Dynamic coating of SU‐8 microfluidic chips with phospholipid disks

Abstract

In this work, PEG-stabilized phosphatidylcholine lipid aggregates (disks), mimicking mammalian cell membranes, were introduced as a new biofouling resistant coating for SU-8 polymer microchannels. A rapid and simple method was developed for immobilization of PEGylated phosphatidylcholine disks in microchannels. Microfluidic chips made from SU-8, PDMS, or glass were dynamically coated with the PEGylated disks followed by characterization of their surface chemistry before and after coating. On the basis of the observed changes in EOF and nonspecific protein adsorption, the affinity of the PEGylated disks was shown to be particularly strong toward SU-8. The PEG-lipid coating enabled permanent change in EOF in SU-8 microchannels with an initial value of 4.5 x 10(-8) m(2) V(-1) s(-1), decreasing to 2.1 x 10(-8) m(2) V(-1) s(-1) (immediately after modification), and, eventually, to 1.5 x 10(-8) m(2) V(-1) s(-1) (7 days after modification) for 9 mM sodium borate (pH 10.5) as BGE. As determined by the Wilhelmy plate measurements and microchip-CE analysis of BSA, the PEG-lipid coating also enabled efficient biofouling shield against protein adsorption, similar to that of low amounts of SDS (3.5 mM) or Tween-20 (80 microM) as buffer additives. These results suggest that dynamically attached PEG-lipid aggregates provide stable, biomimicking surface modification that efficiently reduces biofouling on SU-8.

Development of an SDS‐gel electrophoresis method on SU‐8 microchips for protein separation with LIF detection: Application to the analysis of whey proteins

“…Using this concentration of EOTrol LN, the EOF mobility of SU‐8 microchips was reduced four times reaching a value of 4.1 × 10 −5 cm 2 V −1 s −1 . This compares favorably with the value reported by Sikanen et al who obtained a decrease of two times on the EOF value of SU‐8 microchips with a dynamic coating consisting on phospholipids disks. It has also to be noted, that the EOF of the native SU‐8 polymer reported in that work was 4.5 × 10 −4 cm 2 V −1 s −1 in a buffer different to ours (9 mM borate, pH 9).…”

Isolation of cells for selective treatment and analysis using a magnetic microfluidic chip

“…In order to prevent non-specific binding and cell adhesion to the walls of the PDMS structures and to the Au surface, the channels were first treated with 10 mg/ml BSA (Bovine serum albumin) and 0.1% (v/v) SDS (Sodium dodecyl sulfate) solution for 15 min. BSA is known to inhibit cell adhesion and efficiently prevent adsorption on the walls of PDMS channels, [52][53][54] whereas the ionic surfactant (SDS) prevents binding of SPBs or undesired waste to silicon and photoresist surfaces [55][56][57] like the MMC surface. This treatment also removes all dead cells or other small particles left from previous experiments.…”

Soft nanoparticles (thermo-responsive nanogels and bicelles) with biotechnological applications: from synthesis to simulation through colloidal characterization

“…Nevertheless, capillary electrophoresis measurements have been performed for suspensions of liposomes [153][154][155] and, more scarcely, bicelles. [156][157][158] But the aim of these works was mainly the separation of bicelles by size and amount of charge in order to optimize methods for membrane partitioning. 154 Their electrophoretic mobility was analyzed using old colloidal models and without including further developments.…”

“…In general, z-potential is hardly used in these reports. [153][154][155][156][157][158] On the contrary, colloidal properties such as shape and size, and the internal structure of bicelles have been investigated directly linked to the most studied behavior of bicelles, the orientation in the presence of magnetic fields due to its diamagnetic character. Thus, NMR techniques have been widely used for the characterization of bicelles.…”