To get one step closer to our final approach, we expressed His-GFP directly on Ni-NTA coated iRIf-slides. Therefore, we pipetted 15 µL of our DiaMIX containing the His-GFP DNA template and the DiaMIX without DNA as a negative control on a slide. The slides were incubated for 3 h at 37°C and additionally overnight at 4°C. We performed an iRIf measurement where biotinylated anti-GFP was flushed over the slide, followed by Cy5-labeled streptavidin. In the iRIf, the signal was really weak. Nonetheless, the strep-Cy5 bound to the biotinylated anti-GFP and therefore enabled a detection via a microarray scanner optimized for the detection of Cy-5. The result of the microarray scan at 635 nm is shown in figure 10. We were able to detect small amounts of cell-free expressed His-GFP that diffused to the glass surface and bound to the Ni-NTA with the microarray scanner. The weak binding shows that this part of our systems still needs some optimization.
In-chamber Expression of GFP
The last step towards a final application in the DiaCHIP is the performance of a cell-free expression reaction between the silicone and the glass slide of the microfluidic chamber. Immobilized, linear DNA on the PDMS slide should be transcribed and translated into proteins. Due to time constraints, we were not able to optimize this process. Nonetheless, our initial results can be found on this results page!.
Cell-free Expression of Disease-Specific Antigens
Sadly, we could not show binding of the respective antibodies/serum with the iRIf measurement device. This could be due to folding problems of the antigen during cell-free expression. Moreover, the concentration of expressed C. tetani antigen might not have been high enough to be detected by iRIf measurements.