Nanomedicine

First, a short video

https://www.youtube.com/watch?v=2VcNpl8-PRI&feature=youtu.be

From the European Nanomedicine Nanotechnology Platformhttp://www.etp-nanomedicine.eu/public

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/

See also https://commonfund.nih.gov/nanomedicine/index (US National Institutes of Health)

Introduction

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

Nanoparticles for Pathogen Detection

• 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.

Nanoparticle Probe Targeted RNAFluorophore Release

Nanoparticles for Targeted Detection of Cancer

• 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.

Breast Cancer Cells Healthy Cells

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

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.

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.

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First Successful Nanomedicine - Abraxane

Making Gold Nanoparticles

• AuCl4- salts are reduced using NaBH4 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

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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

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.

biomed.brown.edu

Important to tissue engineering:Cells will differentiate purely based on mechanical stimulus.

Important to tissue engineering:Cells will differentiate purely based on mechanical stimulus.

Genzyme ACT method: FDA approved 1997

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

CMC Gelation

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Addition of Nanoparticles

Rheology of Hydrogels

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• 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 (370C).

• 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.

R-LactideAmorphous Core

L-LactideCrystalline Core

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

Introduction – Goals of Nanomedicine

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

• Goal is to develop handheld diagnostic devices for personalized medical testing and treatment

BioMEMS for Screening and Diagnostics

Biomedical Analysis and Communication System

Disposable Diagnostic BioChip

BioMEMS – Micro and Nanofluidics

UMass Institute for Applied Life Sciences (IALS)

http://www.umass.edu/ials/

See also the IALS Center for Personalized Health Care Monitoringhttp://www.umass.edu/cphm/

Extra slides

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-μm-diameter colloidosome composed of 0.9- μm-diameter polystyrene spheres.

P Interfacial Area = A

Energy = AO/W + 4R2P/O

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(Water)

Energy = (A-R2)O/W + 2R2P/O + 2R2P/W

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

[Pickering (1907); Pieranski PRL 45, 569 (1980)]

I. Particle (P) away from interface:

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

Why Particles Adsorb to Interfaces

surface tension

Nanoparticles At Interfaces

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oil-nanoparticle suspension,w/ droplets

water droplet:

• Nanoparticles can be functionalized, cross linked or sintered to make shell permanent, strengthen shell or change shell permeability.

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.

• Can also allow encapsulation of hydrophobic drugs which are difficult to get into you mostly water body.

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Nano-Encapsulated Drug Delivery

Standard Diffusion Based Drug Delivery