Abstract
Calorimetric biochemical measurements offer various advantages such as low waste, low cost, low sample consumption, short operating time, and labor-savings. Multichannel calorimeters can enhance the possibility of performing higher-throughput biochemical measurements. An enthalpy sensor (ES) array is a key device in multichannel calorimeters. Most ES arrays use Wheatstone bridge amplifiers to condition the sensor signals, but such an approach is only suitable for null detection and low resistance sensors. To overcome these limitations, we have developed a multichannel calorimetric simultaneous assay (MCSA) platform. An adjustable microampere constant-current (AMCC) source was designed for exciting the ES array using a microampere current loop measurement circuit topology. The MCSA platform comprises a measurement unit, which contains a multichannel calorimeter and an automatic simultaneous injector, and a signal processing unit, which contains multiple ES signal conditioners and a data processor. This study focused on the construction of the MCSA platform; in particular, construction of the measurement circuit and calorimeter array in a single block. The performance of the platform, including current stability, temperature sensitivity and heat sensitivity, was evaluated. The sensor response time and calorimeter constants were given. The capability of the platform to detect relative enzyme activity was also demonstrated. The experimental results show that the proposed MCSA is a flexible and powerful biochemical measurement device with higher throughput than existing alternatives.
Highlights
Catalase is a common enzyme present in most living organisms exposed to oxygen, and it is a crucial enzyme in protecting cells from oxidative damage engendered by reactive oxygen species
We demonstrated the performance of the proposed multichannel calorimetric simultaneous assay (MCSA) platform by observing one exothermic enzyme reaction and measuring its relative activity
The temperature resolution of the presented MCSA platform was up to ±10 μK, which is improvement on the device calibration error between 20 and 30 C = −20 μK ± 10 μK), which is improvement on the device reported in our previous work, which had a resolution of ±1000 μK
Summary
Catalase is a common enzyme present in most living organisms exposed to oxygen, and it is a crucial enzyme in protecting cells from oxidative damage engendered by reactive oxygen species. Catalase activity has been demonstrated to be involved in the development of human type 2 diabetes [1,2]. Erythrocyte catalase is the principal regulator of hydrogen peroxide metabolism; any inherited or acquired deficiencies in erythrocyte catalase may cause the hydrogen peroxide concentration in the body to increase, which can have both toxic and physiological effects. Blood catalase activity is generally measured using a clinical spectrophotometric assay. The activity assay of this enzyme and other enzymes is usually challenging and time-consuming to quantify using chemical analysis [3,4]
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