Citrate-capped gold nanoparticle electrophoretic heat production in response to a time-varying radiofrequency electric-field.

The journal of physical chemistry. C, Nanomaterials and interfaces · 2012 · Unclear · Low evidence

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UnclearLow evidencePaper 3137

Study snapshot

PublicationThe journal of physical chemistry. C, Nanomaterials and interfaces · 2012

Study typein_vitro

Reported directionUnclear

Evidence ratingLow

Abstract

The evaluation of heat production from gold nanoparticles (AuNPs) irradiated with radiofrequency (RF) energy has been problematic due to Joule heating of their background ionic buffer suspensions. Insights into the physical heating mechanism of nanomaterials under RF excitations must be obtained if they are to have applications in fields such as nanoparticle-targeted hyperthermia for cancer therapy. By developing a purification protocol which allows for highly-stable and concentrated solutions of citrate-capped AuNPs to be suspended in high-resistivity water, we show herein, for the first time, that heat production is only evident for AuNPs of diameters ≤ 10 nm, indicating a unique size-dependent heating behavior not previously observed. Heat production has also shown to be linearly dependent on both AuNP concentration and total surface area, and severely attenuated upon AuNP aggregation. These relationships have been further validated using permittivity analysis across a frequency range of 10 MHz to 3 GHz, as well as static conductivity measurements. Theoretical evaluations suggest that the heating mechanism can be modeled by the electrophoretic oscillation of charged AuNPs across finite length scales in response to a time-varying electric field. It is anticipated these results will assist future development of nanoparticle-assisted heat production by RF fields for applications such as targeted cancer hyperthermia.

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AI evidence extraction

Structured fields below were generated from the paper’s abstract and metadata to make the evidence easier to inspect. Automated extraction may be incomplete or incorrect; verify important details against the original paper.

Study typein_vitro

Effect directionunclear

PopulationNot supplied

Sample sizeNot supplied

ExposureRF

Evidence strengthLowConfidence: 74% · Peer reviewed: yes

Main findings

Using purified citrate-capped gold nanoparticles suspended in high-resistivity water, heat production under RF excitation was reported only for nanoparticles with diameters ≤10 nm. Heating was described as linearly dependent on nanoparticle concentration and total surface area, and strongly reduced when nanoparticles aggregated; permittivity analysis (10 MHz to 3 GHz) and static conductivity measurements were used to validate these relationships. The authors propose electrophoretic oscillation of charged nanoparticles in a time-varying electric field as a model for the heating mechanism.

Outcomes measured

Heat production (temperature increase) of citrate-capped gold nanoparticles in response to time-varying RF electric field
Size-dependent heating behavior (≤10 nm vs larger)
Dependence of heating on nanoparticle concentration and total surface area
Effect of aggregation on heating attenuation
Permittivity across 10 MHz–3 GHz
Static conductivity measurements

Limitations

Frequency of the RF exposure used for heating experiments is not specified in the abstract (only the permittivity analysis range is given).
No quantitative heating magnitudes, exposure levels, or dosimetry metrics (e.g., field strength, SAR) are provided in the abstract.
In vitro/physical mechanism study; no biological or health outcomes assessed.
Sample sizes and experimental replication details are not provided in the abstract.

View raw extracted JSON

{
  "study_type": "in_vitro",
  "exposure": {
    "band": "RF",
    "source": "other",
    "frequency_mhz": null,
    "sar_wkg": null,
    "duration": null
  },
  "population": null,
  "sample_size": null,
  "outcomes": [
    "Heat production (temperature increase) of citrate-capped gold nanoparticles in response to time-varying RF electric field",
    "Size-dependent heating behavior (≤10 nm vs larger)",
    "Dependence of heating on nanoparticle concentration and total surface area",
    "Effect of aggregation on heating attenuation",
    "Permittivity across 10 MHz–3 GHz",
    "Static conductivity measurements"
  ],
  "main_findings": "Using purified citrate-capped gold nanoparticles suspended in high-resistivity water, heat production under RF excitation was reported only for nanoparticles with diameters ≤10 nm. Heating was described as linearly dependent on nanoparticle concentration and total surface area, and strongly reduced when nanoparticles aggregated; permittivity analysis (10 MHz to 3 GHz) and static conductivity measurements were used to validate these relationships. The authors propose electrophoretic oscillation of charged nanoparticles in a time-varying electric field as a model for the heating mechanism.",
  "effect_direction": "unclear",
  "limitations": [
    "Frequency of the RF exposure used for heating experiments is not specified in the abstract (only the permittivity analysis range is given).",
    "No quantitative heating magnitudes, exposure levels, or dosimetry metrics (e.g., field strength, SAR) are provided in the abstract.",
    "In vitro/physical mechanism study; no biological or health outcomes assessed.",
    "Sample sizes and experimental replication details are not provided in the abstract."
  ],
  "evidence_strength": "low",
  "confidence": 0.74,
  "peer_reviewed_likely": "yes",
  "keywords": [
    "gold nanoparticles",
    "citrate-capped",
    "radiofrequency",
    "RF electric field",
    "Joule heating",
    "electrophoretic oscillation",
    "permittivity",
    "conductivity",
    "nanoparticle hyperthermia",
    "aggregation",
    "size-dependent heating"
  ],
  "suggested_hubs": []
}

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AI-extracted fields are generated from the abstract and metadata and may be incomplete or incorrect. This material is for informational purposes and is not medical advice.

Identifiers and source

DOI: 10.1021/jp309053z
PubMed: 23795228

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