Dual sensing reporter system of assembled gold nanoparticles toward the sequential colorimetric detection of adenosine and Cr(III)

A facile and sensitive sequential colorimetric detection strategy for adenosine and Cr³⁺ has been presented by using the aptamer and 11-mercaptoundecanoic acid assembled gold nanoparticles. The thiolated DNA and 11-mercaptoundecanoic acid was simultaneously assembled to the surface of gold nanoparticles in one step by gold-sulfur interaction. Adenosine aptamer was linked to functionalized gold nanaoparticles based on the strict complementary nature of the DNA base pairs. Conformational change of aptamer will be induced due to its specific binding with targets. As a result, this aptamer tethered aggregated nanoparticles underwent fast disassembly into dispersed nanoparticles upon binding of adenosine, and this distance change between particles induced a distinct solution color changing from blue to red. The dispersed particles were sensitive to Cr³⁺ due to the chelation effect between the carboxyl group of 11-mercaptoundecanoic acid and metal ions, and further occurred obvious aggregation accompanying with a color change from red to blue. Depended on this principle, a sensitive and selective sequential colorimetric sensor for detection of adenosine and Cr³⁺ was developed. The proposed colorimetric sensor exhibited wide linear ranges and low detection limits towards the detection of adenosine and Cr³⁺. Regarding adenosine, linear range was 1 × 10⁻⁷ ∼ 1 × 10⁻⁴ M with low detection limit of 1.8 × 10⁻⁸ M, and the naked eye detection limit was estimated as 20 μM. With regard to Cr³⁺, good linear relationship was ranged from 1 × 10⁻¹⁰ to 1 × 10⁻⁶ M with low detection limit of 1.7 × 10⁻¹¹ M，and the naked eye detection limit was as low as 0.1 nM. Meanwhile, bifunctional recognition was successfully used for practical human urine samples with good recoveries from 89.0% to 112.6% for adenosine and 90.2%–113.4% for Cr³⁺. It also highlights the potential applications of other aptamers and ligands in cascade analysis of other analytes.