Layered electrophoretic transfer - A method for pre-analytic processing of histological sections

Three-dimensional histological electrophoresis enables fast automatic distinguishment of cancer margins and lymph node metastases

Tissue diagnosis is important during surgical excision of solid tumors for margin evaluation. Conventional histopathologic methods rely heavily on image-based visual diagnosis by specialized pathologists, which can be time-consuming and subjective. We report a three-dimensional (3D) histological electrophoresis system for rapid labeling and separation of the proteins within tissue sections, providing a more precise assessment of tumor-positive margin in surgically resected tissues. The 3D histological electrophoresis system uses a tumor-seeking dye labeling strategy to visualize the distribution of tumor-specific proteins within sections and a tumor finder that automatically predicts the tumor contour. We successfully demonstrated the system's capability to predict the tumor contours from five murine xenograft models and distinguish the tumor-invaded region of sentinel lymph nodes. Specifically, we used the system to accurately assess tumor-positive margins from 14 patients with cancer. Our 3D histological electrophoresis system serves as an intraoperative tissue assessment technology for more accurate and automatic pathologic diagnosis.

Photonics of Trimethine Cyanine Dyes as Probes for Biomolecules

Cyanine dyes are widely used as fluorescent probes in biophysics and medical biochemistry due to their unique photophysical and photochemical properties (their photonics). This review is focused on a subclass of the most widespread and studied cyanine dyes—trimethine cyanines, which can serve as potential probes for biomolecules. The works devoted to the study of the noncovalent interaction of trimethine cyanine dyes with biomolecules and changing the properties of these dyes upon the interaction are reviewed. In addition to the spectral-fluorescent properties, elementary photochemical properties of trimethine cyanines are considered, including: photoisomerization and back isomerization of the photoisomer, generation and decay of the triplet state, and its quenching by oxygen and other quenchers. The influence of DNA and other nucleic acids, proteins, and other biomolecules on these properties is covered. The interaction of a monomer dye molecule with a biomolecule usually leads to a fluorescence growth, damping of photoisomerization (if any), and an increase in intersystem crossing to the triplet state. Sometimes aggregation of dye molecules on biomolecules is observed. Quenching of the dye triplet state in a complex with biomolecules by molecular oxygen usually occurs with a rate constant much lower than the diffusion limit with allowance for the spin-statistical factor 1/9. The practical application of trimethine cyanines in biophysics and (medical) biochemistry is also considered. In conclusion, the prospects for further studies on the cyanine dye–biomolecule system and the development of new effective dye probes (including probes of a new type) for biomolecules are discussed.

Electrotransfer of Immunoprobes through Thin-Layer Polyacrylamide Gels

Hydrogels are important structural and operative components of microfluidic systems, finding diverse utility in biological sample preparation and interrogation. One inherent challenge for integrating hydrogels into microfluidic tools is thermodynamic molecular partitioning, which reduces the in-gel concentration of molecular solutes (e.g., biomolecular regents), as compared to the solute concentration in an applied solution. Consequently, biomolecular reagent access to in-gel scaffolded biological samples (e.g., encapsulated cells, microbial cultures, target analytes) is adversely impacted in hydrogels. Further, biomolecular reagents are typically introduced to the hydrogel via diffusion. This passive process requires long incubation periods compared to active biomolecular delivery techniques. Electrotransfer is an active technique used in Western blots and other gel-based immunoassays that overcomes limitations of size exclusion (increasing the total probe mass delivered into gel) and expedites probe delivery, even in millimeter-thick slab gels. While compatible with conventional slab gels, electrotransfer has not been adapted to thin gels (50-250 μm thick), which are of great interest as components of open microfluidic devices (vs enclosed microchannel-based devices). Mechanically delicate, thin gels are often mounted on rigid support substrates (glass, plastic) that are electrically insulating. Consequently, to adapt electrotransfer to thin-gel devices, we replace rigid insulating support substrates with novel, mechanically robust, yet electrically conductive nanoporous membranes. We describe grafting nanoporous membranes to thin-polyacrylamide-gel layers via silanization, characterize the electrical conductivity of silane-treated nanoporous membranes, and report the dependence of in-gel immunoprobe concentration on transfer duration for passive diffusion and active electrotransfer. Alternative microdevice component layers─including the mechanically robust, electrically conductive nanoporous membranes reported here─provide new functionality for integration into an increasing array of open microfluidic systems.

3D projection electrophoresis for single-cell immunoblotting

Immunoassays and mass spectrometry are powerful single-cell protein analysis tools; however, interfacing and throughput bottlenecks remain. Here, we introduce three-dimensional single-cell immunoblots to detect both cytosolic and nuclear proteins. The 3D microfluidic device is a photoactive polyacrylamide gel with a microwell array-patterned face (xy) for cell isolation and lysis. Single-cell lysate in each microwell is "electrophoretically projected" into the 3rd dimension (z-axis), separated by size, and photo-captured in the gel for immunoprobing and confocal/light-sheet imaging. Design and analysis are informed by the physics of 3D diffusion. Electrophoresis throughput is > 2.5 cells/s (70× faster than published serial sampling), with 25 immunoblots/mm2 device area (>10× increase over previous immunoblots). The 3D microdevice design synchronizes analyses of hundreds of cells, compared to status quo serial analyses that impart hours-long delay between the first and last cells. Here, we introduce projection electrophoresis to augment the heavily genomic and transcriptomic single-cell atlases with protein-level profiling.