Purpald reagent to enhance surface plasmon resonance imaging toward sensing of formaldehyde
Abstract
Formaldehyde (FA) is the smallest aldehyde with the formula HCHO. An elevated FA concentration (despite at ppm-ppb levels) in the human body reflects abnormal health conditions. Moreover, HCHO is an environmental pollutant. Detecting the ultra-low ppb concentrations of FA is challenging due to the small size of this molecule in comparison to large biomolecule markers (e.g., DNA, protein, antibody). Herein, we demonstrate an ultra-sensitive HCHO detection strategy by utilizing Surface Plasmon Resonance imaging (SPRi) and the Purpald reagent (4-amino-3-hydrazino-5-mercapto-1,2,4-triazole) to complex with HCHO. The Purpald reagent is well known to react specifically with formaldehyde to form a purple solution, whereas in the absence of FA, the reagent is colorless. Translation of this fundamental chemistry reaction into clinical relevance using our SPRi microarray, which measures refractive index changes, allowed us to detect HCHO concentrations as low as 30 ppb. To our knowledge, this is the lowest detection level known for HCHO using SPRi. The future goal for this research is to further lower the detection limits by using metal nanoparticles, and to apply this method for the detection of formaldehyde present in biological matrices such as urine and blood serum.