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Abstract Efficient techniques for separating target cells from undiluted blood are necessary for various diagnostic and research applications. This paper presents acoustic focusing in dense media containing iodixanol to purify peripheral blood mononuclear cells (PBMCs) from whole blood in a label-free and flow-through format. If the blood is laminated or mixed with iodixanol solutions while passing through the resonant microchannel, all the components (fluids and cells) rearrange according to their acoustic impedances. Red blood cells (RBCs) have higher effective acoustic impedance than PBMCs. Therefore, they relocate to the pressure node despite the dense medium, while PBMCs stay near the channel walls due to their negative contrast factor relative to their surrounding medium. By modifying the medium and thus tuning the contrast factor of the cells, we enriched PBMCs relative to RBCs by a factor of 3600 to 11,000 and with a separation efficiency of 85%. That level of RBC depletion is higher than most other microfluidic methods and similar to that of density gradient centrifugation. The current acoustophoretic chip runs up to 20 µl/min undiluted whole blood and can be integrated with downstream analysis.

Summary: Understanding microbes in nature requires consideration of their microenvironment. Here, we present a protocol for quantifying biomass and nutrient degradation of bacterial and fungal cultures (Pseudomonas putida and Coprinopsis cinerea, respectively) in microfluidics. We describe steps for mask design and fabrication, master printing, polydimethylsiloxane chip fabrication, and chip inoculation and imaging using fluorescence microscopy. We include procedures for image analysis, plotting, and statistics.For complete details on the use and execution of this protocol, please refer to Arellano-Caicedo et al. (2023).1 : Publisher’s note: Undertaking any experimental protocol requires adherence to local institutional guidelines for laboratory safety and ethics.

Arellano Caicedo et al. use microfluidic devices to determine how spatial distortion of pore spaces in soil organic matter affects bacterial and fungal growth and substrate degradation. Their newly conceptualized chip design allows the quantification of bacterial and fungal biomass, and ecosystem function organic matter cycling with help of fluorescent markers in different microstructures.

Mafla-Endara et al. incubate a microfluidic chip with and directly in soil in order to examine interactions between microbial communities and the pore space microstructures. This work shows the spatiotemporal changes of soil microhabitats and demonstrates that fungal hyphae increase the dispersal range and abundance of water-dwelling organisms across air pockets.