The current global health threat by the novel coronavirus disease 2019 (COVID-19) requires an urgent deployment of advanced therapeutic options available. The role of nanotechnology is highly relevant to counter this “virus” nano enemy. Nano intervention is discussed in terms of designing effective nanocarriers to counter the conventional limitations of antiviral and biological therapeutics. This strategy directs the safe and effective delivery of available therapeutic options using engineered nanocarriers, blocking the initial interactions of viral spike glycoprotein with host cell surface receptors, and disruption of virion construction. Controlling and eliminating the spread and reoccurrence of this pandemic demands a safe and effective vaccine strategy. Nanocarriers have potential to design risk-free and effective immunization strategies for severe acute respiratory syndrome coronavirus 2 vaccine candidates such as protein constructs and nucleic acids. We discuss recent as well as ongoing nanotechnology-based therapeutic and prophylactic strategies to fight against this pandemic, outlining the key areas for nanoscientists to step in.

The classic theory of direct-current (DC) insulator-based dielectrophoresis (iDEP) considers that, in order to elicit particle trapping, dielectrophoretic (DEP) velocity counterbalances electrokinetic (EK) motion, that is, electrophoresis (EP) and electro-osmotic flow (EOF). However, the particle velocity DEP component requires empirical correction factors (sometimes as high as 600) to account for experimental observations, suggesting the need for a refined model. Here, we show that, when applied to particle suspensions, a high-magnitude DC uniform electric field induces nonlinear particle velocities, leading to particle flow reversal beyond a critical field magnitude, referred to as the EK equilibrium condition. We further demonstrate that this particle motion can be described through an exploratory induced-charge EP nonlinear model. The model predictions were validated under an insulator-based microfluidic platform demonstrating predictive particle trapping for three different particle sizes (with an estimation error < 10%, not using correction factors). Our findings suggest that particle motion and trapping in “DC-iDEP” devices are dominated by EP and EOF, rather than by DEP effects.

Monitoring of phenolic compounds in the food industry and for environmental and medical applications has become more relevant in recent years. Conventional methods for detection and quantification of these compounds, such as spectrophotometry and chromatography, are time consuming and expensive. However, laccase biosensors represent a fast method for on-line and in situ monitoring of these compounds. We discuss the main transduction principles. We divide the electrochemical principle into amperometric, voltammetric, potentiometric and conductometric sensors. We divide optical transducers into fluorescence and absorption. The amperometric transducer method is the most widely studied and used for laccase biosensors. Optical biosensors present higher sensitivity than the other biosensors. Laccase production is dominated by a few fungus genera: Trametes, Aspergillus, and Ganoderma. We present an overview of laccase biosensors used for the determination of phenolic compounds in industrial application

This paper introduces the concept of continuous chaotic printing, i.e. the use of chaotic flows for deterministic and continuous extrusion of fibers with internal multilayered micro- or nanostructures. Two free-flowing materials are coextruded through a printhead containing a miniaturized Kenics static mixer (KSM) composed of multiple helicoidal elements. This produces a fiber with a well-defined internal multilayer microarchitecture at high-throughput (>1.0 m min−1). The number of mixing elements and the printhead diameter determine the number and thickness of the internal lamellae, which are generated according to successive bifurcations that yield a vast amount of inter-material surface area (∼102 cm2 cm−3) at high resolution (∼10 µm). This creates structures with extremely high surface area to volume ratio (SAV). Comparison of experimental and computational results demonstrates that continuous chaotic 3D printing is a robust process with predictable output. In an exciting new development, we demonstrate a method for scaling down these microstructures by 3 orders of magnitude, to the nanoscale level (∼150 nm), by feeding the output of a continuous chaotic 3D printhead into an electrospinner. The simplicity and high resolution of continuous chaotic printing strongly supports its potential use in novel applications, including—but not limited to—bioprinting of multi-scale layered biological structures such as bacterial communities, living tissues composed of organized multiple mammalian cell types, and fabrication of smart multi-material and multilayered constructs for biomedical applications.

No abstract

Insulator-based dielectrophoresis (iDEP), an efficient technique with great potential for miniaturization, has been successfully applied for the manipulation of a wide variety of bioparticles. When iDEP is applied employing direct current (DC) electric fields, other electrokinetic transport mechanisms are present: electrophoresis and electroosmotic flow. In order to concentrate particles, iDEP has to overcome electrokinetics. This study presents the characterization of electrokinetic flow under the operating conditions employed with iDEP; in order to identify the optimal conditions for particle concentration employing DC-iDEP, microparticle image velocimetry (microPIV) was employed to measure the velocity of 1-microm-diameter inert polystyrene particles suspended inside a microchannel made from glass. Experiments were carried out by varying the properties of the suspending medium (conductivity from 25 to 100 microS/cm and pH from 6 to 9) and the strength of the applied electric field (50-300 V/cm); the velocities values obtained ranged from 100 to 700 microm/s. These showed that higher conductivity and lower pH values for the suspending medium produced the lowest electrokinetic flow, improving iDEP concentration of particles, which decreases voltage requirements. These ideal conditions for iDEP trapping (pH = 6 and sigma(m) = 100 microS/cm) were tested experimentally and with the aid of mathematical modeling. The microPIV measurements allowed obtaining values for the electrokinetic mobilities of the particles and the zeta potential of the glass surface; these values were used with a mathematical model built with COMSOL Multiphysics software in order to predict the dielectrophoretic and electrokinetic forces exerted on the particles; the modeling results confirmed the microPIV findings. Experiments with iDEP were carried out employing the same microparticles and a glass microchannel that contained an array of cylindrical insulating structures. By applying DC electric fields across the insulating structures array, it was seen that the dielectrophoretic trapping was improved when the electrokinetic force was the lowest; as predicted by microPIV measurements and the mathematical model. The results of this study provide guidelines for the selection of optimal operating conditions for improving insulator-based dielectrophoretic separations and have the potential to be extended to bioparticle applications.

Dielectrophoresis (DEP), the motion of particles in nonuniform electric fields, is a nondestructive electrokinetic (EK) transport mechanism can be used to concentrate and separate bioparticles. Traditionally, DEP has been performed employing microelectrodes, an approach that is expensive due to the cost of microelectrode fabrication. An alternative is insulator-based DEP (iDEP), an inexpensive method where nonuniform electric fields are created with arrays of insulating structures. This study presents the effects of operating conditions on the dielectrophoretic behavior of polystyrene microparticles under iDEP. Experiments were performed employing microchannels containing insulating structures that worked as insulators. The parameters varied were pH (8-9) and conductivity (25-100 microS/cm) of the bulk medium, and the magnitude of the applied field (200-850 V/cm). Optimal operating conditions in terms of pH and conductivity were obtained, and the microdevice performance was characterized in terms of concentration factor and minimum electric field required (minimum energy consumption). This is the first report on improving iDEP processes when EOF is present. DEP and EOF have been studied extensively, however, this study integrates the effect of suspending medium characteristics on both EK phenomena. These findings will allow improving the performance of iDEP microdevices achieving the highest concentration fold with the lowest energy consumption.

A mathematical model is implemented to study the performance of an insulator-based dielectrophoretic device. The geometry of the device was captured in a computational model that solves Laplace equation within an array of cylindrical insulating structures. From the mathematical model it was possible to predict the location and magnitude of the zones of dielectrophoretic trapping of microparticles. Simulation and experimental results of trapping zones are compared for different operating conditions.