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: jfleary@purdue.edu

BME 626

September 25, 2014

Lecture 8

Copyright 2014 J.F. Leary

Surface chemistry: attaching nanomedical structures to the core

A. attachment strategies typically depend on

core composition

B. but the attachment strategy should not

drive the core choice

C. the choice of core should still depend on

the desired overall “multifunctional”

nanomedical device

Introduction – Basic attachment

Strategies

A. hydrophobic versus hydrophilic core materials

B. addition of biomolecules for biocompatibility

C. monofunctional versus bifunctional surface

chemistry strategies – begin with the end in

mind!

D. pay attention to overall zeta potential during

the surface chemistry process

“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

Two main attachment strategies

A. Covalent bonding

B. Non-covalent bonding

1. Advantages

a. Very stable

b. Can control process of bond disruption for

multilayering

2. Disadvantages

a. Can be too stable and difficult to disassemble

b. Must be careful to avoid or minimize use of

strong organic solvents that can be cytotoxic

even at trace concentrations

Covalent bonding strategies

Non-covalent (primarily

electrostatic) Bonding Strategies

1. Advantages

a. Can use very gentle chemistries for

biocompatibility

b. Chemistry can be very simple layer-by-layer

assemblies

c. Easier to disassemble multilayered structures

2. Disdvantages

a. Instability - different pH and ionic strength

environments can cause layers to spontaneously

disassemble at undesired times

b. Zeta potential can suddenly change as layers

spontaneously strip off

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

A. Preparing the nanoparticle for addition of

targeting and therapeutic molecules

B. What are the special requirements, if any,

for these molecules?

C. Testing for targeting an efficacy at the

single cell level

I. 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.

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

intensi-ties 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

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

Formation of pPEGMA-coated MNPs with biotin

A. antibodies

B. peptides

C. aptamers

D. small molecule ligands (e.g. folate)

Attaching different types

of targeting molecules

(some types and examples)

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).

Superparamagnetic Iron Oxide Nanoparticle–

Aptamer Bioconjugation

Source: Wang et al. ChemMedChem

2008, 3, 1311 – 1315

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

A. Ways of detecting this complex

B. Ways of assessing targeting/mistargeting

efficiency and costs of mistargeting

C. Is the nanoparticle still attached to the

targeting molecule?

Testing the nanoparticle-

targeting complex

A. antibody therapeutics - need to interact with

the immune system to activate

B. peptides (e.g. apoptosis-inducing peptides)

C. therapeutic aptamers

D. transcribable sequences

E. small drugs

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

Design of a multifunctional nanoparticle for siRNA

A. direct and indirect ways of detecting the

therapeutic molecules

B. ways of assessing the therapeutic efficacy at

single cell level

C. Is the nanoparticle still attached to the

therapeutic molecule? Is that important?

Testing the nanoparticle-

therapeutic molecule complex

A. Little is known about complex nanoparticle

pharmacodynamics

B. Obtaining quantitative biodistribution data is

extremely difficult!

C. Some possible new approaches

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).