HoloMonitor i ny forskningsrapport inom nanoteknologi

Hexagonal Boron Nitride Functionalized with Au Nanoparticles—Properties and Potential Biological Applications

Forskningsrapporten offentliggjordes 9 Augusti.
Received: 9 July 2018 / Accepted: 4 August 2018 / Published: 9 August 2018

Rapporten handlar om nanoteknologi inom medicinområdet.
Den berör ett nytt material, Boron nitride, som forskarna påvisar går att använda som läkemedelsbärare, då som bärare av cancermedicin.
Man ser även möjligheter att använta materialet inom s.k Fotodynamisk terapi för just cancerpatienter.

Boron nitride

Materialet beskrivs i Wikipedia enligt följande:
Boron nitride is a heat and chemically resistant refractory compound of boron and nitrogen with the chemical formula BN. It exists in various crystalline forms that are isoelectronic to a similarly structured carbon lattice. The hexagonal form corresponding to graphite is the most stable and soft among BN polymorphs, and is therefore used as a lubricant and an additive to cosmetic products. The cubic (sphalerite structure) variety analogous to diamond is called c-BN; it is softer than diamond, but its thermal and chemical stability is superior.
The rare wurtzite BN modification is similar to lonsdaleite and may even be harder than the cubic form.
Because of excellent thermal and chemical stability, boron nitride ceramics are traditionally used as parts of high-temperature equipment. Boron nitride has potential use in nanotechnology.

Ur rapporten klipper jag valda delar.

Abstract
Hexagonal boron nitride is often referred to as white graphene. This is a 2D layered material, with a structure similar to graphene. It has gained many applications in cosmetics, dental cements, ceramics etc. Hexagonal boron nitride is also used in medicine, as a drug carrier similar as graphene or graphene oxide. Here we report that this material can be exfoliated in two steps: chemical treatment (via modified Hummers method) followed by the sonication treatment. Afterwards, the surface of the obtained material can be efficiently functionalized with gold nanoparticles. The mitochondrial activity was not affected in L929 and MCF-7 cell line cultures during 24-h incubation, whereas longer incubation (for 48, and 72 h) with this nanocomposite affected the cellular metabolism. Lysosome functionality, analyzed using the NR uptake assay, was also reduced in both cell lines. Interestingly, the rate of MCF-7 cell proliferation was reduced when exposed to h-BN loaded with gold nanoparticles. It is believed that h-BN nanocomposite with gold nanoparticles is an attractive material for cancer drug delivery and photodynamic therapy in cancer killing.

Introduction
Recently, graphene, related two-dimensional crystals and hybrid particles have been intensively studied in the context of technological and scientific evolution. Unique properties of graphene allow for using it for various purposes in many fields (e.g., biomedical applications, energy storage, electronic devices, biosensors, spintronics or photonics) [1]. Hexagonal boron nitride (h-BN) is one of the 2D layered materials with specific properties [1]. BNs were considered only as synthetics, but recently they have also been discovered in the natural environment (Qingsongite (IMA2013-30)—natural analogue of cubic boron nitride) [2,3]. Hexagonal boron nitride is an analogue of graphite. In its structure, alternating B and N atoms substitute C atoms [4]. Boron and nitrogen atoms are linked with each other via strong B-N covalent bonds to form interlocking hexagonal rings.

Methods

2.7. Microscopic Analyses

Firstly, the morphology of L929 and MCF-7 cell lines exposed to the h-BN_AuNP nanocomposite at different concentrations and control samples was analyzed using a Nikon TS-100 phase contrast inverted microscope (Nikon, Melville, NY, USA) at 400× magnification.

Secondly, holographic microscopy label-free images were obtained using the HM4 HoloMonitor™ (Phase Holographic Imaging, Lund, Sweden). For presented analyses, the HoloMonitor™ connected to the computer was placed inside a CO₂ incubator (Memmert GmbH, Germany) to capture time-lapse image sequences during the cell treatment. 

Similarly to the phase contrast microscopy, the images using the HoloMonitor M4 were taken for different concentrations of the h-BN_AuNP nanocomposite and the control sample for both cell lines. 

The time-laps image sequence was recorded every 1 min for 24–72 h (24 h after cell seeding). The doubling time (DT) was established basing on holographic observations, as a measure of cell growth for each cell line using the following Formula (1):

Doubling Time=duration×log(2)log(Final concentration)−log(Initial concentration) 

Figure 7. Morphology of the L929 and the MCF-7 cell lines incubated with the h-BN_AuNP nanocomposite. L929 control culture (A), L929 culture at 24 h (B), 48 h (C) and 72 h (D), MCF-7 control culture (E), MCF-7 culture at 24 h (F), 48 h (G) and 72 h (H) (DT—doubling time).

Similarly, time-lapse image sequences were taken using a HoloMonitor™ M4. L929 and MCF-7 cell lines were exposed to the h-BN_Au nanocomposite at a concentration of 10.0 µg mL⁻¹ for 24, 48 and 72 h (Figure 7). L929 cells did not show any significant differences in the presence of the nanocomposite (Figure 7B–D). The DT value was determined basing on image sequences. The DT value for the L929 control was 16.82 h, while the DT values of the experimental culture were 17.16 h, 22.29 h and 22.47 h for 24-, 48- and 72-h incubation, respectively. L929 cells showed no reduction in proliferation under experimental conditions for cultures exposed to h-BN_AuNP during a 24-h incubation, whereas cell doubling times for 48- and 72-h incubations were higher in comparison to the control culture.

Results obtained for the MCF-7 cell line incubated with h-BN_AuNP demonstrated a stronger effect on the cells at a concentration of 10.0 µg mL⁻¹ (Figure 7F–H). MCF-7 cells did not show any visible morphological changes in comparison to the control culture, but the DT analysis indicated a reduction in proliferation capacity. The DT value for the MCF-7 control sample was 42.41 h, whereas the doubling time for experimental cultures was 52.93 h, 68.70 h, and 97.89 h for 24-, 48-, and 72-h incubations, respectively.

Conclusions

These results make the new hybrid nanomaterial an interesting tool not only for anticancer therapy, but also can be used as a platform in biosensor design or in tissue engineering. It is worth emphasizing that the effect of the h-BN_Au nanoparticle on living structures should be examined in greater detail.