Method measuring oxygen tension and transport within subcutaneous devices

Cellular therapies hold promise to replace the implantation of whole organs in the treatment of disease. For most cell types, in vivo viability depends on oxygen delivery to avoid the toxic effects of hypoxia. A promising approach is the in situ vascularization of implantable devices which can mediate hypoxia and improve both the lifetime and utility of implanted cells and tissues. Although mathematical models and bulk measurements of oxygenation in surrounding tissue have been used to estimate oxygenation within devices, such estimates are insufficient in determining if supplied oxygen is sufficient for the entire thickness of the implanted cells and tissues. We have developed a technique in which oxygen-sensitive microparticles (OSMs) are incorporated into the volume of subcutaneously implantable devices. Oxygen partial pressure within these devices can be measured directly in vivo by an optical probe placed on the skin surface. As validation, OSMs have been incorporated into alginate beads, commonly used as immunoisolation devices to encapsulate pancreatic islet cells. Alginate beads were implanted into the subcutaneous space of Sprague–Dawley rats. Oxygen transport through beads was characterized from dynamic OSM signals in response to changes in inhaled oxygen. Changes in oxygen dynamics over days demonstrate the utility of our technology

Transdermal Micro-Implantable Metabolite Sensor with Optical Communication

Early warning of impending shock, organ failure, and hypoperfusion are critical to implementing an effective treatment approach in emergency medicine. However, vital signs often do not change until a patient is already in critical condition, and it is too late to intervene effectively. Blood lactate levels have been suggested as a more sensitive parameter for measuring a patient's condition, because lactate levels change early during life-threatening situations such as hemorrhagic shock and sepsis. In fact, frequent serial measurements of lactate over the course of treatment that guide a goal-directed therapy have been shown to decrease mortality rates significantly. Unfortunately, lactate guided treatment is rarely practiced due to the logistical burden of taking serial measurements using point-of-care devices or as part of a lab panel. To address this unmet need, a microchip device to continuously monitor lactate for the duration of inpatient care has been developed. It was found that the microchip could be made such that it is implanted just under the skin surface and an optical probe is used to measure the reported response on the skin surface by passing and receiving light through skin. The microchip responds to changes in lactate concentration by utilizing an enzyme with high specificity and selectivity for lactate. A molecule that reports the enzyme-mediated response is embedded in the microchip. Manufacturing techniques have been developed to reproduce the microchips effectively, and the chips have been tested for use and accuracy in rabbit models of cyanide poisoning, where lactate levels change rapidly. The microchip platform has the ability to be loaded with alternate chemistries for detecting other bio-analytes, such as glucose, oxygen, CO2, pH, etc. An optical probe suitable for passing light through skin and receiving the microchip light emission for use in animal studies was created along with software to analyze the emission signals. When calibrations of implanted chip response to lactate were compared to gold-standard blood lactate measurements across the physiological and pathological range in 12 separate models of cyanide poisoning in rabbits the average error was 11%

Transdermal Micro-Implantable Metabolite Sensor with Optical Communication

Early warning of impending shock, organ failure, and hypoperfusion are critical to implementing an effective treatment approach in emergency medicine. However, vital signs often do not change until a patient is already in critical condition, and it is too late to intervene effectively. Blood lactate levels have been suggested as a more sensitive parameter for measuring a patient's condition, because lactate levels change early during life-threatening situations such as hemorrhagic shock and sepsis. In fact, frequent serial measurements of lactate over the course of treatment that guide a goal-directed therapy have been shown to decrease mortality rates significantly. Unfortunately, lactate guided treatment is rarely practiced due to the logistical burden of taking serial measurements using point-of-care devices or as part of a lab panel. To address this unmet need, a microchip device to continuously monitor lactate for the duration of inpatient care has been developed. It was found that the microchip could be made such that it is implanted just under the skin surface and an optical probe is used to measure the reported response on the skin surface by passing and receiving light through skin. The microchip responds to changes in lactate concentration by utilizing an enzyme with high specificity and selectivity for lactate. A molecule that reports the enzyme-mediated response is embedded in the microchip. Manufacturing techniques have been developed to reproduce the microchips effectively, and the chips have been tested for use and accuracy in rabbit models of cyanide poisoning, where lactate levels change rapidly. The microchip platform has the ability to be loaded with alternate chemistries for detecting other bio-analytes, such as glucose, oxygen, CO2, pH, etc. An optical probe suitable for passing light through skin and receiving the microchip light emission for use in animal studies was created along with software to analyze the emission signals. When calibrations of implanted chip response to lactate were compared to gold-standard blood lactate measurements across the physiological and pathological range in 12 separate models of cyanide poisoning in rabbits the average error was 11%

Method measuring oxygen tension and transport within subcutaneous devices.

Cellular therapies hold promise to replace the implantation of whole organs in the treatment of disease. For most cell types, in vivo viability depends on oxygen delivery to avoid the toxic effects of hypoxia. A promising approach is the in situ vascularization of implantable devices which can mediate hypoxia and improve both the lifetime and utility of implanted cells and tissues. Although mathematical models and bulk measurements of oxygenation in surrounding tissue have been used to estimate oxygenation within devices, such estimates are insufficient in determining if supplied oxygen is sufficient for the entire thickness of the implanted cells and tissues. We have developed a technique in which oxygen-sensitive microparticles (OSMs) are incorporated into the volume of subcutaneously implantable devices. Oxygen partial pressure within these devices can be measured directly in vivo by an optical probe placed on the skin surface. As validation, OSMs have been incorporated into alginate beads, commonly used as immunoisolation devices to encapsulate pancreatic islet cells. Alginate beads were implanted into the subcutaneous space of Sprague–Dawley rats. Oxygen transport through beads was characterized from dynamic OSM signals in response to changes in inhaled oxygen. Changes in oxygen dynamics over days demonstrate the utility of our technology

Lens-free computational imaging of capillary morphogenesis within three-dimensional substrates.

Endothelial cells cultured in three-dimensional (3-D) extracellular matrices spontaneously form microvessels in response to soluble and matrix-bound factors. Such cultures are common for the study of angiogenesis and may find widespread use in drug discovery. Vascular networks are imaged over weeks to measure the distribution of vessel morphogenic parameters. Measurements require micron-scale spatial resolution, which for light microscopy comes at the cost of limited field-of-view (FOV) and shallow depth-of-focus (DOF). Small FOVs and DOFs necessitate lateral and axial mechanical scanning, thus limiting imaging throughput. We present a lens-free holographic on-chip microscopy technique to rapidly image microvessels within a Petri dish over a large volume without any mechanical scanning. This on-chip method uses partially coherent illumination and a CMOS sensor to record in-line holographic images of the sample. For digital reconstruction of the measured holograms, we implement a multiheight phase recovery method to obtain phase images of capillary morphogenesis over a large FOV (24 mm2) with ≈ 1.5 μm spatial resolution. On average, measured capillary length in our method was within approximately 2% of lengths measured using a 10 × microscope objective. These results suggest lens-free on-chip imaging is a useful toolset for high-throughput monitoring and quantitative analysis of microvascular 3-D networks

Lens-free computational imaging of capillary morphogenesis within three-dimensional substrates.

Endothelial cells cultured in three-dimensional (3-D) extracellular matrices spontaneously form microvessels in response to soluble and matrix-bound factors. Such cultures are common for the study of angiogenesis and may find widespread use in drug discovery. Vascular networks are imaged over weeks to measure the distribution of vessel morphogenic parameters. Measurements require micron-scale spatial resolution, which for light microscopy comes at the cost of limited field-of-view (FOV) and shallow depth-of-focus (DOF). Small FOVs and DOFs necessitate lateral and axial mechanical scanning, thus limiting imaging throughput. We present a lens-free holographic on-chip microscopy technique to rapidly image microvessels within a Petri dish over a large volume without any mechanical scanning. This on-chip method uses partially coherent illumination and a CMOS sensor to record in-line holographic images of the sample. For digital reconstruction of the measured holograms, we implement a multiheight phase recovery method to obtain phase images of capillary morphogenesis over a large FOV (24 mm2) with ≈ 1.5 μm spatial resolution. On average, measured capillary length in our method was within approximately 2% of lengths measured using a 10 × microscope objective. These results suggest lens-free on-chip imaging is a useful toolset for high-throughput monitoring and quantitative analysis of microvascular 3-D networks

Lens-free computational imaging of capillary morphogenesis within three-dimensional substrates

Endothelial cells cultured in three-dimensional (3-D) extracellular matrices spontaneously form microvessels in response to soluble and matrix-bound factors. Such cultures are common for the study of angiogenesis and may find widespread use in drug discovery. Vascular networks are imaged over weeks to measure the distribution of vessel morphogenic parameters. Measurements require micron-scale spatial resolution, which for light microscopy comes at the cost of limited field-of-view (FOV) and shallow depth-of-focus (DOF). Small FOVs and DOFs necessitate lateral and axial mechanical scanning, thus limiting imaging throughput. We present a lens-free holographic on-chip microscopy technique to rapidly image microvessels within a Petri dish over a large volume without any mechanical scanning. This on-chip method uses partially coherent illumination and a CMOS sensor to record in-line holographic images of the sample. For digital reconstruction of the measured holograms, we implement a multiheight phase recovery method to obtain phase images of capillary morphogenesis over a large FOV ([Formula: see text]) with [Formula: see text] spatial resolution. On average, measured capillary length in our method was within approximately 2% of lengths measured using a [Formula: see text] microscope objective. These results suggest lens-free on-chip imaging is a useful toolset for high-throughput monitoring and quantitative analysis of microvascular 3-D networks

A bench-top model of middle ear effusion diagnosed with optical tympanometry.

ObjectivesTo assess the validity of a bench-top model of an optical tympanometry device to diagnose in vitro model of middle ear effusion (MEE).Methods and materialsWe illuminated an in vitro model of ear canal and tympanic membrane with broadband light and relayed remitted light to a spectrometer system. We then used our proprietary algorithm to extract spectral features that, together with our logistic regression classifiers, led us to calculate a set of simplified indices related to different middle ear states. Our model included a glass vial covered with a porcine submucosa (representing the tympanic membrane) and filled with air, water, or milk solution (representing different MEE), and a set of cover-glass slips filled with either blood (representing erythema) or cerumen. By interchanging fluid types and cover-glass slips, we made measurements on combinations corresponding to normal healthy ear and purulent or serous MEE.ResultsEach simulated condition had a distinct spectral profile, which was then employed by our algorithm to discriminate clean and cerumen-covered purulent and serous MEE. Two logistic purulent and serous MEE classifiers correctly classified all in vitro middle ear states with 100% accuracy assessed by leave-one-out and k-fold cross validation.ConclusionsThis proof-of-concept in vitro study addressed an unmet need by introducing a device that easily and accurately can assess middle ear effusion. Future in vivo studies aimed at collecting data from clinical settings are warranted to further elucidate the validity of the technology in diagnosing pediatric acute otitis media