8/14/2019 Blood Compatibility of Implants

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Presented by:

Navjot Kanwar

M.PHARM- 1

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  Implants are sterile system contains a huge

amount of drug which can provide the

required blood concentration ranging from a

day, a week, few months or even for fewyears.

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All materials used for implants being physically

and chemically stable, but vitally important that

the materials are biocompatible.

Desirable criteria for implantable drug delivery

biomaterials include:

The biomaterial must be chemically inert in that

it does not cause any biological effect or

interact with other adjuvant in formulation.

Biomaterial must not cause any inflammatory or

foreign body reaction in the body.

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Biomaterial must not be carcinogenic.

Biomaterial should not cause any allergic or

hypersensitivity reactions.

It should be mechanically stable.Does not cause any thrombogenecity.

The biomaterial must have ability to be

easily removed after its therapeutic

duration.

Must be compatible with a wide range of

drugs.

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These responses are due to its:

Physical properties resulting in epithelial

encapsulation,thickening of connective tissue,

presence of giant cells.Chemical reaction between biomaterial and tissue

resulting in inhibition of of epithelial growth, induction

of epithelial hypertrophy, connective tissue

inflammation, vacuolization of tissue.Presence of additives during polymer production.

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Implant size

Implant shape

Implant material

Surface wettability

Surface charge

Surface roughness

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  Little is known about problems that arise

when blood or other tissue fluids make

contact with foreign surfaces.

Electric phenomenon occurring at interfacecould lead to thrombosis formation.

Materials with high negative zeta potential

resist this tendency.

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  Possible effects of biomaterials on living

environment due to lack of blood

compatibility are – thrombogenecity and

induction of haemolysis.

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  Prevention of thrmbosis:

To prevent this thrombosis , surface of

vascular implants should be smooth and in

contact only with an area of high velocity.

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Variuos methods:

Kinetic clotting test

Ex-vivo measurement of amount of

thrombus and estimation of its platelet andfibrin content by radiotracer techniques

Critical surface tension test

Haemolysis and shear stress test

Caval ring implant test

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Venous blood from dog is taken

Blood enters a specificallydesigned chamber that containstest biomaterial, through a shortsegment of silicone rubber tubing

Amount of free haemoglobin aremeasured spectrophotometricalyyat 254 nm at periodic intervals

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  It only measures the end product (blood clot) and not

the factors determining blood compatibility. Therefore

there is no guarantee that the biomaterial is fully

compatible if there is no clot formation.

There could also be problems with the venous blood

coming into contact with silicone tubing before test

biomaterial as silicone itself also activate coagulation

factors.

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This is done by radio tracer technique.

Carotid arterial blood to jugular vein of dog

is connected ex-vivo to two test chambers

containing stainless steel shafts. Theconnection shunt is a 20 cm long silicone

rubber tube.

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  Silicone rubber shunt could create

interpretation problems on the suitability of

the biomaterial.

Centrifugal force of the rotating stainlesssteel shafts and the difficulty of coating the

shaft with test biomaterial causes test and

result interpretation problems.

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