Gold nanorods are the most commonly used nanoparticles in photothermal therapy for cancer treatment due to their high efficiency in converting light into heat. This study aimed to investigate the efficacy of gold nanorods of different sizes (large and small) in eliminating two types of cancer cell: melanoma and glioblastoma cells. After establishing the optimal concentration of nanoparticles and determining the appropriate time and power of laser irradiation, photothermal therapy was applied to melanoma and glioblastoma cells, resulting in the highly efficient elimination of both cell types. The efficiency of the PTT was evaluated using several methods, including biochemical analysis, fluorescence microscopy, and flow cytometry. The dehydrogenase activity, as well as calcein-propidium iodide and Annexin V staining, were employed to determine the cell viability and the type of cell death triggered by the PTT. The melanoma cells exhibited greater resistance to photothermal therapy, but this resistance was overcome by irradiating cells at physiological temperatures. Our findings revealed that the predominant cell-death pathway activated by the photothermal therapy mediated by gold nanorods was apoptosis. This is advantageous as the presence of apoptotic cells can stimulate antitumoral immunity in vivo. Considering the high efficacy of these gold nanorods in photothermal therapy, large nanoparticles could be useful for biofunctionalization purposes. Large nanorods offer a greater surface area for attaching biomolecules, thereby promoting high sensitivity and specificity in recognizing target cancer cells. Additionally, large nanoparticles could also be beneficial for theranostic applications, involving both therapy and diagnosis, due to their superior detection sensitivity.

Magnetic hyperthermia (MHT) is an oncological therapy that uses magnetic nanoparticles (MNPs) to generate localized heat under a low-frequency alternating magnetic field (AMF). Recently, trapezoidal pulsed alternating magnetic fields (TPAMFs) have proven their efficacy in enhancing the efficiency of heating in MHT as compared to the sinusoidal one. Our study aims to compare the TPAMF waveform’s killing effect against the sinusoidal waveform in B16F10 and CT2A cell lines to determine more efficient waveforms in causing cell death. For that purpose, we used MNPs and different AMF waveforms: trapezoidal (TP), almost-square (TS), triangular (TR), and sinusoidal signal (SN). MNPs at 1 and 4 mg/mL did not affect cell viability during treatment. The exposition of B16F10 and CT2A cells to only AMF showed nonsignificant mortality. Hence, the synergetic effect of the AMF and MNPs causes the observed cell death. Among the explored cases, the nonharmonic signals demonstrated better efficacy than the SN one as an MHT treatment. This study has revealed that the application of TP, TS, or TR waveforms is more efficient and has considerable capability to increase cancer cell death compared to the traditional sinusoidal treatment. Overall, we can conclude that the application of nonharmonic signals enhances MHT treatment efficiency against tumor cells.

Inducing magnetic hyperthermia (MHT) involves locally raising the temperature to 39–45 °C, which increases the susceptibility of tumor cells to therapeutic agents without damaging healthy tissues. Recent studies on trapezoidal pulsed alternating magnetic fields (TP-AMFs) have proven their considerable efficacy in increasing the temperature of magnetic nanoparticles (MNPs) compared to sinusoidal fields. Thermal therapies have been known to incorporate multiple combinations of therapeutic approaches to optimize the medical procedure for healing cancer patients such as chemotherapy and radiotherapy. The combination of MHT with chemotherapy aims to enhance the therapeutic effects against cancer due to the synergistic interaction in tumor cells. In this study, we aim to exploit the synergistic effects of combining MHT produced by TP-AMFs with a low concentration of 5-Fluorouracil (5-FU) to optimize the therapeutic outcomes in comparison to TP-AMFs MHT alone. Hence, we exposed a glioblastoma cell line (CT2A) incubated with iron oxide nanoparticles at 1 mg/mL to two cycles of MHT employing a trapezoidal-square waveform at 200 kHz and 2 mT for 30 min for each cycle, separated by a 45 min break, both as a single treatment and in combination with 0.1 μg/mL of 5-FU. Our findings demonstrated the efficacy of the synergistic effect between MHT treatment via TP-AMFs and the 5-FU, increasing the cell death to 58.9 ± 2%, compared to 31.4 ± 3% with MHT treatment alone. Cell death was primarily driven by the necrosis pathway (47.3 ± 2%) compared to apoptosis (11.6 ± 2). The addition of 5-FU enhanced the cytotoxic effect of MHT on CT2A cells, increasing the calreticulin (CRT) positive cells to 17 ± 1% compared to 10 ± 1% as produced by MHT treatment alone. Furthermore, this combination suggests that the employed treatment approach can promote immune system activation due to the exposure of CRT in the treated cells.

Magnetic hyperthermia (MHT) is an antitumor therapy that employs magnetic nanoparticles (MNPs) to generate localized heat using a low-frequency alternating magnetic field (AMF). Recently, trapezoidal pulsed alternating magnetic fields (TPAMF) have been shown to improve heating efficiency compared to sinusoidal fields, enhancing therapeutic effects. Since thermal therapies are often combined with treatments such as chemotherapy to improve clinical outcomes, this study sought to increase the effectiveness of MHT by using non-sinusoidal AMF waveforms and combining them with chemotherapy. The tumor cell lines B16F10 and CT2A, along with C57BL/6 mice, were used to evaluate the effects of different waveforms: trapezoidal (TP), quasi-square (TS), triangular (TR), and sinusoidal (SN). In in vitro testing, MNPs were incubated at non-cytotoxic concentrations (1 and 4 mg/mL). Exposure to SN and PAMF alone did not cause significant cell mortality, but non-sinusoidal waves, especially TS and TP, showed greater efficacy in inducing cell death. Furthermore, the synergistic effect of combining MHT generated with TPAMF and the chemotherapeutic agent 5-fluorouracil (5-FU) was evaluated. CT2A cells treated with MNP and exposed to two cycles of MHT using a TS waveform (200 kHz, 2 mT, 30 min per cycle with a 45- min interval), showed a 58.9% increase in cell death when combined with 5-FU, compared to 31.4% observed with MHT alone. Cell death was primarily due to necrosis, and improved immunogenicity was observed, with a 17% increase in calreticulin-positive (CRT) cells compared to 10% generated by MHT alone. Preliminary in vivo studies showed a slight reduction in tumor size with TPAMF compared to sinusoidal AMF. In silico simulations revealed a stable thermal distribution (~37C) at intensities below 5 mT, without significant thermal side effects, confirming the safety of TPAMF. At higher frequencies and amplitudes, eddy current effects with exponential temperature increases were detected, highlighting the need for careful parameter control. In conclusion, non-sinusoidal TP, TS, and TR waveforms were more effective than traditional sinusoidal waveforms at inducing cell death in MHT treatments. The combination of MHT with TPAMF and chemotherapy not only increased cytotoxic efficacy but also induced enhanced immunogenic cell death (ICD), which suggests that it is potentially capable of promoting the immune system activation. This combined approach could represent a promising strategy for improving cancer treatments. RESUMEN La hipertermia magnética (HTM) es una terapia oncológica que emplea nanopartículas magnéticas (MNP) para generar calor localizado mediante un campo magnético alterno (AMF) de baja frecuencia. Recientemente, se ha demostrado que los campos magnéticos alternos pulsados trapezoidales (TPAMF) mejoran la eficiencia del calentamiento respecto a los campos sinusoidales, potenciando los efectos terapéuticos. Dado que las terapias térmicas suelen combinarse con tratamientos como la quimioterapia para mejorar los resultados clínicos, en este estudio se buscó incrementar la efectividad de la HTM mediante el uso de formas de onda AMF no sinusoidales y su combinación con quimioterapia. Se utilizaron las líneas celulares tumorales B16F10 y CT2A, junto con ratones C57BL/6, para evaluar los efectos de diferentes formas de onda: trapezoidal (TP), casi cuadrada (TS), triangular (TR) y sinusoidal (SN). En las pruebas in vitro, las MNP se incubaron a concentraciones no citotóxicas (1 y 4 mg/mL). La exposición a SN y PAMF por sí solos no causó una mortalidad celular significativa, pero las ondas no sinusoidales, en especial TS y TP, mostraron una mayor eficacia en la inducción de muerte celular. Además, se evaluó el efecto sinérgico de combinar la HTM generada con TPAMF y el agente quimioterapéutico 5-fluorouracilo (5-FU). Las células CT2A, tratadas con MNP y expuestas a dos ciclos de HTM usando una onda TS (200 kHz, 2 mT, 30 min por ciclo con 45 min de intervalo), mostraron un aumento en la muerte celular del 58,9% al combinarse con 5-FU, en comparación con el 31,4% observado con HTM sola. La muerte celular fue principalmente por necrosis, y se observó una mejora en la inmunogenicidad del tratamiento, con un aumento del 17% en células positivas a calreticulina (CRT) frente al 10% generado por HTM sola. Los estudios preliminares in vivo mostraron una leve reducción del tamaño tumoral con TPAMF frente a ondas sinusoidales. Por su parte, las simulaciones in silico revelaron una distribución térmica estable (~37 °C) con intensidades menores a 5 mT, sin efectos térmicos secundarios significativos, lo que confirma la seguridad del uso de TPAMF. A mayores frecuencias y amplitudes, se detectaron efectos de corrientes parásitas con aumento exponencial de temperatura, destacando la necesidad de un control cuidadoso de los parámetros. En conclusión, las formas de onda no sinusoidales TP, TS y TR resultaron más eficaces que las sinusoidales tradicionales para inducir muerte celular en tratamientos con HTM. La combinación de HTM con TPAMF y quimioterapia no solo incrementó la eficacia citotóxica, sino que también indujo una muerte celular inmunogénica mejorada (ICD), potencialmente capaz de estimular el sistema inmunológico mediante la activación de células presentadoras de antígenos (APC). Este enfoque combinado podría representar una estrategia prometedora para mejorar los tratamientos contra el cáncer.