A portable impedance microflow cytometer for measuring cellular response to hypoxia

Abstract

This article presents the development and testing of a low‐cost (<$60), portable, electrical impedance‐based microflow cytometer for single‐cell analysis under a controlled oxygen microenvironment. The system is based on an AD5933 impedance analyzer chip, a microfluidic chip, and an Arduino microcontroller operated by a custom Android application. A representative case study on human red blood cells (RBCs) affected by sickle cell disease is conducted to demonstrate the capability of the cytometry system. Impedance values of sickle blood samples exhibit remarkable deviations from the common reference line obtained from two normal blood samples. Such deviation is quantified by a conformity score, which allows for the measurement of intrapatient and interpatient variations of sickle cell disease. A low conformity score under oxygenated conditions or drastically different conformity scores between oxygenated and deoxygenated conditions can be used to differentiate a sickle blood sample from normal. Furthermore, an equivalent circuit model of a suspended biological cell is used to interpret the electrical impedance of single flowing RBCs. In response to hypoxia treatment, all samples, regardless of disease state, exhibit significant changes in at least one single‐cell electrical property, that is, cytoplasmic resistance and membrane capacitance. The overall response to hypoxia is less in normal cells than those affected by sickle cell disease, where the change in membrane capacitance varies from −23% to seven times as compared with −17% in normal cells. The results reported in this article suggest that the developed method of testing demonstrates the potential application for a low‐cost screening technique for sickle cell disease and other diseases in the field and low‐resource settings. The developed system and methodology can be extended to analyze cellular response to hypoxia in other cell types.

Digital Sort-Enabled Counting Allows Absolute Electrical Quantification of Target Nucleic Acid

“…19,20 Low-cost (<$60) integrated circuits (e.g., AD5933 impedance analyzer) and microcontrollers can be used for impedance cytometry. 21 The portability of electrical detection has also been demonstrated via a modular Coulter counter the size of a credit card. 22 Future integration of droplet generation, LAMP incubation, and droplet sorting in a single chip 13,23 will further streamline the workflow and minimize operator error, cross-contamination, and potential losses due to handling and evaporation.…”

“…Although we have yet to show an actual point-of-care implementation of DISCO, relevant technologies to enable it are available. For example, the generation of monodispersed droplets for LAMP reaction can be implemented through portable chip-based or chip-free solutions. , Low-cost (<$60) integrated circuits (e.g., AD5933 impedance analyzer) and microcontrollers can be used for impedance cytometry . The portability of electrical detection has also been demonstrated via a modular Coulter counter the size of a credit card .…”

Next generation microfluidics: fulfilling the promise of lab-on-a-chip technologies

“…[51][52][53] Coupling the electrical field with fluidics could enable POC testing and may improve the throughput and specificity of the impedance flow cytometry. 54 Researchers can also design low-cost MF devices with minimal or no supporting equipment and accessories in resource-limited settings. 26 Opportunities exist for MF applications in rapid diagnostic tools that can be used on-site, such as drawing blood from a finger stick.…”

3D-Printed Hydrodynamic Focusing Lab-on-a-Chip Device for Impedance Flow Particle Analysis

“…To enable measuring electrochemical signals in the 3D-printed device, two conductive metal rods were inserted into the designated sockets and were sealed using epoxy glue. The cost for fabricating one chip costs USD 12, which is lower compared with the commercially available chips [26] and the already existing technologies [15,27].…”