Mechanical and Industrial Engineering University of Massachusetts Amherst, MA, USA Nanomedicine...
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Transcript of Mechanical and Industrial Engineering University of Massachusetts Amherst, MA, USA Nanomedicine...
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.
Dru
g C
once
ntra
tion
in P
atie
nt
Time
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
HS
S
S
S
SS
SSSSSS
SS SS
S
HS
HS
S
S
S
SS
SSSSSS
SS SS
S
HSS
S
S
SS
SSSSSS
SS SS
S
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.
0
1
10
100
1,000
10,000
100,000
1,000,000
Tumor Liver Spleen Lungs Heart SkinAcc
umul
atio
n (C
FU
/mg)
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
0.01
0.1
1
10
100
1000
10000
100000
0.01 0.1 1 10 100
Frequency (Hz)
Ela
stic
Mo
du
lus
(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
1
10
100
1000
10000
78R
Ela
stic m
od
ulu
s (
Pa
)
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