A Novel Capacitive Biosensor for the Detection of Small Molecule S-Nitrosothiols

Small molecule S-nitrosothiols are a class of endogenous chemicals which are produced by various forms of nitric oxide synthase. The regulation of these molecules has been shown to play a role in control of a variety of bodily processes and disease models including breathing, blood pressure, pulmonary hypertension, and asthma. However, these molecules are extremely labile, making in vivo detection extremely challenging as most small molecule S-nitrosothiols exists at very low concentrations in the body. To overcome this challenge, we have developed a capacitive biosensor which employs an organic semiconductor that readily covalently crosslinks to all free amines, free thiols, and S-nitrosylated thiols in solution. Samples were treated with formaldehyde to block all free amines and free thiols, leaving only S-nitrosylated thiols. S- nitrosothiol bonding to the semiconducting surface of the sensing electrode changes its capacitance, allowing for extremely sensitive detection of S-nitrosothiols in biological samples. We will present evidence of attomolar detection of S-nitrosocysteine which can be abolished by the addition of Mercury to the fixing buffer, or by exposing the sample to UV light during fixing, both methods of degrading S-nitrosothiols. We will also present evidence of the presence of small molecule S-nitrosothiols in blood, saliva, and other biological samples.