Liquid-metal-based stretchable bioelectronics can conform to the dynamic movements of tissues and enable human-interactive biosensors to monitor various physiologic parameters. However, the fluidic nature, surface oxidation, and low biostability of the liquid metals have limited the long-term use of bioelectronics. Here we have developed a rationally designed material engineering approach to overcome these challenges in liquid metal bioelectronics. To our knowledge, this is the first demonstration of stretchable, leak-free, and highly conductive gallium-based bioelectronic devices with exceptional biostability and electrochemical properties. We first utilized unique gallium oxide properties to create 3D microscale wrinkled structures on the gallium surface. Then, gold nanoparticles and biostable poly(3,4-ethylenedioxythiophene) were successively deposited on the wrinkled liquid metal surface. We demonstrated this multilayer encapsulation material could conform to the stretching deformation and showed excellent environmental stabilities while maintaining high electrical properties. Electromyographic measurements were used to evaluate the bioelectrical performance of the stretchable electronics, and the results demonstrated the encapsulated liquid metal device could outperform bare liquid metal devices. Finally, a sensory feedback study demonstrated our liquid metal bioelectronic device could record precise physiologic signals to control robots for mimicking dexterous hand gestures. This study opens the possibility of chronic liquid-metal-based stretchable bioelectronics.
The carbon fiber/metal nanoparticle hybrid structure is a widely studied material combination for various fields such as energy storage, highperformance composites, and biomedical tools. The versatile carbon fiber/gold nanoparticle structure was prepared using an eco-friendly and energy-efficient fabrication process to address the sustainability issue. First, cellulose fiber was prepared by an eco-friendly lyocell process. The study obtained high mechanical strength of the lyocell fiber through high cellulose contents, strict pulp dissolution conditions, modified spinning, and thermal elongation processes. Then, the lyocell fiber was changed to carbon fiber with stabilization under 5% tension and carbonization, resulting in high mechanical strength and Young's modulus. Finally, gold nanoparticles were electrochemically deposited on the lyocell-based carbon fiber surface. The electrochemical properties of the carbon fiber/gold nanoparticle system were drastically improved due to the high surface area of the nanostructured gold particles. Enhanced electrochemical property and biocompatibility from non-toxic material selection enabled the carbon fiber/gold nanoparticles for dopamine detection, a representative electrochemical biosensor. The detection result demonstrated that the hybrid structure provided high sensitivity and selectivity for dopamine sensing. Overall, this fabrication strategy opens up numerous application opportunities to address eco-friendly and sustainable development requirements.
Liquid metals (LMs) have gained great attention due to their fluidic behavior and metallic characteristics, suggesting the LMs to be an ideal electrode material for stretchable electronic textiles (e-textiles) in real-time healthcare systems. Despite advancements in material design techniques enabling LMs to monitor physiologic conditions on the skin, the low biostability of LMs remains challenging for practical use in e-textile. Here, we introduce a mechanically responsive and conductive gold nanoparticle (Au NP) layer as encapsulation on the LM layer to monitor healthcare systems with stretchable benefits. The Au NPencapsulated LM-based e-textile (AuLM textile) shows high electrical and mechanical stabilities under stretching deformation. We also demonstrate that Au NPs can maintain bonding to the fluidic LM layer when stretched and after stretching. The AuLM textile is equipped with biocompatibility and high electrochemical performance, resulting in multimodal biomedical applications. The electrochemical performance of the AuLM textile allows for sweat component detection and noninvasive, high sensitivity estimation of blood sugar contents. In addition, electrocardiography and electromyography measurements determined that the stretchable platform provides stable monitoring results under motion, and the Au NP encapsulation solves the biostability issue caused by a bare LM environment. This is the first demonstration of preparing stretchable e-textiles using the LM platform with practical and multimodal benefits. The study will open numerous design opportunities for next-generation stretchable bioelectronic applications.
Currently, neurointervention, surgery, medication, and central nervous system (CNS) stimulation are the main treatments used in CNS diseases. These approaches are used to overcome the blood brain barrier (BBB), but they have limitations that necessitate the development of targeted delivery methods. Thus, recent research has focused on spatiotemporally direct and indirect targeted delivery methods because they decrease the effect on nontarget cells, thus minimizing side effects and increasing the patient’s quality of life. Methods that enable therapeutics to be directly passed through the BBB to facilitate delivery to target cells include the use of nanomedicine (nanoparticles and extracellular vesicles), and magnetic field-mediated delivery. Nanoparticles are divided into organic, inorganic types depending on their outer shell composition. Extracellular vesicles consist of apoptotic bodies, microvesicles, and exosomes. Magnetic field-mediated delivery methods include magnetic field-mediated passive/actively-assisted navigation, magnetotactic bacteria, magnetic resonance navigation, and magnetic nanobots—in developmental chronological order of when they were developed. Indirect methods increase the BBB permeability, allowing therapeutics to reach the CNS, and include chemical delivery and mechanical delivery (focused ultrasound and LASER therapy). Chemical methods (chemical permeation enhancers) include mannitol, a prevalent BBB permeabilizer, and other chemicals—bradykinin and 1-O-pentylglycerol—to resolve the limitations of mannitol. Focused ultrasound is in either high intensity or low intensity. LASER therapies includes three types: laser interstitial therapy, photodynamic therapy, and photobiomodulation therapy. The combination of direct and indirect methods is not as common as their individual use but represents an area for further research in the field. This review aims to analyze the advantages and disadvantages of these methods, describe the combined use of direct and indirect deliveries, and provide the future prospects of each targeted delivery method. We conclude that the most promising method is the nose-to-CNS delivery of hybrid nanomedicine, multiple combination of organic, inorganic nanoparticles and exosomes, via magnetic resonance navigation following preconditioning treatment with photobiomodulation therapy or focused ultrasound in low intensity as a strategy for differentiating this review from others on targeted CNS delivery; however, additional studies are needed to demonstrate the application of this approach in more complex in vivo pathways.
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