Reduced fluoresceinamine as a fluorescent sensor for nitric oxide

Abstract

A new fluorescent sensor for nitric oxide (NO) is presented that is based on its reaction with a non fluorescent substance, reduced fluoresceinamine, producing the highly fluorescent fluoresceinamine. Using a portable homemade stabilized light source consisting of 450 nm LED and fiber optics to guide the light, the sensor responds linearly within seconds in the NO concentration range between about 10-750 μM with a limit of detection (LOD) of about 1 μM. The system generated precise intensity readings, with a relative standard deviation of less than 1%. The suitability of the sensor was assessed by monitoring the NO generated by either the nitrous acid decomposition reaction or from a NO-releasing compound. Using relatively high incubation times, the sensor also responds quantitatively to hydrogen peroxide and potassium superoxide, however, using transient signal measurements results in no interfering species.

Keywords: NO sensor; fiber optics; fluorescence; reduced fluoresceinamine.

Figure 1.

Chemical structures of fluoresceinamine (a) and probable reduced fluoresceinamine (b).

Figure 2.

Chemical structure of DEANO.

Figure 3.

Fluorescence profile (excitation at 450 nm and emission at 522 nm) before and after mixing NO with reduced fluoresceinamine (the arrow shows the point were NO was added).

Figure 4.

(a) Fluorescence emission spectra of reduced fluoresceinamine in the presence of increasing amounts of NO (excitation 450 nm); and, (b) typical calibration plot for NO (excitation at 450 nm and emission at 522 nm).

Figure 5.

Detection NO present in aqueous solution as a result of production from the reaction of nitrite and sulfuric acid (a) and from the hydrolysis of DEANO (b).

Figure 6.

Interfering species assessment (concentration of all species is about 400 μM): (a) steady state fluorescence after one hour; and (b) initial fluorescence variation of the sensor in contact with NO (▬), H₂O₂ (^…) and KO₂ (─).