Detection of pathogenic bacteria by magneto-immunoassays:a review

Magnetic particle-based immunoassays are widely used in microbiology-related assays for both microbial capture,separation,analysis,and detection.Besides facilitating sample operation,the implementation of micro-to-nanometer scale magnetic beads as a solid support potentially shortens the incubation time(for magnetic immuno capture)from several hours to less than an hour.Analytical technologies based on magnetic beads offer a rapid,effective and inexpensive way to separate and concentrate the target analytes prior to detection.Magneto-immuno separation uses magnetic particles coated with specific antibodies to capture target microorganisms,bear the corresponding antigens,and subsequently separate them from the sample matrix in a magnetic field.The method has been proven effective in separating various types of pathogenic bacteria from environmental water samples and in eliminating background interferences.Magnetic particles are often used to capture target cells(pathogenic bacteria)from samples.In most commercially available assays,the actual identification and quantitation of the captured cells is then performed by classical microbiological assays.This review highlights the most sensitive analytic methods(i.e.,long-range surface plasmon resonance and electrochemical impedance spectroscopy)to detect magnetically tagged bacteria in conjunction with magnetic actuation.

A short review on cell-based biosensing:challenges and breakthroughs in biomedical analysis

Current cell-based biosensors have progressed substantially from mere alternatives to molecular bioreceptors into enabling tools for interfacing molecular machineries and gene circuits with microelectronics and for developing groundbreaking sensing and theragnostic platforms.The recent literature concerning whole-cell biosensors is reviewed with an emphasis on mammalian cells,and the challenges and breakthroughs brought along in biomedical analyses through novel biosensing concepts and the synthetic biology toolbox.These recent innovations allow development of cell-based biosensing platforms having tailored performances and capable to reach the levels of sensitivity,dynamic range,and stability suitable for high analytic/medical relevance.They also pave the way for the construction of flexible biosensing platforms with utility across biological research and clinical applications.The work is intended to stimulate interest in generation of cell-based biosensors and improve their acceptance and exploitation.

High-resolution impedance mapping using electrically activated quantitative phase imaging

Retrieving electrical impedance maps at the nanoscale rapidly via nondestructive inspection with a high signal-to-noise ratio is an unmet need,likely to impact various applications from biomedicine to energy conversion.In this study,we develop a multimodal functional imaging instrument that is characterized by the dual capability of impedance mapping and phase quantitation,high spatial resolution,and low temporal noise.To achieve this,we advance a quantitative phase imaging system,referred to as epi-magnified image spatial spectrum microscopy combined with electrical actuation,to provide complementary maps of the optical path and electrical impedance.We demonstrate our system with high-resolution maps of optical path differences and electrical impedance variations that can distinguish nanosized,semi-transparent,structured coatings involving two materials with relatively similar electrical properties.We map heterogeneous interfaces corresponding to an indium tin oxide layer exposed by holes with diameters as small as~550 nm in a titanium(dioxide)over-layer deposited on a glass support.We show that electrical modulation during the phase imaging of a macro-electrode is decisive for retrieving electrical impedance distributions with submicron spatial resolution-and beyond the limitations of electrode-based technologies(surface or scanning technologies).The findings,which are substantiated by a theoretical model that fits the experimental data very well enable achieving electro-optical maps with high spatial and temporal resolutions.The virtues and limitations of the novel optoelectrochemical method that provides grounds for a wider range of electrically modulated optical methods for measuring the electric field locally are critically discussed.