Photochemical linkage of antibodies to silicon chips

Diagnostic devices as biomaterials: a review of nucleic acid and protein microarray surface performance issues

This review of current DNA and protein microarray diagnostic and bio-analytical technologies focuses on the different surface chemistries used in these miniaturized surface-capture formats. Description of current strategies in bio-immobilization and coupling to create multiplexed affinity bioassays in micrometer-sized printed spots, problems with current formats and review of some detection methods are included. Recommendations for improving long-standing challenges in DNA- and protein-based arrays are forwarded. The biomaterials community can contribute relevant expertise to these formidable bio-interfacial problems that represent significant barriers to clinical implementation of microarray assays.

Integrated nanoparticle-biomolecule hybrid systems: synthesis, properties, and applications

Nanomaterials, such as metal or semiconductor nanoparticles and nanorods, exhibit similar dimensions to those of biomolecules, such as proteins (enzymes, antigens, antibodies) or DNA. The integration of nanoparticles, which exhibit unique electronic, photonic, and catalytic properties, with biomaterials, which display unique recognition, catalytic, and inhibition properties, yields novel hybrid nanobiomaterials of synergetic properties and functions. This review describes recent advances in the synthesis of biomolecule-nanoparticle/nanorod hybrid systems and the application of such assemblies in the generation of 2D and 3D ordered structures in solutions and on surfaces. Particular emphasis is directed to the use of biomolecule-nanoparticle (metallic or semiconductive) assemblies for bioanalytical applications and for the fabrication of bioelectronic devices.

Photochemical immobilization of proteins on microwave–synthesized photoreactive polymers

We report a rapid and versatile procedure for the preparation of photoreactive polymers and light-induced immobilization of proteins onto such polymers. Photoreactive controlled-pore glass, silica gel, glass slide, and polystyrene microtiter plate are prepared in 40-60s by microwave irradiation of the respective amino polymers and 1-fluoro-2-nitro-4-azidobenzene. Azido group, now part of the polymer, yields highly reactive nitrene under ultraviolet (UV) light at 365 nm. Thus, when photoreactive polymer and horseradish peroxidase or glucose oxidase are exposed to UV light, the reactive nitrene immobilizes the protein molecules in 10 to 20 min through covalent bonding. As nitrene has a property of inserting into C-H bond, the method may find potential applications for immobilization of biomolecules irrespective of their functional groups.

Light activated patterning of dye-labeled molecules on surfaces

This Communication describes a novel method for patterning proteins, ligands, or other organic/inorganic species onto solid substrates. The process works by linking the moiety of interest to a fluorophore that can be subsequently photobleached and bound to the interface. The technique can be performed in aqueous solution and allows several species to be addressed onto the surface simultaneously by using different frequencies of light. Because the method can be used with fluorophores excited by visible light, shorter and more damaging wavelengths can be avoided.

Biochips beyond DNA: technologies and applications

Technological advances in miniaturization have found a niche in biology and signal the beginning of a new revolution. Most of the attention and advances have been made with DNA chips yet a lot of progress is being made in the use of other biomolecules and cells. A variety of reviews have covered only different aspects and technologies but leading to the shared terminology of "biochips." This review provides a basic introduction and an in-depth survey of the different technologies and applications involving the use of non-DNA molecules such as proteins and cells. The review focuses on microarrays and microfluidics, but also describes some cellular systems (studies involving patterning and sensor chips) and nanotechnology. The principles of each technology including parameters involved in biochip design and operation are outlined. A discussion of the different biological and biomedical applications illustrates the significance of biochips in biotechnology.

Mediated electrochemical detection of catechol by tyrosinase-based poly(dicarbazole) electrodes

A new dicarbazole derivative functionalised by an N-hydroxysuccinimide group has been synthesised and electrochemically characterised. Upon oxidative electropolymerisation of this monomer in organic electrolytes, electroactive poly(dicarbazole) films were formed on platinum electrodes. The subsequent chemical grafting of tyrosinase on the poly(dicarbazole) film was easily performed by immersion in an enzymatic aqueous solution. The amperometric response of the resulting biosensors to catechol has been studied at -0.2 V vs. saturated calomel electrode (SCE). Since the reduction of quinone generates radicals which may induce electrode fouling, thionine, a phenothiazine dye, was covalently bound to the poly(dicarbazole) backbone as it mediates the reduction of quinoid products and therefore induces an enhancement of the performance of the tyrosinase-based biosensor.

The solid phase in affinity chromatography: strategies for antibody attachment

Antibodies (Ab) are commonly used in affinity chromatography (AC) as a versatile and specific means of isolating target molecules from complex mixtures. A number of procedures have been developed to immobilize antibodies on the solid matrix. Some of these methods couple the antibody via chemical groups that may be important for specific recognition of antigen, resulting in loss of functionality in a proportion of the antibodies. In other methods, the outcome of immobilization is coupling via unique sites in the Fc region of the antibody molecule, ensuring orientation of the antibody combining sites (Fab) towards the mobile phase. This review discusses the advantages and disadvantages of the various methods available for immobilization and outlines protocols for site-directed, covalent coupling of the antibody to the solid phase that essentially retains the activity of the antibody.

Patterning and characterization of surfaces with organic and biological molecules by the scanning electrochemical microscope

A novel approach for micropatterning of surfaces with organic and biological microstructures using the scanning electrochemical microscope (SECM) is described. The approach is based on the introduction of the spatial resolution by local deposition of gold particles followed by monolayer formation and functionalization. Specifically, gold patterns were deposited locally on silicon wafers with the SECM as a result of the controlled anodic dissolution of a gold microelectrode. The gold patterns were further used as microsubstrates for assembling cystamine monolayers to which either fluoresceine isothiocyanate (FIT) or glucose oxidase (GOD) were covalently attached. Characterization of the organic monolayers, as well as the biological activity of the enzyme patterns, was carried out by fluorescence microscopy and the SECM, respectively.

Patterning of immobilized antibody layers via photolithography and oxygen plasma exposure

A novel technique for patterning immobilized antibody layers based upon photolithography and oxygen plasma exposure has been developed. Mouse monoclonal antibodies specific for thiabendazole (a post-harvest fungicide and veterinary anthelmintic) were covalently linked through free amine groups to aminosilanized silicon dioxide films using glutaraldehyde. Immobilized antibody layers were stabilized with sucrose, dehydrated, and stored refrigerated with desiccant. Photolithographic patterning was performed with a positive photoresist with modified bake temperatures and times, selective UV exposure with a contact mask, and aqueous alkaline solubilization of exposed resist. Exposed regions of immobilized antibody were then removed by exposure to a low power, radio frequency oxygen discharge. Residual resist was stripped with acetone. Successful patterning was demonstrated by challenging surfaces with goat anti-mouse antibody conjugated to tetramethylrhodamine isothiocyanate. Sucrose stabilization was necessary for antibody to undergo photoresist processing without loss of binding activity. Challenge with enzyme linked antigen of oxygen plasma exposed antibody layers demonstrated that plasma treatment completely neutralized antibody capture ability. Ellipsometry measurements of oxygen plasma exposed antibody layers indicated complete removal of immobilized antibodies. Fluorescent imaging demonstrated smallest line widths of 2-3 microns.