Dendrimer porphyrin-terminated polyelectrolyte multilayer micropatterns for a protein microarray with enhanced sensitivity

Through a combination of layer-by-layer (LbL) self-assembly (SA) and lift-off methods, a dendrimer-coated polyelectrolyte multilayer micropattern was prepared for protein microarrays. A silicon substrate was patterned with a photoresist thin film using conventional photolithography, and then poly(ethyleneimine) (PEI) and poly(sodium 4-styrenesulfonate) (PSS) were alternatively deposited onto the substrate surface using spin-assisted self-assembly. A well-defined multilayer microarray was produced by subsequent removal of the photoresist template by a lift-off process. Dendrimer porphyrin (DP) was successively immobilized onto the PEI-terminated micropatterns via electrostatic interactions between the negatively-charged DPs and positively-charged PEI segments. Because of strong fluorescence from focal porphyrins, the homogeneous covering of DPs onto the multilayer micropatterns was easily confirmed using fluorescence microscopy. Atomic force microscopy (AFM) also showed morphological change of micropatterned surfaces by DP immobilization. Based on these results, IgG was immobilized on the DP-coated protein microarrays, and immunoassays were performed to demonstrate that the DP-coated microarrays yielded a higher fluorescence signal and were more sensitive than the control microarrays that were coated with linear PAA polymer instead of DP due to the multiple functional groups present on the DP-coated arrays and their increased surface area relative to control microarrays.