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Means to prepare uniform dilution of a known
quantity of tissue suspended within a known
quantity of a suitable diluents and uniformly
macerate or crush the tissue in such a manner
as to disperse minute fragments of tissue
evenly throughout the mixture.
Tissue homogenization is a process used to
prepare tissue samples for certain types of studies.
It involves encouraging the cells to lyse, or break
apart to release their contents.
Devices designed for tissue homogenization are
used in many lab facilities and specialized
techniques may be used for certain types of cells,
as for example when cells are difficult to break up
because of their structure
Homogenization is one of the steps allowing for
preparation of any biological material as a sample
for the proteomic analysis.
The term “homogenization” covers many
meanings such as mixing, stirring, dispersing,
emulsifying, but in general, it means: receiving
sample of the same composition and structure in
the whole volume.
 By applying homogenization in the procedure of
sample preparation, we assume that the sample
should change its physical properties without any
changes in the chemistry of components.
There are certain variables to be
considered while designing a
homogenizer/cell disruptor.
They are:
- type of homogenizing valve/orifice
- operating pressure
- stages of disruption
- viscosity of the sample
- temperature
Homogenization methods used for the
proteomics purposes can be divided
into five major categories:
1. Mechanical;
2. Ultrasonic;
3. Freeze–thaw;
4. Osmotic and detergent lysis
1-Mechanical homogenization.
Rotor–stator homogenizers are one of the best homogenizing
tools applied in the laboratories.
They can homogenize samples in the volumes from 0.01 ml
to about 20 l, depending on the tip and power of a motor
applied. Homogenizing tips can easily be cleaned and
sterilized
Heat transfer to the processed mixture is low to moderate but
usually needs external cooling.
 Sample loss is minimal in comparison to pressure processors
(French presses), and very small amounts of samples can
easily be homogenized.
During operation, the suspended material is
drawn into the core of the homogenizer by a
rotor turning at 30,000 rpm.
The material is repeatedly cycled through six
narrow slits in the stator where it is rapidly
sheared and disintegrated by high frequency
mechanical action.
Complete homogenization of tissues (muscle,
liver, breast tissue, etc.) is usually achieved in
ten to thirty seconds.
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Ultrasonic homogenizers, also called as disintegrators or
sonificators, are based on the electric effect while
generating the high energy or ultrasonic wave, interacting
with the sample. Energy, resolved after
explosion/implosion of gas microbubbles, effectively
destroys solid particles such as cells.
Ultrasonic devices are mainly used to homogenize small
pieces of soft tissues (brain, blood, liver).
Tough and dense tissues are not recommended to
homogenize using this equipment.
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This type of homogenization uses effect of
ice crystals formation in the tissue during
freezing process.
The method is relatively fast, effective
and, what is also important, does not
introduce any external impurities into the
sample because freezed solution is isolated
from the external environment.
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These methods of disruption of cells utilize osmotic
pressure or detergent interactions to destroy cells’
walls and membranes. They are also efficient for
homogenization of nuclear and mitochondrial
membranes in cell extracts.
Osmotic lysis is often used to disrupt blood cells. It
may be useful for RNA extraction, even from
bacteria like Brucella abortus internalized in
macrophages
Depending on the conditions, osmotic lysis can be
used also for microbial cell disruption.
This image shows how the detergent molecules interefere with the
lipids and proteins on the cell membrane and nuclear membrane,
causing the DNA
to be more exposed.