Integrated microneedle-smartphone nucleic acid amplification platform for in-field diagnosis of plant diseases

We demonstrate an integrated microneedle (MN)-smartphone nucleic acid amplification platform for “sample-to-answer” diagnosis of multiplexed plant pathogens within 30 min. This portable system consists of a polymeric MN patch for rapid nucleic acid extraction within a minute and a 3D-printed smartphone imaging device for loop-mediated isothermal amplification (LAMP) reaction and detection. We expanded the extraction of the MN technology for DNA targets as in the previous study (ACS Nano, 2019, 13, 6540–6549) to more fragile RNA biomarkers, evaluated the storability of the extracted nucleic acid samples on MN surfaces, and developed a smartphone-based LAMP amplification and fluorescent reader device that can quantify four LAMP reactions on the same chip. In addition, we have found that the MN patch containing as few as a single needle tip successfully extracted enough RNA for RT-PCR or RT-LAMP analysis. Moreover, MN-extracted RNA samples remained stable on MN surfaces for up to three days. The MN-smartphone platform has been used to detect both Phytophthora infestans DNA and tomato spotted wilt virus (TSWV) RNA down to 1 pg, comparable to the results from a benchtop thermal cycler. Finally, multiplexed detection of P. infestans and TSWV through a single extraction from infected tomato leaves and amplification on the smartphone without benchtop equipment was demonstrated. [Display omitted] •Rapid extraction of RNA from plant leaves by a simple press and retraction process using a microneedle (MN) patch.•An integrated MN-smartphone platform for on-site “sample-to-answer” detection of plant pathogens within 30 min.•The MN-smartphone platform can simultaneously screen multiple target pathogens from a single MN extraction.•The method enables detecting tomato spotted wilt virus as early as 5 days after inoculation in asymptomatic tomato plants.