Systems and methods for accurate optical pH sensing of biofilms

Inventors

Seibel, Eric J. • Nelson, Leonard Y. • Sharma, Manuja • Graham, Jasmine

Assignees

University of Washington

Abstract

Systems and methods for accurate optical pH sensing of biofilms are disclosed. In one embodiment, a method of measuring an extracellular pH level using multiple wavelengths emitted by a fluorescent substance includes: exciting the fluorescent substance at an excitation wavelength; measuring a first fluorescence intensity at a first wavelength of a fluorescence emission; and measuring a second fluorescence intensity at a second wavelength of the fluorescence emission. The second wavelength is different from the first wavelength. The method also includes determining the extracellular pH level based on the first fluorescence intensity at the first wavelength and the second fluorescence intensity at the second wavelength.

Core Innovation

The disclosure provides an optical pH sensing technology for measuring an extracellular pH level using multiple wavelengths emitted by a fluorescent substance. The fluorescent substance is fluorescein, which is excited at an excitation wavelength while fluorescence emission is measured at a first wavelength and at a second wavelength different from the first. The extracellular pH level is then determined based on the first fluorescence intensity and the second fluorescence intensity.

The disclosure further calibrates the fluorescence emission of an anion component and a dianion component of the fluorescein. It uses ambient emission subtraction to condition the measured spectra and divides the anion component and the dianion component by a peak spectral intensity to normalize the components. A spectral unmixing model is applied so that a Measured Spectrum is expressed as a linear combination of anion and dianion spectra using calibration constants.

The disclosed sensing approach is framed as enabling optical measurement of extracellular pH over biological and environmental surfaces without relying on contact-based pH probes. The measurement context described includes tooth plaque bacteria layers, drinking water, irrigation water, recycled vegetable wash water, and plant surfaces. System elements described include a light source with wavelength selection components, wavelength-selective sensors for the two emission bands, and a controller configured to compute extracellular pH using the calibration model.

Claims Coverage

The partial content contains four independent claims. Across these claims, the inventive features focus on measuring extracellular pH from fluorescein fluorescence at two different emission wavelengths, using calibrated anion/dianion spectral components including ambient subtraction and normalization, determining pH via a calibration model, and using opposite correlation directions of the two measured fluorescence intensities with extracellular pH level.

Across the independent claims, extracellular pH is determined from fluorescein fluorescence measured at two different emission wavelengths, using calibrated anion/dianion spectral components represented by a Measured Spectrum linear combination with calibration constants, and in one claim including ambient subtraction and normalization. A further independent concept specifies determining pH using two fluorescence intensities that correlate with opposite signs to the extracellular pH level, enabling pH determination based on both measurements.

Stated Advantages

Documented Applications