Synthesis and application of molecularly imprinted polymers (MIP) and use of aptamers in the construction of lateral flow type rapid analysis devices for tetracycline determination

Author(s)

Rafael Rovatti Pupin

• Document type: Doctoral Thesis
• Press: Araraquara. 2021-07-27.
• Institution: Universidade Estadual Paulista (Unesp). Instituto de Química. Araraquara
• Defense date: 2021-06-22
• Advisor: Maria Del Pilar Taboada Sotomayor

Abstract

Emerging pollutants are a class of compounds released into the environment that cause pollution in terrestrial, aquatic and atmospheric environment; also, they can be found in food and water for human consumption. Drugs, especially antibiotics, are among the most found in the environment. Tetracycline belongs to a class of antibiotics widely applied in human and veterinary use due to its broad spectrum of action and, therefore, residues of this antibiotic are easily found in soil, water and food. Since continued exposure to drugs can be harmful to human health, rapid and selective methods to detect them are essential. Lateral flow tests were developed to determine tetracycline: in one of the tests molecularly imprinted polymers (MIP) were used and in the other system were applied aptamers, both components as a selective recognition phase. Initially, three different types of MIP were synthesized: traditional, core-shell and hollow (with high porosity). All materials were characterized by techniques such as scanning electron microscopy and infrared spectroscopy. After optimizing the analysis conditions, hollow MIP presented superior results for the identification of tetracycline: maximum binding capacity of 5.6 mg g-1 and 0.2 L mg-1 affinity constant. Hollow MIP also showed good results in selectivity tests, with higher retention for tetracycline compared to other drugs. Different types of samples fortified with tetracycline were evaluated and MIP showed recovery in the range of 74 - 96%, with linear range of 4.5 ‒ 155 μmol L-1 and the limits of detection and quantification of 4 e 13 μmol L-1, respectively. Due to the good results, the hollow MIP was applied as a recognition phase in one of the lateral flow systems. In this system, visual response indicating the presence of the analyte, after being recognized by the MIP, was based on a complexation reaction between tetracycline and Fe3+ cation, forming a coordinating compound with a dark yellow colour. This system was also quantified through the treatment of lateral flow strips images obtained using a smartphone. After optimizing all the necessary parameters, qualitative identification was obtained in 10 minutes of running. The efficiency of the tests was evaluated in the application of samples fortified with the analyte and through the quantitative results was obtained recovery values in the range of 73 - 104%; with linear range of 45 ‒ 180 μmol L-1 and the limits of detection and quantification of 17 e 45 μmol L-1, respectively. Another rapid test for tetracycline identification was structured using aptamers as selective recognition biomolecules. The colorimetric response of this system was based on the application of gold nanoparticles modified with aptamers. Nanoparticles modifications with the tetracycline-binding aptamer was successfully accomplished through the interaction between gold and aptamer thiol labelled aptamer. Preliminary tests for the construction of the test line (SiO2 nanoparticles modified with tetracycline) and control line (complementary aptamer strand) showed that the elution and colorimetric response were viable, requiring further optimization tests. Therefore, MIPs and lateral flow tests were successful in the identification and quantification of tetracycline. (AU)

• FAPESP's process: 17/20789-9 - Synthesis and application of Molecularly Imprinted Polymers (MIP) in the construction of rapid analysis devices based in lateral flow type for the detection of environmental contaminants
• Grantee: Rafael Rovatti Pupin
• Support Opportunities: Scholarships in Brazil - Doctorate