Before tissues can be utilized for important biomedical and drug discovery research, they must first be properly prepared. Tissue processing protocols are intended to remove water from the tissues, exchanging the water with supporting mediums that increase tissue rigidity and ease of preparation by sectioning. Better tissue sections reduce damage to sensitive structures within the tissue, and so improve their use for in-vitro research.
One of the most common methods for preserving valuable tissue specimens involves fixing a specimen in neutral-buffered formalin soon after resection and then embedding it in paraffin. These tissues samples, known as formalin-fixed and paraffin-embedded (FFPE) are among the most commonly used tissues for biomedical research. FFPE tissues are often selected for large-scale, long-term studies of human cancers and inflammatory diseases.
Tissue processing protocols follow a series of well-established steps. When tissue is immersed in a fluid reagent, interchange occurs between the tissue fluids and the fluid medium. Three key factors impact the rate of interchange between the fluids and reduce the duration of tissue processing.
By maximizing the tissue surface area to infiltrating reagents, the rate of fluid exchange increases. Agitation using manual or automated processors increases the flow of fresh fluids in and around the tissues. Most tissue processing protocols utilize automated processors with vertical or rotary oscillation mechanisms to speed fluid exchange.
Without agitation, tissues tend to settle to the bottom of the processing device or become too tightly packed, therefore reducing surface area available for fluid exchange. When tissue processing begins, tissues should be loosely packed in the processing container so they are suspended, after which agitation can begin and will enhance exchange of tissue fluids. According to histology experts, efficient agitation can reduce overall processing time by 30 percent.
Elevated tissue processing temperatures can increase the rate of fluid penetration and exchange. However, heat must be carefully applied. Heat increases molecular kinetic energy and diffusion rates, which decreases solution viscosity. Too much heat causes tissue shrinkage, hardening and brittleness, and negatively affects their research utility. Conversely, at low temperatures, tissue structures are stabilized against solvent effects; however, such low temperatures also increase the viscosity of reagents used in tissue processing protocols, reducing the rate of diffusion and increasing processing time.
Applying moderate temperatures, in the range of 37° to 45°C, for a limited time can speed up tissue processing protocols; careful attention must be paid to this step to limit tissue shrinkage and viability.
3.Vacuum and pressure
Reduced pressure can increase the infiltration rate and decrease time needed to complete steps in tissue processing protocols. Studies show that vacuum will extract reagents from tissue only if these fluids are more volatile than the reagent being replaced. Vacuum application during tissue infiltration improves processing quality. It can aid in removal of trapped air from for example, lung tissue, or other porous tissue. Using vacuum during tissue processing protocols can reduce the infiltration time when dealing with dense and fatty tissue specimens.
Top-quality, carefully-sourced, properly-prepared tissue specimens will accelerate your biomedical and drug discovery research programs. What biospecimens can we find for you?