WatsOn

Part of the biosensor system Cellock Holmes are our agar chips. They contain our engineered sensing cells that fluoresce in the presence of the pathogen Pseudomonas aeruginosa. However, bacteria are small and the fluorescent signal cannot be seen with the naked eye. Thus the central question "What's on the chip?" remains.

To answer this question we present our measurement device WatsOn.

Application

How to use WatsOn This scheme illustrates handling WatsOn when testing the 2D biosensor for a fluorescent signal.

Features

WatsOn

WatsOn fulfills several tasks in our system:

• incubate the sensing cells and the sampling chip
• prevent escape of potentially sampled pathogens and our genetically engineered cells
• illuminate the chip with the right excitation wavelength for GFP or iLOV
• take photos and time lapse shootings of the chips
• analyze the fluorescence signal
• give feedback to the user about the presence or absence of P. aeruginosa

WatsOn is designed such that it can be easily copied. Our work heavily emphasizes the Open Source concept. Therefore, the construction manual and all technical detailes are published on our wiki. Analogous to our OD/F device, we used low-cost and easily available parts.

Software

Hardware

Hardware components

Our hardware consists of the casing and the electronical components. The casing which can be seen in the Features section[1] was build from laser cutted acrylic glass.
The electronic circuit is a combination of the components displayed in the image. We combined the Raspberry Pi, a small single-board computer, running a Linux operating system and an Arduino board to control the LEDs and a Peltier heater. For taking an image we connected the Raspberry Pi camera to the board.
A detailed description of all components and the wiring can be found here [2].

Achievements

When developing our ‘’’WatsOn’’’ our goal was to build a system that

• incubates the sensing cells and the sampling chip
• prevents escape of potentially sampled pathogens and our genetically engineered cells
• illuminates the chip with the right excitation wavelength for GFP or iLOV
• takes photos and time lapse shootings of the chips
• uses cheap filter slides to block the light emitted from the LEDs
• analyzes the fluorescence signal
• gives feedback to the user about the presence or absence of P. aeruginosa through a GUI (graphical user interface)
• is portable and fast in analysing the images