Nanomedicine

Jonathan P. Rothstein

Mechanical and Industrial Engineering University of Massachusetts Amherst, MA, USA

Introduction

• What is nanomedicine?

• It is nanotechnology used for the treatment, diagnosis, monitoring and control of biological systems • It includes the delivery and targeting of pharmaceutical, therapeutic, and diagnostic agents using nanoparticles to cancer and other cells • It includes nanomaterial for bone, cartilage, vascular, bladder and neural applications • What isn’t nanomedicine?

• Flesh eating/repairing nanorobots

Introduction – Goals of Nanomedicine

• End goal of nanomedicine is improved diagnostics, treatment and prevention of disease • For a great review see http://www.wtec.org/nano2/Nanotechnology_Research_Directions_to_2020/

Introduction – Goals of Nanomedicine

• Ultimate goal is to integrate detection, diagnostics, treatment and prevention of disease into a personalized single platform

Introduction

• Nanotechnology holds key to a number of recent and future breakthroughs in medicine

BioMEMS for Screening and Diagnostics

• Goal is to develop handheld diagnostic devices for personalized medical testing and treatment Biomedical Analysis and Communication System Disposable Diagnostic BioChip

BioMEMS – Micro and Nanofluidics

Nanoparticles for Pathogen Detection

Nanoparticle Probe Targeted RNA Fluorophore Release

• Gold nanoparticles can be functionalized with thiolated oligonucleatides.

• Bound to the oligonucleatides are fluorophores which are quenched by their proximity to the nanoparticle.

• When the targeted RNA (H2N2, HIV or a cancer) bindes to the oligonucleatide, the fluorophore is released and becomes fluorescence.

• The fluorescence can be detected in a BioMEMS device.

• Challenge is developing oligonucleatides with high selectivity for the target RNA.

Nanoparticles for Targeted Detection of Cancer

Breast Cancer Cells Healthy Cells

• As an example, nanoparticle probes were developed by Chad Mirkin at Northwestern Univ. that target the survivin RNA sequence known to exist in a certain breast cancers.

• Experiments are done ex-vivo.

• On the left, cancer cells fluoresce.

• On the right, healthy cells show minimal fluorescence.

Nanoparticles for In-vivo Detection of Pathogens

• Fluorescence is not a viable option in-vivo, but magnetic tagging works very well.

• Harmless virus can used as a building block to produce contrast agents that can be used in Magnetic Resonance Imaging (MRI).

• Here, magnetic metal ions are bonded to the virus as are molecules that bind to cancer cells.

• A full body MRI scan detects these contrast agents and even very small tumors throughout the body

Nanoparticle Encapsulation for Drug Delivery

• Nanoparticle shells can be formed around spherical droplets • A.D. Dinsmore,

et al., Science

298, 1006 (2002), Y. Lin,

et al., Science

299, 226 (2003) • Shells are porous at lengthscales much smaller than size of nanoparticle.

A:

Scanning electron microscope of a dried 10 μ m-diameter colloidosome composed of 0.9 μm-diameter polystyrene spheres.

Why Particles Adsorb to Interfaces

[Pickering (1907); Pieranski PRL

45

, 569 (1980)]

I. Particle (P) away from interface:

P Interfacial Area =

A

surface tension (Oil) Energy =

A

g O/W + 4 p

R

2 g P/O (Water)

II. Particle sitting astride the interface (half-in, half-out):

Energy = (

A-

p

R

2

)

g O/W + 2 p

R

2 g P/O + 2 p

R

2 g P/W • If | g P/O – g P/W | < g O/W /2, then adsorption reduces surface energy.

Nanoparticles At Interfaces

oil-nanoparticle suspension, w/ droplets • Nanoparticles can be functionalized, cross linked or sintered to make shell permanent, strengthen shell or change shell permeability.

water droplet: m m to mm nm

Nano-Encapsulation for Drug Delivery

• By making the holes between nanoparticles approximately the same size as the drug you want to administer you can get a constant release rate – avoids spikes in dosage.

Standard Diffusion Based Drug Delivery Nano-Encapsulated Drug Delivery Time • Can also allow encapsulation of hydrophobic drugs which are difficult to get into you mostly water body.

Targeted Delivery to Tumors

• Goal is to inject treatment far from tumor and have large accumulation in tumor and minimal accumulation in normal cells/organs.

Cancer Treatments

• Tumor penetration is a key issue for successful chemotherapy

Nanoparticle use in Cancer Treatments

• Because of their small size, nanoparticles can pass through interstitial spaces between necrotic and quiescent cells.

• Tumor cells typically have larger interstitial spaces than healthy cells • Particles collect in center bringing therapeutics to kill the tumor from inside out.

Making Gold Nanoparticles

HAuCl 4

HS Na BH 4

S S S S S SS S S S S S S S S S

HS HS

S S S S S SS S S S S S S S S S

HS HS HS

S S S S S SS S S S S S S S S S

• AuCl4- salts are reduced using NaBH 4 in the presence of thiol capping ligands • The core size of the particles formed can be varied from <1 nm to ~ 8 nm • The surface functionality can be controlled through the choice of thiols • Diffusion speed can be controlled by length of thiols

Nanoparticles as Sensors and Therapeutics

• Glutathione (GSH) provides a selective and tunable release mechanism • Once inside cells, fluorophores and drugs selectively dissociate

Nanoparticle Success

• Both cationic and anionic particles penetrate and accumulate in tumors.

• However, only cationic particles diffuse fully throughout the tumor.

• Work of Neil Forbes and Vince Rotello at UMASS

Nanoparticle Targeting and Accumulation

• To maximize their effectiveness, the microenvironment of the tumor must be quantified and vectors developed to specifically target the tumor.

• These treatment approaches have shown great promise in mice.

Necrotic Quiescent Proliferating Therapeutic 1,000,000 100,000 10,000 1,000 100 10 0 1 Tumo r Liver Spleen Lungs Heart Skin

First Successful Nanomedicine - Abraxane

Alternatives to Nanoparticles - Surfactants

• Surfactants are composed of a hydrophilic head and a long hydrophobic tail • When dissolved in water above the critical micellar concentration (CMC) surfactants can self-assemble into large aggregate • Spherical micelles are around 10nm in size • Hydrophobic drugs can be encapsulated and in their core and delivered throughout the body or to a specific target.

Nanotechnology in Tissue Engineering – Cartilage Replacement • Samuel Stupp at Northwestern has shown that nanotechnology can be use to regenerate severed spinal cords.

• Two polypeptides amphiphiles are used that when mixed in an aqueous solution self assemble into a nanotube • As seen on right, these nanotubes display peptide growth factors.

• In mice, these systems have been shown to promote axonal outgrowth and bridging of injured areas (bottom right).

Nanotechnology in Tissue Engineering – Cartilage Replacement • Because cartilage doesn’t have vasculature and cannot repair itself, accepted treatments have been mostly

mechanical

in their approach.

• Joint lubricants: • Simple and effective at short-term pain relief but do not address cause of the problem or repair any damage.

• Debridement/lavage/microfracture: • Small lesions are repaired by shaving or shaping contour of cartilage.

• Microfracture penetrates subchondral plate (bone) and actually causes growth of fibrocartilage – a lesser form, not desirable.

• Total joint replacement: • Addresses problem and generally allows full repair, but • Very invasive procedure, native tissue removed • Prostheses do not last a lifetime in active patients.

• Nanotechnology approach • Regrow patient’s own cartillage in-vivo to repair damage

www.hughston.com/hha/

ACT Methods

• A popular tissue engineering approach has been to introduce new cells, via

autologous chondrocyte transplantation/implantation

(ACT/ACI).

• Some of the earliest work by Benya and Shaffer (1982) showed it was possible to isolate and culture chondrocytes.

• More interesting result was that when cultured

in vitro

, the cells differentiated and changed their phenotype to produce a lesser quality collagen. • Need better tissue scaffolds – nanotech.

Genzyme ACT method: FDA approved 1997 Important to tissue engineering:

Cells will differentiate purely based on mechanical stimulus.

biomed.brown.edu

Hydrogels – Self Assembly

• • • • Hydrogels have applications in drug delivery and tissue engineering Regenerating cartilage and other tissue requires scaffolds with similar modulus and other mechanical properties → Need to develop stiffer, tunable hydrogels We investigated Polylactide-Polyethylene Oxide-Polylactide triblock copolymers.

Systems are biocompatible with a hydrophobic ends (PLA) and a hydrophilic center (PEO) which self-assembles in water and can form a gel under the right conditions Triblock Copolymer CMC Micelle Gelation Gel Reinforced Through Addition of Nanoparticles

Rheology of Hydrogels

100000 10000 1000 100 10 1 0.1

0.01

0.001

0.0001

0.01

72L 58L 72R 60R 0.1

1

Frequency (Hz)

10

R-Lactide

Amorphous Core 100

L-Lactide

Crystalline Core • The hydrogels formed are very stiff with elastic modulus on the order of 1-10 kPa.

• Within range of moduli of several human tissues including cartilage.

• Gels formed from polymers with higher degree of polymerization maintain a high storage modulus even at physiological temperatures (37 0 C).

• In-vivo applications feasible.

• Rheological response of these polymers can be easily tuned by varying the crystallinity or block length of PLA or through addition of nanoparticles.

Khaled

et al.

Biomaterials (2003)

Photocrosslinking Hydrogels for Cartilage Replacement

• An alternate approach is to make the hydrogel from polymers that can be crosslinked after injection.

• From Jennifer Elisseeff’s lab at Johns Hopkins University.

• Photo-polymerizing the hydrogel increases its modulus, allowing the appropriate phenotype of cartilage to be expressed and protecting damaged area from wear.

Keeping Things Clean – Antimicrobial Surfaces

• • • Silver is an excellent anti-microbial agent Silver nanoparticles are now being added to fibers of clothing and bandages as well as being incorporated into surfaces in hospitals to reduce the rate of bacterial infections When co-extruded with a polymer like PLLA, the silver is released slowly over time and has been shown to effectively kill bacteria