Engineering Nanomedical Systems
James F. Leary, Ph.D.
SVM Endowed Professor of NanomedicineProfessor of Basic Medical Sciences and
Biomedical EngineeringMember: Purdue Cancer Center; Oncological Sciences Center;
Bindley Biosciences Center; Birck Nanotechnology CenterEmail: [email protected]
BME 695
Lecture 8
Copyright 2011 J.F. Leary
Surface chemistry: attaching nanomedical structures to the core
8.1.1 attachment strategies typically depend on
core composition
8.1.2 but the attachment strategy should not
drive the core choice
8.1.3 the choice of core should still depend on
the desired overall “multifunctional”
nanomedical device
8.1 Introduction – Basic
attachment Strategies
8.2.1 hydrophobic versus hydrophilic core materials
8.2.2 addition of biomolecules for biocompatibility
8.2.3 monofunctional versus bifunctional surface
chemistry strategies – begin with the end in mind!
8.2.4 PEGylation as “stealth strategy” to minimize
opsonification and increase circulation time
8.2.4 pay attention to overall zeta potential during
the surface chemistry process!
8.2 “Surface chemistry” strategies for
attachment of biomolecules to the
core material for biocompatibility
Stabilizing, Biocompatible
Coatings of Core Materials
Adsorption of
ampliphilic diblock
polymers
Chemical coupling
of hydrophilic
polymeric molecules
Linkage of spacer
molecules with
hydrophilic surface
groups
Source: Kumar, C. 2005
8.3 Two main attachment
strategies
8.3.1 Covalent bonding
8.3.2 Non-covalent bonding
8.3.1.1 Advantages
8.3.1.1.1 Very stable
8.3.1.1.2 Can control process of bond disruption for
multilayering
8.3.1.2 Disadvantages
8.3.1.2.1 Can be too stable and difficult to disassemble
8.3.1.2.2 Must be careful to avoid or minimize use of
strong organic solvents that can be cytotoxic
even at trace concentrations
8.3.1 Covalent bonding strategies
General Reaction Scheme for
Carbodiimide Chemistry for Conjugating
Peptides to Nanoparticles
Courtesy of Christy
Cooper
Reaction scheme when using carboxyl-modified nanoparticles
Reaction scheme when using amine-modified nanoparticles
8.3.2 Non-covalent (primarily
electrostatic) Bonding Strategies
8.3.2.1 Advantages
8.3.2.1.1 Can use very gentle chemistries for
biocompatibility
8.3.2.1.2 Chemistry can be very simple layer-by-layer
assemblies
8.3.2.1.3 Easier to disassemble multilayered structures
8.3.2.2 Disadvantages
8.3.2.2.1 Instability - different pH and ionic strength
environments can cause layers to
spontaneously disassemble at undesired times
8.3.2.2.2 Zeta potential can suddenly change as layers
spontaneously strip off
Example: Four Common Approaches to Hydrophilic
Surface Modification of TOPO stabilized Quantum dots
Thiol +
carboxyl
hydrophilic
end
2 Thiol +
carboxyl
hydrophilic
ends
Stable silane
shell with
crosslinking
Stabilization
of TOPO
layer with
PEG or other
polymersSource: Kumar, C. 2005
Example: More complicated strategies: Coupling
PEG and folate to an iron oxide nanoparticle
Source: Kumar, C. 2005
8.4.1 Preparing the nanoparticle for addition of
targeting and therapeutic molecules
8.4.2 What are the special requirements, if any,
for these molecules?
8.4.3 Testing for targeting an efficacy at the
single cell level
8.4 Introduction
Structure of water dispersible iron oxide
nanocrystals (R stands for a functional group,
e.g. –COOH).
Cryo-TEM photograph of
water dispersible iron oxide
nanocrystals.
Example: Aqueous dispersion of monodisperse
magnetic iron oxide nanocrystals
Source: Yu et al. Nanotechnology 17 (2006) 4483–4487
Figure 1. (a) One-step in situ
DNA functionalization of
CdSe@ZnS core–shell QDs.
(b) photolumines-cence (PL)
spectra of CdSe core QDs and
the DNA-capped CdSe@ZnS
core–shell QDs. Both the green
and red QDs show a significant
increase of the QY after growth
of the ZnS shell and DNA
capping, simultaneously. The
intensities were normalized by
green CdSe@ZnS core–shell
QDs. (c, d) TEM images of
green and red core–shell QDs,
respectively. Higher-
magnification images of
individual dots are shown in the
insets.Source: Wang et al. Angew. Chem.
Int. Ed. 2008, 47, 316 –319
Example: Direct capping of QDs with thiolated DNA
oligonucleotides
The procedure for formation of pPEGMA-coated MNPs and
subsequent conjugation of biotin.
Source: Kang Macromol. Res., Vol. 17, No. 4, 2009
Example: Formation of pPEGMA
(PEG methacrylate)-coated MNPs with biotin
8.5.1 antibodies
8.5.2 peptides
8.5.3 aptamers
8.5.4 small molecule ligands (e.g. folate)
8.5 Attaching different types
of targeting molecules
(some types and examples)
8.5.1 Attaching antibodies and
peptides to Nanoparticles
� Usually done with “soft aqueous chemistry”
involving bonding to carboxyl (COO - ) or amine
(NH2) groups on surface of nanoparticles
� May need molecular spacer arms of 8-12
carbons to give good access (reduce steric
hindrance problems) of antibodies and peptides
Figure 1. a) Schematic
illustration of the TCL-
SPION–Apt bioconjugate
system; b) confirmation of
TCL-SPION–Apt
bioconjugate formation by
gel electrophoresis (1. 100-
bp ladder; 2. A10 aptamer;
3. TCL-SPION–Apt
bioconjugate; 4. TCL-
SPION).
8.5.3 Superparamagnetic Iron Oxide Nanoparticle–
Aptamer Bioconjugation
Source: Wang et al. ChemMedChem
2008, 3, 1311 – 1315
8.6.1 Ways of detecting this complex
8.6.2 Ways of assessing targeting/mis-
targeting efficiency and costs of mistargeting
8.6.3 Is the nanoparticle still attached to the
targeting molecule?
8.6 Testing the nanoparticle-
targeting complex
8.7.1 antibody therapeutics - need to interact with
the immune system to activate
8.7.2 peptides (e.g. apoptosis-inducing peptides)
8.7.3 therapeutic aptamers
8.7.4 transcribable sequences
8.7.5 small drugs
8.7 Attaching/tethering different types
of therapeutic molecules
Figure 1. Design of a multifunctional nanoparticle for siRNA delivery. Because of
their photostable fluorescence and multivalency, QDs are suitable vehicles for
ferrying siRNA into live cells in vitro and in vivo. Conjugation of homing peptides
(along with the siRNA cargo) to the QD surface allows targeted internalization in
tumor cells. Once internalized, these particles must escape the endolysomal
pathway and reach the cytoplasm to interact with the RNA-induced silencing
complex (RISC), which leads to degradation of mRNA homologous to the siRNA
sequence. Source: Derfus et al. Bioconjugate Chem., Vol. 18, No. 5, 2007
Example: Design of a multifunctional
nanoparticle for siRNA
8.8.1 direct and indirect ways of detecting the
therapeutic molecules
8.8.2 ways of assessing the therapeutic efficacy
at single cell level
8.8.3 Is the nanoparticle still attached to the
therapeutic molecule? Is that important?
8.8 Testing the nanoparticle-
therapeutic molecule complex
8.9.1 Little is known about complex nanoparticle
pharmacodynamics
8.9.2 Obtaining quantitative biodistribution data is
extremely difficult!
8.9.3 Some possible new approaches
8.9 Nanomedical pharmacodynamics
– the great unknown!
Lecture 8 References
1. Bagwe, R.P., Hilliard, L.R., Tan, W. “Surface Modification of Silica Nanoparticles to
Reduce Aggregation and Nonspecific Binding” Langmuir 22: 4357-4362 (2006).
2. Derfus, A.M., Chen, A.A., Min, D-H, Ruoslahti, E., Bhati, S.N. “Targeted Quantum
Dot Conjugates for siRNA Delivery” Bioconjugate Chem. 18: 1391-1396 (2007).
3. Hwu, J.R., Lin, Y.S., Josephrajan, T., Hsu,M-H, Cheng, F-Y, Yeh, C-S, Su, W-C,
Shieh, D-B. “Targeted Paclitaxel by Conjugation to Iron Oxide and Gold
Nanoparticles” J. Am. Chem. Soc. 131, 66–68 (2009).
4. Kang, S.M., Choi, I.S., Lee, K-B, Kim, Y. “Bioconjugation of Poly(poly(ethylene
glycol) methacrylate)-Coated Iron Oxide Magnetic Nanoparticles for Magnetic
Capture of Target Proteins” Macromolecular Research, 17( 4): 259-264 (2009).
5. Kumar, C.S.S.R Biofunctionalization of Nanomaterials. Nanotechnologies for the
Life Sciences Volume 1. Wiley-VCH Verlag GmbH & Co. Weinhaim, Germany. 2005.
6. Wang, A.Z., Bagalkot, V., Vasilliou, C.C., Gu, F., Alexis, F., Zhang, L., Shaikh, M.,
Yuet, K., Cima, M.J., Langer, R., Kantoff, P.W., Bander, N.H., Jon, S., Farokhzad,
O.C. “Superparamagnetic Iron Oxide Nanoparticle–Aptamer Bioconjugates for
Combined Prostate Cancer Imaging and Therapy”. ChemMedChem 3: 1311–1315
(2008).
7. Wang,Q., Liu, Y., Ke, Y., Yan, H. “Quantum Dot Bioconjugation during Core–Shell
Synthesis” Angew. Chem. Int. Ed. 47: 316 –319 (2008).
8. Yu, W.W., Chang, E., Sayes, C.M., Drezek, R., Colvin, V.L. “Aqueous dispersion
of monodisperse magnetic iron oxide nanocrystals through phase transfer”.
Nanotechnology 17: 4483–4487 (2006).
