Fluorescence Anisotropy as a Temperature-Sensing Molecular Probe Using Fluorescein.

Area of Science:

• Biophysics
• Analytical Chemistry
• Microfluidics

Background:

• Fluorescence anisotropy is a valuable tool for studying molecular interactions and states.
• Microfluidic systems require accurate temperature monitoring for controlled experiments.
• Existing temperature sensing methods may have limitations in microfluidic environments.

Purpose of the Study:

• To develop and validate fluorescence anisotropy as a microfluidic temperature sensor.
• To investigate the influence of parameters like viscosity on temperature sensing.
• To demonstrate temperature imaging capabilities in microfluidics.

Main Methods:

• Utilized fluorescein as a temperature-sensing probe in a glycerol-aqueous ammonia solution.
• Measured fluorescence anisotropy of fluorescein under varying conditions.
• Compared fluorescence anisotropy with fluorescence intensity for microfluidic applications.
• Assessed viscosity and temperature dependence of anisotropy.
• Performed temperature imaging using focused laser heating.

Main Results:

• Fluorescence anisotropy effectively measures microfluidic temperature fields.
• Viscosity and molecular size critically influence the temperature coefficient of anisotropy.
• Anisotropy is valid for microfluidics with non-uniform liquid thickness.
• A practical calibration procedure for apparatus constants was proposed.
• Temperature distribution imaging under laser heating was successfully demonstrated.

Conclusions:

• Fluorescence anisotropy is a viable and sensitive method for microfluidic temperature sensing.
• Optimizing the relationship between molecular size and viscosity enhances temperature sensitivity.
• The technique holds potential for advanced temperature imaging and analysis in microfluidic devices.