Catgut is prepared from collagen extracted from the submucosa layer of sheep and lamb intestines. The intestines are cleaned, split, and the mucosa layer is removed. The collagen strands are spun into a strand and dried. The raw catgut is polished, measured, and sterilized. Sterilization is important as intestines carry bacteria even after cleaning. Common sterilization methods include chemicals like iodine, ethylene oxide gas, or formaldehyde, though chemicals can weaken the catgut. Proper sterilization kills bacteria and spores without compromising the catgut's strength and absorbability.

1. CATGUT
Sterile surgical catgut consists of a strand prepared from collagen
derived from healthy mammals after purification and sterilization.
Source:
Most widely used source for preparation of catgut is submucosa of
small intestine of sheeps and lambs to lesser extent from serosa
layer of cattle.
Factorstobeconsideredinmanufactureofcatgut:
Diameter of intestine should not be more than 18mm.Intestine of
animals should not have scar tissue.Younger the animal, smaller
should be the intestine and less likely to be affected by the
food.A number of manufactures of catgut use only 1st
8mm of
intestine measured from duodenum.Such intestine are called
Ligature casings or Runners.
Procedureofremovalofintestinefromanimals:
Gut is removed by gut pullers
Cleaned to remove fecal matter
Inspected,measured and then preserved either in frozen state or
salted state.

2.  As intestine is most vulnerable to bacterial attack and
decomposition, the steps involved in the removal of gut in
slaughter house with precaution such that bacterial
contamination is at its minimum.
Layers of intestine:
There are 4 layers if gut (i,e:) tunica serosa,tunica
musculosa,tunica submucosa and tunica mucosa.Of all these
layers,tunica submucosa is suitable for preparation of the catgut.
Stepsinvolvedinmanufacturingofcatgutfromtheintestine:
1. Thawing
2. Splitting
3. Cleaning of mucosa
4. Spinning
5. Polishing
6. Guaging
7. Sterilization
8. Standardisation
Thawing:
The first step in manufacturing of catgut is to soak ligature casing
in water to thaw or to remove the salt and prepare them for
splitting.

3. Splitting:
Splitting or cutting is carried out by inserting the curved horn of
cutting tool into the end of casing and pulling the runner over the
cutting blades.Horns are used to identify the rough side of the
intestine.
Rough side and smooth side of intestine are kept apart
throughout the process as they behave in differnt case physically
and chemically.
Cleaningofmucosa:
This step is used to remove mucosa,muscle and any remaining
serosa layers after the splitting step.This step is usually done by
treating with alkaline solutions.
When the ribbons are judged satisfactorily cleaned,they are cut to
a predetermined length, assembled in multiple ribbons of same
time and mounted on to string loops on either side.
Spinning:
The apparatus selected for spinng is based on manufacturer’s
choice
Number of hooks on the machine to which the string loops are
attached varies from 2 to 20.
Spinning is done sometimes from both ends and takes place in
immersed water and alkaline solution.

4. Spinning is highly skilled operation-
 Multiple of ribbons which are over spurn will tend to lack
elasticity and will curl when they dry.
 If they are underspun,elasticity will be too great and tensile
strength will be reduced.
Angle of ply to the horizontal is the guide whether the string has
been properly prepared or not. After spinning, catgut is mounted
on drying frames and conditions on drying time and humidity being
carefully controlled.
The resulting strand of dried catgut is known as ‘RAW CATGUT’
Polishing:
Aim of this step in manufacturing is-
Strands of catgut will vary only slightly in diameter and need a
light manner of polishing.
Polishing of catgut is done by 2 methods:
1. Rotating the springs while a carriage baring an abrasive paper
moves to and fro along the length.
2. By using a pair of grinding wheels and settling the wheels to
the required distance apart.
These methods should be careful that the piles of strand will not
damage with consequent loss in tensile strength.
Guaging:

5. Checking the diameter of catgut is done by the guage of dial
reading time. This machine gives the details of press or foot and
weight loading.
As the diameter of catgut will vary with relative humidity of the
atmosphere, the diameter of catgut is measured at a relative
humidity of 60-80% and at a temperature of 16-21o
c.
Normal guages of catgut used vary from finest size 1 in opthalmic
work to the thickest size 7 which is occasionally used for specialist
surgery.
Sterilization:
Mammalian intestine in the living animal is normally relatively free
of micro organisms but immediately after the death,grown of
micro organism proceeds at a rapid rate.
Even though the conditions of slaughter house are carefully
controlled to avoid bacterial contamination,the intestine inavitably
carry large bacterial population.Freezing or salting of the material
inhibits further growth but doesnot kill these
organisms.Streptococcus faecalis and E.coli are commonly found in
the intestine but are suseptable to sterilization process.Apart
from these organism spores of other organisms such as Clostidium
and Bacillus anthrax contamination will be there
 Spores can revert back if the conditions are favourable.
 Difficulty in sterilization is exacerbated by the structure of
catgut i.e, where the ribbons twisted together will carry

6. contamination throughout the cross section.As a result micro
organisms are located in the center and are insulated.
Keeping these trouble in the aspect of
microbial contamination of catgut,sterilization of catgut is
necessary and should be done by different ways such as
chemical,heat and radiation.
SterilizationofCatgut:
The aim of sterilisation of catgut is to sterilize catgut without
damage in physical characteristics such as tensile strength and
absorbability.
The sterilization should interfere as little as possible with inherent
structural advantages of collagen is a strong,flexible and elastic
fibre that will be absorbing by the body in a surgical acceptable
manner.
ChemicalSterilization:
The chemical used in the sterilization must be sporicidal.Most of
the organic and inorganic compounds are not sporicidal and the
available sporicidal agents are very few.
The sporicidal chemical agents used for sterilization of catgut are:
o Formaldehyde
o H2o2
o Hypochloride
o Gluteraldehyde
o Ethyl iodide

7. o Methyl bromide
o Iodine
o Ethyl oxide and
o Beta-propiolactone.
Immersion of standard catgut length wound on framer and reels in
standard solution of I2,KI,KIO3.
Procedure:
Catgut must absorb 12% of its own weight of iodide.After this,the
catgut is transferred from the solution and excess iodine is
removed by sterile solvent containing a bacteristatic.Sterile
strands are then transferred to their final container to which
sterile fluid (95 % iso propyl alchol) is added when the containers
are sealed.
EthylOxideSterilization:
Ethyl oxide is explosive gas and is usually mixed with carbondioxide
and freon.The factors to be controlled during ethylene oxide
sterilization are:
The process is usually monitered with spore stripes of Bacillus
subtilis var.nigar.Care must be taken to limit residual ethyl oxide
in the catgut.
Aseptic procedure must be followed for filling and sealing step to
the final container.
FormaldehydeSterilization:

8. Although formaldehyde can destroy anthrax spores,it has several
disadvantages such as –
1. Catgut will be more hardened and so its absorbtion is
delayed.
2. Tensile strength of catgut is reduced.
3. The sterility achieved is not complete.
H202 Sterilization:
H202 can effectively sterilize catgut but result in poor
quality.Sometimes it has been used to improve the colour of the
catgut by treating collagen in ribbon form before spilling.
SolutionofSodiumandPottasiumhypochloride:
These solutions are sporicidal in acid solutions.
DisadvantagesofHypochlorides:
Catgut sterilized by hypochloride solution is not suitable because:
o Penetrating power is very poor.
o Catgut is underly swollen.
o Catgut of poor tensile strength.
Gluteraldehyde:
This solution is active in Na2Hco3 buffered solutions.It can retain
its sporicidal activity for about 2 weeks only.
Iodide:

9. It is only suitable chemical for large scale sterilization of catgut.