Poly(acrylic acid)/polypyrrole interpenetrated network as electro‐responsive hydrogel for biomedical applications

Hierarchical Crack Engineering-Enabled High-Linearity and Ultrasensitive Strain Sensors

Growing imperative for intelligent transformation of electro-ionic actuators in soft robotics has necessitated self-perception for accurately mapping their nonlinear dynamic responses. Despite the promise of integrating crack-based strain sensors for such a purpose, significant challenges remain in controlling crack propagation to prevent the induction of through-cracks, resulting in lower sensitivity, linearity, and poor detection limits. Herein, we propose a hierarchical crack-based synergistic enhancement structure by incorporating conductive poly(pyrrole)-coated polystyrene nanospheres and Ti3C2Tx MXene to induce cross-long sensing cracks via point-to-plane contacts, along with silver nanowires for positively engineering networked microcracks for linearity tuning. The prepared microstrain sensor achieves high linearity (GF = 152.4, R2 = 0.99) regulation within ∼6% strain range, ultralow detection limit of 0.02%, and ultrafast response/recovery time of 31 ms/32 ms under 0.2%. Notably, state-of-the-art sensing performance by detecting minimal strain changes down to one millionth, i.e., ∼1 microstrain, has been demonstrated by voiceprint recognition, while maintaining superior dynamic measurement capability and long-term stability for mechanical vibrations up to 100 Hz with a response time of 5 ms. Moreover, the introduction of an adhesive and cross-linking layer facilitates robust bonding between the actuator and sensing structure, enabling real-time tracking of the actuation strain without structural interference by a resistance change resolution of 0.01%, providing significant insights for empowering soft robotics with integrated perception and intelligence.

Recent advances in shape memory scaffolds and regenerative outcomes

The advent of tissue engineering (TE) technologies has revolutionized human medicine over the last few decades. Despite splendid advances in the fabricating and development of different substrates for regenerative purposes, non-responsive static composites have been used to heal injured tissues. After being transplanted into the target sites, grafts will lose their original features, leading to a reduction in regenerative potential. Along with these statements, the use of shape memory polymers (SMPs), smart substrates with unique physicochemical properties, has been extended in different disciplines of regenerative medicine in recent years. These substrates are intelligent and they can easily change physicogeometry features such as stiffness, strain size, shape, etc. in response to external stimuli. It has been proposed that SMPs can easily acquire their original properties after deformation, even in the presence or absence of certain stimuli. It has been indicated that the application of distinct synthesis protocols is required to fabricate dynamically switchable surfaces with prominent cell-to-substrate interaction, resulting in better regulation of cell function, dynamic growth, and reparative mechanisms. Here, we aimed to scrutinize the prominent regenerative properties of SMPs in the TE and regenerative medicine fields. Whether and how SMPs can orchestrate certain cell behavior, with reconfigurable features and adaptability were discussed in detail.

Curcumin-loaded polymeric nanomaterials as a novel therapeutic strategy for Alzheimer's disease: A comprehensive review

Alzheimer's disease (AD) stands as a formidable challenge in modern medicine, characterized by progressive neurodegeneration, cognitive decline, and memory impairment. Despite extensive research, effective therapeutic strategies remain elusive. The antioxidant, anti-inflammatory, and neuroprotective properties of curcumin, found in turmeric, have demonstrated promise. The poor bioavailability and rapid systemic clearance of this drug limit its clinical application. This comprehensive review explores the potential of curcumin-loaded polymeric nanomaterials as an innovative therapeutic avenue for AD. It delves into the preparation and characteristics of diverse polymeric nanomaterial platforms, including liposomes, micelles, dendrimers, and polymeric nanoparticles. Emphasis is placed on how these platforms enhance curcumin's bioavailability and enable targeted delivery to the brain, addressing critical challenges in AD treatment. Mechanistic insights reveal how these nanomaterials modulate key AD pathological processes, including amyloid-beta aggregation, tau phosphorylation, oxidative stress, and neuroinflammation. The review also highlighted the preclinical studies demonstrate reduced amyloid-beta plaques and neuroinflammation, alongside improved cognitive function, while clinical trials show promise in enhancing curcumin's bioavailability and efficacy in AD. Additionally, it addresses the challenges of clinical translation, such as regulatory issues, large-scale production, and long-term stability. By synthesizing recent advancements, this review underscores the potential of curcumin-loaded polymeric nanomaterials to offer a novel and effective therapeutic approach for AD, aiming to guide future research and development in this field.

Self-supported polypyrrole flexible electrodes for electrochemical reduction of nitrite

The efficiency of an electrochemical oxidation/reduction process strongly depends on the working electrode's surface area to volume ratio. By making electrodes flexible and employing different configurations such as roll-to-roll membrane, the surface area to volume ratio can be enhanced, therefore improving the overall efficiency of electrochemical processes. Conductive polymers emerge as a new framework to enable alternative electrochemical water treatment cell configurations. Self-standing polypyrrole flexible electrodes were synthesized by electropolymerization and evaluated on the treatment of an oxyanion pollutant: nitrite. Mechanical characterization through stress-strain curves and bending tests demonstrated high electrode resilience that sustained over 1000 bending cycles without impacting mechanical integrity or electrocatalytic responses. The electrocatalytic response towards nitrite reduction was assessed under linear scan voltammetry (LSV) and removal performance evaluated under potentiostatic conditions reaching 79% abatement of initial concentrations of nitrite of 15 mg/L [NO2--N]. Self-standing flexible electrodes appear as a novel framework to enable modular compact water treatment unit designs that maximize the electrode area/volume ratio and substitute expensive platinum group metal (PGMs) electrocatalysts.

Functionalized hydrogels in neural injury repairing

Repairing injuries to the nervous system has always been a prominent topic in clinical research. Direct suturing and nerve displacement surgery are the primary treatment options, but they may not be suitable for long nerve injuries and may require sacrificing the functionality of other autologous nerves. With the emergence of tissue engineering, hydrogel materials have been identified as a promising technology with clinical translation potential for repairing nervous system injuries due to their excellent biocompatibility and ability to release or deliver functional ions. By controlling their composition and structure, hydrogels can be Functionalized and almost fully matched with nerve tissue and even simulate nerve conduction function and mechanical properties. Thus, they are suitable for repairing injuries to both the central and peripheral nervous systems. This article provides a review of recent research progress in functionalized hydrogels for nerve injury repair, highlighting the design differences among various materials and future research directions. We strongly believe that the development of functionalized hydrogels has great potential for improving the clinical treatment of nerve injuries.

Advanced stimuli-responsive membranes for smart separation

Membranes have been extensively studied and applied in various fields owing to their high energy efficiency and small environmental impact. Further conferring membranes with stimuli responsiveness can allow them to dynamically tune their pore structure and/or surface properties for efficient separation performance. This review summarizes and discusses important developments and achievements in stimuli-responsive membranes. The most commonly utilized stimuli, including light, pH, temperature, ions, and electric and magnetic fields, are discussed in detail. Special attention is given to stimuli-responsive control of membrane pore structure (pore size and porosity/connectivity) and surface properties (wettability, surface topology, and surface charge), from the perspective of determining the appropriate membrane properties and microstructures. This review also focuses on strategies to prepare stimuli-responsive membranes, including blending, casting, polymerization, self-assembly, and electrospinning. Smart applications for separations are also reviewed as well as a discussion of remaining challenges and future prospects in this exciting field. This review offers critical insights for the membrane and broader materials science communities regarding the on-demand and dynamic control of membrane structures and properties. We hope that this review will inspire the design of novel stimuli-responsive membranes to promote sustainable development and make progress toward commercialization.

Bioinspired polypyrrole based fibrillary artificial muscle with actuation and intrinsic sensing capabilities

A non-conventional, bioinspired device based on polypyrrole coated electrospun fibrous microstructures, which simultaneously works as artificial muscle and mechanical sensor is reported. Fibrous morphology is preferred due to its high active surface which can improve the actuation/sensing properties, its preparation still being challenging. Thus, a simple fabrication algorithm based on electrospinning, sputtering deposition and electrochemical polymerization produced electroactive aligned ribbon meshes with analogous characteristics as natural muscle fibers. These can simultaneously generate a movement (by applying an electric current/potential) and sense the effort of holding weights (by measuring the potential/current while holding objects up to 21.1 mg). Electroactivity was consisting in a fast bending/curling motion, depending on the fiber strip width. The amplitude of the movement decreases by increasing the load, a behavior similar with natural muscles. Moreover, when different weights were hung on the device, it senses the load modification, demonstrating a sensitivity of about 7 mV/mg for oxidation and - 4 mV/mg for reduction. These results are important since simultaneous actuation and sensitivity are essential for complex activity. Such devices with multiple functionalities can open new possibilities of applications as e.g. smart prosthesis or lifelike robots.

Fabrication of Thermo-Responsive Controllable Shape-Changing Hydrogel

Temperature response double network (DN) hydrogels comprising a network formed by polymerization of methacrylic acid (MA) modified PVA, N,N'-methylene bis(acrylamide), N-isopropylacryl amide (NIPAM), and one formed from crystalline polyvinyl alcohol (PVA) are prepared in a 3D printed tailor-made mold. The (PVA-MA)-g-PNIPAAm thermoset intermediate is formed in water by a radical, photo-initiated process, and in the presence of dissolved PVA polymers. A subsequent freezing-thawing sequence induces the crystallization of the PVA network, which forms a second network inside the thermoset NIPAM polymer. The prepared hydrogel is thermoresponsive by the phase transition of PNIPAAm segments (T ≈ 32 °C) and has good mechanical properties (tensile strength 1.23 MPa, compressive strength 1.47 MPa). Thermal cycling between room temperature at 40 or 50 °C shows the product converses from a virgin-state to a steady-state, which most likely involves the reorganization of PVA crystals. The swelling-deswelling cycles remain clear at a length change of about 13%.