Project conclusion

Within NILbiochip, nanostructured protein biomarker chips were fabricated that improve significantly the assay sensitivity for diagnosis of sepsis.

Glass surfaces coated with epoxy resin were nanostructured by thermal nanoimprint lithography (NIL) using different designs and line & space arrangements. We expected that assay sensitivity will increase due to the increased surface area and roughness of the nanostructured surface. Interestingly, protein immobilization capacity was quite similar on nanostructured and non nanostructured chips indicating that the signal enhancement was most probably due to optical interference phenomena rather than increased surface area. However, the print buffer composition had critical impact on the overall system: as the surface became significantly more hydrophobic upon nanostructuring, printing reagents were added to improve surface wettability and protein immobilization. Depending on the period and the height of the nanostructures as well as the optical wavelengths chosen for the biomarker detection the surface can be tailored to achieve higher signal-to-noise ratios.

Other approaches that were proposed for signal enhancement of protein chips and were realized within NILbiochip include the preparation and integration of acrylic microlenses, printed optically active nanoparticles, and metal clusters fabricated by electrochemical pulse plating on pre-structured ITO slides. The Figure below shows a nanostructured biochip, the gold cluster chip and micro contact printed (µCP) imprinted gold cluster structures (triangles) for protein immobilization.



From left to right: a protein chip which is nanostructured on one length side; four microscopy images of gold cluster chips (5x5 µm; 5x10 µm; 10x5 µm; 10x10 µm); and image of µCP imprinted 20 nm gold clusters.