Resealed Erythrocytes

Contents

Introduction

Source of erythrocytes

Isolation of erythrocytes

drug loading in erythrocytes

Factors effecting resealed erythrocytes

Advantages of erythrocytes

Method of drug loading

In vitro characterization of erythrocytes

applications

Introduction

- Present pharmaceutical scenario is aimed at development of drug delivery systems which maximize the drug targeting along with high therapeutic benefits for safe and effective management of diseases.

- Target drug delivery system indeed a very attractive goal because in this system targeting of an active bio molecule from effective drug delivery where pharmacological agents directed specifically to its target.

- Various cellular carriers has been used for drug targeting among which cellular carriers(leukocytes, platelets and erythrocytes) offer a great

Erythrocytes

• Erythrocytes also known as red blood cells and have extensively studied for their potential carrier capabilities for delivery of drugs .

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Electrolyte composition of erythrocytes:

- Although qualitatively similar to that of plasma .however, quantitatively it differs from that of plasma.

- The concentration of K+ is more in erythrocytes and Na+ in plasma.

- The osmotic pressure of the interior of the erythrocytes is equal to that of the plasma and termed as isotonic (0.9% NaCl or normal physiological saline.)

- Changes in the osmotic pressure of the medium surrounding the red blood cells changes the morphology of the cells.

- If the medium is Hypotonic, water diffuses into the cells and they get swelled and eventually loose all their hemoglobin content and may burst.

- if the medium is Hypertonic,(i.e. higher osmotic
pressure than 0.9% NaCl) they will shrink and become irregular in shape.¹

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Haematocrit value

- If blood is placed into a tube and centrifuged, the cells and the plasma will separate.

- The erythrocytes, which are heavy, will settle down to the bottom of the tube, while the plasma rises up to the top and the leukocytes and platelets will form a thin layer (buffy coat) between the erythrocytes and the plasma.

- The haematocrit is defined as the percentage of whole blood made up of erythrocytes.

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Source of erythrocytes

- Different mammalian erythrocytes have been used for drug loading, resealing and subsequent use in drug and enzyme delivery.

E.g. mice, cattle, pigs, dogs, sheep, goats, monkeys, chicken, rats, and rabbits etc.

- EDTA or heparin can be used as anticoagulants agents

Isolation of erythrocytes

- Blood is collected into heparinized tubes by venipuncture

- Blood is withdrawn from cardiac/splenic puncture(in small animal) and through veins (in large animals) in a syringe containing a drop of anti coagulant.

- The whole blood is centrifuged at 2500 rpm for 5 min at 4 ±1.0o C in a refrigerated centrifuge.

- The serum coats are carefully removed and packed cells

washed three times with phosphate buffer saline (pH=7.4).

- The washed erythrocytes are diluted with PBS and stored at 40oC until used.

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Drug loading in erythrocytes

- When erythrocytes are suspended in a hypotonic medium they swell to about one and a half times their normal size, and the membrane rupture in the formation of pores with diameters of 200 to 500 Ao

- The pores allow equilibration of the intracellular and extracellular solution. If the ionic strength of the medium then is adjusted to isotonic and the cells are incubated at 37oC, the pores will close and cause the erythrocyte to “Resealed”.

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¹ Balanced ion solutions like Ringer’s and Tyrode’s soln. which are not only isotonic but also contains ions in proper quantity are used in erythrocyte related experiments.