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Lipoprotein Determination in Single Cells by Near-Infrared Spectromicrography

Jenni Moses
Jennifer L. Moses

A near-infrared InSb focal plane array camera is being used to collect images of human carotid plaques during carotid endarterectomies. The excised plaques are later analyzed for lipoprotein content by ultracentrifugation and gel electrophoresis. The results from the electrophoresis indicate a correlation between the size of atherosclerotic plaque and the concentration of a 93 kD protein in the plaque, and plaque size is correlated to incidence of stroke. Experiments now underway are designed to test two hypotheses:
(1) that a near- infrared PtSi CCD camera provides better in vivo spatial resolution and more functional pixels on a plaque image than the InSb focal plane array camera, with sufficient signal-to-noise ratio for macroscopic lipoprotein determination in individual plaque cells.
(2) that the oxLDL 93kD protein is transported into plaque cells from serum by infiltrating macrophages.
The InSb camera typically has more failed pixels and has a lower spatial resolution than the PtSi camera. The SEE and SEP for analytes using the InSb camera and PtSi camera have been compared in the laboratory using prepared samples to create a calibration curve. The increased spatial resolution of the PtSi camera makes it easier to select spectra from microscopic sections made from the excised plaque. The spectra collected by attaching the PtSi camera to a microscope are also compared to a visual picture of a stained slide from the same plaque for reference. The near-IR microscope shown below uses an InSb focal plane array camera and can be used with either blackbody light sources with interference filters or a Nd:YAG-pumped KTP/OPO tunable near-IR laser system.

near-IR microscope

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