A photoimmobilizable sulfobetaine-based polymer for a nonbiofouling surface.

A novel photoreactive polymer containing sulfobetaine polar groups was prepared by copolymerization of two kinds of methacrylic acids with sulfobetaine and azidoaniline. The polymer was photoimmobilized on polyester and polystyrene surfaces. Its effects on surface modification were investigated from its interactions with water, proteins and cells. Polymer immobilization altered both of the plain surfaces to becoming hydrophilic in a similar range of static contact angles (12.5±1.6° on polyester and 14.7±2.2° on polystyrene). This suggests that the surfaces were covered with sulfobetaine polar groups. Micropattern immobilization was carried out on both polymers using a photomask. The formed pattern was identical to the photomask, showing that the polymer was formed in response to ultraviolet irradiation. Measurements using atomic force microscopy showed that the polymer was formed at a thickness of 550nm, demonstrating that the polymer was cross-linked with itself and with the substrate molecules. Measurements using time-of-flight secondary ion mass spectrometry detected an abundance of sulfur-containing ions in the patterned polymer, confirming that sulfobetaine had been immobilized. Protein adsorption and mammalian cell adhesiveness were reduced markedly on the immobilized regions. The reduction of cell adhesiveness was concentration-dependent for the immobilized polymer on polyester surfaces. In conclusion, a novel sulfobetaine-containing polymer was immobilized photoreactively on conventional polymer surfaces and significantly reduced interactions with proteins and mammalian cells.

Photo-immobilization of biological components on gold-coated chips for measurements using surface plasmon resonance (SPR) and a quartz crystal microbalance (QCM).

The photo-immobilization technique is useful for immobilization of various biomolecules on assorted material surfaces, independent of the organic functional groups that may be present. Here, we report a convenient new photo-immobilization technique that was developed by combining a nonbiofouling polymer containing polyethylene glycol and a photoreactive crosslinker for surface plasmon resonance (SPR) and quartz crystal microbalance (QCM) measurements. By this method, nonspecific interactions were reduced and various types of molecules, bovine serum albumin, heparin, dsDNA, phosphatidylserine, Tobacco Mosaic Virus, and norfloxacine, were immobilized on an alkane thiol-modified gold surface by a single method. The interactions of photo-immobilized biomolecules and their corresponding antibodies were investigated by SPR and QCM. In addition, SPR imaging was possible using the present method.

Automated microfluidic assay system for autoantibodies found in autoimmune diseases using a photoimmobilized autoantigen microarray.

Autoimmune diseases such as rheumatoid arthritis, multiple sclerosis, and autoimmune diabetes are characterized by the production of autoantibodies that serve as useful diagnostic markers, surrogate markers, and prognostic factors. We devised an in vitro system to detect these clinically pivotal autoantibodies using a photoimmobilized autoantigen microarray. Photoimmobilization was useful for preparing the autoantigen microarray, where autoantigens are covalently immobilized on a plate, because it does not require specific functional groups of the autoantigens and any organic material can be immobilized by a radical reaction induced by photoirradiation. Here, we prepared the microarray using a very convenient method. Aqueous solutions of each autoantigen were mixed with a polymer of poly(ethylene glycol) methacrylate and a photoreactive crosslinker, and the mixtures were microspotted on a plate and dried in air. Finally, the plate was irradiated with an ultraviolet lamp to obtain immobilization. In the assay, patient serum was added to the microarray plate. Antigen-specific IgG adsorbed on the microspotted autoantigen was detected by peroxidase-conjugated anti-IgG antibody. The chemical luminescence intensities of the substrate decomposed by the peroxidase were detected with a sensitive CCD camera. All autoantigens were immobilized stably by this method and used to screen antigen-specific IgG. In addition, the plate was covered with a polydimethylsiloxane sheet containing microchannels and automated measurement was carried out.

Copolymers including L-histidine and hydrophobic moiety for preparation of nonbiofouling surface.

A new type of copolymer composed of l-histidine (ampholyte) and n-butyl methacrylate (hydrophobic moiety) was developed for the preparation of nonbiofouling surfaces. The copolymer adsorbed onto resin surfaces and made the surface very hydrophilic. The hydrophilization effect was higher than that of bovine serum albumin (BSA). When polystyrene surfaces were coated with the copolymer, both the nonspecific adsorption of protein and the adhesion of cells were significantly reduced in comparison with BSA coating. The newly synthesized polymer is a new and useful candidate for the preparation of nonbiofouling surfaces.

Surface modification of plastic, glass and titanium by photoimmobilization of polyethylene glycol for antibiofouling.

Photoreactive poly(ethylene glycol) (PEG) was prepared and the polymer was photoimmobilized on organic, inorganic and metal surfaces to reduce their interaction with proteins and cells. The photoreactive PEG was synthesized by co-polymerization of methacrylate-PEG and acryloyl 4-azidobenzene. Surface modification was carried in the presence and the absence of a micropatterned photomask. It was then straightforward to confirm the immobilization using the micropatterning. Using the micropatterning method, immobilization of the photoreactive PEG on plastic (Thermanox), glass and titanium was confirmed by time-of-flight secondary ion mass spectroscopy and atomic force microscopy observations. The contact angle on an unpatterned surface was measured. Although the original surfaces have different contact angles, the contact angle on PEG-immobilized surfaces was the same on all surfaces. This result demonstrated that the surface was completely covered with PEG by the photoimmobilization. To assess non-specific protein adsorption on the micropatterned surface, horseradish peroxidase (HRP)-conjugated proteins were adsorbed. Reduced protein adsorption was confirmed by vanishingly small staining of HRP substrates on the immobilized regions. COS-7 cells were cultured on the micropatterned surface. The cells did not adhere to the PEG-coated regions. In conclusion, photoreactive PEG was immobilized on various surfaces and tended to reduce interactions with proteins and cells.