Fe3O4/ZIF-8-90 Nanocomposite as a Strategy for Oncological Treatment

Cancer remains a major global health challenge, with conventional chemotherapy limited by poor selectivity and significant side effects. This study reports the design of a magnetic nanocarrier, combining superparamagnetic iron oxide nanoparticles (Fe₃O₄) with the metal–organic framework ZIF-8-90, forming a multifunctional Fe₃O₄/ZIF-8-90 nanosystem. The nanocarrier exhibited a uniform particle size (~97 nm) and efficiently adsorbed 13% of 5-fluorouracil (5-FU).

The composite demonstrated high biocompatibility toward healthy cells (85% viability at ≤100 µg/mL) and selective cytotoxicity against breast (MDA-MB-231) and lung (H292) tumor cells. Under magnetic fields, it achieved a temperature rise of 5.2 °C in 10 min, confirming its potential for magnetic hyperthermia therapy. Additionally, MRI relaxometric studies revealed a strong T₂ contrast effect (r₂ = 180.15 mM⁻¹ s⁻¹). Altogether, Fe₃O₄/ZIF-8-90 emerges as a promising theranostic nanoplatform, uniting targeted treatment and diagnostic imaging for advanced oncological applications.

The original article

Fe3O4/ZIF-8-90 Nanocomposite as a Strategy for Oncological Treatment

Julia Fernanda da Costa Araujo, Giovanna Nogueira da Silva Avelino Oliveira Rocha, José Yago Rodrigues Silva*, João Victor Ribeiro Rocha, Andris Figueiroa Bakuzis, and Severino Alves Junior*

ACS Omega 2025, 10, 27, 29463–29475

https://doi.org/10.1021/acsomega.5c02819

licensed under CC-BY 4.0

Selected sections from the article follow. Formats and hyperlinks were adapted from the original.

Cancer remains one of the leading causes of death worldwide, posing a significant challenge to public health. According to the Global Cancer Observatory (Globocan), it is estimated that one in five individuals will develop cancer during their lifetime. (1,2) Despite advancements in conventional treatments such as surgery, radiotherapy, and chemotherapy, these methods often lack specificity, causing collateral damage to healthy tissues and severe adverse effects. (3) In this context, the search for more effective and less invasive therapeutic approaches has become a priority in the fight against the disease.

In this context, nanotechnology-based systems have emerged as powerful tools for targeted drug delivery, with particular emphasis on metal–organic frameworks (MOFs). MOFs, due to their high porosity, large surface area, and versatile chemistry, have shown exceptional promise in biomedical applications. (4−7) Among them, Zeolitic Imidazolate Framework-8 (ZIF-8), composed of Zn²⁺ ions and 2-methylimidazole linkers, stands out for its chemical and thermal stability, biocompatibility, high surface area (∼1600 m²/g), and tunable pore size (∼11.6 Å), enabling the encapsulation of various therapeutic agents and controlled release in mildly acidic tumor microenvironments. (8−10)

Studies corroborate the superior performance of ZIF-8-90 compared to ZIF-8. For example, Ma et al. demonstrated that fibers coated with ZIF-8-90 presented high adsorption efficiency for both hydrophilic and hydrophobic targets, an effect attributed to the synergy between the methyl and aldehyde groups on the surface of the material, combined with its high porosity. (11) Additionally, ZIF-8-90 exhibits greater colloidal stability in aqueous media and better compatibility with water-soluble drugs. In the Yen et al. study, ZIF-90 and its postfunctionalized derivatives showed excellent dispersibility in aqueous solution and significantly lower cytotoxicity when compared to more hydrophobic systems. (13) Another relevant aspect is the presence of the aldehyde group in its ligand, which acts as an active site for postsynthetic modifications, allowing the conjugation of targeting molecules and expanding its potential for selective delivery into tumor tissues. (14,15) Thus, ZIF-8-90 represents an evolution over ZIF-8, especially for biological applications.

To introduce additional functionalities and therapeutic synergies, superparamagnetic iron oxide nanoparticles (SPIONs), typically Fe₃O₄, have been integrated into metal–organic frameworks (MOFs). (16−19) SPIONs exhibit excellent biocompatibility, (20−22) are FDA (Food and Drug Administration) approved for clinical use, and perform multiple functions: as contrast agents in magnetic resonance imaging (MRI), (23,24) heat mediators in magnetic hyperthermia, (16,25−28) magnetic drug delivery vehicles, (29) and also for the treatment of iron deficiency anemia. (30) Critically, findings have revealed that SPIONs can modulate the tumor immune microenvironment. Zanganeh et al. demonstrated that SPIONs can polarize tumor-associated macrophages (TAMs) toward the pro-inflammatory M1 phenotype, thus activating cytotoxic immune responses and inhibiting tumor growth and metastasis. (31) Recently, Liu et al. developed an iron-based nanocomposite derived from Polyporus umbellatus polysaccharides. This material promoted M1 polarization of TAMs and significantly enhanced antitumor efficacy in a breast cancer model, further confirming the immunomodulatory potential of iron-based systems. (32) These results highlight the immunomodulatory capacity of SPIONs, positioning them as active agents in cancer therapy.

Beyond their immunomodulatory role, thermal nanomedicine applications of SPIONs also have important oncology applications. When quasi-static superparamagnetic iron oxide NPs are excited by an AC magnetic field, dynamic hysteresis can appear, resulting in local heat release. (33) This property has led to the clinical approval of magnetic hyperthermia combined with radiotherapy for brain cancer therapy. (33,34) Heat can also trigger an immune response, (35) as demonstrated by recent studies, (36−38) and enhancement effects are expected due to the biodegradation of the NPs, since they release metallic ions that might be relevant for cancer immunotherapy. (37,39)

In this sense, the integration of Fe₃O₄ nanoparticles into ZIF-8-90 matrices creates a hybrid nanocomposite that takes advantage of the synergistic benefits of both components: the structural versatility and high load capacity of ZIF-8-90 and the magnetic responsiveness, imaging capability, and immunomodulatory potential of SPIONs. Compared to Fe₃O₄/ZIF-8 systems, Fe₃O₄/ZIF-8-90 offers improved drug–carrier interactions, higher dispersion stability in biological environments, and therapeutic performance.

Therefore, this study aims to synthesize and characterize the Fe₃O₄/ZIF-8-90 nanocomposite, as well as its application in the controlled loading and release of the anticancer drug 5-FU. Additionally, the system’s functionalities for magnetic hyperthermia and its potential as a contrast agent in magnetic resonance imaging will be explored, consolidating an integrated and efficient approach to cancer treatment.

2. Results and Discussion

2.1. Characterizations

The X-ray diffraction (XRD) patterns presented in Figure 1a show the characteristic peaks of the synthesized ZIFs, in addition to the calculated pattern for ZIF-8 (COD 4118891, Crystallography Open Database). The diffractograms confirm the isoreticularity between the ZIF-8 and ZIF-8-90 structures, both based on the coordination of zinc with imidazole-class ligands. (12,45) This behavior was expected since, as reported in the literature, the structure of the hybrid ZIF-8-90 exhibits structural variations of less than 3% compared to its ZIF-8 and ZIF-90 counterparts. (9)

ACS Omega 2025, 10, 27, 29463–29475: Figure 1. (a) and (b) XRD spectra of prepared ZIF-8, ZIF-8-90, Fe3O4 and Fe3O4/ZIF-8-90.

In the case of SPIONs (Figure 1b), the observed diffraction peaks show excellent agreement with the calculated pattern for the magnetite phase (COD 1010369). These peaks are by the works of Siregar et al. and Dutta et al., who observed similar diffractograms with 2θ values around 30.12°, 35.48, 43.12, 53.5, 57.04, and 62.64 corresponding to (220), (311), (400), (422), (511), and (440) planes, respectively. (22,46) Additionally, in the diffractograms of the Fe₃O₄/ZIF-8-90 nanosystem, it is possible to identify the (311) and (400) planes of the SPIONs. These results confirm the successful incorporation of SPIONs into the ZIF-8-90 matrix, consolidating the presence of iron oxide in the hybrid structure.

The refinement of the X-ray diffraction patterns was performed using the GSAS-II software. The collected data calculated crystallographic parameters, and the details of the XRD data refinements are presented in Table S1, and the graphs generated after refinement are in Figure S1.

The phase fraction ratio (Fe₃O₄: 41.165%; ZIF-8-90:58.835%) is surprising, as a higher percentage for the hybrid ZIF was expected due to the low intensity of characteristic peaks corresponding to the iron oxide planes in the final material. The SPIONs were identified as an FCC system with space group Fd-3m, typical of magnetite, indicating high structural symmetry, (47,48) and the materials demonstrated its system as BCC and space group I-43m. (49) The unit cell volume, which is 4950.42 ų, is significantly more extensive than that of SPIONs due to large internal cavities in the metal–organic material.

To compare the crystallite size obtained through GSAS-II, the Williamson-Hall and Scherrer methods were also employed. (50−52) The crystallite size (Table S1) increases with the incorporation of NPs and the formation of the hybrid ZIF (ZIF-8:68.2 nm < ZIF-8-90:70.02 nm < Fe₃O₄/ZIF-8-90:106.2 nm), which aligns with expectations and closely matches the values obtained from crystal counting in the SEM images.

In the FTIR spectrum (Figure 2a), characteristic bands were observed, confirming the formation of the metal–organic frameworks ZIF-8 and ZIF-8-90. The band at 420 cm^–1 is associated with the stretching vibration of the Zn–N bond, confirming the coordination between the imidazolate ligand and the zinc metal ion. (42,53) In the ZIF-8-90 hybrid, notable bands at 1681 and 790 cm^–1 were observed, corresponding to the C═O stretching and C–H bending vibrations, respectively, both attributed to the aldehyde group of the ICA ligand, reinforcing the formation of the ZIF-90 structure. (54−57)

ACS Omega 2025, 10, 27, 29463–29475: Figure 2. (a) and (b) FT-IR spectra of ZIF-8, ZIF-8-90, Fe3O4 and Fe3O4/ZIF-8-90.

In the Fe₃O₄ spectrum (Figure 2b), a band at 550 cm^–1 was identified, attributed to the Fe–O stretching vibrations. This finding aligns with the studies by Beigi and Babamoradi and Kutluay et al., characterizing the spinel structure of magnetite and confirming the presence of iron oxide in the nanocomposite composition. (21,58−60)

The morphologies and structures of Fe₃O₄ nanoparticles and the Fe₃O₄/ZIF-8-90 nanocomposite are presented in the SEM micrographs in Figure 3. The Fe₃O₄ nanoparticles appeared aggregated, with tiny crystals approximately 11 nm in size (Figure 3a). The Fe₃O₄/ZIF-8-90 nanocomposite retained its morphology compared to pure ZIF-8-90 (Figure S2b), exhibiting a well-defined orthorhombic structure with smooth and homogeneous surfaces and an average diameter of 97 nm (Figure 3b), a value considered ideal for biological applications in tumor tissues according to Wang et al. (61) A slight coexistence of polyhedral particles of varying sizes was observed, likely resulting from heterogeneous crystal nucleations on the surfaces of preexisting crystals, a phenomenon known as Ostwald ripening. (62)

ACS Omega 2025, 10, 27, 29463–29475: Figure 3. Micrographs of (a) Fe3O4 and (b) Fe3O4/ZIF-8-90 obtained by scanning electron microscopy (SEM). Images (c) and (d) correspond to transmission electron microscopy (TEM) of the Fe3O4ZIF-8-90 system, evidencing the presence of Fe3O4 nanoparticles inside and on the surface of the ZIF-8-90 crystals.

Transmission electron microscopy (TEM) analysis in Figure 3c revealed that the SPIONs within the sample tended to organize into small clusters, both inside and on the surface of the ZIF-8-90 crystals. This behavior can be attributed to the small size of the Fe₃O₄ nanoparticles and the specific interactions between functional groups on the PVP functionalized SPIONs and the ligands of ZIF-8-90, as observed by Lu et al. (63) In some crystals, SPIONs were centralized (Figure 3d), potentially indicating preferential heterogeneous nucleation during the initial formation of ZIF-8-90 crystals. This result is consistent with studies by Abdelmigeed et al., who reported SPION localization at the core of ZIF-8 crystals, and Chen et al., who observed similar behavior in ZIF-90 crystals, highlighting the impact of these hybrid structures on thermal stability and magnetic properties. (64,65) TEM analysis of SPIONs are provided in Figure S3.

3. Conclusions

In this study, a multifunctional superparamagnetic nanocarrier, Fe₃O₄/ZIF-8-90, was developed based on a hybrid ZIF. The synthesis was optimized for reproducibility, resulting in a structurally stable material with a well-defined crystallographic pattern and an average particle size of 97.09 nm. The composite demonstrated a 5-FU loading capacity of 0.21 mg per milligram of material. In magnetic hyperthermia tests, Fe₃O₄/ZIF-8-90 exhibited a temperature elevation of 5.18 °C under alternating magnetic field conditions of 6.37 kAm^–1 and a frequency of 323 kHz, remaining within the biological safety limits. Relaxometry tests indicated an increase in relaxivity (r₂ = 180.15 mM^–1 s^–1), especially for T₂-weighted images, reinforcing its potential as a contrast agent. Additionally, cell viability tests demonstrated the composite’s selectivity for MDA-MB-231 and H292 tumor cells, with a cytotoxic effect exclusive to these cells, while preserving the viability of healthy Vero cells.

Comparing the results to their equivalent Fe₃O₄/ZIF-8, Fe₃O₄/ZIF-8-90 exhibited superior performance in key aspects relevant to theranostic applications. A higher transverse relaxation rate suggests a more efficient material to act as a negative contrast agent, possibly due to the higher integration and dispersion of Fe₃O₄ nanocrystals within the ZIF-8-90 matrix. Additionally, although the thermal response observed in hyperthermia was moderate, the experiment was conducted under field conditions significantly below the clinical safety threshold, implying that heating efficiency may increase under more intense conditions. Importantly, using the carboxyl-functionalized ligand (ZIF-8-90) provides greater chemical versatility, facilitating future conjugation with targeting moieties and paving the way for developing more selective and personalized nanoplatforms. Therefore, Fe₃O₄/ZIF-8-90 emerges as a promising and adaptable theranostic candidate, integrating drug delivery, magnetic hyperthermia, and MRI contrast capabilities into a single nanosystem.

4. Materials and Methods

4.2. Instruments

Powder X-ray Diffractometry (XRD) analysis was performed using a Bruker eco D8 Advance device under a radiation source with a copper anode (CuKα (1.537 Å)). The morphology of the nanocomposite was characterized by a Tescan MIRA 3 scanning electron microscope (SEM) and a Tecnai G2 Spirit TWIN transmission electron microscope (TEM). Elemental mapping by the Energy Dispersive Detector (EDS) was performed by an Oxford Instruments Ultim Max 40 detector coupled to the SEM. For thermal analysis, a Shimadzu thermogravimetric analyzer, model TGA 60/60H, was used under a synthetic air atmosphere. Fourier transform infrared (FTIR) was performed using Shimadzu IRSpirit equipment with the ATR (attenuated total reflectance) accessory. The UV–vis absorption spectra were obtained on a Shimadzu UV-2600 spectrophotometer in the wavelength range of 200–800 nm. For magnetic characterization, a Vibrating Sample Magnetometer (VSM) ADE EV9 ADE-MAGNETICS model EV-9 operating in a magnetic field intensity range of −20 000 Oe to 20 000 Oe was used.