Fabrication of CdSe/ZnS quantum-dot-conjugated protein microarrays and nanoarrays

We demonstrate the fabrication and the detection of protein microarrays and nanoarrays, which are tagged by using colloidal CdSe/ZnS quantum dots (QDs), for the purpose of optical readout of those biochips. A microarrayer and a dip-pen nanolithography technique were used for the fabrication of QD-labeled protein microarrays and nanoarrays, respectively. The optical readout of those biochips was conducted by using a microchip scanner and a confocal scanning microscope in the case of the microarrays while an atomic force microscope was employed for characterizing the nanoarrays. We also report a possible way of reducing the 'doughnut phenomenon' in microarrays by varying the spot size from 300 μm to 100 μm, wherein the fluorescence intensity distribution becomes more uniform with decreasing spot diameter.