Plasmonic Photothermal Cancer Therapy: Nanoparticle-embedded Tumor-tissue-mimicking Phantoms for Visualizing Photothermal Temperature Distribution
May 9th, 2025
This article presents the protocol for preparing tumor-tissue phantoms that replicate optical properties for plasmonic photothermal therapy. It details phantom preparation, photothermal evaluations, and validation of the developed numerical model based on photothermal temperature measurements for assessing therapeutic parameters, offering an ethical, cost-effective alternative to in vivo studies for preliminary testing.
Scope of research basically involves developing tumor tissue and making phantoms for plasmonic photothermal cancer therapeutics to validate the numerical simulations, as well as for specifying the therapeutic parameters for in vivo experiments to assess the therapeutic outcome. This protocol bridges the gap between numerical modeling and experimental validation for plasmonic photothermal therapy, as well as estimation of therapeutic parameters for in vivo evaluation before clinical translation. This protocol offers a cost effective evaluation of plasmonic photothermal interaction for solid tumors using agarose phantoms with thermocouple monitoring, thereby minimizing the need of animals for in vivo testing.
Phantom based evaluation allows validation of simulation to improve treatment accuracy and tuning parameters like nanoparticle concentration and iteration settings to support safe and effective plasmonic photothermal cancer therapeutics. In the future, we want to develop more realistic tumor tissue making phantoms involving melanin, hemoglobin, as well as blood flow. Also, we want to explore the multi-site injections for large tumors.
To begin, design a three dimensional model using CAD software. Click on New, followed by Create to design a hollow cylindrical mold. Press Document Settings and choose Units to change the unit to millimeters.
Design a cylindrical mold with an inner diameter of 40 millimeters and height of 12 millimeters, along with two solid cylindrical masking molds. Use the generated G code to print the molds using a 3D printer with polylactic acid filament. For the preparation of solution one, add 0.35 grams of agarose to 33.18 milliliters of deionized water in a beaker.
Cover the beaker with aluminum foil to prevent water loss. Heat the beaker on a hot plate at 120 degrees Celsius while stirring until the solution becomes transparent. Then decrease the hot plate temperature to 60 degrees Celsius and allow the solution to cool for 15 minutes.
While stirring, add 1.82 milliliters of intralipid solution and continue mixing. For solution two, add 45 milligrams of agarose to 1.18 milliliters of deionized water in a beaker and cover with aluminum foil. After heating and cooling the solution as demonstrated earlier, add 106.2 microliters of intralipid solution and 3.21 milliliters of the gold nanorod suspension while stirring.
Keep solution two under continuous stirring at 60 degrees Celsius until use. To prepare solution three, add 25 milligrams of agarose to 2.44 milliliters of deionized water in a beaker and cover with aluminum foil. Heat and cool the solution.
Then add 59 microliters of intralipid solution while stirring at 60 degrees. For the preparation of tumor tissue-mimicking phantom, first seal the bottom of the cylindrical molds with parafilm. Place the masking mold in the center.
For preparation of the IT phantom, pour solution one into the cylindrical molds up to the top mark of the masking mold. After solidification, remove the masking mold to create a cavity for the tumor region. Next, fill the cavity with solution two and let it solidify.
Then add solution one to the top of the phantom and allow it to fully solidify. For the preparation of the IV phantom, insert a smaller masking mold and fill the cavity around it with solution two. After solidification, remove the smaller mold and fill the remaining cavity with solution three.
Add solution one to the top and allow complete solidification. Next, insert thermocouples within some glass capillaries that have been cut to length. Puncture the phantoms at specified radial and axial locations.
Once all thermocouples are in place, carefully place the phantom in a glass Petri dish for subsequent NIR infrared irradiation. Position the glass Petri dish so that the central region of the phantom's top surface is perpendicular and axially aligned to the optical fiber tip of the NIR infrared light source. Then connect the data acquisition system to the computer and launch the lab view software.
Turn on the NIR infrared light source and start recording temperature data by pressing the play button in the software. Irradiate the phantom for 20 minutes in a dark room. Then switch off the NIR light source and stop the recording.
Now plot the recorded mean temperature versus time data, then plot the mean experimental temperature against the simulated temperature at all thermocouple locations. The temperature rise in the IT distribution of gold nanorod embedded tumor tissue phantom was higher than in the IV distribution due to increased scattering in the IV distribution. The maximum temperature rise was approximately 11 degrees Celsius for the IT distribution and six degrees Celsius for the IV distribution at the zero three thermocouple location.
The maximum root means square error for intratumoral and intravenous distributions was 2.10 degrees Celsius and 1.94 degrees Celsius respectively.
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Overview
This article presents a protocol for preparing tumor-tissue phantoms that replicate optical properties for plasmonic photothermal therapy. It bridges the gap between numerical modeling and experimental validation, offering a cost-effective alternative to in vivo studies.
Key Study Components
Area of Science
- Plasmonic photothermal therapy
- Tumor tissue phantoms
- Numerical modeling and validation
Background
- Development of tumor tissue phantoms for therapeutic evaluation.
- Importance of validating numerical simulations for accurate treatment.
- Reduction of animal testing through phantom-based evaluations.
- Future plans to enhance phantoms with realistic components like melanin and hemoglobin.
Purpose of Study
- To provide a protocol for evaluating plasmonic photothermal interactions.
- To specify therapeutic parameters for in vivo experiments.
- To improve treatment accuracy through simulation validation.
Methods Used
- Preparation of agarose phantoms.
- Thermocouple monitoring for temperature measurements.
- Evaluation of nanoparticle concentration and iteration settings.
- Validation of numerical models based on experimental data.
Main Results
- Successful replication of optical properties in tumor phantoms.
- Cost-effective method minimizing the need for animal testing.
- Validation of simulation results through experimental measurements.
- Identification of optimal therapeutic parameters for future studies.
Conclusions
- The protocol offers a reliable method for preliminary testing of plasmonic therapies.
- Phantom-based evaluations enhance the accuracy of treatment parameters.
- Future research aims to create more realistic tumor models.
