Journal: Trends in biotechnology

Article Title: Potential applications of lifetime-based, phase-modulation fluorimetry in bioprocess and clinical monitoring

doi: 10.1016/S0167-7799(00)88915-5

Figure Lengend Snippet: Conceptual phase-fluorimetric blood-gas instrumentation based on a laser diode light source. This is an example of a multianalyte sensing system using a single set of electronics. On-line sampling is done through a blood-gas catheter. Although long-lifetime fluorophores are desirable for simplifying instrumentation, such probes are not yet available for all analytes. To accommodate shorter-lifetime probes requiring higher modulation frequencies, the fluorimeter uses cross-correlation detection to simplify instrumentation46. By modulating the gain of the photomultiplier tube at the synthesizer frequency plus a small increment (f + Δf), the resulting photocurrent modulates at the lower frequency Δf, but contains the desired phase values. While LEDs can be safely modulated up to 100 MHz, laser diodes permit modulation to several GHz. Both sources are inexpensive. Depending upon the set of fluorescent probes used, either light source can be utilized in such a multianalyte sensor.

Article Snippet: Powerful and inexpensive light sources such as red (>600 nm) laser diodes that can be intrinsically modulated to several GHz and the recent availability of high power, modulatable (1000 millicandela, ≈100 MHz) blue gallium nitride light-emitting diodes (LEDs) (45030 nm, Nichia Chemical Industries, Japan) have facilitated the construction of simple, hand-held devices.

Techniques: Sampling