Fig. 7: The portable colorimetric biosensor.

a The cannabinoid biosensor was configured into a portable biosensor the output of which can be monitored by the eye. This biosensor workflow using the colorimetric strain KM205 consists of (1) Preparing the biosensor strain by activating it with concentrated media (this solution also includes the DOPA and O-da supplement), (2) adding the sample to be measured in the portable biosensor device, (3) adding the activated biosensor yeast to the device and incubating 4–16 h, (4) observing the color that was produced or measuring the signal by cell phone camera. b To test the portable biosensor workflow, a concertation series of CP55940 from 30 pM to 300 nM was added to the test wells (T) in of ten biosensor devices. Positive control wells (C + ) in each device had 300 nM CP55940 each and no negative control wells (C−) no cannabinoid. After the addition of the biosensor and 16 h of incubation, the color in test wells could be detected by eye down to 30 pM CP55940. c To quantify the biosensor signal for the portable colorimetric biosensor the above experiment was made in triplicate and the O-da-betacyanin pigment measured from a cellular phone photograph (see “Methods”). This resulted in a typical dose–response curve. For (c), data presented as mean + /− standard deviation. n = 3 biologically independent samples. Source data are provided in the Source Data file.