Protein Discrimination Using a Colorimetric Sensor Array Based on Gold Nanoparticle Aggregation Induced by Cationic Polymer

In view of the charge characteristic of cationic polymers, herein, we put forward a sensitive and unique colorimetric sensor array strategy for discrimination of proteins. We used gold nanoparticles (AuNPs) as colorimetric probes and three nonspecific DNA strands (15A, 15C, and 15T) as nonspecific receptors. Upon the addition of the proteins, the diverse interactions between DNA and proteins result in the difference in the number of the remaining DNA strands. As we know, cationic polymer, such as poly(diallyldimethylammonium chloride) (PDDA), can interact with DNA and AuNPs with negative charges. Therefore, these remaining DNA strands can interact with PDDA. Superfluous PDDA molecules bind to AuNPs, leading to different AuNP aggregation. On the basis of this phenomenon, linear discriminant analysis (LDA) is employed to quantitatively discriminate the colorimetric responses (A(620)/A(520)) of proteins. At the 20 nM level, 11 proteins were completely distinguished with 100% accuracy. Remarkably, the feasibility of the method was confirmed by the discrimination of proteins in serum.