resealed erythrocytes

Resealed Erythrocyte

As Drug Carrier

Presented By Bindiya Patel

M.PHARM (PHARMACEUTICS)

CONTENT

Introduction

Why erythrocyte as carrier

Source and isolation of erythrocytes

Advantages

Limitation

Drug carrying potential of RBC

Effects of tonicity on RBC

Method of loading

Reference

INTRODUCTION

Erythrocytes have been the most extensively investigated and

found to posses great potential in novel drug delivery .

Erythrocytes are loaded with drug/enzymes & provide target

drug delivery system.

Such drug-loaded carrier erythrocytes are prepared simply by

collecting blood samples from the organism of interest,

separating erythrocytes from plasma, entrapping drug in the

erythrocytes, and resealing the resultant cellular carriers. Hence,

these carriers are called resealed erythrocytes.

CONT...

• Erythro= red

• Cytes = cell

• Biconcave discs, anucleate.

• Filled with hemoglobin (Hb), a protein that functions in gas transport.

• Erythrocyte ghosts: RBC without hemoglobin

Why Erythrocyte As Carrier ???

Erythrocytes are potential biocompatible vectors for different

bioactive substances, biological carriers of drugs, and enzymes.

Erythrocytes loaded with drugs and other substances allow for

different release rates to be obtained.

Encapsulation in erythrocytes significantly changes the

pharmacokinetic properties of drugs in both animals and

humans, enhancing liver and spleen uptake and targeting the

reticulo-endothelial system (RES).

Encapsulation of new prodrugs with increased duration of action,

etc

Cont...

Erythrocytes are biocompatible, biodegradable, possess long

circulation half lives, and can be loaded with a variety of

biologically active compounds using various chemical and

physical methods.

Erythrocytes, the most abundant cells in the human body,

have potential carrier capabilities for the delivery of drugs.

They capability for prevention of premature degradation or

inactivation.

Source And Isolation Of Erythrocytes

Source:- mice, cattle, pig, dog, sheep, goat, monkey,

chicken, rat, rabbit & human.

Whole blood can be collected by venipuncture or from

orbital sinus in heparinized tube.

EDTA or heparin can be used as anticoagulants agents.

Fresh blood is used for loading of drugs.

Biodegradable Isolation is easy Non immunogenic large volume of drug can be encapsulated in small volume

of erythrocytes Prolong systemic activity of drug Reduce Adverse Effect Peptide & Enzyme Delivery

Advantages

Limitation

They have a limited potential as carrier to non-phagocytic target

tissue.

Possibility of Leakage of the cells and dose dumping may be

there.

Several molecules may alter the physiology of the erythrocyte.

Liable to biological contamination due to the origin of the blood,

the equipment and the environment.

Drug Carrying Potential Of RBC

The carrier potentials of these cells was first realized in

early 1970.

The developing RBC has capacity to synthesize hemoglobin,

however, adult RBCs do not have this capacity and serve as

carriers for hemoglobin.

Drug which are normally unable to penetrate the

membrane, should be made to transverse the membrane

without causing any irreversible changes in the membrane

structure and permeability.

Cont...

Cells must be able to release the entrapped drug in a

controlled manner upon reaching the desired target.

The processing of drug entrapment requires a reversible

and transient permeability change in the membrane, which

can be achieved by various physical and chemical means.

Effects Of Tonicity On RBC

Method Of Loading

Drug loading in Resealed erythrocytes

Electro encapsul

ation

Membrane perturbati

on

Hypo-osmotic

lysis

Dialysis method

Osmotic-lysis

Preswell method

Dilution method

Lipid fusion endocytosi

s

Dilution Haemolysis

RBC0.4% NaCl

HypotonicMembrane ruptured

RBC

Drug

Loading buffer

Loaded RBC

Resealed Loaded RBC

Resealing buffer

Incubation at 250C

Hypotonic medium

Isotonic medium Washed

Efficiency 1-8%

Isotonic Osmotic Lysis

RBC Isotonically ruptured RBC

Chemical – urea, polyethylene, polypropylene, and NH4Cl

Physical rupturing

Chemicalrupturing

DrugIsotonicBuffer

Loaded RBC

Resealed RBC

Incubation at 250 C

Preswell Dilutional Haemolysis

RBC

0.6%w/v NaCl

Swelled RBC Drug +

Loading buffer

5 min incubation at 0 0c Loade

d RBC

Incubation at 25 0c

Resealing Buffer

Resealed RBC

Efficiency 72% Fig:- Preswell Method

Dialysis

RBC

Phosphate buffer

+

80 % Haematocri

t value

Placed in dialysis bag

with air bubble

Dialysis bag placed in 200ml of lysis buffer with mechanical rotator 2hrs

4 0C

DrugLoading

buffer

Loaded RBC

Dialysis bag placed in Resealing buffer with

mechanical rotator 30 min 37c.

Resealed RBC

Efficiency 30-45%

Electroinsertion Or Electro-encapsulation

RBC

2.2 Kv Current for 20 microsecAt 250 CPulsatio

n medium

+ +Drug

Loading suspension

3.7 Kv Current for 20 micro

sec

Isotonic NaCl

Loaded RBC

Resealing Buffer

Resealed RBC

Fig:- Electro-encapsulation Method

Entrapment By Endocytosis

RBC

Drug Suspensi

on

+

Buffer containing ATP, MgCl2, and

CaCl2At 250 C

Loaded RBC

Resealing Buffer

Resealed RBC

Fig : Entrapment By Endocytosis Method

Membrane Perturbation Method

RBC

Amphotericin B

e.g. Chemical agents

Increased permeability

of RBC Resealing Buffer

Drug Resealed

RBC

Comparison Of Various Hypo-osmotic Lysis Method 

 METHOD

%LOADINGADVANTAGE

SDISADVANTAGE

S

Dilution method 1-8%

Fastest & simplest

especially for low molecular weight drugs

Entrapment efficiency is very

less (1-8%)

Dialysis 30-45%

Better in vitro survival of

membrane due to lesser ionic

load

Time consuming; heterogeneous size

distribution of resealed

erythrocytes

Preswell dilution 20-70%

Good retention of cytoplasm

constituents & good survival in

vivo.

-

Isotonic osmotic

lysis-

Better in vivo surveillance

Impermeable to large molecules , process is time

consuming

REFERENCES

Jain.S., Jain.N.K., resealed erythrocytes as drug carriers, Edited

Jain N.K., Controlled And Novel Drug Delivery, New Delhi, CBS

publishers, New Delhi, 2004, 256-281.

Vyas S.P., Khar R.K., Targeted And Controlled Drug Delivery:

Novel Carrier Systems, New Delhi, CBS publisher, 2004, 387-413.

Indian Journal of Pharmaceutical Education & Research Vol.

43(4), Oct-Dec, 2009 , 375-386 Journal of Controlled Release

(2004) 27– 49