Microsystems for Single-Cell Analysis

Sonja M. Weiz, Mariana Medina-Sánchez, Oliver G. Schmidt

Due to the heterogeneity that exists even between cells of the same tissue, it is essential to use techniques and devices able to resolve the characteristics of single biological cells, such as morphology, metabolism, or response to drugs. To that end, different structures with sizes similar to that of individual cells have been developed in recent years, which allow single-cell studies with high sensitivity and high resolution. By employing a variety of sensing strategies, one can obtain complementary information about individual cells, and thus create a complete picture of cellular properties. This review aims to provide an overview of microscale single-cell sensors. The progress in micrometer-sized sensing probes as well as microfluidic and micropatterned devices is described, showing the capabilities of the available systems. In addition, a comprehensive compendium of systems based on rolled-up microtubes, which have the potential to advance and improve the single-cell analysis microsystem field, is comprised.

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Targeting Tumor-Associated Exosomes with Integrin-Binding Peptides

Randy P. Carney, Sidhartha Hazari, Tatu Rojalin, Alisha Knudson, Tingjuan Gao, Yuchen Tang, Ruiwu Liu, Tapani Viitala, Marjo Yliperttula, Kit S. Lam

All cells expel a variety of nanosized extracellular vesicles (EVs), including exosomes, with composition reflecting the cells' biological state. Cancer pathology is dramatically mediated by EV trafficking via key proteins, lipids, metabolites, and microRNAs. Recent proteomics evidence suggests that tumor-associated exosomes exhibit distinct expression of certain membrane proteins, rendering those proteins as attractive targets for diagnostic or therapeutic application, yet it is not currently feasible to distinguish circulating EVs in complex biofluids according to their tissue of origin or state of disease. Here, peptide binding to tumor-associated EVs via overexpressed membrane protein is demonstrated. It is found that SKOV-3 ovarian tumor cells and their released EVs express α3β1 integrin, which can be targeted by the in-house cyclic nonapeptide, LXY30. After measuring bulk SKOV-3 EV association with LXY30 by flow cytometry, Raman spectral analysis of laser-trapped single exosomes with LXY30-dialkyne conjugate enables the differentiation of cancer-associated exosomes from noncancer exosomes. Furthermore, the foundation for a highly specific detection platform for tumor-EVs in solution with biosensor surface-immobilized LXY30 is introduced. LXY30 not only exhibits high specificity and affinity to α3β1 integrin-expressing EVs, but also reduces EV uptake into SKOV-3 parent cells, demonstrating the possibility for therapeutic application.

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