Jerry Elkind

A commercial solution for surface plasmon sensing

A novel, fully integrated surface plasmon resonance (SPR) transducer is described which is based on the encapsulation of the required electro-optical components within the optical material, through a molding process. Prototype sensors based on this approach have been successfully fabricated and tested. Results are shown for sensing of refractive index variations in alcohol solutions. Additionally, the SPR transducer is shown to function as a biological sensor.

Detection of Staphylococcus aureus enterotoxin B at femtomolar levels with a miniature integrated two-channel surface plasmon resonance (SPR) sensor

Surface plasmon resonance (SPR) biosensors offer the capability for continuous real-time monitoring. The commercial instruments available have been large in size, expensive, and not amenable to field applications. We report here an SPR sensor system based on a prototype two-channel system similar to the single channel Spreeta devices. This system is an ideal candidate for field use. The two-channel design provides a reference channel to compensate for bulk refractive index (RI), non-specific binding and temperature variations. The SPR software includes a calibration function that normalizes the response from both channels, thus enabling accurate referencing. In addition, a temperature-controlled enclosure utilizing a thermo-electric module based on the Peltier effect provides the temperature stability necessary for accurate measurements of RI. The complete SPR sensor system can be powered by a 12V battery. Pre-functionalized, disposable, gold-coated thin glass slides provide easily renewable sensor elements for the system. Staphylococcus aureus enterotoxin B (SEB), a small protein toxin was directly detectable at sub-nanomolar levels and with amplification at femtomolar levels. A regeneration procedure for the sensor surface allowed for over 60 direct detection cycles in a 1-month period.

A portable surface plasmon resonance (SPR) sensor system with temperature regulation

We describe here the construction of an inexpensive portable, temperature-regulated surface plasmon resonance (SPR) instrument utilizing readily available components. This system is ideal for both laboratory and field use. Applications of SPR-based biosensors range from laboratory assays to continuous or spot monitoring for analytes important in food industries to monitoring for environmental pollutants and agents of bioterrorism. SPR sensors are capable of measuring minute changes in refractive index (RI) to high precision. Changes in temperature affect the materials of the SPR sensor and RI of aqueous sample solutions. Management of the effects of temperature changes on the SPR signal can be achieved by temperature stabilization, compensation, or a combination of both. The multi-channel design described here allows for a reference channel to compensate for bulk RI changes, non-specific binding, and minor temperature variations, while the temperature controller provides the temperature stability necessary for monitoring small changes in RI. The temperature controller also allows for studies of the temperature dependence of molecular interactions and for optimizing detection conditions.

Construction of biosensors using a gold-binding polypeptide and a miniature integrated surface plasmon resonance sensor

Surface plasmon resonance (SPR) biosensors were constructed on miniature integrated sensors. Recognition elements were attached to the sensor surface using a gold-binding repeating polypeptide. Biosensors with fluorescyl groups attached to their surfaces were functional for at least 1 month of daily use with little decrease in response to the binding of an anti-fluorescyl monoclonal antibody. The coupling of protein A to the gold-binding polypeptide on the sensor surface enabled the biosensor to detect the binding of antibodies to the protein A and provided a sensor with convertible specificity. The system described herein provides a simple and rapid approach for the fabrication of highly specific, durable, portable and low cost SPR-based biosensors.

Integrated analytical sensors: the use of the TISPR-1 as a biosensor

Abstract The TISPR-1 integrated surface plasmon resonance (SPR) sensor has features that make it ideal for use in a distributed sensor environment. This sensor, combined with simple bio-films, is shown to be capable of a wide variety of bio-assays. Data for a direct-binding assay for creatine kinase MB (CK-MB), for a displacement assay for dinitrophenol-glycine (DNP-GLY) and a competition assay for trinitrotoluene (TNT) are presented. Also, current and projected TISPR-1 sensor system limits of detection are discussed.

Characterization of oxidoreductase-redox polymer electrostatic film assembly on gold by surface plasmon resonance spectroscopy and Fourier transform infrared-external reflection spectroscopy

The electrostatic assembly of nanocomposite thin films consisting of alternating layers of an organometallic redox polymer (RP) and oxidoreductase enzymes, glucose oxidase (GOX), lactate oxidase (LOX) and pyruvate oxidase (PYX), was investigated. Multilayer nanostructures were fabricated on gold surfaces by the deposition of an anionic self-assembled monolayer of 11-mercaptoundecanoic acid, followed by the electrostatic attachment of a cationic RP, poly(vinylpyridine Os(bis-bipyridine)2Cl-co-allylamine) (PVP-Os-AA), and anionic oxidoreductase enzymes. Surface plasmon resonance (SPR) spectroscopy, Fourier transform infrared external reflection spectroscopy (FT-IR–ERS) and electrochemistry were employed to characterize the assembly of these nanocomposite films. The surface concentration of GOX was found to be 2.4 ng/mm 2 for the first enzyme layer and 1.96 ng/mm 2 for the second enzyme layer, while values of 10.7 and 1.3 ng/mm 2 were obtained for PYX and LOX, respectively. The apparent affinity constant for GOX adsorption was found to be 8 × 10 7 M −1 . FT-IR–ERS was used to verify the incorporation of GOX and its conformational stability inside of these nanocomposite thin films. An SPR instrument with a flow-through cell was modified by additions of Ag/AgCl reference and Pt counter electrodes, with the gold-coated SPR surface film serving as the working electrode. This enabled real-time observation of the assembly of sensing components and immediate, in situ electrochemical verification of substrate-dependent current upon the addition of enzyme to the multilayer structure. A glucose-dependant amperometric response with sensitivity of 0.197 A/cm 2 /mM for a linear range of 1–10 mM of glucose was obtained. The SPR and FT-IR–ERS studies also showed no desorption of polymer or enzyme from the nanocomposite RP–GOX structure when stored in aqueous environment occurred over the period of 3 weeks, suggesting that decreasing substrate sensitivity with time was due to loss of enzymatic activity rather than loss of film compounds from the nanostructure.