Protein–gold nanoparticles interactions and its application for alkaline phosphatase assay

Proteins-modified gold nanoparticles (AuNPs) have been considered as attractive materials in many fields especially in biosensing. In this Letter, the authors have studied the relationship between ratios of specific amino acids and protein–AuNPs interactions. A new indicator Rw/s, calculated from the ratios of certain hydrophilic amino acids, is proposed to reveal the affinity coefficient between proteins and AuNPs. Experimental results show that the proposed Rw/s can indicate the binding status of proteins and AuNPs effectively. The authors have also introduced alkaline phosphatase, a protein with relatively low Rw/s, for detection by the colorimetric shift based on strong protein–AuNPs interactions.