Photothermal nanoparticles absorb incident light and convert the absorbed energy into heat. Plasmonic nanoparticles are especially useful for this purpose because particle composition, size, and geometry can be engineered to produce strong absorption at selected wavelengths.
Gold nanorods and nanoshells, for example, can be designed with optical resonances in the near-infrared (NIR), supporting applications ranging from localized photothermal treatment and triggered delivery to nanowarming and rapid thermal cycling.
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Why Use Near-Infrared Light?
Near-infrared wavelengths are frequently used in biomedical photothermal research because tissue absorption and scattering can be lower in selected NIR wavelength ranges than in much of the visible spectrum. The useful penetration depth still depends on wavelength, tissue type, treatment geometry, and optical dose.
Plasmonic particle geometry can be tuned so that strong absorption overlaps with a selected excitation wavelength. This makes particle architecture an important design variable for photothermal systems.
Catalog nanoComposix materials are intended for Research Use Only. For translational programs, nanoComposix can support custom development, process scale-up, and quality-controlled manufacturing based on project requirements.
Choosing a Nanoparticle for Photothermal Applications
Particle composition and architecture determine the spectral response, absorption-to-scattering balance, environmental stability, and available surface chemistry.
| Particle Type | Photothermal Relevance | Key Considerations |
|---|---|---|
| Gold Nanorods | Strong, tunable absorption from the visible into the NIR | Resonance wavelength, aspect ratio, surface chemistry |
| Gold Nanoshells | Core-shell geometry enables strong NIR absorption and scattering | Core and shell dimensions, resonance, absorption-to-scattering balance |
| Silver Nanoplates | Highly tunable visible-to-NIR plasmonic response | Environmental stability, protective coatings, custom design |
| Custom Composite Particles | Can combine photothermal response with porous, magnetic, or other functions | Architecture, coatings, payload, formulation |
Optical Wavelength & Particle Architecture
Particle architecture determines where the plasmonic response occurs and how strongly the particle absorbs and scatters light. Gold nanorods and gold nanoshells provide particularly useful tunability into the NIR.
Silver nanoplates can also span a broad spectral range, but their optical properties are more sensitive to environmental chemistry. Formulation and protective coatings therefore become especially important when silver is used in demanding solution environments.
Absorption vs. Scattering
Optical extinction includes both absorption and scattering, but absorbed light is the component directly converted into heat. Photothermal particle design therefore needs to consider not only total extinction at the excitation wavelength, but also how much of that optical response comes from absorption.
Particle size and architecture can substantially alter the balance between absorption and scattering. For spherical and concentric core-shell systems, the Mie Theory Calculator can be used to compare calculated extinction, absorption, and scattering.
Surface Chemistry & Functionalization
Surface modification influences nanoparticle stability, compatibility with the surrounding formulation, and the ability to introduce molecular recognition or other functional properties.
| Surface Strategy | Potential Role |
|---|---|
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PEG & other polymers can modify colloidal stability and nonspecific interactions and provide functional handles for additional surface modification. |
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Silica shells can physically separate a plasmonic core from the surrounding environment while providing a versatile surface for further functionalization. |
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Antibodies, peptides, proteins & nucleic acids can introduce molecular recognition or other functional properties when attached using an appropriate conjugation strategy. |
Therapeutic & Delivery Applications
Photothermal Hyperthermia
Plasmonic nanoparticles have been widely investigated as localized heat sources for photothermal treatment. When particles absorb light at the excitation wavelength, the resulting temperature increase can affect nearby cells and tissue.
Particle localization, optical dose, absorption efficiency, and heat transport all influence the resulting thermal effect.
Light-Triggered Drug Delivery
Photothermal heating can also serve as a trigger within responsive delivery systems. Plasmonic particles can be incorporated into composite structures containing temperature-sensitive polymers, porous carriers, or other release mechanisms that respond to local heating.
Dermatology & Aesthetic Applications
Photothermal particles have been investigated for localized dermatologic and aesthetic treatments. Particle formulation, optical resonance, delivery into the target structure, and excitation wavelength all influence performance.
In a clinical study, NIR-absorbing silica-gold nanoshells were delivered into sebaceous glands and used for selective photothermolysis in acne treatment.
Theranostic & Multifunctional Systems
Photothermal functionality can be combined with imaging, molecular recognition, drug delivery, or other nanoparticle capabilities to create multifunctional research platforms.
Core-shell and composite architectures can be particularly useful when multiple functions need to be integrated into a single particle system.
Other Applications of Plasmonic Heating
Nanowarming & Cryopreservation
Plasmonic heating can provide rapid, spatially distributed warming during cryopreservation. Gold nanorods absorb incident light and convert it to heat within vitrified biological samples, providing an alternative to slower external warming.
In research conducted with the University of Minnesota, gold-nanorod-mediated warming improved the viability of cryopreserved zebrafish embryos and demonstrated the potential of nanoparticle-assisted nanowarming for challenging biological samples.
Plasmonic Thermocycling
Rapid plasmonic heating can also be used outside therapeutic applications. Nanoparticle-mediated heating has been integrated into PCR systems to reduce thermal cycling time and support compact nucleic-acid amplification platforms.
Combining rapid nanoparticle heating with optical detection can support portable and higher-throughput molecular testing concepts.
Need a nanoparticle engineered around a specific excitation wavelength?
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Selected Literature
- Cui, X. et al. “Photothermal Nanomaterials: A Powerful Light-to-Heat Converter.” Chemical Reviews, 123(11), 6891–6952 (2023).
- Hirsch, L. R. et al. “Nanoshell-mediated near-infrared thermal therapy of tumors under magnetic resonance guidance.” Proceedings of the National Academy of Sciences, 100(23), 13549–13554 (2003).
- Riley, R. S. & Day, E. S. “Gold nanoparticle-mediated photothermal therapy: applications and opportunities for multimodal cancer treatment.” WIREs Nanomedicine and Nanobiotechnology, 9(4), e1449 (2017).
- Liu, J. et al. “Gold Nanorods Coated with Mesoporous Silica Shell as Drug Delivery System for Remote Near Infrared Light-Activated Release and Potential Phototherapy.” Small, 11(19), 2323–2332 (2015).
- Paithankar, D. et al. “Ultrasonic delivery of silica-gold nanoshells for photothermolysis of sebaceous glands in humans: Nanotechnology from the bench to clinic.” Journal of Controlled Release, 206, 30–36 (2015).
- Khosla, K. et al. “Gold Nanorod Induced Warming of Embryos from the Cryogenic State Enhances Viability.” ACS Nano, 11(8), 7869–7878 (2017).
- Blumenfeld, N. R. et al. “Multiplexed reverse-transcriptase quantitative polymerase chain reaction using plasmonic nanoparticles for point-of-care COVID-19 diagnosis.” Nature Nanotechnology, 17, 984–992 (2022).