by zhan14 | Sep 26, 2017 | Projects
Abstract
To accelerate the development of nanotechnologies for drug and gene delivery, it is highly desired to construct nanoparticles with imaging capabilities so that the process of delivery and release can be monitored and quantified with a medical imaging modality. Although there have been successful preclinical studies that showed the possibility of such monitoring, there is clearly a gap between the demand for clinically-compatible imaging methods to monitor the nanoparticle-mediated drug delivery and release and the current nanoparticle tagging strategies, which often require the use of metallic or radioactive contrast agents. To address this gap, bioorganic molecules have recently been developed as “non-labeled” (i.e., not radioactive, and not paramagnetic- or super-paramagnetic-) tracers that can be detected through Chemical Exchange Saturation Transfer (CEST) MRI technology. The long-term goal of our research is to exploit bioorganic drugs or drug analogues as CEST MR imaging contrast agents for tagging of nanoparticles, and subsequently translating this new technology to clinical applications. As an initial demonstration of such a principle, this application aims to develop, without the need for additional imaging probes, a sensitive CEST MRI-trackable liposome system to monitor tumor-targeted delivery of 5-FC, and consequently, to predict the therapeutic effect of cytosine deaminase (CD)/5-FC gene therapy. The central hypothesis is that the CEST signal carried by 5-FC can be directly used to detect 5-FC encapsulating liposomes, thus enabling the monitoring and potential quantification of drug-carrying nanoparticles with CEST MRI. Guided by strong preliminary data, this hypothesis will be tested through three specific aims: 1) To develop a sensitive CEST MRI-trackable liposome encapsulating prodrug for 5-FC;2) to assess antitumor effects of liposome-mediated prodrug delivery;and 3) to monitor liposome-mediated prodrug delivery using CEST MRI. Under the first aim, starting from an already proven liposomal formulation with sufficient CEST detectability, we will optimize the liposomal formulation to obtain a system with improved CEST sensitivity as well as favorable characteristics for drug delivery. Under the second and third aims, we will apply the self-trackable liposome system on experimental animals, assess the antitumor effects, and quantify the enhanced drug delivery with CEST MRI.
These aims are expected to result in a translatable nanotechnology to obtain tumor-targeted prodrug delivery in CD suicide gene therapy that can be monitored by non-invasive CEST MRI. The innovation of this proposed research lies in a “non-labeled” approach to tag nanoparticles based on the drugs they carry. The proposed research is significant, because it is expected to shift the paradigm of the tagging strategy for MR imaging of nanoparticle-mediated drug delivery from metallic agents to bioorganic drug analogues. Ultimately, such a new multifunctional nanoparticle system has the potential to boost the development of an image-guided nanoparticle system for gene and drug delivery, either as an ‘effect enhancer’for existing therapies or as an initiator of new therapies
Public Health Relevance
The project is relevant to public health because it is expected to result in a nanoparticle drug delivery platform to improve the monitoring of cancer gene therapy with the help of MR imaging. This proposed technology enables the monitoring of nanoparticles directly by the MR signal carried by their encapsulated drugs, through a novel MRI contrast mechanism, chemical exchange saturation transfer (CEST), and thus eliminates the need for additional imaging agents in the nanoparticle drug carriers. Successful accomplishment of the proposed research will form the basis of a clinically translatable nanotechnology-MR imaging platform to improve existing cancer gene therapies, which is highly relevant to the part of NIH’s mission.
by zhan14 | Sep 26, 2017 | Projects
Abstract
Quantitative imaging technologies for the characterization of the size-dependent tumor vascular permeability (i.e., in the macro- to nano- size range) are of great clinical interest. Such technologies will be extremely useful for oncologists to assess the tumor vascular permeability to drugs at different sizes and, based on the drug accessibility, to stratify patients for the appropriate treatment. Moreover it can be used to monitor the tumor responses to any interventions that can potentially modulate the tumor vascular permeability and improve the drug delivery. In the current application, we propose to directly use the highly-safe, clinically-available dextrans as new MRI probes for assessing tumor vascular permeability without the need for any radioactive, paramagnetic, or super-paramagnetic label. In this approach, dextran is detected directly via its exchangeable hydroxyl (OH) protons using a recently emerged MRI contrast mechanism, Chemical Exchange Saturation Transfer (CEST), namely dextran-enhanced CEST (dexCEST). Because dextrans are available in a wide range of particle sizes– from 5 to 54 nm for molecular weights (MW) from 10 kD to 2 MD, respectively, it is therefore feasible to use them as macro- and nano-sized MR imaging agents in a broad range of applications. As such, we hypothesize that dexCEST MRI can be used to assess the size-dependent tumor vascular permeability, and to monitor the response in the tumor vascular permeability of pancreatic cancer to stroma-targeting therapies. In particular, we will first fully optimize and validate dexCEST MRI detection to assess size-dependent tumor vascular permeability of experimental pancreatic ductal adenocarcinoma (PDAC) tumors. Then, we will use this technique to monitor the tumor response to stroma-targeting therapies in experimental PDAC tumors, which will lead to the evaluation of the use of dexCEST MRI as an imaging biomarker to quantify the efficacy of stroma-depleting drugs. The successful completion of this project will have an immediate impact on the pre-clinical development and clinical implementation of stroma-targeting therapies to treat hypo-permeable PDAC in a personalized medicine manner. Because many new drugs are in macro-size range (i.e., monocolonal antibodies) and nano-size range (nanomedicine), our approach is expected to play an important role in the clinical implementation of newly developed chemotherapy and immunotherapy, as well as their combination with stroma-targeting therapies. In addition, we expect that these developments can be easily tailored to other types of solid tumors.
Public Health Relevance
The project is relevant to public health because it is expected to result in innovative and translatable medical imaging technology. This will establish an imaging-based protocol for characterizing the tumor vascular permeability in solid tumors such as Pancreatic ductal adenocarcinoma (PDAC), one of the most lethal types of cancer, and assessing the response of the tumor vasculature to therapies. This proposed technology relies on the use of clinically available dextrans and a label-free MRI method that directly detects dextrans via the MRI signal inherently carried by hydroxyl protons using a technique called chemical exchange saturation transfer (CEST). Thus, there is no need for extra chemical-, paramagnetic-, or radioactive- imaging labeling. The successful accomplishment of the proposed research will lead to a highly translatable MR image-guidance method for the development and clinical implementation of nanomedicine in a personalized medicine manner, which is highly relevant to the mission of NIH.
by zhan14 | Sep 26, 2017 | Projects
Abstract
It is highly desired to develop new non-invasive imaging approach for detecting bacterial infection with improved specificity and spatial-temporal resolution. Although to date there are a number of molecular imaging approaches have been demonstrated for bacterial infection in the preclinical animal models, there is clearly a gap between the demand of clinically-compatible imaging methods and conventional tagging strategies, which often require the use of metallic or radioactive contrast agents. To address this gap, we are developing a ?non-labeled? (i.e., not radioactive, and not paramagnetic- or super-paramagnetic-) approach for detecting bacteria. In this approach bacterial cells are directly detected through their endogenous molecules using an innovative MRI technology called Chemical Exchange Saturation Transfer (CEST). The long-term goal of our research is to exploit this endogenous bacteria-specific CEST MRI signal to detect pathogenic bacteria and monitor the progress of bacterial infection. As initially demonstrated in solid tumors, we showed that CEST MRI could detect a therapeutic bacteria C. novyi-NT, a genetically modified bacteria strain currently in the Phase I clinical trial for treating solid tumors. Based on the preliminary data, we hypothesize that CEST MRI that detects the germination and proliferation of C. novyi-NT can be used as a non-invasive imaging biomarker for predicting the success of bacteriolytic therapy on glioma, a highly lethal brain tumor type. We plan to test our hypothesis through completing the following two specific aims: 1) To improve the specificity of bacterial CEST contrast using newly developed CEST technologies, and 2) To test and validate the optimized bacterial CEST MRI detection in the C. novyi-NT cancer therapy. We anticipate that accomplishing these aims will result in a highly translatable MRI technology specifically for bacterial detection, which could be used immediately as an imaging biomarker in the clinical trials of C.novyi-NT bacteriolytic therapy. More importantly, the knowledge gained from this project will enable a further expansion of using the proposed CEST MRI methods to the detection of many other types of bacteria, which will be enormously useful for the diagnosis and treatment monitoring of bacterial infection in deep organs, such as brain, which are currently difficult to detect.
Public Health Relevance
The project is relevant to public health because it is expected to result in an innovative MRI technology for the diagnosis and treatment monitoring of bacterial infection. This proposed technology enables the monitoring of the proliferation of bacteria directly by the endogenous MRI signal carried by the bacterial cells, through a novel MRI contrast mechanism, chemical exchange saturation transfer (CEST), and thus eliminates the need to inject exogenous imaging agents. Successful accomplishment of the proposed research will form the basis of a clinically translatable MR imaging technology not only for developing novel bacteria based cancer therapies, but also for improving the diagnosis and treatment monitoring of bacteria infection in general, both of which are highly relevant to the part of NIH’s mission.
