By Neil Sharma
A customer recently asked if real-time PCR testing can be done in the field or in areas with limited resources? Yes! The Hunter® instrument is designed to be used at the point-of-need, even if the point-of-need is the back of a truck. Recently we loaded up my SUV and went out into the field to show how this could be done.
First, a little bit about the Hunter® device. It is an easy-to-use real-time PCR instrument with several features which make it ideal for use in a laboratory or out in the field:
- The instrument doesn’t require calibration so it is ready to use right out of the box (or out of the travel case)
- The integrated touch-screen and on-board software means an external laptop isn’t needed
- It consumes only a little bit of power which means it can be powered using vehicle power
- It can be interfaced with a GSM modem allowing reports to be sent wirelessly back to a central quality control laboratory or other location the same way you send a text message from your cellphone.
- The Hunter® test kits contain freeze-dried reagents allowing the kits to be transported to the field at ambient temperature. No cooler full of ice required.
To get started, we put the Hunter® and some needed auxiliary equipment into a custom designed travel case. This case has wheels and an extendable handle allowing it to be easily transported, or even checked onto an airplane as baggage. A Pelican® case off Amazon.com would also work. The auxiliary equipment included a small heat block, a small microcentrifuge, a pipet, a tube rack, and some gloves.
For this adventure we decided to test food samples for pork DNA using our Porcine Food Verification kit.
The ‘adventure’ begins
Where is the best place to get some samples for our tailgating party? The grocery store! We stopped at our local Stop and Shop and picked up chicken, lamb, beef and pork. Next stop, the parking lot of our hometown Ravens’ stadium. All the needed equipment easily fit in the back of my SUV. Power for the Hunter®, the heat block, and the centrifuge was provided using a 400 watt inverter that connected directly to the vehicle battery using small clamps, similar to jumper cables. Alternatively, some inverters can be plugged directly into a car power plug if it has sufficient amperage. Inverters takes the 12V DC power provided by the vehicle and converts it into clean 120V AC power needed to power line voltage equipment. To make sure you do not drain the battery completely, the vehicle can be started every once in a while (say every hour for 10 minutes) to ensure that the battery remains fully charged.
A little bit more about inverters: The standard wall power outlets at your home and office provides clean AC power in a pure sine wave as generated by the power company. Your car or truck produces DC power and inverters function by converting this DC input to AC output. However, most inverters produce a square wave or a ‘modified sine wave’. This means the AC power produced is similar to but not identical to the power provided by a wall outlet. This is OK for many applications or limited use but can cause problems with sensitive electronic devices. Using a ‘pure sine wave inverter’ eliminates this problem and is only a bit more expensive. These enhanced inverters produce power that is identical to that provided by wall outlets. This is the only type of inverter that we use and recommend.
Back to our trip and Tailgating with the Hunter. We processed the variety samples using our standard protocol for sample prep and our Porcine DNA test kit. Briefly, swabs were used to carefully collect residue from the meat samples, DNA was then extracted from the swabs using a simple heating step in buffer followed by a quick spin in the centrifuge. We were careful to change gloves between handling the different meat samples to avoid any chances of cross-contamination. The extracted DNA was then mixed with the freeze-dried PCR reagents and loaded into the Hunter® instrument for analysis.
After about an hour, we had our results. In this test only the pork sample came up positive. So the meats at the supermarket WERE correctly marked. (BTW, other tests we have done showed some hot dogs labels as chicken as also containing at least trace amounts of pork.) Once the test completed I had the Hunter automatically email the reports so I could see them on my cellphone while we were hanging out waiting for the game to start.
Real-Time PCR can be done in the laboratory and out in the field. So pack up your Hunter® and get out there!
Neil Sharma is a molecular biologist and technology enthusiast. His passion is developing new and innovative products that solve important problems. He has a Ph.D. from Rice University and currently lives in Bethesda, Maryland.