Physisorbed surface coatings for poly(dimethylsiloxane) and quartz microfluidic devices

Abstract

Surface modifications of microfluidic devices are of essential importance for successful bioanalytical applications. Here, we investigate three different coatings for quartz and poly(dimethylsiloxane) (PDMS) surfaces. We employed a triblock copolymer with trade name F108, poly (l-lysine)-g-poly(ethylene glycol) (PLL-PEG), as well as the hybrid coating n-dodecyl-β-d-maltoside and methyl cellulose (DDM/MC). The impact of these coatings was characterized by measuring the electroosmotic flow (EOF), contact angle, and prevention of protein adsorption. Furthermore, we investigated the influence of static coatings, i.e., the incubation with the coating agent prior to measurements, and dynamic coatings, where the coating agent was present during the measurement. We found that all coatings on PDMS as well as quartz reduced EOF, increased reproducibility of EOF, reduced protein adsorption, and improved the wettability of the surfaces. Among the coating strategies tested, the dynamic coatings with DDM/MC and F108 demonstrated maximal reduction of EOF and protein adsorption and simultaneously best long-term stability concerning EOF. For PLL-PEG, a reversal in the EOF direction was observed. Interestingly, the static surface coating strategy with F108 proved to be as effective to prevent protein adsorption as dynamic coating with this block copolymer. These findings will allow optimized parameter choices for coating strategies on PDMS and quartz microfluidic devices in which control of EOF and reduced biofouling are indispensable.

Tuning direct current streaming dielectrophoresis of proteins

“…Under our experimental conditions, we observed cathodic EOF (Ref. 64). Assuming that l eo found previously for PDMS/glass channels 62 is in the same order of magnitude (10 À8 m 2 /Vs) as l ep for proteins, 65 two scenarios are possible.…”

“…The simulation was conducted using a l dep value of À1.28 Â 10 À23 m 4 /V 2 s calculated based on the size of the spherical micelle-IgG complex measured by DLS, as well as l eo of 0.14 Â 10 À8 m 2 /Vs for F108 dynamic coated PDMS channels. 64 We note that the here employed numerical model for DC conditions does not capture the contribution of the double-layer to the protein polarizability in detail. 44,46 We can, however, speculate that the contribution of double-layer polarization and a decrease in the zeta potential due to the polyethylene glycol chains of F108 forming the micelles results in FIG.…”

“…62 Recently, we could also demonstrate that dynamic coating, in which the coating agent is apparent in the buffer throughout the entire experiment is able to reduce EOF even further. 64 Hence, we employed this dynamic coating procedure with 3 mM F108 as final concentration in the buffer and studied its effect on streaming DEP of IgG.…”

Silicones for Microfluidic Systems

“…Nevertheless, dynamic replenishment of surface-active molecules occurs continuously from the excess of surfactant in the running buff er and desorption does not negatively impact the overall result. • Adsorption of charged polymers (polyelectrolytes [68,69] or zwitterionic polymers [70]) and layer-bylayer (LBL) technique, using alternating multilayers of electrostatically assembled polyanions and polycations (PEMs) [71][72][73] onto activated (negatively charged) PDMS surface. • Non-specifi c adsorption of proteins as surface modifi ers [74].…”

Mitigated reactive oxygen species generation leads to an improvement of cell proliferation on poly[glycidyl methacrylate‐co‐poly(ethylene glycol) methacrylate] functionalized polydimethylsiloxane surfaces

“…14,15 Apart from successful application in microdevice for protein analysis, it has been increasingly utilized for constructing cell analyzer. 16,17 However, PDMS is not ideal for cell adhesion owing to an energy barrier between it and cell growth medium. Consequently, tailoring of physical or chemical properties of PDMS to enhance cell adhesion and growth is a key factor for the development of PDMS-based miniaturized cell assay analytical devices.…”