J. P. Alarie

Antibody-based nanoprobe for measurement of a fluorescent analyte in a single cell

We report here the application of an antibody-based nanoprobe for in situ measurements of a single cell. The nanoprobe employs antibody-based receptors targeted to a fluorescent analyte, benzopyrene tetrol (BPT), a metabolite of the carcinogen benzo[a]pyrene (BaP) and of the BaP–DNA adduct. Detection of BPT is of great biomedical interest, since this species can serve as a biomarker for monitoring DNA damage due to BaP exposure and for possible precancer diagnosis. The measurements were performed on the rat liver epithelial clone 9 cell line, which was used as the model cell system. Before making measurements, the cells were treated with BPT. Nanoprobes were inserted into individual cells, incubated 5 min to allow antigen–antibody binding, and then removed for fluorescence detection. We determined a concentration of 9.6 ± 0.2 × 10−11 M for BPT in the individual cells investigated. The results demonstrate the possibility of in situ measurements inside a single cell using an antibody-based nanoprobe.

SURFACE-ENHANCED RAMAN DETECTION OF NERVE AGENT SIMULANT (DMMP AND DIMP) VAPOR ON ELECTROCHEMICALLY PREPARED SILVER OXIDE SUBSTRATES

Surface-enhanced Raman scattering (SERS) spectra of the chemical nerve agent simulants dimethyl methylphosphonate (DMMP) and diisopropyl methylphosphonate (DIMP) were obtained in the vapor phase. The spectra obtained demonstrate the possibility of detecting these nerve agent species in the vapor phase using electrochemically roughened silver oxide substrates prepared from silver foil.

Intensified Charge Coupled Device-Based Fiber-Optic Monitor for Rapid Remote Surface-Enhanced Raman Scattering Sensing:

This paper describes the development of an intensified charge coupled device (ICCD)-based fiber-optic monitor for remote Raman and surface-enhanced Raman (SERS) sensing. Both Raman and SERS data were obtained with the use of a fiber-optic probe design incorporating 20-m optical fibers carrying the Raman signal. Spectra were obtained in 5 milliseconds for Raman and 9 ms for SERS. The proposed system could be used for a highly sensitive portable Raman system for rapid and remote chemical sensing.

Phase-Resolved Fiber-Optics Fluoroimmunosensor

This paper describes the development and application of a phase-resolved fiber-optics fluoroimmunosensor (PR-FIS), which combines the biochemical specificity of antigen-antibody reaction, the high sensitivity of laser excitation, the versatility of fiber-optics sensors, and the selectivity of phase-resolved detection. The PR-FIS device can differentiate benzo(a)pyrene and benzo(a)pyrene tetrol, a DNA-adduct product of the carcinogen benzo(a)pyrene. Benzo(a)pyrene tetrol can be detected at femtomole levels in the presence of an amount of interfacing benzo(a)pyrene that is 50-fold more concentrated.

A fiber-optic cyclodextrin-based sensor.

This paper describes the development of a fiber-optic cyclodextrin-based (FCD) sensor. The device uses laser excitation and fluorescence detection with beta-cyclodextrin as the reagent phase, immobilized at the tip of an optical fiber. The sensitivity of the FCD sensor is 14 times as great as that of a bare optical fiber when measurements are made with the fiber immersed in a buffer after a 10-min incubation period. The selectivity of the sensor is illustrated with pyrene as the model compound and 5,6-benzoquinoline as the interferent. An interference study with a contaminated environmental ground water sample is used to illustrate the usefulness of the FCD device.

Synthesis and characterization of SERS gene probe for BRCA-1 (breast cancer)

A protocol for binding cresyl fast violet (CFV), a SERS-active dye (label) containing an aromatic amino group with a modified oligomer having a carboxy derivatized thymidine moiety using carbodiimide coupling has been achieved for the first time. Covalent coupling between CFV and the oligomer has been confirmed by mass spectral analysis of the labeled oligomer. The fluorescence, SERS and absorption characteristics of the labeled product have been evaluated. The chosen oligomer contains a BRCA-1 (breast cancer) sequence, and hence has the potential for being used as a gene probe to identify BRCA-1 gene. It has high potential for being used in polymerase chain reaction (PCR) amplification, as has been performed with labeled oligonucleotide for the HIV sequence.

Development of a room-temperature phosphorescence fiber-optic sensor

The design of a new fiber-optic sensor based on solid-surface room-temperature phosphorimetry is presented for the analyses of polycyclic aromatic hydrocarbons in water samples. Analytical figures of merit are given for several compounds of environmental importance. Limits of detection at the nanograms per milliliter level were estimated for pyrene, benzo[e]pyrene, benzo[ghi]perylene, 1,2:3,4-dibenzanthracene, coronene, and 2,3-benzofluorene. The linearity of response of the phosphorescence sensor was evaluated, showing a fairly linear behavior for quantitative analysis. Finally, the feasibility of monitoring polycyclic aromatic hydrocarbons in aqueous media was illustrated by identifying pyrene in a contaminated groundwater sample.

Antibody-based biosensor for breast cancer with ultrasonic regeneration

We describe a novel method and instrumental setup for regenerating antibodies immobilized on a fiberoptic probe of an immunosensor using ultrasonic irradiation with broadband imaging transducers. The instrumental setup and irradiation conditions for antibody regeneration using ultrasound are described. The results of the measurements with antibody against breast cancer antigen illustrate the effectiveness and potential of the regenerable immunosensor. A 65% removal of the antigens bound to the Mab immobilized on the fiber surface is attained after ultrasound regeneration.

A Portable Surface-Enhanced Raman Spectrometer

Abstract We describe the development of a simple and compact spectrometer for use in Raman and Surface-enhanced Raman Scattering (SERS) analysis. The instrument using an avalanche photodiode is designed to use under field conditions with simple optical samples. Examples of measurement of a variety of chemicals are used to illustrate the performance of the instrument.

Development of a multiarray biosensor for DNA diagnostics

Abstract This work involves the development and evaluation of a multiarray biosensor for DNA diagnostics. The evaluation of various system components developed for the biosensor is discussed. The DNA probes labeled with visible and near infrared (NIR) dyes are evaluated. The detection system uses a two-dimensional charge-coupled device (CCD). Examples of application of gene probes in DNA hybridization experiments and in biomedical diagnosis (detection of the p53 cancer gene) are presented to illustrate the usefulness and potential of the biosensor device.