On-Chip DNA Purification and Amplification with Minimum Equipment

On-chip magnets and thermal chamber coupled with a handheld microfluidics drive system

Problem

Integrating multiple conventional DNA/RNA analysis methods (e.g., DNA/RNA extraction, purification, elution, and amplification) into microfluidic chips can easily lead to exceedingly large, costly, and power-hungry systems. For example, conventional thermal cycling requires special care and additional “pre-PCR” isolation rooms to avoid contamination from previous assays. Similarly, magnetic beads are often used to wash or isolate nucleic acids which may require large, power-hungry electromagnetic systems to immobilize the beads, creating excessive heat emissions.

Solution

Combine various DNA/RNA analysis methods on a single chip and use simple microfluidic handling features to drive and move fluids accurately. This approach minimizes device footprint, power consumption, complexity, cross-contamination, and equipment cost. In this example, a handheld microfluidics drive system (including embedded magnets) purifies nucleic acids with beads without generating excessive heat. The device will drive the purified DNA/RNA directly to an on-chip thermal chamber, thus confining the entire amplicon within one chip and reducing the chance of cross-contamination.

DNA Purification by Magnetic Beads, Simplified

There are a few ways magnets can be positioned on-chip to purify DNA or RNA. For example, on Enplas’s proprietary Rotary Membrane Valve and Pump (RMVP) system, the magnet can be placed directly on the chip (aligned with open microfluidic valves) or placed on a separate rotating dial (independent of microfluidic valves). For the on-chip magnet, the RMVP accurately drives the bead solution using a rotary valve and pump, while the on-chip magnet stops the magnetic beads from moving, removing the supernatant and extracting the nucleic acid. Alternatively, for the rotating magnet, the beads are immobilized at a specific inlet, depending on the position of the dial. Thus, the same inlet can be used for mixing and achieving bead suspension to complete the purification.

Watch the video to see how combining a magnet, magnetic beads, and the RMVP system enables DNA purification using just a handheld device without complex equipment.

Secure DNA Amplification on the Same Chip

The combination of an accurate liquid flow and control system with an on-chip thermal chamber enables efficient thermal cycles required for PCR and other library prep systems. The RMVP drives carefully metered reagent volumes (e.g., PCR primer, the template, PCR enzyme mix, and water) in and out of the thermal chamber. While inside the chamber, a Peltier conducts the necessary thermal cycles. Following the DNA purification process outlined in the previous section, the amplicon is safely contained, minimizing the risk of cross-contamination.

Watch the video to see how the closed RMVP system drives and mixes multiple reagents before applying thermal cycles via the Peltier unit.