Schulich Faculty of Chemistry, Technion-Israel Institute of Technology, Haifa, Israel.
Department of Biomedical Engineering, Ohio State University, Columbus, Ohio, USA.
Magn Reson Med. 2021 May;85(5):2915-2925. doi: 10.1002/mrm.28595. Epub 2020 Nov 18.
Skin oxygen level is of significance for the diagnosis and treatment of many clinical problems, such as chronic wounds and diabetic foot ulcers. Furthermore, skin oxygen levels can be correlated to arterial oxygen partial pressure, thereby revealing potentially dangerous conditions such as hyperoxia (too much oxygen), which may occur in ventilated neonates. Traditionally, skin oxygen levels are measured using electrochemical methods and, more recently, also by fluorescence lifetime techniques. These approaches suffer from several drawbacks, rendering them suboptimal. The purpose of this work is to develop an electron spin resonance (ESR) -based method for monitoring oxygen partial pressure (pO ) in skin tissue.
A compact sensor for pulsed ESR is designed and constructed. Our ESR-based method makes use of a unique exogenous paramagnetic spin probe that is placed on the skin in a special partially sealed sticker, and subsequently measuring its signal with the compact pulsed ESR sensor that includes a miniature magnet and a small S-band (~2.3 GHz) microwave resonator. The inverse of the spin-spin relaxation time (1/T ) measured by ESR is shown to be linearly correlated with pO levels.
The sensor and its matching sticker were tested both in vitro and in vivo (with human subjects). Measured skin pO levels reached equilibrium after ~2-3 h and were found to be comparable to those measured by continuous-wave (CW) ESR using a large electromagnet.
A compact pulsed ESR sensor with a matching paramagnetic sticker can be used for pO monitoring of the skin tissue, similar to large bulky CW ESR systems.
皮肤氧水平对于许多临床问题的诊断和治疗都具有重要意义，例如慢性伤口和糖尿病足溃疡。此外，皮肤氧水平可以与动脉氧分压相关联，从而揭示潜在的危险情况，例如高氧血症（过多的氧气），这可能发生在通气的新生儿中。传统上，使用电化学方法和最近的荧光寿命技术来测量皮肤氧水平。这些方法存在一些缺点，因此效果并不理想。本研究旨在开发一种基于电子自旋共振（ESR）的方法来监测皮肤组织中的氧分压（pO ）。
设计并构建了用于脉冲 ESR 的紧凑型传感器。我们的基于 ESR 的方法利用了一种独特的外源性顺磁自旋探针，将其放置在特殊的部分密封贴剂上的皮肤表面，并随后使用包括微型磁铁和小型 S 波段（约 2.3 GHz）微波谐振器的紧凑型脉冲 ESR 传感器来测量其信号。ESR 测量的自旋-自旋弛豫时间（1/T ）的倒数与 pO 水平呈线性相关。
该传感器及其匹配的贴纸在体外和体内（人体）都进行了测试。测量的皮肤 pO 水平在 2-3 小时后达到平衡，并且与使用大型电磁铁的连续波（CW）ESR 测量的 pO 水平相当。
具有匹配顺磁贴纸的紧凑型脉冲 ESR 传感器可用于皮肤组织的 pO 监测，类似于大型 CW ESR 系统。
