Veera Arora

Gold nanotags for combined multi-colored Raman spectroscopy and x-ray computed tomography

Multi-color gold-nanoparticle-based tags (nanotags) are synthesized for combined surface-enhanced Raman spectroscopy (SERS) and x-ray computed tomography (CT). The nanotags are synthesized with quasi-spherical gold nanoparticles encoded with a reporter dye (color), each with a unique Raman spectrum. A library of nanotags with six different colors were synthesized for a range of gold nanoparticle sizes and an optimum size has been established to yield the largest SERS intensity and x-ray attenuation that is higher than the iodinated CT contrast agents used in clinics. Proof-of-principle in vivo imaging results with nanotags are presented that, for the first time, demonstrates the combined in vivo dual modality imaging capability of SERS and CT with a single nanoparticle probe.

Development of novel 19F NMR pH indicators: Synthesis and evaluation of a series of fluorinated vitamin B6 analogues

We have synthesized a series of novel fluorinated vitamin B6 analogues (6-fluoropyridoxol derivatives) as potential 19F NMR pH indicators for use in vivo. Modifications included addition of aldehyde, carboxyl or aminomethyl groups at the 4- or 5-ring position, and examination of a trifluoromethyl moiety as an internal chemical shift standard. The variation in chemical shift with respect to acid-base titration showed pKa values in the range 7.05-9.5 with a chemical shift sensitivity in the range 7.4-12 ppm. Several of the molecules readily cross cell membranes providing estimates of both intra- and extra-cellular pH in whole blood. 6-Fluoropyridoxamine (6-FPAM) exhibits a pKa = 7.05, which is closer to normal physiological pH than the parent molecule 6-fluoropyridoxol (6-FPOL) (pKa = 8.2), and should thus, be useful for precise and accurate measurements of pH in vivo. Enhanced spectral resolution for 6-FPAM over 6-FPOL is demonstrated in whole blood and the perfused rat heart.

Nanoparticulate Radiolabelled Quinolines Detect Amyloid Plaques in Mouse Models of Alzheimer's Disease

Detecting aggregated amyloid peptides (Aβ plaques) presents targets for developing biomarkers of Alzheimers disease (AD). Polymeric n-butyl-2-cyanoacrylate (PBCA) nanoparticles (NPs) were encapsulated with radiolabelled amyloid affinity 125I-clioquinol (CQ, 5-chloro-7-iodo-8-hydroxyquinoline) as in vivo probes. 125I-CQ-PBCA NPs crossed the BBB (2.3 ± 0.9 ID/g) (P < .05) in the WT mouse (N = 210), compared to 125I-CQ (1.0 ± 0.4 ID/g). 125I-CQ-PBCA NP brain uptake increased in AD transgenic mice (APP/PS1) versus WT (N = 38; 2.54 × 105 ± 5.31 × 104 DLU/mm2; versus 1.98 × 105 ± 2.22 × 104 DLU/mm2) and in APP/PS1/Tau. Brain increases were in mice intracranially injected with aggregated Aβ 42 peptide (N = 17; 7.19 × 105 ± 1.25 × 105 DLU/mm2), versus WT (6.07 × 105 ± 7.47 × 104 DLU/mm2). Storage phosphor imaging and histopathological staining of the plaques, Fe2+ and Cu2+, validated results. 125I-CQ-PBCA NPs have specificity for Aβ in vitro and in vivo and are promising as in vivo SPECT (123I), or PET (124I) amyloid imaging agents.

B6 Strain Ly49I Inhibitory Gene Expression on T Cells in FVB.Ly49IB6 Transgenic Mice Fails to Prevent Normal T Cell Functions

Inhibitory Ly49 receptors expressed on NK cells provide a mechanism for tolerance to normal self tissues. The immunoregulatory tyrosine-based inhibitory motifs present in some Ly49s are able to transmit an inhibitory signal upon ligation by MHC class I ligands. In our system, as well as others, mice transgenic for inhibitory Ly49 receptors express these receptors on both NK and T cells. FVB (H2q) mice transgenic for the B6 strain Ly49I (Ly49IB6) express the inhibitory Ly49 receptor on the surface of both T and NK cells. Although Ly49I functions to prevent NK-mediated rejection of H2b donor bone marrow cells in this transgenic mouse strain, the T cells do not appear to be affected by the expression of the Ly49I transgene. FVB.Ly49I T cells have normal proliferative capabilities both in vitro and in vivo in response to the Ly49I ligand, H2b. In vivo functional T cell assays were also done, showing that transgenic T cells were not functionally affected. T cells in these mice also appear to undergo normal T cell development and activation. Only upon stimulation with suboptimal doses of anti-CD3 in the presence of anti-Ly49I is T cell proliferation inhibited. These data are in contrast with findings in Ly49A, and Ly49G2 receptor transgenic models. Perhaps Ly49I-H2b interactions are weaker or of lower avidity than Ly49A-H-2Dd interactions, especially in T cells.

Feature Article: Polymeric Nanoparticulate Drug Delivery Through The Blood Brain Barrier

Abstract Alzheimers disease (AD) is the most common cause of dementia among the elderly, affecting 5% of Americans over age 65, and 20% over age 80. An excess of senile plaques (β-amyloid protein) and neurofibrillary tangles (tau protein), ventricular enlargement, and cortical atrophy characterizes it. Unfortunately, targeted drug delivery to the Central Nervous System (CNS), for the therapeutic advancement of neurodegenerative disorders such as Alzheimers, is complicated by restrictive mechanisms imposed at the blood brain barrier (BBB). Opsonization by plasma proteins in the systemic circulation is an additional impediment to cerebral drug delivery. Here, we attempt to show that biodegradable polymeric nanoparticles (NPs) with appropriate surface modifications can deliver drugs of interest beyond the BBB for diagnostic and therapeutic applications, thus allowing the study of neurological disorders. Particularly, the radiolabelled Cu2+ or Fe3+ metal chelator Clioquinol (CQ), which has a high affinity f...

A new F-18 labeled PET agent for imaging Alzheimer's plaques

Amyloid plaques and neurofibrillary tangles are hallmarks of Alzheimer’s disease (AD). Advances in development of imaging agents have focused on targeting amyloid plaques. Notable success has been the development of C‐11 labeled PIB (Pittsburgh Compound) and a number of studies have demonstrated the utility of this agent. However, the short half life of C‐11 (t1/2: 20 min), is a limitation, thus has prompted the development of F‐18 labeled agents. Most of these agents are derivatives of amyloid binding dyes; Congo red and Thioflavin. Some of these agents are in clinical trials with encouraging results. We have been exploring new class of agents based on 8‐hydroxy quinoline, a weak metal chelator, targeting elevated levels of metals in plaques. Iodine‐123 labeled clioquinol showed affinity for amyloid plaques however, it had limited brain uptake and was not successful in imaging in intact animals and humans. We have been successful in synthesizing F‐18 labeled 8‐hydroxy quinoline. Small animal PET/CT imagi...

PET imaging of Alzheimer's disease (AD) transgenic mice with F-18 labeled 8-hydroxy quinoline

and no distal cues, or (2) hippocampal-based spatial MWM with hidden platform and distal visual cues. Performance was assessed using escape latencies and probe trial parameters. Ten days post-training, mice were transcardially perfused. Brains within intact skulls were post-fixed and imaged using highresolution (32 micron isotropic) T2-weighted MRI at 7T. Deformation-based morphometry (DBM) was used to identify focal volume changes correlated with cognitive task performance using a general linear model (Lerch et al, 2008). Results: All mice undergoing the non-spatial MWM performed equally well. Focal volume increase associated with non-spatial MWM was observed in the striatum. On spatial MWM, APP mice displayed significantly prolonged escape latencies to reach the hidden platform compared to WT. Pioglitazone-treated APP mice exhibited a trend for reduced latencies during training, and a slightly higher number of platform-crossings than untreated APP mice during probe trial. Focal volume increase associated with spatial MWM performance was observed in the hippocampus in WT mice and treated APP mice, but not in untreated APP mice. Conclusions: We have demonstrated using high resolution MRI and DBM that spatial learning-induced hippocampal brain plasticity is absent in young APP mice. Pioglitazone-treatment in young APP mice had beneficial effects on focal hippocampal volume growth associated with spatial MWM performance, and completely rescued cerebrovascular function, suggesting that early and continued pioglitazone treatment may slow AD progression.

Imaging Lung Clearance of Radiolabeled Tumor Cells to Study Mice with Normal, Activated or Depleted Natural Killer (NK) Cells

Lung clearance of 51CR and 125I iododeoxyuridine (IUDR) labeled cancer cells assess NK cell activity. It is desirable to develop noninvasive imaging technique to assess NK activity in mice. We labeled target YAC‐1 tumor cells with 125I, 111In, 99mTc, or 67Ga and injected I.V. into three groups of BALB/c mice. Animals were treated with medium (group I), 300mg/kg cyclophosmamide (CY) to kill NK cell (group II), or anti‐LY49C/1) (ab’)2 mAb to augment NK function (group III). Lungs were removed 15 min or 2 h later for tissue counting. Control and treated mice were imaged every 5 min with a scintillating camera for 1 h after 15 min of infusion of the 111In labeled cells. Lung clearance increased after 15 min (lodging: 60–80%) and (2 h retention: 3–7%). Similar results were obtained with all the isotopes studied. Images distinguished the control and treated mice for lung activity. Cells labeled with 111In, 99mTc or 67Ga are cleared similar to those labeled with 51Cr or 125I. NK cell destruction of tumor cells m...