Nia Shetty
THE HONOR ROLL SCHOOL, Sugarland, Texas, US
Abstract
Cancer is one of the leading causes of death worldwide accounting for nearly 10 million deaths in 2020. Solid tumors make up almost 90% of all cancer cases. Currently, surgery is most commonly used to treat solid tumors like prostate, breast, and thyroid cancers. However, the invasive nature of surgery allows for the possibility of life-threatening complications such as hemorrhage and organ damage. To reduce the risk of these complications, this project tests a novel minimally-invasive treatment for solid tumors by using gold nanoshells and focal laser therapy. Gold nanoshells possess optimal properties for absorbing laser light, thus generating heat locally to kill cancer cells. We hypothesized that introducing tumors with gold nanoshells, in combination with focal laser therapy, would selectively raise the temperature within the tumor to a lethal level (>52°C; body temp+15°C) while minimizing damage to surrounding normal tissue. Two experiments were conducted to evaluate the effectiveness of this approach. In the first experiment, Nanoshell Gel Models and Control Gel (no nanoshells) were heated with max temperature rises noted with thermal camera at 1 & 2 Watts for 1 minute (3 times/group). In the second experiment, a Thyroid Tumor model was created using a nanoshell ellipsoid, embedded in control gel, then heated at 6 watts for 2 minutes. Using a thermal camera, the temperature of the tumor center, tumor edge, and surrounding normal tissue was measured (3 times/group). T-tests were conducted to compare the means and standard deviations of temperature rise of the nanoshell and control groups, and a significant temperature increase was observed in the nanoshell groups over the control groups. The temperature in the tumor center and edge was significantly higher than that of the normal tissue (p-value < .05), providing evidence that gold nanoshells can focally treat solid tumors with minimal side effects, thus potentially speeding up recovery and maintaining quality of life for cancer patients.
Introduction
Cancer is a heartless beast that doesn’t discriminate and affects millions of people all
around the world. In 2022, an estimated 1.8 million cases (1) of cancer were diagnosed in the US,
with 60% being solid tumors. Solid tumors develop in the cells of the body’s organs and tissues,
examples being, breast, lung, colorectal, and thyroid cancer. The most common treatment for
solid tumors is surgery, but this can come with serious side effects such as damaging surrounding
tissue, bacterial infections, and blood clots. In rare cases, surgically operating to remove the
tumor can lead to life-threatening complications, such as organ failure.
A type of solid tumor is thyroid cancer, which affects the thyroid gland that regulates
your metabolism, heart rate, blood pressure, and body temperature. Every year, around 55,000
people are diagnosed with thyroid cancer, common types including papillary and follicular
cancer. The post-surgical complications are muscle spasms, hematomas, and permanent voice
loss.
Minimally invasive procedures are when doctors make one or more small incisions to
operate and cause less damage to the body than with open surgery (2). Eg: laparoscopy,
colectomy, and cholecystectomy. Another type of minimally invasive treatment is laser ablation.
Laser therapy is currently used in prostate cancer, and is guided by specific imaging, to target the
exact area of the tumor (3)
This project aims to explore the use of nanoshells in minimally invasive procedures with
the goal of reducing complications in surgery. A nanoshell is a type of nanostructure that consists
of a thin shell or layer of material with dimensions on the nanoscale. Nanoshells can be used in a
variety of fields, due to their special optical, electrical, and mechanical properties. Gold
nanoshells (AuNS) with their dielectric functions can be used at certain wavelengths to convert
laser light into heat (9). This experiment explores this property of AuNS combined with focal laser therapy at 808nm wavelength to precisely target solid tumors and cause high enough
temperature rise to cause cancer cell death without damaging surrounding tissue. The use of
minimally invasive procedures in combination with nanoshells can further reduce the risk of
complications in surgery. This is because these procedures involve making one or more small
incisions rather than a large open surgery, which can cause less damage to the body and result in
a faster recovery time.
Methods
The experiment started off with gathering the needed materials. Safety precautions were
implemented with the use of laser safety goggles, closed toe shoes and protective gloves. To
make the gels which was the first experiment, gold nanoshells (Nanospectra Inc.), water, green &
blue food coloring, and agarose powder were required. A pipette, scale, fisher vortex, precision
balance, thermometer, microwave, fridge, and hotplate stirrer were also used in assembling the
gels. 50 mL rectangular plastic container, 15 mL centrifuge tubes, 50 mL centrifuge tubes, 250
mL beaker, and 2L steel beaker were the containers necessary to complete this project. For the
second experiment, an ellipsoid cookie cutter was used to create the Thyroid Tumor Model. To
examine the temperature of the gels, an 808-nanometer laser, stand with clamps, thermal camera,
computer with imaging software, and cooling pump were utilized.
The experiments were conducted in a lab under supervision to test the heating of a nanoshell gel
compared to a control gel at different laser powers.
Before the start of the experiment,
● Wear safety goggles and lab attire
● Ensure closed toe shoes are worn
● Wear protective gloves
3.1 Experiment # 1 : Nanoshell vs Control Experiment
Below are the detailed steps of this Experiment
3.1.1 Making of the nanoshell concentration-
● Pour 14 mL water into test tube
● Shake up the nanoshell test tube using vortex
● add 0.07 mL nanoshells to water
● Vortex the test tube
● add 0.07 mL nanoshells to water
● Vortex the test tube
3.1.2 Making the control concentration-
● Add 0.0001 mL green food coloring to 14 mL
water
● Vortex the test tube
3.1.3 Making a 1% gel-
● Heat up 350 grams of water in the microwave
till it reaches 90°C (the temperature which
agarose dissolves in)
● Measure 3.5 grams of agarose on precision
balance and pour into hot water beaker placed
on hotplate w/ stirrer
3.1.4 Making batches of nanoshells & control gels
● .45 mL nanoshells is poured into each of the (3) 50 mL test tubes ( Figure 1 )
● 45 mL of 1% gel is added into each 50 mL test tubes
● Vortex the test tubes ( Figure 2 )
● Pour the nanoshell gel into 50 mL rectangular molds and let it cool until it reaches 35°C (
Figure 3 )
● Pour 45 mL of 1% gel and add .45 mL of control concentration into 50 mL rectangular
molds ( Figure 4 )
3.1.5 Laser Experiment Setup
● Set up consisted of a thermal camera
attached to a laptop for thermal images,
an external laser beam, 808 nanometer
laser generator, and the gel molds as
shown in Figure 5
● Calibrate the laser
● Decided on using 1 watt & 2 watt laser
power for 1 minute
● The thermal camera would capture an
image every 10 seconds
● The diameter of the laser beam was the
7 mm
● Temperature hotspots were selected near the center and edge of this beam
● Repeated the test 2 times for each of the 3 nanoshells gels, and 3 control gels for 1 watt
per min
● Repeated above at 2 watts per min
● The temperature profile for each of the gels was plotted
● The max rise in temperature for the nanoshell groups was averaged and standard
deviation was calculated
● Above was repeated for the control group
● To compare the results, a paired T-TEST was performed and a p-value was calculated to
show if the difference was significant
3.2 Experiment # 2 : Thyroid Model Experiment
3.2.1 Setup
● An ellipsoid shaped cookie cutter was used to cut
the nanoshell and control gel
● The nanoshell ellipsoid was embedded into the
control gel as shown in Figure 6
● Set up consisted of thermal camera attached to a
laptop, laser fiber, 808 nanometer laser generator,
cooling pump, and thyroid molds
● Calibrate the laser
● Introduce the laser fiber with 18 mm active tip
into the thyroid ellipsoid at 5 mm below surface
and at surface level
● Did a laser power test at 2, 4, and
6 watts (6 watts was selected for
a time of 2 minutes as it showed
the greatest temperature rise)
Testing
3.2.2 Testing
● Temperature hotspots were selected near the center of the laser, the edge of the ellipsoid,
and in the control section of the gel
● Repeated 3 times for each of the 2 thyroid gels at 6 watts for 2 min
● The temperature profile for each of the gels was plotted
● The max rise in temperature for the nanoshell groups was averaged and standard
deviation was calculated
● Above was repeated for the control group
● To compare the results, a paired T-TEST was performed and a p-value was calculated to
show if the difference was significant
Results
To compare the results from the two experiments, statistical analysis was performed. In the
Nanoshell vs Control gel Experiment, the maximum temperature increase of the nanoshell and
control gels, as well as their standard deviations, for the following four settings (1 watt for 1 min,
2 watt for 1 min, center, edge) were used in performing T-TEST.
Once the means and standard deviations were calculated, the researcher was curious how they
could prove that there was a significant temperature difference between the nanoshell gels and
control gels. The researcher found out that a T-TEST is a comparison between the means and
standard deviations of two groups to establish a significant difference. In the Nanoshell vs
Control experiment, the maximum temperature rise of the nanoshell and control gels for the
following four settings (1 watt for 1 min, 2 watt for 1 min, center, edge) were used in performing
a T-TEST. In this experiment, when the p-value, the result of a T-TEST, is less than 0.05 it shows
a significant difference.
The p-value for the temperature difference between nanoshell center and control center at 1 watt
for 1 min, is 0.000003819605687
The p-value for the temperature difference between nanoshell center and control center at 2 watt
for 1 min, is 0.000004081363772
The p-value for the temperature difference between nanoshell edge and control edge at 1 watt for
1 min, is 0.00007069349687
The p-value for the temperature difference between nanoshell edge and control edge at 2 watt for
1 min, is 0.00008364348935
These values prove that in all 4 settings, the nanoshell gels had a significantly higher temperature
rise than the control gels.
In the Thyroid Tumor Model Experiment, the max temp. rise and standard deviations of the
center of the thyroid tumor model, edge of the model, and in the control tissue were used in
performing T-TEST.
In the Thyroid Model Experiment, the max temp. rise of the center of the thyroid tumor model,
edge of the model, and in the control tissue were used in performing T-TEST.
The p-value for the temperature difference between tumor center and control tissue in Thyroid
Gel 1, is 0.01081963697
The p-value for the temperature difference between tumor edge and control tissue is Thyroid Gel
1, is 0.03716586406
The p-value for the temperature difference between tumor center and control tissue Thyroid Gel
2, is 0.00163946551
The p-value for the temperature difference between tumor edge and control tissue Thyroid Gel 2, is 0.1192888656
These results prove that the temperature in the center of the tumor raised significantly higher
than the normal tissue when tested at 6 Watts for 2 minutes.
The temperature in the tumor edge vs the control showed significance in Thyroid Gel 1, but did
not reach significance in Gel 2.
Conclusion
The reason behind this experiment was to test if gold nanoshells could be used to selectively
create ablation temperature in a solid tumor with laser-mediated activation without damaging the
surrounding normal tissue. In the first experiment, the researcher heated up 3 nanoshell gels and
3 control gels, at 1 Watt and 2 Watt for 1 minute each. A statistical analysis was then performed,
by averaging the maximum temperature rise, finding the standard deviation, and finally a
T-TEST was conducted to show the significance in temperature rise. It was found that in all 4
comparisons where a T-TEST was performed, the nanoshell gels had a significant higher
temperature rise than the control gels, as the p-values were all less than 0.05.
In the second experiment, the researcher created 2 thyroid tumor models by cutting out a
nanoshell ellipsoid and inserting it into the control gel. Both models were heated up at 6 Watt for
2 minutes. A statistical analysis was then performed, by averaging the maximum temperature
rise, finding the standard deviation, and finally conducting a T-TEST to show the significance in
temperature rise between the center of the tumor, edge of the tumor, and normal tissue. It was
found that the temperature rise in the center of the tumor and the edge of the tumor was
significantly higher than the temperature rise in the normal tissue.
The goal was to increase the temperature in the tumor by at least 15°C which in a real tumor
would be 52°C (body temp. is 37°C). In the Thyroid Tumor Model experiment, the average
temperature rise for the center of the tumor was in the range of 15-22 degrees. The temperature
rise for the edge of the tumor was from 9.3-12.3 degrees. This data was recorded when the laser
setting was at 6 watts for 2 minutes. The researcher believes that in the future, if this experiment
is repeated, and the laser power is at 6 watts for 3 minutes, both the center and edge temperature
will reach temperatures that can cause tumor cell death.
The hypothesis of this experiment was that if gold nanoshells with laser activation are used to
treat solid tumors, then the temperature inside the tumor will rise enough to cause cell death,
while the temperature of the normal tissue will stay low enough to cause no harm.
The hypothesis was proven correct, because gold nanoshells can be used to effectively treat solid
tumors without damaging the surrounding healthy tissue. The data collected in this project
demonstrates that there is a very clear future for focal laser therapy and gold nanoshells as an
alternative treatment method to surgery for solid tumors.
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Acknowledgement
The researcher would like to acknowledge the support of Nanospectra Biosciences, Inc for
providing equipment for this research. Researcher would also like to thank Nanospectra
Bioscienece, Director of Clinical Research for their valuable contributions and expertise in the
field. Their insights and guidance were invaluable in the conduct and success of this study.