In intensive care units (ICU), vital signs and biomarkers of critically ill patients provide a set of operational parameters for doctors to assess the severity of organ dysfunction and optimize the supporting treatment. Among those organs monitored, the gut is less accessible, and its latent risk is not manageable. There is an emerging need for sensitive and easily measured biomarkers of early intestinal injury. Here, we found plasma fluorochromics can be used to assess the severity of intestinal injury using label-free methods of quantification. In acute mesenteric ischemia-reperusion animal models, ischemia-reperfusion damage can lead to multiple times increase of NADH, flavins, and porphyrin auto-fluorescence in blood. The intensity ratio between NADH and flavin fluorescence can capture early signatures before the occurrence of shock. Using liquid chromatography and mass spectroscopy, we confirmed that riboflavin is primarily responsible for the increased flavin fluorescence. Since endogenous riboflavin in humans is absorbed from the intestine, its increase in plasma validates its association with intestinal injury. In the future, blood fluorochrome detection could serve as a time-course monitoring modality in the emergency department or ICU to assess intestinal damage in various acute illnesses and critical care conditions.
For deep imaging depth and least invasiveness, people commonly use 1100-1300 nm femtosecond laser sources to perform label-free in vivo microscopy. The modalities include reflectance confocal, two & three photon fluorescence, and second & third harmonic generation microscopy. However, most of the laser sources are typically based on bulky oscillators, which are sensitive to environment conditions and less stable for routine clinical use. In contrast, fiber-based lasers have simpler cavity design and potentially compact size for movable use. In this presentation, we demonstrate a fiber-based 1150 nm femtosecond laser source, with 6.5 nJ pulse energy, 86 fs pulse-width, and 11.25 MHz pulse repetition rate. It was achieved by a Bismuth Borate (BIBO) or Magnesium-doped periodically poled Lithium Niobate (MgO:PPLN) mediated frequency doubling of the 2300 nm solitons, generated from an excitation of 1550 nm Er:fiber femtosecond laser pulses on a large mode area photonic crystal fiber. Combined with a laser scanned microscope and a home-build data acquisition card, we achieve a pulse-per-pixel harmonic generation microscopy in vivo at a 30 Hz frame rate. In the future, this solution is potential to be used for label-free clinical virtual optical biopsy.
Harmonic generation microscopy (HGM) has become one unique tool of optical virtual biopsy for the diagnosis of cancer and the in vivo cytometry of leukocytes. Without labeling, HGM can reveal the submicron features of tissues and cells in vivo. For deep imaging depth and minimal invasiveness, people commonly adopt 1100- to 1300-nm femtosecond laser sources. However, those lasers are typically based on bulky oscillators whose performances are sensitive to environmental conditions. We demonstrate a fiber-based 1150-nm femtosecond laser source, with 6.5-nJ pulse energy, 86-fs pulse width, and 11.25-MHz pulse repetition rate. It was obtained by a bismuth borate or magnesium-doped periodically poled lithium niobate (MgO:PPLN) mediated frequency doubling of the 2300-nm solitons, generated from an excitation of 1550-nm femtosecond pulses on a large mode area photonic crystal fiber. Combined with a home-built laser scanned microscope and a tailor-made frame grabber, we achieve a pulse-per-pixel HGM imaging in vivo at a 30-Hz frame rate. This integrated solution has the potential to be developed as a stable HGM system for routine clinical use.
In recent years, it has been suggested that epicardial adipose tissue (EAT) plays an important role in development of coronary artery disease (CAD) and diabetes mellitus (DM). In this article, we used two-photon fluoresce microscope to measure the fluorescence metabolic image of EAT, which obtained from the patient with/without CAD/DM. We used 740nm and 890nm infrared light to excite the auto-fluorescence of metabolic molecules NADH and FAD respectively. We collected the fluorescence signal at wavelength 450nm to 500nm and 500nm to 550nm to obtain the metabolic image. Through the image, we computed the redox ratio (NADH/FAD) by analyzing the intensity. The preliminary result showed that the redox ratio increase in the patients with CAD. It indicates EAT adipocytes of patient with CAD have decreased cellular metabolic activity. But there were no significant variation of redox ratio in the patients with DM.
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