ABSTRACT
We describe a method of amplifying the biosensing signal in surface plasmon resonance (SPR)-based immunoassays using an antibody-carbon nanotube (CNT) conjugate. As a model system, human erythropoietin (EPO) and human granulocyte macrophage colony-stimulating factor (GM-CSF) were detected by sandwich-type immunoassays using an SPR biosensor. For the amplification of the SPR signal, the CNT was conjugated with a polyclonal antibody, and then the conjugates were reacted with antibodies coupled with the target proteins. This amplification strategy increases the dynamic range of the immunoassays and enhances the detection sensitivity. The SPR immunoassays, combined with the CNT-assisted signal amplification method, provided a wide dynamic range over four orders of magnitude for both EPO and GM-CSF (0.1-1,000 ng/ml). The CNT amplification method is expected to realize the detection of picogram levels and a wide dynamic detection range of multiple proteins, enabling it to offer a robust analysis tool for the development of biopharmaceutical production.
Subject(s)
Erythropoietin/analysis , Granulocyte-Macrophage Colony-Stimulating Factor/analysis , Nanotubes, Carbon/chemistry , Surface Plasmon Resonance/methods , Antibodies/immunology , Biosensing Techniques/methods , Erythropoietin/genetics , Erythropoietin/metabolism , Granulocyte-Macrophage Colony-Stimulating Factor/genetics , Granulocyte-Macrophage Colony-Stimulating Factor/metabolism , Humans , Immunoassay/methods , Recombinant Proteins/analysis , Recombinant Proteins/genetics , Recombinant Proteins/metabolismABSTRACT
We report a fabrication method for a gradient refractive-index polymeric object from a binary comonomer system, regardless of the monomers' reactivity ratio and the molar volume criteria of gradient refractive-index development. To fabricate a large gradient refractive-index rod consisting of a methyl methacrylate and 2,2,3,3-tetrafluoropropyl methacrylate comonomer pair that has not been used for fabrication of a copolymer gradient refractive-index rod by previous conventional methods because of chemical restrictions in molar volume and reactivity ratio difference, we use the so-called successive UV polymerization in a controlled radial volume in conjunction with an automatic refill reactor. Simultaneously and automatically, the volume shrinkage problem, an inevitable shortcoming for the fabrication of a large polymeric object in a commercial production scale, is overcome and exploited. The theoretical features of the refractive-index profile generation of this method are also compared with those of conventional methods for which the chemical restrictions of monomers are crucial for the shape of a refractive-index profile.
