Rapid calcification propensity testing in blood using a temperature controlled microfluidic polymer chip

PLoS ONE, vol. 15, pp. e0230493

Abstract

Phosphate toxicity is a major threat to cardiovascular health in chronic kidney disease. It is associated with oxidative stress, inflammation and the accumulation of calcium phosphate commonly known as calcification in soft tissues leading to functional disorders of blood vessels. An improved calcification propensity test for the assessment of phosphate toxicity was developed, which measures the velocity of calcium phosphate mineralization from colloidal precursors in vitro. This so called T50 test measures the transformation from a primary into a secondary form of nanosized colloidal plasma protein-calcium phosphate particles known as calciprotein particles. The T50 test in its previous form required a temperature controlled nephelometer and several hours of continuous measurement, which precluded rapid bed side testing. We miniaturized the test using microfluidic polymer chips produced by ultrasonic hot embossing. A cartridge holder contained a laser diode for illumination, light dependent resistor for detection and a Peltier element for thermo control. Increasing the assay temperature from 37°C to 75°C reduced the T50 test time 36-fold from 381 ± 10 min at 37°C to 10.5 ± 0.3 min at 75°C. Incorporating sputtered micro mirrors into the chip design increased the effective light path length, and improved signal-to-noise ratio 9-fold. The speed and reproducibility of the T50 chip-based assay run at 75°C suggest that it may be suitable for rapid measurements, preferably in-line in a dialyser or in a portable microfluidic analytic device with the chip inserted as a disposable cartridge.

Authors 6

1. Julia Bavendiek Aachen KEmikro

   RWTH Aachen University

   Affiliation as printed

   KEmikro, RWTH Aachen University, Aachen, Germany

2. Philipp Maurer Aachen KEmikro

   RWTH Aachen University

   Affiliation as printed

   KEmikro, RWTH Aachen University, Aachen, Germany

3. Steffen Gräber Aachen Biointerface Laboratory

   Universitätsklinikum Aachen · RWTH Aachen University

   Affiliation as printed

   Biointerface Laboratory, Helmholtz-Institute for Biomedical Engineering, RWTH Aachen University Clinics, Aachen, Germany

4. Andreas Pasch

   Johannes Kepler University of Linz · Lindenhofspital

   Affiliation as printed

   Calciscon AG, Nidau; Lindenhofspital, Bern, Switzerland; Institute for Physiology and Pathopysiology, Johannes Kepler University, Linz, Austria

   Calciscon AG, Nidau

   Institute for Physiology and Pathopysiology, Johannes Kepler University, Linz, Austria

   Lindenhofspital, Bern, Switzerland

5. Werner Karl Schomburg Aachen KEmikro

   RWTH Aachen University

   Affiliation as printed

   KEmikro, RWTH Aachen University, Aachen, Germany

6. Willi Jahnen‐Dechent corresponding Aachen Biointerface Laboratory

   Universitätsklinikum Aachen · RWTH Aachen University

   Affiliation as printed

   Biointerface Laboratory, Helmholtz-Institute for Biomedical Engineering, RWTH Aachen University Clinics, Aachen, Germany