STANDARD OPERATING PROCEDURE
CLODRONATE LIPOSOMES
PI
Issue Date
Prepared by
Christopher A. Pennell
08/27/2021
Christopher A. Pennell
Lab Location
Revision Date
Approved by
490 MCRB
NA
NA
Background
Macrophages regulate functions of many non-phagocytic cells, mainly through mediation of
soluble molecules as cytokines and chemokines. Macrophages are also involved in
‘homoeostasis’ of the body by ingesting and digesting microorganisms or non-self particles and
macromolecules. Digestion is in turn mediated by their lysosomal enzymes.
Liposomes are artificially prepared lipid vesicles, consisting of concentric phospholipid bilayers
entrapping aqueous compartments. They can be used to encapsulate strongly hydrophilic
molecules solved in aqueous solutions, such as clodronate, a non-toxic bisphosphonate
developed for human application.
After injection, clodronate liposomes function as Trojan horses. Macrophages ingest the
clodronate liposomes and digest the liposomal membranes. Clodronate is not digested and will
remain inside the macrophage. More clodronate will accumulate in the macrophage as it ingests
and digests more clodronate liposomes. At a certain intracellular concentration, clodronate will
eliminate the macrophage by initiating its programmed cell death, i.e. apoptosis.
The phospholipid bilayers are composed of phosphatidylcholine and cholesterol. All liposomal
formulations are suspended in sterile phosphate buffered saline (PBS). Liposomes are slightly
negatively charged and will therefore not clog together. The liposomes in the suspension are not
sized, meaning that it contains smaller and larger liposomes as well (up to 3 micron). On
average, the size of the liposomes are 1.7 micron.
Clodronate liposomes: a suspension of artificially prepared lipid vesicles encapsulating
clodronate. The concentration of clodronate in the suspension is ca. 5 mg / mL. Clodronate is
encapsulated in the liposomal vesicles in the form of CH2Na2Cl2O6P2 · 4 H2O.
Hazard Identification - None
Procedural Materials and Methods:
1. For intraperitoneal administration, the recommended injection dosis (i.e. 100 µL of
suspension / 10 grams of animal weight) can be increased considerably. This route also
depletes peritoneal macrophages, but will take longer to deplete macrophages in liver and
spleen (ca. 3 days). Depletion is slower and more gradual, since the liposomes have to be
carried from the peritoneal cavity to circulation by lymph flow via the thoracic duct,
which is a passive form of transport.
Waste Generated and Disposal Methods
● Needles and sharps: Must be disposed of in sharps container.
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STANDARD OPERATING PROCEDURE
CLODRONATE LIPOSOMES
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