[Label-Free and Rapid Detection of Histidine-Rich Peptides in Saliva].

Siliva as a kind of biomarker containing a variety of bioactive components can be used to help disease diagnosis. Compared with the urine and blood, the collection of saliva is more simple and convenient while the collection process is completely non-invasive. Therefore, saliva detection attracts more and more attention in non-invasive disease diagnosis. Histatins are a family of small, cationic, histidine-rich peptides, which secreted by salivary bringing innate defense of the oral cavity. It has been reported that histatins are related to many other diseases, such as HIV and AIDs. Thus the detection of histatins in saliva is significantly important for oral healthy monitoring and disease diagnosis. In this paper, a new label free method for rapid detection of histidine-rich peptides was developed based on the fact that histidine-rich peptides can interact with 3-azidocoumarin through hydrogen bonds which decreases the electron-donating ability of the azido group and results in fluorescence enhancement of the system. The results showed that the fluorescence intensities were dramatically increased when histatin 5 were incubation with 3-azidocoumarin. There is a good relationship with the linear co r of 0.994 between the enhanced fluorescence and histatin 5 concentration ranging from 0.23 to 31.05 µmol·L-1, and the limit of detection is 72 nmol·L-1 (3σ/k). Moreover, the detection of histidine-rich peptides in saliva was successfully achieved by the new developed label free method since amino acids and proteins in saliva will not be interfered with the detection with the recoveries between 96.7%~111.6%. Compared with the existing saliva analysis methods, this method has the advantage of simple, fast and low cost. It might be applied in non-invasive disease diagnosis.