Hyperthermic effects of dissipative structures of magnetic nanoparticles in large alternating magnetic fields.

Abstract

Targeted hyperthermia treatment using magnetic nanoparticles is a promising cancer therapy. However, the mechanisms of heat dissipation in the large alternating magnetic field used during such treatment have not been clarified. In this study, we numerically compared the magnetic loss in rotatable nanoparticles in aqueous media with that of non-rotatable nanoparticles anchored to localised structures. In the former, the relaxation loss in superparamagnetic nanoparticles has a secondary maximum because of slow rotation of the magnetic easy axis of each nanoparticle in the large field in addition to the known primary maximum caused by rapid Néel relaxation. Irradiation of rotatable ferromagnetic nanoparticles with a high-frequency axial field generates structures oriented in a longitudinal or planar direction irrespective of the free energy. Consequently, these dissipative structures significantly affect the conditions for maximum hysteresis loss. These findings shed new light on the design of targeted magnetic hyperthermia treatments.

AI evidence extraction

Main findings

Numerical comparisons suggested that rotatable superparamagnetic nanoparticles can show a secondary maximum in relaxation loss in large alternating magnetic fields due to slow rotation of the magnetic easy axis, in addition to a primary maximum attributed to Néel relaxation. For rotatable ferromagnetic nanoparticles, irradiation with a high-frequency axial field generated longitudinal or planar oriented structures, which significantly affected conditions for maximum hysteresis loss.

Outcomes measured

• magnetic loss (relaxation loss, hysteresis loss)
• heat dissipation mechanisms in magnetic nanoparticles
• formation of dissipative structures under high-frequency axial field

Limitations

• Study described as numerical comparison/modeling; no experimental or clinical outcomes reported in the abstract.
• Exposure parameters (field strength, frequency) are not specified in the abstract.
• No biological endpoints or safety/health outcomes are reported; focus is on physical mechanisms relevant to hyperthermia design.

Suggested hubs

• engineering (0.6)
  Mechanistic/numerical study of magnetic nanoparticle heating in alternating magnetic fields for hyperthermia.
• medical-applications (0.55)
  Discusses design implications for targeted magnetic hyperthermia cancer treatment.

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    "study_type": "other",
    "exposure": {
        "band": null,
        "source": "alternating magnetic field (magnetic hyperthermia context)",
        "frequency_mhz": null,
        "sar_wkg": null,
        "duration": null
    },
    "population": null,
    "sample_size": null,
    "outcomes": [
        "magnetic loss (relaxation loss, hysteresis loss)",
        "heat dissipation mechanisms in magnetic nanoparticles",
        "formation of dissipative structures under high-frequency axial field"
    ],
    "main_findings": "Numerical comparisons suggested that rotatable superparamagnetic nanoparticles can show a secondary maximum in relaxation loss in large alternating magnetic fields due to slow rotation of the magnetic easy axis, in addition to a primary maximum attributed to Néel relaxation. For rotatable ferromagnetic nanoparticles, irradiation with a high-frequency axial field generated longitudinal or planar oriented structures, which significantly affected conditions for maximum hysteresis loss.",
    "effect_direction": "unclear",
    "limitations": [
        "Study described as numerical comparison/modeling; no experimental or clinical outcomes reported in the abstract.",
        "Exposure parameters (field strength, frequency) are not specified in the abstract.",
        "No biological endpoints or safety/health outcomes are reported; focus is on physical mechanisms relevant to hyperthermia design."
    ],
    "evidence_strength": "insufficient",
    "confidence": 0.7399999999999999911182158029987476766109466552734375,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "magnetic nanoparticles",
        "magnetic hyperthermia",
        "alternating magnetic field",
        "Néel relaxation",
        "hysteresis loss",
        "dissipative structures",
        "ferromagnetic nanoparticles",
        "superparamagnetic nanoparticles",
        "numerical study"
    ],
    "suggested_hubs": [
        {
            "slug": "engineering",
            "weight": 0.59999999999999997779553950749686919152736663818359375,
            "reason": "Mechanistic/numerical study of magnetic nanoparticle heating in alternating magnetic fields for hyperthermia."
        },
        {
            "slug": "medical-applications",
            "weight": 0.5500000000000000444089209850062616169452667236328125,
            "reason": "Discusses design implications for targeted magnetic hyperthermia cancer treatment."
        }
    ]
}

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