CELLULAR CARRIERS

PRESENTED BY: STUTI TRIPATHI M.PHARM 2nd SEM.

ERYTHROCYTES

RESEALED ERYTHROCYTES:

Resealed erythrocytes are prepared by collecting blood samples from the organism of interest and separating erythrocytes from plasma.

Resealed erythrocytes are biocompatible, biodegradable, having long circulation half-life and can be loaded with variety of active substances.

PREPARATION OF RESEALED ERYTHROCYTES:

By using various methods (discuss later),cells are broken.

Drug is entrapped into erythrocytes, and then they are resealed.

Resultant carriers are termed as “Resealed erythrocytes”.

PROPERTIES OF RESEALED ERYTHROCYTES:

The drug should be released at target site in a controlled manner.

It should be appropriate size, shape and should permit the passage through capillaries and minimum leakage of drug should take place.

It should be biocompatible and have minimum toxic effect.

The carrier system should have an appreciable stability during storage.

It should have the ability to carry a broad spectrum of drug.

The degradation product of the carrier system, after release of the drug at selected site should be biocomaptible.

ENTRAPMENT METHOD:

HYPO-OSMOTIC LYSIS METHOD: Hypotonic lysis of cells in a solution containing

the drug to be entrapped followed by restoration of tonicity and reseal them.

The ghost population so obtained are heterogeneous.

Three types of ghosts can be distinguished :a. Type 1:ghosts which reseal immediately after

haemolysis,b. Type 2:ghosts which reseal after reversal of

haemolysis by addition of alkali ions, andc. Type 3:ghosts which remain leaky under different

experimental conditions.

VARIOUS CONDITION AND CENTRIFUGAL FORCE USED FOR ISOLATION OF ERYTHROCYTES:

Sr. No.

Species Washing buffer Centrifugal force(g)

1. Rabbit 10mmol Phosphate buffer 500-1000

2. Dog 15mmol Phosphate buffer 500-1000

3. Human 154mmol NaCl <500

4. Cow 10-15mmol Phosphate buffer 1000

5. Mouse 10mmol Phosphate buffer 100-500

6. Horse 2mmol Magnesium chloride,10mmol glucose

1000

7. Sheep 10mmol Phosphate buffer 500-1000

8. Pig 10mmol Phosphate buffer 500-1000

CHEMICAL PERTURBATION OF THE MEMBRANE:

This method is based on the increase in membrane permeability of erythrocytes when the cells are exposed to certain chemicals.

This method was used successfully by Kitao and Hattori to entrap the antineoplastic drug “daunomycin” in human and mouse erythrocytes.

ELECTRO-INSERTION ORELECTROCAPSULATION:

This method is also known as electroporation, based on the observation that electrical shock brings about irreversible changes in an erythrocyte membrane.

The erythrocyte membrane is opened by a dielectric breakdown. Subsequently, the pores can be resealed by incubation at 37⁰c in an isotonic medium.

CHARACTERIZATION OF RESEALED ERYTHROCYTES: DRUG-CONTENT DETERMINATION: Packed loaded cells

are deprotenized with acetonitrile after centrifugation at 300 rpm for a fixed time interval. The clear supernatant liquid is assayed for drug content.

IN-VITRO DRUG RELEASE AND Hb CONTENT: The cell suspensions are stored at 4⁰c in ambered colored glass container. Periodically clear supernatant are drawn using a hypodermic syringe, filter and deproteined with methanol and then estimated for drug content.

%Hb release= A540 of sample – A540 of background

% CELL RECOVERY: May be determined by counting the no. of intact cells per cubic mm of packed erythrocytes before and after loading the drug.

ERYTHROCYTE SEDIMENTATION RATE: It is an estimate of the suspension stability of RBC in plasma and is related to the no. and size of the red cells and to relative concentration of plasma protein, especially fibrinogen and alpha and beta globulins. This test is performed by determining the rate of sedimentation of blood cells in a standard tube.

NORMAL BLOOD ESR=0-15 mm/hr.

APPLICATIONS:

Targeting of bioactive agents to RE system

Targeting to sites other than RES-rich organs

Erythrocytes as circulating bioreactors

Erythrocytes as carriers for enzymes

VARIOUS APPLICATION OF RESEALED ERYTHROCYTE:

APPLICATION DRUG/ENZYME/MACROMOLECULE

Enzyme deficiency replacement therapy

ẞ- galactosidase , ẞ-fructofuronodase,urease,glucose-6-phosphatedehydrogenase

Thrombolytic activity Brinase , aspirin , heparin

Iron overload Desferroxamine

Immunotherapy Human recombinant interlukin-2

REFERNCES

Jain S.K. and Vyas S.P., “Magnetically Responsive Diclofenac Sodium- Loaded Erythrocytes: Preparation and In-Vitro Characterization, CBS Publishers and Distributors, pg. no.-141-51.

Vyas S.P. and Dixit V.K., Pharmaceutical Biotechnology , CBS Publishers & Distributors, New Delhi, pg. no. 655

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