#FUTURE FRAGMENTS 0.19 PORTABLE#
Optical imaging technologies have been miniaturized to detect fluorophores for on-chip optofluidic microscopy 9, 10, portable tomographic microscopy 11 and cell-phone based microscopy 12, 13. Gold standard techniques for highly sensitive DNA quantification are optical in nature and generally require bulky instrumentation for readout, such as fluorescence 3, 4, 5 and plasmonic based detection 6, 7, 8. Miniaturized technologies for quantification and sizing of nucleic acids can serve as point-of-use tools for research and clinical applications ranging from infectious and genetic disease testing to screening of environmental samples for viral and pathogen detection 1, 2. Using this impedance sensor, purified PCR products could be analyzed within ten minutes to determine DNA fragment length and quantity based on comparison to a known DNA standard. Additionally, our approach allowed distinguishing beads with similar molar concentration DNA fragments of different lengths. The minimum DNA amount of a 300 bp fragment coupled on beads that could be robustly detected was 0.0039 fmol (1.54 fg or 4750 copies/bead). Multi-frequency IPR correlated positively with DNA amounts and was used to calculate a DNA quantification score. Technical and analytical performance was evaluated using beads containing purified Polymerase Chain Reaction (PCR) products of different lengths (157, 300, 613 bp) with DNA concentration ranging from 0.039 amol to 7.8 fmol. We apply a custom-made microfluidic chip to detect DNA molecules bound to beads by measuring Impedance Peak Response (IPR) at multiple frequencies.
Here we introduce the integration of 2.8 μm paramagnetic beads with DNA fragments. However, limitation in probe selectivity and variable levels of non-target material in complex biological samples can lead to nonspecific binding and reduced sensitivity. Electronic biosensors for DNA detection typically utilize immobilized oligonucleotide probes on a signal transducer, which outputs an electronic signal when target molecules bind to probes.
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