Protein-protected red emittive copper nanoclusters as a fluorometric probe for highly sensitive biosensing of creatinine

A simple fluorescent bioassay for real time, ultrasensitive and highly selective determination of creatinine is extremely desirable in clinical science. Herein, we describe red-emittive bovine serum albumin-modified copper nanoclusters (BSA-CuNCs) applied as a precise fluorescent nanoprobe for the optical recognition of creatinine. The fluorescence of the BSA-CuNCs was considerably decreased by the addition of creatinine in a concentration-dependent manner. The observed experimental creatinine-induced emission quenching is attributed to the formation of non-fluorescent coordination complexes between creatinine and the BSA-CuNCs probe. The proposed fluorimetry approach enables the optical quantification of creatinine with a lowest detection limit of around 50.00 x 10(-9) mol dm(-3). In addition, the emission quenching ability of various potential interfering moieties for the BSA-CuNCs was investigated; only creatinine was found to be capable of successfully decreasing the emission spectral response of the BSA-CuNCs. Therefore, this creatinine-stimulated emission quenching can be utilized for the specific determination of creatinine using the BSA-CuNCs as a probe. The turn-off fluorescence characteristics and visible colour change to the naked eye of the probe under UV light illumination revealed the highly specific sensing of creatinine. Furthermore, this assay was successfully employed in the determination of creatinine in urine (human) samples, with very good recoveries (97.63% to 102.43%).