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3Laser synthesis of boron nanoparticles for BNCT
K.O. Aiyyzhy1*, E.V. Barmina1
1- Prokhorov General Physics Institute of the Russian Academy of Sciences, Vavilova str. 38, 119991 Moscow,
Russia
* aiyyzhy@phystech. edu
Boron neutron capture therapy (BNCT) is one of the most appealing radiotherapy modalities, whose efficiency can be further improved by the employment of boron nanoparticles (NPs) [1,2]. But the fabrication of biologically friendly, water-dispersible NPs with high boron content and favorable physicochemical characteristics still presents a great challenge. In this work, we study the synthesis of elemental boron NPs using pulsed laser fragmentation in the liquid of commercial boron powders (grade A, grade B and boron enriched with the 10B isotope). A solid-state Nd:YAG laser with a wavelength of 1064 nm, a pulse duration of 10 ns, a pulse repetition rate of 10 kHz, and a pulse energy of 1 mJ was used as a source of laser radiation in all our experiments. Deionized water and isopropanol were used as the working liquid. Laser fragmentation in deionized water is accompanied by the formation of boric acid [3], while laser fragmentation in isopropanol leads to the formation of carbon-containing NPs due to the partial decomposition of isopropanol during its optical breakdown [4]. Nevertheless, decomposition products of liquid and large NPs fractions were replaced to pure isopropanol by centrifugation of boron NPs colloid.
Analysis of X-ray diffraction patterns shows that micropowders of boron grade A and boron enriched with the 10B isotope are amorphous, grade B is crystalline. The isotopic composition measured on a secondary ion mass spectrometer of micropowders of boron grade A, boron enriched with the isotope 10B, and boron grade B shows a 10B content of 19.2%, 85.1% and 17.5%, respectively. Laser fragmentation of boron micropowders leads to the formation of spherical NPs. The size distributions obtained using a disk centrifuge CPS 24000 were in the range of 5-100 nm for NPs grade A and 10-40 nm for NPs grade B. The size distribution for boron NPs enriched with the 10B isotope obtained using dynamic light scattering was in the range 10-100 nm. Transmission electron microscopy studies confirm the data obtained using disk centrifuge and dynamic light scattering. Elemental analysis (EDX) shows high purity of boron NPs grade A and boron NPs enriched with the 10B isotope (boron content 99.1%), while boron NPs grade B contains boron in an amount of 91.5%. The obtained B NPs were functionalized with polyethylene glycol polymer to improve colloidal stability and biocompatibility. Using the obtained B NPs in BNCT led to a dramatical enhancement in cancer cell death [5].
This work was supported by Russian Science Foundation, Grant № 24-62-00018.
Fig. 1. TEM image of boron nanoparticles after laser fragmentation by 10 ns laser pulses in isopropanol. Fragmentation time was 40 min.
[1] R.F. Barth, A.H. Soloway, R.G. Fairchild, Boron neutron capture therapy for cancer, Scientific American, 263, 100 (1990).
[2] V. Torresan, et al, Biocompatible iron-boron nanoparticles designed for neutron capture therapy guided by magnetic resonance imaging, Advanced Healthcare Materials, 10, 2001632 (2021).
[3] A.I. Pastukhov, et al, Laser-ablative aqueous synthesis and characterization of elemental boron nanoparticles for biomedical applications, Scientific Reports, 12, 9129 (2022).
[4] K.O Aiyyzhy, E.V. Barmina, V.V. Voronov, G.A. Shafeev, G.G. Novikov, O.V. Uvarov, Laser ablation and fragmentation of Boron in liquids, Optics & Laser Technology, 155, 108393 (2022).
[5] I.N. Zavestovskaya, et al, Laser-Synthesized Elemental Boron Nanoparticles for Efficient Boron Neutron Capture Therapy, International Journal of Molecular Sciences, 24, 17088 (2023).
