Cellular heterogeneity of any tissue or organ makes it challenging to identify and study the impact and the treatment of any disease. In this context, analysis of cells at an individual level becomes highly relevant for throwing light on the heterogeneous nature of cells. Single cell analysis can be used to gain insights into an overall view of any disease, thereby holding great applications in health diagnosis, disease identification, drug screening, and targeted delivery. Various conventional methods, such as flow cytometry, are used to isolate and study single cells. Still, these methods are narrower in scope due to certain limitations, including the associated processing/run times, the economy of reagents, and sample preparation. Microfluidics, an emerging technology, overcomes such limitations and is now being widely applied to develop tools for the isolation, analysis, and parallel manipulation of single cells. This review systematically compiles various microfluidic tools and techniques involved in single cell investigation. The review begins by highlighting the applications of microfluidics in single cell sorting and manipulation, followed by emphasizing microfluidic platforms for single cell analysis, with a specific focus on optical sensing-based detection in a high-throughput fashion, and ends with applications in cancer cell studies.

This article reports a simple and inexpensive leak-proof paper pad with an initial selection of a paper substrate on the grounds of surface morphology and fluid absorption time. Herein, a drying method is used for glucose detection on a paper pad through colorimetric analysis, and the spot detection of glucose is analyzed by optimizing the HRP concentration and volume to obtain accurate results. The rapid colorimetric method for the detection of glucose on the paper pad was developed with a limit of detection (LOD) of 2.92 mmol L−1. Furthermore, the effects of the detection conditions were investigated and discussed comprehensively with the help of chemometric methods. Paper pads were developed for glucose detection with a range of 0.5–20 mM (apropos to the normal glucose level in the human body) and 0.1–0.5 M (to test the excessive intake of glucose). The developed concept has huge potential in the healthcare sector, and its extension could be envisioned to develop the reported paper pad as a point-of-care testing device for the initial screening of a variety of diseases.

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