Development of pH-Sensitive Probes for in vivo Cerenkov Imaging

项目摘要/摘要 这个项目的主要目标是开发pH敏感的荧光团来确定肿瘤微环境。 使用切伦科夫成像技术建立乳腺癌模型。肿瘤微环境中酸度增加(TME) 在癌细胞的侵袭和转移中起作用，并导致化疗耐药。 这一代谢特征激发了人们对探索细胞外肿瘤pH测量和 活体成像。肿瘤微环境pH值的降低是由于代谢失调所致 主要由癌细胞中糖酵解通量增加引起。β粒子发射的切伦科夫辐射是 一种潜在的体内pH成像工具，因为对pH敏感的荧光团或发色团可以选择性地 衰减其多光谱发射，提供定量读数。 当像电子和正电子这样的亚原子粒子从衰变中发出时，切伦科夫辐射就会发生 核苷酸在电介质中的传播速度比光速还快。它们高速运动的速度 亚原子粒子的运动导致沿着粒子轨迹产生多光谱光子。这 多光谱发射是连续的，包括可见光谱，可以被pH选择性地衰减 在化合物的吸收极大处的敏感的荧光团或发色团。选择信号 衰减，即所谓的选择性带宽猝灭，可以被量化并与pH值相关， 为体内pH成像提供了一种非侵入性技术。 这一提议将检验pH对切伦科夫多光谱发射的选择性吸收这一假设 灵敏的荧光团将通过切伦科夫成像提供TME的准确pH测量。这个 假设将通过以下具体目标进行检验： 具体目标1：切伦科夫活性、pH敏感荧光团的合成和表征：这将包括 金属螯合剂DOTA或NOTA与部分pH敏感荧光团的偶联和络合 放射性金属68Ga和90Y，以及化学和光学表征。 具体目标2：体外评价切伦科夫活性、pH敏感的荧光团：pH滴定曲线 构造为将通过切伦科夫成像获得的平均辐射值与pH值相关联。细胞 将进行摄取和毒性研究。 具体目标3：在体内评价切伦科夫活性、pH敏感的荧光团：合成的探针将被 静脉注射到荷有乳腺癌肿瘤的小鼠体内。将使用PET成像来评估 肿瘤的生物分布和探针传递。切伦科夫成像将用于测量TME的pH值。 将使用syrosingopine对乳酸运输进行药理学调节，以改变肿瘤的pH和 评估切伦科夫成像技术的敏感性。

PROJECT SUMMARY/ABSTRACT The principal goal of this project is to develop pH-sensitive fluorophores to determine tumor microenvironment pH in breast cancer models using Cerenkov imaging. Increased acidity in the tumor microenvironment (TME) plays a role in the invasion and metastasis of cancer cells and contributes to chemotherapeutic resistance. This metabolic hallmark has sparked interest in the exploration of extracellular tumor pH measurement and imaging in vivo. The decrease in tumor microenvironment pH is due to a deregulated metabolism predominantly arising from increased glycolytic flux in cancer cells. Cerenkov radiation emitted by β-particles is a potential tool for pH imaging in vivo, since pH-sensitive fluorophores or chromophores can selectively attenuate its multispectral emission, providing a quantitative readout. Cerenkov radiation occurs when subatomic particles like electrons and positrons emitted from decaying nucleotides travel faster than the speed of light in a dielectric medium. The high speed at which these subatomic particles travel results in the production of multispectral photons along the particle’s trajectory. This multispectral emission is continuous, includes the visible spectrum and can be selectively attenuated by pH sensitive fluorophores or chromophores at the absorption maxima of the compounds. The selective signal attenuation, known as selective bandwidth quenching can be quantified and correlated with a pH value, providing a non-invasive technique for pH imaging in vivo. This proposal will test the hypothesis that selective absorption of the Cerenkov multispectral emission by pH sensitive fluorophores will provide accurate pH measurements of the TME through Cerenkov imaging. The hypothesis will be tested by the following Specific Aims: Specific Aim 1: Synthesis and characterization of Cerenkov-active, pH sensitive fluorophores: This will include conjugation and chelation of selected pH-sensitive fluorophores with the metal chelators DOTA or NOTA and radiometals 68Ga and 90Y, in addition to chemical and optical characterization. Specific Aim 2: In vitro evaluation of Cerenkov-active, pH sensitive fluorophores: A pH titration curve will be constructed to correlate average radiance values obtained through Cerenkov imaging to pH values. Cell uptake and toxicity studies will be performed. Specific Aim 3: In vivo evaluation of Cerenkov-active, pH sensitive fluorophores: Synthesized probes will be injected intravenously into mice bearing breast cancer tumors. PET imaging will be used to assess biodistribution and probe delivery into tumors. Cerenkov imaging will be used to measure TME pH. Pharmacological modulation of lactate transport using syrosingopine will be done to alter the tumor pH and assess sensitivity of the Cerenkov imaging technique.