Cross linking modulator

Fabrication of elastic collagen nano- and micro-patterns is a challenging task due to the susceptibility of type-I collagen to undergo rapid gelation, and van-der-waals and capillary interactions between the nano-stamp and the printed surface that provoke a collapse of the soft PDMS nano-stamps onto the glass surface. To address these issues and achieve high precision micro- and nano-patterns on elastic platforms we (i) substituted regular PDMS nano-stamps with composite stamps, veneered with a submillimeter-thick hard PDMS (hPDMS) for non-collapsing high-definition printing surfaces (Schmid and Michel, 2000 ; Tabdanov et al., 2015 ), and (ii) substituted collagen with a-collagen-1 rabbit pAb (AbCam, Cambridge, UK), conjugated with biotin and a fluorescent tag, to ensure cross-linking of the antibody to PAA gels and for fluorescence visibility, respectively. For hPDMS we mixed 3.4g of VDT-731 (Gelest, Inc.), 18mL of Pt catalyst (Platinum(0)-2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane complex solution) (Sigma-Aldrich) and one drop of cross-linking modulator (2,4,6,8-Tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane) (Sigma-Aldrich). Next, immediately before use, we added 1g of HMS-301 (Gelest, Inc.) and thoroughly mixed it for 30sec on vortex mixer (Odom et al., 2002 ).