Photonic crystals in biology

Poster Session, Tuesday, June 15
Theme A1 - B702
Antibody Targeting of Doxorubicin Loaded Nanoparticles to
HER2 Expressing Cancer Cells
G. Petek en, F. Gürkan A ırcan, Ufuk Gündüz
Middle East Technical University, Biological Sciences
Abstract- Doxorubicin was encapsulated into PLGA nanoparticles with single emulsion solvent evaporation method. Trastuzumab
was adsorbed on the surface of nanoparticles for targeting to HER2 expressing mammary cancer cells.
Delivery of anti-cancer drugs using biocompatible
nanoparticles are likely to provide protection from
degradation, better adsorption, reduced frequency of
administration, and improved therapeutic index. The next
generation of drug delivery systems includes surface
modified nanoparticles in order to get a selective drug carrier
system. Targeting can be achieved via antibodies against
proteins over-expressed on cell membrane. Between 25% and
30% of breast cancers overexpress human epidermal growth
factor receptor 2 (HER2-neu), which is associated with
poorer prognosis and resistance to treatment [1].
Trastuzumab is a humanized monoclonal antibody that is
currently used as a treatment for the cancer type that
expresses HER2 receptor. In this study, anti-cancer drug
doxorubicin was loaded into Poly (lactic-co-glycolic acid)
(PLGA) nanoparticles. Active targeting of nanoparticles via
adsorption of trastuzumab on their surface was aimed. BT-
474 cell line which over-express HER2 receptor was used.
Anticancer drug doxorubicin was encapsulated by PLGA
polymer by using a modified single emulsion solvent
evaporation technique [2]. Doxorubicin was solubilized in
chloroform containing triethylamin. PLGA was dissolved in
this solution. Solution was than added drop wise into the
aqueous phase containing 2% PVA under magnetic stirring
at. Chloroform was evaporated. Hardened nanoparticles were
obtained by centrifugation and washed with distilled water.
Adsorption of trastuzumab was achieved by 24 hours
incubation of antibody with doxorubicin loaded nanoparticles
at different pH values with different antibody nanoparticle
ratios. The incubations were done in PBS at pH values of 5.0,
7.0 and 9.0 with the antibody nanoparticle ratios of 1:1 and
2:1. Amount of the antibody adsorbed on the nanoparticles
was determined by protein assay. Incubation at pH 5.0 and
with the nanoparticle antibody ratio of 1:2, adsorption of
antibodies on nanoparticles’ surface was at maximum.
Surface analyses of unmodified doxorubicin loaded and
trastuzumab adsorbed nanoparticles were done. Scanning
electron microscopy images showed that trastuzumab
adsorption changed the structure of nanoparticles (Figure 1).
During incubation with antibody, nanoparticles were swelled
and their surface became smoother.
Cellular targeting and uptake of unmodified and antibody
coated nanoparticles were investigated with BT-474 cell
culture. Equal amounts of unmodified and coated
nanoparticles were added to the cells and incubated for 4
hours. The cells were then washed to remove nanoparticles
not internalized by the cells or bound to the cell surfaces.
Fluorescence microscopy was then performed. It was
observed that there were significantly higher amounts of
nanoparticles around and inside the BT-474 cells when the
nanoparticles were covered with trastuzumab antibody
(Figure 2).
a) b)
Figure 2. BT-474 cell line incubated with a) unmodified
nanoparticles b) trastuzumab adsorbed nanoparticles
Coated nanoparticles were more likely to be bound to the
cells than non-coated nanoparticles. Results indicated
increased interaction of nanoparticles with the cells when
they are coated with antibody. Increased interactions may be
helpful in internalization of the drug and increasing potency
of the therapy.
While nanoparticles are known to increase the bioavailability
of doxorubicin, trastuzumab adsorption can target the
doxorubicin loaded nanoparticles to HER2 expressing cell.
Further research is in progress in order to indicate specific
targeting of coated nanoparticles to HER2 expressing BT-474
cells.
ufukg@metu.edu.tr
[1] Slamon DJ, Godolphin W, Jones LA, et al. Studies of the
HER-2/neu proto-oncogene in human breast and ovarian cancer.
Science 1989;244:707-712.
a) b)
Figure 1. Scanning electron micrograph of a) unmodified
nanoparticles b) trastuzumab adsorbed nanoparticles
[2] X.S. Wu, Preparation, characterization, and drug delivery
applications of microspheres based on biodegradable
lactic/glycolic acid polymers. In: WiseEncyclopedic handbook of
biomaterials and bioengineering, Marcel Dekker, New York
(1995), pp. 1151–1200.
6th Nanoscience and Nanotechnology Conference, zmir, 2010 252