cancer therapy using em feild

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DEPT.OF ECE CANCER THERAPY BY HEATING OF GNPs USING EM FIELD

JOHN COX MEMORIAL CSI INSTITUTE OF TECHNOLOGY

CHAPTER 1

INTRODUCTION

Although RF and microwave electromagnetic (EM) fields have been used for

tissue heating for many years renewed attention has been given to the EM-field

approach, a method combining a noncontact, capacitive coupled E-field arrangement

with electrically conductive particles to heat tissue. It is well known that systemic

chemotherapy has serious, debilitating side effects, frequently without producing a

substantial increase in survival.

In this method, RF current passes through a medium without physical contact

between the medium and the transmitter – receiver pair, thus avoiding the need for

contact electrodes. The noncontact approach is appealing for treating small animals

and for whole-body treatment of various systemic cancers, which would preclude the

use of contact electrodes. Additionally, RF-EM fields can penetrate deeply within

tissue, thus making the method promising for treating a wide range of cancers,

potentially anywhere within the human body.

The concept goes a step further from traditional RF-hyperthermia by

incorporating metal ions or metal particles to enhance heating in localized regions as

compared to surrounding regions, where enhancers are not present. Low

concentrations of conductive nanoparticles consisting of gold nanospheres or carbon

nanotubes cause dramatically increased absorption of RF-EM energy, which is then

dissipated in the form of heat. It has also been demonstrated that metal ion solutions

produce a similar effect.

Radiation therapy (also called radiotherapy, X-ray therapy, or irradiation) isthe use of ionizing radiation to kill cancer cells and shrink tumors. Radiation therapy

can be administered externally via External Beam Radiotherapy (EBRT) or internally

via brachytherapy. The effects of radiation therapy are localised and confined to the

region being treated. Radiation therapy injures or destroys cells in the area being

treated (the "target tissue") by damaging their genetic material, making it impossible

for these cells to continue to grow and divide. Although radiation damages both

cancer cells and normal cells, most normal cells can recover from the effects of

radiation and function properly. The goal of radiation therapy is to damage as many

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cancer cells as possible, while limiting harm to nearby healthy tissue. Hence, it is

given in many fractions, allowing healthy tissue to recover between fractions.

Radiation therapy may be used to treat almost every type of solid tumor,

including cancers of the brain, breast, cervix, larynx, lung, pancreas, prostate, skin,

stomach, uterus, or soft tissue sarcomas. Radiation is also used to treat leukemia and

lymphoma. Radiation dose to each site depends on a number of factors, including the

radiosensitivity of each cancer type and whether there are tissues and organs nearby

that may be damaged by radiation. Thus, as with every form of treatment, radiation

therapy is not without its side effects.

Gold NanoParticles (GNPs) have been the primary catalyst for the technique,

likely due to their biocompatibility and potential for creating functionalized bioactive

chemistries.Mechanistic studies have primarily been performed in suspensions of

GNPs in distilled and deionized water (ddH2O), and normal saline. Results indicate

that RF-EM heating applied to solutions containing a suspension of 5 nm diameter

GNPs experience significant heating in ddH2O. Using the RF therapy device, the

heating of ddH2O solutions containing Au concentrations ranged from 1.1 to 67 μM

(0.217 – 13.2 μg/mL), with concentration-dependent temperature increases in 1 mL

solutions of up to 80◦

C (heating from 20 to 100◦

C) using 800 W of 13.56 MHz RF

exposures after 60 s of heating. Capacitively coupled shortwave radiofrequency

fields (13.56 MHz) resistively heat low concentrations (~1 ppm) of gold nanoparticles

with a thermal power dissipation of ~380 kW/g of gold. Smaller diameter gold

nanoparticles (< 50 nm) heat at nearly twice the rate of larger diameter gold

nanoparticles (≥50 nm), which is attributed to the higher resistivity of smaller gold

nanostructures. A Joule heating model has been developed to explain this

phenomenon and provides critical insights into the rational design and engineering of

nanoscale materials for noninvasive thermal therapy of cancer.Nanoparticle-enhanced

thermal destruction of tumors has been demonstrated by using Near Infrared (NIR)

light to heat gold nanoshells or by using strong alternating magnetic fields to heat iron

oxide nanoparticles . Although these methods show significant promise in treating

cancer, they have disadvantages that limit their practicalimplementation as therapies.

Magnetic field-based hyperthermia is effective at treating deep tissue cancer,

but suffers from limited thermalization by iron oxide nanoparticles. The highest





reported thermal power dissipation by iron oxide is a relatively low ~500 W/g of

nanomaterial (at magnetic field amplitude of ~11 kA/m). Therefore, the

concentrations of iron oxide required for effective therapy are much higher than can

be reasonably achieved in vivo. Recently, it is shown that gold nanoparticles heat

under capacitively coupled radio frequency fields. RF heating of gold nanoparticles

within cancer cells overcomes the major limitations associated with other noninvasive

nanoparticle heating methods, since RF energy penetrates well into the body to

efficiently heat gold nanoparticles within deep tissue tumors. Previous studies

evaluated the therapeutic benefits of capacitive RF heating of gold nanoparticles, but

the mechanism of thermalization of RF energy by gold nanoparticles has remained

unaddressed and poorly understood.

A primary objective of this paper is to present and explore the RF-EM therapy

method, from the circuit design and characterization, to the experimental application

of the method for heating GNP suspensions, characterization of GNP heating, and

exploration of the potential for cancer therapy in vitro.

Colloidal gold is a suspension (or colloid) of sub-micrometre-sized particles

of gold in a fluid — usually water. The liquid is usually either an intense red colour

(for particles less than 100 nm), or a dirty yellowish colour (for larger particles) Dueto the unique optical, electronic, and molecular-recognition properties of gold

nanoparticles, they are the subject of substantial research, with applications in a wide

variety of areas, including electron microscopy, electronics,nanotechnology, and

materials science.Properties and applications of colloidal gold nanoparticles strongly

depend upon their size and shape. For example, rodlike particles have both transverse

and longitudinal absorption peak and anisotropy of the shape affects their self-

assembly Chrysotherapy (or aurotherapy), often self-administered allegedly by

alchemists and snake oil vendors before modern medicine isolated effective

compounds, relates to the intake of gold salts and or colloidal gold. Although

colloidal gold has been successfully used as a therapy for rheumatoid arthritis in

rats one noticeable side-effect in humans to whom are administered gold

based DMARDs is the coloring of the skin in shades of mauve to a purplish dark grey

when exposed to sunlight, if the salts are taken on a regular basis over a long period of

time. Excessive intake of gold salts and colloidal gold while undergoing

chrysotherapy result -through complex redox processes- in the saturation by relatively

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stable gold compounds and colloidal gold of skin tissue and organs (as well as teeth

and ocular tissue in extreme cases), a condition known as chrysiasis, similar to a

certain extent to argyria which is related to silver salts and colloidal

silver. Chrysiasis can ultimately lead to acute renal severe heart conditions,

hematologic complications(leucopenia, anemia) : while some effects can be healed

with moderate success, the pigmentation of the skin is considered permanent One of

these special uses of gold refers to what is called ‗nanogold‘, ‗colloidal gold‘ or ‗gold

nanoparticles‘, i.e. sub-micrometer-sized particles of gold dispersed in a fluid, usually

water. The existence of these special gold particles has been known to people since

ancient times, yet it was in 1850s that scientists focused their full attention on them.

The main reasons behind this interest for gold nanoparticles are their extraordinary

optical, electronic and molecular-recognition properties. These properties allow for

the gold nanoparticles to have applications in various fields, including electron

microscopy, electronics, nanotechnology and materials science.

Biological electronic microscopy is one of the areas where gold nanoparticles

have been extensively used as contrast agents. They can be associated with many

traditional biological probes such as antibodies, lectins, superantigens, glycans,

nucleic acids and receptors. Because gold particles having various sizes can be easily

spotted in electron micrographs, it is possible for multiple experiments to be

conducted simultaneously.In what concerns the domain of health and medical

applications, gold nanoparticles have been successfully used as part of the treatment

for some diseases. Rheumatoid arthritis was among the first conditions where use of

gold was part of the therapy since it has been found that gold particles implanted near

the arthritic hip joints relieve pain. There have also been some in vitro experiments

which have proved that gold nanoparticles combined with microwave radiation can

destroy the beta-amyloid fibrils and plaque which are characteristic for Alzheimer‘s

disease. But perhaps the most important medical purpose for which gold nanoparticles

can be used is the localization and treatment of cancer. It has already been shown that

by directing gold nanoparticles into the nuclei of cancer cells, they can only not

hinder them from multiplying, but also kill them. For the modern society of today

gold has become more than just merchandise and by buying it we do not just secure

our investments, but our health as well. With the help of science, researchers have

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been able to explore the great latent potential gold has. Just like the professionals in

the business whose opinion is of great value for the buyers, specialists in important

areas such as medicine can testify about gold‘s benefits too.





CHAPTER 2

BACKGROUND

2.1 RF-EM CIRCUIT DESIGN CONSIDERATIONS

Several modeling approaches were utilized in the analysis of the circuit design.

A circuit mesh equation analysis using MathCad was first performed, followed by a

two-port model with a two variable solver routine to find the best values of C 1 and C 2

to use for tuning. Analysis was also performed with a SPICE circuit modeling

package to make additional verifications against laboratory and mesh model data. The

circuit-tuning technique involves the measurement of the reflected power at the input

node, which can be accomplished with a vector network analyzer. Correct circuitoperation occurs when the reflected power is low and can be assessed with the voltage

reflection coefficient at the input node.

The design utilizes a cascaded LC matching network to transmit 13.56 Hz electrical

energy from a standard 50 Ω source across an air gap to a receiving circuit that steps

down the impedance to a 50 Ω load. Since an air gap presents large reactive load

impedance, several LC sections are necessary to match to the load (three sections for

transmission matching and three for reception matching), while maintaining

reasonable component values and immersions; hence, this mode is referred to as a

transmission-mode design. Tissue-like samples placed within the gap modify the load

impedance, and consequently, tuning of both the transmission and receiving circuits is

necessary to minimize power reflected back into the generator and maximize power

transmitted across the air gap. A modest amount of energy is absorbed from the

applied E-field by samples placed within the gap.

Radiation dose to each site depends on a number of factors, including theradiosensitivity of each cancer type and whether there are tissues and organs nearby

that may be damaged by radiation. Thus, as with every form of treatment, radiation

therapy is not without its side effects.





RESONANT MODE DESIGN

Fig 2.1

Resonant mode‖ RF-EM circuit with the major circuit components labeled and in the

loss resistances associated with the inductors and the C 2 capacitor are omitted for brevity. Rt andCt are the resistance and capacitance, respectively, of the sample placed

in the gap.

A practical resonant-mode schematic shown in Fig. (a) includes three LC stages to

produce an easily adjusted circuit, which provides a real 50 Ω input through the use of

multiple, nonidentical s-plane poles. The voltage is increased at the output of each

stage, which culminates in a very large voltage available as the E-field source for

noncontact heating.

In Fig. a high capacity voltage source (Vs) operating at 13.56 MHz (f0)with output

impedance (Rs) of 50 Ω drives the passive circuit. All thr ee inductors L1 , L2 , and L3

are custom made from soft copper refrigerator tubing. L1 and L3 are wound using

6.35-mm diameter copper tubing and L2 is wound using 4.76-mm diameter copper

tubing. The capacitors C1 and C2 are adjustable. C1 consists of a 500 ± 20% pF fixed

door-knob capacitor in parallel with a 20 – 450 pF air-variable capacitor , C2 is a 10 –

110 pF vacuum variable capacitor. The C3 component is a lumped equivalent

capacitance created from a ground shield around the L3 inductor; the C4 capacitor is a

parasitic component, and the two Ccp capacitances are the air coupling capacitances

to the sample shown as a simple RC element. Very important loss components for the

three inductors as well as for the variable capacitor C2 are considered, but omitted in

the figures for brevity. The loss resistances are all in series with their respective L or

C component. The real part of the input power delivered to the RF-EM circuit will be

divided unequally among these loss components and the Rt in the intended load.





2.1.1. PHYSICAL CIRCUIT OF RESONANT MODE

In the circuit individual components are labeled.C3 is the parasitic capacitance

formed between a sheet of copper clad and the grounded shield labeled to the left (and

the ground plane). L3 is hidden from view inside the grounded shield, and C4 is the

distributed parasitic capacitance between L3 and the shield (including the ground

plane). The sample placed in the gap consists of a 2-mL Eppendorf tube containing a

green neon lamp, which is illuminated in the RF-EM field. The circuit is tuned by

adjusting C1 and C2 via the control knobs shown in order to minimize reflected

power.

2.1.2. CAPACITIVE RF HEATING SYSTEM

Fig 2.2 Capacitive Heating System

A 13.56 MHz signal is applied across two metal electrodes that are coated with an

insulating Teflon layer which produces a high-voltage RF field (|E| = 15 kV/m at 600

W of RF generator power) over a variable air gap. Gold nanoparticle suspensions

contained within a cylindrical cuvette are placed on a Teflon platform (not shown) between the two electrodes. The metal chassis contains high voltage matching circuits





to efficiently produce RF fields between the electrodes.

Radiofrequencies are far below the electronic resonance frequencies for gold

nanoparticles, which are typically in the infrared visible spectrum; because of this,

capacitive coupling to the RF field dominates the movement of charge through

nanoparticles. Therefore, the amount of Joule heat generated by each gold

nanoparticle under RF oscillations can be directly estimated by approximating gold

nanoparticles as conductors of constant cross section.The temperature of the cuvette

was continuously monitored using an infrared camera and thermal emissions were

recorded . All colloidal suspensions were exposed to RF fields until they reached a

final temperature of 70°C or for a maximum duration of 2 min, whichever was

achieved first.

2.3 POWER DELIVERY TO A SAMPLE IN A NON- CONTACT

RF-EM FIELD

A theoretical model for the operation of the RF-EM circuit may be developed

by examining the heating (or electrical power delivery and dissipation) in a small

electrically conductive liquid sample suspended in an E-field without direct electrical

contact to the field electrodes. In effect, the heating of a sample involves determining

the equivalent resistance and capacitance of the sample in addition to the coupling

capacitances. Here, it is assumed that C cp is the same on either side of a sample of

saline, with dependent sample model components of resistance Rsal(σ sal ), where σ

sal is the saline conductivity, and capacitance C sal (T ), where T is the temperature.

In a noncontact RF-EM system. A 0.5-mL sample is shown between two 1-cm

diameter electrodes; a fluoroptic sensor measures temperature postheating





Fig 2.3.Macroscopic modeling of the E-field exposed sample





Using the model, the real power delivered to the saline medium as a function of saline

conductivity σ salt a frequency f shows the dissipation power peak at a

salineconductance of





CHAPTER 3

METHODS

3.1.RF-EM CIRCUIT MODELLING

Several modeling approaches were utilized in the analysis of the circuit

design. A circuit mesh equation analysis using Math Cad was first performed,

followed by a two-port model with a two variable solver routine to find the best

values of C 1 and C 2 to use for tuning. Analysis was also performed with a SPICE

circuit modeling package to make additional verifications against laboratory and mesh

model data. The circuit-tuning technique involves the measurement of the reflected

power at the input node, which can be accomplished with a vector network analyzer.

Correct circuit operation occurs when the reflected power is low and can be assessed

with the voltage reflection coefficient at the input node.

The three custom inductors and the two adjustable capacitors were directly

measured for use in the circuit modeling. The modeling of the effective series loss

resistance for each of the three custom-built inductors was found to be critically

important to a reasonable estimation of circuit operation. The loss resistances have theundesirable effect of power consumption (especially L2 ), but otherwise provide

easier circuit tuning, since absolutely zero resistive loss would create very high Q

elements resulting in difficult tuning adjustments as component values change with

temperature and thermal expansion.

Since capacitances C 4 and C cp are very small, the direct measurement of

these components is extremely challenging. To arrive at reasonable estimates of these

values, a Finite-Element Analysis (FEA) model was assembled for their estimationusing a charge integration (ΣQ) technique on the metal surface of the electrodes at

unity voltage with the application of ΣQ = CV . Both C 4 and C cp were estimated by

dividing theelectrode surface into regions contributing to one or the other capacitance.

The size and morphology of all nanoparticles were confirmed using Transmission

Electron Microscopy(TEM). TEM was performed using a JEM 1010 transmission

electron microscope with an accelerating voltage of 80 kV and digital images were

acquired usingan AMT Imaging System (Advanced Microscopy ). Drops ofnanoparticle suspensions were placed onto a poly- L-lysine treated form var coated





copper grid for 1 h. Grids were blotted dry with filter paper and air dried before TEM

observation all gold concentrations are reported in ppm by mass and were determined

In order to independently examine nanoparticle diameter and gold contenteffects under RF fields, we tested gold nanoshells. Since nanoshells are composed of

an inner dielectric core (SiO2) and a thin outer shell of gold, the total volume fraction

of gold in solution can be varied while holding the overall diameter of the

nanoparticle constant. Surprisingly, at equivalent gold volume fractions, 150 nm

diameter gold nanoshells (ca. 10 15 nm gold shell thickness) exhibit RF heating rates

comparable to solid gold nanoparticles ≤20 nm in diameter. Note, that in a control

experiment 120 nm diameter uncoated silica nanoparticles exhibited an RF heatingrate equivalent to that of water

3.2. RF-EM POWER DELIVERY TO SALINE SOLUTIONS

To refine estimates of critical circuit model component values, a comparison was

made of the 1) power required to heat a sample by a forward calculation using the

circuit model and sample component values, and 2) the power required in a FEA of

heating the same sample.

A laboratory study was conducted to find the peak heating for a sample heated

with the RF-EM system. A series of 0.5 mL samples were prepared in a serial dilution

range of ten concentrations from standard 0.9% normal saline (0.154 M) to a dilution

of 1/512 in concentration. Each of three samples at each dilution was heated for 30 s

with 125 W of input power to the RF-EM system. A 0.5-mm fluoroptic temperature

probe was placed in the heating tube before and immediately after E-field exposure.





3.3. RF-EM POWER DELIVERY TO GNP SOLUTIONS

Colloidal suspensions of citrate-coated GNPs in nominal diameters of 5, 10, 20,

and 50 nm in nominal concentrations of 0.01% Au are taken. A series of 0.5 mL

samples of GNP suspension with varying concentration was placed in 2 mLEppendorf tubes. The region of the tube containing the fluid sample was centered

between two 17 -mm diameter copper electrodes spaced apart by 17 mm, allowing

approximately a 4-mm air gap on either side of the tube . With a sample in place, the

circuit was tuned using the VNA to minimize reflected power (S 11) to better than – 30

dB at 13.56 MHz. After tuning, the circuit was connected to a 1000 W capacity 13.56

MHz RF generator, Prior to RF-EM exposure, the initial temperature of each sample

was measured using the fluoroptic temperature probe. The fluoroptic probe was

removed, and each sample was exposed to 125 W of input power to the RF-EM

system for 30 s. Following exposure, the peak temperature in the center of the sample

was measured.

Heating efficiency was quantified as power per unit mass of Au, i.e., kW/g Au,

which allows for the comparison of heating efficacy of various sizes and

concentrations for a given RF delivery system. Throughout this work this quantity is

referred to as the specific heating rate.





CHAPTER 4

RESULTS

4.1. CHARACTERISTICS OF THE CIRCUIT

The circuit with its estimated component values has been extensively modeled.

For good power transfer at each node, the output and input impedances should be

matched as complex conjugates; this circuit functions well in that regard. The circuit

node terminus produces an output impedance magnitude that is over 3100 Ω and an

output voltage peak above 8800 V (for 125 W input). This high impedance andvoltage make a direct sampling method challenging even with a very high impedance

probe (we used a 40 MΩ sampling probe).

A special E-field probe has been constructed and tested to calibrate the high

E-field generation, but even this carefully designed miniature probe has shown field

loading effects. Alternative measurement methods are in development to enable easy

and accurate monitoring of the field generated.

In figure 4.1 Normalized transfer response magnitude in decibels versus frequency in

megahertz for VNA measured (solid), Mathcad model (dotted), and SPICE model

(dashed). All results are normalized to the peak response at 13.56 MHz for the same

input magnitude. The Mathcad and Spice models are equivalent as indicated by the

near exact agreement between their respective curves. Agreement between the model

and experiment is reasonable considering many parasitic capacitances distributed

throughout the circuit that were not modeled. The influence of parasitic capacitance

due to the measurement is apparent near 13.56 MHz, where the measured response is

approximately 6 dB below the prediction.





Fig 4.1 Normalized Transfer Responce





4.2 GNP HEATING

The concentrations of the stock GNP solutions for 5, 10, 20, and 50 nm were

found to be 59, 54, 59, and 75 μg/mL, respectively. Temperature increases measured

in 0.5 mL samples of 5, 10, 20, and 50 nm GNP solutions following 30 s exposures inthe RFEM field using 125 W of transmitted power are summarized in Fig. 5. Heating

is inversely dependent on particle size and directly dependent on concentration up to

approximately 25, 40, 45, and 55 μg/mL for 5, 10, 20, and 50 nm GNPs, respectively.

Beyond these concentrations, heating does not increase with further increases in

concentration. At the highest concentrations, the heating rate ranged from 1.5 to 1.7

.C/s across all particle sizes.

The specific heating rate is inversely dependent on particle size. Exposure of

particles with a diameter of 5 nm resultedin the greatest efficiency with a specific

heating rate of 356 ±78 kW/g Au at a concentration of approximately 16 ìg/mL.

Beyond50 mg/mL, the specific heating rates for all particle sizes appear to follow a

common decreasing trend line. For concentrations below approximately 4 mg/mL, the

heating of water begins to dominate, thus explaining the asymptotically increasing

specific heating rate as zero Au concentration is approached (divide by zero condition

Fig. 4.2.Temperature rise of GNP suspensions in ddH2O

Following 30 s exposure to transmitted power of 125 W. Square, circle, diamond, and





triangle data point labels denote 5, 10, 20, and 50 nm GNPs. Standard deviations for

three trials are shown. The heating is inversely dependent on particle size and directly

dependent on concentration up to approximately 25, 40, 45, and 55 μg/mL for 5, 10,

20, and 50 nm GNPs, respectively. Beyond these concentrations, heating appears to be

unchanged with further increases in concentration.In kilowatt per gram Au

characteristic of GNP suspensions in ddH2O following 30 s exposure to transmitted

power of 125 W. Square, circle, diamond, and triangle data point labels denote 5, 10,

20, and 50 nm GNPs. Standard deviations for three trials are shown. The specific

heating rate is inversely dependent on particle size, with 5 nm being the most efficient

particle size for heating with a specific heating rate of 356 ± 78 kW/g Au at a

concentration of approximately 16 μg/mL.Beyond 50 μg/mL, the specific heating

rates for all particle sizes appear to follow a common decreasing trend line. For

concentrations below approximately 4 μg/mL, the specific heating rate of water

begins to dominate the heating, thus explaining the asymptotically increasing specific

heating rate as zero Au concentration is approached (divide by zero condition)

4.3. CANCER CELL TREATMENT

Fig. 4.3. Preliminary in vitro results

Percent cell death relative to the 100% kill control is presented for Met-1 and PC-3





cancer cell lines for three RF treatment protocolsconsisting of 60 s of RF at 100 W, 30

s of RF at 100 W, and no RF. Each treatment group consisted of cells not incubated

with 10 nm GNPs and cells that were incubated with 10 nm GNPs so as to test if the

presence of GNPs influences cell death. For the cells that were incubated with GNPs,

the results shown include all of the cells regardless of GNP uptake. Upon testing the

influence of GNPs for the three treatment groups, a statistically significant increase in

cell death with the addition of 10 nm GNPs occurred for Met-1 cells treated with RF

for 60 s and for PC-3 cells incubated with 10 nm GNPs and treated with RF for both .

Met-1 cells treated for 30 s and incubated with GNPs did not show a significant

increase in cell death . The no-RF controls did not show a significant difference in

death for either Met-1 cells or PC-3 cells . For both cell lines, treatment with RF alone

did produce a significant increase in cell death relative to the no Au, no RF controls .

The maximum temperatures were recorded for the RF-treated cells, and no statistical

difference was found between the temperature rise with and without cells incubated

with GNPs. Average maximum temperatures for the 30 and 60 s treatments ranged

from 53.5 to 55.7◦C and 64.8 to 67.2◦C, respectively. The starting temperatures

averaged across all replicates was 22.6 ± 0.6◦C

The in vitro results presented demonstrate that the combination of cells

incubated with GNPs and exposed to RF causes statistically significant increases in

cell death for both Met-1 and PC-3 cancer cell lines. Significant differences in cell

deathis not observed as a function of GNP presence unless the samples were heated to

above 50◦C.

High temperatures are a prerequisite for the GNP-induced cell death.

Concentrating the cells into a smaller fluid volume may have also played a role inminimizing the shunting of the RF current around the cells and more closely models

tissue. TEM images of PC-3 cells indicate that the combination of GNPs and RF

creates vacuoles within cells, possibly explaining the significantly higher cell death

for RF-treated groups with GNPs. Vacuolization was not observed in RF-treated cells

without GNPs present observed by additionally, degraded GNP aggregates were

consistently observed in RF-treated cells. It may be that as these cells die, lysosomes

break down and release their digestive enzymes and acidic contents into the

cytoplasm, which may lead to degradation of the GNPs.





The characterization of GNP heating in was performed in ddH2O, which is an ideal

medium for maintaining a colloidal suspension of citrate-coated GNPs with minimal

aggregation. Consequently, it may be possible to improve the method by preventing

aggregation of GNPs in carrier solutions and intra cellularly. More work is needed to

understand the mechanism of GNP heating in RF fields. Selective killing of cancer

cells in vivo requires targeting of GNPs directly to cancer cells by means of passive

and/or active targeting. Fortunately, GNPs are readily functionalized and have been

shown to target a wide range of cancers in vitro . Additionally, GNPs have been

shown to target specific organelles within cells, such as the nucleus .studies evaluated

in vivo tumor uptake of Tumor Necrosis Factor (TNF) bound to GNPs with and

without a protective layer of PEGTHIOL. Following intravenous injection in mice,

they found significant accumulation of the PEGTHIOL protected TNFGNPs in MC-

38 colon carcinoma tumors with little observable accumulation in the liver and spleen.

The increased RF induced heating rates of gold nanoparticles <50 nm in

diameter and gold nanoshells 10 -15 nm thick can be explained by the higher

resistivity of small metal nanostructures compared to bulk metals . Recent studies

have shown that the resistivity of silver nanowires 15 nm in diameter is approximately

twice that of bulk silver. Particles and shells of gold with dimensions on the order of10 nm are expected to exhibit a similar increase in resistivity due to increased

electron-surface scattering since the size of the metal is significantly smaller than the

mean free path of electrons in gold, which is on the order of 50 nm .If the heat

released is due to resistive (Ù) dissipation by gold, then the measured heat should

scale with Joule‘s law, P = I2R, where P is the power dissipated as heat, I is the

current, and R is the resistance. For a given volume fraction of gold nanoparticles, an

increase in the resistivity should lead to a commensurate increase in the amount of

heat generated by ohmic dissipation. As such, the observed doubling of the heating

rate for small gold nanoparticles and Nanoshells is consistent with the hypothesis that

gold nanoparticles are heating resistively under capacitive coupled RF fields.

The analysis presented here describes the models we haveconstructed, which

allow the theoretical prediction and comparison with laboratory data of the

temperatures in saline samplesexposed to high intensity E-fields. An expression for

bath temperature as a function of saline concentration is possible withconsideration ofthe 0.5mL bath geometry, physical materialproperties and their variation with





temperature, and a reason-able thermal model for the Eppendorf tube in air. Simple

modelscan be constructed using the electrical equivalent circuit of Using the model

of Fig. 10, the real power deliveredto the saline medium as a function of saline

conductivity σ salt a frequency f shows the dissipation power peak at a

salineconductance of

where ε0 and εsal are the dielectric constants of free spaceand saline, respectively.

Historically, at 13.56 MHz, the peakconductance has been estimated as 0.06 S/m. A

modified modelis now presented, which compares well with laboratory datacollected

for saline bath heating in small plastic Eppendorf tubeswith the EM heating system.A

custom tester has been built, calibrated, and implementedto measure saline bath

conductance σsal (in S/m), as a function of concentration csal (in mol/L). This relation

appears to be approximately linear as expressed by

log10 = 0.9292log10 + 0.8885

and produces less than 10% error with laboratory data in the range of 0.0002 to

0.154M (largest error at bottom of range).With consideration for the cylindrical bath

geometry of the Ep-pendorf tube, the effective saline bath electrical resistance as

afunction of saline conductivity R sal(σsal), and the saline bathelectrical capacitance as

function of temperature Csal( T) can beeasily estimated. The relationship between

temperature and the relative dielectric constant of saline can be approximatedin the

range between 0 and 100◦C with the expression for water





CHAPTER 5

CONCLUSION

A method for heating GNPs using RF-EM radiation has been investigated.

The circuitdemonstrated heating of saline solutions in good agreement with the model

predictions. Such a model is useful for scaling the device up to larger treatment

volumes. Heating of GNP suspensions was demonstrated in ddH2O, and heating and

specific heating rates similar to previously published values were obtained.

Identification of GNP concentrations to produce maximum specific heating rates was

shown, which may be useful knowledge for cancer therapy. In vitro experiments

yielded preliminary results confirming that RF-EM radiation combined with GNPs

has statistically significant cytotoxic effect on cancer cells. More work is needed to

further elucidate the mechanisms of action.





CHAPTER 6

REFERENCES

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cancer therapy using em feild

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