Principle of operation
The LF402 Metabolic achieves an exceptionally good separation between the fast decaying NADH signal in the detection channel 1 and a slower decaying reference signal in channel 2 by using two integrator gates with different temporal positions:


The fluorescence of reduced NADH of human and animal tissues has a lifetime of less than 1 ns. In contrast to this the oxidized form NAD+ is not fluorescing when excited at 337 nm. Therefore, the uv-excited fluorescence of NADH can function as indicator of the metabolic activity of these kinds of tissues. This method was optimized at IOM by generating an internal reference signal in a second detection channel where that integration gate was delayed by 9 ns with relation to the first channel.
In this way a higher selectivity of the non-invasive characterization of tissue metabolism is obtained in comparison to other fluorescence based methods - even in the presence of strongly scattering samples and accompanied by a largely reduction of blood influence.

The choice of a suitable configuration and lay-out of the fibre-optic probe enables the adaptation of the instrument to specific experimental conditions.

In the area of biotechnology another application of the LF402 Metabolic is the long-term monitoring of miniaturized high cell density culture systems. Critical cell culture states or the optimal time for harvest can be estimated much better now.