Microfluidic Networks Made of Poly(dimethylsiloxane), Si, and Au Coated with Polyethylene Glycol for Patterning Proteins onto Surfaces

Abstract

Microfluidic networks (μFNs) are passive (self-filling) devices incorporating microchannels for guiding minute volumes of fluids over surfaces. μFNs can be employed to localize the deposition of proteins from aqueous solutions onto substrates, for example. The walls of the channels must be hydrophilic for this purpose and should ideally resist the adsorption of proteins. We made μFNs using poly(dimethylsiloxane) (PDMS), Si/SiO2, and Au-covered Si and derivatized them with poly(ethylene glycol)s (PEGs) to fulfill both of these requirements. The grafting of the PEG molecules is optimized for either type of μFN: the networks from PDMS and silicon are derivatized using PEG-silanes and the Au-coated networks are derivatized with a thiolated PEG. Additionally, the zones of the Au-covered Si μFNs separating the channels are selectively covered with a hydrophobic thiol using microcontact printing. X-ray photoelectron spectroscopy and contact angle measurements indicate that all grafted layers have the expected chemical composition and are thin, homogeneous, and hydrophilic where desired. Finally, using fluorescently labeled antibodies we show that these μFNs are more effective for patterning, with high positional accuracy and edge resolution on PDMS substrates, than conventional O2-plasma-treated μFNs made from PDMS. Overall, our approach should help in making and using μFNs made from different materials but having similar surface properties.

Surface treatment and characterization: Perspectives to electrophoresis and lab‐on‐chips

“…The chemical modification of microchip surfaces with SAMs was already used to prevent or minimize the deposition of proteins onto the channels [45]. Surfaces bearing oxides are well-known to be of potential interest for chemical modification with silanes.…”

“…Surfaces bearing oxides are well-known to be of potential interest for chemical modification with silanes. Alternately, silanes have already been grafted onto plastic and elastomeric microchannels [45][46][47].…”

The effects of proteoglycan surface patterning on neuronal pathfinding

“…After the adsorption process, the stamp is removed and can be reused for other substrates. Microfluidic patterning provides an advantage over μCP for proteins that do not retain biological activity through the stamping process [112][113][114]. A few investigators have combined μCP and (μFN to simultaneously or sequentially pattern segregated and overlapping fields of different proteins to a single substrate [115,116].…”

“…The patterning techniques including protein film UVor laser ablation [140,141], nitrocellulose paper strip protein transfer [142], microfluidic networks [112,113,143], and microcontact printing [76] have been utilized to produce such substrates. Of interest are studies in which these techniques have been used to generate concentration gradients and protein field boundaries to discover how bound factor density and spatial distrubition affect cell behavior.…”

Surface modification in microchip electrophoresis

“…The main focus is on the improvement of electrophoretic separations by the reduction of analyte-wall interactions and the manipulation of electroosmosis. Approaches for surface derivatization of microfluidic chips in order to introduce additional functionality such as immunoassays [33][34][35][36], stationary phases for electrochromatography [37][38][39][40] and immobilized reagents [41] and enzymes [42,43] will not be discussed in detail.…”