Intein-mediated thyroid hormone biosensors: towards controlled delivery of hormone therapy

Although blood sampling and medical imaging are well-established techniques in clinical diagnostics, they often require long post-processing procedures. Fast and simple quantification of signaling molecules can enable efficient health monitoring and improve diagnoses. Thyroid hormones (THs) treatment relies on trial-and-error dose adjustments, and requires constant tracking via blood tests. Thus, a fast and reliable method that can constantly track THs levels could substantially improve patient quality of life by reducing their visits to doctors. Synthetic biosensors have shown to be inexpensive and easy tools for sensing molecules, with their use in healthcare increasing over time. This study describes the construction of an engineered THs bacterial biosensor, consisting of a split-intein-based TH receptor ligand binding domain (LBD) biosensor that reconstitutes green fluorescence protein (GFP) after binding to TH. This biosensor could quantitatively measure THs concentrations by evaluating fluorescence intensity. In vitro sensing using Escherichia coli produced GFP over a wide dynamic range. The biosensor was further optimized by adding a double LBD, which enhanced its dynamic range until it reached healthy physiological conditions. Moreover, a mathematical model was developed to assess the dynamic properties of the biosensor and to provide a basis for the characterization of other intein-mediated biosensors. This type of biosensor can be used as the basis for novel treatments of thyroid diseases and can be adapted to measure the concentrations of other hormones, giving rise to a series of mathematically characterized modular biosensors.

尽管血液采样与医学成像已是临床诊断领域成熟的技术手段，但二者往往需要耗时较长的后处理流程。对信号分子开展快速简便的定量检测，可实现高效的健康监测并提升诊断效率。甲状腺激素（Thyroid hormones, THs）疗法依赖于反复试错的剂量调整，且需通过血液检测进行持续监测。因此，一种能够持续追踪THs水平的快速可靠检测方法，可通过减少患者就医次数，大幅提升患者的生活质量。合成生物传感器（synthetic biosensors）已被证实是用于分子检测的低成本、易操作工具，其在医疗健康领域的应用正逐年增长。本研究构建了一种工程化THs细菌生物传感器：该传感器由基于分裂内含肽（split-intein）的TH受体配体结合域（ligand binding domain, LBD）构成，在与TH结合后可重构绿色荧光蛋白（green fluorescence protein, GFP）。该生物传感器可通过检测荧光强度，对THs浓度进行定量测定。以大肠杆菌（Escherichia coli）表达GFP完成的体外传感实验证实，该传感器可在较宽的动态范围内实现检测。研究人员通过引入双LBD结构对该生物传感器进行了优化，使其动态范围得到拓展，直至可适配健康人体的生理浓度区间。此外，本研究还构建了数学模型，用于评估该生物传感器的动态特性，并为其他内含肽（intein）介导的生物传感器的表征提供了参考依据。此类生物传感器可作为甲状腺疾病新型疗法的开发基础，同时也可适配其他激素的浓度检测，由此可衍生出一系列经数学表征的模块化生物传感器。