Microfluidic platform for gold nanoprobe based DNA detection

Due to the importance and wide applications of the DNA analysis, there is a need to make genetic analysis more available and more affordable. This work describes a microfluidic platform for colorimetric DNA detection based on gold nanoprobes, providing sensitive and accurate sensor operating using small volumes of solutions and without the need for substrate functionalization. Microfluidic chip of high aspect ratio, smooth and nearly vertical sidewalls was fabricated in PDMS using a SU-8 mould for patterning. Planar microlenses were incorporated to converge light into the sample increasing 6× the signal-to-losses ratio. The optimized platform enabled detection of single nucleotide polymorphism using target DNA concentration below the limit of detection of the conventionally used microplate reader with 10× lower solution volume. Simultaneously, to enable on chip reagents mixing, a PDMS micromixer was developed and optimized for the highest efficiency, low pressure drop and short mixing length.