Microfluidic device integrating single-cell extraction and electrical lysis for mass spectrometry detection of intracellular compounds.

Analysis of cellular composition and metabolism at a single-cell resolution allows gaining more information about complex relationships of cells within tissues or whole living organisms by resolving the variance stemming from the cellular heterogeneity. Mass spectrometry (MS) is a perfect analytical tool satisfying the demanding requirements of detecting and identifying compounds present in such ultralow-volume samples of high chemical complexity. However, the method of sampling and sample ionization is crucial in obtaining relevant information. In this work, we present a microfluidic sampling platform that integrates single-cell extraction from MS-incompatible media with electrical cell lysis and nanoESI-MS analysis of human erythrocytes. Hemoglobin alpha and beta chains (300 amol/cell) were successfully identified in mass spectra of single-erythrocyte lysates.

Photon-upconversion barcode for monitoring an enzymatic reaction with a fluorescence reporter in droplet microfluidics.

We report luminescent photon-upconversion barcodes for indexing the chemical content of droplets. The barcode is compatible with the simultaneous detection of fluorescence. The encoding and decoding of the initial concentration of enzyme ß-galactosidase and substrate 4-methylumbelliferyl ß-d-galactopyranoside are described. The fluorescent product 4-methylumbelliferone is detected simultaneously with the barcode.

Resistive pulse sensing as particle counting and sizing method in microfluidic systems: Designs and applications review.

Resistive pulse sensing is a well-known and established method for counting and sizing particles in ionic solutions. Throughout its development the technique has been expanded from detection of biological cells to counting nanoparticles and viruses, and even registering individual molecules, e.g., nucleotides in nucleic acids. This technique combined with microfluidic or nanofluidic systems shows great potential for various bioanalytical applications, which were hardly possible before microfabrication gained the present broad adoption. In this review, we provide a comprehensive overview of microfluidic designs along with electrode arrangements with emphasis on applications focusing on bioanalysis and analysis of single cells that were reported within the past five years.