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PubMed2001

Radiative decay engineering: biophysical and biomedical applications.

Fluorescence spectroscopy is a widely used research tool in biochemistry and molecular biology. Fluorescence has also become the dominant method enabling the revolution in medical diagnostics, DNA sequencing, and genomics. To date all the fluorescence observables, including spectral shifts, anisotropies, quantum yields, and lifetimes, have all been utilized in basic and applied uses of fluorescence. In this forward-looking article we describe a new opportunity in fluorescence, radiative decay engineering (RDE). By RDE we mean modifying the emission of fluorophores or chromophores by increasing or decreasing their radiative decay rates. In most fluorescence experiments the radiative rates are not changed because these rates depend on the extinction coefficient of the fluorophore. This intrinsic rate is not changed by quenching and is only weakly dependent on environmental effects. Spectral changes are usually caused by changes in the nonradiative rates resulting from quenching or resonance energy transfer. These processes affect the emission by providing additional routes for decay of the excited states without emission. In contrast to the relatively constant radiative rates in free solution, it is known that the radiative rates can be modified by placing the fluorophores at suitable distances from metallic surfaces and particles. This Review summarizes results from the physics literature which demonstrate the effects of metallic surfaces, colloids, or islands on increasing or decreasing emissive rates, increasing the quantum yields of low quantum yield chromophores, decreasing the lifetimes, and directing the typically isotropic emission in specific directions. These effects are not due to reflection of the emitted photons, but rather as the result of the fluorophore dipole interacting with free electrons in the metal. These interactions change the intensity and temporal and spatial distribution of the radiation. We describe the unusual effects expected from increases in the radiative rates with reference to intrinsic and extrinsic biochemical fluorophores. For instance, the decreased lifetime can result in an effective increase in photostability. Proximity to nearby metallic surfaces can also increase the local field and modify the rate of excitation. We predict that the appropriate localization of fluorophores near particles can result in usefully high emission from "nonfluorescent" molecules and million-fold increases in the number of photons observable from each fluorophore. We also describe how RDE can be applied to medical testing and biotechnology. As one example we predict that nearby metal surfaces can be used to increase the low intrinsic quantum yields of nucleic acids and make unlabeled DNA detectable using its intrinsic metal-enhanced fluorescence.

Energy Transfer↗
PubMed1984

Science and standards. RF-hazards and standards: an historical perspective.

The following topics are discussed: Standard of safety considerations. Early efforts in bioengineering and biophysics before and after World War II, Work after World War II (1950s), Early interest in hazards, Soviet work and The Tri-Service area and ANSI. The author concludes that the historical development of biophysics and bioengineering, both as a whole and in the specialty area of nonionizing radiation, proceeded in a fairly rational fashion. Formulation of exposure standards in the West was based on the biophysical approach, which prevails in the interdisciplinary sciences involving biomedical and engineering disciplines. No pressure by an "industrial-military establishment" was evident in the quest for standards, and the Soviet approach and work were under surveillance from the late 1950's. A continuous interest in athermal effects has persisted since the 1930's. Historical accounts are based on personal experience and study of the literature. They are therefore limited to the extent that such experience and study is incomplete. The author had the good fortune to participate over a professional lifetime in the development of biophysical and biomedical engineering sciences, including those that address nonionizing radiation and Western standards of safety.

Biomedical Engineering↗
PubMedDate not supplied

A study on the current situation in the biomedical technology and clinical engineering sector in Bulgaria--advances, trends and needs.

A survey of the clinical engineering sector in Bulgaria was carried out, within the context of the 1996 Phare Partnership Program, with the aim to provide a reflection of the current situation concerning the management of biomedical technology and investigate the relevant needs in hospitals. The survey was initiated by the Institute of Biomedical Technology (INBIT) in Patras, Greece, with the active support of national organizations, educational institutions and other parties that share involvement in the overall management of medical devices in Bulgaria. This paper summarizes the results of the survey, giving an insight into the situation in the field and providing the basis for a more thorough study on the Biomedical Technology and Clinical Engineering sectors in Bulgaria.

Biomedical Engineering↗