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A minimally-invasive diagnosis of pancreatic cancer is accomplished by obtaining a fine needle aspirate and observing
the cell preparations under conventional optical microscopy. As an unavoidable artifact, native tissue architecture is lost,
making definite diagnosis of malignancy, or invasive neoplasm, impossible. One solution is the preparation of core
biopsies (CBs) within a microfluidic device that are subsequently imaged in 3D. In this paper, porcine pancreas CBs (L
= 1-2 cm, D = 0.4-2.0 mm) were formalin-fixed, stained and optically cleared (FocusClear®). In brightfield at 40x, light
transmission through the ordinarily opaque CBs was increased 5-15x, and internal islet structures were easily identified
250-300 μm beneath the tissue surface. Typically, specimen preparation is time intensive and requires precise handling
since CBs are delicate; thus, fixative, absorptive stain and FocusClear® diffusion were done slowly and manually. To
significantly speed up tissue processing, we developed a microfluidic device consisting of both a main channel (L = 12.5
cm, D = 1.415 mm) with a circular cross section used for fixing and transporting the CB and an intersecting U-channel
employed for staining. Space between the CB and channel wall provided a key feature not traditionally employed in
microfluidic devices, such that at low flow rates (5-10 mL/min) CBs were fixed and stained while the specimen
remained stationary. By switching quickly to higher flow rates (15-20 mL/min), we could precisely overcome adhesion
and transport the specimen within the channel towards the imaging platform for 3D pathology.
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