Determination of cyclic GMP concentration using a gold nanoparticle-modified optical fiber

Guanosine 3',5'-cyclic monophosphate (cGMP) produced from guanosine triphosphate (GTP) via soluble or particulate guanylyl cyclase (GC) is an important second messenger for signal transduction within cells. The currently used methods of measuring cGMP including radioimmunoassay and enzyme immunoassay involve the use of radioisotopes or tracers. To develop a cGMP assay that is label-free, non-radioactive, able to detect cGMP directly, and highly specific and sensitive, we used a gold nanoparticle-modified optical fiber (GNOF) conjugated with anti-cGMP antiserum to determine cGMP concentration based on localized surface plasmon resonance (LSPR). The optimal antisera dilution and incubation time for preparing the probe are 1:250 and 2 h, respectively. The sensor shows detection ranges of 0.0025-0.1 and 0.1-100 pmol/ml for acetylated cGMP and cGMP, respectively. The sensitivity for measuring acetylated cGMP is three orders of magnitude higher than that for cGMP. In addition, the biosensor can be stored at 4°C up to 4 week without losing sensitivity significantly.