Frontiers in single cell analysis: multimodal technologies and their clinical perspectives.

Single cell multimodal analysis is at the frontier of single cell research: it defines the roles and functions of distinct cell types through simultaneous analysis to provide unprecedented insight into cellular processes. Current single cell approaches are rapidly moving toward multimodal characterizations. It replaces one-dimensional single cell analysis, for example by allowing for simultaneous measurement of transcription and post-transcriptional regulation, epigenetic modifications and/or surface protein expression. By providing deeper insights into single cell processes, multimodal single cell analyses paves the way to new understandings in various cellular processes such as cell fate decisions, physiological heterogeneity or genotype-phenotype linkages. At the forefront of this, microfluidics is key for high-throughput single cell analysis. Here, we present an overview of the recent multimodal microfluidic platforms having a potential in biomedical research, with a specific focus on their potential clinical applications.

Directed Evolution in Drops: Molecular Aspects and Applications.

The process of optimizing the properties of biological molecules is paramount for many industrial and medical applications. Directed evolution is a powerful technique for modifying and improving biomolecules such as proteins or nucleic acids (DNA or RNA). Mimicking the mechanism of natural evolution, one can enhance a desired property by applying a suitable selection pressure and sorting improved variants. Droplet-based microfluidic systems offer a high-throughput solution to this approach by helping to overcome the limiting screening steps and allowing the analysis of variants within increasingly complex libraries. Here, we review cases where successful evolution of biomolecules was achieved using droplet-based microfluidics, focusing on the molecular processes involved and the incorporation of microfluidics to the workflow. We highlight the advantages and limitations of these microfluidic systems compared to low-throughput methods and show how the integration of these systems into directed evolution workflows can open new avenues to discover or improve biomolecules according to user-defined conditions.

Gradient acoustic focusing of sub-micron particles for separation of bacteria from blood lysate.

Handling of submicron-sized objects is important in many biochemical and biomedical applications, but few methods today can precisely manipulate this range of particles. We present gradient acoustic focusing that enables flow-through particle separation of submicron particles and cells and we apply it for separation of bacteria from blood lysate to facilitate their detection in whole blood for improved diagnostics. To control suspended objects below the classical 2µm size limit for acoustic focusing, we introduce a co-flowing acoustic impedance gradient to generate a stabilizing acoustic volume force that supresses acoustic streaming. The method is validated theoretically and experimentally using polystyrene particles, Staphylococcus aureus, Streptococcus pneumoniae and Escherichia coli. The applicability of the method is demonstrated by the separation of bacteria from selectively chemically lysed blood. Combined with downstream operations, this new approach opens up for novel methods for sepsis diagnostics.