Noninvasive Monitoring of In Vivo Drug Release

描述（由申请人提供）：在靶向癌症化疗中，控释是提高疗效和减少全身副作用的关键策略之一。在这个项目中，我们集中注意力在磁共振成像（MRI）和光谱成像（MRSI）的一个独特的功能，以监测药物释放和随后的药物分布非侵入性。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相关性。我们假设MRI/MRSI可以区分封装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，并且允许长期监测缓释制剂，而不像需要半衰期短的放射性示踪剂的放射性核素方式。携带MCF-7异种移植物的SCID小鼠将用作人乳腺癌模型，并且将静脉内施用含有5-FU、GdDTPA和超顺磁性氧化铁纳米颗粒（SPIO）的纳米载体。Bruker 9.4T水平孔光谱仪将用于MRI/MRSI实验。我们将使用具有不同重复延迟的多层多回波序列进行MRI，并将采集5-FU MRSI的19 F光谱。我们将在注射纳米载体后的不同时间点重复MRI/MRSI实验。完整的纳米载体将具有5-FU的宽共振线，并且由于SPIO的T2/T2 * 效应而产生负对比度增强。包封的GdDTPA和5-FU一旦释放就会扩散，而SPIO扩散的范围要短得多，因为它们的尺寸很大（40 - 70 nm）。GdDTPA/5-FU扩散到SPIO的负T2增强区之外，MRI/MRSI分别产生正对比增强和游离5-FU的窄共振线。我们还预期GdDTPA和5-FU的释放模式将是相同的，并且在肿瘤中将显示相似的分布模式。此外，我们打算比较体内释放模式与体外释放特征。末端脱氧核苷酸转移酶介导的地高辛-dUTP缺口末端标记（TUNEL）检测切除的肿瘤将告诉我们药物分布和治疗活性之间的相关性。因此，我们预期MRI/MRSI可以无创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，并进一步阐明药物释放特性与抗癌治疗活性之间的相关性，并最终通过MRI/MRSI评估肿瘤中药物释放/分布的治疗效果。在靶向癌症化疗中，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）的独特功能上。我们预计，我们的创新技术，使用MRI/MRSI将提供一个非侵入性监测药物释放和随后的分布在肿瘤。

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.