A New Way to Promote Molecular Drug Release during Medical Treatment: A Polyelectrolyte Matrix on a Piezoelectric-Dielectric Energy Conversion Substrate

Ingenious Structure Engineering to Enhance Piezoelectricity in Poly(vinylidene fluoride) for Biomedical Applications

The future development of wearable/implantable sensing and medical devices relies on substrates with excellent flexibility, stability, biocompatibility, and self-powered capabilities. Enhancing the energy efficiency and convenience is crucial, and converting external mechanical energy into electrical energy is a promising strategy for long-term advancement. Poly(vinylidene fluoride) (PVDF), known for its piezoelectricity, is an outstanding representative of an electroactive polymer. Ingeniously designed PVDF-based polymers have been fabricated as piezoelectric devices for various applications. Notably, the piezoelectric performance of PVDF-based platforms is determined by their structural characteristics at different scales. This Review highlights how researchers can strategically engineer structures on microscopic, mesoscopic, and macroscopic scales. We discuss advanced research on PVDF-based piezoelectric platforms with diverse structural designs in biomedical sensing, disease diagnosis, and treatment. Ultimately, we try to give perspectives for future development trends of PVDF-based piezoelectric platforms in biomedicine, providing valuable insights for further research.

Advancing piezoelectric 2D nanomaterials for applications in drug delivery systems and therapeutic approaches

Precision drug delivery and multimodal synergistic therapy are crucial in treating diverse ailments, such as cancer, tissue damage, and degenerative diseases. Electrodes that emit electric pulses have proven effective in enhancing molecule release and permeability in drug delivery systems. Moreover, the physiological electrical microenvironment plays a vital role in regulating biological functions and triggering action potentials in neural and muscular tissues. Due to their unique noncentrosymmetric structures, many 2D materials exhibit outstanding piezoelectric performance, generating positive and negative charges under mechanical forces. This ability facilitates precise drug targeting and ensures high stimulus responsiveness, thereby controlling cellular destinies. Additionally, the abundant active sites within piezoelectric 2D materials facilitate efficient catalysis through piezochemical coupling, offering multimodal synergistic therapeutic strategies. However, the full potential of piezoelectric 2D nanomaterials in drug delivery system design remains underexplored due to research gaps. In this context, the current applications of piezoelectric 2D materials in disease management are summarized in this review, and the development of drug delivery systems influenced by these materials is forecast.

Effective Scald Wound Functional Recovery Patch Achieved by Molecularly Intertwined Electrical and Chemical Message in Self-Adhesive Assemblies

Bioactive materials that communicate with bio-tissues via simultaneous chemical and electrical information promise an advanced medical treatment strategy. Rational design of simultaneous chemically and electrically active materials is still challenging. In this study, we develop a bioactive wound healing patch that enables functional recovery of scald skin wounds by integrating electrically and chemically active units at the molecular level. The patch should be used with massages for 10 min daily during the recovery process. This healing patch consists of a closely intertwined piezoelectric poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF) film and a self-adhesive poly(N,N-dimethylacrylamide) (PDMAA) hydrogel layer, which permits itself to adhere on skin wounds reversibly. Frequency-dependent electrical and chemical dose delivery is achieved in response to mechanical stimuli via the electrical-chemical crosstalk within the healing patch. Animal scald experiments show that the patch can effectively guide the functional recovery of grade I and shallow grade II scald wounds, promoting proper collagen deposition and hair follicle, blood vessel, and gland regeneration. Integrating electrically and chemically active units at the molecular level in treatment devices provides a new design concept for tissue engineering and medical treatment materials.

Nanoporous electroporation needle for localized intracellular delivery in deep tissues

The exogenous control of intracellular drug delivery has been shown to improve the overall efficacy of therapies by reducing nonspecific off-target toxicity. However, achieving a precise on-demand dosage of a drug in deep tissues with minimal damage is still a challenge. In this study, we report an electric-pulse-driven nanopore-electroporation (nEP) system for the localized intracellular delivery of a model agent in deep tissues. Compared with conventional bulk electroporation, in vitro nEP achieved better transfection efficiency (>60%) with a high cell recovery rate (>95%) under a nontoxic low electroporation condition (40 V). Furthermore, in vivo nEP using a nanopore needle electrode with a side drug-releasing compartment offered better control over the dosage release, time, and location of propidium iodide, which was used as a model agent for intracellular delivery. In a pilot study using experimental animals, the nEP system exhibited two times higher transfection efficiency of propidium iodide in the thigh muscle tissue, while minimizing tissue damage (<20%) compared to that of bulk electroporation. This tissue-penetrating nEP platform can provide localized, safe, and effective intracellular delivery of diverse therapeutics into deep tissues in a controlled manner.

In Situ-Forming Gels Loaded with Stimuli-Responsive Gated Mesoporous Silica Nanoparticles for Local Sustained Drug Delivery

A novel combination of in situ-forming hydrogels of hyaluronic acid with gated mesoporous materials was developed to design depots for local sustained release of chemotherapeutics. The depot consists of a hyaluronic-based gel loaded with redox-responsive mesoporous silica nanoparticles loaded with safranin O or doxorubicin and capped with polyethylene glycol chains containing a disulfide bond. The nanoparticles are able to deliver the payload in the presence of the reducing agent, glutathione (GSH), that promotes the cleavage of the disulfide bonds and the consequent pore opening and cargo delivery. Release studies and cellular assays demonstrated that the depot can successfully liberate the nanoparticles to the media and, subsequently, that the nanoparticles are internalized into the cells where the high concentration of GSH induces cargo delivery. When the nanoparticles were loaded with doxorubicin, a significant reduction in cell viability was observed. Our research opens the way to the development of new depots that enhance the local controlled release of chemotherapeutics by combining the tunable properties of hyaluronic gels with a wide range of gated materials.

Breathable Bactericide Piezocatalyst Integrating Anode-Cathode Heterojunction Capacitance on a Piezoelectric-Conductive Film

Piezocatalysis has received great attention in recent years. However, despite the great promise therein, high-performance piezocatalysts are still rare and the principles in designing high-performance piezocatalysts remain lacking. We demonstrate here a novel piezocatalyst design by integrating the oxidizing and reducing reaction sites heterojunction on a piezoelectric and conductive matrix. The catalytic composite generates reactive oxidizing species with unprecedented high capabilities. The •O₂^- yield is over 400% that of previously reported catalysts and for the first time realized effective piezocatalytic bactericidal effects over 99%. A range of structural features, including proper energy band alignments, high capacitance, patterned high conductivity, voltage-regulated wettability, and effective piezoelectrical capability, are believed to synergize for their high piezocatalytic performance. This study has extended the piezocatalysts with new design principles, effective descriptors of merits, new applications, and effective performance capabilities.

Layer-by-Layer Fabrication of PAH/PAMAM/Nano-CaCO3 Composite Films and Characterization for Enhanced Biocompatibility

Nanoparticle production and functionalization for various biomedical uses are still challenging. Polymer composites constituted of poly(amidoamine) (PAMAM), polyallylamine hydrochloride (PAH), and calcium carbonate (CaCO₃) nanoparticles have good biocompatibility with physiological tissue and fluids, making them excellent candidates for biomedical applications. This study investigated the characteristics of polymeric/nano-CaCO₃ composite films based on a PAH/PAMAM matrix, which were fabricated through layer-by-layer synthesis on quartz glass substrates. It was found that the as-prepared elastic moduli of the resultant (PAH/PAMAM)_n-CaCO₃ (where n represents the number of bilayers) composite films varied from 1.40 to 23.70 GPa for different degrees of cross-linking when 0.1 M nano-CaCO₃ particles were incorporated into the polymer matrix. The highly cross-linked (PAH/PAMAM)₁₅-CaCO₃ composite film had the highest recorded elastic modulus of 23.70 GPa, while it was observed that for all the composite films fabricated for the present study, the addition of the nano-CaCO₃ particles approximately doubled the elastic modulus regardless of the degree of polymerization. Live/Dead assays were used to determine whether the produced composite films were compatible with human lung fibroblast cells. The findings indicate that the (PAH/PAMAM)_7.5-CaCO₃ composite film had the most positive effect on cell growth and proliferation, with the (PAH/PAMAM)₁₅-CaCO₃ composite film demonstrating significant ion transport behavior with low impedance, which was considered good for in vivo rapid cell-to-cell communication. Therefore, the (PAH/PAMAM)_7.5-CaCO₃ and (PAH/PAMAM)₁₅-CaCO₃ composite films are potential tissue engineering biomaterials, but further studies are essential to generate more data to evaluate the suitability of these composites for this and other biomedical functions.

A healing promoting wound dressing with tailor-made antibacterial potency employing piezocatalytic processes in multi-functional nanocomposites

Developing a novel antibiotics-free antibacterial strategy is essential for minimizing bacterial resistance. Materials that not only kill bacteria but also promote tissue healing are especially challenging to achieve. Inspired by chemical conversion processes in living organisms, we develop a piezoelectrically active antibacterial device that converts ambient O₂ and H₂O to ROS by piezocatalytic processes. The device is achieved by mounting nanoscopic polypyrrole/carbon nanotube catalyst multilayers onto piezoelectric-dielectric films. Under stimuli by a hand-held massage device, the sterilizing rates for S. aureus and E. coli reach 84.11% and 94.85% after 10 minutes of operation, respectively. The antibacterial substrate at the same time preserves and releases drugs and presents negligible cytotoxicity. Animal experiments demonstrate that daily treatment for 10 minutes using the device effectively accelerates the healing of infected wounds on the backs of mice, promoting hair follicle generation and collagen deposition. We believe that this report provides a novel design approach for antibacterial strategies in medical treatment.

Electroactive Polymers Obtained by Conventional and Non-Conventional Technologies

Electroactive polymers (EAPs), materials that present size/shape alteration in response to an electrical stimulus, are currently being explored regarding advanced smart devices, namely robotics, valves, soft actuators, artificial muscles, and electromechanical sensors. They are generally prepared through conventional techniques (e.g., solvent casting and free-radical polymerization). However, non-conventional processes such as those included in additive manufacturing (AM) are emerging as a novel approach to tune and enhance the electromechanical properties of EAPs to expand the scope of areas for this class of electro-responsive material. This review aims to summarize the published work (from the last five years) in developing EAPs either by conventional or non-conventional polymer processing approaches. The technology behind each processing technique is discussed as well as the main mechanism behind the electromechanical response. The most common polymer-based materials used in the design of current EAPs are reviewed. Therefore, the main conclusions and future trends regarding EAPs obtained by conventional and non-conventional technologies are also given.

Biofriendly molecular and protein release substrate with integrated piezoelectric motivation and anti-oxidative stress capabilities

Self-powered piezoelectrically active molecular or protein delivery devices have provoked great interest in recent years. However, electric fields used to promote delivery or healing may also induce the redox of water or oxygen to generate reactive oxygen species (ROS) and bring unintended oxidative pressure to the organism and harm biological functions. In addition, protein molecules are easily inactivated in the polymer reservoir matrix due to the pull of strong electrostatic effects. In this study, a multifunctional molecular delivery substrate was fabricated by integrating a piezoelectric-dielectric polymeric substrate, nanoscopic polyelectrolyte films and in-film deposited biomimetic porous CaP coating. The piezoelectric substrate promoted molecular release, and the mineralized coating effectively stored molecules or proteins and simultaneously eliminated ROS, reducing the oxidative stress response generated by oxidative pressure. The present work opens a new way for the development of multifunctional and biofriendly drug delivery devices.

Supramolecular dendrimer-containing layer-by-layer nanoassemblies for bioapplications: current status and future prospects

This review provides a comprehensive and critical overview of the supramolecular dendrimer-containing multifunctional layer-by-layer nanoassemblies driven by a multitude of intermolecular interactions for biological and biomedical applications.

Fluoropolymers in biomedical applications: state-of-the-art and future perspectives

Biomedical applications of fluoropolymers in gene delivery, protein delivery, drug delivery, ¹⁹F MRI, PDT, anti-fouling, anti-bacterial, cell culture, and tissue engineering.

Enhanced Electricity Generation and Tunable Preservation in Porous Polymeric Materials via Coupled Piezoelectric and Dielectric Processes

Biological systems and artificial devices convert omnipresent low-frequency and weak mechanical stimulation into electricity for important functions. However, in-depth understanding of the energy conversion, boosting, and preservation processes of the coupled piezo-dielectric phenomenon in polymeric artificial materials is still lacking. In this study, combined experimental and simulation methods are employed to rationalize the process of energy conversion and preservation via a coupled piezo-dielectric phenomena in composite polymeric films. Both the intensity of the transmembrane electric voltages and the kinetic aspects of the energy generation and preservation process are elucidated. The study indicates that composite films consisting of a conductive filler fraction below the percolation threshold, effectively convert low-frequency mechanical stimulation to preserved electrical energy. Interestingly, film structure engineered into porous film has the ability to break the intertwined high-voltage and exhibits a low-preservation-period relationship; it can simultaneously provide high electric field intensity, high induction velocity, and a long preservation period. The model is not only supported by the experiments but is also consistent with the electricity generation and preservation features of other reported piezo-dielectric films. The systematic understanding can facilitate and inspire new device designs to better address the energy, environmental, and biomedical challenges faced by modern societies.

Surface Charge-Mediated Cell-Surface Interaction on Piezoelectric Materials

Cell-material interactions play an essential role in the development of scaffold-based tissue engineering strategies. Cell therapies are still limited in treating injuries when severe damage causes irreversible loss of muscle cells. Electroactive biomaterials and, in particular, piezoelectric materials offer new opportunities for skeletal muscle tissue engineering since these materials have demonstrated suitable electroactive microenvironments for tissue development. In this study, the influence of the surface charge of piezoelectric poly(vinylidene fluoride) (PVDF) on cell adhesion was investigated. The cytoskeletal organization of C2C12 myoblast cells grown on different PVDF samples was studied by immunofluorescence staining, and the interactions between single live cells and PVDF were analyzed using an atomic force microscopy (AFM) technique termed single-cell force spectroscopy. It was demonstrated that C2C12 myoblast cells seeded on samples with net surface charge present a more elongated morphology, this effect being dependent on the surface charge but independent of the poling direction (negative or positive surface charge). It was further shown that the cell deadhesion forces of individual C2C12 cells were higher on PVDF samples with an overall negative surface charge (8.92 ± 0.45 nN) compared to those on nonpoled substrates (zero overall surface charge) (4.06 ± 0.20 nN). These findings explicitly demonstrate that the polarization/surface charge is an important parameter to determine cell fate as it affects C2C12 cell adhesion, which in turn will influence cell behavior, namely, cell proliferation and differentiation.

A layer-by-layer strategy for the scalable preparation of uniform interfacial electrocatalysts with high structural tunability: a case study of a CoNP/N,P-graphene catalyst complex

Electrocatalysts are important for providing clean energy and have attracted intense research attention. All electrocatalysts must function on electrode surfaces; however, interfacial engineering strategies for electrocatalytic structures remain understudied, and scalable preparation methods are especially rare. In this study, we propose a strategy that employs a layer-by-layer (LbL) assembly, subsequent in-film deposition, and calcination to prepare a complex Co nanoparticle (CoNP)/N,P-graphene catalyst on various 2D and 3D electrode surfaces. We delicately adjusted a variety of parameters and demonstrated that our LbL-based method can finely tune the total amount, the doping fraction, and the electronic structure of the complex catalysts, and provide optimal catalytic performance. When prepared on a large piece of carbon cloth, the catalysts showed a highly uniform catalytic performance, demonstrating the capability of our method for scalable fabrication. Our study emphasizes the delicate nature of the interfacial engineering of electrocatalysts, and promotes functional interface design and mechanism studies.

Hydrogels as Potential Nano-, Micro- and Macro-Scale Systems for Controlled Drug Delivery

This review is an extensive evaluation and essential analysis of the design and formation of hydrogels (HGs) for drug delivery. We review the fundamental principles of HGs (their chemical structures, physicochemical properties, synthesis routes, different types, etc.) that influence their biological properties and medical and pharmaceutical applications. Strategies for fabricating HGs with different diameters (macro, micro, and nano) are also presented. The size of biocompatible HG materials determines their potential uses in medicine as drug carriers. Additionally, novel drug delivery methods for enhancing treatment are discussed. A critical review is performed based on the latest literature reports.

A self-powered delivery substrate boosts active enzyme delivery in response to human movements

Stimulated drug releases in response to human movements are highly appealing in medical therapy and various daily uses. However, the design of a mechanically responsive substrate that presents high delivery capacities and can also preserve the activities of sensitive molecules such as enzymes is still challenging. Taking advantage of the recent development in effective piezoelectric flexible films and in molecular delivery devices, we propose a composite delivery substrate that preserves enzyme activities and enhances molecular delivery in response to human movements such as finger presses or massages. The substrate is achieved by combining two parts, which are the energy converting unit and the molecular loading and releasing unit. The energy converting unit is a piezoelectric-dielectric flexible composite film that produces enhanced electricity and preserves the electricity longer compared to a pure piezoelectric polymer. The molecular delivery unit is a layer-by-layer multilayer containing mesoporous silica particles that are assembled at pH 9 but used in neutral solutions. The releases of molecules including small molecules, peptides, and proteins are all accelerated in response to finger presses irrespective of the signs or densities of their charges. More importantly, the enzyme CAT preserves its activity after release from the composite substrates, meaning that the CAT-loaded (PAH/MS)n(PAH/DAS)n@rGO-TFB/PVDF-HFP composite substrate holds promise as a self-powered soothing pad that effectively removes residue H2O2.