Study on surface properties of PDMS microfluidic chips treated with albumin

Abstract

Electrokinetic properties and morphology of PDMS microfluidic chips intended for bioassays are studied. The chips are fabricated by a casting method followed by polymerization bonding. Microchannels are coated with 1% solution of bovine serum albumin ͑BSA͒ in Tris buffer. Albumin passively adsorbs on the PDMS surface. Electrokinetic characteristics ͑electro-osmotic velocity, electro-osmotic mobility, and zeta potential͒ of the coated PDMS channels are experimentally determined as functions of the electric field strength and the characteristic electrolyte concentration. Atomic force microscopy ͑AFM͒ analysis of the surface reveals a "peak and ridge" structure of the protein layer and an imperfect substrate coating. On the basis of the AFM observation, several topologies of the BSA-PDMS surface are proposed. A nonslip mathematical model of the electro-osmotic flow is then numerically analyzed. It is found that the electrokinetic characteristics computed for a channel with the homogeneous distribution of a fixed electric charge do not fit the experimental data. Heterogeneous distribution of the fixed electric charge and the surface roughness is thus taken into account. When a flat PDMS surface with electric charge heterogeneities is considered, the numerical results are in very good agreement with our experimental data. An optimization analysis finally allowed the determination of the surface concentration of the electric charge and the degree of the PDMS surface coating. The obtained findings can be important for correct prediction and possibly for robust control of behavior of electrically driven PDMS microfluidic chips. The proposed method of the electro-osmotic flow analysis at surfaces with a heterogeneous distribution of the surface electric charge can also be exploited in the interpretation of experimental studies dealing with protein-solid phase interactions or substrate coatings.

Integrated automated particle tracking microfluidic enables high‐throughput cell deformability cytometry for red cell disorders

“…The mixture was drawn into a 1 mL syringe (Becton Dickinson, Franklin Lakes, New Jersey) with microfluidic tubing attached. A 20 mg mL −1 solution of BSA in PBS was injected to perfuse through and block the microfluidic network to prevent nonspecific adhesion of RBCs to the microfluidic channel walls . The BSA solution was allowed to incubate within the device for >30 minutes at room temperature (22°C).…”

Modeling colloid deposition on a protein layer adsorbed to iron-oxide-coated sand

“…Consequently, morphological models of BSA needs simplification to certain degrees: it is described either as a globular ellipsoid of about 14 x 3.8 x 3.8 nm (Ke et al, 2009;Togashi et al, 2009), a heart-shaped solid with three different domains (Voros, 2004), or a flexible foldable polymer (Chiku et al, 2008). Among them, the ellipsoid model not only provides explicit size and geometry description of the protein molecule, but also offers a realistic means to characterise the adsorbed conformation in end-on (long axis perpendicular to collector surface) or side-on (short axis perpendicular to collector surface) (Yoon et al, 2003;Schrott et al, 2009). This renders the globular ellipsoid model well suited for this study.…”

Parallel single‐cell analysis microfluidic platform

“…This variation is attributed to two factors: on one hand, the structure sizes in PDMS remain subject to variations, and, on the other hand, the surface properties are ill-defined [36] especially when an anti-sticking coating is applied [37]. In the future, another material will be employed that provides reliable and reproducible structure sizes (e.g., a rigid material) and well-defined surface properties.…”