Evaluation of stability and antitumor activity of two-dimensional black phosphorus modified with positively charged protein

Two-dimensional black phosphorus (2D BP), a novel 2D photoelectric material with excellent near-infrared optical absorption, biocompatibility, and degradability, has shown enormous potential in biomedical field. However, under the action of light, oxygen and water, 2D BP is easily degraded to phosphate and phosphonate. In this work, trastuzumab (Tmab) as a positively charged protein was used to modify 2D BP through electrostatic interaction to form BP-Tmab. The Tmab layer on the surface of 2D BP can effectively protect BP from water, which significantly enhanced the water stability of BP. PEGylated 2D BP (BP-PEG) as a control was also prepared. After 7 days in air-exposed water, the attenuation value of BP-Tmab was only 6.62 ± 2.72% at room temperature, which was much lower than that of naked 2D BP (52.47 ± 2.26%) and BP-PEG (25.84 ± 2.80%) under the same conditions. The result was further confirmed by the temperature changes at different time points under laser irradiation, suggesting that the degradation of BP was effectively reduced by Tmab modification. In addition, BP-Tmab displayed satisfactory biocompatibility and can effectively destroy cancer cells under laser irradiation, showing an excellent photothermal therapy effect.