Ingestible hydrogel device

Engineered Shape-Morphing Transitions in Hydrogels Through Suspension Bath Printing of Temperature-Responsive Granular Hydrogel Inks

4D printing of hydrogels is an emerging technology used to fabricate shape-morphing soft materials that are responsive to external stimuli for use in soft robotics and biomedical applications. Soft materials are technically challenging to process with current 4D printing methods, which limits the design and actuation potential of printed structures. Here, a simple multi-material 4D printing technique is developed that combines dynamic temperature-responsive granular hydrogel inks based on hyaluronic acid, whose actuation is modulated via poly(N-isopropylacrylamide) crosslinker design, with granular suspension bath printing that provides structural support during and after the printing process. Granular hydrogels are easily extruded upon jamming due to their shear-thinning properties and their porous structure enables rapid actuation kinetics (i.e., seconds). Granular suspension baths support responsive ink deposition into complex patterns due to shear-yielding to fabricate multi-material objects that can be post-crosslinked to obtain anisotropic shape transformations. Dynamic actuation is explored by varying printing patterns and bath shapes, achieving complex shape transformations such as 'S'-shaped and hemisphere structures. Furthermore, stepwise actuation is programmed into multi-material structures by using microgels with varied transition temperatures. Overall, this approach offers a simple method to fabricate programmable soft actuators with rapid kinetics and precise control over shape morphing.

Molecular Chain Rearrangement-Induced In Situ Formation of Nanofibers for Improving the Strength and Toughness of Hydrogels

Although poly(vinyl alcohol) (PVA) hydrogel has high elasticity and is suitable for cartilage tissue engineering, it is difficult to have both high strength and toughness. In this study, a simple and universal strategy is proposed to prepare strong and tough PVA hydrogels by in situ forming nanofibers on the original network structure induced by a molecular chain rearrangement. Quenching-tempering alteratively in ethanol and water several times is carried out to strengthen PVA hydrogels (PVA-Etn hydrogels) due to the advantages of noncovalent bonds in adjustability and reversibility. The results show that, after three quenching-tempering cycles, PVA-Et3 hydrogel with water content up to 79 wt % shows comprehensive improved mechanical properties. The compression modulus, tensile modulus, fracture strength, tensile strain, and tear energy of the PVA-Et3 hydrogel are 270, 250, 260, 130, and 180% of the initial PVA hydrogel, respectively. The improved mechanical properties of the PVA-Et3 hydrogel are attributed to the strong cross-linked PVA chains and hydrogen bond-reinforced nanofibers. This study not only provides a simple and efficient solution for the preparation of strong and tough polymer scaffolds in tissue engineering but also provides new insights for understanding the mechanism of improving the mechanical properties of polymer hydrogels by adjusting the molecular structure.

Hybrid Hydrogel-Magnet Actuated Capsule for Automatic Gut Microbiome Sampling

OBJECTIVE

Non-invasive, pill-sized capsules can provide intestinal fluid sampling to easily retrieve site-specific gut microbiome samples for studies in nutrition and chronic diseases. However, capsules with both automatic sampling and active locomotion are uncommon due to limited onboard space. This paper presents a novel hybrid hydrogel-magnet actuated capsule featuring: i) pH-responsive hydrogels that will automatically trigger fluid sampling at an environmental pH of 6 and ii) active locomotion by an external rotating magnetic field.

METHOD

Two capsule designs were fabricated (Design A: 31 μL sampling volume with dimensions 8 mm × 19 mm, Design B: 41 μL sampling volume with dimensions 8 mm × 21 mm). They were immersed in simulated gastric (pH = 1.2) and simulated intestinal fluid (pH = 6.8) to test for automatic intestinal fluid sampling. An external rotating magnetic field was applied to test for active locomotion. Finally, seal tests were performed to demonstrate sample contamination mitigation.

RESULTS

Preliminary experiments showed that sampling occurred quickly and automatically in simulated intestinal fluid at 6-15 hours, active locomotion via rotation, rolling, and tumbling were possible at magnetic field magnitudes 10 mT, oil piston seals were better at mitigating sample contamination than water piston seals, and minimum o-ring seal pressures limits of 1.95 and 1.69 kPa for Design A and B respectively were sufficient against intra-abdominal pressures.

SIGNIFICANCE

This work presents the ability to impart capsule multi-functionality in a compact manner without onboard electronics or external triggering for sampling.

Flexible and wearable electronic systems based on 2D hydrogel composites

Flexible electronics is a rapidly developing field of study, which integrates many other fields, including materials science, biology, chemistry, physics, and electrical engineering. Despite their vast potential, the widespread utilization of flexible electronics is hindered by several constraints, including elevated Young's modulus, inadequate biocompatibility, and diminished responsiveness. Therefore, it is necessary to develop innovative materials aimed at overcoming these hurdles and catalysing their practical implementation. In these materials, hydrogels are particularly promising owing to their three-dimensional crosslinked hydrated polymer networks and exceptional properties, positioning them as leading candidates for the development of future flexible electronics.

Drinkable in situ-forming tough hydrogels for gastrointestinal therapeutics

Pills are a cornerstone of medicine but can be challenging to swallow. While liquid formulations are easier to ingest, they lack the capacity to localize therapeutics with excipients nor act as controlled release devices. Here we describe drug formulations based on liquid in situ-forming tough (LIFT) hydrogels that bridge the advantages of solid and liquid dosage forms. LIFT hydrogels form directly in the stomach through sequential ingestion of a crosslinker solution of calcium and dithiol crosslinkers, followed by a drug-containing polymer solution of alginate and four-arm poly(ethylene glycol)-maleimide. We show that LIFT hydrogels robustly form in the stomachs of live rats and pigs, and are mechanically tough, biocompatible and safely cleared after 24 h. LIFT hydrogels deliver a total drug dose comparable to unencapsulated drug in a controlled manner, and protect encapsulated therapeutic enzymes and bacteria from gastric acid-mediated deactivation. Overall, LIFT hydrogels may expand access to advanced therapeutics for patients with difficulty swallowing.

Oral administration microrobots for drug delivery

Oral administration is the most simple, noninvasive, convenient treatment. With the increasing demands on the targeted drug delivery, the traditional oral treatment now is facing some challenges: 1) biologics how to implement the oral treatment and ensure the bioavailability is not lower than the subcutaneous injections; 2) How to achieve targeted therapy of some drugs in the gastrointestinal tract? Based on these two issues, drug delivery microrobots have shown great application prospect in oral drug delivery due to their characteristics of flexible locomotion or driven ability. Therefore, this paper summarizes various drug delivery microrobots developed in recent years and divides them into four categories according to different driving modes: magnetic-controlled drug delivery microrobots, anchored drug delivery microrobots, self-propelled drug delivery microrobots and biohybrid drug delivery microrobots. As oral drug delivery microrobots involve disciplines such as materials science, mechanical engineering, medicine, and control systems, this paper begins by introducing the gastrointestinal barriers that oral drug delivery must overcome. Subsequently, it provides an overview of typical materials involved in the design process of oral drug delivery microrobots. To enhance readers' understanding of the working principles and design process of oral drug delivery microrobots, we present a guideline for designing such microrobots. Furthermore, the current development status of various types of oral drug delivery microrobots is reviewed, summarizing their respective advantages and limitations. Finally, considering the significant concerns regarding safety and clinical translation, we discuss the challenges and prospections of clinical translation for various oral drug delivery microrobots presented in this paper, providing corresponding suggestions for addressing some existing challenges.

Millimeter-scale soft capsules for sampling liquids in fluid-filled confined spaces

Sampling liquids in small and confined spaces to retrieve chemicals and microbiomes could enable minimally invasive monitoring human physiological conditions for understanding disease development and allowing early screening. However, existing tools are either invasive or too large for sampling liquids in tortuous and narrow spaces. Here we report a fundamental liquid sampling mechanism that enables millimeter-scale soft capsules for sampling liquids in confined spaces. The miniature capsule is enabled by flexible magnetic valves and superabsorbent polymer, fully wirelessly controlled for on-demand fluid sampling. A group of miniature capsules could navigate in fluid-filled and confined spaces safely using a rolling locomotion. The integration of on-demand triggering, sampling, and sealing mechanism and the agile group locomotion allows us to demonstrate precise control of the soft capsules, navigating and sampling body fluids in a phantom and animal organ ex vivo, guided by ultrasound and x-ray medical imaging. The proposed mechanism and wirelessly controlled devices spur the next-generation technologies for minimally invasive disease diagnosis.

Pericardial Delivery of Sodium Alginate-Infusible Extracellular Matrix Composite Hydrogel Promotes Angiogenesis and Intercellular Electrical Conduction after Myocardial Infarction

Injectable extracellular matrix (iECM) is a versatile biological material with beneficial properties such as good degradability, promotion of cell survival, immunomodulation, and facilitation of vascular formation. However, intravenous injection of iECM faces challenges like a short retention time in vivo and low concentration at the lesion site. To address these issues, we prepared a composite hydrogel composed of sodium alginate and iECM and administered it via intrapericardial injection, forming a structure akin to cardiac patches within the pericardium. Compared with intramyocardial injection, intrapericardial injection avoids direct myocardial injury and ectopic tumor formation, offering less invasiveness and better biocompatibility. This study demonstrates that the sodium alginate/infusible extracellular matrix (SA/iECM) composite hydrogel can effectively prolong the local retention time of iECM in the heart, enhance electrical conduction between cardiomyocytes, promote angiogenesis at ischemic myocardial sites, inhibit apoptosis in the infarcted region, mitigate left ventricular remodeling postmyocardial infarction (MI), and improve cardiac function after infarction. Precise coordination of cardiomyocyte contraction and relaxation depends on the rhythmic occurrence of calcium-dependent action potentials. Cardiac dysfunction is partially attributed to the disruption of the excitation-contraction coupling (ECC) mechanism, which is associated with prolonged intracellular Ca2+ transients and alterations in contraction and relaxation Ca2+ levels. Our results show that the SA/iECM composite hydrogel improves electrical conduction, as evidenced by increased Cx43 expression and enhanced intercellular electrical connectivity. This research establishes that intrapericardial injection of a SA/iECM composite hydrogel is a safe and effective treatment modality, providing a theoretical basis for the use of biomaterials in MI therapy.

An ingestible, battery-free, tissue-adhering robotic interface for non-invasive and chronic electrostimulation of the gut

Ingestible electronics have the capacity to transform our ability to effectively diagnose and potentially treat a broad set of conditions. Current applications could be significantly enhanced by addressing poor electrode-tissue contact, lack of navigation, short dwell time, and limited battery life. Here we report the development of an ingestible, battery-free, and tissue-adhering robotic interface (IngRI) for non-invasive and chronic electrostimulation of the gut, which addresses challenges associated with contact, navigation, retention, and powering (C-N-R-P) faced by existing ingestibles. We show that near-field inductive coupling operating near 13.56 MHz was sufficient to power and modulate the IngRI to deliver therapeutically relevant electrostimulation, which can be further enhanced by a bio-inspired, hydrogel-enabled adhesive interface. In swine models, we demonstrated the electrical interaction of IngRI with the gastric mucosa by recording conductive signaling from the subcutaneous space. We further observed changes in plasma ghrelin levels, the "hunger hormone," while IngRI was activated in vivo, demonstrating its clinical potential in regulating appetite and treating other endocrine conditions. The results of this study suggest that concepts inspired by soft and wireless skin-interfacing electronic devices can be applied to ingestible electronics with potential clinical applications for evaluating and treating gastrointestinal conditions.

Ultra-Tough Graphene Oxide/DNA 2D Hydrogel with Intrinsic Sensing and Actuation Functions

Hydrogel devices with mechanical toughness and tunable functionalities are highly desirable for practical long-term applications such as sensing and actuation elements for soft robotics. However, existing hydrogels have poor mechanical properties, slow rates of response, and low functionality. In this work, two-dimensional hydrogel actuators are proposed and formed on the self-assembly of graphene oxide (GO) and deoxynucleic acid (DNA). The self-assembly process is driven by the GO-induced transition of double stranded DNA (dsDNA) into single stranded DNA (ssDNA). Thus, the hydrogel's structural unit consists of two layers of GO covered by ssDNA and a layer of dsDNA in between. Such heterogeneous architectures stabilized by multiple hydrogen bondings have Young's modulus of up to 10 GPa and rapid swelling rates of 4.0 × 10-3 to 1.1 × 10-2 s-1, which surpasses most types of conventional hydrogels. It is demonstrated that the GO/DNA hydrogel actuators leverage the unique properties of these two materials, making them excellent candidates for various applications requiring sensing and actuation functions, such as artificial skin, wearable electronics, bioelectronics, and drug delivery systems.

Edible hydrogel with dual network structure for weight management

Obesity, a global health crisis, is fueled by shifts in behavior and environmental factors, notably increased consumption of energy-dense processed foods and inadequate dietary fiber. Traditional weight loss methods pose safety challenges. Sodium carboxymethylcellulose (CMC), a promising dietary fiber supplement, aids weight management. However, CMC-based hydrogels have mechanical weaknesses and poor gastrointestinal retention. A new dual-network structured hydrogel here was introduced to address these issues, maintaining volume and elasticity in the digestive system without adding calories, reducing caloric density, and enhancing food elasticity for prolonged satiety. The study assessed four distinct hydrogels, analyzing their mechanical characteristics under simulated gastrointestinal conditions and biomimetic digestion to identify promising options for clinical development. This dual-network hydrogel exhibits a mechanical strength up to 100 times that of the original gel, while its swelling rate throughout the digestion process is approximately twice that of the original gel. This offers a potential solution for obesity management, providing sustained satiety and addressing the mechanical deficiencies of current hydrogels within the digestive system.

Multifaceted Hydrogel Scaffolds: Bridging the Gap between Biomedical Needs and Environmental Sustainability

Hydrogels are dynamically evolving 3D networks composed of hydrophilic polymer scaffolds with significant applications in the healthcare and environmental sectors. Notably, protein-based hydrogels mimic the extracellular matrix, promoting cell adhesion. Further enhancing cell proliferation within these scaffolds are matrix-metalloproteinase-triggered amino acid motifs. Integration of cell-friendly modules like peptides and proteins expands hydrogel functionality. These exceptional properties position hydrogels for diverse applications, including biomedicine, biosensors, environmental remediation, and the food industry. Despite significant progress, there is ongoing research to optimize hydrogels for biomedical and environmental applications further. Engineering novel hydrogels with favorable characteristics is crucial for regulating tissue architecture and facilitating ecological remediation. This review explores the synthesis, physicochemical properties, and biological implications of various hydrogel types and their extensive applications in biomedicine and environmental sectors. It elaborates on their potential applications, bridging the gap between advancements in the healthcare sector and solutions for environmental issues.

Designing Tough Hydrogel Shells for Glucose Sensing

Conventional hydrogel microcapsules often suffer from inadequate mechanical stability, hindering their use. Here, water-cored double-network (DN) hydrogel shells are designed, formed by polyacrylamide and calcium alginate networks using triple-emulsion templates. These DN hydrogel shells offer robust mechanical stability, optical transparency, and a precisely-defined cut-off threshold. The feasibility of this platform is demonstrated through the development of a fluorometric glucose sensor. Glucose oxidase is enclosed within the water core, while a pH-responsive fluorescent dye is incorporated into the DN shells. Glucose diffuses into the core through the DN shells, where the glucose oxidase converts glucose into gluconic acid, leading to pH reduction and a subsequent decrease in fluorescence intensity of DN shells. Additionally, the pH-sensitive colorant dissolved in the medium enables visual pH assessment. Thus, glucose levels can be determined using both fluorometric and colorimetric methods. Notably, the DN shells exhibit exceptional stability, enduring intense mechanical stress and cycles of drying and rehydration without leakage. Moreover, the DN shells act as effective barriers, safeguarding glucose oxidase against proteolysis by large disruptive proteins, like pancreatin. This versatile DN shell platform extends beyond glucose oxidase encapsulation, serving as a foundation for various capsule sensors utilizing enzymes and heterogeneous catalysts.

Natural Underwater Bioadhesive Offering Cohesion Modulation via Hydrogen Bond Disruptor: A Highly Injectable and in Vivo Stable Remedy for Gastric Ulcer Resolution

Injectable bioadhesives are attractive for managing gastric ulcers through minimally invasive procedures. However, the formidable challenge is to develop bioadhesives that exhibit high injectability, rapidly adhere to lesion tissues with fast gelation, provide reliable protection in the harsh gastric environment, and simultaneously ensure stringent standards of biocompatibility. Here, a natural bioadhesive with tunable cohesion is developed based on the facile and controllable gelation between silk fibroin and tannic acid. By incorporating a hydrogen bond disruptor (urea or guanidine hydrochloride), the inherent network within the bioadhesive is disturbed, inducing a transition to a fluidic state for smooth injection (injection force <5 N). Upon injection, the fluidic bioadhesive thoroughly wets tissues, while the rapid diffusion of the disruptor triggers instantaneous in situ gelation. This orchestrated process fosters the formed bioadhesive with durable wet tissue affinity and mechanical properties that harmonize with gastric tissues, thereby bestowing long-lasting protection for ulcer healing, as evidenced through in vitro and in vivo verification. Moreover, it can be conveniently stored (≥3 m) postdehydration. This work presents a promising strategy for designing highly injectable bioadhesives utilizing natural feedstocks, avoiding any safety risks associated with synthetic materials or nonphysiological gelation conditions, and offering the potential for minimally invasive application.

A Stable and Sensitive Engineering Bacterial Sensor via Physical Biocontainment and Two-Stage Signal Amplification

Although engineering bacterial sensors have outstanding advantages in reflecting the actual bioavailability and continuous monitoring of pollutants, the potential escape risk of engineering microorganisms and lower detection sensitivity have always been one of the biggest challenges limiting their wider application. In this study, a core-shell hydrogel bead with functionalized silica as the core and alginate-polyacrylamide as the shell have been developed not only to realize zero escape of engineered bacteria but also to maintain cell activity in harsh environments, such as extremely acidic/alkaline pH, high salt concentration, and strong pressure. Particularly, after combining the selective preconcentration toward pollutants by functionalized core and the positive feedback signal amplification of engineering bacteria, biosensors have realized two-stage signal amplification, significantly improving the detection sensitivity and reducing the detection limit. In addition, this strategy was actually applied to the detection of As(III) and As(V) coexisting in environmental samples, and the detection sensitivity was increased by 3.23 and 4.39 times compared to sensors without signal amplification strategy, respectively, and the detection limits were as low as 0.39 and 0.86 ppb, respectively.

Strong, tough and anisotropic bioinspired hydrogels

Soft materials are widely used in tissue engineering, soft robots, wearable electronics, etc. However, it remains a challenge to fabricate soft materials, such as hydrogels, with both high strength and toughness that are comparable to biological tissues. Inspired by the anisotropic structure of biological tissues, a novel solvent-exchange-assisted wet-stretching strategy is proposed to prepare anisotropic polyvinyl alcohol (PVA) hydrogels by tuning the macromolecular chain movement and optimizing the polymer network. The reinforcing and toughening mechanisms are found to be "macromolecule crystallization and nanofibril formation". These hydrogels exhibit excellent mechanical properties, such as extremely high fracture stress (12.8 ± 0.7 MPa) and fracture strain (1719 ± 77%), excellent modulus (4.51 ± 0.76 MPa), high work of fracture (134.47 ± 9.29 MJ m-3), and fracture toughness (305.04 kJ m-2) compared with other strong hydrogels and even natural tendons. In addition, excellent conductivity, strain sensing capability, water retention, freezing resistance, swelling resistance, and biocompatibility can also be achieved. This work provides a new and effective method to fabricate multifunctional anisotropic hydrogels with high tunable strength and toughness with potential applications in the fields of regenerative medicine, flexible sensors, and soft robotics.

Control of polymers' amorphous-crystalline transition enables miniaturization and multifunctional integration for hydrogel bioelectronics

Soft bioelectronic devices exhibit motion-adaptive properties for neural interfaces to investigate complex neural circuits. Here, we develop a fabrication approach through the control of metamorphic polymers' amorphous-crystalline transition to miniaturize and integrate multiple components into hydrogel bioelectronics. We attain an about 80% diameter reduction in chemically cross-linked polyvinyl alcohol hydrogel fibers in a fully hydrated state. This strategy allows regulation of hydrogel properties, including refractive index (1.37-1.40 at 480 nm), light transmission (>96%), stretchability (139-169%), bending stiffness (4.6 ± 1.4 N/m), and elastic modulus (2.8-9.3 MPa). To exploit the applications, we apply step-index hydrogel optical probes in the mouse ventral tegmental area, coupled with fiber photometry recordings and social behavioral assays. Additionally, we fabricate carbon nanotubes-PVA hydrogel microelectrodes by incorporating conductive nanomaterials in hydrogel for spontaneous neural activities recording. We enable simultaneous optogenetic stimulation and electrophysiological recordings of light-triggered neural activities in Channelrhodopsin-2 transgenic mice.

Silk Fibroin-Based Coatings for Pancreatin-Dependent Drug Delivery

Triggerable coatings, such as pH-responsive polymethacrylate copolymers, can be used to protect the active pharmaceutical ingredients contained within oral solid dosage forms from the acidic gastric environment and to facilitate drug delivery directly to the intestine. However, gastrointestinal pH can be highly variable, which can reduce delivery efficiency when using pH-responsive drug delivery technologies. We hypothesized that biomaterials susceptible to proteolysis could be used in combination with other triggerable polymers to develop novel enteric coatings. Bioinformatic analysis suggested that silk fibroin is selectively degradable by enzymes in the small intestine, including chymotrypsin, but resilient to gastric pepsin. Based on the analysis, we developed a silk fibroin-polymethacrylate copolymer coating for oral dosage forms. In vitro and in vivo studies demonstrated that capsules coated with this novel silk fibroin formulation enable pancreatin-dependent drug release. We believe that this novel formulation and extensions thereof have the potential to produce more effective and personalized oral drug delivery systems for vulnerable populations including patients that have impaired and highly variable intestinal physiology.

Construction methods and biomedical applications of PVA-based hydrogels

Polyvinyl alcohol (PVA) hydrogel is favored by researchers due to its good biocompatibility, high mechanical strength, low friction coefficient, and suitable water content. The widely distributed hydroxyl side chains on the PVA molecule allow the hydrogels to be branched with various functional groups. By improving the synthesis method and changing the hydrogel structure, PVA-based hydrogels can obtain excellent cytocompatibility, flexibility, electrical conductivity, viscoelasticity, and antimicrobial properties, representing a good candidate for articular cartilage restoration, electronic skin, wound dressing, and other fields. This review introduces various preparation methods of PVA-based hydrogels and their wide applications in the biomedical field.

An Antidehydration Hydrogel Based on Zwitterionic Oligomers for Bioelectronic Interfacing

Hydrogels are ideal interfacing materials for on-skin healthcare devices, yet their susceptibility to dehydration hinders their practical use. While incorporating hygroscopic metal salts can prevent dehydration and maintain ionic conductivity, concerns arise regarding metal toxicity due to the passage of small ions through the skin barrier. Herein, an antidehydration hydrogel enabled by the incorporation of zwitterionic oligomers into its network is reported. This hydrogel exhibits exceptional water retention properties, maintaining ≈88% of its weight at 40% relative humidity, 25 °C for 50 days and about 84% after being heated at 50 °C for 3 h. Crucially, the molecular weight design of the embedded oligomers prevents their penetration into the epidermis, as evidenced by experimental and molecular simulation results. The hydrogel allows stable signal acquisition in electrophysiological monitoring of humans and plants under low-humidity conditions. This research provides a promising strategy for the development of epidermis-safe and biocompatible antidehydration hydrogel interfaces for on-skin devices.

Pain-free oral delivery of biologic drugs using intestinal peristalsis-actuated microneedle robots

Biologic drugs hold immense promise for medical treatments, but their oral delivery remains a daunting challenge due to the harsh digestive environment and restricted gastrointestinal absorption. Here, inspired by the porcupinefish's ability to inflate itself and deploy its spines for defense, we proposed an intestinal microneedle robot designed to absorb intestinal fluids for rapid inflation and inject drug-loaded microneedles into the insensate intestinal wall for drug delivery. Upon reaching the equilibrium volume, the microneedle robot leverages rhythmic peristaltic contraction for mucosa penetration. The robot's barbed microneedles can then detach from its body during peristaltic relaxation and retain in the mucosa for drug releasing. Extensive in vivo experiments involving 14 minipigs confirmed the effectiveness of the intestinal peristalsis for microrobot actuation and demonstrated comparable insulin delivery efficacy to subcutaneous injection. The ingestible peristalsis-actuated microneedle robots may transform the oral administration of biologic drugs that primary relies on parenteral injection currently.

Hydrogel Breakthroughs in Biomedicine: Recent Advances and Implications

OBJECTIVE

The objective of this review is to present a succinct summary of the latest advancements in the utilization of hydrogels for diverse biomedical applications, with a particular focus on their revolutionary impact in augmenting the delivery of drugs, tissue engineering, along with diagnostic methodologies.

METHODS

Using a meticulous examination of current literary works, this review systematically scrutinizes the nascent patterns in applying hydrogels for biomedical progress, condensing crucial discoveries to offer a comprehensive outlook on their ever-changing importance.

RESULTS

The analysis presents compelling evidence regarding the growing importance of hydrogels in biomedicine. It highlights their potential to significantly enhance drug delivery accuracy, redefine tissue engineering strategies, and advance diagnostic techniques. This substantiates their position as a fundamental element in the progress of modern medicine.

CONCLUSION

In summary, the constantly evolving advancement of hydrogel applications in biomedicine calls for ongoing investigation and resources, given their diverse contributions that can revolutionize therapeutic approaches and diagnostic methods, thereby paving the way for improved patient well-being.

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.

Intestinal retentive systems - recent advances and emerging approaches

Intestinal retentive devices (IRDs) are devices designed to anchor within the lumen of the intestines for long-term residence in the gastrointestinal tract. IRDs can enable impactful medical device technologies including sustained oral drug delivery systems, indwelling sensors, or real-time diagnostics. The design and testing of IRDs present a myriad of challenges, including precise deployment of the device at desired intestinal locations, secure anchoring within the gastrointestinal tract to allow for natural function, and safe removal of the IRD at user-defined times. Advancing the state-of-the-art of IRD is an interdisciplinary effort that requires innovations such as new materials, novel anchoring mechanisms, and medical device design with consistent input from clinical practitioners and end-users. This perspective briefly reviews the current state-of-the-art for IRDs and charts a path forward to inform the design of future concepts. Specifically, this article will highlight materials, retention mechanisms, and test beds to measure the efficacy of IRDs and their mechanisms. Finally, potential synergies between IRD and other medical device technologies are presented to identify future opportunities.

Recent advances in nano- and micro-scale carrier systems for controlled delivery of vaccines

Vaccines provide substantial safety against infectious diseases, saving millions of lives each year. The recent COVID-19 pandemic highlighted the importance of vaccination in providing mass-scale immunization against outbreaks. However, the delivery of vaccines imposes a unique set of challenges due to their large molecular size and low room temperature stability. Advanced biomaterials and delivery systems such as nano- and mciro-scale carriers are becoming critical components for successful vaccine development. In this review, we provide an updated overview of recent advances in the development of nano- and micro-scale carriers for controlled delivery of vaccines, focusing on carriers compatible with nucleic acid-based vaccines and therapeutics that emerged amid the recent pandemic. We start by detailing nano-scale delivery systems, focusing on nanoparticles, then move on to microscale systems including hydrogels, microparticles, and 3D printed microneedle patches. Additionally, we delve into emerging methods that move beyond traditional needle-based applications utilizing innovative delivery systems. Future challenges for clinical translation and manufacturing in this rapidly advancing field are also discussed.

Biomimetic superabsorbent hydrogel acts as a gut protective dynamic exoskeleton improving metabolic parameters and expanding A. muciniphila

The rising prevalence of obesity and metabolic disorders worldwide highlights the urgent need to find new long-term and clinically meaningful weight-loss therapies. Here, we evaluate the therapeutic potential and the mechanism of action of a biomimetic cellulose-based oral superabsorbent hydrogel (OSH). Treatment with OSH exerts effects on intestinal tissue and gut microbiota composition, functioning like a protective dynamic exoskeleton. It protects from gut barrier permeability disruption and induces rapid and consistent changes in the gut microbiota composition, specifically fostering Akkermansia muciniphila expansion. The mechanobiological, physical, and chemical structures of the gel are required for A. muciniphila growth. OSH treatment induces weight loss and reduces fat accumulation, in both preventative and therapeutic settings. OSH usage also prevents liver steatosis, immune infiltration, and fibrosis, limiting the progression of non-alcoholic fatty liver disease. Our work shows the potential of using OSH as a non-systemic mechanobiological approach to treat metabolic syndrome and its comorbidities.

Tailoring the Swelling-Shrinkable Behavior of Hydrogels for Biomedical Applications

Hydrogels with tailor-made swelling-shrinkable properties have aroused considerable interest in numerous biomedical domains. For example, as swelling is a key issue for blood and wound extrudates absorption, the transference of nutrients and metabolites, as well as drug diffusion and release, hydrogels with high swelling capacity have been widely applicated in full-thickness skin wound healing and tissue regeneration, and drug delivery. Nevertheless, in the fields of tissue adhesives and internal soft-tissue wound healing, and bioelectronics, non-swelling hydrogels play very important functions owing to their stable macroscopic dimension and physical performance in physiological environment. Moreover, the negative swelling behavior (i.e., shrinkage) of hydrogels can be exploited to drive noninvasive wound closure, and achieve resolution enhancement of hydrogel scaffolds. In addition, it can help push out the entrapped drugs, thus promote drug release. However, there still has not been a general review of the constructions and biomedical applications of hydrogels from the viewpoint of swelling-shrinkable properties. Therefore, this review summarizes the tactics employed so far in tailoring the swelling-shrinkable properties of hydrogels and their biomedical applications. And a relatively comprehensive understanding of the current progress and future challenge of the hydrogels with different swelling-shrinkable features is provided for potential clinical translations.

Towards multifunctional robotic pills

Robotic pills leverage the advantages of oral pharmaceutical formulations-in particular, convenient encapsulation, high loading capacity, ease of manufacturing and high patient compliance-as well as the multifunctionality, increasing miniaturization and sophistication of microrobotic systems. In this Perspective, we provide an overview of major innovations in the development of robotic pills-specifically, oral pills embedded with robotic capabilities based on microneedles, microinjectors, microstirrers or microrockets-summarize current progress and applicational gaps of the technology, and discuss its prospects. We argue that the integration of multiple microrobotic functions within oral delivery systems alongside accurate control of the release characteristics of their payload provides a basis for realizing sophisticated multifunctional robotic pills that operate as closed-loop systems.

Activated Metals to Generate Heat for Biomedical Applications

Delivering heat in vivo could enhance a wide range of biomedical therapeutic and diagnostic technologies, including long-term drug delivery devices and cancer treatments. To date, providing thermal energy is highly power-intensive, rendering it oftentimes inaccessible outside of clinical settings. We developed an in vivo heating method based on the exothermic reaction between liquid-metal-activated aluminum and water. After establishing a method for consistent activation, we characterized the heat generation capabilities with thermal imaging and heat flux measurements. We then demonstrated one application of this reaction: to thermally actuate a gastric resident device made from a shape-memory alloy called Nitinol. Finally, we highlight the advantages and future directions for leveraging this novel in situ heat generation method beyond the showcased example.

Konjac glucomannan-based hydrogels with health-promoting effects for potential edible electronics applications: A mini-review

Konjac glucomannan (KGM), a dietary fiber hydrocolloid polysaccharide isolated from Amorphophallus konjac tubers, has potential applications in various fields. However, the use of KGM-based hydrogels has mainly focused on the food, biomedical, and water treatment industries. KGM possesses several health benefits and could be a promising candidate for use in edible electronics. This paper presents the first review of KGM-based hydrogels as edible electronics and their potential health benefits. The paper initially focuses on the health-promoting effects of KGM-based hydrogels, such as prebiotic effects, antiobesity, antioxidant, and antibacterial properties. Then, it discusses the feasible design strategies for KGM-based hydrogels as edible electronics, considering their flexibility, mechanical properties, response to stimuli, degradability aspects, their role as electronic device components, and the retention period of the devices. Finally, this review outlines future directions for developing KGM-based hydrogels for use in edible electronics.

Current Role and Potential of Polymeric Biomaterials in Clinical Obesity Treatment

The rise of obesity and associated fatal diseases has taken a massive toll worldwide. Despite the existing pharmaceuticals and bariatric surgeries, these approaches manifest limited efficacy or accompany various side effects. Therefore, researchers seek to facilitate the prolonged and specific delivery of therapeutics. Or else, to mimic the essential part of "gastric bypass" by physically blocking excessive absorption via less invasive methods. To achieve these goals, polymeric biomaterials have gained tremendous interest recently. They are known for synthesizing hydrogels, microneedle patches, mucoadhesive coatings, polymer conjugates, and so forth. In this Review, we provide insights into the current studies of polymeric biomaterials in the prevention and treatment of obesity, inspiring future improvements in this regime of study.

Untethered shape-changing devices in the gastrointestinal tract

INTRODUCTION

Advances in microfabrication, automation, and computer engineering seek to revolutionize small-scale devices and machines. Emerging trends in medicine point to smart devices that emulate the motility, biosensing abilities, and intelligence of cells and pathogens that inhabit the human body. Two important characteristics of smart medical devices are the capability to be deployed in small conduits, which necessitates being untethered, and the capacity to perform mechanized functions, which requires autonomous shape-changing.

AREAS COVERED

We motivate the need for untethered shape-changing devices in the gastrointestinal tract for drug delivery, diagnosis, and targeted treatment. We survey existing structures and devices designed and utilized across length scales from the macro to the sub-millimeter. These devices range from triggerable pre-stressed thin film microgrippers and spring-loaded devices to shape-memory and differentially swelling structures.

EXPERT OPINION

Recent studies demonstrate that when fully enabled, tether-free and shape-changing devices, especially at sub-mm scales, could significantly advance the diagnosis and treatment of GI diseases ranging from cancer and inflammatory bowel disease (IBD) to irritable bowel syndrome (IBS) by improving treatment efficacy, reducing costs, and increasing medication compliance. We discuss the challenges and possibilities associated with ensuring safe, reliable, and autonomous operation of these smart devices.

Granular Ionogel Particle Inks for 3D Printed Tough and Stretchable Ionotronics

Ionogels have garnered great attention as promising soft conducting materials for the fabrication of flexible energy storage devices, soft actuators, and ionotronics. However, the leakage of the ionic liquids, weak mechanical strength, and poor manufacturability have greatly limited their reliability and applications. Here, we propose a new ionogel synthesis strategy by utilizing granular zwitterionic microparticles to stabilize ionic liquids. The ionic liquids swell the microparticles and physically crosslink microparticles via either electronic interaction or hydrogen bonding. Further introducing a photocurable acrylic monomer enables the fabrication of double-network (DN) ionogels with high stretchability (>600%) and ultrahigh toughness (fracture energy > 10 kJ/m2). The synthesized ionogels exhibit a wide working temperature of -60 to 90 °C. By tuning the crosslinking density of microparticles and physical crosslinking strength of ionogels, we synthesize DN ionogel inks and print them into three-dimensional (3D) motifs. Several ionogel-based ionotronics are 3D printed as demonstrations, including strain gauges, humidity sensors, and ionic skins made of capacitive touch sensor arrays. Via covalently linking ionogels with silicone elastomers, we integrate the ionogel sensors onto pneumatic soft actuators and demonstrate their capacities in sensing large deformation. As our last demonstration, multimaterial direct ink writing is harnessed to fabricate highly stretchable and durable alternating-current electroluminescent devices with arbitrary structures. Our printable granular ionogel ink represents a versatile platform for the future manufacturing of ionotronics.

Hydrogels for Mucosal Drug Delivery

Mucosal tissues are often a desirable site of drug action to treat disease and engage the immune system. However, systemically administered drugs suffer from limited bioavailability in mucosal tissues where technologies to enable direct, local delivery to these sites would prove useful. In this Spotlight on Applications article, we discuss hydrogels as an attractive means for local delivery of therapeutics to address a range of conditions affecting the eye, nose, oral cavity, gastrointestinal, urinary bladder, and vaginal tracts. Considering the barriers to effective mucosal delivery, we provide an overview of the key parameters in the use of hydrogels for these applications. Finally, we highlight recent work demonstrating their use for inflammatory and infectious diseases affecting these tissues.

Utilizing 4D Printing to Design Smart Gastroretentive, Esophageal, and Intravesical Drug Delivery Systems

The breakthrough of 3D printing in biomedical research has paved the way for the next evolutionary step referred to as four dimensional (4D) printing. This new concept utilizes the time as the fourth dimension in addition to the x, y, and z axes with the idea to change the configuration of a printed construct with time usually in response to an external stimulus. This can be attained through the incorporation of smart materials or through a preset smart design. The 4D printed constructs may be designed to exhibit expandability, flexibility, self-folding, self-repair or deformability. This review focuses on 4D printed devices for gastroretentive, esophageal, and intravesical delivery. The currently unmet needs and challenges for these application sites are tried to be defined and reported on published solution concepts involving 4D printing. In addition, other promising application sites that may similarly benefit from 4D printing approaches such as tracheal and intrauterine drug delivery are proposed.

Simultaneous Polymerization Acceleration and Mechanical Enhancement for Printing a Biomimetic PEDOT Adhesive by Coordinative and Orthogonal Ruthenium Photochemistry

Conductive hydrogels are promising material candidates in fields ranging from flexible sensors and electronic skin applications to personalized medical monitoring. However, developing intrinsically conductive polymer hydrogels (ICPHs) with high mechanical properties and excellent printability is still challenging. Here, we introduce a simultaneous polymerization acceleration and mechanical enhancement (SPAME) strategy to construct PEDOT-based ICPHs via the rational design of coordinative and orthogonal ruthenium photochemistry (CORP). This orthogonal photochemistry triggers the oxidative polymerization of EDOT and the coupling of phenols within seconds under blue light irradiation. Benefiting from the bifunctional EDTA-Fe design, the photoreleased Fe(III) accelerated the EDOT polymerization and shortened the preparation time of ICPHs to a few seconds. At the same time, the addition of EDTA-Fe enhanced their mechanical properties, and both the critical strains and maximum stresses of the hydrogel doubled. Furthermore, the introduction of phenol residues in PAA-Ph significantly shortened the gelation time from several minutes to about 7 s. Thus, this fast and controllable CORP chemistry is compatible with standard printing techniques for engineering hydrogels for complex multifunctional structures for multifunctional bioelectronics and devices.

Biocompatible and Long-Term Monitoring Strategies of Wearable, Ingestible and Implantable Biosensors: Reform the Next Generation Healthcare

Sensors enable the detection of physiological indicators and pathological markers to assist in the diagnosis, treatment, and long-term monitoring of diseases, in addition to playing an essential role in the observation and evaluation of physiological activities. The development of modern medical activities cannot be separated from the precise detection, reliable acquisition, and intelligent analysis of human body information. Therefore, sensors have become the core of new-generation health technologies along with the Internet of Things (IoTs) and artificial intelligence (AI). Previous research on the sensing of human information has conferred many superior properties on sensors, of which biocompatibility is one of the most important. Recently, biocompatible biosensors have developed rapidly to provide the possibility for the long-term and in-situ monitoring of physiological information. In this review, we summarize the ideal features and engineering realization strategies of three different types of biocompatible biosensors, including wearable, ingestible, and implantable sensors from the level of sensor designing and application. Additionally, the detection targets of the biosensors are further divided into vital life parameters (e.g., body temperature, heart rate, blood pressure, and respiratory rate), biochemical indicators, as well as physical and physiological parameters based on the clinical needs. In this review, starting from the emerging concept of next-generation diagnostics and healthcare technologies, we discuss how biocompatible sensors revolutionize the state-of-art healthcare system unprecedentedly, as well as the challenges and opportunities faced in the future development of biocompatible health sensors.

Gastroparesis syndromes: emerging drug targets and potential therapeutic opportunities

INTRODUCTION

Gastroparesis (Gp) and related disorders such as chronic unexplained nausea and vomiting and functional dyspepsia, known as gastropareis syndromes (GpS), have large unmet needs. Mainstays of GpS treatments are diet and drugs.

AREAS COVERED

The purpose of this review is to explore potential new medications and other therapies for gastroparesis. Before discussing possible new drugs, the currently used drugs are discussed. These include dopamine receptor antagonists, 5-hydroxytryptamine receptor agonists and antagonists, neurokinin-1 receptor antagonists and other anti-emetics. The article also considers future drugs that may be used for Gp, based on currently known pathophysiology.

EXPERT OPINION

Gaps in knowledge about the pathophysiology of gastroparesis and related syndromes are critical to developing therapeutic agents that will be successful. Recent major developments in the gastroparesis arena are related to microscopic anatomy, cellular function, and pathophysiology. The major challenges moving forward will be to develop the genetic and biochemical correlates of these major developments in gastroparesis research.

Actively Triggerable Metals via Liquid Metal Embrittlement for Biomedical Applications

Actively triggerable materials, which break down upon introduction of an exogenous stimulus, enable precise control over the lifetime of biomedical technologies, as well as adaptation to unforeseen circumstances, such as changes to an established treatment plan. Yet, most actively triggerable materials are low-strength polymers and hydrogels with limited long-term durability. By contrast, metals possess advantageous functional properties, including high mechanical strength and conductivity, that are desirable across several applications within biomedicine. To realize actively triggerable metals, a mechanism called liquid metal embrittlement is leveraged, in which certain liquid metals penetrate the grain boundaries of certain solid metals and cause them to dramatically weaken or disintegrate. In this work, it is demonstrated that eutectic gallium indium (EGaIn), a biocompatible alloy of gallium, can be formulated to reproducibly trigger the breakdown of aluminum within different physiologically relevant environments. The breakdown behavior of aluminum after triggering can further be readily controlled by manipulating its grain structure. Finally, three possible use cases of biomedical devices constructed from actively triggerable metals are demonstrated.

One-Step Soaking Strategy toward Anti-Swelling Hydrogels with a Stiff "Armor"

Double-network (DN) hydrogels consisting of noncovalent interacting networks are highly desired due to their well-controlled compositions and environmental friendliness, but the low water resistance always impairs their mechanical strength. Here, an anti-swelling hydrogel possessing the core/shell architecture through rational regulation of multiple weak noncovalent interactions is prepared. A composite hydrogel consists of chitosan (CS) and poly(N-acryloyl 2-glycine) (PACG), readily forming the shell-structured DN hydrogel after soaking in a FeCl₃ solution because of in situ formation of chain entanglements, hydrogen bonds, and ionic coordination. The produced DN hydrogels exhibit excellent anti-swelling behaviors and mechanical durability for over half a year, even in some strict situations. Taking the merits of noncovalent bonds in adjustability and reversibility, the swelling property of these hydrogels can be easily customized through control of the ion species and concentrations. A dynamically reversible transition from super-swelling to anti-swelling is realized by breaking up and rebuilding the metal-coordination complexes. This facile but efficient strategy of turning the noncovalent interactions and consequently the mechanics and anti-swelling properties is imperative to achieve the rational design of high-performance hydrogels with specific usage requirements and expand their applicability to a higher stage.

Soft robot-enabled controlled release of oral drug formulations

The creation of highly effective oral drug delivery systems (ODDSs) has long been the main objective of pharmaceutical research. Multidisciplinary efforts involving materials, electronics, control, and pharmaceutical sciences encourage the development of robot-enabled ODDSs. Compared with conventional rigid robots, soft robots potentially offer better mechanical compliance and biocompatibility with biological tissues, more versatile shape control and maneuverability, and multifunctionality. In this paper, we first describe and highlight the importance of manipulating drug release kinetics, i.e. pharmaceutical kinetics. We then introduce an overview of state-of-the-art soft robot-based ODDSs comprising resident, shape-programming, locomotive, and integrated soft robots. Finally, the challenges and outlook regarding future soft robot-based ODDS development are discussed.

Fluorescent double network ionogels with fast self-healability and high resilience for reliable human motion detection

Fascinating properties are displayed by high-performance ionogel-based flexible strain sensors, thereby gaining increasing attention in various applications ranging from human motion monitoring to soft robotics. However, the integration of excellent properties such as optical and mechanical properties and satisfactory sensing performance for one ionogel sensor is still a challenge. In particular, fatigue-resistant and self-healing properties are essential to continuous sensing. Herein, we design a flexible ion-conductive sensor based on a multifunctional ionogel with a double network using polyacrylamide, amino-modified agarose, 1,3,5-benzenetricarboxaldehyde and 1-ethyl-3-methylimidazolium chloride. The ionogel exhibits comprehensive properties including high transparency (>95%), nonflammability, strong adhesion and good temperature tolerance (about -96 to 260 °C), especially adaptive for extreme conditions. The dynamic imine bonds and abundant hydrogen bonds endow the ionogel with excellent self-healing capability, to realize rapid self-repair within minutes, as well as good mechanical properties and ductility to dissipate input energy and realize high resilience. Notably, unexpected fluorescence has been observed for the ionogel because of the gelation-induced emission phenomenon. Flexible strain sensors prepared directly from ionogels can sensitively monitor and differentiate various human motions, exhibiting a fast response time (38 ms), high sensitivity (gauge factor = 3.13 at 800% strain), good durability (>1000 cycles) and excellent stability over a wide temperature range (-30 to 80 °C). Therefore, the prepared ionogel as a high-performance flexible strain sensor in this study shows tremendous potential in wearable devices and soft ionotronics.

Strong, Chemically Stable, and Enzymatically On-Demand Detachable Hydrogel Adhesion Using Protein Crosslink

Achieving strong adhesion between hydrogels and diverse materials is greatly significant for emerging technologies yet remains challenging. Existing methods using non-covalent bonds have limited pH and ion stability, while those using covalent bonds typically lack on-demand detachment capability, limiting their applications. In this study, a general strategy of covalent bond-based and detachable adhesion by incorporating amine-rich proteins in various hydrogels and inducing the interfacial crosslinking of the hydrogels using a protein-crosslinking agent is demonstrated. The protein crosslink offers topological adhesion and can reach a strong adhesion energy of ≈750 J m^-2 . The chemistry of the adhesion is characterized and that the inclusion of proteins inside the hydrogels does not alter the hydrogels' properties is shown. The adhesion remains intact after treating the adhered hydrogels with various pH solutions and ions, even at an elevated temperature. The detachment is triggered by treating proteinase solution at the bonding front, causing the digestion of proteins, thus breaking up the interfacial crosslink network. In addition, that this approach can be used to adhere hydrogels to diverse dry surfaces, including glass, elastomers and plastics, is shown. The stable chemistry of protein crosslinks opens the door for various applications in a wide range of chemical environments.

Silk-Based Biomaterials for Designing Bioinspired Microarchitecture for Various Biomedical Applications

Biomaterial research has led to revolutionary healthcare advances. Natural biological macromolecules can impact high-performance, multipurpose materials. This has prompted the quest for affordable healthcare solutions, with a focus on renewable biomaterials with a wide variety of applications and ecologically friendly techniques. Imitating their chemical compositions and hierarchical structures, bioinspired based materials have elevated rapidly over the past few decades. Bio-inspired strategies entail extracting fundamental components and reassembling them into programmable biomaterials. This method may improve its processability and modifiability, allowing it to meet the biological application criteria. Silk is a desirable biosourced raw material due to its high mechanical properties, flexibility, bioactive component sequestration, controlled biodegradability, remarkable biocompatibility, and inexpensiveness. Silk regulates temporo-spatial, biochemical and biophysical reactions. Extracellular biophysical factors regulate cellular destiny dynamically. This review examines the bioinspired structural and functional properties of silk material based scaffolds. We explored silk types, chemical composition, architecture, mechanical properties, topography, and 3D geometry to unlock the body's innate regenerative potential, keeping in mind the novel biophysical properties of silk in film, fiber, and other potential forms, coupled with facile chemical changes, and its ability to match functional requirements for specific tissues.

The Role of Hydrogel in Cardiac Repair and Regeneration for Myocardial Infarction: Recent Advances and Future Perspectives

A myocardial infarction (MI) is the leading cause of morbidity and mortality, seriously threatens human health, and becomes a major health burden of our society. It is urgent to pursue effective therapeutic strategies for the regeneration and restore myocardial function after MI. This review discusses the role of hydrogel in cardiac repair and regeneration for MI. Hydrogel-based cardiac patches and injectable hydrogels are the most commonly used applications in cardiac regeneration medicine. With injectable hydrogels, bioactive compounds and cells can be delivered in situ, promoting in situ repair and regeneration, while hydrogel-based cardiac patches reduce myocardial wall stress, which passively inhibits ventricular expansion. Hydrogel-based cardiac patches work as mechanically supportive biomaterials. In cardiac regeneration medicine, clinical trials and commercial products are limited. Biomaterials, biochemistry, and biological actives, such as intelligent hydrogels and hydrogel-based exosome patches, which may serve as an effective treatment for MI in the future, are still under development. Further investigation of clinical feasibility is warranted. We can anticipate hydrogels having immense translational potential for cardiac regeneration in the near future.

Endoscopy Deliverable and Mushroom-Cap-Inspired Hyperboloid-Shaped Drug-Laden Bioadhesive Hydrogel for Stomach Perforation Repair

Gastrointestinal tract perforation is a full-thickness injury that causes bleeding and fatal infection of the peritoneum. This condition worsens in an acidic gastric environment which interferes with the normal coagulation cascade. Current endoscopic clips to repair gastric perforations are ineffective, and metal or plastic occluders need secondary surgery to remove them. Herein, we report a self-expandable, endoscopy deliverable, adhesive hydrogel to block gastric perforation. We found the nanosilica coating significantly enhanced the adhesive strength even under a simulated strong acidic stomach environment. The developed device was disulfide cross-linked for the reducible degraded gel. By loading with vonoprazan fumarate (VF) and acidic fibroblast growth factor (AFGF), the hyperboloid-shaped device can have a sustained drug release to regulate intragastric pH and promote wound healing. The gel device can be compressed and then expanded like a mushroom when applied in an acute gastric perforation model in both rabbits and minipigs. By utilizing a stomach capsule robot for remotely monitoring the pH and by immunohistochemical analysis, we demonstrated that the compressible hyperboloid-shaped gel could stably block the perforation and promoted wound healing during the 28 days of observation. The real-time pH meter demonstrated that the gel could control intragastric pH above 4 for nearly 60 h to prevent bleeding.

Globefish-Inspired Balloon Catheter with Intelligent Microneedle Coating for Endovascular Drug Delivery

Balloon catheters exhibit important values in treating cardiovascular diseases, while their functions are still under improvements. Here, inspired by the thorn-hiding and deflating-inflating characteristics of globefish, intelligent balloon catheters decorated with invisible microneedles are presented for endovascular drug delivery to inhibit postintervention restenosis (PIRS). These microneedle balloon catheters (MNBCs) fabricated by dipping and rolling-assisted template replication contain three coating layers of sandwiched drug-carrying microneedles and black phosphorus (BP)-carrying gelatin. During the emplacement, the microneedles of MNBCs are hidden under the outermost gelatin protective layer, allowing smooth movements inside the blood vessel. After reaching the destination, the embedded BP converts near infrared (NIR) into heat, increases local temperature, and melts the gelatin layer, enabling the exposure and vascular penetration of the microneedles. Besides, as the innermost gelatin also melts, the microneedles can detach from the balloon catheter and be left inside the blood vessel for continuous drug release. Based on advantages of responsiveness, penetration capacity, and biosafety, it is demonstrated that the MNBCs behave satisfactorily in delivering rapamycin to inhibit abdominal aorta restenosis in rats. All these features indicate that these MNBCs are promising medical devices for clinical applications.

Design and application of stimuli-responsive DNA hydrogels: A review

Deoxyribonucleic acid (DNA) hydrogels combine the properties of DNAs and hydrogels, and adding functionalized DNAs is key to the wide application of DNA hydrogels. In stimuli-responsive DNA hydrogels, the DNA transcends its application in genetics and bridges the gap between different fields. Specifically, the DNA acts as both an information carrier and a bridge in constructing DNA hydrogels. The programmability and biocompatibility of DNA hydrogel make it change macroscopically in response to a variety of stimuli. In order to meet the needs of different scenarios, DNA hydrogels were also designed into microcapsules, beads, membranes, microneedle patches, and other forms. In this study, the stimuli were classified into single biological and non-biological stimuli and composite stimuli. Stimuli-responsive DNA hydrogels from the past five years were summarized, including but not limited to their design and application, in particular logic gate pathways and signal amplification mechanisms. Stimuli-responsive DNA hydrogels have been applied to fields such as sensing, nanorobots, information carriers, controlled drug release, and disease treatment. Different potential applications and the developmental pro-spects of stimuli-responsive DNA hydrogels were discussed.

Percutaneous Electroosmosis of Berberine-Loaded Ca2+ Crosslinked Gelatin/Alginate Mixed Hydrogel

Flexible conductive hydrogel has been driven by scientific breakthroughs and offers a wide variety of applications, including sensors, electronic skins, biomedicine, energy storage, etc. Based on the mixed-ion crosslinking method, gelatin and sodium alginate (Gel-Alg) composite hydrogels were successfully prepared using Ca²⁺ crosslinking. The migration behavior of berberine hydrochloride (BBH) in the matrix network structure of Gel-Alg hydrogel with a certain pore size under an electric field was studied, and the transdermal effect of berberine hydrochloride under an electric field was also studied. The experimental results show that Gel-Alg has good flexibility and conductivity, and electrical stimulation can enhance the transdermal effect of drugs. Gel-Alg composite hydrogel may be a new material with potential application value in future biomedical directions.

Physicochemical Properties of Cellulose-Based Hydrogel for Biomedical Applications

Hydrogels are three-dimensional network structures of hydrophilic polymers, which have the capacity to take up an enormous amount of fluid/water. Carboxymethyl cellulose (CMC) is a commercially available cellulose derivative that can be used for biomedical applications due to its biocompatibility. It has been used as a major component to fabricate hydrogels because of its superabsorbent nature. In this study, we developed carboxylic acid crosslinked carboxymethyl cellulose hydrogels for biomedical applications. The physicochemical, morphological, and thermal properties were analyzed to confirm the crosslinking of carboxymethyl cellulose. Fourier-transform infrared spectra confirmed the crosslinking of carboxymethyl cellulose with the presence of peaks due to an esterification reaction. The distinct peak at 1718 cm-1 in hydrogel samples is due to the carbonyl group vibrations of the ester bond from the crosslinking reaction. The total carboxyl content of the sample was measured with crosslinker immersion time. The swelling of crosslinked hydrogels showed an excellent swelling capacity for CG02 that is much higher than CG01 in water and PBS. Morphological analysis of the hydrogel showed it has a rough surface. The thermal degradation of hydrogel showed stability with respect to temperature. However, the mechanical analysis showed that CG01 has a higher compressive strength than CG01. The optimum swelling ratio and higher compressive strength of CG01 hydrogels could give them the ability to be used in load-bearing tissue regeneration. These results inferred that the carboxylic acid crosslinked CMC hydrogels could be a suitable matrix for biomedical or tissue-engineering applications with improved stability.