Five functional silanes, 3-aminopropyltriethoxysilane (APTES), 3-aminopropyltrimethoxysilane (APTMS), N-(2-aminoethyl)-3-aminopropyltriethoxysilane (AEAPTES), and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (AEAPTMS), and N-(6-aminohexyl)aminomethyltriethoxysilane (AHAMTES) were assessed for the preparation of hydrolytically stable amine-functionalized silica substrates. These can be categorized into three groups (G1, G2, and G3) based on the intra-molecular coordinating ability of the amine functionality to the silicon center. Silanizations were carried out in anhydrous toluene as well as in the vapor phase at elevated temperatures. Aminosilane-derived layers prepared in solution are multilayers in nature and those produced in the vapor phase have monolayer characteristics. In general, vapor-phase reactions are much less sensitive to variations in humidity and reagent purity, are more practical than solution-phase method, and generate more reproducible results. Intra-molecular catalysis by the amine functionality is found to be important for both silanizaton and hydrolysis. The primary amine group in the G1 silanes (APTES and APTMS) can readily catalyze siloxane bond formation and hydrolysis to render their silane layers unstable toward hydrolysis. The amine functionality in the G3 silane (AHAMTES) is incapable of intra-molecular catalysis of silanization so that stable siloxane bonds between the silane molecules and surface silanols do not form easily. The secondary amine group in the G2 silanes (AEAPTES and AEAPTMS), on the other hand, can catalyze siloxane bond formation, but the intra-molecular catalysis of bond detachment is sterically hindered. The G2 silanes are the best candidates for preparing stable amine-functionalized surfaces. Between the two G2 aminosilanes, AEAPTES results in more reproducible silane layers than AEAPTMS in the vapor phase due to its lower sensitivity to water content in the reaction systems.

A major challenge in tissue engineering is to reproduce the native 3D microvascular architecture fundamental for in vivo functions. Current approaches still lack a network of perfusable vessels with native 3D structural organization. Here we present a new method combining self-assembled monolayer (SAM)-based cell transfer and gelatin methacrylate hydrogel photopatterning techniques for microengineering vascular structures. Human umbilical vein cell (HUVEC) transfer from oligopeptide SAM-coated surfaces to the hydrogel revealed two SAM desorption mechanisms: photoinduced and electrochemically triggered. The former, occurs concomitantly to hydrogel photocrosslinking, and resulted in efficient (>97%) monolayer transfer. The latter, prompted by additional potential application, preserved cell morphology and maintained high transfer efficiency of VE-cadherin positive monolayers over longer culture periods. This approach was also applied to transfer HUVECs to 3D geometrically defined vascular-like structures in hydrogels, which were then maintained in perfusion culture for 15 days. As a step toward more complex constructs, a cell-laden hydrogel layer was photopatterned around the endothelialized channel to mimic the vascular smooth muscle structure of distal arterioles. This study shows that the coupling of the SAM-based cell transfer and hydrogel photocrosslinking could potentially open up new avenues in engineering more complex, vascularized tissue constructs for regenerative medicine and tissue engineering applications.

Modification with gold black considerably increased the detection current of protruding micropillar electrodes in microfluidic electrochemical enzyme-linked immunosorbent assay (ELISA). There has been a growing interest in the miniaturization of analytical systems for biochemical sensing applications because miniaturized systems could offer many potential advantages over the conventional assay platforms. Owing to their simplicity

For superhydrophobic surfaces immersed in water, a thin layer of air could be entrapped in the solid/liquid interface.