Abstract
Molecular technologies in cancer diagnosis require a fresh and frozen tissue, which is obtained by means of snap-freezing. Currently, coolants such as solid carbon dioxide and liquid nitrogen are used to preserve good morphology of the tissue. Using these coolants, snap freezing of tissues for diagnostic and research purposes is often time consuming, laborious, even hazardous and not user friendly. For that reason snap-freezing is not routinely applied at the location of biopsy acquisition. Furthermore, the influence of optimal cooling rate and cold sink temperature on the viability of the cells is not well known. In this paper, a snap-freezing apparatus powered by a small cryocooler is presented that will allow bio-medical research of tissue freezing methods and is safe to use in a hospital. To benchmark this apparatus, cooldown of a standard aluminum cryo-vial in liquid nitrogen is measured and the cooling rate is about -25 K/s between 295 K and 120 K. Sufficient cooling rate is obtained by a forced convective helium gas flow through a gap formed between the cryo-vial and a cold surface and is therefore chosen as the preferred cooling method. A conceptual design of the snap-apparatus with forced flow is discussed in this paper.
Highlights
Worldwide cancer is the third most common cause of death, one of eight deaths is cancer related [1]
The FFPE procedure takes time for fixation, for a rapid intra-operative diagnosis tissue samples are generally frozen in a cryogenic coolant such as solid carbon dioxide, liquid nitrogen or liquid isopentance cooled with liquid nitrogen [2]
The apparatus should be prepared for snap-freezing; this is done by cooling the Thermal Energy Storage Unit (TESU) with a cryocooler to a set cold temperature and circulating a low flow of helium gas, about 4 mg.s−1
Summary
Worldwide cancer is the third most common cause of death, one of eight deaths is cancer related [1]. In order to quantify and benchmark the apparatus to established cooling protocols, experiments are performed to determine the cooling rate of a standard aluminum cryo-vial in liquid nitrogen. The experimental data of cooling of a beef specimen in a cryo-vial is presented followed by the systematic design of the snap-freezing apparatus.
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