Boron nitride nanotubes and primary human osteoblasts:in vitrocompatibility and biological interactions under low frequency ultrasound stimulation

Abstract

In this paper we investigated a novel and non-invasive approach for an endogenous osteoblast stimulation mediated by boron nitride nanotubes (BNNTs). Specifically, following the cellular uptake of the piezoelectric nanotubes, cultures of primary human osteoblasts (hOBs) were irradiated with low frequency ultrasound (US), as a simple method to apply a mechanical input to the cells loaded with BNNTs. This in vitro study was aimed at investigating the main interactions between hOBs and BNNTs and to study the effects of the 'BNNTs + US' stimulatory method on the osteoblastic function and maturation.A non-cytotoxic BNNT concentration to be used in vitro with hOB cultures was established. Moreover, investigation with transmission electron microscopy/electron energy loss spectroscopy (TEM/EELS) confirmed that BNNTs were internalized in membranal vesicles. The panel of investigated osteoblastic markers disclosed that BNNTs were capable of fostering the expression of late-stage bone proteins in vitro, without using any mineralizing culture supplements. In our samples, the maximal osteopontin expression, with the highest osteocalcin and Ca(2+) production, in the presence of mineral matrix with nodular morphology, was observed in the samples treated with BNNTs + US. In this group was also shown a significantly enhanced synthesis of TGF-β1, a molecule sensitive to electric stimulation in bone. Finally, gene deregulations of the analyzed osteoblastic genes leading to depletive cellular effects were not detected. Due to their piezoelectricity, BNNT-based therapies might disclose advancements in the treatment of bone diseases.

Boron nitride nanomaterials: biocompatibility and bio-applications

“…In addition to the absence of relevant toxicity on the cells, TEM images confirmed the phagocytosis of the material inside the cell cytoplasm. These findings were further corroborated by a later study by the same group, 69 where BNNTs taken up by osteoblast cells were stimulated through low frequency ultrasounds. BNNTs with a length inferior to 500 nm were obtained through a milling and annealing method 70 and coated with poly-L-lysine in order to attain a stable suspension.…”

Effects of Polydopamine Functionalization on Boron Nitride Nanotube Dispersion and Cytocompatibility

“…The results of these studies demonstrated improved dispersion in water and the generation of composite nanomaterials with enhanced mechanical and thermal properties 40,41 . 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 Interestingly, BNNTs possess a unique capacity of generating electric fields under mechanical stimulation (piezoelectricity) 12 , and recent studies indicate that the piezoelectric response of BNNTs is higher than piezoelectric polymers such as PVDF [42][43][44][45] .…”

Boron nitride nanotube-functionalised myoblast/microfibre constructs: a nanotech-assisted tissue-engineered platform for muscle stimulation

“…In our previous studies, C2C12 myoblasts treated with poly‐ l ‐lysine (PLL)‐coated BNNTs at doses of pharmaceutical relevance have been shown to be viable and to efficiently differentiate into myotubes on two‐dimensional (2D) tissue culture plastic and microgrooved hydrogels (Ciofani et al ., ; Ricotti et al ., ). Additionally, preliminary in vitro results obtained on cultures of osteoblasts and neuron‐like cells treated with BNNTs and low‐frequency US have demonstrated that this method could successfully foster their function and differentiation without exerting major cytotoxic effects (Danti et al ., ; Ciofani et al ., ).…”

“…Aqueous BNNT dispersion to administer our cellular models was prepared according to a published procedure (Ciofani et al ., ). Briefly, we used multiwalled BNNTs supplied by the Australian National University of Canberra (Australia), with boron nitride > 97 wt%, residual metal catalysts (Fe and Cr) ~1.5 wt% and a mean aspect ratio < 10 (Danti et al ., ). PLL (MW = 70 000–150 000, Fluka, St. Louis, MO, USA) was used for water stabilisation of BNNTs via non‐covalent coating.…”

“…For example, in this communication we comment on the outcomes obtained comparing Cx43 and myosin expression in 2D vs 3D culture conditions, under the application of BNNTs and/or US stimuli. In particular, combined ‘BNNTs + US’ treatment is supposed to result in BNNT polarization, with putative electric‐like signals to the cells (Ciofani et al ., ; Ricotti et al ., ; Danti et al ., ).…”