It is crucial for cell physiology to keep the homeostasis of pH, and it is highly demanded yet challenging to develop luminescence resonance energy transfer (LRET)-based near-infrared (NIR) ratiometric luminescent sensor for the detection of pH fluctuation with NIR excitation. As promising energy donors for LRET, upconversion nanoparticles (UCNPs) have been widely used to fabricate nanosensors, but the relatively low LRET efficiency limits their application in bioassay. To improve the LRET efficiency, core/shell/shell structured β-NaGdF₄@NaYF₄:Yb,Tm@NaYF₄ UCNPs were prepared and decorated with hemicyanine dyes as an LRET-based NIR ratiometric luminescent pH fluctuation-nanosensor for the first time. The as-developed nanosensor not only exhibits good antidisturbance ability, but it also can reversibly sense pH and linearly sense pH in a range of 6.0–9.0 and 6.8–9.0 from absorption and upconversion emission spectra, respectively. In addition, the nanosensor displays low dark toxicity under physiological temperature, indicating good biocompatibility. Furthermore, live cell imaging results revealed that the sensor can selectively monitor pH fluctuation via ratiometric upconversion luminescence behavior.

中文翻译：

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含半菁衍生物组装的上转换纳米荧光粉的NIR比例发光检测活细胞pH波动

保持pH的动态平衡对细胞生理至关重要，因此开发基于发光共振能量转移（LRET）的近红外（NIR）比例发光传感器来检测NIR激发的pH波动对细胞生理发展至关重要。作为LRET的有希望的能量供体，上转换纳米粒子（UCNP）已被广泛用于制造纳米传感器，但是相对较低的LRET效率限制了它们在生物测定中的应用。为了提高效率LRET，核/壳/壳结构的β-NaGdF ₄ @NaYF ₄：镱，铥@ NaYF ₄制备了UCNP，并首次用半花菁染料作为基于LRET的近红外比率发光pH波动纳米传感器进行修饰。发展起来的纳米传感器不仅具有良好的抗干扰能力，而且还可以从吸收和上转换发射光谱分别可逆地感测pH值和线性感测pH值，范围分别为6.0-9.0和6.8-9.0。另外，纳米传感器在生理温度下显示出低的暗毒性，表明良好的生物相容性。此外，活细胞成像结果显示该传感器可以通过比例上转换发光行为选择性监测pH波动。