细胞外 pH 值改变与各种病理状况（包括癌症、炎症和代谢紊乱）之间的相关性是众所周知的。大量 pH 测量无法报告细胞表面的细胞外 pH 值。然而，用于以高空间分辨率测量细胞外 pH 值的合适工具数量有限，并且没有一个在世界各地的实验室中得到普遍使用。在这项研究中，开发了一种用于测量细胞外 pH 值的多功能比率纳米传感器。该纳米传感器由生物相容性聚苯乙烯纳米粒子组成，负载有 pH 惰性参考染料尼罗红，并用 pH 响应荧光素染料进行表面功能化。纳米传感器配备了靶向部分，可以粘附在细胞膜上，从而可以直接测量细胞表面的细胞外 pH 值。该纳米传感器在 5.5-9.0 范围内表现出灵敏的比率 pH 响应，计算出的 pKa 为 7.47。该范围最佳地涵盖了大多数健康细胞和 pHe 异常的细胞（例如癌细胞）的细胞外 pH (pHe)。结合纳米传感器靶向细胞膜的能力、其高稳健性、可逆性和生物相容性，pHe 纳米传感器被证明非常适合细胞外 pH 值的原位测量，甚至可以在较长的时间内进行。这种 pH 纳米传感器有潜力通过提高我们对细胞微环境（细胞外 pH 值在细胞微环境中发挥重要作用）的理解来推进生物医学研究。© 2024。作者。

The correlation between altered extracellular pH and various pathological conditions, including cancer, inflammation and metabolic disorders, is well known. Bulk pH measurements cannot report the extracellular pH value at the cell surface. However, there is a limited number of suitable tools for measuring the extracellular pH of cells with high spatial resolution, and none of them are commonly used in laboratories around the world. In this study, a versatile ratiometric nanosensor for the measurement of extracellular pH was developed. The nanosensor consists of biocompatible polystyrene nanoparticles loaded with the pH-inert reference dye Nile red and is surface functionalized with a pH-responsive fluorescein dye. Equipped with a targeting moiety, the nanosensor can adhere to cell membranes, allowing direct measurement of extracellular pH at the cell surface. The nanosensor exhibits a sensitive ratiometric pH response within the range of 5.5-9.0, with a calculated pKa of 7.47. This range optimally covers the extracellular pH (pHe) of most healthy cells and cells in which the pHe is abnormal, such as cancer cells. In combination with the nanosensors ability to target cell membranes, its high robustness, reversibility and its biocompatibility, the pHe nanosensor proves to be well suited for in-situ measurement of extracellular pH, even over extended time periods. This pH nanosensor has the potential to advance biomedical research by improving our understanding of cellular microenvironments, where extracellular pH plays an important role.© 2024. The Author(s).