Radiation dosimetry using three-dimensional optical random access memories.

The ability to determine particle type and energy plays an important role in the dosimetry of heavy charged particles (HCP) and neutrons. A new approach to radiation dosimetry is presented, which is shown to be capable of particle type and energy discrimination. This method is based on utilising radiation induced changes in the digital information stored on three-dimensional optical random access memories (3D ORAM). 3D ORAM is a small cube (a few mm3) composed of poly(methyl methacrylate) doped with a photochromic dye. and it was originally proposed as a memory device in high speed parallel computers. A Nd:YAG laser system is used to write and read binary information (bits) on the ORAM, which functions as a charged particle detector. Both the read and the write processes use two laser beams that simultaneously strike the material to cause a colour change at their intersection (similar to the darkening of light-sensitive sunglasses when exposed to sunlight.) The laser produces colour changes in the ORAM, which then reverts to the original colour ('bit-flips') at sites where energy is deposited from interaction with incident HCP or neutron-recoil protons. The feasibility of this approach was demonstrated both theoretically and experimentally. Calculations based on track structure theory (TST) predict that when HCP interact with the ORAM material, the local energy deposition is capable of inducing measurable 'bit-flips'. These predictions were recently confirmed experimentally using two types of ORAM systems, one based on spirobenzopyran and the other on anthracene, as the photochromic dyes.

Nanosensor for in vivo measurement of the carcinogen benzo[a]pyrene in a single cell.

This work describes the fabrication and the application of an antibody-based fiber-optic nanosensor for in situ measurements of the carcinogen benzo[a]pyrene (BaP) in a single cell. This antibody-based spectroscopic nanosensor is miniaturized enabling the detection of fluorescent analytes in single cells. In addition to measuring fluorescent analytes in single cells, the nanosensor has the potential to be applied for both diagnostic and proteomics purposes. In this work, the human breast carcinoma cell line, MCF-7, was used as the model system to perform BaP measurements in single cells. A standard concentration curve for BaP was established and used to perform quantitative analyses of BaP in individual cells. From these analyses, it was estimated that the concentration of BaP in the individual cells investigated was approximately 3.61 x 10(-10) M. The results obtained demonstrate the application of antibody-based nanosensors for performing in situ measurements inside a single cell.

Laser-induced fluorescence studies of polycyclic aromatic hydrocarbons (PAH) vapors at high temperatures.

In this work, we present the fluorescence spectra of anthracene and pyrene vapors at different elevated temperatures (from 150 to 650 degrees C) excited with the 337 nm line of a nitrogen laser. We describe the high temperature effects on the resulting spectral properties including spectral intensity, spectral bandwidth and spectral shift. We found that the PAH fluorescence spectral bandwidths become very broad as the temperature increases. The broadening is mainly due to thermal vibrational sequence congestion. We also have found that the fluorescence intensity of pyrene vapor increases with increasing temperature, which results from the increase of the pyrene vapor absorption cross section at 337 nm.

The development of optical nanosensors for biological measurements.

This article discusses and documents the basic concepts of, and developments in, the field of optical nanosensors and nanobiosensors. It describes the progression of this field of research from its birth up to the present, with emphasis on the techniques of sensor construction and their application to biological systems. After a brief overview of the techniques for fabricating nanometer-sized optical fibers, we describe the various types of transducer and bioreceptor molecule presently used for nanosensor and nanobiosensor fabrication.

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+/-0.2x10(-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.

Three-dimensional optical random access memory materials for use as radiation dosimeters.

This article describes the development of the first three-dimensional optical random access memory (3D-ORAM) material and readout system for monitoring energetic neutrons. Two different photochromic dyes, 5'-chloro-6-nitro-1',3',3'-trimethylspiro-[2H-1-benzopyran-2,2'-in doline] (spirobenzopyran) and anthracene, have been investigated for use in these 3-D ORAM dosimeter materials. These dyes were immobilized in a poly(methyl methacrylate) support, and the resulting dosimeter materials were irradiated with neutrons from a Cf-252 source. Fluorescence measurements from the dosimeter show a dramatic decrease in the overall fluorescence intensity of the 3D-ORAM dosimeter exposed to the Cf-252, relative to a nonirradiated dosimeter. In addition, a two-photon excitation readout system has been developed for determining characteristics of the radiation that are necessary for estimating dose.

Intracellular measurements in mammary carcinoma cells using fiber-optic nanosensors.

Submicrometer fiber-optic biosensors have been developed and used to measure toxic chemicals within single cells. Optical fibers that have been pulled to a distal-end diameter of less than 1 micrometer are coated with antibodies to selectively bind the species of interest. This paper describes the use of these fibers to selectively measure the concentration of benzo[a]pyrene tetrol (BPT), a metabolite of benzo[a]pyrene, within individual cells of two different cell lines, human mammary carcinoma cells and rat liver epithelial cells. The results from these measurements have been used to determine the sensitivity, reproducibility, and usefulness of these nanosensors. The detection limit of these biosensors has been determined to be 0.64 +/- 0.17 x 10(-11) M for BPT.