A selective probe based on 3‑aminophenyl boronic acid assembly on dithiobis(succinimidylpropionate) functionalized gold nanoparticles for sialic acid detection in human serum

Sialic acid (SA) is a notable tumor marker in human. Its increased level beyond the normal concentration in human biological samples is related to different kinds of cancers development. In this contribution, a novel colorimetric assay is reported for SA detection in form of N-acetylneuraminic acid. The sensitive detection strategy is proposed via the specific SA induced aggregation of 3‑aminophenyl boronic acid (3APBA) assembled on dithiobis(succinimidylpropionate) functionalized gold nanoparticles (AuNPs-DSP). DSP was functionalized on AuNPs through a strong AuS interaction and 3APBA was assembled on AuNPs-DSP by the amine coupling reaction between the carboxyl group of DSP on gold nanoparticles surface and the amino group of 3APBA to generate a covalent amide bond. The addition of 3APBA to buffered AuNPs-DSP generated a ruby red colloidal nanosensor. With increasing concentration of SA, a probe color turned rapidly from red to blue-gray via aggregation of AuNPs-DSP-3APBA. At optimal conditions, the absorbance ratio (A700/A520) was linear with SA concentrations ranging from 0.08 to 0.25 mM and 0.30–0.70 mM. A limit of detection of 35.0 μM was achieved which is the lowest amongst reported colorimetric methods for SA determination. The practical efficacy of the assay was demonstrated on human serum, along with no interfering effects and satisfactory accuracy and precision.