Influence of 3-, 4- and 6-layered borophene on biocompatibility with "non-professional" human phagocytes.

The medical application of borophene in fields such as in vivo diagnosis, drug delivery, and photochemical therapy of cancer requires detailed assessment. There is no knowledge about its effects on cells, organs, and the whole organism of humans and animals. It can be assumed that the impact of borophene on cells will be correlated with the aspect ratio of the 2D flakes and their thickness. This study sought to determine if these nanomaterials are biocompatible and, if not, whether their cytotoxicity is caused by their thickness, dosage, or exposure duration in the model cells employed in the study. The influence of 3-, 4- or 6-layer borophene in the concentration range from 0.2 to 1 mg/ml of the medium on the morphology, integrity of the cell membrane, induction of apoptosis and reactive oxygen species and the level of reducing power in MRC-5 cells was investigated. The study showed no effect of borophene on the plasma membrane, no cytotoxic effects leading to apoptosis or necrosis of MRC-5 cells even at high doses of tested nanomaterials and regardless of the number of layers. Borophene had a beneficial effect on human fibroblasts because it increased or did not change the level of reducing power, which balanced of oxidative stress in cells, if induced. These effects allowed maintaining cell viability and functionality. This study opens up research perspectives leading to understanding the mechanisms responsible for maintaining viability in the borophene-exposed cells. The question remains whether borophene is biocompatible in other models, e.g., non-phagocytic cells, and what other molecular mechanisms are involved in maintaining the viability of the borophene-exposed cells. If the biocompatibility of borophene with a wide range of cells is confirmed, it will find numerous applications in biomedicine with special emphasis on Boron Neutron Therapy.