Materials and methods for luminescence-based carbon dioxide sensing

Abstract

An apparatus for carbon dioxide monitoring is disclosed that includes a photoluminescent carbon dioxide sensitive probe with a polymer matrix and a sensing dye, a photon source configured to send photons to the probe, a photodetector configured to detect light emitted from the probe when the photon source sends photons to the probe, a carbon dioxide permeable light redirecting layer, the carbon dioxide sensitive probe disposed between the light redirecting layer and the photodetector, and a controller in electrical communication with the photon source and the photodetector, the controller configured to execute a program for calculating a level of carbon dioxide adjacent the probe from an electrical signal received from the photodetector, the program being stored in the controller. In one form, the polymer matrix includes a polymer selected from the group consisting of acrylate polymers, methacrylate polymers, polyurethane polymers, and blends and copolymers thereof.

Description

[Technical field]

[0001] <CROSS REFERENCE TO RELATED APPLICATIONS> This application is based on and claims the benefit of and priority to U.S. Application No. 63 / 331,829 (filed April 16, 2022), the entire contents of which are incorporated herein by reference.

[0002] <Statement Regarding Federally Sponsored Research> This invention was made with government support under Grant No. FA9550-17-1-0277 awarded by the Air Force Office of Scientific Research and Grant No. HU0001-17-2-0009 awarded by the Henry M. Jackson Foundation for the Advancement of Military Medicine, Inc. The Government has certain rights in this invention.

[0003] 1. Field of the invention The present invention relates to devices, materials and methods for analyte monitoring, and more particularly to devices, materials and methods for carbon dioxide monitoring. [Background technology]

[0004] 2. Description of Related Technology Carbon Dioxide (CO 2 ) plays various roles in the human body, such as driving respiration, regulating blood pH, and the affinity of hemoglobin for oxygen. 2 Partial pressure (pCO 2 Monitoring of CO in arterial blood is of great importance for the medical diagnosis and treatment of human diseases, such as respiratory and metabolic disorders. For example, the suitability of spontaneous and mechanical ventilation is usually determined by the CO concentration in arterial blood. 2However, the current "gold standard" method for obtaining such a reading is based on the invasive technique of arterial blood gas sampling by placing an arterial line. One non-invasive alternative to arterial gas sampling is the measurement of pCO at the skin surface or in expired air. 2 There are means to monitor blood pressure, which reduces or eliminates the need for blood gas sampling, reducing the risk of developing patient comorbidities and improving patient comfort. However, current technology based on infrared sensors requires large and expensive equipment, lengthy bed calibration procedures, patient immobility, etc.

[0005] Thus, miniaturized sensors that can be integrated into wearable devices, for example for continuous capnography or transcutaneous CO 2 There is a demand for a sensor that can be used in a wide range of applications, such as optical CO sensors based on luminescent materials. 2 The sensor can provide several advantages, such as CO 2 This provides accurate level detection and great potential for miniaturization. Summary of the Invention

[0006] The present invention fulfills these needs by providing devices, materials and methods for monitoring analytes, such as carbon dioxide.

[0007] In one aspect, the present disclosure provides an apparatus for carbon dioxide monitoring, the apparatus comprising: a photoluminescent carbon dioxide sensitive probe comprising a polymer matrix and a sensing dye, a photon source configured to send photons to the probe, a photodetector configured to detect light emitted from the probe when the photon source sends photons to the probe, and a controller in electrical communication with the photon source and the photodetector, the controller configured to execute a program for calculating a level of carbon dioxide adjacent to the probe from an electrical signal received from the photodetector, the program being stored in the controller, the polymer matrix comprising a polymer selected from the group consisting of acrylate polymers, methacrylate polymers, polyurethane polymers, and blends and copolymers thereof.

[0008] In one embodiment of the device, the polymer matrix comprises a hydrophobic polymer. In one embodiment of the device, the polymer matrix comprises a polymer selected from the group consisting of alkyl methacrylate polymers. In one embodiment of the device, the polymer matrix comprises poly(propyl methacrylate) (PPMA).

[0009] In one aspect, the present disclosure provides an apparatus for carbon dioxide monitoring, the apparatus comprising: a photoluminescent carbon dioxide sensitive probe comprising a polymer matrix and a sensing dye, a photon source configured to send photons to the probe, a photodetector configured to detect light emitted from the probe when the photon source sends photons to the probe, a carbon dioxide permeable light redirecting layer, the carbon dioxide sensitive probe disposed between the light redirecting layer and the photodetector, and a controller in electrical communication with the photon source and the photodetector, the controller configured to execute a program for calculating a level of carbon dioxide adjacent the probe from an electrical signal received from the photodetector, the program stored on the controller.

[0010] In one embodiment of the device, the light redirecting layer comprises a silicone film containing a pigment. The pigment can be white. In one embodiment of the device, the light redirecting layer scatters light. In one embodiment of the device, the light redirecting layer reflects light. In one embodiment of the device, the light redirecting layer scatters light and reflects light. In one embodiment of the device, the device further comprises a heater for increasing the temperature of the light redirecting layer and / or the probe. In one embodiment of the device, photons from the photon source having a wavelength longer than that required to excite the sensing dye are filtered using a short pass filter. In one embodiment of the device, the light emitted from the photon source is filtered by a long pass filter covering the photodetector. In one embodiment, the device further comprises a partially or completely air impermeable layer disposed between the carbon dioxide sensitive probe and the photodetector. In one embodiment, the device further comprises a partially or completely air impermeable outer layer. In one embodiment of the device, the polymer matrix comprises a polymer selected from the group consisting of acrylate polymers, methacrylate polymers, silicate polymers and sol-gels, polyurethane polymers (e.g., in the form of films or foams), and blends and copolymers thereof.

[0011] In yet another aspect, the present disclosure provides an apparatus for carbon dioxide monitoring, the apparatus comprising: a photoluminescent carbon dioxide sensitive probe comprising a polymer matrix and a sensing dye, a first photon source configured to send photons to the probe at a first wavelength, a second photon source configured to send photons to the probe at a second wavelength different from the first wavelength, a photodetector configured to detect light emitted from the probe when the first and second photon sources send photons to the probe, and a controller in electrical communication with the first and second photon sources and the photodetector, the controller configured to execute a program for calculating a level of carbon dioxide adjacent to the probe from an electrical signal received from the photodetector, the program stored in the controller.

[0012] In one embodiment of the device, an isosbestic point of the excitation spectrum of the sensing dye is at the first wavelength. In one embodiment of the device, sending photons to the probe at the first wavelength provides a normalization factor to account for brightness variations in the polymer matrix. In one embodiment of the device, the controller is configured to execute a program stored in the controller for calculating a level of carbon dioxide adjacent to the probe using a fluorescence ratio that provides a measure proportional to the level of carbon dioxide adjacent to the probe, normalized using the normalization factor. In one embodiment of the device, the controller is configured to execute a program stored in the controller for executing a calibration algorithm such that the device can report the level of carbon dioxide adjacent to the probe via wired or wireless communication. In one embodiment of the device, the calibration algorithm uses different calibration parameters depending on whether the derivative of the fluorescence ratio is positive or negative. In one embodiment of the device, the controller is configured to execute a program stored in the controller for calculating a level of carbon dioxide adjacent to the probe by detecting the intensity of the emission excited at the first wavelength and the second wavelength. In one embodiment of the device, the first photon source and the second photon source are modulated by sinusoidal voltages, and the intensity of the fluorescent response of the sensing dye is defined as the amplitude extracted by applying multiple linear regression to the measured sinusoidal responses.

[0013] In any embodiment of the device for carbon dioxide monitoring, the optical detector detects tissue pCO 2and detecting a fluorescent response of the sensing dye that provides a pH-sensitive fluorescent dye. The sensing dye may comprise a pH-sensitive fluorescent dye. In one embodiment, the pH-sensitive fluorescent dye comprises 8-hydroxy-1,3,6-pyrenetrisulfonic acid trisodium salt (HPTS). The sensing dye may comprise a pH-sensitive fluorescent dye in an anionic form and a quaternary ammonium cation. The carbon dioxide sensitive probe may comprise a phase transfer reagent embedded in the polymer matrix with the sensing dye. The volume ratio (v / v) of the phase transfer reagent to the sensing dye may be greater than 0% and less than or equal to 40%, or the volume ratio (v / v) of the phase transfer reagent to the sensing dye may be greater than 0% and less than or equal to 20%, or the volume ratio (v / v) of the phase transfer reagent to the sensing dye may be greater than 0% and less than or equal to 10%, or the volume ratio (v / v) of the phase transfer reagent to the sensing dye may be greater than or equal to 2% and less than or equal to 8%.

[0014] In any embodiment of the device for carbon dioxide monitoring, the phase transfer reagent provides the water necessary to generate carbonic acid for protonating the pH sensitive fluorescent dye. The phase transfer reagent can include an alkyl ammonium hydroxide. The phase transfer reagent can include tetraoctyl ammonium hydroxide. In any embodiment of the device for carbon dioxide monitoring, the carbon dioxide sensitive probe can have storage stability with no significant decrease in sensitivity when the carbon dioxide sensitive probe is stored in air under dark conditions for at least 7 days.

[0015] In any embodiment of the device for carbon dioxide monitoring, the device may be a transcutaneous optical device. In any embodiment of the device for carbon dioxide monitoring, the device may further comprise a display in electrical communication (wired or wireless) with the controller, the controller configured to execute the program stored in the controller to display the carbon dioxide level on the display. The controller may be configured to execute the program stored in the controller to store values ​​of the carbon dioxide level at multiple times over a period of time. In any embodiment of the device for carbon dioxide monitoring, the device may further comprise a display in electrical communication with the controller, the controller configured to execute the program stored in the controller to display values ​​of the carbon dioxide level at multiple times over a period of time.

[0016] In any embodiment of the device for carbon dioxide monitoring, the device may be insertable into a portion of a patient's body. In any embodiment of the device for carbon dioxide monitoring, the photon source, the photodetector, and the controller may be located inside or outside a support structure. In any embodiment of the device for carbon dioxide monitoring, the device may include a band of structure for fastening the support structure to a portion of a patient's body. In any embodiment of the device for carbon dioxide monitoring, the device may include structure for fastening the support structure inside or outside a nose or mouth. In any embodiment of the device for carbon dioxide monitoring, the device may include structure for fastening the support structure inside or outside a nasal tube, nasal cannula, mask, helmet, tracheal tube, or breathing apparatus.

[0017] In any embodiment of the device for carbon dioxide monitoring, the device may further comprise an optical waveguide for transmitting photons from each of the photon sources to the probe. The optical waveguide may be an optical fiber. In any embodiment of the device for carbon dioxide monitoring, the device may further comprise an optical waveguide for transmitting light emitted from the probe to the photodetector. The optical waveguide may be an optical fiber.

[0018] Any of the embodiments of the device for carbon dioxide monitoring may be included in a kit for monitoring carbon dioxide, the kit comprising one or more additional photoluminescent carbon dioxide sensitive probes. Each of the photoluminescent carbon dioxide sensitive probes may be provided in a package that is opaque to photons of a wavelength that causes the probe to emit light. The package may comprise an indicator of the usable life of the photoluminescent carbon dioxide sensitive probe. Any of the embodiments of the device for carbon dioxide monitoring may be provided with a medical device, where the device is attached to the medical device.

[0019] In yet another aspect, the present disclosure provides a method for end-tidal carbon dioxide monitoring, the device comprising: a photoluminescent carbon dioxide sensitive probe with a polymer matrix and a sensing dye, the probe being placed in or near the nostrils or mouth, or incorporated into a device or device extension incorporated into a cannula, mask or helmet, a first photon source configured to send photons to the polymer matrix probe at a first wavelength, a second photon source configured to send photons to the probe at a second wavelength different from the first wavelength, a photodetector configured to detect light emitted from the probe when the first and second photon sources send photons to the probe, and a controller in electrical communication with the first and second photon sources and the photodetector, the controller configured to execute a program for calculating a level of carbon dioxide adjacent to the probe from electrical signals received from the photodetector, the program stored in the controller.

[0020] In yet another aspect, the present disclosure provides a method for detecting a concentration of an analyte, the method comprising: (a) providing an apparatus comprising: (i) a probe comprising a polymer matrix and a sensing dye; (ii) a first photon source configured to transmit photons to the probe at a first wavelength; (iii) a second photon source configured to transmit photons to the probe at a second wavelength different from the first wavelength; and (iv) a photodetector configured to detect light emitted from the probe when the first photon source and the second photon source transmit photons to the probe; and (b) calculating a concentration of the analyte adjacent to the probe based on the light emitted from the probe and detected by the photodetector and an isosbestic point at the first wavelength within a physiological range of the analyte in an excitation spectrum of the sensing dye.

[0021] In any embodiment of the method, step (b) may further comprise calculating a concentration of the analyte adjacent to the probe based on a normalization factor determined by sending photons at the first wavelength to the probe to account for brightness variations in the polymer matrix. In any embodiment of the method, step (b) may further comprise calculating a concentration of the analyte adjacent to the probe based on a luminescence ratio providing a measure proportional to the concentration of the analyte adjacent to the probe, the measure normalized using the normalization factor. In any embodiment of the method, step (b) may further comprise calculating a concentration of the analyte adjacent to the probe based on a calibration algorithm such that the device can report the concentration of the analyte adjacent to the probe via wired or wireless communication. The calibration algorithm may use different calibration parameters depending on whether the derivative of the luminescence ratio is positive or negative.

[0022] In any embodiment of the method, step (b) may further comprise calculating the concentration of the analyte adjacent to the probe by detecting the luminescence emission intensity excited at the first wavelength and the second wavelength. In any embodiment of the method, step (b) may further comprise calculating the concentration of the analyte adjacent to the probe by modulating with a sinusoidal voltage, the intensity of the luminescence response of the sensing dye being defined as an amplitude extracted by applying multiple linear regression to the measured sinusoidal response. The analyte may be selected from the group consisting of molecular oxygen, carbon dioxide, nitric oxide, analytes dissolved in plasma and tissue, and hydrogen ions. The analyte may be selected from the group consisting of molecular oxygen, carbon dioxide, and mixtures thereof. The analyte may be carbon dioxide. The concentration of the analyte may be calculated as pCO2. 2 It can be calculated as follows:

[0023] One advantage of the present disclosure is that physiological CO 2 Highly luminescent CO with sensitivity in the range (0-50mmHg) 2 It is an advantage to be able to provide a sensing material that is recognized as being photostable such that the signal of the material remains at a high level during long term use.

[0024] Another advantage of the present disclosure is that when combined with a sensing material, it can detect transdermal CO 2 The objective of this invention is to provide a non-invasive, lightweight, wired or wireless wearable device that can continuously monitor CO partial pressure. 2 Luminescence from the sensing material is excited and detected by the above-described device, allowing the measurement of CO within the physiological range. 2 The sensing material disclosed herein can be used as a wearable CO 2 Sensing applications also exhibit important material properties: for example, the sensing material is mechanically robust and can be formed into a variety of different form factors, and in the case of skin-worn devices, the material can be insensitive to changes in moisture to provide consistent performance across different body sites and physiological and environmental variations.

[0025] Non-limiting examples of uses of the disclosed technology include transcutaneous tissue CO in patients undergoing burn, metabolic or post-operative recovery. 2 and measurement of oxygen tension, capnography, end-tidal CO 2 monitoring, continuous arterial gas sensors, etc.

[0026] These and other features, aspects, and advantages of various embodiments of the present disclosure will become better understood with reference to the following description, appended claims, and accompanying drawings. [Brief description of the drawings]

[0027] [Figure 1A]FIG. 1 shows one embodiment of a wearable device and CO2 sensing film for continuous transdermal monitoring of pCO2. The film emission is excited using two high intensity LEDs (e.g., 405 nm and 470 nm) and sampled using a long pass filter (e.g., 500 nm) and a PIN photodiode as the photodetector. [Figure 1B] FIG. 14 shows the light spectra of two different excitation LEDs and the CO2 sensing dye emission shown in the insert. The LED emission is removed by adding a 500 nm long pass filter. [Diagram 2] Panel (a) shows the chemical structures of the ion pairs and polymer matrices: (HPTS) / (CTA)3, (HPTS) / (TOA)4, poly(methyl methacrylate) (PMMA), and poly(propyl methacrylate) (PPMA). The pH sensitivity of the ion pairs arises from the highlighted functional groups. Panel (b) shows the emission spectra of (HPTS) / (CTA)3 in PPMA and (HPTS) / (TOA)4 in PPMA and PMMA under CO2 and N2 conditions. Panel (c) shows the excitation spectra (collected at 570 nm) of (HPTS) / (CTA)3 in PPMA and (HPTS) / (TOA)4 in PPMA and PMMA under CO2 and N2 conditions. Panel (d) shows the moisture sensitivity of (HPTS) / (TOA)4 in PPMA and PMMA under CO2 and N2 conditions. Panel (e) is a comparative diagram of the photostability of (HPTS) / (TOA)4 in PPMA and PMMA under air conditions. [Diagram 3]Panel (a) shows the sensitivity of the material consisting of 240 μM or 480 μM (HPTS) / (TOA)4 in PPMA with 0%, 5%, 10%, 20% and 40% (v / v) TOAOH in methanol. Panel (b) shows the photostability under air conditions of the sensing film made of 240 μM (HPTS) / (TOA)4 in PPMA with 5%, 10% and 20% (v / v) TOAOH solution and the sensing film made of 480 μM (HPTS) / (TOA)4 in PPMA with 20% (v / v) TOAOH solution. Panel (c) shows the moisture sensitivity under CO2 and N2 conditions of the material made of 240 μM (HPTS) / (TOA)4 in PPMA with 10% (v / v) TOAOH solution. [Figure 4] Panel (a) shows the excitation spectrum measured at 570 nm when (HPTS) / (TOA)4 in PPMA formulation was exposed to different CO2 partial pressures. Panel (b) shows the normalized R (range between [0,1]) vs. CO2 partial pressure for the PPMA / white coating sample, indicating delayed diffusion of CO2 through the white coating (CO2 → white), which disappears at temperatures above 40 °C. The fluorescence ratio R measured in the wearable device is highly sensitive to changes in CO2, and our prototype showed a delayed response to the reference CO2 sensor at T = 25 °C (panel (c)). This is due to CO2 diffusion through the white light scattering layer, which disappears upon heating to T = 44 °C (panel (d)). Panel (e) shows the normalized R vs. CO2 for the wearable at different temperatures, where the delayed response disappears at higher temperatures. Panel (f) shows the time delay (lag) between the signal of our prototype and the reference CO2 sensor as a function of temperature. [Diagram 5]Panel (a) shows the response of the film to changes in CO2, together with the CO2 readings of the reference sensor plotted. Panel (b) shows the fitting of two different calibration algorithms to the fluorescence ratio R, shown as a function of the reference CO2. Fit1 considers the squared dependence on CO2, whereas Fit2 also considers the squared dependence on CO2, but with different coefficients depending on whether R (and thus CO2) is increasing or decreasing. Panel (c) shows the reference CO2 obtained using both algorithms and the estimated CO2 of our prototype. [Figure 6] FIG. 1 shows the aging and sensitivity of materials, specifically the effect of aging time on the sensitivity of materials made with (HPTS) / (TOA)4 in PPMA with 5% and 10% TOAOH under air and dark conditions. [Figure 7] FIG. 1 shows material spectral characterization, specifically the spectra of HTPS(TOA)4 / PPMA obtained using a reference FLS1000 photoluminescence spectrometer (Edinburgh Instruments) with excitation at 405 nm and 470 nm, with and without a 495 long pass filter. [Figure 8] Figure 10 shows the characterization of the material spectrum, specifically the spectrum measured from the wearable device compared to the spectrum of the reference spectrometer of Figure 7 (grey line). Panel (a) shows a 405 nm LED exhibiting unwanted phosphorescence, which is filtered out using a short-pass flexible filter (SP) that passes only the LED emission required to excite the HPTS dye. This LED emission is filtered by a long-pass filter before reaching the photodiode, so that only the HPTS emission is detected. Panel (b) shows a 470 nm LED that does not require such filtering. [Figure 9]A diagram showing the calibration setup includes a sealed chamber with a heater 910, a reference CO2 sensor 920, a CO2 tank 950, an N2 tank 940, and an automatic gas mixer 930. [Figure 10] Figure 1 shows the performance of the calibration algorithms, specifically the residuals from panel (a) Fit1 and panel (b) Fit2. It can be clearly seen how Fit2 describes the data with high fidelity, since the residuals are more randomly scattered compared to Fit1, among which trends in the data can still be detected. The first calibration algorithm, Fit1, is obtained by combining several different reaction rates and material parameters, e.g. quantum yield. This model captures the average trend of the response, but due to the different rates for protonation and deprotonation, the estimated pCO2 is always either over- or under-estimated. To take this into account, we propose a second model, Fit2, which uses the same algorithm as Fit1, but with different calibration parameters depending on whether CO2 is increasing or decreasing. [Figure 11] Figure 1 shows the performance of the calibration algorithms. Specifically, panel (a) shows the ideal sensor response compared to the calibration model sensor response. Panel (b) is the Bland-Altman plot for Fit1, and panel (c) is the Bland-Altman plot for Fit2. The standard deviation of Fit2 is approximately half that of Fit1. [Figure 12] FIG. 1 shows a linear calibration algorithm; specifically, fitting a linear model to the luminescence ratio to CO2 as described in Zhu et al., “A new ratiometric, planar fluorosensor for measuring high resolution, two-dimensional pCO2 distributions in marine sediments”, Marine Chemistry 2006, 101, 40-53, which does not fully capture the curvature of the data. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] In the following detailed description, like parts in the various figures are designated by like reference numerals. None of the figures are drawn to scale. When dimensions are given in the text or figures, such dimensions are merely numerical examples that may be used in implementing one or more embodiments and are not intended to limit the scope of the invention disclosed herein.

[0029] The present disclosure provides devices, materials and methods for analyte monitoring, and more specifically, for luminescence-based carbon dioxide sensing.

[0030] Before describing the present invention in detail, it should be understood that the present invention is not limited to the specific embodiments described herein. Furthermore, the terminology used herein is used only for the purpose of describing specific embodiments, and is not intended to limit the present invention. The scope of the present invention is limited only by the claims. As used herein, the singular forms "a," "an," and "the" include plural embodiments unless the context clearly indicates otherwise.

[0031] It will be apparent to those skilled in the art that many further improvements can be made in addition to those already described herein without departing from the spirit of the invention. In interpreting the present disclosure, all terms should be interpreted in the broadest possible manner consistent with the context. Variations such as "comprising," "including," or "having" should be understood to describe elements, components, or steps in a non-exclusive manner, such that the elements, components, or steps can be combined with other elements, components, or steps not expressly mentioned. Embodiments described as "comprising," "including," or "having" a particular element are also intended to mean "consisting essentially of" or "consisting of" that element, unless the context clearly indicates otherwise. Aspects of the present disclosure described as a system should be understood to be applicable to methods as well, and vice versa, unless the context clearly indicates otherwise.

[0032] Referring now to FIG. 1A, a non-limiting example embodiment of a wearable device 10 for transdermal carbon dioxide monitoring of the present invention is shown. The device 10 includes a photoluminescent carbon dioxide sensitive probe 15, which includes a polymer matrix and a sensing dye. A first photon source 20 is configured to send photons to the probe 15 at a first wavelength, and a second photon source 30 is configured to send photons to the probe 15 at a second wavelength. A photodetector 40 is configured to detect light emitted from the probe 15 when the first photon source 20 and the second photon source 30 send photons to the probe 15. Illumination from the photon source can be modulated (e.g., square wave, sine wave, triangle wave, sawtooth, etc.) or constant. The photodetector 40 can be a PIN photodiode. A controller 50 is in electrical communication with the first photon source 20, the second photon source 30, and the photodetector 40. The controller 50 is configured to execute a program stored in the controller 50 for calculating the level of carbon dioxide adjacent the probe 15 from the electrical signal received from the photodetector 40. The device 10 includes a carbon dioxide permeable light scattering layer 60 and a transparent semi-permeable adhesive film 70. The device 10 may include a heater and / or thermistor 80, and includes a band 90 configured to secure the device 10 to a site on the patient's body as shown in FIG. 1A. The device 10 is configured to measure pCO 2 can be measured directly, without the need for perfusion or underlying blood vessels. The sensing components can be safely secured within the device 10, and the sensing components can be non-invasive, so exogenous dyes, injectable drugs, or needles may not be required. The optical device 10 can be constructed in a short time, and readings of the device 10 can be virtually instantaneous. The optical device 10 may not require bedside calibration or heating, may not require underlying blood flow, and provides a simple readout with minimal equilibration time to obtain displayable results, thereby providing a solution to the problems that generally inhibit clinical carbon dioxide sensing.

[0033] In the device 10, the photoluminescent carbon dioxide sensitive probe 15 can comprise a polymer matrix. In some embodiments, the polymer matrix comprises a hydrophobic polymer. In some embodiments, the polymer matrix comprises a polymer selected from the group consisting of acrylate polymers, methacrylate polymers, and blends and copolymers thereof. Non-limiting examples of acrylate polymers include poly(acrylic acid), poly(methyl acrylate), poly(ethyl acrylate), poly(propyl acrylate), poly(butyl acrylate). Non-limiting examples of methacrylate polymers include poly(methyl methacrylate), poly(ethyl methacrylate), poly(propyl methacrylate), poly(butyl methacrylate), poly(hydroxyethyl methacrylate). In some embodiments, the polymer matrix comprises a polymer selected from the group consisting of alkyl methacrylate polymers. In some embodiments, the polymer matrix comprises poly(propyl methacrylate) (PPMA).

[0034] In the device 10, the photoluminescent carbon dioxide sensitive probe 15 can include a glassy material. In some embodiments, the glassy material can include a silicate sol-gel. Non-limiting examples of silicates include orthosilicate, tetraalkyl orthosilicate, tetramethyl orthosilicate, tetraethyl orthosilicate, tetrapropyl orthosilicate, and tetrabutyl orthosilicate.

[0035] In the device 10, the photoluminescent carbon dioxide sensitive probe 15 can include a polyurethane material. In some embodiments, the polyurethane material includes a breathable film. In some embodiments, the polyurethane material includes a breathable foam. In some embodiments, the polyurethane material can be made from diisocyanate and polyol units. In some embodiments, the diisocyanate monomer can include an arylene diisocyanate. In some embodiments, the diisocyanate monomer can include an alkylene diisocyanate. Non-limiting examples of diisocyanates include phenylene diisocyanate, methylene diphenyl diisocyanate, hexamethylene diisocyanate, and dodecamethylene diisocyanate. In some embodiments, the polyol monomer can include an alkanoyl glycerol. Non-limiting examples of polyol monomers include octanoyl glycerol, decanoyl glycerol.

[0036] In the device 10, a photoluminescent carbon dioxide sensitive probe 15 measures tissue pCO 2In some embodiments, the sensing dye comprises a porphyrin molecule. In some embodiments, the sensing dye comprises a pH-sensitive fluorescent dye. In some embodiments, the pH-sensitive fluorescent dye comprises 8-hydroxy-1,3,6-pyrenetrisulfonic acid trisodium salt (HPTS). The sensing dye can comprise a pH-sensitive fluorescent dye in an anionic form and a quaternary ammonium cation. In some embodiments, the carbon dioxide sensitive probe comprises a phase transfer reagent embedded in a polymer matrix with the sensing dye. In some embodiments, the volume ratio (v / v) of the phase transfer reagent to the sensing dye is greater than 0% and less than or equal to 40%, or greater than 0% and less than or equal to 20%, or greater than 0% and less than or equal to 10%, or greater than or equal to 2% and less than or equal to 8%. The phase transfer reagent provides the water required to generate carbonic acid for protonating the pH-sensitive fluorescent dye. In some embodiments, the phase transfer reagent comprises an alkyl ammonium hydroxide. In some embodiments, the phase transfer reagent comprises tetraoctyl ammonium hydroxide. In some embodiments, the carbon dioxide sensitive probe has storage stability with no significant decrease in sensitivity when the carbon dioxide sensitive probe is stored in air under dark conditions for 7 days. The light emitted from the probe 15 can be filtered by a long pass filter covering the photodetector 40.

[0037] In some embodiments, the first photon source 20 may be a light emitting diode that emits light having a first peak wavelength (e.g., 405 nanometers, etc.). In some embodiments, the second photon source 30 may be a light emitting diode that emits light having a second peak wavelength (e.g., 470 nanometers, etc.). Photons from the photon sources 20, 30 may be filtered using a long pass filter.

[0038] The controller 50 may be a microcontroller or a system on chip (SoC) and may include a memory, which may be a non-transitory memory, capable of storing an executable program on the controller 50. In some embodiments, the controller 50 may store an analyte (e.g., carbon dioxide, etc.) calculation program capable of calculating an analyte (e.g., carbon dioxide, etc.) level adjacent the probe 15 from one or more electrical signals received from the photodetector 40. The controller 50 may also include an output, which may be a wire bundle. The output may be connected to an external interface, which may be used to display, store, and / or analyze results of the executable program of the device 10. The device 10 may include a display in electrical communication with the controller 50, the controller configured to execute a program stored in the controller to display the carbon dioxide level on the display and / or store values ​​of the carbon dioxide level at multiple times over a period of time. In other embodiments, the controller 50 may be configured to include a wireless output, which may perform wireless communication. Non-limiting examples of wireless communication that may be incorporated include Wi-Fi, Bluetooth, short range communication, cellular networks, radio frequency, etc. The controller 50 may include an on-board power source, such as a battery, that may provide power to the controller 50 to power the emission sources 20, 30, the photodetector 40, and the controller 50. In other embodiments, the controller 50 may include an electrical connection to an external power source, such as grid power, to power the emission sources 20, 30, the photodetector 40, and the controller 50.

[0039] The device 10 may be provided with a carbon dioxide permeable light scattering layer 60, which may comprise a silicone film containing a pigment. The pigment may be white. The light scattering layer 60 may backscatter the fluorescent emission to the photodetector 40. The white light scattering layer 60 may also act as a light separator to prevent external lighting from affecting the measurement results and to provide a reading that is independent of skin color. A heater and / or thermistor 80 may increase and / or measure the temperature of the light scattering layer 60. The device 10 may be provided with a transparent semi-permeable adhesive film (e.g., air impermeable) layer 70 to seal the room air out of the probe 15 and the light scattering layer 60, thereby allowing the material to absorb the skin pCO2. 2 Transdermal CO 2 The sensing device 10 is biocompatible because only the multi-layer film comes into contact with the skin. Approximately 99% of the total area of ​​the film corresponds to layer 70, a commercial medical grade skin adhesive, and the remaining 1% corresponds to light scattering layer 60, which is skin compatible and can also be inserted into tissue. The light scattering layer 60 prevents the probe 15 from coming into direct contact with the skin.

[0040] From the detailed description of each component of the device 10 above, a method of operation of the optical device 10 can be understood. Although the device 10 is particularly useful in detecting the concentration of carbon dioxide, the device 10 can be used in a method for detecting the concentration of other analytes. In one non-limiting example of a method of operating the optical device 10, the first photon source 20 is operated by the controller 50 to send photons to the probe 15 at a first wavelength, and the second photon source 30 is operated by the controller 50 to send photons to the probe 15 at a second wavelength different from the first wavelength. The photodetector 40 detects light emitted from the probe 15 when the first photon source 20 and the second photon source 30 send photons to the probe 15. The controller 50 executes a program for calculating the concentration of the analyte adjacent to the probe 15 based on the light emitted from the probe and detected by the photodetector 40. The program is stored in the controller 50. As shown in FIG. 4a, it may be advantageous to use an isosbestic point in the excitation spectrum of a sensing dye in detecting the analyte.

[0041] The controller 50 can execute a program stored in the controller 50 for calculating the concentration of the analyte adjacent to the probe 15 based on a normalization factor, algorithm, and / or calibration determined by sending photons to the probe at a first wavelength and accounting for brightness variations in the polymer matrix. The controller 50 is configured to execute a program stored in the controller 50 for calculating the concentration of the analyte adjacent to the probe based on a luminescence ratio (e.g., a fluorescence ratio, etc.) that provides a measure proportional to the concentration of the analyte adjacent to the probe, normalized using the normalization factor. The controller 50 can execute a program stored in the controller 50 for calculating the concentration of the analyte adjacent to the probe based on a calibration algorithm such that the device can report the concentration of the analyte adjacent to the probe via wired or wireless communication (e.g., USB or Wi-Fi, etc.). The calibration algorithm can use different calibration parameters depending on whether the derivative of the luminescence ratio (e.g., a fluorescence ratio, etc.) is positive or negative. In one embodiment of the device, the controller 50 can execute a program stored in the controller 50 for calculating the concentration of an analyte adjacent to the probe by integrating the emission spectrum excited at a first wavelength and a second wavelength. The controller 50 can execute a program stored in the controller 50 to calculate the concentration of an analyte adjacent to the probe modulated by a sinusoidal voltage, the intensity of the luminescence response (e.g., fluorescence response) of the sensing dye being defined as an amplitude extracted by multiple linear regression of the measured sinusoidal response. In some embodiments, the analyte can be selected from the group consisting of molecular oxygen, carbon dioxide, nitric oxide, analytes dissolved in plasma and tissue, and hydrogen ions. In some embodiments, the analyte can be selected from the group consisting of molecular oxygen, carbon dioxide, and mixtures thereof. In some embodiments, the analyte is carbon dioxide and the concentration of the analyte is pCO2. 2 It is calculated as pCO2 The physiological range of can be 0 to 50 mmHg.

[0042] <Example> The following examples are intended to illustrate and explain certain embodiments and aspects of the present invention in detail, and should not be construed as limiting the scope of the present invention. The descriptions in the examples are presented without being bound by theory.

[0043] <Outline of the Example> CO 2 Continuous monitoring of CO partial pressure is critical in the diagnosis and treatment of respiratory and cardiac diseases. 2 Despite great advances in sensor development, their practical application as portable or wearable devices for real-time monitoring remains underexplored. 2 Transcutaneous CO based on quantification of fluorescence of sensing films 2 We report the creation of a prototype wearable device for monitoring. The developed material is based on a fluorescent pH indicator (trisodium 8-hydroxy-1,3,6-pyrenetrisulfonate or HPTS) embedded in a hydrophobic polymer matrix. The fluorescence of the film is consistent with CO in the physiological range. 2 It is highly sensitive to changes in partial pressure, yet is photostable and humidity insensitive. The device and medical-grade film build on our previous work with transcutaneous oxygen sensing technology, which has been extensively clinically validated.

[0044] <1. Introduction> Carbon Dioxide (CO 2 ) plays various roles in the human body, such as motivating respiration, regulating blood pH, and the affinity of hemoglobin for oxygen [1]. 2 Partial pressure (pCO 2Monitoring of CO in arterial blood is of great importance for the medical diagnosis and treatment of human diseases, such as respiratory and metabolic disorders. For example, the suitability of spontaneous and mechanical ventilation is usually determined by the CO concentration in arterial blood. 2 [References 2, 3] However, the current "gold standard" method for obtaining such readings is based on the invasive technique of arterial blood gas sampling by placing an arterial line. [References 2, 3] Others include CO 2 Although non-invasive clinical alternatives for sensing exist, albeit indirectly, such technologies require further development and optimization to improve accuracy and integration into clinical workflow, as they have significant limitations or shortcomings. 2 The sensor measures the amount of CO exhaled at the end of exhalation. 2 It utilizes infrared absorption technology to measure levels of arterial pCO [4], but this technique requires the use of an optical cavity, which requires a large working volume of gas compared to other techniques [5], resulting in a lower arterial pCO 2 The accuracy of this technique for estimating pulmonary function is susceptible to sampling error and patient-related factors (e.g., age, patient position, pulmonary disease, etc.) [6, 7].

[0045] A noninvasive alternative to arterial gas sampling is skin surface pCO 2 There are means to monitor CO levels, which can reduce or eliminate the need for blood gas sampling, reducing the risk of developing patient comorbidities and improving patient comfort. 2 Transcutaneous monitoring of CO2 can be important, for example, to assess ventilation in neonates during the first month of life [8], but periodic arterial blood sampling for this purpose can be painful, does not provide continuous readings, and does not measure end-tidal CO2. 2 Monitoring pCO2 is not possible due to the small tidal volumes. 2 Arterial pCO 2There are many different sites that can be used for transcutaneous monitoring depending on the clinical situation, where the high correlation is typically in areas with thin skin and high blood vessels. Some examples include the earlobe [9], neck near the carotid artery

[10] , ventral area, front or side of chest

[11] , volar forearm, inner upper arm or inner thigh

[12] , foot

[13] , etc. However, current technology based on electrochemical sensors requires large and expensive equipment, long bedside calibration procedures, and immobility of the patient [3,14]. Thus, it is possible to incorporate a wearable device and to use a transcutaneous CO2 monitor, for example. 2 It can be very important to develop miniaturized sensors that can be used in a wide range of applications, such as continuous measurement of temperature and humidity.

[0046] Optical transdermal CO based on luminescent materials 2 The sensor can provide several advantages, such as CO 2 These sensors offer the potential for accurate detection of CO levels and great potential for miniaturization

[15] . 2 The pH-sensitive fluorescent dye trisodium 8-hydroxy-1,3,6-pyrenetrisulfonate (HPTS) was used to detect the presence of CO in a photodetector. 2 It is one of the most widely used in sensors [References 19, 20]. For skin-worn devices, it may be necessary to create sensors whose response does not change with changes in humidity [References 21, 22], which can vary widely depending on the climate and site [Reference 23]. To make HPTS molecules compatible with hydrophobic matrices, the dye is usually converted into its anionic form with a quaternary ammonium cation to form a lipophilic hydrated ion pair [References 16, 17, 19]. In addition, a phase transfer reagent (quaternary ammonium hydroxide) is required to be embedded in the support matrix along with the dye to help tune the sensitivity of the material and improve its stabilization. Thus, CO 2The performance of the sensor depends not only on the properties of the dye molecules, but also on the optical and physical properties of the support matrix.

[0047] Here we report the development of a polymer film embedded with HPTS-based ion pairs, which can be used to induce oxidative stress in vivo at physiological CO 2 We provide a highly breathable material with high intensity emission throughout the entire range. We have demonstrated that the material proposed above can be used to achieve transdermal CO 2 We developed a wireless, non-invasive, wearable prototype for continuous partial pressure monitoring.

[0048] 2. Materials and Methods 2.1.Materials HPTS, tetraoctylammonium bromide (TOABr), tetraoctylammonium hydroxide solution (20% dissolved in methanol) (TOAOH), hexadecyltrimethylammonium hydroxide solution (25% dissolved in methanol) (CTAOH), poly(methyl methacrylate) (PMMA) (approximately Mw 75,000), platinum(0)-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex solution, and sodium sulfate were purchased from Sigma-Aldrich. Cetyltrimethylammonium bromide (CTABr) was purchased from Fisher Scientific. Poly(propyl methacrylate) (PPMA) was purchased from Scientific Polymer Products (approximately Mw 150,000). White pigment concentrate (45-55% methylhydrosiloxane)-dimethylsiloxane copolymer (HMS) and cure retarder were purchased from Gelest. Glass microfiber was purchased from Whatman and medical grade adhesive film (Bioclusive) was purchased from McKesson.

[0049] 2.2. Synthesis of ion pairs 2.2.1.(HPTS) / (CTA) 3 Synthesis of The compound was synthesized by ion pairing HPTS with CTABr, similar to the method employed by Burke et al. [Reference 24]. 80 mg of CTABr was dissolved in 5 mL of ultrapure water at 50 °C and mixed with a solution of 40 mg of HPTS in 5 mL of ultrapure water. The product was obtained by vacuum filtration and subsequent washing with ultrapure water. The solid product was dried in an oven at 50 °C for 1 h.

[0050] 2.2.2.(HPTS) / (TOA) 4 Synthesis of (HPTS) / (TOA) 4 was prepared in the following manner

[25] : 20 mg of HPTS was dissolved in 5 mL of 0.01 M NaOH solution, along with 4-fold molar equivalent of TOABr (85 mg) in 5 mL of dichloromethane. These two solutions were then mixed, and the reaction mixture was stirred at room temperature for approximately 1 h. The mixture was placed in a separatory funnel, and the ion pair was extracted into the organic layer, which was then washed twice with 5 mL of 0.01 M NaOH solution. The organic layer was collected and the traces of water were dried over sodium sulfate. The solvent was removed by rotary evaporation, and the solid product was dried under high vacuum. The product yield was calculated to be approximately 60%.

[0051] 2.3.CO 2 Sensing film creation 2.3.1. Films for Spectral Characterization Filter paper was used as a substrate to prepare samples for spectral characterization because it is highly breathable and provides light scattering, increasing the amount of light collected by our spectrometer. A portion of the ion pair solution was added to 0.05 mg / μL PMMA or PPMA in dichloromethane, followed by different ratios of CTAOH or TOAOH in methanol and mixed thoroughly by vortexing. Next, 60 μM (HPTS) / (CTA) 3 and 240 or 480 μM (HPTS) / (TOA) 4and were added to the final solution. Approximately 15 μL of this solution was applied to a 5 mm diameter filter paper, placed on a solid surface, and allowed to dry overnight at room temperature in a hood.

[0052] 2.3.2. Multi-layer CO for wearables 2 Sensing Film As shown in Figures 1A and 1B, a multi-layer CO 2 The sensing film was fabricated following the approach of [Reference 26], by laminating a breathable white (scattering) silicone film as a carbon dioxide-transparent light-scattering layer 60, a PPMA-based sensitive film as a photoluminescent carbon dioxide-sensitive probe 15, and a transparent semi-permeable adhesive film (Bioclusive®, McKesson, New York, NY, USA) 70. This configuration reduces the volume and thickness, thereby improving the sensitivity of the skin to CO 2 A white silicone layer 60 / PPMA layer 15 combination was used in conjunction with the wearable device to allow for rapid equilibration to CO concentrations. The white silicone layer 60 / PPMA layer 15 combination was used in place of filter paper to backscatter the fluorescent emission to the photodiode 40 of the wearable device while minimizing the dead space volume. This white coating also doubles as a light separator to prevent external lighting from affecting the measurement results, allowing for a reading that is independent of skin color. A semi-transparent light-clear adhesive film 70 was used to filter the room air with CO 2 The sensing film and white silicone layer 60 can be sealed away, allowing the material to absorb the skin pCO 2 Transdermal CO 2 Our approach to sensing is biocompatible because only the multilayer film comes into contact with the skin. Approximately 99% of the total area of ​​the film corresponds to a commercial medical-grade skin adhesive, and the remaining 1% corresponds to a white silicone coating that is skin compatible

[26] and can also be inserted into tissue

[27] . The HPTS / PPMA disk 15 is prevented from coming into direct contact with the skin by the white coating 60.

[0053] To create PPMA-based films, (HPTS) / (TOA) 4 25 μL of the PPMA solution containing 1,000 μL of dimethylformamide (DMSO) and TOAOH was applied to an 8 mm diameter circular mold on a glass slide. The PPMA-based film was removed from the glass slide after drying in a hood for 30 min. The white light scattering layer was made according to the procedure in [Reference 26] with the following modifications. First, the silicone polymer component (100 μL) was mixed with a white pigment concentrate (1 g), followed by the addition of 3 drops of cure retarder and 1 drop of platinum catalyst. The mixture was applied to a flat surface and allowed to form a thin film before curing.

[0054] 2.4.Operation Principle optical CO 2 The most common principle of the sensor is based on the fluorescence change of a pH indicator due to protonation or deprotonation at different pH values ​​[References 17, 18]. In HPTS, it has been widely reported that the pH sensitivity of HPTS is caused by the OH group [Reference 19]. To facilitate the dissolution of the dye in hydrophobic polymers, lipophilic quaternary ammonium cations (Q+), known as phase transfer catalysts, are widely used, and pH indicator anions (D - ) to provide the water needed to generate carbonic acid to protonate the pH indicator dye.

[16] The general chemical principle can be described as follows:

number

[18] . 2 In the presence of CO, the dye anion with green fluorescence is converted to a protonated form, which does not fluoresce upon 470 nm excitation. 2 The reaction with is completely reversible. Furthermore, quaternary ammonium hydroxides are introduced to adjust the sensitivity of the material.

[0055] 2.5.Fluorescence spectrum measurement Fluorescence spectral measurements were obtained using an FLS1000 steady-state luminescence lifetime spectrometer equipped with a continuous xenon lamp (Xe2) (Edinburgh Instruments, Livingston, UK). The sample to be tested was placed in a holder fixed at an angle in a cuvette with a septum screw cap. N was introduced via a needle through the septum of the cuvette cap. 2 / CO 2 Changes in gas conditions were produced by flowing a gas mixture. This gas was also connected to a water bubbler, which altered the water vapor content of the mixture. Excitation spectra were acquired by setting the emission wavelength at 570 nm and scanning the excitation wavelength from 300 nm to 550 nm. Emission spectra were acquired by setting the excitation wavelength at 405 nm or 470 nm and scanning the emission wavelength from 500 nm to 700 nm. For emission spectra, the excitation light was filtered using a 495 nm long pass filter for all samples, which matches the filter of the wearable and therefore provides a "ground truth" measurement. Kinetic scanning was used to measure the photostability of several different materials over a period of 120 minutes under air conditions with a fixed excitation wavelength of 470 nm and a fixed emission wavelength of 520 nm. The power of the excitation light falling on the samples was set by adjusting the excitation bandwidth and was measured by an optical power meter (Thorlabs PM100D, Newton, NJ, USA). The rate of change in intensity was calculated as follows:

number

[0056] 2.6. Wearable Optical Devices Building on our previous work

[26] , we developed a small, lightweight, wearable prototype (see Figure 1A). 2 The fluorescence response of the sensing film was detected by exciting and detecting CO 2The device is based on a Wi-Fi enabled microcontroller board (Particle Photon), which drives custom low-power electronics (high-speed ADC chip, transimpedance amplifier, and signal conversion block). The intensity of the film's fluorescence response is detected via a PIN photodiode, which is sequentially excited by two high-power LEDs with peak wavelengths of 405 nm and 470 nm (see FIG. 1B). The LEDs are modulated with a sinusoidal voltage signal with f=1.6 kHz, and the CO excited by each LED is detected via a PIN photodiode. 2 The intensity of emission from the sensing film is defined as the amplitude of the measured sinusoidal response, which is extracted by multiple linear regression

[26] . The temperature of the film and the sensor head were sampled via a miniature thermistor. To avoid crosstalk between excitation and emission and to remove unwanted phosphorescence from the LED (see Figure 8), the LED excitation was filtered by a 500 nm short-pass filter constructed from two ultra-thin flexible optical notch filters (Edmund Optics), which were then blocked by a 500 nm long-pass filter covering the PIN photodiode by combining a flexible 405 nm long-pass filter (Edmund Optics) and an "amber" colored polyamide film (Kapton tape, 3M). CO 2 The sensing film was attached to the device's 3D-printed casing as a support structure using a thin, highly adhesive double-sided tape. The device was attached to the skin using a medical-grade film and an elastic band or strap, which was minimally tightened to prevent restriction of blood flow. 2 Data was collected using a Python

[28] script on a PC via the USB serial port to record a sinusoidal time series every time the device was sampled. For calibrated devices, the calibration algorithm (described below) was loaded into the firmware and the device was then able to transmit the CO signal to the display via USB or Wi-Fi. 2 Report the reading directly.

[0057] <3. Results and Discussion> 3.1. Optimization of sensing film composition Different dyes and polymer matrices are 2 To test their effect on the sensor sensitivity, the following materials cast on filter paper were investigated: (1) (HPTS) / (CTA) in PPMA 3 (2) (HPTS) / (TOA) in PPMA 4 (3) (HPTS) / (TOA) in PMMA 4 The filter paper was used as the support material for the spectral measurements because it is highly light scattering and does not change the sensing properties of the material. Figure 2, panel b, shows the change in the fluorescence spectrum when excited at 470 nm. 2 I as an index of sensor sensitivity N2 / I CO2 The ratio of I N2 The material is 100% N 2 corresponds to the peak intensity of the spectrum when exposed to the environment, and I CO2 The material is 100% CO 2 Corresponding to the peak intensity of the spectrum when exposed to the environment. (HPTS) / (CTA) embedded in PPMA 3 I N2 I CO2 It was found that the sensitivity was approximately 1.7 times higher than that of the (HPTS) / (TOA) sensing molecule. 4 When replaced by CO 2 The sensitivity increased dramatically to about 46. Furthermore, the (HPTS) / (TOA) embedded in PMMA 4 In the case of I N2 I CO2 These results suggest that the CO 2 It was shown that the sensitivity of the sensor can be tuned.

[0058] As shown above for sensors embedded in similar types of synthetic acrylate polymer matrices

[22] , the excitation spectrum can provide useful information on the distribution of the embedded sensor molecules and therefore the homogeneity of the resulting material. The chemical compatibility between the embedded dyes, which feature hydrophobic functional groups and alkyl chains, and the polymer matrix components can have a significant impact on the sensing performance [21, 22]. Here, (HPTS) / (TOA) 4 To further explore the differences in sensitivity observed between the materials tested, with +PPMA showing the highest sensitivity, excitation spectra were obtained and are shown in Figure 2, panel c. For all three materials, the dye reacted with CO 2 Under the conditions shown, the excitation maximum is at about 400 nm, and N 2 The excitation maximum was approximately 500 nm under CO conditions. 2 Or N 2 In the presence of (HPTS) / (CTA), different excitation wavelengths indicate the protonated or deprotonated forms of the dye. 3 CO 2 Under these conditions, only a small amount of the material is converted to the protonated form, which indicates that the CO 2 In contrast, the sensitivity of (HPTS) / (TOA) embedded in PPMA with TOAOH was low. 4 CO 2 Under these conditions, it is converted to a completely protonated form, which results in the observed significantly higher sensitivity. Furthermore, (HPTS) / (CTA) contained in PPMA together with CTAOH 3 The excitation spectrum of CO 2 Under conditions and N 2 Under both conditions, (HPTS) / (TOA) contained in PPMA together with TOAOH 4 It is clear that the width is much wider than that of the original. 16 TOAOH has four octyl (C 8) chains, which makes them more lipophilic overall. Taking these observations together, the (HPTS) / (CTA) 3 The most optimal materials for this purpose are those that combine a more lipophilic quaternary ammonium ion and phase transfer reagent (TOA+ / TOAOH) with a more hydrophobic polymer matrix with longer side chains (PPMA). Furthermore, the relatively long alkyl side chains of PPMA reduce the CO 2 This increases the diffusion and solubility of the gas, which allows the dye to be protonated more efficiently, and ultimately, the CO 2 Sensitivity is improved [Reference 29].

[0059] (HPTS) / (CTA) contained in PPMA together with CTAOH 3 The sensitivity of CO was much lower, so subsequent characterization focused only on the other two materials. Due to the water-mediated sensing chemistry, the moisture level of the gas can have a strong effect on the sensor performance, especially in applications such as respiratory gas analysis [Ref. 16]. Therefore, CO 2 The performance of the sensor was further evaluated under humid conditions (Figure 2, panel d). The presence of humidity increased the (HPTS) / (TOA) 4 CO 2 The (HPTS) / (TOA) ratio in PMMA+5% TOAOH did not affect the sensing sensitivity. 4 A corresponding increase in sensitivity of 1.9-fold was observed. It is possible that the longer alkyl side chains of PPMA increase its hydrophobicity compared to PMMA, improving its resistance to water. Finally, the PMMA-based materials showed good photostability during 2 h of continuous irradiation (Figure 2, panel e), whereas the (HPTS) / (TOA) in PPMA 4 Due to its high gas sensitivity and good water resistance, the (HPTS) / (TOA) in PPMA 4was the best candidate for final characterization.

[0060] 3.2. Effect of TOAOH ratio on sensitivity, photostability and dark stability After identifying the optimal combination of polymer matrix and sensing dye, different amounts of TOAOH were added to detect CO 2 The effect of this on sensing performance was investigated (see Figure 3). TOAOH found that the film made from this base-buffer-free solution was sensitive to CO 2 did not show sensitivity to CO 2 This is advantageous for sensing. In addition, the (HPTS) / (TOA) ratio in PPMA 4 It was found that the highest sensitivity was observed by adding 5% (v / v) TOAOH in methanol. Furthermore, the increase in the TOAOH ratio 2 The sensitivity decreased. A similar trend was observed when different dye concentrations were used (Figure 3, panel a).

[0061] To characterize the photostability of the material, the rate of change of intensity was obtained after 120 minutes of continuous irradiation in air, which, depending on the sampling rate, could be days or weeks longer than the wearable measurement time. 2 The acquisition of the concentration took only 200 ms per measurement. As shown in panel b of Figure 3, the (HPTS) / (TOA) concentration in PPMA 4 (240 μM) showed higher photostability at higher TOAOH ratios. 240 μM (HPTS) / (TOA) in PPMA 4 The intensity change rate of the sensing film prepared by was found to be 42% when 5% (v / v) TOAOH solution was added, 30% when 10% (v / v) TOAOH solution was added, and 24% when 20% (v / v) TOAOH solution was added. Furthermore, it was observed that the photostability of the dye at 480 μM was lower than that at 240 μM in the same support matrix. Increasing the TOAOH ratio can improve the photostability of the material, but the CO 2The sensitivity is low, and the (HPTS) / (TOA) ratio in PPMA is 4 The water resistance of CO2 is also reduced when 10% (v / v) TOAOH is added under humid conditions. 2 The sensitivity increased by 1.4-fold (Figure 3, panel c), whereas the sensitivity increased by only 1.1-fold when 5% (v / v) TOAOH was added (Figure 2, panel d). (HPTS) / (TOA) in PPMA with 5% and 10% TOAOH added 4 The storage stability of was tested over a period of 3 months. No significant loss of sensitivity was observed when the materials were stored under air (approximately 25°C) and dark conditions for 7 days, but after 3 months, both materials lost approximately 90% of their sensitivity (see Figure 6). The stability of the materials can be further improved by optimizing the storage conditions. Thus, the stability of the materials can be improved by optimizing the storage conditions. 2 Considering the sensitivity and optimized water resistance and light stability, (HPTS) / (TOA) in PPMA with 5% TOAOH was 4 Formulations of were tested in combination with wearable optical devices.

[0062] 3.3. Wearable Response and Calibration As mentioned above, the wearable collects the emission after excitation of the dye molecules at two different wavelengths, 405 nm and 470 nm, as also done in

[25] . The excitation spectrum of the HPTS / TOA-PPMA blend shows the emission spectrum of the CO 2 The film showed an isosbestic point at around 405 nm in the range (0-50 mmHg). This wavelength therefore serves as a normalization factor or ideal reference to account for variations in film brightness due to photobleaching, changes in the relative film / instrument position due to movement, etc. The second excitation wavelength used was 470 nm, which was used to measure the CO 2 A CO dependent emission was performed. This wavelength was also chosen to allow sufficient spectral separation between the excitation light (470 nm) and the dye emission (520-530 nm) to reduce LED leakage into the photodiode. Two excitation wavelengths were used, with excitation at 405 nm producing CO, the emission of interest. 2By effectively acting as an isosbestic point in the range, we can 2 A colorimetric measurement technique could be employed that gives a normalized index that is proportional to the concentration, without photobleaching phenomena, and that can be robust to motion artifacts in some ranges.

[0063] Therefore, the fluorescence ratio is defined as: R=I 405 / I 470 (3)

[0064] As a gold standard reference, the fluorescence spectrum of TOA / HPTS in PPMA in a multilayer film structure containing a white light scattering layer was acquired. Measurements were made by exciting at 405 nm and 470 nm and passing the emission through a 495 nm long pass filter to remove the excitation light from the collected light. To better compare the spectrometer measurements with the wearable readings, the I was calculated by integrating both the 405 nm excited spectrum and the 470 nm excited spectrum, rather than defining them as the fluorescence intensity at a particular wavelength. 405 and I 470 The integrated signal is smoother and better represents the signal measured by the wearable photodiode, which includes contributions from a wide range of wavelengths.

[0065] I as the integral of the fluorescence spectrum (with a long-pass filter to remove the excitation) 405,470 Definition of and ratio R=I 405 / I 470 I 405,470 should be similar to the trend observed when measured at a single wavelength.

[0066] To explain this, we propose the following assumption: λ 1 = 405 nm and λ 2 = Fluorescence spectrum excited at 470 nm is fλ 1 (λ) and fλ 2As can be seen from Figures 2 and 3, the shape of the spectrum (or the function of wavelength) is 2 Its amplitude is proportional to the excitation intensity (taking into account the quantum yield), and A λi exc ∝I λi exc (Conditional quantum yield is also required) and λ 2 = 470 nm, CO 2 For some function B=h(CO 2 ), we have the following:

number

number

number

number

[0067] Furthermore, calculating the ratio R using the integral results in a smoother function compared to using the intensity at a single wavelength, since the integral provides spectral averaging.

[0068] Panel b of Figure 4 shows the CO 2 Concentration (CO 2 and N 2 The fluorescence ratio R is plotted against the fluorescence intensity (calculated from a known mixture of gases). In this example, CO 2 PPMA is freely diffusing (CO 2 →PPMA) or forced diffusion through the white coating (CO 2 → white). Each gas mixture was flowed for 1 min and the spectrum was acquired afterwards. To better compare the trends at different temperatures, the ratio R was normalized between [0,1]. CO 2 When CO diffuses directly into the PPMA layer, 2 →PPMA), the sample shows a temperature-independent periodic response (start and end points coincide). 2 The slight delay in the response rate between the increase and decrease in CO has been previously reported to be due to the difference in the reaction rates of protonation and deprotonation [25, 30]. 2 Diffusion of (CO 2 The white coating (→white) was achieved by forcing all diffusion to occur through the white coating by adding a transparent but non-breathable backing layer. As shown in Figure 4, panel b, the white coating effectively prevented CO from escaping from the film at 25 °C. 2 This adds a substantial delay to the diffusion of CO, which is thought to be absent for oxygen

[26] . As can be seen from the wearable measurements in Figure 4, the breathability of the white film is significantly improved by increasing the temperature above 40 °C.

[0069] Measurements using the wearable device were performed in a sealed chamber with a controlled N gas proportioner (Gometrics) as shown in Figure 9. 2 and CO 2 A mixture of gases was delivered. pCO 2 is a commercially available non-dispersive infrared (NDIR) 2 Sensor (K-33 BLG, CO2 We measured the leakage in a temperature-dependent manner using a wearable "blank" film, which contains all the layers listed above except for the HPTS dye. All I used to calculate R 405 , I 470 The LED leakage was subtracted from the values. Panels c and d of Figure 4 show the change in the fluorescence ratio due to the same gas mixing sequence, measured at average temperatures of 25 °C and 44 °C. The lower temperature side is CO 2 A delay was observed with decreasing R, whereas no delay was observed at higher temperatures. Furthermore, the normalized R-pCO 2 The loops show the same trend at temperatures as shown in the spectral measurements in panel b of Figure 4. Panel f of Figure 4 plots the temperature dependence of the delay or lag between the wearable and the reference commercial sensor, obtained by cross-correlation of both signals, which shows that the CO 2 It can be clearly seen that the permeability to β-glucose is significantly increased. The dashed lines correspond to second order polynomial fits and are shown as a guide to the trends.

[0070] To calibrate the prototype and test cyclability, multiple 5-minute cycling sequences were programmed for the gas mixer. The measurements shown in Figure 5, panel a, were performed at an average temperature of 45 °C. The fluorescence ratio was measured at 100 °C for 90 min with CO 2 showed a sensitive and rapid response to changes in

[0071] According to the study by [Reference 25], pCO 2 The dependence of on the fluorescence ratio R follows the equation: pCO 2 =(A RB) / (-C R+D) The constants (A,B,C,D)>0 are obtained by combining different reaction rates and material parameters such as quantum yields (see [Ref. 25]). A script written for GNU Octave was used to fit the data in the figure to equation (4) [Ref. 31]. As shown in panel b of Figure 5, the model captures the trend well (R 2 =0.9518), quantitatively following the pCO readings of the reference sensor 2 This fit captures the average trend in the response, but as noted above, the estimated pCO 2 will always be an overestimate or an underestimate.

[0072] Given these data, we can propose a second model (Fit2 in Figure 5, panel b), which uses equation (4) but assumes that the derivative of the fluorescence ratio is positive (CO 2 Increased) or negative (CO 2 Different calibration parameters (A, B, C, D) are used depending on whether the model is over- or under-estimated (higher R 2 = 0.9808), as can be seen from panel c of Figure 5 and the residual plots in Figure 10, the reference pCO 2 Follow the readings closely. Reference sensor and our pCO 2 The standard deviation of the difference in estimates, σ, corroborates what is shown in Figure 5, Panel c, where σ Fit1 = 5.50mmHg and σ Fit2 = 2.73 mmHg (see Figure 11 for the Bland-Altman plot of the model). Furthermore, the Fit1 results were found to lag 37 seconds behind the reference reading, while Fit2 showed no lag.

[0073] In the study by [Reference 25], CO 2 propose a linear dependence with , where the fitting coefficients correspond to the ratio of the different reaction rates. The linear dependence does not capture the curvature of our data (see Figure 12), which is due to the fact that CO is distributed through several different layers of the film. 2This is most likely due to the added complexity of spreading.

[0074] Our R and pCO 2 The estimated sensitivity of the device, taking into account the simplified linear relationship between

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[0075] In summary, our colorimetric readings and calibration algorithms provide accurate pCO measurements without being affected by photobleaching during measurements over several hours. 2 It provides reliable readings and is compatible with benchtop commercial pCO 2 This can be achieved without deviation from the sensor. Depending on the application, longer monitoring times may be required and the use of the film may be limited by photobleaching of the HPTS. This can be easily solved by replacing the film regularly or by reducing the sampling frequency of the device to probe the film less frequently, which allows a high signal to be obtained with long wearing times.

[0076] <4. Conclusion> In this example, we used transdermal CO 2 To identify optimal materials for use in optical wearable devices for real-time monitoring of partial pressure, we aimed to investigate various HPTS-based ion pairs contained in different support matrices. We thoroughly characterized our materials, in particular the (HPTS) / (TOA) embedded in a PPMA matrix. 4 The characterization of the physiologic CO 2We found that our materials are highly sensitive within the range (0-50mmHg). The films are inherently insensitive to changes in humidity, which is important for a skin-worn device, and the films are photostable for extended periods of continuous sampling. We incorporated these materials into a medical-grade multi-layer film and tested it in an optical wearable device prototype to measure CO 2 We measured physiological CO 2 We proposed a detection and calibration method that utilizes the isosbestic points of the formulations in the physiological range. This method allows for the detection of CO2 within the physiological range while compensating for changes in fluorescence intensity due to photobleaching and motion artifacts. 2 The response speed of our film is faster than that of the commercially available NDIRCO 2 Our embodiment is comparable to a CO sensor, making it ideal for detecting physiological changes that occur on a minute-by-minute basis. 2 This indicates great potential for developing a commercially available, miniaturized, wearable device for monitoring partial pressure. Moreover, both the device and film structure based on our team's transcutaneous oxygenation measurement approach have already been clinically validated for noninvasively detecting changes in tissue oxygenation in several different physiological scenarios. Our previous work and the results presented here support the development of a dual-O 2 / CO 2 It presents an ideal platform for realizing wearable sensors.

[0077] Based on this example, CO can be produced over a wide temperature range to eliminate the need for heating for transdermal applications. 2One possible goal is to develop novel light scattering layers [Ref. 32] that are highly transparent to oxygen. Alternatively, our device can incorporate a small heating element to achieve temperatures of about 42-45°C, which are typically used in standard-of-care transcutaneous gas sensing devices. Based on this example, our technology can be refined to create wearable or portable devices in different form factors to detect oxygen at the skin surface [Ref. 26, 33], in the exhaled breath (capnography), and in arterial lines or muscle tissue [Ref. 27], O 2 and CO 2 It is conceivable that both can be monitored continuously.

[0078] Non-limiting advantageous features demonstrated in this embodiment include: -(HPTS) / (TOA) in a PPMA matrix that is mechanically robust and hydrophobic, making it insensitive to humidity 4 Ion pair formulations, - A wearable device that is a lightweight, standalone device, equipped with electronic devices such as microcontrollers, LEDs, PIN photodiodes, thermistors, amplifiers, ADC chips, and passive components (R,L,C), The use of multiple LEDs, each with a different excitation wavelength, allows for normalized or colorimetric luminescence, which provides robustness against motion artifacts, ambient light changes, photobleaching, etc., compared to purely intensity-based or colorimeter-based measurements, which is important in portable healthcare applications; - Hardware using low power and low voltage components, i.e. microcontroller for PC, LED for Xe lamp, PIN diode for CCD detector (DSLR camera), live readout for required post processing, continuous point measurement for image, etc. -As opposed to traditional devices that require a computer to take a reading, 2Hardware that is a wearable, standalone device that can take readings and send them to a computer or smartphone; - Disposable, single-use CO 2 The sensing film detects CO 2 Only a small volume of air (no dead space) is required to sample CO, thus allowing fast equilibration and readout, which eliminates the need for long optical paths. 2 NDIR CO requires a high volume of air to absorb enough infrared light at low concentrations 2 In contrast to sensors, products commercialized based on our embodiments can be made more compact. - the formulation is less sensitive to humidity, which is an advantage since water vapor in the air also affects the readings of infrared sensors; -The above measurement approach is 2 and O 2 It can also be easily combined with an optical oxygen sensor for dual readout of both.

[0079] <References> 1. Patel, S.; Miao, JH; Yetiskul, E.; Anokhin, A.; Majmundar, SH, Physiology, Carbon Dioxide Retention. In StatPearls; StatPearls Publishing LLC.: Treasure Island, FL, USA, 2022. 2. Casati, A.; Squicciarini, G.; Malagutti, G.; Baciarello, M.; Putzu, M.; Fanelli, A., Transcutaneous monitoring of partial pressure of carbon dioxide in the elderly patient: A prospective, clinical comparison with end-tidal monitoring. J. Clin. Anesth. 2006, 18, 436-440. 3. Umeda, A.; Ishizaka, M.; Ikeda, A.; Miyagawa, K.; Mochida, A.; Takeda, H.; Takeda, K.; Fukushi, I.; Okada, Y.; Gozal, D., Recent Insights into the Measurement of Carbon Dioxide Concentrations for Clinical Practice in Respiratory Medicine. Sensors 2021, 21, 5636. 4. Huttmann, S.E.; Windisch, W.; Storre, J.H., Techniques for the measurement and monitoring of carbon dioxide in the blood. Ann. Am. Thorac. Soc. 2014, 11, 645-652. 5. Tipparaju, V.V.; Mora, S.J.; Yu, J.; Tsow, F.; Xian, X., Wearable Transcutaneous CO2 Monitor Based on Miniaturized Nondispersive Infrared Sensor. IEEE Sens. J. 2021, 21, 17327-17334. 6. Berkenbosch, J.W.; Lam, J.; Burd, R.S.; Tobias, J.D., Noninvasive monitoring of carbon dioxide during mechanical ventilation in older children: End-tidal versus transcutaneous techniques. Anesth. Analg. 2001, 92, 1427-1431. 7. Casati, A.; Salvo, I.; Torri, G.; Calderini, E., Arterial to end-tidal carbon dioxide gradient and physiological dead space monitoring during general anaesthesia: Effects of patients’ position. Minerva Anestesiol. 1997, 63, 177-182. 8. Wyatt, J.; Edwards, A.; Cope, M.; Delpy, D.; McCormick, D.; Potter, A.; Reynolds, E., Response of cerebral blood volume to changes in arterial carbon dioxide tension in preterm and term infants. Pediatr. Res. 1991, 29, 553-557. 9. Senn, O.; Clarenbach, C.F.; Kaplan, V.; Maggiorini, M.; Bloch, K.E., Monitoring carbon dioxide tension and arterial oxygen saturation by a single earlobe sensor in patients with critical illness or sleep apnea. Chest 2005, 128, 1291-1296. 10. Bendjelid, K.; Schutz, N.; Stotz, M.; Gerard, I.; Suter, P.M.; Romand, J.A., Transcutaneous pCO2 monitoring in critically ill adults: Clinical evaluation of a new sensor. Crit. Care Med. 2005, 33, 2203-2206. 11. Nishiyama, T.; Nakamura, S.; Yamashita, K., Comparison of the transcutaneous oxygen and carbon dioxide tension in different electrode locations during general anaesthesia. Eur. J. Anaesthesiol. 2006, 23, 1049-1054. 12. Palmisano, B.W.; Severinghaus, J.W., Transcutaneous pCO2 and pO2: A multicenter study of accuracy. J. Clin. Monit. 1990, 6, 189-195. 13. Finzgar, M.; Frangez, H.B.; Cankar, K.; Frangez, I., Transcutaneous application of the gaseous CO2 for improvement of the microvascular function in patients with diabetic foot ulcers. Microvasc. Res. 2021, 133, 104100. 14. Dervieux, E.; Theron, M.; Uhring, W. Carbon Dioxide Sensing-Biomedical Applications to Human Subjects. Sensors 2021, 22, 188. 15. Escobedo, P.; Fernandez-Ramos, M.; Lopez-Ruiz, N.; Moyano-Rodriguez, O.; Martinez-Olmos, A.; Perez de Vargas-Sansalvador, I.; Carvajal, M.; Capitan-Vallvey, L.; Palma, A., Smart facemask for wireless CO2 monitoring. Nat. Commun. 2022, 13, 1-12. 16. Malins, C.; MacCraith, B.D., Dye-doped organically modified silica glass for fluorescence based carbon dioxide gas detection. Analyst 1998, 123, 2373-2376. 17. Wolfbeis, O.S.; Kovacs, B.; Goswami, K.; Klainer, S.M., Fiber-optic fluorescence carbon dioxide sensor for environmental monitoring. Microchim. Acta 1998, 129, 181-188. 18. Mills, A.; Chang, Q., Fluorescence plastic thin-film sensor for carbon dioxide. Analyst 1993, 118, 839-843. 19. Mills, A.; Yusufu, D., Highly CO2 sensitive extruded fluorescent plastic indicator film based on HPTS. Analyst 2016, 141, 999-1008. 20. Chu, C.S.; Syu, J.J., Optical sensor for dual sensing of oxygen and carbon dioxide based on sensing films coated on filter paper. Appl. Opt. 2017, 56, 1225-1231. 21. Roussakis, E.; Cascales, J.P.; Marks, H.L.; Li, X.; Grinstaff, M.; Evans, C.L., Humidity-Insensitive Tissue Oxygen Tension Sensing for Wearable Devices. Photochem. Photobiol. 2020, 96, 373-379. 22. Li, X.; Roussakis, E.; Cascales, J.P.; Marks, H.L.; Witthauer, L.; Evers, M.; Manstein, D.; Evans, C.L., Optimization of bright, highly flexible, and humidity insensitive porphyrin-based oxygen-sensing materials. J. Mater. Chem. C 2021, 9, 7555-7567. 23. Wang, X.d.;Wolfbeis, O.S., Optical methods for sensing and imaging oxygen: Materials, spectroscopies and applications. Chem. Soc. Rev. 2014, 43, 3666-3761. 24. Burke, C.S.; Markey, A.; Nooney, R.I.; Byrne, P.; McDonagh, C., Development of an optical sensor probe for the detection of dissolved carbon dioxide. Sens. Actuators B Chem. 2006, 119, 288-294. 25. Zhu, Q.; Aller, R.C.; Fan, Y., A new ratiometric, planar fluorosensor for measuring high resolution, two-dimensional pCO2 distributions in marine sediments. Mar. Chem. 2006, 101, 40-53. 26. Cascales, J.P.; Roussakis, E.; Witthauer, L.; Goss, A.; Li, X.; Chen, Y.; Marks, H.L.; Evans, C.L., Wearable device for remote monitoring of transcutaneous tissue oxygenation. Biomed. Opt. Express 2020, 11, 6989-7002. 27. Witthauer, L.; Cascales, J.P.; Roussakis, E.; Li, X.; Goss, A.; Chen, Y.; Evans, C.L., Portable oxygen-sensing device for the improved assessment of compartment syndrome and other hypoxia-related conditions. ACS Sens. 2020, 6, 43-53. 28. Van Rossum, G.; Drake, F.L., Jr., Python ReferenceManual; Centrum voorWiskunde en Informatica: Amsterdam, The Netherlands, 1995. 29. Pinnau, I.; Morisato, A.; He, Z., Influence of Side-Chain Length on the Gas Permeation Properties of Poly(2-alkylacetylenes). Macromolecules 2004, 37, 2823-2828. 30. Chu, C.S.; Lo, Y.L., Highly sensitive and linear optical fiber carbon dioxide sensor based on sol-gel matrix doped with silica particles and HPTS. Sens. Actuators B Chem. 2009, 143, 205-210. 31. Eaton, J.W.; Bateman, D.; Hauberg, S.; Wehbring, R., GNU Octave Version 3.8.1 Manual: A High-Level Interactive Language for Numerical Computations; CreateSpace Independent Publishing Platform: Scotts Valley, CA, USA, 2014; ISBN 1441413006. 32. Prefol, T.; Gain, O.; Sudre, G.; Gouanve, F.; Espuche, E., Development of Breathable Pebax(R) / PEG Films for Optimization of the Shelf-Life of Fresh Agri-Food Products. Membranes 2021, 11, 692. 33. Marks, H.; Bucknor, A.; Roussakis, E.; Nowell, N.; Kamali, P.; Cascales, JP; Kazei, D.; Lin, SJ; Evans, CL, A paintable phosphorescent bandage for postoperative tissue oxygen assessment in DIEP flap reconstruction. Sci. Adv. 2020, 6, eabd1061. The citation of any publication or reference should not be construed as an admission that it is prior art to the present invention.

[0080] Accordingly, the present invention provides devices, materials and methods for analyte monitoring, and more particularly for carbon dioxide monitoring.

[0081] In view of the principles and example embodiments described and illustrated herein, it can be appreciated that the arrangement and details of the example embodiments described above can be modified without departing from the principles. Also, while the above discussion focuses on a particular embodiment, other configurations are possible. In particular, even if the phrases "in one embodiment," "in another embodiment," "in another embodiment," "in some embodiments," and the like are used, such phrases are intended to generally refer to possible embodiments and are not intended to limit the invention to a particular embodiment configuration. The above phrases may refer to the same or different embodiments that can be combined into other embodiments in this application. In general, all embodiments referred to herein can be combined with any one or more of the other embodiments referred to herein, and any number of features of the different embodiments can be combined with each other.

[0082] Although the present invention has been described in some detail with reference to specific embodiments, it will be apparent to those skilled in the art that the present invention may be used in alternative embodiments to those described above, and that the above embodiments are intended to be illustrative and not limiting, and therefore the scope of the appended claims should not be limited to the description of the embodiments contained herein.

Claims

1. An apparatus for carbon dioxide monitoring, comprising: A photoluminescence carbon dioxide-sensitive probe comprising a polymer matrix and a sensing dye; A photon source configured to send photons to the probe; A photodetector configured to detect light emitted from the probe when the photon source sends photons to the probe; A controller in electrical communication with the photon source and the photodetector, the controller being configured to execute a program for calculating the level of carbon dioxide adjacent to the probe from the electrical signal received from the photodetector; And The program is stored in the controller; The polymer matrix includes a polymer selected from the group consisting of acrylate polymers, methacrylate polymers, polyurethane polymers, blends and copolymers thereof; An apparatus characterized by the above.

2. The polymer matrix includes a hydrophobic polymer, The apparatus according to Claim 1.

3. The polymer matrix includes a polymer selected from the group consisting of alkyl methacrylate polymers, The apparatus according to Claim 1.

4. The polymer matrix includes poly(propyl methacrylate) (PPMA), The apparatus according to Claim 1.

5. An apparatus for carbon dioxide monitoring, comprising: A photoluminescence carbon dioxide-sensitive probe comprising a polymer matrix and a sensing dye; A photon source configured to send photons to the probe; A photodetector configured to detect light emitted from the probe when the photon source sends photons to the probe; A carbon dioxide-permeable light direction conversion layer, the carbon dioxide-sensitive probe being disposed between the light direction conversion layer and the photodetector; A controller in electrical communication with the photon source and the photodetector, the controller being configured to execute a program for calculating the level of carbon dioxide adjacent to the probe from the electrical signal received from the photodetector; And The program is stored in the controller; An apparatus characterized by the above.

6. The light direction conversion layer can scatter light, The apparatus according to Claim 5.

7. The light direction conversion layer can reflect light, The apparatus according to Claim 5.

8. The light direction conversion layer includes a silicone film containing a pigment. The apparatus according to claim 5.

9. The pigment is white. The apparatus according to claim 8.

10. The apparatus further includes a heater for raising the temperature of the light direction conversion layer and / or the probe. The apparatus according to claim 5.

11. Photons having a wavelength longer than the wavelength necessary to excite the sensing dye among the photons from the photon source are filtered using a short-pass filter. The apparatus according to claim 5.

12. The light emitted from the photon source is filtered by a long-pass filter covering the photodetector. The apparatus according to claim 5.

13. The apparatus further includes a partially air-impermeable layer disposed between the carbon dioxide-sensitive probe and the photodetector. The apparatus according to claim 5.

14. The apparatus further includes a partially air-impermeable outer layer. The apparatus according to claim 5.

15. The apparatus further includes a completely air-impermeable outer layer. The apparatus according to claim 5.

16. The polymer matrix includes a polymer selected from the group consisting of an acrylate polymer, a methacrylate polymer, a silicate polymer and sol-gel, a polyurethane polymer, blends and copolymers thereof. The apparatus according to claim 5.

17. An apparatus for carbon dioxide monitoring, a fluorescence carbon dioxide-sensitive probe including a polymer matrix and a sensing dye, a first photon source configured to send photons to the probe at a first wavelength, a second photon source configured to send photons to the probe at a second wavelength different from the first wavelength, a photodetector configured to detect light emitted from the probe when the first photon source and the second photon source send photons to the probe, a controller in electrical communication with the first photon source, the second photon source, and the photodetector, the controller being configured to execute a program for calculating the level of carbon dioxide adjacent to the probe from an electrical signal received from the photodetector, comprising The program is stored in the controller An apparatus characterized by the above.

18. The isosbestic point of the excitation spectrum of the sensing dye is at the first wavelength. The apparatus according to claim 17.

19. By sending photons to the probe at the first wavelength, a normalization coefficient is provided to account for variations in the brightness of the polymer matrix. The apparatus according to claim 17. **Claim 20** The controller is configured to execute a program stored in the controller to calculate the level of carbon dioxide adjacent to the probe using a fluorescence ratio that provides an indicator proportional to the level of carbon dioxide adjacent to the probe and normalized using the normalization coefficient. The apparatus according to claim 19. **Claim 21** The controller is configured to execute a program stored in the controller to execute a calibration algorithm so that the apparatus can report the level of carbon dioxide adjacent to the probe via wired or wireless communication. The apparatus according to claim 20. **Claim 22** The calibration algorithm uses different calibration parameters depending on whether the derivative of the fluorescence ratio is positive or negative. The apparatus according to claim 21. **Claim 23** The controller is configured to execute a program stored in the controller to calculate the level of carbon dioxide adjacent to the probe by detecting the intensities of emissions excited at the first wavelength and the second wavelength. The apparatus according to claim 17. **Claim 24** The first photon source and the second photon source are modulated by a sinusoidal voltage. The intensity of the fluorescence response of the sensing dye is defined as the amplitude extracted by performing multiple linear regression on the measured sinusoidal response. The apparatus according to claim 17. **Claim 25** The photodetector detects the fluorescence response of the sensing dye that provides tissue pCO ２ ​ The apparatus according to any one of claims 1 to 24. **Claim 26** The sensing dye includes a pH-sensitive fluorescent dye. The apparatus according to any one of claims 1 to 24. **Claim 27** The pH-sensitive fluorescent dye includes trisodium 8-hydroxy-1,3,6-pyrenetrisulfonate (HPTS). The apparatus according to claim 26. **Claim 28** The sensing dye includes an anionic form of a pH-sensitive fluorescent dye and a quaternary ammonium cation, and the apparatus according to any one of claims 1 to 24. **Claim 29** The carbon dioxide-sensing probe includes a phase transfer reagent embedded in the polymer matrix together with the sensing dye. The device according to any one of claims 1 to 24.

30. The volume ratio (v / v) of the phase transfer reagent to the sensing dye is more than 0% and 40% or less. The device according to claim 29.

31. The volume ratio (v / v) of the phase transfer reagent to the sensing dye is more than 0% and 20% or less. The device according to claim 29.

32. The volume ratio (v / v) of the phase transfer reagent to the sensing dye is more than 0% and 10% or less. The device according to claim 29.

33. The volume ratio (v / v) of the phase transfer reagent to the sensing dye is 2% or more and 8% or less. The device according to claim 29.

34. The phase transfer reagent provides water necessary for generating carbonic acid for protonating the pH-sensitive fluorescent dye. The device according to claim 29.

35. The phase transfer reagent contains alkylammonium hydroxide. The device according to claim 29.

36. The phase transfer reagent contains tetraoctylammonium hydroxide. The device according to claim 29.

37. The carbon dioxide-sensitive probe has storage stability such that there is no significant decrease in sensitivity when the carbon dioxide-sensitive probe is stored in the atmosphere under dark conditions for at least 7 days. The device according to any one of claims 1 to 24.

38. The device is a transcutaneous optical device. The device according to any one of claims 1 to 24.

39. The device further includes a display in electrical communication with the controller, The controller is configured to execute the program stored in the controller to display the level of carbon dioxide on the display. The device according to any one of claims 1 to 24.

40. The controller is configured to execute the program stored in the controller to store the values of the levels of carbon dioxide at a plurality of times over a certain period. The device according to any one of claims 1 to 24.

41. The device further includes a display in electrical communication with the controller, The controller is configured to execute the program stored in the controller to display the values of the levels of carbon dioxide at a plurality of times over a certain period. The device according to any one of claims 1 to 24.

42. The device is insertable into a part of a patient's body. The device according to any one of claims 1 to 24.

43. Each of the photon sources, the photodetector, and the controller is disposed inside or outside the support structure. The device according to any one of claims 1 to 24.

44. It includes a band of a structure for fixing the support structure to a part of a patient's body. The device according to claim 43.

45. It includes a structure for fixing the support structure inside or outside the nose or mouth. The device according to claim 43.

46. It includes a structure for fixing the support structure inside or outside a nasal tube, a nasal cannula, a mask, a helmet, a tracheal tube, or a breathing device. The device according to claim 43.

47. It further includes an optical waveguide for sending photons from each of the photon sources to the probe. The device according to any one of claims 1 to 24.

48. The optical waveguide is an optical fiber. The device according to claim 47.

49. It further includes an optical waveguide for sending the light emitted from the probe to the photodetector. The device according to any one of claims 1 to 24.

50. The optical waveguide is an optical fiber. The device according to claim 49.

51. A kit for monitoring carbon dioxide, The device according to any one of claims 1 to 24, and One or more additional photoluminescent carbon dioxide-sensitive probes. A kit, characterized by comprising the above.

52. Each of the photoluminescent carbon dioxide-sensitive probes is provided in a package that does not transmit photons of a wavelength that causes the probe to emit light. The kit according to claim 51.

53. The package includes an indicator of the useful life of the photoluminescent carbon dioxide-sensitive probe. The kit according to claim 52.

54. A medical instrument, and The device according to any one of claims 1 to 24 attached to the medical instrument. A device, characterized by comprising the above.

55. A method for detecting the concentration of an analyte, (a) (i) A probe comprising a polymer matrix and a sensing dye, and (ii) A first photon source configured to send photons to the probe at a first wavelength. (iii)a second photon source configured to send photons to the probe at a second wavelength different from the first wavelength; (iv)a photodetector configured to detect light emitted from the probe when the first photon source and the second photon source send photons to the probe; providing an apparatus comprising; (b)calculating the concentration of the analyte adjacent to the probe based on the light emitted from the probe and detected by the photodetector and an isosbestic point at the first wavelength in the excitation spectrum of the sensing dye; A method characterized by comprising.

56. Step (b) further includes calculating the concentration of the analyte adjacent to the probe based on a normalization coefficient obtained by considering variations in the brightness of the polymer matrix by sending photons to the probe at the first wavelength. The method according to claim 55.

57. Step (b) further includes calculating the concentration of the analyte adjacent to the probe based on a luminescence ratio that provides an index proportional to the concentration of the analyte adjacent to the probe and is normalized using the normalization coefficient. The method according to claim 56.

58. Step (b) further includes calculating the concentration of the analyte adjacent to the probe based on a calibration algorithm such that the apparatus can report the concentration of the analyte adjacent to the probe via wired or wireless communication. The method according to claim 55.

59. The calibration algorithm uses different calibration parameters depending on whether the derivative of the luminescence ratio is positive or negative. The method according to claim 58.

60. Step (b) further includes calculating the concentration of the analyte adjacent to the probe by detecting the luminescence emission intensities excited at the first wavelength and the second wavelength. The method according to claim 55.

61. Step (b) further includes calculating the concentration of the analyte adjacent to the probe by modulating with a sinusoidal voltage, The intensity of the luminescence response of the sensing dye is defined as the amplitude extracted by performing multiple linear regression on the measured sinusoidal response. The method according to claim 55.

62. The object to be analyzed is selected from the group consisting of an oxygen molecule, carbon dioxide, nitric oxide, the object to be analyzed dissolved in plasma and tissue, and hydrogen ions. The method according to any one of claims 55 to 61. **Claim 63** The object to be analyzed is selected from the group consisting of an oxygen molecule, carbon dioxide, and a mixture thereof. The method according to any one of claims 55 to 61. **Claim 64** The object to be analyzed is carbon dioxide. The method according to any one of claims 55 to 61. **Claim 65** The concentration of the analysis target is pCO ２ calculated as The method according to any one of claims 55 to 61.

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