Patternable Protein Resistant Surfaces for Multifunctional Microfluidic Devices via Surface Hydrophilization of Porous Polymer Monoliths Using Photografting

Abstract

Surface-modified macroporous polymer monoliths that resist the adsorption of proteins have been prepared using both single-and two-step photografting of hydrophilic monomers. The adsorption of protein was measured using a fluorescence assay based on bovine serum albumin labeled with fluorescein. Acrylamide, 2-hydroxyethyl methacrylate, vinyl pyrrolidinone, and poly(ethylene glycol) methacrylate (PEGMA) monomers were grafted and evaluated for their ability to prevent protein adsorption. Photografted layers of PEGMA reduced protein adsorption to less than 2% relative to unmodified surfaces. The sequential two-step photografting process consisted in (i) the formation of covalently bound surface photoinitiator sites followed by (ii) surface-localized graft polymerization. Monomer concentration and irradiation time during photografting were found to be the most important parameters for optimization of the two-step process. For simultaneous single-step photografting, the solvent and the presence of photoinitiator were the key variables. Initiator-free single-step photografting was less efficient than the two-step technique, yet resulted in similar prevention of protein adsorption after grafting for an extended period of time. The utility of photografting as a simple, patternable modification technique was demonstrated by first creating a hydrophilic surface within the monolith that was subsequently patterned with a layer of reactive 2-vinyl-4,4-dimethylazlactone polymer chains followed by the immobilization of green fluorescent protein.

Preparation of methacrylate monoliths

“…Stachowiak et al [116] have reported hydrophilization of macroporous poly(butyl methacrylate-co-ethylene dimethacrylate) monoliths using single-and two-step photografting with acrylamide, 2-hydroxyethyl methacrylate, vinyl pyrrolidinone, and poly(ethylene glycol) methacrylates. The single-step photografting was carried out using (i) a traditional approach, where the photografting solution contained both monomer and photoinitiator, and (ii) an initiator-free approach.…”

Monolithic porous polymer stationary phases in polyimide chips for the fast high-performance liquid chromatography separation of proteins and peptides

“…The morphology of the monolithic polymer is strongly affected by both the composition of the polymerization mixture and the conditions under which the polymerization process is carried out [21,28,29]. The different monoliths have thus been optimized for specific applications by tuning them with a wide range of functionalities [29,32,33], among which hydrophobic [27,28,34] hydrophilic [35], ionizable [28,34], and reactive [36,37] are the most frequently used.…”

Hydrophilic surface modification of cyclic olefin copolymer microfluidic chips using sequential photografting

“…However, for less permeable substrates, such as COC, initiator is not likely to absorb into the walls and desorption would be a greater concern. We recently utilized an alternative two-step technique for surface modification of high surface area macroporous monolithic polymers [29]. This approach involves the covalent attachment of photoinitiator to the polymer surface before monomer is introduced.…”