Dual closed-loop, optoelectronic, auto-oscillatory detection circuit for monitoring fluorescence lifetime-based chemical sensors and biosensors

J Biomed Opt. 2004 May-Jun;9(3):609-17. doi: 10.1117/1.1688814.

Abstract

We present a new detection instrument for sensor measurements based on excited-state fluorescence lifetimes. This system consists of a primary optoelectronic loop containing a resonance-type rf amplifier, a modulatable fluorescence-excitation light source, a fiber optic feedback loop (with a gap for a fluorescent sensor), and a photomultiplier tube. A secondary, phase-feedback optoelectronic circuit consists of a long-wavelength-pass optical filter, a second photomultiplier tube, a photodiode, an electronic phase detector, a dc amplifier, and an electronic phase shifter (inserted into the main loop). This phase-feedback circuit is new with respect to our previous work. Under the appropriate conditions, the main loop exhibits self-oscillations, manifesting themselves as sinusoidal rf modulation of light intensity. The phase-feedback circuit detects the modulation phase shift resulting from the finite excited-state lifetimes of a fluorophore. As the excited state lifetime changes, the phase shift from the electronic phase shifter also changes, which results in a shift in self-oscillation frequency. The detection system uses self-oscillation frequency as the detection parameter and has excellent resolution with respect to changes in excited-state lifetime ( approximately 1 ps). (c) 2004 Society of Photo-Optical Instrumentation Engineers.

Publication types

  • Comparative Study
  • Evaluation Study
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Validation Study

MeSH terms

  • Biosensing Techniques / instrumentation*
  • Biosensing Techniques / methods
  • Electronics
  • Equipment Design
  • Equipment Failure Analysis*
  • Feedback
  • Fluoresceins / analysis*
  • Melanins*
  • Optics and Photonics / instrumentation*
  • Pigments, Biological
  • Reproducibility of Results
  • Sensitivity and Specificity
  • Spectrometry, Fluorescence / instrumentation*
  • Spectrometry, Fluorescence / methods*
  • Transducers*

Substances

  • Fluoresceins
  • Melanins
  • Pigments, Biological
  • fluorescent age pigment
  • seminaphthofluorescein