non-invasive-optical-measurement-cerebral-metabolism-hemodynamics

Non-invasive Optical Measurement of Cerebral Metabolism and Hemodynamics in Infants

Perinatal brain injury remains a significant cause of infant mortality  and morbidity, but there is not yet an effective bedside tool that can  accurately ...

Frequency-domain fluorescence spectroscopy using 280-nm and 300-nm light-emitting diodes: measurement of proteins and protein-related fluorophores.

Gliadin proteins are primarily responsible for celiac disease. As gliadin is a complex mixture of proteins difficult to solubilize and to extract from food, it is difficult to develop an assay capable of accurate quantization of gliadin in food for celiac patients. In this work, we present an advanced fluorescence assay for the detection of traces of gliadin in food. The described assay is based on measurement of the fluctuations of fluorescein-labeled gliadin peptides (GP) in a focused laser beam in the absence and in the presence of anti-GP antibodies. A competitive assay based on the utilization of unlabeled GP was developed. The obtained results indicate that the combination of high-avidity IgG antibodies together with the innovative fluorescence immunoassay strategy resulted in a gluten detection limit of 0.006 ppm, which it is much lower than the values reported in the literature.

Fluorescence correlation spectroscopy assay for gliadin in food.

Frequency-domain near-infrared spectro-imaging offers significant advantages over the continuous-wave method in human brain applications. However, the drawback of existing instruments is a low signal-to-noise ratio for measured phase and modulation depth changes caused by cerebral activation. In this paper we show that in the case of the geometry specific for the activated area in the human brain, the SNR can be significantly improved by increasing the modulation frequency. We present the results of two studies: one performed experimentally using a subnanosecond pulsed light source and a spherical absorbing inhomogeneity immersed in a highly scattering solution, and the other performed numerically using Monte Carlo simulations of light transport in an MRI based digital phantom of the adult human head. We show that changes caused by the absorbing inhomogeneity in both phase and modulation depth increase with frequency and reach maximum values at frequencies between 400 and 1400 MHz, depending on the particular source-detector distance. We also show that for the human head geometry an increase of the modulation frequency from 100 to 500 MHz can increase the phase SNR 2-3 times, and the modulation depth SNR up to 10 times.

Optimization of the signal-to-noise ratio of frequency-domain instrumentation for near-infrared spectro-imaging of the human brain.

We first report on the development of new microscope means that reduce background contributions in fluorescence fluctuation methods: i) excitation shutter, ii) electronic switches, and iii) early and late time-gating. The elements allow for measuring molecules at low analyte concentrations. We first found conditions of early and late time-gating with time-correlated single-photon counting that made the fluorescence signal as bright as possible compared with the fluctuations in the background count rate in a diffraction-limited optical set-up. We measured about a 140-fold increase in the amplitude of autocorrelated fluorescence fluctuations at the lowest analyte concentration of about 15 pM, which gave a signal-to-background advantage of more than two-orders of magnitude. The results of this original article pave the way for single-molecule detection in solution and in live cells without immobilization or hydrodynamic/electrokinetic focusing at longer observation times than are currently available.

Article	Year
Frequency-domain fluorescence spectroscopy using 280-nm and 300-nm light-emitting diodes: measurement of proteins and protein-related fluorophores. Analytical biochemistry\| PubMed ID: 15950917	2005
Fluorescence correlation spectroscopy assay for gliadin in food. Analytical chemistry\| PubMed ID: 17503770	2007
Optimization of the signal-to-noise ratio of frequency-domain instrumentation for near-infrared spectro-imaging of the human brain. Optics express\| PubMed ID: 19471386	2003
Reducing background contributions in fluorescence fluctuation time-traces for single-molecule measurements in solution. Current pharmaceutical biotechnology\| PubMed ID: 19689322	2009
Current pharmaceutical biotechnology\| PubMed ID: 20497113	2010
Quantitative spectroscopic determination of hemoglobin concentration and saturation in a turbid medium: analysis of the effect of water absorption. Journal of biomedical optics\| PubMed ID: 23014867	1997

Beniamino Barbieri

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