Department of Materials Science and Technology, Faculty of Advanced Engineering, Tokyo University of Science, 6-3-1 Niijuku, Tokyo 125-8585, Katsushika, Japan.
ACS Appl Bio Mater. 2024 Jun 17;7(6):3821-3827. doi: 10.1021/acsabm.4c00201. Epub 2024 May 24.
Near-infrared fluorescence (NIRF) thermometry is an emerging method for the noncontact measurement of deep temperatures. Fluorescence-lifetime-based methods are effective because they are unaffected by optical loss due to excitation or detection paths. Moreover, the physiological changes in body temperature in deep tissues and their pharmacological effects are yet to be fully explored. In this study, we investigated the potential application of the NIRF lifetime-based method for temperature measurement of deep tissues in the abdomen using rare-earth-based particle materials. β-NaYF particles codoped with Nd and Yb (excitation: 808 nm, emission: 980 nm) were used as NIRF thermometers, and their fluorescence decay curves were exponential. Slope linearity analysis (SLA), a screening method, was proposed to extract pixels with valid data. This method involves performing a linearity evaluation of the semilogarithmic plot of the decay curve collected at three delay times after cutting off the pulsed laser irradiation. After intragastric administration of the thermometer, the stomach temperature was monitored by using an NIRF time-gated imaging setup. Concurrently, a heater was attached to the lower abdomens of the mice under anesthesia. A decrease in the stomach temperature under anesthesia and its recovery via the heater indicated changes in the fluorescence lifetime of the thermometer placed inside the body. Thus, NaYF:Nd/Yb functions as a fluorescence thermometer that can measure temperature based on the temperature dependence of the fluorescence lifetime at 980 nm under 808 nm excitation. This study demonstrated the ability of a rare-earth-based NIRF thermometer to measure deep tissues in live mice, with the proposed SLA method for excluding the noisy deviations from the analysis for measuring temperature using the NIRF lifetime of a rare-earth-based thermometer.
近红外荧光（NIRF）测温是一种用于非接触式深部测温的新兴方法。基于荧光寿命的方法是有效的，因为它们不受激发或探测路径的光损耗的影响。此外，深部组织体温的生理变化及其药理学效应尚未得到充分探索。在这项研究中，我们使用基于稀土的颗粒材料研究了基于 NIRF 寿命的方法在腹部深部组织测温中的潜在应用。β-NaYF 颗粒共掺 Nd 和 Yb（激发：808nm，发射：980nm）作为 NIRF 温度计，其荧光衰减曲线呈指数型。斜率线性分析（SLA）是一种筛选方法，用于提取具有有效数据的像素。该方法涉及对在切断脉冲激光照射后采集的三个延迟时间的衰减曲线的半对数图进行线性评估。通过胃内给药后，使用 NIRF 时间门控成像装置监测胃温度。同时，在麻醉下将加热器附着在小鼠的下腹部。麻醉下胃温下降和通过加热器恢复表明体内放置的温度计荧光寿命发生变化。因此，NaYF:Nd/Yb 可作为荧光温度计，可根据 808nm 激发下 980nm 处荧光寿命对温度的依赖性测量温度。本研究证明了基于稀土的 NIRF 温度计在活体小鼠中测量深部组织的能力，并提出了 SLA 方法，用于排除分析中来自噪声的偏差，以使用基于稀土的温度计的 NIRF 寿命测量温度。
