pH photothermal spectrometer and performing pH photothermal spectroscopy
Inventors
Ahmed, Zeeshan • Hartings, Matthew Robert
Assignees
United States Department of Commerce
Publication Number
US-11624664-B2
Publication Date
2023-04-11
Expiration Date
2040-12-03
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Abstract
A pH photothermal spectrometer includes a container that receives an analyte medium and pH-sensitive chromophore. An excitation fiber and optical thermometer are disposed in the container. The optical thermometer include a light receiver disposed on a temperature detector fiber.
Core Innovation
The invention is a pH photothermal spectrometer for performing pH photothermal spectroscopy that includes a container configured to receive an analyte medium and a pH-sensitive chromophore. The chromophore has an optical absorption spectrum that adjusts based on the pH of the analyte medium. An excitation fiber is disposed in the container to communicate first and second excitation lights of different wavelengths to the chromophore, which absorbs amounts of these lights based on the pH, causing an increase in the analyte temperature.
Additionally, an optical thermometer comprising a temperature detector fiber and a light receiver is disposed in the container in thermal and optical communication with the analyte medium. The light receiver adjusts its temperature to match the analyte temperature and exhibits an optical resonance that changes in response to the temperature change. By measuring the ratio of the optical amounts of probe light entering and reflected from the light receiver, the system provides a determination of the pH of the analyte medium.
The problem solved by this invention relates to limitations of conventional pH sensors, especially in biological environments. Existing polymeric waveguide sensors require low ionic strength environments and inferring pH indirectly through osmotic pressure-induced swelling of hydrogels, suffer from hysteresis upon dehydration, require frequent recalibration, and may interfere with biological processes. The pH photothermal spectrometer overcomes such technical limitations by providing a small footprint probe compatible with biological environments, capable of operating in high ionic strength solutions, embedding into substrates, and maintaining stability over lengthy periods without weekly recalibration.
Claims Coverage
The patent contains one principal independent claim directed to a pH photothermal spectrometer and one independent claim directed to a process for performing pH photothermal spectroscopy. The main inventive features relate to the structure and function of the spectrometer and the steps in the spectroscopic process.
pH photothermal spectrometer with integrated excitation and detection fibers
A spectrometer comprising a container that receives an analyte medium and a pH-sensitive chromophore, an excitation fiber that communicates two excitation lights of distinct wavelengths to the chromophore for absorption dependent on pH, and an optical thermometer with a temperature detector fiber and a light receiver that reflects probe light whose optical amount depends on the receiver temperature, enabling determination of pH from optical signals.
Optical thermometer with temperature-sensitive resonance
The light receiver is disposed on the terminus of the temperature detector fiber, is in thermal communication with the analyte medium, has a receiver temperature that matches the analyte temperature, and features an optical resonance at a resonance wavelength that changes in response to temperature, enabling reflected light intensity changes used to determine pH.
Process for performing pH photothermal spectroscopy
A process comprising delivering first and second excitation lights to the pH-sensitive chromophore, which alters its optical absorption spectrum in response to the analyte pH and absorbs corresponding amounts of excitation light, causing temperature changes of the analyte medium and light receiver. Measurement of reflected probe light intensity changes allows determination of pH from a ratio of optical amounts.
The independent claims describe a system integrating excitation and temperature sensing fibers to exploit pH-dependent photothermal effects in a chromophore and a corresponding process of measurement, providing pH determination within a container holding an analyte medium. The inventive features focus on the combination of pH-dependent optical absorption inducing thermal changes and the use of a temperature-sensitive optical resonance for pH measurement.
Stated Advantages
Small form factor compatible with biological environments.
Operates in high ionic strength solutions, overcoming limitations of conventional waveguide sensors.
Embeddable in substrates to allow pH measurement in optically inaccessible regions.
Biocompatible materials that do not interfere with cell growth or biofouling.
Does not require frequent recalibration; stable measurements over 2-3 weeks.
Does not require measuring excitation light after interaction with the chromophore, reducing measurement errors.
Avoids use of toxic materials such as metals, corrosive salts, or toxic dyes.
Temperature dependence is addressed by employing ratiometric measurements for improved accuracy.
Documented Applications
Use in bio-industrial processing and tissue engineering industry requiring small footprint compatible probes.
Measurement of pH in biological tissues, including cell media and human blood samples.
Embedding in microtissues or biomanufacturing vessels for monitoring pH over cell proliferation and differentiation cycles.
Quality control tools for three-dimensional tissue analogues and cell-laden constructs in pharmaceutical drug screening and regenerative medicine.
Non-invasive monitoring of biological conditions such as acidosis or presence of therapeutic drugs in tissue.
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