3. 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.
4. 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”.
5. 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.
6. 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, and
c. Type 3:ghosts which remain leaky under different
experimental conditions.
8. 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.
9. ELECTRO-INSERTION OR
ELECTROCAPSULATION:
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.
10. 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
11. % 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.
12. 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
14. 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