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2,4-Dichlorophenoxyacetic acid (2,4-D) is one important and well-known herbicide that is widely used in agriculture because of its advantages to regulate plant growth. However, the use of large quantities of the treated plants as animal feed leads to residues in meat, milk and eggs. Furthermore, the herbicide can drain away and contaminate ground and drinking water. The ingestion of 2,4-D-contaminated food and water causes damage to the inner organs of humans and animals, e.g., the kidneys and the liver.
Analytical assays based on molecularly imprinted polymers (MIPs) have emerged as a valuable tool in the field of environmental analysis due to the low production costs, stability, format adaptability and the possibility to imprint and thus their ability to recognize a wide variety of target analytes. With regard to optical sensing technologies, however, MIPs have only been used in considerably few applications, especially in fluorescence sensors. This limitation is basically due to the fact that the incorporation of a fluorescently responding moiety into a polymer matrix is challenging. One way to overcome this limitation is to use tailor-made fluorescent indicator monomers for direct transfer of the binding event into an optical signal and coat the MIP via reversible addition-fragmentation chain transfer (RAFT) polymerization as a thin layer onto the surface of silica nanoparticles as primary sensing element.
Here, we present the response behavior of the fluorescent MIP sensor particles in terms of sensitivity for 2,4-D detection (the so-called imprinting factor), discrimination ability against structurally similar compounds and performance in a phase-transfer assay (PTA) on chip, i.e., the implementation of the assay into a microfluidic chip environment, offering a novel simple and rapid way for the detection of herbicides.
2,4-Dichlorophenoxyacetic acid (2,4-D) is one important and well-known herbicide that is widely used in agriculture because of its advantages to regulate plant growth. However, the use of large quantities of the treated plants as animal feed leads to residues in meat, milk and eggs. Furthermore, the herbicide can drain away and contaminate ground and drinking water. The ingestion of 2,4-D-contaminated food and water causes damage to the inner organs of humans and animals, e.g., the kidneys and the liver.
Analytical assays based on molecularly imprinted polymers (MIPs) have emerged as a valuable tool in the field of environmental analysis due to the low production costs, stability, format adaptability and the possibility to imprint and thus their ability to recognize a wide variety of target analytes.5 With regard to optical sensing technologies, however, MIPs have only been used in considerably few applications, especially in fluorescence sensors. This limitation is basically due to the fact that the incorporation of a fluorescently responding moiety into a polymer matrix is challenging. One way to overcome this limitation is to use tailor-made fluorescent indicator monomers for direct transfer of the binding event into an optical signal and coat the MIP via reversible addition-fragmentation chain transfer (RAFT) polymerization as a thin layer onto the surface of silica nanoparticles as primary sensing element.
Here, we present the response behavior of the fluorescent MIP sensor particles in terms of sensitivity for 2,4-D detection (the so-called imprinting factor), discrimination ability against structurally similar compounds and performance in a phase-transfer assay (PTA) on chip, i.e., the implementation of the assay into a microfluidic chip environment, offering a novel simple and rapid way for the detection of herbicides.
As the interest in rapid and sensitive detection methods is growing, molecularly imprinted polymers (MIPs) are increasingly considered as an alternative to bio-macromolecular recognition units such as antibodies or enzymes due to their facilely tailorable selectivity towards certain analytes or a group of structurally related species. The low production costs, stability, robustness and format adaptability of MIPs combined with the possibility to imprint and thus their ability to recognize a wide variety of target analytes can be potentially useful in chemical sensor applications.[1] With regard to optical sensing technologies, however, MIPs have only been used in considerably few applications, especially in fluorescence sensors. This limitation is basically due to the fact that the incorporation of a fluorescently responding moiety into a polymer matrix is a challenge. One way to overcome this limitation is to use tailor-made fluorescent indicator monomers and thin MIP-shells on silica particles.[2]
Here, we present silica sensor particles with a thin MIP layer which was grown onto the silica surface via reversible addition-fragmentation chain transfer (RAFT) polymerization. The homogeneous MIP shell contains fluorescent phenoxazine-urea monomers as signal generation elements. The carboxylate salts of the antibiotic ampicillin (AMPI) and the herbicide 2,4 dichlorophenoxyacetic acid (2,4-D) were used as templates in those studies. In this case, hydrogen bonds are formed between the urea group of the fluorescent monomer and the carboxylate group of the template. To investigate the binding behavior of the MIPs and the control non-imprinted polymer (NIP) particles in terms of discrimination and imprinting factor, titration experiments with AMPI and 2,4-D salts were performed directly in organic solution. In order to study the detection possibilities in aqueous solution, a simple phase-transfer assay using fluorescence spectroscopy was investigated for both analytes.
2,4-Dichlorophenoxyacetic acid (2,4-D) is an important and well-known herbicide that is widely used in agriculture because of its advantages to regulate plant growth.1 However, the use of large quantities of the treated plants as animal feed leads to residues in meat, milk and eggs. Furthermore, the herbicide can drain off and contaminate ground and drinking water. The ingestion of 2,4-D-contaminated food and water can cause damage to the inner organs of humans and animals, e.g., the kidneys and the liver.
Analytical assays based on molecularly imprinted polymers (MIPs) have emerged as a valuable tool in the field of environmental analysis due to the low production costs, high stability, format adaptability and the possibility to imprint—and thus their ability to recognize—a wide variety of target analytes. Regarding optical sensing technologies, however, MIPs have only been used in considerably few applications, especially in fluorescence sensors. This limitation is basically because the incorporation of a fluorescently responding moiety into a polymer matrix is challenging. One way to overcome this limitation is to use tailor-made fluorescent indicator monomers or cross-linkers for direct transfer of the binding event into an optical signal and to coat the MIP via reversible addition-fragmentation chain transfer (RAFT) polymerization as a thin layer onto the surface of silica nanoparticles as primary sensing element.
Here, we present the response behaviour of fluorescent MIP sensor particles in terms of sensitivity for 2,4-D detection (the so-called imprinting factor), discrimination ability against structurally similar compounds (the discrimination factor) and performance in a phase-transfer assay (PTA) on chip, i.e., the implementation of the assay into a microfluidic chip environment, offering a novel simple and rapid way for the detection of herbicides in water.