Lung Diseases; Scientists spanning several disciplines have come up with an optical fiber based probe much thinner than a hair, but which carries 19 sensors to measure changes in oxygen and pH deep in the lung. This flexible optical probe provides rapid and accurate measurements for deep body sensing to within 0.02 pH units and 0.6 mg/L for pH and oxygen respectively but still has space for more sensors. The research is report in the current issue of the journal Scientific Reports.
The Lung Diseases
Current knowledge of human physiology comes mostly from animal models. Sensing in humans is far more difficult or impossible; so because the technology require is invasive, or simply not yet available. The importance of this novel probe lies in its scope to enormously expand in vivo sensing; so to a host of currently inaccessible areas of the human body; so extending the knowledge of body function in both health and disease.
The current study use an ovine lung model which was supply with oxygen and nutritional fluid through ventilation and perfusion channels. Lung diseases are leading causes of both disability and death today. Despite the progress made, its pathogenesis in conditions like lung trauma or pneumonia is unclear. The new probe could help us understand lung disease and its treatment much better.
A host of optical fiber sensors already exist for pH and oxygen; so sensing that use sol-gel or polymer coatings to hold the sensing molecules; so like dyes or nano/microsphere particles to the fiber facet. This type of coupling leads to imprecise deposition, slower response times, and reduce accuracy and range of sensing.
A more recent dual sensing probe use sol-gel or hydrogel coating to deposit both pH; also oxygen sensing microspheres on the same optical fiber, but still had relatively slow response times. The specially design multicore probe ensures robust sensing; but avoids common issues with fluorescent probes, such as photo bleaching and variation of laser pump power.
The fluorescent excitation
This ultra dense packing gives rise to fluorescent excitation; so with subsequent energy transfer to neighbors, resulting in a fluorescence response that is inversely proportional to the pH. The emission behavior returns to the expect pattern at standard loading. This unexpected phenomenon, which has never report before; so greatly boosts the sensor’s performance.
Ratiometric pH sensing is achieve using a FRET pair as fluorophores. Its components are excited by slightly different wave lengths. This causes a more complex, stable and reliable response to pH changes than a single fluorescent response. The oxygen sensing is by a palladium-porphyrin complex that shows inverse fluorescence as oxygen levels increase. The excitation wavelength was chosen to minimize background fluorescence which could confuse the sensors.
Next, the researchers plan to enclose the fiber sensor assembly in bio compatible materials for testing in various clinical scenarios. This is made simpler by the fact that it can withstand standard sterilization procedures. Researcher Michael Tanner says: “These new methods, if taken to clinic, will lead to novel insights in disease biology. Our aim now is to expand the number of unique sensors on this miniaturised platform to provide even more information.”