19th December 2019

The contamination of the environment with pesticide residues has become one of the most serious problems of public health in the world, due to their wide application in agriculture industry to guarantee the crop yield and quality. This has necessitated the development of rapid, easy and highly sensitive approaches for the detection of pesticides. Aptamers offer a more cost effective method where the need for sophisticated instrumentation is minimized and can provide highly sensitive and accurate determination of pesticides residues. Compared with antibody – based immunosensors and enzyme – based biosensors for detection of pesticide residues, aptasensors exhibit better specificity and sensitivity, higher stability, more flexibility, easier artificial synthesis and longer shelf life.

Keeping in view the environmental concern and challenges associated with conventional strategies, Bala et al. demonstrated highly sensitive, selective and rapid method for detecting malathion, a toxic organophosphorous pesticide using a combination of aptamer, peptide and un-modified gold nanoparticle (AuNPs). The method employed aptamer (specific for the target) as a bio recognition element, cationic peptide as aggregation inducer and AuNPs as optical indicators for signaling the interaction of malathion with aptamer in real samples. Color of nanoparticles remained red in the absence of malathion as the peptide is bound to the aptamer. The complex however turned blue in the presence of malathion as the peptide was free to cause the aggregation (Figure 1). Direct visualization was possible without requiring complex instrumentation.

Figure 1. Left: Schematic representation of colorimetric assay for malathion based on aptamer, cationic peptide and gold nanoparticles. The gold nanoparticles remain red in the absence of malathion due to the interaction of aptamer and peptide whereas in the presence of malathion, the color of the particles turns blue as aptamer binds to malathion and peptide is free to aggregate the particles. Right: TEM images of (A) AuNPs, (B) AuNPs in the presence of peptide, (C) AuNPs in the presence of aptamer and peptide and (D) AuNPs in the presence of aptamer, malathion and peptide.

Cross-reactivity studies were also performed with other commonly used pesticides. The results showed high selectivity and specificity towards target malathion and negligible interference with other pesticides (Figure 2).

Figure 2. (A) Response of the proposed aptasensor towards potential interfering substances. (B) The plot of A650/520 of various non-target pesticides vs concentration of pesticides. The colour of the particles remained red for non-target pesticides as compared to malathion which confirmed the selectivity of the sensing platform.

Similarly, other pesticide specific aptamers targeting fipronil, fluoroacetamide, acetamiprid, organophosphorous pesticides etc. have been developed and widely applied for the detection of correlated pesticide residues both in food and environment management. At Aptamer Group, we are involved in continuous development of aptamer-based biosensors for similar targets and even small molecule detection using our high affinity aptamers. If you would like more information on such platforms, please contact us using the form below.

Reference:

Bala R., Dhingra S., Kumar M., Bansal K., Mittal S., Sharma RK & Wangoo N (2017). Detection of organophosphorous pesticide – Malathion in environmental samples using peptide and aptamer based nanoprobes. Chemical engineering journal. 311(111-116).

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