In vivo simulation environment for fluorescence molecular tomography using Monte Carlo method

Building on decades of technological advances and imaging experience, during which noninvasive imaging of cardiac structure and function, myocardial perfusion and viability, and noncoronary vascular pathology have become intimately entwined in routine clinical practice, advanced imaging techniques are now poised to deliver noninvasive coronary arteriograms and to delineate the coronary artery wall in exquisite detail. At the same time that these highly promising methods for anatomic imaging at the macroscopic level are creating great excitement among physicians, their patients, and the public, a quieter imaging revolution is underway with steady progress in detecting and tracking fundamental biological processes at the cellular and subcellular levels. In the era of genomic research, molecular biology, and stem cell therapies, these methods have great potential to accelerate understanding of basic pathophysiological processes in animals and humans and to develop new tools for early diagnosis and drug development. Cardiovascular molecular imaging is taking hold. See p 1800 Molecular imaging is the science of visually representing, characterizing, and quantifying cellular/subcellular biological processes in intact organisms. These processes include gene expression, protein–protein interaction, signal transduction, cellular metabolism, and both intracellular and intercellular trafficking. Molecular imaging has the potential to quantify these events, to monitor multiple events simultaneously, to localize these events in 3 dimensions, and to monitor these events serially. Thus, biological processes can be identified and studied in time and space, providing “4-dimensional” information. The emergence of molecular imaging has coincided with and has been made possible by the enormous progress in molecular biology, cell biology, and transgenic animal models, as well as the development of imaging probes that are specific, reproducible, and quantifiable.1 Molecular imaging was once the sole domain of nuclear medicine, with tracers developed for both positron emission tomography (PET) and single photon emission computed tomography (SPECT). Examples include antimyosin antibodies for …

Emerging near-infrared targeting diagnostic and therapeutic strategies for ischemic cardiovascular and cerebrovascular diseases

Increases in intracranial pressure (ICP) may occur in patients of cerebral edema, brain tumors, encephalitis, brain injury etc. The care of these patients has been improved with continuous ICP monitoring. However, all the present clinical ICP monitors are invasive. Non-invasive ICP monitor is greatly expected. In this paper, a new method for ICP non-invasive monitoring using near-infrared light is proposed. Both theoretical and experimental studies have shown that correlation analysis applied to ICP, cerebrospinal fluid (CSF) and near-infrared diffuse reflection light from the brain tissue provides a possibility for non-invasive ICP detection. First, the correlation between the reflected light and the thickness of CSF is studied with Monte-Carlo simulations. It is concluded that the intensity of the reflected light changes significantly with the thickness of CSF, suggesting the feasibility to detect ICP by measuring the diffuse reflection near-infrared light from the brain tissue because the thickness of CSF changes with ICP. Secondly, the correlation of the diffuse reflection light and ICP is studied based on the experimental data acquired with helps of volunteers. It has been proved very promising to determine ICP non-invasively using near-infrared light.

Multiplexed Superresolution CRISPR Imaging of Chromatin in Living Cells

PurposeA sensitive and specific imaging method to detect metastatic cancer cells in lymph nodes to detect the early-stage breast cancer is still a challenge. The purpose of this study was to investigate a novel breast cancer–targeting and tumour microenvironment ATP-responsive superparamagnetic iron oxide nanoparticles (SPIOs) imaging probe (abbreviated as SPIOs@A-T) that was developed to detect lymph node metastasis through fluorescence molecular imaging (FMI) and magnetic particle imaging (MPI).MethodsThe conjugation of the targeted peptide CREKA and SPIOs was via linker sulfo-SMCC, while the dsDNA-Cy5.5 was modified on SPIOs through the conjugation between maleimide group in sulfo-SMCC and sulfydryl group in dsDNA-Cy5.5. SPIOs@A-T was characterised for its imaging properties, targeting ability and toxicity in vitro. Mice with metastatic lymph node (MLN) of breast cancer were established to evaluate the FMI and MPI imaging strategy in vivo. Healthy mice with normal lymph node (NLN) were used as control group. Histological examination and biosafety evaluation were performed for further assessment.ResultsAfter injection with SPIOs@A-T, the obvious high fluorescent intensity and MPI signal were observed in MLN group than those in NLN group. FMI can specifically light up MLN using an ATP-responsive fluorescence design. On the other hand, MPI could complement the limitation of imaging depth from FMI and could detect MLN more sensitively. Besides, the biosafety evaluation results showed SPIOs@A-T had no detectable biological toxicity.ConclusionSPIOs@A-T imaging probe in combination with FMI and MPI can provide a promising novel method for the precise detection of MLN in vivo.

Fluorescence Molecular Tomography is an optical imaging technique which aims at reconstructing the 3D distribution of fluorescent markers in bio-tissues based on surface measurements of emitted photons and a model of light propagation. The gold standard of accuracy in creating this light propagation model is the Monte Carlo method (MC), which simulates the path of photon packets through a discretized model of the tissue. One drawback of MC is the computational burden associated with its stochastic nature. Mesh based MC are computational implementations of MC techniques with favorable computational costs. Herein, we investigate the effects of locally refining a mesh discretization on reconstruction accuracy in mesh based Fluorescence Molecular Tomography. Using a mouse model created from μCT data and average murine optical properties, we are investigating the performances of mesh refinement strategies in reconstructing an 48.9 mm 3 fluorescence inclusion in the center of the model. Iterative mesh optimization is applied to the inverse problem in which after each reconstruction, the mesh is refined in the area of interest. Performance of the method is evaluated in terms of in volume and center of mass position of the inclusion compared to the ground truth. Our preliminary results indicate that accuracy improves with each refinement until convergence. Moreover, a method for rescaling analytically the forward model to fit each new mesh is also proposed in order to reduce the computational expense of the procedure while maintaining the improvements in accuracy

Fluorescence imaging has become an indispensable technique in cancer research because it can reveal informative molecular, cellular, anatomical, and functional insights. Development of advanced fluorescent probes with superior sensitivity and biological selectivity for fluorescence imaging is thus imperative. To move forward in this direction, we developed an easy self-assembly method for fabricating aptamer- anchored rubrene-loaded organic fluorescent nanoprobes. The aptamer-modified organic nanoprobes integrated the best features of the organic light-emitting materials and the aptamers, thus endowing them with excellent cell-targeting capability, high stability, and good biocompatibility. By using this general method, a variety of biocompatible and highly bright organic fluorescent nanoprobes based on novel organic light-emitting materials with specific recognition could be easily constructed for real-time biosensing and long-term biomedical imaging. © 2019 Chinese Chemical Society.

Fluorescence molecular tomography (FMT) is an important tool for life science, which can noninvasive real-time three-dimensional (3-D) visualization for fluorescence source location. FMT is widely used in tumor research due to its high-sensitive and low cost. However, the reconstruction of FMT is difficult. Although the reconstruction methods of FMT have developed rapidly in recent years, the morphological reconstruction of FMT is still a challenge problem. Thus, the purpose of this study is to realize the morphological reconstruction performance of FMT in glioma research. In this study, group sparsity was used as a new priori information for FMT. Besides sparsity, group sparsity also takes the group structure of the fluorescent sources, which can maintain the morphological information of the sources. Fused LASSO method (FLM) was proved it can efficiently model the group sparsity prior. Thus, we utilize FLM to reconstruct the morphological information of glioma. Furthermore, to reduce the influence of the high scattering of skull, we modified the FLM for improving the accuracy of morphological reconstruction. Glioma numerical simulation model and in vivo glioma model were established to evaluate the performance of morphological reconstruction of the proposed method. The results demonstrated that the proposed method was efficient to reconstruct the morphological information of glioma. Group sparsity priori can effectively improve the morphological accuracy of FMT reconstruction. Group sparsity can maintain the morphological information of fluorescent sources effectively, which has great application potential in FMT. The group sparsity based methods can realize the morphological reconstruction, which is of great practical significance in tumor research.

Mounting evidence points to dietary habits as an important determinant of health/disease prevention. Although the linkages with diet are intriguing, the literature is also laden with many inconsistencies. The reasons for these inconsistencies are likely multi-factorial, but probably reflect variation in the ability of bioactive constituents to reach or to influence a specific and critical molecular target(s). Knowledge about three types of biomarkers will assist in comparing the effectiveness of foods and drugs: (1) exposure (amount and time needed to bring about a response), (2) effect (amounts and activity of specific molecular target[s]) and (3) susceptibility determinants (agent-gene interactions or diet-drug interactions). As the era of molecular nutrition unfolds, a greater understanding of how foods and their components influence normal cellular process and ultimately health will surely arise. Knowledge about the molecular targets for bioactive food components may also help explain individuality in response to drugs. Such information will be critical in the development of effective tailored strategies for optimizing health. Keywords: Dietary, drugs, foods, genes, health, nutrigenomics, targets, omega-3, prebiotic, probiotic

PurposeLocal recurrence occurs in ~ 19% of sinonasal inverted papilloma (SNIP) surgeries and is strongly associated with incomplete resection. During surgery, it is technically challenging to visualize and resect all SNIP tissue in this anatomically complex area. Proteins that are overexpressed in SNIP, such as vascular endothelial growth factor (VEGF), may serve as a target for fluorescence molecular imaging to guide surgical removal of SNIP. A proof-of-concept study was performed to investigate if the VEGF-targeted near-infrared fluorescent tracer bevacizumab-800CW specifically localizes in SNIP and whether it could be used as a clinical tool to guide SNIP surgery.MethodsIn five patients diagnosed with SNIP, 10 mg of bevacizumab-800CW was intravenously administered 3 days prior to surgery. Fluorescence molecular imaging was performed in vivo during surgery and ex vivo during the processing of the surgical specimen. Fluorescence signals were correlated with final histopathology and VEGF-A immunohistochemistry. We introduced a fluorescence grid analysis to assess the fluorescence signal in individual tissue fragments, due to the nature of the surgical procedure (i.e., piecemeal resection) allowing the detection of small SNIP residues and location of the tracer ex vivo.ResultsIn all patients, fluorescence signal was detected in vivo during endoscopic SNIP surgery. Using ex vivo fluorescence grid analysis, we were able to correlate bevacizumab-800CW fluorescence of individual tissue fragments with final histopathology. Fluorescence grid analysis showed substantial variability in mean fluorescence intensity (FImean), with SNIP tissue showing a median FImean of 77.54 (IQR 50.47–112.30) compared to 35.99 (IQR 21.48–57.81) in uninvolved tissue (p < 0.0001), although the diagnostic ability was limited with an area under the curve of 0.78.ConclusionsA fluorescence grid analysis could serve as a valid method to evaluate fluorescence molecular imaging in piecemeal surgeries. As such, although substantial differences were observed in fluorescence intensities, VEGF-A may not be the ideal target for SNIP surgery.Trial registrationNCT03925285.

Heat shock protein 90 (Hsp90) is a molecular chaperone required for the stability and function of a number of conditionally activated and/or expressed signaling proteins, as well as multiple mutated, chimeric, or overexpressed signaling proteins, which promote cancer cell growth or survival or both. Hsp90 inhibitors, by interacting specifically with a single molecular target, cause the inactivation, destabilization, and eventual degradation of Hsp90 client proteins, and they have shown promising antitumor activity in preclinical model systems. One Hsp90 inhibitor, 17-AAG, has completed Phase I clinical trial, and several Phase II trials are in progress. Hsp90 inhibitors are unique in that, although they are directed towards a specific molecular target, they simultaneously inhibit multiple signaling pathways that frequently interact to promote cancer cell survival. Recently identified clients of Hsp90 participate, frequently in overlapping pathways, in mediating cancer cell survival. These include Akt, Her2, and HIF-1 alpha. Thus, by inhibiting multiple survival pathways used by cancer cells, combination of an Hsp90 inhibitor with standard chemotherapeutic agents may dramatically increase the in vivo efficacy of the standard agent. Furthermore, Hsp90 modulates androgen receptor activity and the activity of several mutated kinases characteristic of several leukemias and lymphomas, making Hsp90 inhibition an attractive modality in these cases. Hsp90 inhibitors may circumvent the characteristic genetic plasticity that has allowed cancer cells to eventually evade the toxic effects of most molecularly targeted agents. The mechanism-based use of Hsp90 inhibitors, both alone and in combination with other drugs, should augment the treatment of multiple forms of cancer.

The increasing use of mechanical thrombectomy in stroke management has opened the window to local intraarterial brain delivery of therapeutic agents. In this context, the use of nanomedicine could further improve the delivery of new treatments for specific brain targeting, tracking and guidance. In this study we take advantage of this new endovascular approach to deliver biocompatible poly(D-L-lactic-co-glycolic acid) (PLGA) nanocapsules functionalized with superparamagnetic iron oxide nanoparticles and Cy7.5 for magnetic targeting, magnetic resonance and fluorescent molecular imaging. A complete biodistribution study in naïve (n = 59) and ischemic (n = 51) mice receiving intravenous or intraarterial nanocapsules, with two different magnet devices and imaged from 30 min to 48 h, showed an extraordinary advantage of the intraarterial route for brain delivery with a specific improvement in cortical targeting when using a magnetic device in both control and ischemic conditions. Safety was evaluated in ischemic mice (n = 69) showing no signs of systemic toxicity nor increasing mortality, infarct lesions or hemorrhages. In conclusion, the challenging brain delivery of therapeutic nanomaterials could be efficiently and safely overcome with a controlled endovascular administration and magnetic targeting, which could be considered in the context of endovascular interventions for the delivery of multiple treatments for stroke.

Recently, attention has been focused on molecular targeted cancer therapy in various tumors. Although there is no single consistent molecular target specific for oral squamous cell carcinoma (OSCC) and salivary gland cancer (SGC), there are a number of promising candidate proteins. The aim of this review is to introduce the basic evidences to support the molecular targeting for OSCC and SGC. We focused on the 4 molecules, epidermal growth factor receptor (EGFR), cyclooxygenase-2 (COX-2), peroxisome proliferator-activated receptor gamma (PPARgamma), and progesterone receptor, that are, respectively, associated with the proliferation and the differentiation of OSCC and SGC. Gefitinib ("Iressa," ZD1839), a small molecule EGFR tyrosine kinase inhibitor, can inhibit the proliferation of OSCC cell lines in a dose- and time-dependent manner and lead to cell cycle arrest with accumulation of cells in the G1 phase, and a decrease of cells in S phase. The agent suppressed tumor metastasis in the animal model. Furthermore, a cooperative antiproliferative effect was obtained when cancer cells were treated with radiation followed by gefitinib. While radiation alone did not significantly affect p38 mitogen-activated protein kinase and MAP kinase kinase (MEK)1/2 autophosphorylation, the combination of gefitinib and radiation completely inhibited the downstream signaling of EGFR. Gefitinib enhanced tumor radioresponsiveness by multiple mechanisms, including the growth inhibition and effects on DNA repair after exposure to radiation. Next, the level of COX-2 expression correlated inversely with increased tumor radiation sensitivity. Treatment with celecoxib, a COX-2 selective inhibitor, enhanced the radioresponsiveness of HSC-2 cells, which constitutively expressed COX-2. Another promising molecular target is the PPARgamma, which is a member of the nuclear receptor superfamily of ligand-activated transcription factors. Recent studies have demonstrated that PPARgamma ligands induce cellular differentiation and inhibit cell growth in carcinomas of various types. These data suggest that synthetic PPARgamma ligands may be useful for molecular targeting of oral cancer. Finally, the possibility of using molecular targeted therapy directed at hormone receptors in the treatment of advanced SGCs was described. The basic data strongly suggested the possibility of tumor suppression by targeting these molecules. Studies of different targeted agents alone or with more conventional treatment modalities are needed to fully determine what role the targeted therapy will play in the management of patients with OSCC and SGC.

The solution of the forward problem in fluorescence molecular imaging strongly influences the successful convergence of the fluorophore reconstruction. The most common approach to meeting this problem has been to apply the diffusion approximation. However, this model is a first-order angular approximation of the radiative transfer equation, and thus is subject to some well-known limitations. This manuscript proposes a methodology that confronts these limitations by applying the radiative transfer equation in spatial regions in which the diffusion approximation gives decreased accuracy. The explicit integro differential equations that formulate this model were solved by applying the Galerkin finite element approximation. The required spatial discretization of the investigated domain was implemented through the Delaunay triangulation, while the azimuthal discretization scheme was used for the angular space. This model has been evaluated on two simulation geometries and the results were compared with results from an independent Monte Carlo method and the radiative transfer equation by calculating the absolute values of the relative errors between these models. The results show that the proposed forward solver can approximate the radiative transfer equation and the Monte Carlo method with better than 95% accuracy, while the accuracy of the diffusion approximation is approximately 10% lower.

Objective To investigate the property and the combination effect of the peptide specifically binding to human medullary breast cancer Bcap-37 cells by using phage display in vivo and to provide molecular targeting probe for early diagnosis of breast cancer. Methods The human medullary breast carcinoma Bcap-37 cells tumor-bearing nude mice model was prepared and three rounds in vivo were performed by using Ph.D.-C7CTM phage display peptide library. The distribution of screened phages in tumors and normal tissues was detected by using immunohistochemistry. The affinity of monoclonal phage to Bcap-37 cells was identified by using enzyme linked immunosorbent assay (ELISA). The positive monoclonal phage DNA was taken and sequenced, and the sequence with high repetition rate was selected to synthesize peptide by using chemical methods. Optical molecular probe was prepared and fluorescence molecular imaging was used to test its specificity and targeting ability for breast transplantation tumor of tumor-bearing nude mice in vivo. Results The recovery rate of phage in the third round screening in vivo was 107.2 times than that in the first round. Immunohistochemical results showed that the phages binding to the tumor tissues were increased successively with the increasing screening rounds in vivo. The number of phages binding to tumor tissues was more than that binding to normal tissues (lung, skeletal muscle, liver and kidney). The absorbancy (A) value of section scanning image in the tumor tissues was higher than that in the normal tissues, and the difference was statistically significant different (P < 0.05). ELISA results showed that 22 phages (affinity≥2) among the 50 randomly selected monoclonal phage were positive. After DNA sequencing analysis of the positive monoclonal phage, 4 repeat amino acid sequences were obtained. The fluorescein isothiocyanate-labelled (FITC)-CSPLNTRFC with the highest repetition rate was synthesized for FITC-CSPLNTRFC peptide. Bcap-37 cells tumor-bearing nude mice model assay in vivo showed that FITC-CSPLNTRFC peptide could significantly enriched in the breast xenograft tissues. Conclusion CSPLNTRFC peptide specifically binding to human medullary breast cancer Bcap-37 cells can be screened out successfully by using phage display in vivo, which will be helpful to vitro studies on the early diagnosis of breast cancer. Key words: Breast neoplasms; Peptide library; Phage display; Specifically binding peptide