Gold nanoparticle–modified black phosphorus nanosheets with improved stability for detection of circulating tumor cells

Gold nanoparticle (AuNP)–anchored BP nanosheets were synthesized through in situ growth of AuNPs onto BP. Due to the strong chelating ability of P or phosphorus oxides with AuNPs, the stability of BP is improved. As proof-of-concept demonstration of the functionalized BP, electrochemical detection of circulating tumor cells (CTCs) based on BP@AuNPs@aptamer as a probe combined with immunomagnetic separation is reported. The aptamer can specifically bind with CTCs, while the phosphorus oxides including phosphite ion and phosphate ion (PxOy species) on BP and aptamer can react with molybdate to generate an electrochemical current, leading to dual signal amplification. The biosensor is applied to MCF-7 cell detection and displays good analytical performance with a detection limit of 2 cell mL−1. Furthermore, the practicality of this biosensor was validated through sensitive determination of MCF-7 cells in human blood. Therefore, the reported biosensor could be applied to detect other biomarkers, offering an ultrasensitive strategy for clinical diagnostics.