Carborane-Containing Iron Oxide@Gold Nanoparticles for Potential Application in Neutron Capture Therapy

Abstract

Cancer remains one of the most pressing global health challenges, driving the need for innovative treatment strategies. Boron neutron capture therapy (BNCT) offers a highly selective approach to destroying cancer cells while sparing healthy tissues. To improve boron delivery, Fe₃O₄@Au nanoparticles were developed and functionalized with a boron-containing carborane compound. Fe₃O₄ nanoparticles were synthesized and covered by gold, followed by (3-Aminopropyl)triethoxysilane (APTES) modification to introduce amino groups for carborane immobilization. Comprehensive characterization using SEM, DLS, FTIR, EDX, Brunauer-Emmett-Teller (BET), and XRD confirmed successful functionalization at each stage. TEM confirmed the final structure and elemental composition of the nanoparticles. BET analysis revealed a surface area of 94.69 m²/g and a pore volume of 0.51 cm³/g after carborane loading. Initial release studies in PBS demonstrated the removal of only loosely bound carborane within 48 h, with FTIR confirming stable retention of the compound on the nanoparticle surface. The modified nanoparticles achieved a stable zeta potential of -20 mV. The particles showed low toxicity within a range of concentrations (0-300 μg Fe/mL) and were efficiently accumulated by U251MG cells. These results demonstrate the potential of the obtained nanoparticles to carry boron and gold for their possible application as a theranostic agent.

Keywords: carborane; drug delivery; iron oxide; nanoparticles; neutron capture therapy.

Figure 1

Calibration curve of carborane concentration in PBS solution.

Figure 2

Scheme of Fe₃O₄ modification.

Figure 3

FTIR spectra of Fe₃O₄ at different stages of modifications (a); FTIR spectrum dissociation of potassium salt of carborane containing β-aryl aliphatic acid (b).

Figure 4

Zeta potential of nanoparticles at different stages of modification.

Figure 5

The stability of carborane on NPs in a phosphate-buffered saline (PBS) solution (a) and FTIR analysis before and after desorption (b); UV-vis spectra of the solution during carborane release (c).

Figure 6

X-ray diffraction patterns of the obtained samples: (1) Fe₃O₄, (2) Fe₃O₄@Au, (3) Fe₃O₄@Au–APTES, and (4) Fe₃O₄@Au–APTES–carborane.

Figure 7

SEM images and size distribution histograms of (a) Fe₃O₄, (b) Fe₃O₄@Au, (c) Fe₃O₄@Au–APTES, and (d) Fe₃O₄@Au–APTES–carborane nanoparticles.

Figure 8

Material and structural characterization of Fe₃O₄@Au–APTES–carborane particles. (a) Low-resolution transmission electron microscopy (TEM) image of Fe₃O₄@Au–APTES–carborane particles. (b,c) High-resolution TEM images of Fe₃O₄@Au–APTES–carborane particles showing their morphology and surface structure. (d) Selected-area electron diffraction (SAED) pattern obtained from the region shown in (a), where yellow corresponds to Au and white corresponds to Fe₃O₄ lattice orientation.

Figure 9

Proliferation of U251MG cells after incubation with nanoparticles.