Dopamine (DA), as a neurotransmitter in human brain, plays a crucial role in reward motivation and motor control. An improper level of DA can be associated with neurological disorders such as schizophrenia and Parkinson’s disease. To quantify DA, optical DA sensors have emerged as an attractive platform due to their capability of high-precision and label-free measurement, and immunity to electromagnetic interference. However, the lack of selectivity, limited biocompatibility, and complex fabrication processes are challenges that hinder their clinical applications. Here, we report a soft and biocompatible luminescent hydrogel optical sensor capable of recognizing and quantifying DA with a simple and compact interrogation setup. The sensor is made of a hydrogel optical fiber (HOF) incorporated with upconversion nanoparticles (UCNPs). DA molecules are detected through the luminescence energy transfer (LET) between the UCNPs and the oxidation products of DA, while the light-guiding HOF enables both excitation and emission collection of the UCNPs. The hydrogel sensor provides an optical readout that shows a linear response up to 200 μmol/L with a detection limit as low as 83.6 nmol/L. Our results show that the UCNP-based hydrogel sensor holds great promise of serving as a soft and biocompatible probe for monitoring DA in situ.

中文翻译：

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用于原位多巴胺监测的上转换发光水凝胶光学探针

多巴胺 (DA) 作为人类大脑中的一种神经递质，在奖励动机和运动控制中起着至关重要的作用。不适当的 DA 水平可能与神经系统疾病有关，例如精神分裂症和帕金森病。为了量化 DA，光学 DA 传感器因其高精度和无标记测量的能力以及抗电磁干扰能力而成为一个有吸引力的平台。然而，缺乏选择性、有限的生物相容性和复杂的制造工艺是阻碍其临床应用的挑战。在这里，我们报告了一种柔软且生物相容的发光水凝胶光学传感器，能够通过简单紧凑的询问设置识别和量化 DA。该传感器由水凝胶光纤 (HOF) 和上转换纳米粒子 (UCNP) 制成。DA 分子通过 UCNPs 和 DA 的氧化产物之间的发光能量转移 (LET) 检测，而光导 HOF 能够同时收集 UCNPs 的激发和发射。水凝胶传感器提供光学读数，显示线性响应高达 200 μmol/L，检测限低至 83.6 nmol/L。我们的结果表明，基于 UCNP 的水凝胶传感器有望作为一种柔软且生物相容的探针用于原位监测 DA。