Resonance light scattering technique for simultaneous determination of cysteine and homocysteine using fluorosurfactant-capped gold nanoparticles

In this paper, based on the enhancement effect on resonance light scattering (RLS) intensity of fluorosurfactant-capped gold nanoparticles (FSN-capped AuNPs), homocysteine can be discriminated from cysteine by tuning the pH values of the 14 nm FSN-capped AuNP solutions. In contrast to the reported enhanced RLS of AuNPs for cysteine and homocysteine assays, the present method was improved by the following aspects: (1) cysteine and homocysteine could be determined simultaneously without separation techniques; (2) the incubation time of less than 2.0 min for FSN-capped AuNP aggregation was employed in the proposed approach, which is much shorter than those reported by RLS probes (e.g., 25 min and 60 min). Under optimum experimental conditions, the calibration curve was found to be linear over the range of 0.08–6.0 μM for cysteine and homocysteine with a detection limit of 0.04 μM. The applicability of the proposed method has been validated by determining cysteine and homocysteine in human urine samples with satisfactory results. Recoveries from spiked urine samples were in the range of 96.0–113.0%.