Simple and Efficient Method to Purify DNA–Protein Conjugates and Its Sensing Applications

DNA-protein conjugates are very useful in analytical chemistry for target recognition and signal amplification. While a number of methods for conjugating DNA with proteins are known, methods for purification of DNA-protein conjugates from reaction mixture containing unreacted proteins are much less investigated. In this work, a simple and efficient approach to purify DNA-invertase conjugates from reaction mixture via a biotin displacement strategy to release desthiobiotinylated DNA-invertase conjugates from streptavidin-coated magnetic beads was developed. The conjugates purified by this approach were utilized for quantitative detection of cocaine and DNA using a personal glucose meter through structure-switching DNA aptamer sensors and competitive DNA hybridization assays, respectively. In both cases, the purified DNA-invertase conjugates showed better performance compared to the same assays using unpurified conjugates. The approach demonstrated here can be further expanded to other DNA and proteins to generate purified DNA-protein conjugates for analytical and other applications.