Mechanical and Industrial Engineering University of Massachusetts

Amherst, MA, USA

Nanomedicine

Jonathan P. Rothstein

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

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

(Oil)

(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

nm

m to

mm

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

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 brining therapeutics to kill the tumor from inside out.

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

HAuCl4NaBH4

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HSHS

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.

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Tumor Liver Spleen Lungs Heart SkinAcc

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NecroticQuiescentProliferating

Therapeutic

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 around10nm 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

• Over 15 million people worldwide suffer from knee-joint failure each year due to cartilage deterioration and 1 million spinal surgeries are needed every year

• When cartilage breaks down, the resulting contact of bones causes pain, swelling, and loss of movement.

• As observed over the past 250 years, normal (hyaline-type) cartilage is not known to repair itself.

• Mechanism not fully understood, but cartilage cells, chondrocytes, are sparsely distributed in tissue with poor vasculature, and actually continue to deteriorate after a traumatic incident osteoarthritis.

www.allaboutarthritis.com

www.healthsolutionsgroup.com

Current Treatments

• 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.

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.

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 are currently looking at 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

TriblockCopolymer

Micelle

Gel

ReinforcedThrough

Addition of Nanoparticles

[kPa]1-10 100 1000 10,000

hyalinecartilage

???

amorphoushydrogel

crystallineHydrogel

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 are currently looking at 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

TriblockCopolymer

Micelle

Gel

ReinforcedThrough

Addition of Nanoparticles

Rheology of Hydrogels

0.0001

0.001

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10

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100000

0.01 0.1 1 10 100

Frequency (Hz)

Ela

stic

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(Pa)

72L58L72R60R

• 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)

Effect of Nanoparticle Addition on Rheology of Hydrogel

1 10 1000.1

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od

ulu

s (

Pa

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Frequncy (Hz)

78R 25% 78R 25% + laponite 1% 78R 25% + laponite 1.5% 78R 25% + laponite 2.5%

• PEO adsorbs very strongly to laponite

• Result is an additional, stronger network junction that increases modulus

• Only a very small amount of laponite (1%) is required to gel the neat polymer

• Dramatic modulus enhancement is observed shows great promise

• However, laponite is non-ideal because it is not FDA approved for in-vitro use

• Currently looking for the ‘right’ nanoparticle

Laponite Clay

Nanoparticles

Hydroxyapatite (HAP) Nanoparticles

• Hydroxyapatite (a type of Calcium phosphate) is a mineral found in bone and enamel• Bioactive material capable of bonding to living tissue• HAP nanowhiskers are 20-80 nm in width but up to 100’s of nm in length, and they have a

high tendency to aggregate• Can HAP serve as a new junction point? Initial results are promising, but still a work in

progress

• The atomic force microscopy (AFM) is tool that allows us to image the 3D structure of proteins, cells, viruses and bacteria.

• By modifying the tip to attach enzymes, proteins or different chemical groups, we can also measure interaction strengths/energies between these groups and cell etc.

Nanobiology Measurements using an AFM

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

BioMEMS

Biomedical Analysis and Communication System

Disposable Diagnostic BioChip

BioMEMS – Micro and Nanofluidics