Experimental insight into the evolutionary mechanism of solid-to-hollow hydrogel

Degradable Alginate Hydrogel Intervention Catheters with Gradient Hardness in Length

Interventional catheter, a medical device characterized by a gradient hardness from one end to the other, exhibits enhanced flexibility upon insertion into the human body. This unique configuration accommodates various anatomical structures and surgical requirements. This study reports, for the first time, a degradable hydrogel interventional catheter with gradient hardness. A novel aqueous reaction methodology is developed, enabling the direct transformation of a solid sodium alginate (SA) film strip into a hollow hydrogel interventional catheter. This process involves copper ions-induced asymmetry crosslinking in an aqueous solution, solvent exchange in ethanol, removal of copper ions by ethylenediaminetetraacetic acid, and subsequent bimetallic crosslinking in CaCl2 and FeCl3 aqueous solutions. This method results in gradient-hardness hydrogel interventional catheters without surface defects such as protrusions and pits. The hydrogel interventional catheter demonstrates gradient robustness with mechanical strength reaching 5.5 MPa for the soft head and 28 MPa for the hard tail. By incorporating a gradual stiffness variation, the hydrogel catheter with superior lubricity and flexibility more effectively adapts to the anatomical structures of the human body, potentially minimizing tissue damage and expediting surgical procedures. Consequently, it shows significant potential as a medical interventional catheter.

Regulating Supramolecular Assembly and Disassembly of Chitosan toward Efficiently Antibacterial Lubricous and Biodegradable Hydrogel Urinary Catheters

Urinary catheters serve as critical medical devices in clinical practice. However, the currently used urinary catheters lack efficient antibacterial and lubricating properties, often leading to discomfort with patients and even severe urinary infections. Herein, a new strategy of supramolecular assembly and disassembly of chitosan (Cs) is developed that enables efficient antibacterial lubricous and biodegradable hydrogel urinary catheters. Sodium lauryl sulfonate (SLS) is employed to induce supramolecular assembly on the surface of Cs film strips in an aqueous solution, resulting in the formation of hollow hydrogel catheters of Cs@SLS. Subsequent disassembly in a strong alkaline solution eliminates the SLS component, yielding neat Cs hydrogel catheters. The mechanical strength of these catheters reaches 16 MPa, exceeding that of similar devices made of plastics. The Cs hydrogel catheters are endowed with high antibacterial activity, capable of inhibiting the growth of Staphylococcus aureus (S. aureus), Escherichia coli (E. coli) and Proteus mirabilis(P. mirabilis) on its surface, while these bacteria are found to proliferate rapidly on plastic catheters within 24 h. They also demonstrate excellent lubricity, with a friction coefficient approaching zero, and thus about 13 times lower than that of plastic catheters. In vivo tests further confirm the biodegradability of the catheters, highlighting their strong potential for clinical applications.

Processing Solid Hydrogels into Hollow Structures by Infrared Laser Light for Highly-Efficient Drug Loading and Controlled Release

Hollow hydrogels, characterized by their three-dimensional networks akin to biological tissues, are extensively utilized in artificial blood vessels, drug delivery, and nerve conduits due to their superior biocompatibility and fluid-transportation capacity. Nonetheless, the fabrication of hollow hydrogels presents significant challenges, including intricate steps, costly equipment, and structural instability. Consequently, refining the preparation techniques for hollow hydrogels remains paramount to surmounting the limitations of conventional methods. This research introduces an innovative approach that markedly diverges from traditional techniques, offering notable convenience and efficiency in the creation of hollow hydrogel structures. The central novelty of this method lies in employing laser light to induce an in situ photothermal effect, leading to the formation of hollow configurations. This laser-driven transformation of solid hydrogels into hollow structures addresses numerous shortcomings associated with traditional methods. For instance, conventional chemical approaches often necessitate several days to yield hollow hydrogels, and the resultant structures tend to be fragile and susceptible to damage under external pressure. In contrast, the laser-assisted technique facilitates the formation of hollow structures within 240 s, significantly outpacing traditional methods. To achieve controlled drug release, silk fibroin was integrated into the wall of the hollow hydrogels, enabling modulation of wall permeability and directing the drug release process.

Continuous and Controllable Preparation of Sodium Alginate Hydrogel Tubes Guided by the Soft Cap Inspired by the Apical Growth of the Plant

Hydrogel tubes made of sodium alginate (SA) have potential applications in drug delivery, soft robots, biomimetic blood vessels, tissue stents, and other fields. However, the continuous preparation of hollow SA hydrogel tubes with good stability and size control remains a huge challenge for chemists, material scientists, and medical practitioners. Inspired by the plant apical growth strategy, a new method named soft cap-guided growth was proposed to produce SA hydrogel tubes. Due to the introduction of inert low gravity substances, such as air and heptane, into the extrusion needle in front of calcium chloride solution to form a soft cap, the SA hydrogel tubes with controllable sizes were fabricated rapidly and continuously without using a template through a negative gravitropism mechanism. The SA hydrogel tubes had good tensile strength, high burst pressure, and good cell compatibility. In addition, hydrogel tubes with complex patterns were conveniently created by controlling the motion path of a soft cap, such as a rotating SA bath or magnetic force. Our research provided a simple innovative technique to steer the growth of hydrogel tubes, which made it possible to mass produce hydrogel tubes with controllable sizes and programmable patterns.

Magnetic Actuation of Hollow Swarming Spheres for Dynamic Catalysis

Untethered robots with smart human-machine interactions can execute complex activities such as target cargo delivery or assembly of functional scaffolds. However, it remains challenging for fabricating microscale hollow hydrogel robots that can go with autonomous transformation of their geometric formations to adapt to unstructured environments. We herein report hydrogel-based microscopic hollow swarming spheres (HSSs) with anisotropic/isotropic alignments of Fe₃O₄ particles in the porous wall that can navigate under complex topography conditions by altering their geometric formation, including passing around or jumping over obstacles, assembling into various formation patterns, and swimming in a high-viscosity system. We introduce HSSs into a catalytic reaction model, in which HSSs as a catalyst can shift between water and oil phases to initiate or terminate the decomposition reaction of H₂O₂. This dynamic catalysis is expected to construct free-radical "living" polymerization for controlling the reaction rate and polymer dispersity index in the future.

Temperature-Responsive, Manipulable Cavitary Hydrogel Containers by Macroscopic Spatial Surface-Interior Separation

Synthetic macroscopic materials transforming from bulk solid or semisolid to a closed structure with inner cavities and distinct outer and inner microstructures are rarely reported. Here, we report an in situ method for directing spatial surface-interior separation from bulk dynamic hydrogels to closed three-dimensional (3D) hydrogel containers with inner cavities via constructing a competitively cross-linking gradient within dynamic hydrogels. The initial cross-linking of phenylboronic acid/catechol complexes is disrupted by stronger ferric ions/catechol associations, generating gradually weakened cross-linking from the outside to the inside. Both stronger cross-linking in the outer shells and sequentially weaker cross-linked interior generated during swelling closed the hydrogel container with a tunable dense outer shell, fluffy inner layer, and cavities in the core. Cellulose nanocrystals could be used to significantly improve the spatial distinction of gradient cross-linking within hydrogels, leading to an even denser outer shell with tunable shell thickness. Moreover, cavitary hydrogel containers with diverse shapes can be programmed by designing the initial shapes of dynamic hydrogels and macroscopic assembly of individual dynamic hydrogels based on their self-healing capability after subsequent surface-interior separation. These cavitary hydrogel containers demonstrate thermal-responsive gate systems with unique sustained release at higher temperature and potential reaction containers for oxygen generation on demand. This facile spatial surface-interior separation strategy for fabricating closed cavity systems has great potential for various applications.

Celiac Disease and Non-celiac Wheat Sensitivity: State of Art of Non-dietary Therapies

Gluten related disorders (GRD), which include celiac disease, non-celiac wheat sensitivity and wheat allergy are heterogeneous conditions triggered by ingestion of gluten-containing grains. Together, their prevalence is estimated to be ~5% in the general population, however, in the last years the number of diagnoses has been rapidly increasing. To this day, the gold standard treatment for these disorders is the complete removal of gluten-containing grains from the diet. Although this therapy results effective in the majority of patients, up to 30% of individuals affected by GRD continue to present persistent symptoms. In addition, gluten-free diet has been shown to have poor nutritional quality and to cause a socio-economic burden in patients' quality of life. In order to respond to these issues, the scientific community has been focusing on finding additional and adjuvant non-dietary therapies. In this review, we focus on two main gluten related disorders, celiac disease and non-celiac wheat sensitivity. We delineate the actual knowledge about potential treatments and their relative efficacy in pre-clinical and clinical trials.