Multifunctional Ionic Hydrogel-Based Transdermal Delivery of 5-Fluorouracil for the Breast Cancer Treatment

Transdermal drug delivery systems (TDDS) are a promising and innovative approach for breast cancer treatment, offering advantages such as noninvasiveness, potential for localized and prolonged drug delivery while minimizing systemic side effects through avoiding first-pass metabolism. Utilizing the distinctive characteristics of hydrogels, such as their biocompatibility, versatility, and higher drug loading capabilities, in the present work, we prepared ionic hydrogels through synergistic interaction between ionic liquids (ILs), choline alanine ([Cho][Ala]), and choline proline ([Cho][Pro]) with oleic acid (OA). ILs used in the study are biocompatible and enhance the solubility of 5-fluorouracil (5-FU), whereas OA is a known chemical penetration enhancer. The concentration-dependent (OA) change in morphological aggregates, that is, from cylindrical micelles to worm-like micelles to hydrogels was formed with both ILs and was characterized by SANS measurement, whereas the interactions involved were confirmed by FTIR spectroscopy. The hydrogels have excellent mechanical properties, which studied by rheology and their morphology through FE-SEM analysis. The in vitro skin permeation study revealed that both hydrogels penetrated 255 times ([Cho][Ala]) and 250 times ([Cho][Pro]) more as compared to PBS after 48 h. Those ionic hydrogels exhibited the capability to change the lipid and keratin arrangements within the skin layer, thereby enhancing the transdermal permeation of the 5-FU. Both ionic hydrogels exhibit excellent biocompatibility with normal cell lines (L-132 cells) as well as cancerous cell lines (MCF-7 cells), demonstrating over 92% cell viability after 48 h in both cell lines. In vitro, the cytotoxicity of the 5-FU-loaded hydrogels was evaluated on MCF-7 and HeLa cell lines. These results indicate that the investigated biocompatible and nontoxic ionic hydrogels enable the transdermal delivery of hydrophilic drugs, making them a viable option for effectively treating breast cancer.

Conductive and Eco-friendly Biomaterials-based Hydrogels for Noninvasive Epidermal Sensors: A Review

As noninvasive wearable electronic devices, epidermal sensors enable continuous, real-time, and remote monitoring of various human physiological parameters. Conductive biomaterials-based hydrogels as sensor matrix materials have good biocompatibility, biodegradability, and efficient stimulus response capabilities and are widely applied in motion monitoring, healthcare, and human-machine interaction. However, biomass hydrogel-based epidermal sensing devices still need excellent mechanical properties, prolonged stability, multifunctionality, and extensive practicality. Therefore, this paper reviews the common biomass hydrogel materials for epidermal sensing (proteins, polysaccharides, polyphenols, etc.) and the various types of noninvasive sensing devices (strain/pressure sensors, temperature sensors, glucose sensors, electrocardiograms, etc.). Moreover, this review focuses on the strategies of scholars to enhance sensor properties, such as strength, conductivity, stability, adhesion, and self-healing ability. This work will guide the preparation and optimization of high-performance biomaterials-based hydrogel epidermal sensors.

Synaptic transistor with multiple biological functions based on metal-organic frameworks combined with the LIF model of a spiking neural network to recognize temporal information

Spiking neural networks (SNNs) have immense potential due to their utilization of synaptic plasticity and ability to take advantage of temporal correlation and low power consumption. The leaky integration and firing (LIF) model and spike-timing-dependent plasticity (STDP) are the fundamental components of SNNs. Here, a neural device is first demonstrated by zeolitic imidazolate frameworks (ZIFs) as an essential part of the synaptic transistor to simulate SNNs. Significantly, three kinds of typical functions between neurons, the memory function achieved through the hippocampus, synaptic weight regulation and membrane potential triggered by ion migration, are effectively described through short-term memory/long-term memory (STM/LTM), long-term depression/long-term potentiation (LTD/LTP) and LIF, respectively. Furthermore, the update rule of iteration weight in the backpropagation based on the time interval between presynaptic and postsynaptic pulses is extracted and fitted from the STDP. In addition, the postsynaptic currents of the channel directly connect to the very large scale integration (VLSI) implementation of the LIF mode that can convert high-frequency information into spare pulses based on the threshold of membrane potential. The leaky integrator block, firing/detector block and frequency adaptation block instantaneously release the accumulated voltage to form pulses. Finally, we recode the steady-state visual evoked potentials (SSVEPs) belonging to the electroencephalogram (EEG) with filter characteristics of LIF. SNNs deeply fused by synaptic transistors are designed to recognize the 40 different frequencies of EEG and improve accuracy to 95.1%. This work represents an advanced contribution to brain-like chips and promotes the systematization and diversification of artificial intelligence.

Hydrogel transformed from sandcastle-worm-inspired powder for adhering wet adipose surfaces

Normally, hydrogel adhesives do not perform well on adipose matters that are covered with bodily fluids. Besides, the maintenance of high extensibility and self-healing ability in fully swollen state still remains challenging. Based on these concerns, we reported a sandcastle-worm-inspired powder, which was made of tannic acid-functionalized cellulose nanofiber (TA-CNF), polyacrylic acid (PAA) and polyethyleneimine (PEI). The obtained powder can rapidly absorb diverse bodily fluids and transform into a hydrogel, displaying fast (＜3 s), self-strengthening and repeatable wet adhesion to adipose tissues. Due to the dense physically cross-linked network, the formed hydrogel still showed excellent extensibility (∼14 times) and self-healing ability after being immersed in water. Moreover, excellent hemostasis, antibacterial ability and biocompatibility make it suitable for numerous biomedical applications. With combined advantages of powders and hydrogels, such as good adaptability to irregular sites, efficient drug loading capacity and tissue affinity, the sandcastle-worm-inspired powder offers significant promise as tissue adhesive and repair materials. This work may open new avenues for designing high-performance bioadhesives with efficient and robust wet adhesiveness to adipose tissues.

A mechanically tough and ultra-swellable microneedle for acute gout arthritis

Acute gout arthritis (AGA) remains the fundamental research focus in the entire medical field. Hydrogel microneedles (HMNs) loaded with therapeutic molecules such as colchicine (Col) have been developed as a new tool for the management of AGA in a minimally invasive manner. However, the incompatible mechanical and swelling properties of HMNs limited the diffusion of the drug from the HMN system, which remains a challenge for practical use. Here, a mechanically tough (11.53 N per needle) and super-swelling (2708%) hydrogel microneedle (HMNs) composed of a uniform network structure was developed using a UV-responsive crosslinker through in situ photopolymerization for percutaneous delivery of Col. Such HMNs and Col loaded HMNs (Col-HMNs) present excellent biocompatibility. Moreover, Col-HMNs present considerable anti-inflammatory effects in vivo through down-regulated inflammatory responses such as related cytokines IL-1β, IL-6, and TNF-α. These results demonstrated that the mechanically tough and super-swelling HMNs could be a promising tool for effective Col delivery to relieve AGA.

Ionic liquid multistate resistive switching characteristics in two terminal soft and flexible discrete channels for neuromorphic computing

By exploiting ion transport phenomena in a soft and flexible discrete channel, liquid material conductance can be controlled by using an electrical input signal, which results in analog neuromorphic behavior. This paper proposes an ionic liquid (IL) multistate resistive switching device capable of mimicking synapse analog behavior by using IL BMIM FeCL₄ and H₂O into the two ends of a discrete polydimethylsiloxane (PDMS) channel. The spike rate-dependent plasticity (SRDP) and spike-timing-dependent plasticity (STDP) behavior are highly stable by modulating the input signal. Furthermore, the discrete channel device presents highly durable performance under mechanical bending and stretching. Using the obtained parameters from the proposed ionic liquid-based synaptic device, convolutional neural network simulation runs to an image recognition task, reaching an accuracy of 84%. The bending test of a device opens a new gateway for the future of soft and flexible brain-inspired neuromorphic computing systems for various shaped artificial intelligence applications.

Mechanically tuneable physical nanocomposite hydrogels from polyelectrolyte complex templated silica nanoparticles for anionic therapeutic delivery

Hydrogels have shown great promise for drug delivery and tissue engineering but can be limited in practical applications by poor mechanical performance. The incorporation of polymer grafted silica nanoparticles as chemical or physical crosslinkers in in situ polymerised nanocomposite hydrogels has been widely researched to enhance their mechanical properties. Despite the enhanced mechanical stiffness, tensile strength, and self-healing properties, there remains a need for the development of simpler and modular approaches to obtain nanocomposite hydrogels. Herein, we report a facile protocol for the polyelectrolyte complex (PEC) templated synthesis of organic-inorganic hybrid poly(ethylenimine) functionalised silica nanoparticles (PEI-SiNPs) and their use as multifunctional electrostatic crosslinkers with hyaluronic acid (HA) to form nanocomposite hydrogels. Upon mixing, electrostatic interactions between cationic PEI-SiNPs and anionic HA resulted in the formation of a coacervate nanocomposite hydrogel with enhanced mechanical stiffness that can be tuned by varying the ratios of PEI-SiNPs and HA present. The reversible electrostatic interactions within the hydrogel networks also enabled self-healing and thixotropic properties. The excess positive charge present within the PEI-SiNPs facilitated high loading and retarded the release of the anionic anti-cancer drug methotrexate from the nanocomposite hydrogel. Furthermore, the electrostatic complexation of PEI-SiNP and HA was found to mitigate haemotoxicity concerns associated with the use of high molecular weight PEI. The method presented herein offers a simpler and more versatile strategy for the fabrication of coacervate nanocomposite hydrogels with tuneable mechanical stiffness and self-healing properties for drug delivery applications.

Graphene oxide-based composite organohydrogels with high strength and low temperature resistance for strain sensors

In recent years, a rapid development of polymeric hydrogel-based sensors has been witnessed. However, conventional hydrogels often exhibit poor mechanical properties. Additionally, the use of these sensors at temperatures <0 °C is limited due to the freezing of the water molecules in the hydrogel matrix. In this study, graphene oxide/poly(acrylamide-co-N-(3-amino propyl)methacrylamide) [poly(AAm-co-APMA)/GO] hydrogels have been synthesized by UV photo-initiation polymerization. Subsequently, the poly(AAm-co-APMA)/GO-Gly (PAAG-Gly) organohydrogels were obtained by glycerol replacement. GO and glycerol had multiple interactions with the polymer chains, which endowed the physically crosslinked organohydrogel with a high fracture stress of up to 782.9 ± 38.6 kPa. Also, the glycerol molecules formed hydrogen bonds with the water molecules, thus inhibiting the formation of ice crystals. After storage at -20 °C for 24 h, the PAAG-Gly organohydrogels retained their superior mechanical properties, adhesion strength, and electrical conductivity. Once the cut surfaces of the organohydrogel were contacted, the conductive path was rapidly self-healed. Moreover, the PAAG-Gly organohydrogels exhibited excellent cytocompatibility. At 100% strain, the gauge factor of the organohydrogel-based sensor reached 4.22. The organohydrogel-based sensor revealed the capability to monitor human motions, such as finger, wrist and knee movements.

Polyelectrolyte Gels: Fundamentals, Fabrication and Applications

Polyelectrolyte gels are an important class of polymer gels and a versatile platform with charged polymer networks with ionisable groups. They have drawn significant recent attention as a class of smart material and have demonstrated potential for a variety of applications. This review begins with the fundamentals of polyelectrolyte gels, which encompass various classifications (i.e., origin, charge, shape) and crucial aspects (ionic conductivity and stimuli responsiveness). It further centralises recent developments of polyelectrolyte gels, emphasising their synthesis, structure-property relationships and responsive properties. Sequentially, this review demonstrates how polyelectrolyte gels' flourishing properties create attractiveness to a range of applications including tissue engineering, drug delivery, actuators and bioelectronics. Finally, the review outlines the indisputable appeal, further improvements and emerging trends in polyelectrolyte gels.

Fluorescent Nanogel Sensors for X-ray Dosimetry

X-ray dosimeters are of significance for detecting the levels of ionizing radiation exposure in cells and phantoms; thus, they can further optimize X-ray radiotherapy in the clinic. In this paper, we designed a polyacrylamide-based nanogel sensor that is capable of measuring X-ray doses. The dosimeters were prepared by anchoring an X-ray-responsive probe (aminophenyl fluorescein, APF) to poly(acrylamide-co-N-(3-aminopropyl) methyl acrylamide) nanogels. The premise behind the dose measurement is the transition of APF to fluorescence in the presence of hydroxyl radicals that are caused by the radiolysis of water molecules under X-rays. Therefore, the dose of X-rays can be readily detected by measuring the fluorescence intensity of the resultant nanogel immediately after irradiation using fluorescence spectroscopy principles. Using an RS2000 X-ray biological irradiator, our dosimeters showed good linearity responsivity at X-ray doses ranging from 0 to 15 Gy, with a limit of detection (LOD) of 0.5 Gy. Additionally, the signals showed temperature stability (25-65 °C), durability (5 weeks), and dose-rate (1.177 and 6 Gy/min) and energy independence (160 kVp and 6 MV). As a proof-of-concept, we used our sensors to fluorescently detect X-ray doses in A549 tumor cells and 3D-printed eye phantoms. The results showed that our dosimeters were able to accurately predict doses similar to those used by treatment plan systems.

Bioinspired tissue-compliant hydrogels with multifunctions for synergistic surgery-photothermal therapy

Operation therapy is a common treatment for many cancers, but malignant tumors likely recur and metastasize after surgery, resulting in treatment failure. In this study, we aimed at synthesizing a multifunctional hydrogel patch that features multifunctions for synergistic surgery-photothermal therapy. Our polydopamine nanoparticle (PDA NP)-crosslinked poly(acrylamide-co-N-(3-aminopropyl)methacrylamide) hydrogels undergo several dynamic interactions (e.g., hydrogen bonds, π-π interactions, and imine bonds), which confer high stretchability (∼3430%) and adhesive strength to porcine skin (∼75 kPa) that mimics soft wound tissues. Furthermore, PDA NP incorporation into the hydrogel matrix endows it with photothermal responsivity under 808 nm irradiation. As a proof of concept, our hydrogel system was used to ablate residual tumors in 4T1 tumor-bearing mice models after surgery via photothermal therapy. We find that synergistic operation-photothermal therapy effectively eradicates solid tumors and prevents cancer recurrence in mice. We envision that our work provides an effective synergistic strategy for cancer treatment and offers great potential for clinical applications.

Development and Characterization of a Novel Hydrogel for the Decontaminating of Radionuclide-Contaminated Skin Wounds

Designing skin decontaminating materials with outstanding therapeutic effects, adhesiveness, and suitable mechanical property has great practical significance in radionuclide-contaminated skin wound healing. Here, a physically crosslinked hydrogel is constructed via hydrogen bonding of poly acrylamide, sodium alginate (SA), and the complexing agent diethylene triamine pentaacetic acid (DTPA). The physical and chemical properties of the poly(AAm-SA-DTPA) hydrogel (PASD) are detected according to established methods. The decontaminating property and skin wound healing of the PASD are investigated to confirm multi-functions of wound dressing. The physical and chemical properties results show that the synthesis of the PASD hydrogel is effective and that DTPA is present in the hydrogel. The hydrogel also shows great mechanical and swelling properties. In vitro tests find that PASD shows significant scavenging abilities for strontium and cerium. In vivo experiments show that the PASD hydrogel can remove radioactive strontium from the skin wounds of mice, and can effectively prevent the absorption of radioactive strontium through the skin wound. Furthermore, the PASD hydrogel can effectively promote the formation of granulation tissue in a radioactive contaminated wound. Taken together, the PASD hydrogels, which has good mechanical properties and radionuclides decontamination, is expected to be used as a dressing for radionuclide-contaminated skin wound healing.

Double-Hydrophobic-Coating through Quenching for Hydrogels with Strong Resistance to Both Drying and Swelling

In recent years, various hydrogels with a wide range of functionalities have been developed. However, owing to the two major drawbacks of hydrogels-air-drying and water-swelling-hydrogels developed thus far have yet to achieve most of their potential applications. Herein, a bioinspired, facile, and versatile method for fabricating hydrogels with high stability in both air and water is reported. This method includes the creation of a bioinspired homogeneous fusion layer of a hydrophobic polymer and oil in the outermost surface layer of the hydrogel via a double-hydrophobic-coating produced through quenching. As a proof-of-concept, this method is applied to a polyacrylamide hydrogel without compromising its mechanical properties. The coated hydrogel exhibits strong resistance to both drying in air and swelling in multiple aqueous environments. Furthermore, the versatility of this method is demonstrated using different types of hydrogels and oils. Because this method is easy to apply and is not dependent on hydrogel surface chemistry, it can significantly broaden the scope of next-generation hydrogels for real-world applications in both wet and dry environments.

Cellular Nanofiber Structure with Secretory Activity-Promoting Characteristics for Multicellular Spheroid Formation and Hair Follicle Regeneration

Multicellular spheroids can mimic the in vivo microenvironment and maintain the unique functions of tissues, which has attracted great attention in tissue engineering. However, the traditional culture microenvironment with structural deficiencies complicates the culture and collection process and tends to lose the function of multicellular spheroids with the increase of cell passage. In order to construct efficient and functional multicellular spheroids, in this study, a chitosan/polyvinyl alcohol nanofiber sponge which has an open-cell cellular structure is obtained. The hair follicle (HF) regeneration model was employed to evaluate HF-inducing ability of dermal papilla (DP) multicellular spheroids which formed on the cellular structure nanofiber sponge. Through structural fine-tuning, the nanofiber sponge has appropriate elasticity for the creation of a three-dimensional dynamic microenvironment to regulate cellular behavior. The cellular structure nanofiber sponge tilts the balance of cell-substratum and cell-cell interactions to a state which is more conducive to the formation of controllable multicellular spheroids in a short time. More importantly, it improves the secretory activity of high-passaged dermal papilla cells and restores their intrinsic properties. Experiments using BALB/c nude mice show that cultured DP multicellular spheroids could effectively enhance HF-inducing ability. This novel system provides a simple and efficient strategy for multicellular spheroid formation and HF regeneration.

Dynamic covalent bonds in self-healing, shape memory, and controllable stiffness hydrogels

A review of hydrogels containing dynamic bonds that are shown to provide benefits for applications including self-healing and stimuli-induced stiffness changes.

High-Strength, Self-Adhesive, and Strain-Sensitive Chitosan/Poly(acrylic acid) Double-Network Nanocomposite Hydrogels Fabricated by Salt-Soaking Strategy for Flexible Sensors

As a promising functional material, hydrogels have attracted extensive attention, especially in flexible wearable sensor fields, but it remains a great challenge to facilely integrate excellent mechanical properties, self-adhesion, and strain sensitivity into a single hydrogel. In this work, we present high in strength, stretchable, conformable, and self-adhesive chitosan/poly(acrylic acid) double-network nanocomposite hydrogels for application in epidermal strain sensor via in situ polymerization of acrylic acid in chitosan acid aqueous solution with tannic acid-coated cellulose nanocrystal (TA@CNC) acting as nanofillers to reinforce tensile properties, followed by a soaking process in a saturated NaCl solution to cross-link chitosan chains. With addition of a small amount of TA@CNC, the double-network nanocomposite hydrogels became highly adhesive and mechanically compliant, which were critical factors for the development of conformable and resilient wearable epidermal sensors. The salt-soaking process was applied to cross-link chitosan chains by shielded electrostatic repulsions between positively charged amino groups, drastically enhancing the mechanical properties of the hydrogels. The obtained double-network nanocomposite hydrogels exhibited excellent tunable mechanical properties that could be conveniently tailored with fracture stress and fracture strain ranging from 0.39 to 1.2 MPa and 370 to 800%, respectively. Besides, the hydrogels could be tightly attached onto diverse substrates, including wood, glass, plastic, polytetrafluoroethylene, glass, metal, and skin, demonstrating high adhesion strength and compliant adhesion behavior. In addition, benefiting from the abundant free ions from strong electrolytes, the flexible hydrogel sensors demonstrated stable conductivity and strain sensitivity, which could monitor both large human motions and subtle motions. Furthermore, the antibacterial property originating from chitosan made the hydrogels suitable for wearable epidermal sensors. The facile soaking strategy proposed in this work would be promising in fabricating high-strength multifunctional conductive hydrogels used for wearable epidermal devices.

Self-curing super-stretchable polymer/microgel complex coacervate gels without covalent bond formation

Elastic physical gels are highly desirable because they can be conveniently prepared and readily shaped. Unfortunately, many elastic physical gels prepared in water require in situ free-radical polymerization during the gel formation stage. In contrast, complex coacervate gels are physical gels that can be prepared by simply mixing two pre-formed oppositely-charged polyelectrolytes. However, as far as we are aware, highly elastic complex coacervate gels have not yet been reported. Herein, we combine polyanionic microgel particles with a well-known commercially-available cationic polyelectrolyte to prepare polymer/microgel complex coacervate (PMCC) physical gels. This new family of gels requires annealing at only 37 °C and behaves like a covalent gel but does not form covalent bonds. Thermal reconfiguration of the dynamic ionic bonds transforms the shapeable pre-gel into a highly elastic gel that is super-stretchable, adhesive, self-healing, highly swellable and can be further toughened using Ca2+ as an ionic crosslinker. Our PMCC gels have excellent potential for applications as engineering gels and structural biomaterials, as well as for wound healing and water purification.

A dynamic-coupling-reaction-based autonomous self-healing hydrogel with ultra-high stretching and adhesion properties

We synthesized a dynamic coupling-reaction based hydrogel that showed excellent mechanical and adhesion properties, super-high self-healing properties and good biocompatibility.

A muscle mimetic polyelectrolyte–nanoclay organic–inorganic hybrid hydrogel: its self-healing, shape-memory and actuation properties

In this investigation, we report a non-covalent (ionic interlocking and hydrogen bonding) strategy of self-healing in a covalently crosslinked organic–inorganic hybrid nanocomposite hydrogel, with specific emphasis on tuning its properties fitting into a muscle mimetic material.

Flexible and wearable strain sensors based on tough and self-adhesive ion conducting hydrogels

Tough and self-adhesive zwitterionic hydrogels with ionic conductivity have been prepared, showing high and linear strain sensitivity for detecting human motions.

A nanogel sensor for colorimetric fluorescence measurement of ionizing radiation doses

A polyacrylamide-based nanogel sensor was constructed for spectral and visual colorimetric fluorescence measurement of ionizing radiation doses.