A novel AuNPs colorimetric sensor for sensitively detecting viable Salmonella typhimurium based on dual aptamers

A simple AuNPs-based colorimetric aptasensor for chlorpyrifos detection

“…Aptamers, a class of single strand oligonucleic acids, are selected by systematic evolution of ligands by exponential enrichment (SELEX) [15 − 19], which possesses superior advantages over traditional recognition molecules, because of their nontoxicity, high speci city, high a nity, low cost and easier to synthesize and modify [20 − 23]. According to recent researches, highly speci city aptamers for diverse target substances (proteins [24], exsomes [25], cells [26,27], ions [28,29], bacterial [30], pesticides [31 − 33], etc.) have been screened.…”

Recent Advances in Aptamer Sensors

“…AuNPs were functionalized with aptamers equipped with colorimetric smartphone technology for a sensitive and selective Cd 2+ detection strategy based on the AuNP aggregation induced by polydiene dimethyl ammonium chloride (PDDA) [ 86 ], in which the selective aptamer for Cd 2+ shows a stable complementary hybridization with the PDDA. In the presence of Cd 2+ , the aptamer leaves the PDDA and binds to the Cd 2+ ; AuNP aggregation is induced by the aptamer leaving the PDDA, which induces the solution’s color change from red to blue, with a linear range of 1–400 ng/mL and a LOD of 1 ng/mL, using a smartphone device as indicated in Figure 1 B. Chen et al also used aptamer–AuN-induced aggregation under the effect of a highly saline solution for assaying viable Salmonella typhimurium ( S. typhimurium ) bacteria using a dual aptamer approach, in which one was functionalized with magnetic beads to capture S. typhimurium and the other was used for PCR amplification, as shown in Figure 1 C [ 87 ]. Finally, the hybridization between the amplicons and the AuNP probe took place for 5 min before adding MgSO 4 to induce the aggregation.…”

“…Finally, the hybridization between the amplicons and the AuNP probe took place for 5 min before adding MgSO 4 to induce the aggregation. The system showed a linear relationship for S. typhimurium from 3.3 × 10 1 to 3.3 × 10 6 CFU/mL, with LODs of 33 and 95 CFU/mL for detection by the naked eye in pure culture and milk, respectively ( Table 1 ) [ 87 ]. S. typhimurium bacteria have also been detected via AuNP aggregation through competitive aptamer–target binding under the influence of salts, as inducers of aggregation, with a linear range of 100 to 10 9 CFU/mL and LOD of 16 CFU/mL, as reported by Jiecan [ 88 ].…”

“…( B ) Schematic illustration of the colorimetric aptasensor for Cd 2+ assay based on AuNP aggregation, reproduced from [ 86 ]. ( C ) Schematic procedure for an S. typhimurium bacterium assay via a proposed colorimetric SMBs-Apt1 sandwich strategy, reproduced from [ 87 ]. ( D ) Schematic illustration of a colorimetric aptasensor assay for AFM1 based on salt aggregation of AuNPs induced by AuNP–aptamer competitive binding, reproduced from [ 89 ].…”

“…Similarly, a colorimetric aptasensor based on the aggregation of AuNPs as a signal transducer using cationic perylene probe as gold aggregating agent (CPP) was also provided by Lerdsrias et al for assaying aflatoxin B1 (AFB1), with a LOD of 0.18 ng/mL [90], as shown in Figure 2A. As previously discussed, several colorimetric aptasensors were developed based on AuNP-induced aggregation with different targets such as malathion, Cd 2+ , Salmonella typhimurium, and AFB1, changing the specific aptamer functionalized with the AuNPs [85][86][87][88]90]. The question is what the role of these targets and others in the stability and instability of AuNPs in solution is, and if this could influence the salt-induced AuNP aggregation or not, affecting the reliability of the proposed strategies.…”