Erythrocytes have potential as drug carriers due to their biocompatibility. They can encapsulate drugs using various entrapment methods and target the reticuloendothelial system. Loaded erythrocytes are characterized for drug content, release kinetics, morphology and cellular recovery. Applications include treatment of lysosomal storage diseases, hepatic tumors, and parasitic diseases by delivering drugs to target sites. Erythrocytes thus provide a means for sustained drug delivery.

1. A Seminar on
RESEALED ERYTHROCYTES
BY
T.SHIVA
B.PHARMACY
KOTTAM INSTITUTE OF
PHARMACY

2. Introduction
Among the various carriers used for targeting of
drugs to various body tissues, the cellular carriers
meet several criteria desirable in clinical
applications, among the most important being
biocompatibility of carrier and its degradation
products.
Leukocytes, platelets and erythrocytes have been
proposed as cellular carrier systems. Among these,
the erythrocytes have been the most investigated and
have found to possess great potential in drug
delivery.

3. Advantages:
They are the natural product of the body which are
biodegradable in nature.
Isolation of erythrocyte is easy and larger amount of
drug can be encapsulated in a small volume of cells.
The entrapment of drugs does not require any
chemical modification of the substance to be
entrapped.
They are non-immunogenic in action
They prolong the systemic activity of drug while
residing for a longer time in the body

4.  They protect the premature degradation, inactivation and
excretion of proteins and enzymes
 They can target the drugs within reticuloendothelial system
 They facilitate incorporation of proteins and nucleic acids in
eukaryotic cells by cell infusion with RBC.
 A longer life span in circulation as compared to other
synthetic
 carrier
Disadvantages:
 They have a limited potential as carrier to non-phagocytic
target tissue.
 Possibility of clumping of cells and dose dumping may be
there.

5. Entrapment methods
1) Hypo-osmotic methods.
a. Dilution method.
b. Dialysis.
c. Presswell method.
d. Isotonic osmotic lysis method.
2) Electrical break down.
3) Endocytosis.
4) Membrane perturbation method.
5) Normal transport.
6) Lipid fusion method.

6. a. Dilution method
Population of erythrocytes when exposed to hypotonic
saline solution (0.4% NaCl) swells until it reaches a
critical value of volume or pressure where membrane
ruptures and becomes permeable to macromolecules
and ions, therefore permitting the escape of cellular
components.
One volume of washed erythrocytes could be treated
with 2-20 volumes of materials to be loaded in a
hypotonic buffer at 0oC or 5 min.
Further incubation at 25oC in an isotonic solution
(0.9% NaCl) reseal them again. This method is rapid
and simple for low molecular weight drugs.
The entrapment efficiency is 1-8%.

7. Dialysis method

8. Preswell dilutional technique

9. d. Isotonic osmotic lysis:
In order to avoid disadvantages of hypotonic hemolysis,
efforts were made to develop resealed V under isotonic
conditions. Hemolysis in isotonic conditions can be
achieved both by physical and chemical means.
2. Electrical break down method:
Use of electrolysis to generate desirable membrane
permeability for drug loading into RBC is the basis of this
method. In this, electrically induced permeability
changes at high membrane potential differences.

10. Electrical breakdown method

11. Endocytosis

12. 4. Membrane perturbation
Antibiotics such as amphotericin B damage micro-
organisms by increasing the permeability of their
membrane to metabolites and ions. This property
could be exploited for loading of drug into
erythrocytes. Amphotericin-B was used to load
erythrocytes with antileukaemic drug daunomycin.
Amphoyericin-B interacts with the cholesterol of the
plasma membrane of eukaryotic cells causing change
impermeability of the membrane.

13. Membrane perturbation

14. 5. Normal transport mechanism
It is possible to load erythrocytes with drug without
disrupting the erythrocyte membrane in any way by
incubating the drug and erythrocytes for varying period
of time. After infusion the drug would, exit from the cell
following kinetics compared to those observed for entry.
6. Lipid fusion method
Lipid vesicles containing drug can be directly fused with
human erythrocytes leading to exchange of lipid
entrapped drug. This technique was used for loading
inositol hexaphosphate into resealed erythrocytes. This
method gives very low encapsulation efficiency (1%).

15. Characterization of resealed erythrocytes:
1. Drug contain determination
 To determine drug contain, packed loaded cell are de-
protenized with acetonitrile after centrifugation at 3000 rpm
for a fix time interval.
 The clear supernatant is assayed for drug contain.
2. In vitro Drug and Hemoglobin release
 Normal and loaded erythrocytes are incubated at 37 0 C in
phosphate buffer saline at 50% haematocrit in a metabolic
rotating wheel incubator bath.
 The samples are withdrawn with the help of a hypodermic
syringe fitted with a 0.8 µ spectrophore membrane filter. The
samples are then deprotenized with the acetonitrile and can
be estimated amount of drug release.

16. 5. Turbulence shock:
The parameter indicates the effects of shear force
and pressure by which resealed erythrocytes
formulations are injected, on the integrity of the
loaded cells.
 Loaded erythrocytes are passed through a 23 gauge
hypodermic needle at flow rate of 10 ml/min. After
every pass, aliquot of suspension is withdrawn and
centrifuged for 15 min and hemoglobin content
leached out are estimated spectrophotometrically.

17. 6. Morphology and percent cellular
Recovery:
Phase-contrast optical microscopy, transmission
electron microscopy and scanning electron
microscopy are the microscopic methods used to
evaluate the shape, size and the surface features of
the loaded erythrocytes.
 Percent cell recovery can be determined by
assessing the number of intact erythrocytes
remaining per cubic mm with the help of a
haemocytometer.

18. Applications:
1. Treatment of lysosomal storage disease:
Resealed erythrocytes have been proposed to deliver
lysosomal enzymes to lysosomes of the erythrophagocytic
cells, thus resulting in replacement of the missing
enzyme. Ex: β-glucoronidase, β-galactoronidase and β-
glucosiade.
2. Treatment of Gaucher’s disease:
Gaucher’s disease is due to accumulation of
glucocerebroside from catabolised erythrocytes and
leukocytes in spleen, liver and bone marrow. This disease
was treated by encapsulating glucocerebroside in
erythrocyte.

19. 3. Treatment of liver tumors:
Anticancer agents like bleomycin, adriamycin, L-
asparaginase, doxorobucin and methotrexate are
encapsulated in erythrocyte to treat hepatic
carcinomas.
4. Erythrocytes as circulating carriers:
Various bioactive agents are encapsulated in
erythrocytes for their slow release in circulation for
treatment of parasitic diseases in cattle. Ex:
homidium bromide is encapsulated in erythrocytes
to treat trypanosomiasis.

20. 5. In enzyme delivery:
To eliminate or minimize the problems related to
immunologic responses and toxicity, encapsulated
enzyme administration is suggested
6. Prevention of thromboembolism:
Encapsulated heparin is liberated from circulating
erythrocytes at the site of thrombus formation thus
reducing the risk of further thrombus growth.

21. 7.Slow drug release.
Erythrocytes have been used as circulating depots for
the sustained delivery of antineoplastics,
antiparasitics, veterinary antiamoebics , vitamins ,
steroids , antibiotics , and cardiovascular drugs .
8.Treatment of hepatic tumors.
Hepatic tumors are one of the most prevalent types
of cancer. Antineoplastic drugs such as methotrexate
, bleomycin , asparginase , and adriamycin have
been successfully delivered by erythrocytes.

22. 9. Treatment of parasitic diseases.
The ability of resealed erythrocytes to selectively
accumulate within RES organs make them usefultool
during the delivery of antiparasitic agents. Parasitic
diseases that involve harboring parasites in the RES
organs can be successfully controlled by this method.
Results were favorable in studies involving animal
models for erythrocytes loaded with antimalarial
(17), antileishmanial (17, 23, 51), and antiamoebic
drugs (13, 38).

23. 10. Removal of RES iron overload.
Desferrioxamine-loaded erythrocytes have been used
to treat excess iron accumulated because of multiple
transfusions to thalassemic patients (13, 51).
Targeting this drug to the RES is very beneficial
because the aged erythrocytes are destroyed in RES
organs, which results in an accumulation of iron in
these organs.

24. CONCLUSION
I concluded “among the various carriers used for
targeting of drugs to various body tissues, the
erythrocytes have been the most investigated and
have found to possess great potential in drug
delivery”.

25. REFERENCES
Gilbert s Banker. Modern Pharmaceutics. 4 th edition.
S.P. Vyas and R.K. Khar. Targeted and Controlled drug
delivery. 1 st edition.
N.K. Jain. Controlled and Novel drug delivery. 1 st edition.
Y.W. Chien. Novel Drug Delivery Systems.
Binghe Wany, Teruna Siahaan, Richard A Soltao. Drug
Delivery Principles and Applications.
Patel RP, Patel MJ and Patel NA. an overview of resealed
erythrocyte drug delivery. J Pharm Res. 2009; 2(6):
1008-1012.
Gothoskar AV. Resealed erythrocytes :an overview.
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