotechnology enables us to make use of the special properties of materials on the nanoscale and open up many new fields of biomedical research. Among them, thermosensitive nanomaterials stand out in many biomedical fields because of their “intelligent” behavior in response to temperature changes. However, this article mainly reviews the research progress of thermosensitive nanomaterials, which are popular in biomedical applications in recent years. Here, we simply classify the thermally responsive nanomaterials according to the types of polymers, focusing on the mechanisms of action and their advantages and potential. Finally, we deeply investigate the applications of thermosensitive nanomaterials in drug delivery, tissue engineering, sensing analysis, cell culture, 3D printing, and other fields and probe the current challenges and future development prospects of thermosensitive nanomaterials.

Recent advances in polysaccharide-based in situ forming hydrogels

Polysaccharides comprise an important class of natural polymers; they are abundant, diverse, polyfunctional, typically benign, and are biodegradable. Using polysaccharides to design in situ forming hydrogels is an attractive and important field of study since many polysaccharide-based hydrogels exhibit desirable characteristics including self-healing, responsiveness to environmental stimuli, and injectability. These characteristics are particularly useful for biomedical applications. This review will discuss recent discoveries in polysaccharide-based in situ forming hydrogels, including network architecture designs, curing mechanisms, physical and chemical properties, and potential applications.

Facile Construction of a Two-in-One Injectable Micelleplex-Loaded Thermogel System for the Prolonged Delivery of Plasmid DNA

Nanoparticle-hydrogel systems have recently emerged as a class of interesting hybrid materials with immense potential for several biomedical applications. Remarkably, the incorporation of nanoparticles into a hydrogel may yield synergistic benefits lacking in a singular system. However, most synthetic strategies require laborious steps to achieve the system, severely restricting the process of translational research. Herein, a facile strategy to access a two-in-one system comprising two distinct polyurethane (PU)-based micellar systems is demonstrated and applied as a novel sustained gene delivery platform, where the two PUs are synthesized similarly but with slightly different compositions. One PU forms cationic micelles that complex with plasmid DNA (pDNA), which are loaded into a thermogel formed by another PU micellar system for the prolonged release of pDNA micelleplexes. Specifically, a thermogelling multiblock PU copolymer (denoted as EPH) was synthesized via the step-growth polymerization of poly(ethylene glycol), poly(propylene glycol), and poly(3-hydroxybutyrate). By further introducing a cationic extender, 3-(dimethylamino)-1,2-propanediol, into the reaction feed, a series of cationic PUs (denoted as EPHD) with varying compositions were obtained. The EPHDs formed positively charged micelles in aqueous solutions, efficiently condensed pDNA into nano-sized micelleplexes (<200 nm) at optimized w/w ratios, and mediated transient green fluorescence protein expression in HEK293T cells at 48 h post-transfection. On the other hand, aqueous EPH solution (4 wt %) was injectable at 4 °C and rapidly gelled upon heating to 37 °C to form a stable hydrogel depot. EPHD/pDNA micelleplexes were easily loaded into EPH by mixing the solutions at 4 °C, before heating to 37 °C, leading to the resultant hydrogel system. The in vitro release study revealed that while free pDNA loaded in the thermogel was completely released in 2 weeks, the release of EPHD/pDNA micelleplexes was prolonged to at least 28 days, suggesting substantial micelleplex-hydrogel interactions. Intact, bioactive, and noncytotoxic EPHD/pDNA micelleplexes in the release media were proved by gel retardation, in vitro gene transfection, and CCK-8 cytotoxicity assay results, respectively. Collectively, this work presents a simple approach to achieving and optimizing a novel two-in-one nanoparticle-hydrogel system for the prolonged delivery of pDNA and may be promising for long-term gene delivery applications.