Surface-functionalization of isotactic polypropylene via dip-coating with a methacrylate-based terpolymer containing perfluoroalkyl groups and poly(ethylene glycol)

Rewritable Surface on a Plastic Substrate Using Fluorous Affinity

Fluorous chemistry has unique features and high potential applicability, which are distinct from those of nonfluorinated organic compounds. However, there are limited reports detailing the applications of fluorous-fluorous interactions (fluorophilicity or fluorous affinity), likely because these interactions are not found in nature. In the present study, we describe the rewritable surface functionalization of a plastic substrate based on fluorous affinity. Plastic substrates were dip-coated with a series of methacrylate-based fluoropolymers to generate fluorous surfaces. Fluorous-tagged small molecules [perfluoroalkyl (Rf) amines] were immobilized on the fluorous surfaces via fluorous-fluorous interactions, thereby introducing reactive functional groups (amino moieties) on the surface. The amino groups displayed on the surface (accessible by a reactant) were successfully quantified using a reactive fluorophore, which enabled quantitative analysis of the Rf-amines immobilized on the fluorous surface that were available for the subsequent reaction. The effects of the molecular structures of the fluoropolymers and Rf-amines on the surface immobilization of Rf-amines were also investigated quantitatively. The surface coated with a fluoropolymer containing -C₈F₁₇ most effectively immobilized an Rf-amine comprising two -C₆F₁₃ chains. The adhered Rf-amines were easily removed by washing the surface with methanol, and then, they could successfully be re-immobilized on the surface. Finally, the presented approach enabled the rewritable micropatterning of an Rf-tagged biomolecule on a plastic surface through microcontact printing.

Covalent immobilization of gold nanoparticles on a plastic substrate and subsequent immobilization of biomolecules

We propose a novel approach to stably immobilize gold nanoparticles (AuNPs) on a plastic substrate and demonstrate that the modified substrate is also capable of immobilizing biomolecules. To immobilize citrate-capped AuNPs, an acrylic substrate was simply dip-coated in a functional polymer solution to decorate the outermost surface with amino groups. Electrostatic interactions between AuNPs and the amino groups immobilized the AuNPs with a high density. The AuNP-modified acrylic substrate was transparent with a red tint. A heat treatment promoted the formation of amide bonds between carboxy groups on the AuNPs and amino groups on the substrate surface. These covalent bonds stabilized the immobilized AuNPs and the resulting substrate was resistant to washing with acid and thiol-containing solutions. The surface density of AuNPs was controlled by the surface density of amino groups on the substrate surface, which was in turn controlled by the dip-coating in the functional polymer solution. We attempted to immobilize functional biomolecules on the AuNPs-functionalized plastic surface by two different approaches. An enzyme (horseradish peroxidase) was successfully immobilized on the AuNPs through amide formation and 5′-thiolated DNA was also immobilized on the AuNPs through S–Au interactions. These chemistries allow for simultaneous immobilization of two different kinds of biomolecules on a plastic substrate without loss of their functional properties.

We propose a novel approach to stably immobilize gold nanoparticles (AuNPs) on a plastic substrate and demonstrate that the modified substrate is also capable of immobilizing biomolecules.

Design of a Bioinert Interface Using an Amphiphilic Block Copolymer Containing a Bottlebrush Unit of Oligo(oxazoline)

We designed an amphiphilic block copolymer, poly(methyl methacrylate)-block-poly[oligo(2-ethyl-2-oxazoline) methacrylate] (PMMA-b-P[O(Ox)MA]), suitable for bioinert coating. Angular-dependent X-ray photoelectron spectroscopy and neutron reflectivity measurements revealed that the outermost surface of a dried film of PMMA-b-P[O(Ox)MA] was covered with the PMMA block-rich layer. Once the film came into contact with water, the P[O(Ox)MA] bottlebrush block was segregated toward the water interface. This structural rearrangement in the outermost region of the film resulted in the formation of the swollen oligo(oxazoline) layer with excellent bioinertness in terms of the suppression of serum protein adsorption and NIH3T3 fibroblast adhesion.

One-Step Biotinylation of Cellulose Paper by Polymer Coating to Prepare a Paper-Based Analytical Device

Cellulose paper has strong potential as an analytical platform owing to its unique characteristics. In the present study, we investigated a procedure for functionalizing the surface of cellulose paper by dip-coating a mixture of a functional polymer and a perfluoroalkylated surfactant (surfactant 1). The functional polymer comprised a mixture of methyl methacrylate and poly(ethylene glycol) methacrylate monomers. The monomer ratio in the functional polymer affected the hydrophilicity and water absorbance of the cellulose paper after dip-coating. Furthermore, the presence of surfactant 1 during dip-coating promoted the surface segregation of poly(ethylene glycol) (PEG) moieties in the polymer, which enhanced the hydrophilicity, prevented nonspecific protein adsorption, and maintained the water absorbance of the dip-coated cellulose paper. Dip-coating with another functional polymer containing biotin groups produced a cellulose paper with a biotin-decorated surface in a one-step procedure. The displayed biotin groups immobilized avidin on the surface, and the PEG moieties in the polymer prevented nonspecific protein adsorption. We then immobilized a thrombin-binding DNA aptamer on the avidin-immobilized cellulose paper to prepare a paper-based analytical device. It is possible to visualize thrombin in model solutions and serum using the paper-based analytical device.