PVDF as a Biocompatible Substrate for Microfluidic Fuel Cells

A reliable, flexible, and biocompatible power source for implantable and wearable devices has always been one of the biggest challenges for medical device design engineers. Microfluidic fuel cells (MFCs) are one of the candidates to generate a constant and reliable energy. However, the aspects of this approach, such as use of expensive materials, limitation of achievable power density and biocompatibility, have not yet been fully addressed. These challenges have restricted the application of MFCs to lab-on-chip systems that are deemed to be promising for implantable medical devices. Recently, porous materials such as natural papers and synthetic polymers (in the form of either nanofibers or porous membranes), when used as the MFC substrate, have shown that they can address the above-mentioned challenges. More importantly, these porous materials induce an inherent capillary flow in the fuel, eliminating the need of a pump. This may lead to an increased fuel efficiency and miniaturization of MFCs. However, the search for a porous biomaterial that displays high mechanical strength but remains flexible without degrading in a biological environment is not straightforward. In this research, Polyvinylidene Fluoride (PVDF), a non-biodegradable, biocompatible, flexible, and inexpensive material, was investigated for the first time as a channel substrate in a dynamic state MFC. To achieve the desired porosity, flexibility, and material strength of the substrate, PVDF nanofibers were fabricated using the electrospinning technique. Furthermore, hydrophilic PVDF nanofibers were successfully achieved by oxygen plasma surface treatment. The desired PVDF-based MFC was conceptualized using Axiomatic Design Theory (ADT) and FCBPSS (F: function, C: context, B: behavior, P: principle, SS: structure-state) methods. To investigate the electrochemical output of the designed PVDF-based MFC, a hydrophilic porous PVDF membrane was used as the substrate to induce a capillary action in the fuel (hydrogen peroxide). The PVDF-based MFC studied here successfully produced a power density of 0.158 mW/cm^2 at 0.08 V that is ~60% higher compared to the previous dynamic state paper-based biofuel cell reported in the literature. Moreover, the power density of MFC studied here is comparable to previous studies of static state single compartment MFCs using the same fuel type and concentration. Therefore, the results from this work demonstrate, for the first time, that the porous PVDF is a suitable material for the channel substrate in a dynamic state MFC. The potential application of this cell, in medicine, is utilizing the hydrophilic porous PVDF in electrochemical, implantable, and wearable medical devices. This approach can also be applied to any self-powered point-of-care diagnostic system

Artificial Rheotaxis

Motility is a basic feature of living microorganisms, and how it works is often determined by environmental cues. Recent efforts have focused on develop- ing artificial systems that can mimic microorganisms, and in particular their self-propulsion. Here, we report on the design and characterization of syn- thetic self-propelled particles that migrate upstream, known as positive rheo- taxis. This phenomenon results from a purely physical mechanism involving the interplay between the polarity of the particles and their alignment by a viscous torque. We show quantitative agreement between experimental data and a simple model of an overdamped Brownian pendulum. The model no- tably predicts the existence of a stagnation point in a diverging flow. We take advantage of this property to demonstrate that our active particles can sense and predictably organize in an imposed flow. Our colloidal system represents an important step towards the realization of biomimetic micro-systems withthe ability to sense and respond to environmental changesComment: Published in Science Advances [Open access journal of Science Magazine

Ultrafast Directional Janus Pt-Mesoporous Silica Nanomotors for Smart Drug Delivery

[EN] Development of bioinspired nanomachines with an efficient propulsion and cargo-towing has attracted much attention in the last years due to their potential biosensing, diagnostics, and therapeutics applications. In this context, self-propelled synthetic nanomotors are promising carriers for intelligent and controlled release of therapeutic payloads. However, the implementation of this technology in real biomedical applications is still facing several challenges. Herein, we report the design, synthesis, and characterization of innovative multifunctional gated platinum¿mesoporous silica nanomotors constituted of a propelling element (platinum nanodendrite face), a drug-loaded nanocontainer (mesoporous silica nanoparticle face), and a disulfide-containing oligo(ethylene glycol) chain (S¿S¿PEG) as a gating system. These Janus-type nanomotors present an ultrafast self-propelled motion due to the catalytic decomposition of low concentrations of hydrogen peroxide. Likewise, nanomotors exhibit a directional movement, which drives the engines toward biological targets, THP-1 cancer cells, as demonstrated using a microchip device that mimics penetration from capillary to postcapillary vessels. This fast and directional displacement facilitates the rapid cellular internalization and the on-demand specific release of a cytotoxic drug into the cytosol, due to the reduction of the disulfide bonds of the capping ensemble by intracellular glutathione levels. In the microchip device and in the absence of fuel, nanomotors are neither able to move directionally nor reach cancer cells and deliver their cargo, revealing that the fuel is required to get into inaccessible areas and to enhance nanoparticle internalization and drug release. Our proposed nanosystem shows many of the suitable characteristics for ideal biomedical destined nanomotors, such as rapid autonomous motion, versatility, and stimuli-responsive controlled drug release.The authors want to thank the Spanish Government for RTI2018-100910-B-C41 (MCIU/AEI/FEDER, UE) and CTQ2017-87954-P projects and the Generalitat Valenciana for support by project PROMETEO/2018/024. P.D. thanks the Spanish government for her Juan de la Cierva postdoctoral fellowship. E.L.-S. thanks MINECO for her FPU fellowship. A.E. is also grateful for her Ph.D. grant by the Generalitat Valenciana.Diez-Sánchez, P.; Lucena-Sánchez, E.; Escudero-Noguera, A.; Llopis-Lorente, A.; Villalonga, R.; Martínez-Máñez, R. (2021). Ultrafast Directional Janus Pt-Mesoporous Silica Nanomotors for Smart Drug Delivery. ACS Nano. 15(3):4467-4480. https://doi.org/10.1021/acsnano.0c084044467448015

A concise review of microfluidic particle manipulation methods

Particle manipulation is often required in many applications such as bioanalysis, disease diagnostics, drug delivery and self-cleaning surfaces. The fast progress in micro- and nano-engineering has contributed to the rapid development of a variety of technologies to manipulate particles including more established methods based on microfluidics, as well as recently proposed innovative methods that still are in the initial phases of development, based on self-driven microbots and artificial cilia. Here, we review these techniques with respect to their operation principles and main applications. We summarize the shortcomings and give perspectives on the future development of particle manipulation techniques. Rather than offering an in-depth, detailed, and complete account of all the methods, this review aims to provide a broad but concise overview that helps to understand the overall progress and current status of the diverse particle manipulation methods. The two novel developments, self-driven microbots and artificial cilia-based manipulation, are highlighted in more detail