Protein Determination by Distance and Color Changing via PEG-Based Hydrogels

Equipment-free detection devices are attractive for point-of-care analysis, especially in resource-limited regions. Distance -based detection is the measurement of color change along the detection path related to the concentration of analytes. Hydrogels are three-dimensional crosslinked polymer networks with tunable properties and may be suitable for distance-based sensors. However, only small ions have been used as the targets in the previous studies. In this work, we demonstrated the possibility of using hydrogel as the distance-based measurement of large biomolecules such as proteins. The hydrogel was prepared with poly(ethylene glycol) diacrylate and a fluorescein derivative as the fluorescent detection probe. The fluorescent alteration in the presence of a target protein, trypsin, can be observed in both intensity-based and distance-based detection. It was found that the effect of the concentration of a fluorescent reagent was not significantly impacted in distance-based detection, while it is essential in intensity-based detection. The relationship between the distance change and the trypsin concentration in the range of 0.5 - 5 mM can be observed. This result showed the possibility of using hydrogel for distance-based detection of large biomolecules.