As a new low-cost photothermal nanoprobe, Prussian blue nanoparticles (PB NPs) have been demonstrated to have more potential in photothermometric-based point-of-care testing (POCT) application. However, most of the existing PB NP-based photothermometric sensors were constructed mainly relying on in situ generation of PB NPs or their combination with antigens and antibodies, therefore usually suffering from the inherent defects like complicated preparation and cumbersome surface process as well as high-cost modification. To break this limitation of PB NP-based photothermometric POCT, we proposed an ingenious redox reaction-controlled nanoprobe conversion strategy and successfully applied to photothermometric detection of ascorbate oxidase (AAO). In this design, the heat of PB NP photothermal system under 808-nm laser irradiation dramatically decreased with the addition of AA, due to a unique AA-induced Prussian blue to Prussian white (PB-to-PW) conversion. Upon AAO addition, the heat of reaction system increased because of the enzymatic catalytic reaction between AAO and AA, which led to a significant reduction of AA and resultantly inhibited PB-to-PW conversion. Such target-mediated nanoprobe conversion resulted in an obvious temperature change that could be easily detected by a common thermometer and exhibited good linear ranges from 0.25 to 14 mU/mL with a detection limit as low as 0.21 mU/mL for POCT analysis of AAO. This facile, convenient, and portable photothermometric sensing platform provides an innovative route for the design of PB NP nanoprobe-based photothermometric detection methods.

Graphical abstract

中文翻译：

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基于氧化还原反应控制的纳米探针从普鲁士蓝到普鲁士白的转换的灵敏光热生物传感器

作为一种新的低成本光热纳米探针，普鲁士蓝纳米粒子 (PB NPs) 已被证明在基于光热测量的即时检测 (POCT) 应用中具有更大的潜力。然而，现有的大多数基于PB NP的光测温传感器主要依靠PB NPs的原位生成或它们与抗原和抗体的结合来构建，因此通常存在制备复杂、表面工艺繁琐以及高成本修改。为了打破基于 PB NP 的光热 POCT 的这一局限性，我们提出了一种巧妙的氧化还原反应控制的纳米探针转换策略，并成功应用于抗坏血酸氧化酶 (AAO) 的光热检测。在这个设计中，由于独特的 AA 诱导的普鲁士蓝到普鲁士白（PB 到 PW）的转换，PB NP 光热系统在 808 nm 激光照射下的热量随着 AA 的加入而显着降低。添加 AAO 后，由于 AAO 和 AA 之间的酶催化反应，反应体系的热量增加，导致 AA 显着减少，从而抑制了 PB 到 PW 的转化。这种靶介导的纳米探针转换导致明显的温度变化，可以很容易地被普通温度计检测到，并且表现出良好的线性范围，从 0.25 到 14 mU/mL，AAO 的 POCT 分析检测限低至 0.21 mU/mL。这种简便、便携的光热测量传感平台为基于 PB NP 纳米探针的光热测量检测方法的设计提供了一条创新途径。

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