A critical comparison of the main parameters playing a role in measurement of electrophoretic mobility of plastic nanoparticles (NPs) by CE and laser Doppler velocimetry (LDV) techniques in NP suspensions is herein presented, accompanied by a discussion about potential impact on different mobility values observed. Capillary material and dynamic or permanent coating of the inner capillary wall, capillary dimensions, EOF variability, BGE temperature, Joule heating, and presence of species potentially interacting with analyzed NPs are underlined as possible causes of the different performance of the above two techniques. It is of importance to get an insight into the reasons behind experimental conditions and operating features to opt for one technique or the other based on research interests. In the end, it is intended to present a knowledge expansion about two parallel paths that converge in a distinctive parameter of an enormous relevance in CE, effective electrophoretic mobility, not achievable by other techniques, and discuss practical considerations in experimental design.
We present the coupling of capillary electrophoresis to a custom-built high-resolution ion mobility spectrometer (IMS). This system integrates a shifted inlet potential IMS configuration with a customised nanoflow ESI sheath interface. It enables the rapid analysis of quaternary ammonium compounds (QACs) and their impurities in real-world samples. It allowed the detection of six non-chromophoric compounds in about 3 min. The assignment of the IMS signals to compounds was supported by matching experimentally determined collision cross-section (CCS) values with predicted values. The system achieved a detection limit in the single-digit picogram range with IMS resolutions of over 80.
Various forms of dielectrophoresis and higher order electrokinetic effects are being increasingly investigated and used to precisely and accurately manipulate micro and nanoparticles within microfluidic devices. The types of particles span ∼10 nm to hundreds of microns in diameter and are composed of minerals, polymers, biological materials, and complex mixtures. Some studies focused on the selective isolation and concentration of purified particles countering negative dielectrophoretic forces against flow and electrophoretic effects. Similar studies are presented here examining the behaviors of small inorganic particles (10 nm diameter) where their collective actions are inconsistent with negative dielectrophoretic effects and were consistent overall with positive dielectrophoresis (DEP). Positive DEP can account for some of the observed phenomena, particularly the deflection of large particle aggregates, which are rapidly accelerated through microchannel constrictions and then pulled back toward the constrictions against the direction of electroosmotic flow. Nevertheless, the dynamic complexity of the observed nanoparticle structures suggests that a myriad of electrostatic and possibly hydrodynamic forces, including both particle–particle and particle–device interactions, may be involved.
As an emerging functional material, liquid metal has attracted extensive attention due to its unique physical/chemical properties. Particularly, the combination of the intrinsic fluidity with rapidly stimuli-responsiveness to electrical field endows it potential as soft actuators to be employed in soft robots. Herein, we developed a small controllable vehicle driven by electrically actuated Galinstan droplets. A series of experiments were carried out to evaluate the vehicle's performance, including straight translational locomotion at various speeds and rotational motion from different starting angles. And then, the vehicle's excellent mobility is further demonstrated through its ability to follow complex trajectories. More importantly, by redesigning the vehicle's frame, it can be adapted for multiple functions, such as cargo transportation and loading/unloading tasks. The present finding is envisaged to have the potential to expand current research on soft robot and further advance the development of micro-factory.
A capillary electrophoresis system capable of measuring streaming potentials was used for the determination of critical micelle concentration (CMC) of anionic, cationic, zwitterionic and non-ionic surfactants. The CMC values of anionic surfactant sodium dodecyl sulphate (SDS), cationic surfactant cetyltrimethylammonium bromide (CTAB), zwitterionic surfactant 3-((3-cholamidopropyl) dimethylammonio)-1-propanesulfonate (CHAPS) and non-ionic surfactant polyethylene glycol p-(1,1,3,3-tetramethylbutyl)-phenyl ether (Triton X-100) in water or salt solutions were determined by determining the abrupt change in the trend of streaming potential change with the surfactant concentration. The CMC values were 8.23, 0.93, 5.80 and 0.16 mM, respectively. This method was also used to demonstrate how the CMCs of SDS and CTAB change differently with temperature. The CMC of SDS decreased from 10°C to 25°C and then increased from 25°C to 40°C, whereas CTAB only increased linearly within 10°C–40°C. The capillary wall zeta potentials in surfactant solutions can be calculated from the measured streaming potential, conductivity and solution viscosity. Surface charge densities were calculated using the zeta potentials obtained. The surface charge densities of SDS were calculated to be 5.6–0.8 C/m2 when SDS solutions with concentrations of 2–20 mM zeta potentials were used. The calculated zeta potentials and surface charge densities reached a plateau at about 8 mM, which coincided with the CMC of SDS determined in the present study and the literature values. The CMC values obtained from streaming potential measurement are comparable to values obtained with other CMC determination techniques such as surface tension and conductometric measurements.
Cancer is among the most significant health threats to humanity. As a critical front-line treatment in the early stages of the disease, chemotherapy drugs provide positive effects on more than one disease. Traditional analytical methods for screening these drugs are often marred by the need for intricate sample preparation and reliance on costly equipment or reagents. In this study, we profiled the biophysical properties of cancer cells (MCF-7) as they traversed a detection region using a high-throughput seven-electrode double-differential biochip. To ensure precise and reliable cell status assessment, we optimized both the electrode dimensions within the assay system and the buffer's conductivities. Our findings indicated that an electrode configuration of E:F:G = 2:5:1 (E, F, and G stand for exciting/floating/gap, respectively), coupled with a conductivity setting of 1.6 S/m, was optimal for probing the electrical properties of breast cancer cells (MCF-7). Utilizing this refined system, we achieved a live–dead cell differentiation accuracy of approximately 94.25%. Moreover, MCF-7 cells displayed distinct impedance signatures in response to varying drug concentrations. Changes in impedance signal characteristics, such as opacity and phase, stand for the physiological shifts within the cells under drug exposure. This research is of considerable importance, offering a novel and efficient methodology for drug dosage response testing. It paves the way for more precise and personalized cancer treatment strategies, potentially enhancing patient outcomes and quality of life.
Immunoblot, also known as western blot, is a well-established procedure in life science. It is commonly used to determine the relative size and abundance of specific proteins, as well as posttranslational modifications of proteins. While this method is widely employed due to its simplicity, it can take hours or even days to complete. Despite considerable efforts to reduce the overall procedure time, particularly for antibody incubation, the steps involving membrane rinsing have remained unchanged since the development of the immunoblot technique. In this context, we introduce an innovative device called the “Smart Wash,” designed to significantly reduce the washing intervals by utilizing a motorized salad spinner. The principle of Smart Wash is akin to that of a household washing machine: the container holds the membranes during the rinsing cycle, and the basket moves the membranes along with the washing solution in the container. We have optimized the rinsing conditions, including the volume of the washing solution, rotation speed, number of washing cycles, and direction. This straightforward device empowers researchers to significantly enhance the efficiency and productivity of immunoblotting analysis.
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