Biophysical phenotyping of single-cell based on impedance and application for individualized precision medicine.

Single-cell biophysical characterization based on impedance measurement is an advantageous approach due to its label-free, high-efficiency, cost-effective and real-time capability. Biophysical phenotyping can yield timely and rich information on physiological and pathological state of cells for disease diagnosis, drug screening, precision medicine, etc. However, precise measurement on single-cell impedance is challenging, particularly hard to figure out the detailed biophysical parameters of single cell due to coupling and complexity of impedance model. Here, we propose an analytic determination method to decode single-cell electrophysiological parameters (including cell-substrate interface capacitance, cell membrane capacitance, cell membrane conductivity, and cytoplasm conductivity) from the impedances measured at optimized frequencies by using analytic solution rather than spectrum fitting. With this simple and fast analytic solution method, the physiological parameters of single cell in natural adhesion state can be accurately determined in real time. We validate this cell parameter determination method in monitoring the change of cell adhesion under hydraulic effects and exploring electrophysiological differences among MCF-7, HeLa, Huh7, and MDA-MB-231 cell lines. Particularly, we apply the approach to optimize tumor treating fields (TTFields) therapy, realizing individualized precision medicine. Our work provides an accurate and efficient approach for characterizing single-cell biophysical properties with real-time, in-situ, label-free, and less invasive advantages.

Electroporation-Assisted Surface-Enhanced Raman Detection for Long-Term, Label-Free, and Noninvasive Molecular Profiling of Live Single Cells.

Molecule characterization of live single cells is greatly important in disease diagnoses and personalized treatments. Conventional molecule detection methods, such as mass spectrography, gene sequencing, or immunofluorescence, are usually destructive or labeled and unable to monitor the dynamic change of live cellular molecules. Herein, we propose an electroporation-assisted surface-enhanced Raman scattering (EP-SERS) method using a microchip to implement label-free, noninvasive, and continuous detections of the molecules of live single cells. The microchip containing microelectrodes with nanostructured EP-SERS probes has a multifunction of cell positioning, electroporation, and SERS detection. The EP-SERS method capably detects both the intracellular and extracellular molecules of live single cells without losing cell viability so as to enable long-term monitoring of the molecular pathological process in situ. We detect the molecules of single cells for two breast cancer cell lines with different malignancies (MCF-7 and MDA-MB-231), one liver cancer cell line (Huh-7), and one normal cell line (293T) using the EP-SERS method and classify these cell types to achieve high accuracies of 91.4-98.3% using their SERS spectra. Furthermore, 24 h continuous monitoring of the heterogeneous molecular responses of different cancer cell lines under doxorubicin treatment is successfully implemented using the EP-SERS method. This work provides a long-term, label-free, and biocompatible approach to simultaneously detect intracellular and extracellular molecules of live single cells on a chip, which would facilitate research and applications of cancer diagnoses and personalized treatments.

Computer-Vision-Based Dielectrophoresis Mobility Tracking for Characterization of Single-Cell Biophysical Properties.

Fast and precise measurements of live single-cell biophysical properties is significant in disease diagnosis, cytopathologic analysis, etc. Existing methods still suffer from unsatisfied measurement accuracy and low efficiency. We propose a computer vision method to track cell dielectrophoretic movements on a microchip, enabling efficient and accurate measurement of biophysical parameters of live single cells, including cell radius, cytoplasm conductivity, and cell-specific membrane capacitance, and in situ extraction of cell texture features. We propose a prediction-iteration method to optimize the cell parameter measurement, achieving high accuracy (less than 0.79% error) and high efficiency (less than 30 s). We further propose a hierarchical classifier based on a support vector machine and implement cell classification using acquired cell physical parameters and texture features, achieving high classification accuracies for identifying cell lines from different tissues, tumor and normal cells, different tumor cells, different leukemia cells, and tumor cells with different malignancies. The method is label-free and biocompatible, allowing further live cell studies on a chip, e.g., cell therapy, cell differentiation, etc.

AC/DC Electric-Field-Assisted Growth of ZnO Nanowires for Gas Discharge.

Using ZnO nanowires as needle anodes in gas discharge is helpful for maintaining continuous discharge with a relatively low voltage. It is necessary that the ZnO nanowires are far enough apart to guarantee no electric field weakening and that the nanowire anodes are easy to assemble together with the discharging devices. An AC/DC electric-field-assisted wet chemical method is proposed in this paper. It was used to grow ZnO nanowires directly on discharging devices. The nanowires covered the whole electrode in the case in which only a DC field was applied. Moreover, the tips of the nanowires were scattered, similar to the results observed under the application of AC fields. The average distance between the tips of the highest nanowires was approximately equal to 4 µm, which almost meets the requirement of gas discharge. The research concerning growing ZnO nanowires directly on PCBs shown that, at the current time, ZnO nanowires on PCBs did not meet the requirements of gas discharge; however, in this study, the parameters regarding ZnO nanowire growth were established.

A CuNi Alloy-Carbon Layer Core-Shell Catalyst for Highly Efficient Conversion of Aqueous Formaldehyde to Hydrogen at Room Temperature.

A copper (Cu) material is catalytically active for formaldehyde (HCHO) dehydrogenation to produce H2, but the unsatisfactory efficiency and easy corrosion hinder its practical application. Alloying with other metals and coating a carbon layer outside are recognized as effective strategies to improve the catalytic activity and the long-term durability of nonprecious metal catalysts. Here, highly dispersed CuNi alloy-carbon layer core-shell nanoparticles (CuNi@C) have been developed as a robust catalyst for efficient H2 generation from HCHO aqueous solution at room temperature. Under the optimized reaction conditions, the CuNi@C catalyst exhibits a H2 evolution rate of 110.98 mmol·h-1·g-1, which is 1.5 and 4.9 times higher than those of Cu@C and Ni@C, respectively, which ranks top among the reported nonprecious metal catalysts for catalytic HCHO reforming at room temperature to date. Furthermore, CuNi@C also displays excellent stability toward the catalytic HCHO reforming into H2 in tap water owing to the well-constructed carbon sheath protecting CuNi nanocrystals from oxidation in an alkaline medium. Combined with density functional theory calculations, the superior catalytic efficiency of CuNi@C for H2 generation results from the synergistic contribution between the massive active species from HCHO decomposition on the Cu sites and the remarkable H2 evolution activity on Ni sites. The improved performance of CuNi@C highlights the enormous potential of advancing noble-metal-free nanoalloys as cost-effective and recyclable catalysts for energy recovery from industrial HCHO wastewater.

[Immunonanogold catalytic spectrophotometric determination of trace IgG].

Gold nanoparticles the size of about 10 nm were prepared by improved trisodium citrate reduction procedure, and were used to label goat anti-human IgG to obtain a sensitive spectral probe for IgG in the condition of pH 6.5. The immune reaction of nanogold-labeled IgG antibody (anti-IgG) with the antigen IgG took place to form the nanogold immune complex in pH 7.O Na2HPO4-C6H8O7 buffer solution and in the presence of polyethylene (PEG). The optimal immunoreaction conditions were pH 7.0, 10.76 microg x mL(-1) nanogold-labeled anti-IgG, 8.0% PEG 6000 and incubation time of 30 min under the ultrasonic irradiation. After centrifuging for 15 min at 16000 rpm, the excess nanogold-labeled anti-IgG in the upper solutions was obtained, and was used to catalyze the colored particle reaction of HAuCl4 with NH2 OH x HCl to produce gold particles with bigger size. The influence of pH value, HAuCl4 and NH2OH x HCl concentration, and reaction temperature and time on the immunonanogold catalytic reaction was considered spectrophotometrically. A pH 2.27 Na3C6H5O7-HCl buffer solution, 0.094 mmol x L HAuCl4, 1.92 mmol x L NH22OH x HCl, and reaction time of 6 min at 30 degrees C water bath were chosen for use. Results demonstrated that with increasing IgG, the concentration of gold labeled anti-IgG in the upper solution decreased, and the absorbance decreased linearly. Linear relationships between the decreased absorbance at 700 nm and the IgG concentration CIgG in the range of 0.10-10 ng x mL(-1) were obtained. Its regress equation was deltaA(760 nm) = 0.0144c(IgG) + 0.0042, the related coefficient was 0.9926, and the detection limit reached 0.06 ng x mL(-1) IgG. The influence of foreign substances on the determination of 3 ng x mL(-1) IgG was examined, with the relative error +/-10%. Results showed that the following coexistent substances had no impact on the assay: 6000 ng x mL(-1) HSA, 6000 ng x mL(-1) gluocose, 6000 ng x ml(-1) Zn(II), 3000 ng x mL(-1) IgA, 3000 ng x mL(-1) Ca(II), 3000 ng x mL(-1) L-arginine, 3000 ng x mL(-1) beta-phenylalanine, 2400 ng x mL(-1) Cu(II), 2400 ng x mL(-1) EDTA, 2400 ng x mL(-1) L-cystinol etc. This showed that the assay has high selectivity. The sensitive, rapid and highly specific assay was applied to the quantification of IgG in human sera, with satisfactory results.