Enhanced microcontact printing of proteins on nanoporous silica surface

Abstract

We demonstrate porous silica surface modification, combined with microcontact printing,as an effective method for enhanced protein patterning and adsorption on arbitrarysurfaces. Compared to conventional chemical treatments, this approach offersscalability and long-term device stability without requiring complex chemicalactivation. Two chemical surface treatments using functionalization with thecommonly used 3-aminopropyltriethoxysilane (APTES) and glutaraldehyde (GA) werecompared with the nanoporous silica surface on the basis of protein adsorption. Thedeposited thickness and uniformity of porous silica films were evaluated for fluoresceinisothiocyanate (FITC)-labeled rabbit immunoglobulin G (R-IgG) protein printedonto the substrates via patterned polydimethlysiloxane (PDMS) stamps. A morecomplete transfer of proteins was observed on porous silica substrates compared tochemically functionalized substrates. A comparison of different pore sizes (4–6 nm)and porous silica thicknesses (96–200 nm) indicates that porous silica with 4 nmdiameter, 57% porosity and a thickness of 96 nm provided a suitable environment forcomplete transfer of R-IgG proteins. Both fluorescence microscopy and atomicforce microscopy (AFM) were used for protein layer characterizations. A poroussilica layer is biocompatible, providing a favorable transfer medium with minimaldamage to the proteins. A patterned immunoassay microchip was developed todemonstrate the retained protein function after printing on nanoporous surfaces, whichenables printable and robust immunoassay detection for point-of-care applications.