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Technology | Common slicing techniques
2023-07-13
Abstract
It is well known that many tools and materials including tissue or cell specimens to be studied are required in medical research, especially in the hot research of cancer. Specimens can be used to examine the shape and structure of cells (morphology), disease status, intra-and inter-cellular communication, and, therefore, how they were obtained from biopsies. Since most biological materials are both fragile and perishable, care must be taken to ensure that they are prepared and preserved correctly.
In this paper, we will focus on the relationship between FFPE and frozen tissue. There are two main methods of tissue preparation today. For decades, tissues have been saturated with formalin (aka formaldehyde) and then embedded in paraffin blocks (called formalin-fixed paraffin-embedded or FFPE tissue). With the advent of reliable ultra-low temperature freezers and a large supply of liquid nitrogen, freezing tissue as a second means of long-term storage has become feasible. Both methods have their own advantages and disadvantages. The following is a comparison of the advantages and disadvantages of the two preservation methods.
FFPE
Formalin-fixed paraffin-embedded tissue
Formalin-fixed paraffin-embedded tissue is the most common method of storing specimens, and hospital pathologists have been using FFPE tissue for decades. When a biopsy sample is taken from a patient, some of this material is processed for research use-sometimes with reference to previous pathophysiological tissue during the patient's treatment.
Other researchers save tissue donated by humans or collected from animals for research purposes.
These archives are called "biobases" and can be developed by universities and hospitals, or created for commercial purposes by companies that serve the research community. The establishment of archives can provide strong support for follow-up research.
Because libraries cover long timelines, they can provide historical information and can output large amounts of data. Because FFPE slices can be stored at room temperature, it is very inexpensive to create a large sample that is stable for a long time.
Formalin and wax preserve the fragile structure inside and between cells in the tissue, which allows scientists who pay attention to cell and tissue morphology to use FFPE tissue for scientific research. For example, pathologists can use FFEP sections of biopsy tissue as a basis for cancer diagnosis.
The FFPE treatment allows the proteins in the tissue to be preserved at the same time, not just the structures visible under the microscope. Histologists can use fluorescently labeled antibodies (or antibodies labeled by other means) to specifically bind to certain proteins to verify whether they are present in certain cells within a tissue, and whether the location and amount of these proteins in diseased tissue is different from healthy tissue. This method is called immunohistochemistry (IHC). Because FFPE is a long-established and well-established method of tissue storage, pathologists are accustomed to examining tissue biopsies and using the biopsy results for diagnosis.
Disadvantages of the FFPE organization
Formalin is volatile, toxic, and smelly. Most paraffin embedding and fixation procedures are also laborious and time-consuming. In addition, while the protein is retained, the protein is denatured so that it is no longer biologically active. Therefore, the deformed standard in the section may not bind to some antibodies (such as natural antibodies to the protein). This can limit the value of the slices in, for example, IHC studies, so the slices cannot be used for biochemical analysis.
Another problem is that the nucleic acids (DNA and RNA) in FFPE tissue cannot be maintained in a biologically active state. Although it is possible to isolate nucleic acids from stored paraffin section tissue, the use of such nucleic acids is limited due to lack of information.
Thus, FFPE tissue may not be amenable to all molecular genetic analyses. Moreover, most FFPE processes have not been standardized, and there is no guarantee that the processing of experimental samples is consistent. Non-standardized preparation methods can seriously affect the results obtained from them-especially in experiments for molecular genetic analysis. Some molecular analysis is possible, but much is lost when the FFPE method is used to preserve the tissue.
frozen section tissue
Freezing method-a new means of sample processing