There is an increasing demand for lithography methods to enable the fabrication of diagnostic devices for the biomedical and agri-food sectors. In this regard, scanning probe lithography methods have emerged as a possible approach for this purpose, as they are not only convenient, robust and accessible, but also enable the deposition of “soft” materials such as complex organic molecules and biomolecules. In this report, the use of polymer pen lithography for the fabrication of DNA oligonucleotide arrays is described, together with the application of the arrays for the sensitive and selective detection of Ganoderma boninense, a fungal pathogen of the oil palm. When used in a sandwich assay format with DNA-conjugated gold nanoparticles, this system is able to generate a visually observable result in the presence of the target DNA. This assay is able to detect as little as 30 ng of Ganoderma-derived DNA without any pre-amplification and without the need for specialist laboratory equipment or training.
A colourimetric assay for the detection of DNA fragments associated with the oil palm pathogen Ganoderma boninense and other fungi DNA is reported. The assay is based on the aggregation of DNA-nanoparticle conjugates in the presence of complementary DNA from the target organism. Here, various designs of DNAnanoparticle conjugates were evaluated, and it was found that the best design gave a visually observable colour change with as little as 2 pmol of doublestranded DNA analyte even in the presence of a large excess of a mixture of noncomplementary DNA. Overall, this label-free system is rapid, sensitive, selective, simple in design, and easy to carry out. It does not require specialist equipment or specialist training for the interpretation of the results, and therefore has the potential to be deployed for agricultural diagnostics in the field.
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</strong></u><p>A colorimetric assay for the detection of DNA fragments associated with the oil palm pathogen Ganoderma boninense is reported, which is based on the aggregation of DNA-nanoparticle conjugated in the presence of complementary DNA from the pathogen. Here, various designs of DNA-nanoparticle conjugates were evaluated, and it was found that the best design gave a visually observable colour change with as little as 2 pmol of double-stranded DNA analyte even in the presence of a large excess of a mixture of non-complementary DNA. The assay was also able to differentiate analyte sequences with three or more single nucleotide mismatches. Overall, this label-free system is rapid, sensitive, selective, simple in design and easy to carry out. It does not require specialist equipment or specialist training for the interpretation of the results and therefore has the potential to be deployed of agricultural diagnostics in the field.</p><u><strong></strong></u>
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