Nanostructured Conductive Polypyrrole for Antibacterial Components in Flexible Wearable Devices

Self-healing Ppy-hydrogel promotes diabetic skin wound healing through enhanced sterilization and macrophage orchestration triggered by NIR

Non-healing diabetic foot ulcers are the knotty public health issue due to the uncontrolled bacterial infection, prolonged inflammation, and inferior vessel remodeling. In this work, polypyrrole (Ppy) was added into the hybrid hydrogel containing polyvinyl alcohol (PVA), polyethylene glycol (PEG), and hyaluronan (HA) to acquire superior mechanism and photothermal ability. The Ppy composited hybrid hydrogel could effectively kill bacteria through accumulating heat on the hydrogel surface. RNA-Seq analysis shows that the heat accumulation could enhance phagosome of macrophage and M1 activation, which further accelerate bacteria clearance. Benefitting from the bacteria clearance, macrophage could transform its phenotype to M2 in Ppy composited hybrid hydrogel group with near infrared light (NIR) stimulation. The related genes expression in keratinization, keratinocyte differentiation, and establishment of the skin barrier in the skin were up-regulated and collagen and vascular endothelial growth factor (VEGF) expression level are also enhanced. In summary, Ppy composited hybrid hydrogel could effectively solve the issues of infection and poor wound healing in diabetic foot ulcers, making it an ideal candidate dressing for the treatment of chronic wounds.

Additively Manufactured Flexible EGaIn Sensor for Dynamic Detection and Sensing on Ultra-Curved Surfaces

Electronic skin is widely employed in multiple applications such as health monitoring, robot tactile perception, and bionic prosthetics. In this study, we fabricated millimeter-scale electronic skin featuring compact sensing units using the Boston Micro Fabrication S130 (a high-precision additive manufacturing device) and the template removal method. We used a gallium-based liquid metal and achieved an inner channel diameter of 0.1 mm. The size of the sensing unit was 3 × 3 mm2. This unit exhibited a wide linear sensing range (10-22,000 Pa) and high-pressure resolution (10 Pa) even on an ultra-curved surface (radius of curvature was 6 mm). Sliding was successfully detected at speeds of 8-54 mm/s. An artificial nose with nine sensing units was fabricated, and it exhibited excellent multitouch and sliding trajectory recognition capabilities. This confirmed that the electronic skin functioned normally, even on an ultra-curved surface.

Stearic Acid as Polymerization Medium, Dopant and Hydrophobizer: Chemical Oxidative Polymerization of Pyrrole

In recent years, fatty acids have garnered significant attention as a natural phase-change material and a hydrophobizer due to their biocompatibility and biodegradability. In this study, the utilization of fatty acid is proposed as a polymerization medium for the first time. As a specific reaction, chemical oxidative polymerizations of pyrrole is conducted using ferric chloride as an oxidant in a stearic acid medium. The polymerizations resulted in the production of micrometer-sized polypyrrole (PPy) grains, which are aggregates of atypical primary particles with submicrometer size. The PPy grains are doped with stearic acid, suggesting that the stearic acid functioned as a dopant and a hydrophobizing agent as well as a polymerization medium. The dried PPy grains can adsorb at the air-water interface and function as a liquid marble stabilizer with light-to-heat photothermal properties. The liquid marble can move on a planar air-water interface by Marangoni flow induced by NIR laser light irradiation.

Hydrophobic TPU/CNTs-ILs Ionogel as a Reliable Multimode and Flexible Wearable Sensor for Motion Monitoring, Information Transfer, and Underwater Sensing

Ionogel-based sensors have gained widespread attention in recent years due to their excellent flexibility, biocompatibility, and multifunctionality. However, the adaptation of ionogel-based sensors in extreme environments (such as humid, acidic, alkaline, and salt environments) has rarely been studied. Here, thermoplastic polyurethane/carbon nanotubes-ionic liquids (TPU/CNTs-ILs) ionogels with a complementary sandpaper morphology on the surface were prepared by a solution-casting method with a simple sandpaper as the template, and the hydrophobic flexible TPU/CNTs-ILs ionogel-based sensor was obtained by modification using nanoparticles modified with cetyltrimethoxysilane. The hydrophobicity improves the environmental resistance of the sensor. The ionogel-based sensor exhibits multimode sensing performance and can accurately detect response signals from strain (0-150%), pressure (0.1-1 kPa), and temperature (30-100 °C) stimuli. Most importantly, the hydrophobic TPU/CNTs-ILs ionogel-based sensors can be used not only as wearable strain sensors to monitor human motion signals but also for information transfer, writing recognition systems, and underwater activity monitoring. Thus, the hydrophobic TPU/CNTs-ILs ionogel-based sensor offers a new strategy for wearable electronics, especially for applications in extreme environments.

Refining and in-situ growth of polyaniline endows the cellulose fibers with electrical stimulation sterilization

Bacteria and virus infections have posed a great threat to public health and personnel safety. For realizing rapid sterilization of the bacteria and virus, electrical stimulation sterilization was adopted to endow cellulose fibers with instantaneous antibacterial and antiviral properties. In the proposed strategy, the fiber is fluffed by mechanical refining, and then by means of the hydrogen bond between hydroxyl and aniline, the polyaniline (PANI) directionally grows vertically along the fine fibers via in-situ oxidative polymerization. Benefiting from the conductive polyaniline nanorod arrays on the fiber stem, the paper made from PANI modified refined fibers (PANI/BCF/P) exhibited excellent antibacterial and antiviral activity, the inhibition rates against S. aureus, E. coli, and bacteriophage MS2 can up to 100 %, 100 %, and 99.89 %, respectively when a weak voltage (2.5 V) was applied within 20 min. This study provides a feasible path for plant fiber to achieve efficient antibacterial and antiviral activity with electrical stimulation, which is of great significance for the preparation of electroactive antibacterial and antiviral green health products.

A bio-fabricated tesla valves and ultrasound waves-powered blood plasma viscometer

Introduction: There is clinical evidence that the fresh blood viscosity is an important indicator in the development of vascular disorder and coagulation. However, existing clinical viscosity measurement techniques lack the ability to measure blood viscosity and replicate the in-vivo hemodynamics simultaneously. Methods: Here, we fabricate a novel digital device, called Tesla valves and ultrasound waves-powered blood plasma viscometer (TUBPV) which shows capacities in both viscosity measurement and coagulation monitoring. Results: Based on the Hagen-Poiseuille equation, viscosity analysis can be faithfully performed by a video microscopy. Tesla-like channel ensured unidirectional liquid motion with stable pressure driven that was triggered by the interaction of Tesla valve structure and ultrasound waves. In few seconds the TUBPV can generate an accurate viscosity profile on clinic fresh blood samples from the flow time evaluation. Besides, Tesla-inspired microchannels can be used in the real-time coagulation monitoring. Discussion: These results indicate that the TUBVP can serve as a point-of-care device in the ICU to evaluate the blood's viscosity and the anticoagulation treatment.

Antibacterial conductive polyacrylamide/quaternary ammonium chitosan hydrogel for electromagnetic interference shielding and strain sensing

The utilization of biomass-based conductive polymer hydrogels in wearable electronics holds great promise for advancing performance and sustainability. An interpenetrating network of polyacrylamide/2-hydroxypropyltrimethyl ammonium chloride chitosan (PAM/HACC) was firstly obtained through thermal-initiation polymerization of AM monomers in the presence of HACC. The positively charged groups on HACC provide strong electrostatic interactions and hydrogen bonding with the PAM polymer chains, leading to improved mechanical strength and stability of the hydrogel network. Subsequently, the PAM/HACC networks served as the skeletons for the in-situ polymerization of polypyrrole (PPy), and then the resulting conductive hydrogel demonstrated stable electromagnetic shielding performance (40 dB), high sensitivity for strain sensing (gauge factor = 2.56). Moreover, the incorporation of quaternary ammonium chitosan into PAM hydrogels enhances their antimicrobial activity, making them more suitable for applications in bacterial contamination or low-temperature environments. This conductive hydrogel, with its versatility and excellent mechanical properties, shows great potential in applications such as electronic skin and flexible/wearable electronics.

Interdisciplinary-Inspired Smart Antibacterial Materials and Their Biomedical Applications

The discovery of antibiotics has saved millions of lives, but the emergence of antibiotic-resistant bacteria has become another problem in modern medicine. To avoid or reduce the overuse of antibiotics in antibacterial treatments, stimuli-responsive materials, pathogen-targeting nanoparticles, immunogenic nano-toxoids, and biomimetic materials are being developed to make sterilization better and smarter than conventional therapies. The common goal of smart antibacterial materials (SAMs) is to increase the antibiotic efficacy or function via an antibacterial mechanism different from that of antibiotics in order to increase the antibacterial and biological properties while reducing the risk of drug resistance. The research and development of SAMs are increasingly interdisciplinary because new designs require the knowledge of different fields and input/collaboration from scientists in different fields. A good understanding of energy conversion in materials, physiological characteristics in cells and bacteria, and bactericidal structures and components in nature are expected to promote the development of SAMs. In this review, the importance of multidisciplinary insights for SAMs is emphasized, and the latest advances in SAMs are categorized and discussed according to the pertinent disciplines including materials science, physiology, and biomimicry.

Type I photodynamic antimicrobial therapy: Principles, progress, and future perspectives

The emergence of drug-resistant bacteria has significantly diminished the efficacy of existing antibiotics in the treatment of bacterial infections. Consequently, the need for finding a strategy capable of effectively combating bacterial infections has become increasingly urgent. Photodynamic therapy (PDT) is considered one of the most promising emerging antibacterial strategies due to its non-invasiveness, low adverse effect, and the fact that it does not lead to the development of drug resistance. However, bacteria at the infection sites often exist in the form of biofilm instead of the planktonic form, resulting in a hypoxic microenvironment. This phenomenon compromises the treatment outcome of oxygen-dependent type-II PDT. Compared to type-II PDT, type-I PDT is not constrained by the oxygen concentration in the infected tissues. Therefore, in the treatment of bacterial infections, type-I PDT exhibits significant advantages over type-II PDT. In this review, we first introduce the fundamental principles of type-I PDT in details, including its physicochemical properties and how it generates reactive oxygen species (ROS). Next, we explore several specific antimicrobial mechanisms utilized by type-I PDT and summarize the recent applications of type-I PDT in antimicrobial treatment. Finally, the limitations and future development directions of type-I photosensitizers are discussed. STATEMENT OF SIGNIFICANCE: The misuse and overuse of antibiotics have accelerated the development of bacterial resistance. To achieve the effective eradication of resistant bacteria, pathfinders have devised various treatment strategies. Among these strategies, type I photodynamic therapy has garnered considerable attention owing to its non-oxygen dependence. The utilization of non-oxygen-dependent photodynamic therapy not only enables the effective elimination of drug-resistant bacteria but also facilitates the successful eradication of hypoxic biofilms, which exhibits promising prospects for treating biofilm-associated infections. Based on the current research status, we anticipate that the novel type I photodynamic therapy agent can surmount the biofilm barrier, enabling efficient treatment of hypoxic biofilm infections.

Cotton Fibers with a Lactic Acid-Like Surface for Re-establishment of Protective Lactobacillus Microbiota by Selectively Inhibiting Vaginal Pathogens

Failure to reconstruct the Lactobacillus microbiota is the major reason for the recurrence of vaginal infection. However, most empiric therapies focus on the efficacy of pathogen elimination but do not sufficiently consider the viability of Lactobacillus. Herein, cotton fibers with a lactic acid-like surface (LC) are fabricated by NaIO4 oxidation and L-isoserine grafting. The lactic acid analog chain ends and imine structure of LC can penetrate cell walls to cause protein cleavage in Escherichia coli and Candida albicans and inhibit vaginal pathogens. Meanwhile, the viability of Lactobacillus acidophilus is unaffected by the LC treatment, thus revealing a selective way to suppress pathogens as well as provide a positive route to re-establish protective microbiota in the vaginal tract. Moreover, LC has excellent properties such as good biosafety, antiadhesion, water absorption, and weight retention. The strategy proposed here not only is practical, but also provides insights into the treatment of vaginal infections.

Capillary-Assisted Assembly of Soft Conductive Polymer Nanopillar/Tube Arrays and Applications

Nanopillar/tube arrays have emerged as encouraging platforms, possessing remarkable advantages, including large specific areas and highly aligned orientations. Despite the progress of nano/microfabrication technologies, facile and controllable fabrication of conductive polymer nanopillar/tube arrays remains challenging. In this study, we demonstrate that the air-liquid interfacial self-assembly can be extended to obtain three-dimensional nanostructured arrays. A smart and novel method is proposed for preparing uniform conductive polymer nanopillar/tube arrays by a template-mediated interfacial synthesis approach. By utilizing capillary force, precise control processes of the nanostructure and patterned structure can be easily realized. Furthermore, a transfer strategy is devised, allowing for scalable fabrication and expansion of the applicability. Applications, including antibacterial surfaces and actuators, have been demonstrated. We extend the air-liquid interfacial synthesis technique as a powerful and universal strategy for producing ordered nanopillar/tube arrays and show the great potential of soft nanostructured arrays as advanced platforms in diverse applications.