Research fiber photometry system FLiP

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Overview
The RWD Fluorescence Lifetime Photometry System (FLiP) is based on Time-Correlated Single Photon Counting (TCSPC) technology with fiber photometry for real-time monitoring of fluorescence lifetime changes in the brain of freely moving animals, providing a stable and quantitative approach for in vivo studies of neurotransmitter release, protein–protein interactions, and protein conformational changes.

What is Fluorescence Lifetime?
Fluorescence lifetime (τ) is the average time a fluorophore remains in its excited state before emitting a photon. Unlike fluorescence intensity, lifetime is independent of fluorophore concentration and excitation power and reflects conformational changes and the local microenvironment. Lifetime measurements enable separation of multiple lifetime components and sensitive detection of subtle changes, delivering a stable quantitative readout for in vivo experiments.

Why Fluorescence Lifetime?

• Quantitative, cross-sample comparable measurements — no normalization to baseline required
• Stable long-term recordings — suitable for sleep studies, chronic disease models, and longitudinal experiments
• Sensitive detection of dynamic analyte changes using lifetime-based biosensors

Two Mainstream Measurement Methods
Time-Domain
Excites the sample with a pulsed light source and records the temporal fluorescence decay. TCSPC measures time differences between emitted photons and excitation pulses to build decay histograms for exponential fitting, offering high temporal resolution, excellent SNR at low photon flux, and precise separation of multiple lifetime components.

Frequency-Domain
Uses a sinusoidally modulated continuous light source and derives lifetime from phase delay and modulation depth between emission and excitation. Frequency-domain systems are simpler, enable fast acquisition, and can operate without pulsed lasers, making them suitable for high-photon-flux measurements.

Comparison (Time-Domain vs Frequency-Domain)

• Lifetime measurement accuracy: Time-domain — high; Frequency-domain — good
• SNR for weakly fluorescent samples: Time-domain — excellent; Frequency-domain — relatively limited
• Resolution of multiple lifetime components: Time-domain — high precision; Frequency-domain — requires multi-frequency modulation or phasor analysis
• Acquisition speed: Time-domain — relatively fast; Frequency-domain — fast
• High photon flux samples: Time-domain — good; Frequency-domain — excellent
• Laser requirement: Time-domain — pulsed laser; Frequency-domain — modulated continuous source

Highlights of the Fluorescence Lifetime Photometry System

• Exceptional system stability: consistent performance minimizes device-state fluctuations for reliable longitudinal comparisons
• Ultra-low system noise: preserves data integrity under weak-signal conditions
• Reliable long-term recording: stable core components reduce baseline drift over consecutive weeks
• Broad biosensor compatibility: supports the lifetime design range of mainstream biosensors
• Direct quantitative analysis: planned standard-curve function enables direct concentration readouts

Application Examples

• Neuromodulator measurements across animals and chronic timescales: FLiP enables lifetime-based comparisons across animals and over weeks for sensors such as GRAB ACh3.0
• Mechanistic studies in genetic models: used to reveal abnormal PKA activity dynamics in Akap11 mutant mice and related pharmacological responses
• Novel sensor validation: validation of high-speed calcium lifetime sensor (LifeCamp) for baseline and transient calcium measurements in freely moving mice

Technical specifications

• Excitation wavelength options: 488, 515, 560, 640, 670 nm (customizable)
• Pulse frequency: 1–80 MHz
• Lifetime measurement range: 1–10 ns
• Sampling rate: 1–50 Hz
• DIO count: 8
• Voltage level: 3.3–5 V
• Optical fiber core diameter: 200 or 400 µm
• Numerical aperture (NA): 0.37