We are ready to go to the field with the eGFP arsenic reporter!
After trying different configurations, we went back to the spring 2014 prototype, with the lasercut chassis for stability, but most importantly, an acrylic filter we obtained from Knight Optical (510nm long-pass 50x10mm) for 6.30 GBP (British pounds). The long-pass at 510nm should remove the excitation blue LED + scattered light and allow the eGFP fluorescence light to pass through, which should help with the signal to noise ratio.
We demonstrate this briefly with the spectruino set-up using FITC dextran, which has similar excitation and emission wavelengths as eGFP. While FITC dextran doesn’t have scattering, the FITC fluorescence is higher so we can see more emitted light than with eGFP inside bacteria.
Then, we ran a series of AsIII standards that had been incubated with the eGFP bioreporter for 6 hours.
We finally see nice fluorescence increase, that can be used to detect definitely 50ug/L and also above 10ug/L arsenic.
The 6 hours incubation time was due to convenience of timing – shorter incubation times can be tested. But this is a great start to go our for real world water collection and up to the lake draining a former arsenic mine in Valais.
Field testing to come, so we can figure out how to make it robust and compatible for a big hike (do we really bring this many standard vials??? what about them cables?).