Optimization and validation of integrated microscale technologies for low-cost, automated production of PET molecular imaging tracers for cancer research

项目总结 正电子发射断层扫描(PET)探头(或“示踪剂”)是含有正电子发射的生物分子 同位素，其衰变可以高灵敏度地被检测以执行各种体外或体内3D 用于癌症研究的生化过程的分析。放射性标记物的一个显著优势是组织高度 伽马射线的穿透--这使得细胞水平的发现可以转化为新的动物模型 (例如，研究疾病的机制和治疗)，然后对患者进行分析(例如，预测反应 治疗或评估治疗效果)，全部使用相同的探头。数以千计的PET示踪剂已经 用于评估血管生成、肿瘤微环境(如缺氧)、代谢(如葡萄糖或氨基酸) 酸)、受体密度等。另一个优点是许多PET示踪剂用单一的放射性标记 原子，与荧光团等笨重的标记相比，通常对生物功能的破坏较小。 这些短寿命PET示踪剂的常规生产的当前方法主要针对临床市场， 即用于大批量、多患者批次的生产。对于少数示踪剂(例如[18F]FDG)，需求充足 可以协调安排(即在同一天进行多个患者扫描和研究项目) 高昂的生产成本可以在许多患者和研究人员之间分摊。需求不足的情况下 为了分担成本，PET示踪剂的价格高得令人望而却步。由于放射性同位素只是 生产成本，缩减到较少的放射性并不能显著降低 只需要少量探头的研究人员。成本的其他驱动因素是昂贵的设备和 专门的设施(即热室，在使用大量放射性同位素时保护操作员) 提供给许多机构的癌症研究人员，以及每批消耗的试剂的高昂成本 已生成示踪剂。由于成本较高，许多研究人员选择替代标记方法(例如， 生物发光)，尽管这些方法存在局限性。 我们的初步数据表明，微流控合成器可以成功地产生各种PET示踪剂 同时为解决上述问题提供了独特的优势：(1)液滴微反应器消耗10-1000倍 试剂比常规体系少；(2)与常规体系不同，微型反应器中的摩尔活度 即使在产生少量(放射性)示踪剂时仍保持高水平；(3)紧凑的尺寸 微反应堆可实现局部辐射屏蔽，避免需要热室；(4)小批量生产 对于个人研究人员来说，与典型的热电池相比，使用时需要的辐射屏蔽(厚度)要小得多。 以前的研究已经确定了可行性，并表明微滴合成器有望实现 按需常规、低成本生产示踪剂。这可能使PET“商品化”，并制造出各种示踪剂 任何调查员都可以使用。本提案旨在执行高级开发和验证 使放射性标记示踪剂广泛用于各种癌症研究应用中的分析的技术。

PROJECT SUMMARY Positron-emission tomography (PET) probes (or “tracers”) are biological molecules containing positron-emitting isotopes, the decay of which can be detected with high sensitivity to perform a variety of in vitro or 3D in vivo assays of biochemical processes for cancer research. A significant advantage of radiolabels is the high tissue penetration of gamma rays – this allows discoveries at the cellular level to be translated to new animal models (e.g. to study the mechanisms and treatment of disease) and then to assays in patients (e.g. to predict response to treatment or assess efficacy of treatment), all with the same probe. Thousands of PET tracers have been reported for assessing angiogenesis, tumor microenvironment (e.g. hypoxia), metabolism (e.g., glucose or amino acids), density of receptors, etc. Another advantage is that many PET tracers are labeled with a single radioactive atom, typically causing less disruption to biological function compared to bulky labels such as fluorophores. Current methods for routine production of these short-lived PET tracers are aimed largely at the clinical market, i.e. for production of large, multi-patient batches. For a few tracers (e.g. [18F]FDG), there is sufficient demand that scheduling can be coordinated (i.e. many patient scans and research projects on the same day) and the high production cost can be divided among many patients and researchers. In cases where demand is insufficient to enable cost-sharing, PET tracers are prohibitively expensive. Since the radioisotope is only a fraction of the production cost, scaling down to a smaller amount of radioactivity does not provide significant cost reduction for researchers that only need a small quantity of the probe. Other drivers of cost are the expensive equipment and specialized facilities (i.e. hot cells, to protect operators when using high amounts of radioisotope) that are not available to cancer researchers at many institutions, and the high cost of reagents consumed for each batch of tracer produced. Due to the high cost, many researchers choose alternative labeling methods (e.g. fluorescent, bioluminescent) despite the limitations of these approaches. Our preliminary data have shown that microfluidic synthesizers can successfully produce diverse PET tracers while providing unique advantages to solve the above problems: (1) Droplet microreactors consume 10-1000x less reagents than conventional systems; (2) Unlike conventional systems, molar activity in microreactors remains high even when producing small quantities (radioactivity) of the tracer; (3) The compact size of microreactors enables local radiation shielding and avoids the need for hot cells; (4) Production of small batches for individual researcher use will require much less radiation shielding (thickness), compared to typical hot cells. Previous studies have established feasibility and suggest that microdroplet synthesizers are poised to enable routine, low-cost production of tracers on demand. This could “commoditize” PET and make diverse tracers available to any investigator. This proposal seeks to perform advanced development and validation of this technology to make radiolabeled tracers widely available for assays in a variety of cancer research applications.