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The study utilized thermophoresis, the directed motion of molecules in a temperature gradient to quantify DNA and
proteins for point-of-care applications. Because the direction and speed of thermophoretic motion is dependent on the size,
charge, and conformation of the molecules, the binding between molecules can induce changes in their thermophoretic
motion. To quantify biomolecules using thermophoresis, we mixed fluorescently-labeled capture probes with samples and
then used an infrared laser to create a temperature gradient in the solution. By adding a small fraction of polymers to the
buffer solution, we accumulated the fluorescent probes in a temperature gradient using the thermophoretic effects. The
thermophoretic motion of the fluorescent probes significantly changed as the target molecules bind to the specially
designed capture probes. Consequently, the level of the thermophoretic accumulation, which was determined by the spatial
distribution of fluorescent probes, could be used to quantify molecules. This method functioned well even when the buffer
contained 10% serum, which suggested that the detection was resistant to the interferences from the molecules in serum.
The thermophoresis-based detection method developed in this study only requires a laser and an epi-fluorescence
microscope during the detection. Unlike many other commonly seen biosensing methods, quantifying molecules using
thermophoresis does not need any fluid channels or pumps for washing away unbound molecules during the detection
process. In addition, the detection does not rely on any micro- or nanofabricated chips. In short, this thermophoresis-based
biosensing method can be a simple, robust, and sensitive method for quantifying proteins and DNA.
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