key: cord-0833044-62fvk4ma
authors: Kharat, Prashant B.; Somvanshi, Sandeep B.; Khirade, Pankaj P.; Jadhav, K. M.
title: Induction Heating Analysis of Surface-Functionalized Nanoscale CoFe(2)O(4) for Magnetic Fluid Hyperthermia toward Noninvasive Cancer Treatment
date: 2020-09-02
journal: ACS Omega
DOI: 10.1021/acsomega.0c03332
sha: d61ad9947bcfce76857380ed1f139a486e45e10e
doc_id: 833044
cord_uid: 62fvk4ma

[Image: see text] Oleic acid-coated cobalt ferrite nanoparticles were synthesized using the chemical co-precipitation route and characterized by standard techniques for structure, morphology, and magnetic properties analysis. The Rietveld refined X-ray diffraction (XRD) pattern of CoFe(2)O(4) nanoparticles indicated the formation of a cubic-spinel single-phase structure with the Fd3̅m space group. The average crystallite size (∼12 nm) confirmed the nanocrystalline appearance of the prepared CoFe(2)O(4) nanoparticles. Transmission electron microscopy (TEM) images revealed the spherical nature of both (CoFe(2)O(4)) and (OA-CoFe(2)O(4)) samples. The absorption bands in the Fourier transform infrared (FT-IR) spectrum at ∼3418, 3026, 1628, 1404, 1068, 845, 544, and 363 cm(–1) affirmed the spinel ferrite formation and OA attachment. The M–H curve recorded at room temperature showed the superparamagnetic nature of the CoFe(2)O(4) nanoparticles with moderate saturation magnetization (∼78 emu/gm). The blocking temperature of the prepared CoFe(2)O(4) nanoparticles obtained from the field-cooled and zero-field-cooled (FC–ZFC) curve was estimated to be 144 K. Further, the characterized surface-modified CoFe(2)O(4) was then added in ethylene glycol/water with various concentrations and characterized by the induction heating technique for the evaluation of their self-heating characteristics. A series of temperature versus time measurements were made by varying the ethylene glycol/water proportion for better understanding of the self-heating characteristics of the prepared CoFe(2)O(4) nanoparticles. All of the findings display the applicability of the surface-modified CoFe(2)O(4) nanoparticles in magnetic fluid hyperthermia toward noninvasive cancer treatment and other bio-applications.

Magnetic nanomaterials with appropriate physicochemical properties, functionalized surface, and improved biocompatibility have been broadly examined for different restorative, indicative, and remedial applications, for example, specific drug delivery, fluid hyperthermia, as a contrast enhancer in magnetic resonance or reverberation imaging (MRI), cell detachment, tissue fixing, biosensors, and so forth. 1−6 The physicochemical properties, colloidal strength, and biocompatibility of these magnetic nanomaterials can be vitally constrained by precise synthesis conditions and functionalization of the surface. Magnetic platforms with nanometric size (of the order of a few nanometers) and thin size distribution with upgraded magnetic properties comprise the prime necessity for biomedical application purposes. Likewise, magnetic nanoparticles should also have consolidated high susceptibility for the best magnetic enhancement and quicker loss of magnetization after disposal of the outer guest magnetic field. Magnetic fluid hyperthermia, a modular strategy for disease treatment with the desired temperature, in the range of 41−45°C, and a treatment period of least 20 min, has been paid great attention to because of its lower clinical symptoms and probability to obliterate particular territory of harmful malignancy tumor. 7−9 This procedure includes the consolidation of superparamagnetic or ferromagnetic particles into the dangerous tumor cell and then illumination with a substituting magnetic field. 10 In previous decades, much research of magnetic nanomaterials for biomedical field (specifically hyperthermia) has been centered on superparamagnetic iron oxide materials, for example, Fe 3 O 4 and γ-Fe 2 O 3 , which show smaller saturation magnetization values. 11−13 In contrast, some transition metals, for example, Ni, Co, and so on, acquire large saturation magnetization values, similarly moderate anisotropy, steady K eff , and larger losses. Recently, spinel-structured ferrite nanomaterials, a type of general magnetic nanomaterials, have attracted the great attention of researchers and scientists. 14 is important from the biomedical application perspective because of its great saturation magnetization, high permeability, and no favored direction of magnetization. 25 In addition, it displays high anisotropy of the order 190−280 kJ/m 3 in correlation with alternate ferrites. Hence, the magnetic moment of CoFe 2 O 4 relaxes with a much slower rate than other iron oxide nanoparticles of same size. This suggests that CoFe 2 O 4 nanoparticles with a nanometric size range can be utilized as an alternative of iron oxide nanoparticles in hyperthermia applications. Utilization of CoFe 2 O 4 nanoparticles in the biomedical field is very monotonous due to a few issues, for example, aggregation of nanoparticles in solution and the toxicity of the material. To overcome these issues, coating CoFe 2 O 4 nanoparticles with suitable surfactants, for example, oleic acid, polyethylene glycol, and so forth, produces a protecting layer and lessens the direct and immediate exposure of the CoFe 2 O 4 nanoparticles surface to the organic climate. Oleic acid (OA) is one of the promising coating agents having complementary anticancerous and anti-inflammatory behavior. 26 Oleic acid coating helps us to stabilize the nanoparticles in fluidic media and enhances the dispersion stability of the nanoparticles with less agglomeration. Also, oleic acid coating increases the biocompatibility of the nanoparticles, which is one of the main concerns of the biomedical applications of nanoparticles. 27 In recent decades, surface-functionalized spinel ferrites, especially CoFe 2 O 4 nanoparticles prepared by utilizing wet chemical techniques were explored by the academic and scientific network for biomedical applications, for example, directed drug loading, magnetic hyperthermia, and magnetic resonance imaging. 28,29 These analyses were fundamentally centered on the inductive heating properties of CoFe 2 O 4 nanoparticles synthesized by the hydrothermal method and the sol−gel autoburning technique. However, very few reports are available on water-dispersible CoFe 2 O 4 nanoparticles prepared by the chemical co-precipitation method and functionalized by oleic acid. The CoFe 2 O 4 nanoparticles are effectively dispersed and stable in combination with water and ethylene glycol in contrast to other fluidic mediums, which results in a superior self-warming at lower attractive field. In correlation with other synthesis routes, the chemical co-precipitation strategy showed numerous advantages, for example, better homogeneity, small particle size, moderately low reaction temperature, thin size distribution, low cost, and so on. 30, 31 Thus, herein, we report the synthesis, characterization, and induction heating evaluation of surface-modified CoFe 2 O 4 nanoparticles co-dispersed in water/ethylene glycol. Oleic acid-coated cobalt ferrite nanoparticles were synthesized using the chemical co-precipitation route and characterized by standard techniques for structure, morphology, and magnetic properties analysis. Further, the characterized surface-modified CoFe 2 O 4 was then added in ethylene glycol/water with various concentrations and characterized by the induction heating technique for evaluation of their self-heating characteristics. A series of temperature versus time measurements were done by varying the ethylene glycol/water proportion for better understanding of the self-heating characteristics of the prepared CoFe 2 O 4 nanoparticles.

The pristine and surface-modified CoFe 2 O 4 samples were coded as PR-CF and SM-CF, respectively. The recorded X-ray diffraction (XRD) patterns of PR-CF and SM-CF are shown in Figure 1 , which reveals that both the PR-CF and SM-CF samples exhibit good crystalline nature that confirms the formation of a pure-phase nanoparticle without any impurity phase. Rietveld refinement of both the PR-CF and SM-CF samples was done by FullProf Suite software. It is confirmed from Figure 1 that functionalization of the oleic acid on the surface of the CoFe 2 O 4 nanoparticles did not modify the crystal structure of the PR-CF. A small noise was recorded in the XRD pattern of SM-CF due to the amorphous nature of oleic acid Table 1 shows the values of structural parameters of PR-CF and SM-CF nanoparticles deduced from XRD data.

The morphology of PR-CF and SM-CF analyzed by transmission electron microscopy (TEM), as shown in Figure  1 , was found to be spherical in nature for both samples. The slight agglomeration of SM-CF is also attributed to the magnetic interaction among the nanoparticles, which results in the lowering of surface energy and depends on the communal performance of NPs and intermolecular force offered among them. The particle size (t) values determined from TEM data are found to be 9. Thermogravimetric analysis (TGA) of PR-CF and SM-CF was studied to examine the phase development temperature of the spinel cubic structure. The TGA plot of PR-CF and SM-CF is shown in Figure 2 . The curve shows the elimination of nitrates trailed by the development of the spinel ferrite phase with respect to temperature. The TGA curve demonstrates total weight losses of 21.18 and 24.87% for the PR-CF and SM-CF samples, respectively, as seen in Figure 2 . Also, it is noted from the TGA curve that there is no notable weight loss beyond 450°C

, which is accredited to spinel ferrite phase development. The decomposition of the SM-CF sample started at 170°C and ended at 440°C with a total weight loss of 24.87%. This weight loss of 24.87% emerged from the disintegration of oleic acid, which is presented on the core of the SM-CF sample. This validates the total % of oleic acid as 24.87% on the SM-CF core.

The Fourier transform infrared (FT-IR) spectra of PR-CF and SM-CF are shown in Figure 2 . The emergence of bands at 544 and 363 cm −1 corresponds to the stretching vibrations of Fe 3+ − O 2 and Co, which appeared in both the PR-CF and SM-CF samples. 32, 33 The peaks at about 3418 cm −1 are assigned to O− H vibrations. The peaks at 544 and 363 cm −1 are assigned to Fe at the tetrahedral location, whereas the peaks at 1068 and 845 cm −1 are due to the stretching vibration mode related to the C− O band. The peaks at 1628 and 1404 cm −1 are due to the asymmetric and symmetric stretching linked with the COO− band, respectively. The carboxylic acid groups are then present in a COO− conformation. The peak at 3026 cm −1 is due to the asymmetric stretching linked with the CH 2 band. This observation indicates the existence of carboxylic molecules on the nanoparticle surface, which also confirms the functionalization of the oleic acid layer over the cobalt ferrite nanoparticles. The obtained peaks are well matched with earlier reports. 34 It is observed from Figures 3 and 4 that all of the curves show a gradual increase in temperature with respect to time. The time required for the temperature rise decreased with the increase of nanoparticle concentration for both the PR-CF and SM-CF samples. The hyperthermia temperature was achieved at 65 s by the PR-CF sample with 1 mg/mL concentration, whereas for 5 mg/mL concentration, it was 55 s. Similarly, the hyperthermia temperature range was achieved at 70 s by the SM-CF sample with 1 mg/mL concentration, whereas for 5 mg/mL concentration, it was 60 s. It is also observed from the curves that the increase in temperature was slightly decreased after the oleic acid coating over the CoFe 2 O 4 nanoparticles. This slight decrease can be attributed to the decrease of saturation magnetization, which directly affects the heating ability of the nanoparticles.

Specific absorption rate (SAR) is one of the important parameters that plays a significant role in the application of MNPs in hyperthermia therapy. The following equation was used to calculate the SAR 36 = Δ Δ T t m specific absorption rate (SAR) C 1 Fe Figure 5 shows the SAR plots for different nanoparticle concentrations as well as varying ethylene glycol/water proportion for PR-CF and SM-CF samples, respectively. It is observed from Figure 5 that the SAR value decreases with an increase in the nanoparticle concentration, whereas it increases with an increase in water concentration. The highest SAR values of the order of 248 W/g was observed for the PR-CF sample with 1 mg/mL concentration. This SAR value was decreased to 216 W/g for the SM-CF sample due to oleic acid coating. This shows that the SM-CF sample with 1 mg/mL concentration is sufficient to produce the required heat for hyperthermia treatment.

Oleic acid-coated CoFe 2 O 4 nanoparticles were successfully synthesized using the chemical co-precipitation route. Table 2 . 

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