Electrochemical fabrication of conducting polymer nanowires in an integrated microfluidic system.

In this paper, we introduce a new approach for the in situ electrochemical fabrication of an individually addressable array of conducting polymer nanowires (CPNWs) positioned within an integrated microfluidic device and also demonstrate that such an integrated device can be used as a chemical sensor immediately after its construction.

Electrolyte-gated transistors based on conducting polymer nanowire junction arrays.

In this study, we describe the electrolyte gating and doping effects of transistors based on conducting polymer nanowire electrode junction arrays in buffered aqueous media. Conducting polymer nanowires including polyaniline, polypyrrole, and poly(ethylenedioxythiophene) were investigated. In the presence of a positive gate bias, the device exhibits a large on/off current ratio of 978 for polyaniline nanowire-based transistors; these values vary according to the acidity of the gate medium.

Transgenic mouse for conditional, tissue-specific Cox-2 overexpression.

We constructed a cyclooxygenase-2 (Cox-2) conditional overexpression transgenic mouse (Cox-2 COE). The transgene contains a CAG promoter driving the Cox-2 and humanized Renilla luciferase (hRL) coding regions, linked by an internal ribosomal entry site. The promoter is followed by a loxP-flanked sequence containing enhanced green fluorescent protein (EGFP), a neomycin selection cassette, and a transcriptional/translational STOP sequence.

Effect of optical property estimation accuracy on tomographic bioluminescence imaging: simulation of a combined optical-PET (OPET) system.

Inevitable discrepancies between the mouse tissue optical properties assumed by an experimenter and the actual physiological values may affect the tomographic localization of bioluminescent sources. In a previous work, the simplifying assumption of optically homogeneous tissues led to inaccurate localization of deep sources. Improved results may be obtained if a mouse anatomical map is provided by a high-resolution imaging modality and optical properties are assigned to segmented tissues.

Monte carlo simulations of dose from microCT imaging procedures in a realistic mouse phantom.

The purpose of this work was to calculate radiation dose and its organ distribution in a realistic mouse phantom from micro-computed tomography (microCT) imaging protocols. CT dose was calculated using GATE and a voxelized, realistic phantom. The x-ray photon energy spectra used in simulations were precalculated with GATE and validated against previously published data.

Investigation of OPET Performance Using GATE, a Geant4-Based Simulation Software.

A combined optical positron emission tomography (OPET) system is capable of both optical and PET imaging in the same setting, and it can provide information/interpretation not possible in single-mode imaging. The scintillator array here serves the dual function of coupling the optical signal from bioluminescence/fluorescence to the photodetector and also of channeling optical scintillations from the gamma rays. We report simulation results of the PET part of OPET using GATE, a Geant4 simulation package.

Detector Concept for OPET-A Combined PET and Optical Imaging System.

The design of an imaging system capable of detecting both high-energy γ-rays and optical wavelength photons is underway at the UCLA Crump Institute for Molecular Imaging. This system, which we call optical PET (OPET), will be capable of non-invasively and repeatedly imaging small animal models in vivo for the presence of PET and optical signals. In this study, we describe the physical principles behind the operation of the OPET imaging system and discuss the design concept for one of the detector modules.

Readout of the Optical PET (OPET) Detector.

The design of an imaging system capable of detecting both high-energy γ-rays and optical wavelength photons is underway at the Crump Institute for Molecular Imaging. This system will noninvasively image small animal models in vivo for the presence of positron emission tomographic (PET) and optical signals. The detector will consist of modules of multichannel photomultiplier tubes (MC-PMT) coupled to arrays of scintillator crystals.

Noninvasive indirect imaging of vascular endothelial growth factor gene expression using bioluminescence imaging in living transgenic mice.

Vascular endothelial growth factor (VEGF) plays a critical role in the early activation of stromal tissues during wound healing and tumor growth. We report the use of a two-step transcriptional amplification (TSTA) approach to augment the transcriptional activity of the relatively weak VEGF promoter (pVEGF) using firefly luciferase (fl) reporter gene and bioluminescence imaging (BLI). In cell culture, we demonstrate that TSTA-based fl gene expression can be significantly enhanced over the direct one-step system.

Bioluminescence imaging of systemic tumor targeting using a prostate-specific lentiviral vector.

Developments in vector design using tissue-specific and tumor-specific promoters have led to significant improvements in tumor-targeting strategies. These developments combined with the ability to monitor gene expression by molecular imaging have facilitated the detection and prolonged monitoring of disease progression in small-animal models. Bioluminescence imaging offers a convenient and sensitive platform for monitoring gene expression patterns in preclinical models of gene therapy.

A method of image registration for small animal, multi-modality imaging.

Many research institutions have a full suite of preclinical tomographic scanners to answer biomedical questions in vivo. Routine multi-modality imaging requires robust registration of images generated by various tomographs. We have implemented a hardware registration method for preclinical imaging that is similar to that used in the combined positron emission tomography (PET)/computed tomography (CT) scanners in the clinic.

Tailoring antibodies for radionuclide delivery.

Therapeutic antibodies are well established as an important class of drugs in modern medicine. The exquisite specificity and affinity for a specific target offered by antibodies has also encouraged their development as delivery vehicles for agents such as radionuclides to target tissues, for radioimmunoimaging and radioimmunotherapy. Specifically, in nuclear medicine, radionuclide-conjugated antibody molecules make it possible to image diseased loci with greater sensitivity than other imaging modalities such as magnetic resonance imaging.

Instrumentation for molecular imaging in preclinical research: Micro-PET and Micro-SPECT.

Noninvasive imaging of molecular events and interactions in living small animal models has gained increasing importance in preclinical research. Two of the imaging modalities available for this research with potential for translation to the clinic are dedicated small animal positron emission tomography and single-photon emission computed tomography. This brief review introduces the fundamental principles behind these imaging technologies and instrumentation, and discusses the limitations in terms of their spatial resolution and sensitivity.

Small animal imaging center design: the facility at the UCLA Crump Institute for Molecular Imaging.

Purpose: The growing number of mouse and rat experiments, coupled with advances in small-animal imaging systems such as microPET, optical, microCAT, microMR, ultrasound and microSPECT, has necessitated a common technical center for imaging small animals.

Procedures: At the UCLA Crump Institute for Molecular Imaging, we have designed and built a facility to support the research interests of a wide range of investigators from multiple disciplines. Requirements to satisfy both research and regulatory oversight have been critically examined.

Novel fluorogenic substrates for imaging beta-lactamase gene expression.

A new class of small nonfluorescent fluorogenic substrates becomes brightly fluorescent after beta-lactamase hydrolysis with up to 153-fold enhancement in the fluorescence intensity. Less than 500 fM of beta-lactamase in cell lysates can be readily detected, and beta-lactamase expression in living cells can be imaged with a red fluorescence derivative. These new fluorogenic substrates should find uses in clinical diagnostics and facilitate the applications of beta-lactamase as a biosensor.

Tomographic bioluminescence imaging by use of a combined optical-PET (OPET) system: a computer simulation feasibility study.

The feasibility and limits in performing tomographic bioluminescence imaging with a combined optical-PET (OPET) system were explored by simulating its image formation process. A micro-MRI based virtual mouse phantom was assigned appropriate tissue optical properties to each of its segmented internal organs at wavelengths spanning the emission spectrum of the firefly luciferase at 37 degrees C. The TOAST finite-element code was employed to simulate the diffuse transport of photons emitted from bioluminescence sources in the mouse.

Synthesis of 4-(5-[18F]fluoromethyl-3-phenylisoxazol-4-yl)benzenesulfonamide, a new [18F]fluorinated analogue of valdecoxib, as a potential radiotracer for imaging cyclooxygenase-2 with positron emission tomography.

Fluoroalkyl and fluoroaryl analogues of valdecoxib were found to possess potent inhibitory activities against cyclooxygenase-2 comparable to that of the parent valdecoxib. Among them, the fluoromethyl analogue was chosen for 18F-labeling. Thus, 4-(5-[18F]fluoromethyl-3-phenylisoxazol-4-yl)benzenesulfonamide (approximately 2000 Ci/mmol at end of synthesis) was synthesized by [18F]fluoride-ion displacement of the corresponding tosylate in approximately 40% decay-corrected radiochemical yield within approximately 120 min from end of bombardment.

Arming antibodies: prospects and challenges for immunoconjugates.

Immunoconjugates--monoclonal antibodies (mAbs) coupled to highly toxic agents, including radioisotopes and toxic drugs (ineffective when administered systemically alone)--are becoming a significant component of anticancer treatments. By combining the exquisite targeting specificity of mAbs with the enhanced tumor-killing power of toxic effector molecules, immunoconjugates permit sensitive discrimination between target and normal tissue, resulting in fewer toxic side effects than most conventional chemotherapeutic drugs. Two radioimmunoconjugates, ibritumomab tiuxetan (Zevalin) and tositumomab-131I (Bexxar), and one drug conjugate, gemtuzumab ozogamicin (Mylotarg), are now on the market.

Optimizing radiolabeled engineered anti-p185HER2 antibody fragments for in vivo imaging.

We have recently described the in vivo properties of an iodinated anti-p185HER2 engineered antibody fragment [minibody (scFv-C(H)3)2; 80 kDa], made from the internalizing 10H8 monoclonal antibody. Although the 10H8 minibody showed excellent binding to the target in vitro, only modest tumor uptake [5.6 +/- 1.

Non-invasive imaging of a transgenic mouse model using a prostate-specific two-step transcriptional amplification strategy.

Non-invasive assessment of transgenic animals using bioluminescence imaging offers a rapid means of evaluating disease progression in animal models of disease. One of the challenges in the field is to develop models with robust expression to image repetitively live intact animals through solid tissues. The prostate-specific antigen (PSA) promoter is an attractive model for studying gene regulation due to its hormonal response and tissue-specificity permitting us to measure signaling events that occur within the native tissues.

Attenuation correction for small animal PET tomographs.

Attenuation correction is one of the important corrections required for quantitative positron emission tomography (PET). This work will compare the quantitative accuracy of attenuation correction using a simple global scale factor with traditional transmission-based methods acquired either with a small animal PET or a small animal x-ray computed tomography (CT) scanner. Two phantoms (one mouse-sized and one rat-sized) and two animal subjects (one mouse and one rat) were scanned in CTI Concorde Microsystem's microPET Focus for emission and transmission data and in ImTek's MicroCAT II for transmission data.

Noninvasive monitoring of target gene expression by imaging reporter gene expression in living animals using improved bicistronic vectors.

Unlabelled: Indirect, noninvasive imaging of therapeutic gene expression based on levels of reporter gene expression is a powerful tool to devise improved therapeutic strategies in cancer gene therapy. The use of bicistronic vectors carrying internal ribosome entry sites (IRESs) allows the coexpression of multiple gene products from the same promoter but leads to considerable attenuation of the downstream gene. In this study, we describe the use of 10 linked copies of the Gtx (homeodomain protein) IRES (abbreviated as SIRES) in place of the encephalomyocarditis (EMCV) IRES in mediating downstream reporter gene expression in cell culture and in vivo.

Cryoelectron microscopy imaging of recombinant and tissue derived vaults: localization of the MVP N termini and VPARP.

The vault is a highly conserved ribonucleoprotein particle found in all higher eukaryotes. It has a barrel-shaped structure and is composed of the major vault protein (MVP); vault poly(ADP-ribose) polymerase (VPARP); telomerase-associated protein 1 (TEP1); and small untranslated RNA (vRNA). Although its strong conservation and high abundance indicate an important cellular role, the function of the vault is unknown.

A tracer kinetic model for 18F-FHBG for quantitating herpes simplex virus type 1 thymidine kinase reporter gene expression in living animals using PET.

Unlabelled: Reporter probe 9-(4-18F-fluoro-3-[hydroxymethyl]butyl)guanine (18F-FHBG) and reporter gene mutant herpes simplex virus type 1 thymidine kinase (HSV1-sr39tk) have been used for imaging reporter gene expression with PET. Current methods for quantitating the images using the percentage injected dose per gram of tissue do not distinguish between the effects of probe transport and subsequent phosphorylation. We therefore investigated tracer kinetic models for 18F-FHBG dynamic microPET data and noninvasive methods for determining blood time-activity curves in an adenoviral gene delivery model in mice.