| Part | Description | Manufacturer / Partname |
|---|---|---|
| A fairly strong LED | In our case a 3W green 520nm LED | Cree XP-E on star circuit board |
| A cooling element | Used to prevent the LED from overheating | Fischer Elektronik ICK S |
| A constant-current-source | To ensure static LED light (no flickering) | Roschwege GmbH KSQ-3W |
| An AC/DC rectifier | Used to grant direct current to the LED | Goobay 67951 |
| Two optical lenses | Here we used two identical 60mm lenses | Thorlabs AC254-060-A |
| A camera | We used a SLR camera | Canon 550D |
| A microfluidics chamber | Our chamber consists of an iRIf slide attached to a PDMS flow chamber | Made ourselves |
| Magnets | Used to attach the flow-cell to the device | 5mm Neodymium magnets |
| A small syringe | We used a regular 10 ml syringe | BRAUN INJEKT 10ml |
| A microfluidic tube | Used to connect the flow chamber with the syringe | - |
| A case for the device | 5 mm thick acrylic glass cutouts to hold the parts in place | Ordered at http://formulor.com |
Team:Freiburg/Results/Own Device
Results: Device
Hier nochmal das ergebniss zeigen oder das Video nur auf der Main results page? Zudem wäre ne kleine Kostenaufstellung cool! (Stefan)
Here you'll see what we were able to measure with our own device, as well as how to build your own, low-priced iRIf device.
Our own device is able to detect antigen/antibody binding
For testing our device we bound proteins derived from rabbits onto an iRIf slide in distinct spots (Fig 1 D). The proteins used were polyclonal anti-HCV (hepatitis C virus) antibodies, which we then aimed to detect with anti-rabbit antibodies. The reason for using the rabbit/anti-rabbit couple in this series of experiments was to reproduce a successful measurement with this binding couple which we previously performed in our regular measuring device. The binding layer on the iRIf slide consisted of an APTES/PDITC surface. The spots on the slide were made by pipetting 3 µl (500 µg/ml) rabbit-anti-HCV protein and 3 µl (1 mg/ml) BSA in an alternating pattern onto the slide. After incubation, the slide was blocked for 30 min in BSA solution. A Canon 50D camera was used to record the measurement and was set to take one picture every 5 seconds. The exposure time was set so that the pixels in the image were approx. 80% of maximum light saturation before the solution was flown onto the chip. The antibody solution was pipetted into the flow-chamber without the use of any microfluidics device. Instead a syringe was loaded with 500 µl [5 µg/ml] anti-rabbit antibody solution (diluted in PBS) and slowly released into the binding chamber of the device by gently dispensing the solution from the syringe. As can be seen in the figure C, the quotient picture clearly showed binding of anti-rabbit to the rabbit protein spots. The BSA control-spots showed none or negligible unspecific binding.
How to build your own device
General principle
As can be seen in the illustration below, the basic setup is fairly simple. Light from an LED enters a lense where the light rays are made parallel. To achieve this, the distance from LED to the lense has to be exactly one focal length. The light then hits the iRIf slide, where it gets reflected (reflecting at the same angle it hit the slide) and enters a second lense, whose purpose is to project a sharp image of the slide onto the CCD chip of the camera.
Construction guidance
A major problem that we confronted when building the device from scratch was to assure that all components are at the exact distance and angle to each other. This is crucial as a slight misplacement of a component may lead to lower signal strengh, blurred images or in the worst case no signal at all. This can be difficult since our device doesn't rely on straight angles. We overcame this problem by designing a case for the device that ensures the right placement of the components in the device. This was archieved by calculating all the distances
