Noninvasive Monitoring of In Vivo Drug Release

描述（由申请人提供）：在肿瘤靶向化疗中，控释是提高疗效和减少全身副作用的关键策略之一。在本项目中，我们将重点关注磁共振成像（MRI）和光谱成像（MRSI）的独特功能，以无创性地监测药物释放和随后的药物分布。本项目的长期目标是了解载抗癌药物纳米载体的体内药物释放特性，从而阐明载抗癌药物纳米载体的抗癌活性与释放特性之间的关系。我们假设MRI/MRSI可以区分包裹在纳米载体中的药物分子和从纳米载体中释放的药物分子，并允许长期监测缓释制剂，而不像放射性核素模式需要半衰期短的放射性示踪剂。移植MCF-7的SCID小鼠将被用作人类乳腺癌模型，并通过静脉注射含有5-FU、GdDTPA和超顺磁性氧化铁纳米颗粒（SPIO）的纳米载体。MRI/MRSI实验将使用Bruker 9.4T水平孔径光谱仪。我们将使用具有不同重复延迟的多层多回波序列进行MRI，并将获得5-FU的MRSI的19F谱。我们将在注射纳米载体后的不同时间点重复MRI/MRSI实验。完整的纳米载体由于SPIO的T2/T2*效应，对5-FU具有较宽的共振线，并产生负的对比度增强。封装的GdDTPA和5-FU一旦释放就会扩散，而SPIO由于其大尺寸（40- 70 nm），扩散范围要短得多。GdDTPA/5-FU扩散到SPIO负T2增强区以外，MRI/MRSI分别产生正增强对比和游离5-FU窄共振线。我们也期望GdDTPA和5-FU的释放模式相同，在肿瘤中呈现相似的分布模式。此外，我们打算比较体内释放模式和体外释放特性。切除肿瘤的末端脱氧核苷酸转移酶介导的地高辛- dutp缺口末端标记（TUNEL）检测将告诉我们药物分布与治疗活性之间的相关性。因此，我们期望MRI/MRSI可以无创地监测药物释放和随后的肿瘤内药物分布。此外，组织化学分析将验证MRI/MRSI图像，进一步阐明药物释放特征与抗癌治疗活性之间的相关性，并最终通过MRI/MRSI估计药物在肿瘤中的释放/分布的治疗效果。在肿瘤靶向化疗中，控释是提高疗效和减少全身副作用的关键策略之一。为了无创地监测药物释放和随后的肿瘤内药物分布，我们将注意力集中在磁共振成像（MRI）和光谱成像（MRSI）的独特特征上。我们期望我们的创新技术使用MRI/MRSI将提供药物释放和随后在肿瘤中的分布的无创监测。

DESCRIPTION (provided by applicant): In targeted cancer chemotherapy, controlled release is one of the key strategies to increase the efficacy and to reduce systemic side effects. In this project, we have focused attention on a unique feature of magnetic resonance imaging (MRI) and spectroscopic imaging (MRSI) to monitor drug release and subsequent drug distribution noninvasively. The long-term goal of this project is to understand in vivo drug release characteristics of anticancer drug-loaded nanocarriers, and thus to elucidate the correlation between anticancer activity and release characteristics of anticancer drug- loaded nanocarriers. We hypothesize that MRI/MRSI can distinguish drug molecules encapsulated in and released from nanocarriers, and allow for the long-term monitoring of sustained release formulation unlike radionuclide modalities which require radiotracers with short half-life. SCID mice bearing MCF-7 xenografts will be used as human breast cancer model, and nanocarriers containing 5-FU, GdDTPA and superparamagnetic iron oxide nanoparticles (SPIO) will be administered intravenously. Bruker 9.4T horizontal bore spectrometer will be used for MRI/MRSI experiments. We will use a multislice multiecho sequence with different repetition delays for MRI and will acquire 19F spectra for MRSI of 5-FU. We will repeat MRI/MRSI experiments at different time points following injection of nanocarriers. Intact nanocarriers will have broad resonance line for 5-FU and generate negative contrast enhancement due to the T2/T2* effect of SPIO. Encapsulated GdDTPA and 5-FU will diffuse once they released while SPIO diffusion is much shorter range due to their large sizes (40- 70 nm). GdDTPA/5-FU that has diffused beyond the negative T2 enhancement region of SPIO will generate positive contrast enhancement and a narrow resonance line of free 5-FU by MRI/MRSI, respectively. We also expect that release pattern of GdDTPA and 5-FU will be identical and will show similar distribution pattern in the tumor. In addition, we intend to compare in vivo release pattern to in vitro release characteristics. Terminal deoxynucleotidyl transferase-mediated digoxigenin-dUTP nick end-labeling (TUNEL) assay of excised tumor will tell us the correlation between drug distribution and therapeutic activity. Therefore, we anticipate that MRI/MRSI can noninvasively monitor drug release and subsequent intratumoral drug distribution. In addition, histochemical analysis will validate MRI/MRSI images and further elucidate the correlation between drug release characteristics and therapeutic activity against cancer, and eventually estimate the therapeutic effects from drug release/distribution in the tumor by MRI/MRSI. PUBLIC HEALTH RELEVANCE In targeted cancer chemotherapy, controlled release is one of the key strategies to increase the efficacy and to reduce systemic side effects. To monitor drug release and subsequent intratumoral drug distribution noninvasively, we have focused attention on a unique feature of magnetic resonance imaging (MRI) and spectroscopic imaging (MRSI). We anticipate that our innovative technique using MRI/MRSI will provide a noninvasive monitoring of drug release and subsequent distribution in the tumor.