Potent Acetylcholinesterase Selective and Reversible Homodimeric Agent Based on Tacrine for Theranostics.

Acetylcholinesterase (AChE) has been an important biomarker for diagnosing Alzheimer's disease (AD), due to reduction in AChE activity in post-mortem brains of AD patients. A potent, selective, and reversible homodimeric inhibitor of AChE, 5-amino- N1, N3-bis(2-(1,2,3,4-tetrahydroacridin-9-ylamino)ethyl)isophthalamide (compound 4), was synthesized by using 9-alkyl(1,2,3,4-tetrahydroacridine) pharmacophore with appended functionality. In the present work, we report the synthesis of this bivalent inhibitor of AChE. The homodimeric ligand structure was designed and studied with molecular docking tools, which revealed its high affinity and interactions with active site gorge of AChE, which includes both catalytic active site (CAS) and peripheral active site (PAS). The IC50 value of this bivalent inhibitor for AChE and BuChE were 0.54 ± 0.06 and 32.49 ± 1.2 nM, respectively, with a selectivity ratio of 60.16 toward AChE. The designed ligand also showed potent inhibitory properties on PAS activity as well as on AChE-induced amyloid aggregation with low cytotoxicity on rat hippocampal neurons. The AFM images further corroborated the Aß1-42 aggregation inhibition by compound 4 to an extent similar to bis(7)-tacrine. Moreover, the bivalent ligand was also proven to be of neurogenic potential due to its ability to induce S-phase post-treatment in rat hippocampal neuronal cells. On the basis of initial results, the agent could be further explored for its theranostic value clinically, which gives the possibility of tracing the AChE levels by molecular imaging techniques in correlation with progression of neurocognitive disorders like AD for better therapy response and patient management.

New Trends and Current Status of Positron-Emission Tomography and Single-Photon-Emission Computerized Tomography Radioligands for Neuronal Serotonin Receptors and Serotonin Transporter.

The critical role of serotonin (5-hydroxytryptamine; 5-HT) and its receptors (5-HTRs) in the pathophysiology of diverse neuropsychiatric and neurodegenerative disorders render them attractive diagnostic and therapeutic targets for brain disorders. Therefore, the in vivo assessment of binding of 5-HT receptor ligands under a multitude of physiologic and pathologic scenarios may support more-accurate identification of disease and its progression and the patient's response to therapy as well as the screening of novel therapeutic strategies. The present Review aims to focus on the current status of radioligands used for positron-emission tomography (PET) and single-photon-emission computerized tomography (SPECT) imaging of human brain serotonin receptors. We further elaborate upon and emphasize the attributes that qualify a radioligand for theranostics on the basis of its frequency of use in clinics, its benefit to risk assessment in humans, and its continuous evolution, along with the major limitations.

Biotinidase Resistant 68Gallium-Radioligand Based on Biotin/Avidin Interaction for Pretargeting: Synthesis and Preclinical Evaluation.

A new macrocyclic system 2,2'-(12-amino-11,13-dioxo-1,4,7,10-tetraazacyclotridecane-4,7-diyl)diacetic acid (ATRIDAT) was designed for coordinating metals in +2 and +3 oxidation states particularly 68Ga(III), for PET imaging. ATRIDAT was conjugated to d-biotin for pretargeting via biotin-avidin interaction. This model provides high tumor targeting efficiency and stability to biotinidase activity leading to modest signal amplification at the tumor site. Cyclization of triethylenetetramine with protected diethylamino malonate resulted in the formation of 13 membered diamide ring. d-Biotin was then anchored on the pendant amine rendering α-methyne carbon to the biotinamide bond which blocks the biotinidase enzyme activity. Biotinidase stability assay showed remarkable stability toward the action of biotinidase with ∼95% remaining intact after treatment following 4 h. Binding affinity experiments such as HABA assay, competitive displacement studies with d-biotin and CD showed high binding affinity of the molecule with avidin in nanomolar range. Biotin conjugate was successfully radiolabeled with 68Ga(III) with radiolabeling efficiency of ∼70% and then purified to get 99.9% radiochemical yield. IC50 of the compound was found to be 2.36 mM in HEK cell line and 0.82 mM in A549 as assessed in MTT assay. In biodistribution studies, the major route of excretion was found to be renal. Significant uptake of 4.15 ± 0.35% was observed in tumor in the avidin pretreated mouse at 1 h. µPET images also showed a high tumor to muscle ratio of 26.8 and tumor to kidney ratio of 1.74 at 1 h post-injection after avidin treatment.

Evaluating the Diagnostic Efficacy of 99mTc-Methionine Single-Photon Emission Computed Tomography-Computed Tomography: A Head-to-Head Comparison with 11C-Methionine Positron Emission Tomography-Magnetic Resonance Imaging in Glioma Patients.

Background: Amino acid positron emission tomography (PET) imaging plays a significant role in the diagnosis of gliomas and in differentiating tumor recurrence from necrosis. In this study, the authors evaluated the diagnostic efficacy of [99mTc]Tc-methionine single-photon emission computed tomography-computed tomography (SPECT-CT) in comparison with [11C]methionine PET-magnetic resonance imaging (MRI) in delineating tumors. Methods: Thirty-one (primary: 16 and postoperative: 15) patients of confirmed (either MRI or histopathological proven) glioma underwent both [99mTc]Tc-methionine SPECT-CT and [11C]methionine PET-MRI. A comparative analysis was performed between SPECT, PET, and MR images to calculate the concordance between the modalities and to evaluate the diagnostic efficacy of the [99mTc]Tc-methionine SPECT. Results: [99mTc]Tc-methionine SPECT showed comparable uptake in the tumor lesions in comparison to [11C]methionine PET. A significant and strong positive correlation was observed between the volume of tumor (Vt) in PET and Vt MR (p < 0.004). Likewise, a significant and strong positive correlation was found between Vt SPECT and Vt MR. [99mTc]-methionine has a sensitivity and specificity of 91% and 75%, respectively, compared with 82% and 100% for [11C]methionine in postoperative cases to differentiate the tumor recurrence from necrosis. The sensitivity and specificity of [99mTc]Tc-methionine was 92% and 100%, respectively, compared with 92% and 67% for [11C]methionine in primary tumors. Conclusion: [99mTc]Tc-methionine SPECT-CT is as equally good as [11C]methionine for diagnosing and differentiating it from necrosis especially in high-grade glioma.

Radiolabelled folate micellar carriers as proposed diagnostic aid for CNS tumors by nasal route.

Glioma refers to the most atypical variant of the malignant central nervous system tumors posturing massive challenge to the research fraternity owing to the flimsy improvement in the patient survival rate over the past years. The aim of the proposed work was developing a diagnostic aid for brain tumors, which could be administered via the non-invasive intranasal route. Since overexpression of folate receptors in the central nervous system tumors is 500 times more than the normal healthy cells, we aimed at fabricating a radiolabeled folate encapsulated micellar delivery system to be given via the nasal route. Folate conjugated bifunctional chelating agent was synthesized, radiolabeled with 99mTc, and encapsulated in a micellar carrier. The fabricated micelles were further evaluated for in vivo nasal toxicity in rats and the same were found safe for intranasal administration. The fabricated micelles owing to their nano size, mucoadhesive nature, and enhanced permeation were observed to have a higher uptake into the brain (around 16% in 4 h) than as compared to the radiolabeled conjugated folate solution when studied for in vivo biodistribution in mice. Single-photon emission computerized tomography imaging performed in higher animals upon intranasal administration of the micellar formulation revealed enhanced uptake of the micelles into the animal brain. It is believed that the aforementioned formulation can be of a great diagnostic value in the detection of not only brain tumors but also other folate expressing cancers such as cervical, breast, and lungs as the system is fast, non-toxic, accurate, non-invasive, and simple.

Preclinical and Clinical Use of Indigenously Developed 99mTc-Diethylenetriaminepentaacetic Acid-Bis-Methionine: l-Type Amino Acid Transporter 1-Targeted Single Photon Emission Computed Tomography Radiotracer for Glioma Management.

A new era in tumor classification, diagnosis, and prognostic evaluation has begun as a consequence of recent developments in the molecular and genetic characterization of central nervous system tumors. In this newly emerging era, molecular imaging modalities are essential for preoperative diagnosis, surgical planning, targeted treatment, and post-therapy evaluation of gliomas. The radiotracers are able to identify brain tumors, distinguish between low- and high-grade lesions, confirm a patient's eligibility for theranostics, and assess post-radiation alterations. We previously synthesized and reported the novel l-type amino acid transporter 1 (LAT-1)-targeted amino acid derivative in light of the use of amino acid derivatives in imaging technologies. Further, we have developed a single vial ready to label Tc-lyophilized kit preparations of diethylenetriaminepentaacetic acid-bis-methionine [DTPA-bis(Met)], also referred to as methionine-diethylenetriaminepentaacetic acid-methionine (MDM) and evaluated its imaging potential in numerous clinical studies. This review summarizes our previous publications on 99mTc-DTPA-bis(Met) in different clinical studies such as detection of breast cancer, as a prognostic marker, in detection of recurrent/residual gliomas, for differentiation of recurrent/residual gliomas from radiation necrosis, and for comparison of 99mTc-DTPA-bis(Met) with 11C-L-methionine (11C-MET), with relevant literature on imaging modalities in glioma management.

Preparation and biological evaluation of paclitaxel loaded biodegradable PCL/PEG nanoparticles for the treatment of human neuroendocrine pancreatic tumor in mice.

The main aim of this study was to develop and evaluate nanoparticulate system of paclitaxel loaded polymeric biodegradable Poly (ε-caprolactone) nanoparticles for targeting to neuroendocrine pancreatic tumors in mice. Nanoparticles were prepared by simple emulsion technique having surface modification with pluronic F-68. All formulations were evaluated for particle shape and size, zeta potential, encapsulation efficiency and in vitro drug release. Radiolabelling of nanoparticles with (99m)Tc was done for scintigraphy and biodistribution studies. Cytotoxicity studies were performed on BON-1 cell line using MTT cell proliferation assay. The in vivo tumor inhibition study was performed after i.v. administration of paclitaxel nanoparticles. Our results showed that optimized nanoformulation was found to have size range from 100 ± 0.03 nm to 250 ± 0.06 nm with smooth spherical shape. Negative zeta potential value confirmed the surface modification and stability of nanoformulations. The amount of drug released after 24h from the formulation was found to be 73.3% ± 2.7%. More pronounced cytotoxicity was found with nanoparticulate formulation as compared with paclitaxel. The PCL-Ptx nanoparticles reduced tumor volume significantly in comparison with paclitaxel. Higher concentration of Ptx-NPs were found in tumor which was also revealed by high quality scintigraphic image of BON-1 tumor bearing mouse model. In conclusion, polymeric nanoparticulate formulation of paclitaxel was very much efficient for chemotherapy of human pancreatic neuroendocrine tumor in mice.

Sustained Activity of Stimuli-Responsive Curcumin and Acemannan Based Hydrogel Patches in Wound Healing.

Natural plant extract, namely acemannan (Ac) and curcumin (Cur), coencapsulated pluronic micelles, showing thermoresponsive properties, were designed for efficient and safe in vivo wound healing applications. Ac and Cur, widely used antimicrobials, find limited applications because of their low stability, short biological half-life, poor solubility, and low bioavailability. Herein, we report the extraction of Ac from aloe vera and coencapsulation of it with Cur in pluronic micelles to take advantage of the combined effects of both components. Both Ac and Cur preserved their bioactive functionality upon encapsulation. Single photon emission computed tomography imaging confirmed that NPAcC2 hydrogel masked the whole wound by forming a layer. Cur and Ac synergistically resulted in rapid wound closure on the seventh day, and full-grown hair was observed on the 10th day. Individually they both take more than 20 days for wound closure. The increase in the concentration of curcumin increases the healing properties of the material. For days 1, 6, and 10 of the wound dressing experiment, the percentages of wound closure of the mice were the highest for NPAcC2 (i.e., 100%) compared to the untreated control (25%) while maintaining the integrity of the skin. These natural product-based hydrogels have limited side effects vs those caused by commercial drugs in wound healing.

[99mTc]Tc-DTPA-Bis(cholineethylamine) as an Oncologic Tracer for the Detection of Choline Transporter (ChT) and Choline Kinase (ChK) Expression in Cancer.

OBJECTIVE: The elevated choline transporters (ChT), choline kinase (ChK), choline uptake, and phosphorylation in certain tumor cells have influenced the development of radiolabeled choline derivatives as diagnostic probes for imaging cell membrane proliferation. We, therefore, aimed to develop a choline-based moiety for imaging choline kinase-overexpressed tumors by single-photon emission tomography (SPECT). A novel choline-based diagnostic probe was synthesized and evaluated preclinically in various ChT- and ChK-overexpressed tumor models for SPECT imaging applications. METHODS: The synthesis of diethylenetriaminepentaacetic acid-bis-choline ethylamine [DTPA-bis(ChoEA)] featured the conjugation of dimethylaminoethanol to a bifunctional chelator DTPA anhydride. [99mTc]Tc-DTPA-bis(ChoEA) was prepared, and its in vivo characteristics were evaluated in BALB/c mice and tumor-xenografted PC3, A549, and HCT116 athymic mouse models. The in vitro parameters, including cell binding and cytotoxicity, were assessed in PC3, A549, and HCT116 cell lines. To evaluate the specificity of the radioprobe, competitive binding studies were performed. Small-animal SPECT/CT diagnostic imaging was performed for in vivo evaluation. The mouse biodistribution data was further investigated to estimate the radiation dose in humans. RESULTS: In silico studies suggested high binding with enhanced specificity. A standard radiolabeling procedure using stannous chloride as a reducing agent showed a labeling yield of 99.5 ± 0.5%. The in silico studies suggested high binding with enhanced specificity. [99mTc]Tc-DTPA-bis(ChoEA) showed high in vitro stability and specificity. The pharmacokinetic studies of [99mTc]Tc-DTPA-bis(ChoEA) in mice showed an increased tumor-to-background ratio after few minutes of intravenous administration. The first-in-human trial was also conducted. The effective dose was estimated to be 0.00467 mSv/MBq (4.67 mSv/GBq), resulting in a radiation dose of up to 1.73 mSv for the 370 MBq injection of [99mTc]Tc-DTPA-bis(ChoEA). CONCLUSIONS: The synthesized radioprobe [99mTc]Tc-DTPA-bis(ChoEA) accumulates specifically in choline kinase-overexpressed tumors with a high signal-to-noise ratio. The preclinical and first-in-man data suggested that [99mTc]Tc-DTPA-bis(ChoEA) could potentially be used as a diagnostic SPECT tracer in the monitoring and staging of cancer.

DMA, a Small Molecule, Increases Median Survival and Reduces Radiation-Induced Xerostomia via the Activation of the ERK1/2 Pathway in Oral Squamous Cell Carcinoma.

Survival, recurrence, and xerostomia are considerable problems in the treatment of oral squamous carcinoma patients. In this study, we investigated the role of DMA (5-(4-methylpiperazin-1-yl)-2-[2'-(3,4-dimethoxyphenyl)5″benzimidazoyl]benzimidazole) as a salivary gland cytoprotectant in a patient-derived xenograft mouse model. A significant increase in saliva secretion was observed in the DMA-treated xenograft compared to radiation alone. Repeated doses of DMA with a high dose of radiation showed a synergistic effect on mice survival and reduced tumor growth. The mean survival rate of tumor-bearing mice was significantly enhanced. The increased number of Ki-67-stained cells in the spleen, intestine, and lungs compared to the tumor suggests DMA ablates the tumor but protects other organs. The expression of aquaporin-5 was restored in tumor-bearing mice injected with DMA before irradiation. The reduced expression of αvß3 integrin and CD44 in DMA alone and DMA with radiation-treated mice suggests a reduced migration of cells and stemness of cancer cells. DMA along with radiation treatment results in the activation of the Ras/Raf/MEK/ERK pathway in the tumor, leading to apoptosis through caspase upregulation. In conclusion, DMA has strong potential for use as an adjuvant in radiotherapy in OSCC patients.

Synthesis of specific SPECT-radiopharmaceutical for tumor imaging based on methionine: 99mTc-DTPA-bis(methionine).

Methionine-diethylenetriaminepentaaceticacid-methionine [DTPA-bis(Met)] was synthesized by covalently conjugating two molecules of methionine (Met) to DTPA and was labeled with (99m)Tc in high radiochemical purity and specific activity (166-296 MBq/micromol). Kinetic analysis showed K(m) of 12.95 +/- 3.8 nM and a maximal transport rate velocity (V(max)) of 80.35 +/- 0.42 pmol microg protein(-1) min(-1) of (99m)Tc-DTPA-bis(Met) in U-87MG cells. DTPA-bis(Met) had dissociation constants (K(d)) of 0.067 and 0.077 nM in U-87MG and BMG, respectively. (35)S-methionine efflux was trans-stimulated by (99m)Tc-labeled DTPA conjugate demonstrating concentrative transport. The blood kinetic studies showed fast clearance with t(1/2) (F) = 36 +/- 0.5 min and t(1/2) (S) = 5 h 55 min +/- 0.85 min. U-87MG and BMG tumors saturated at approximately 2000 +/- 280 nmol/kg of (99m)Tc-DTPA-bis(Met). Initial rate of transport of (99m)Tc-DTPA-bis(Met) in U-87MG tumor was found to be 4.68 x 10(-4) micromol/kg/min. The tumor (BMG cell line, malignant glioma) grafted in athymic mice were readily identifiable in the gamma images. Semiquantitative analysis from region of interest (ROI) placed over areas counting average counts per pixel with maximum radiotracer uptake on the tumor was found to be 11.05 +/- 3.99 and compared ROI with muscle (0.55 +/- 0.13). The tumor-to-contralateral muscle tissue ratio of (99m)Tc-DTPA-bis(Met) was found to be 23 +/- 3.3. Biodistribution revealed significant tumor uptake and good contrast in the U-87MG, BMG, and EAT tumor-bearing mice. In clinical trials, the sensitivity, specificity, and positive predictive values were found to be 87.8%, 92.8%, and 96.6%, respectively. (99m)Tc-DTPA-bis(Met) showed excellent tumor targeting and has promising utility as a SPECT-radiopharmaceutical for imaging methionine-dependent human tumors and to quantify the ratio of MET(+)/HCY(-).

Microenvironment Stimulated Bioresponsive Small Molecule Carriers for Radiopharmaceuticals.

The widespread and successful use of radiopharmaceuticals in diagnosis, treatment, and therapeutic monitoring of cancer and other ailments has spawned significant literature. The transition from untargeted to targeted radiopharmaceuticals reflects the various stages of design and development. Targeted radiopharmaceuticals bind to specific biomarkers, get fixed, and highlight the disease site. A new subset of radioprobes, the bioresponsive radiopharmaceuticals, has been developed in recent years. These probes generally benefit from signal enhancement after undergoing molecular changes due to the fluctuations in the environment (pH, redox, or enzymatic activity) at the site of interest. This review presents a comprehensive overview of bioresponsive radioimaging probes covering the basis, application, and scope of development.

Radioprotective efficacy of GSH based peptidomimetic complex of manganese against radiation induced damage: DT(GS)2Mn(II).

The adverse effects of ionizing radiation (IR) on biological tissues are mediated via increased production of reactive oxygen species (ROS) often resulting in life-threatening injuries. The effects of ionizing radiation on cells include the formation of ROS, DNA single-strand breaks, double-strand breaks, and extensive base modifications inducing the complex DNA damage. The capacity to endure the radiation insult lies in the biochemical mechanisms and structural properties in many bacterial species such as Deinococcus radiodurans and Thermococcus radiotolerans. In addition, a mechanistic link has established between the presence and accumulation of short peptides and Mn2+ in the protection of bacteria (Deinococcus radiodurans) from the harmful ionizing radiation. This paradigm has opened up novel avenues of radioprotection in diverse settings and systems for human application. We hereby report a new bifunctional system that comprises of thiol groups in the form of Glutathione (GSH), and manganese to mimic the above system for radioprotection. The present study, therefore, adopts a novel approach to use GSH complexed Mn, and this conjugated system is complying with the prerequisite for radioprotection as seen in the above mechanism. This unique conjugate DT(GS)2Mn(II) was evaluated for its efficacy invitro and invivo. Radioprotective efficacy of DT(GS)2Mn(II) on NIH/3T3 cells revealed that compound could significantly protect cells against radiation-induced toxicity as compared to the standard compound N-acetyl cysteine. Pre-treatment of DT(GS)2Mn(II) increased the survival of mice by 50% compared to radiation alone treatment group. A significant decrease in cytochrome c levels in the group pre-treated with test compound (0.50 ±â€¯0.14) compared to radiation alone group (1.60 ±â€¯0.07) was observed. DT(GS)2Mn(II) attenuated radiation induced apoptosis by promoted expression of anti-apoptotic Bcl-2 along with suppression of cyt-c release and augmented cell survival following irradiation. A distinct improvement in villi length was observed in the group treated with DT(GS)2Mn(II) with an average of 1546 ±â€¯61 µm versus 763 ±â€¯154 µm for radiation alone group. The present findings suggested DT(GS)2Mn(II) is a promising radioprotective agent and exerts it protective effect both invitro and invivo systems by decreasing radiation induced cytotoxicity.

Optimization by design of etoposide loaded solid lipid nanoparticles for ocular delivery: Characterization, pharmacokinetic and deposition study.

The present study was to develop etoposide loaded solid lipid nanoparticles (SLN) and optimize it for effective ocular delivery to the posterior eye. SLN were prepared by melt-emulsification and ultrasonication technique. Etoposide loaded SLN were optimized by using three-factor three levels Box-Behnken design to establish the functional relationships between variables on responses of particle size, polydispersity index (PDI) and entrapment efficiency (EE). SLN were characterized for size & surface morphology, entrapment efficiency and in vitro release. Further the pharmacokinetic study of optimized formulation after intravitreal administration was evaluated in Wister rats. The deposition in the ocular tissues was checked by scintigraphic analysis in Albino rabbits. Histology was also done to evaluate morphological changes if any occur after treatment. The particle size, PDI and EE obtained for the optimized formulation (Z15) were 239.43 ±â€¯2.35 nm, 0.261 ±â€¯0.001 and 80.96 ±â€¯2.21% respectively. Single intravitreal administrations of SLN were able to give sustained etoposide concentration in the vitreous for 7 consecutive days which was also supported by the results of Gamma scintigraphic study. Histology of posterior ocular tissues do not showed any serious toxic effect. Therefore it can concluded that etoposide loaded SLN was able to maintain vitreous concentration of drug without any serious toxic effect to the surrounding ocular tissues after an intravitreous administration in rat eye.

Evaluation of BBB permeable nucleolipid (NLDPU): A di-C15-ketalised palmitone appended uridine as neuro-tracer for SPECT.

Despite being in routine for onco-diagnostics for years, the applicability of nucleosidic molecular imaging probes is severely restricted in neurological applications due to their low permeability across blood-brain-barrier (BBB). For extending nucleoside tracers utility for neuro-onco early diagnostics, suitable modification which enhances their BBB permeation needs investigation. Among various modifications, lipidization of nucleosides has been reported to enhance cellular permeability. Extending the concept, the aim was to exemplify the possibility of lipidized nucleosides as potential brain tracer with capability to cross intact BBB and evaluate as metal based neuro-imaging SPECT agent. Uridine based non-lipidic (NSDAU) and di-C15-ketal appended lipidic (NLDPU) ligands were conjugated to chelator, DTPA (DTPA-NSDAU and DTPA-NLDPU) using multi-step chemistry. The ligands were evaluated in parallel for comparative physical and biological parameters. Additionally, effects of enhanced lipophilicity on UV-absorption, acid strength, fluorescence and non-specific protein binding were evaluated. Fluorescence quenching of BSA indicated appreciable interaction of DTPA-NLDPU with protein only above 10 mM without inducing conformational changes. In addition, DTPA-NLDPU was found to be haematocompatible and cytocompatible with low dose-dependent toxicity in HEK-cells. The chelator DTPA was used for 99mTc-complexation for SPECT imaging. Optimized 99mTc-radiolabeling parameters resulted in quantitative (≥97%) labeling with good stability parameters in in-vitro serum and cysteine challenge studies. We demonstrate that the nucleolipid radiotracer (99mTc-DTPA-NLDPU) was successfully able to permeate the BBB with brain uptake of 0.2% ID/g in normal mice as compared to 0.06% ID/g uptake of 99mTc-DTPA-NSDAU at 5 min. Blood kinetics indicate biphasic profile and t1/2(distribution) 46 min for 99mTc-DTPA-NLDPU. The preferential accumulation of 99mTc-DTPA-NLDPU in brain tumor intracranial xenograft indicate the targeting capability of the nucleoside. We conclude that as first-of-its-kind, this work presents the potential of the biocompatible nucleolipidic system for brain targeting and early diagnostics.

Radiolabeling and Preclinical Evaluation of a New S-Alkylated Cysteine Derivative Conjugated to C-Substituted Macrocycle for Positron Emission Tomography.

A new S-alkylated cysteine-derivatized tumor targeting agent, 2,2'-(12-(2-((2-acetamido-2-carboxyethyl)thio)acetamido)-11,13-dioxo-1,4,7,10-tetraazacyclotridecane-4,7-diyl)diacetic acid was developed for positron emission tomography (PET) imaging. N-Acetyl cysteine (NAC) was conjugated to ATRIDAT as a specific targeting agent toward L-type and ASC amino acid transporter systems in the oncogenic cells. NAC was attached via S-alkylation to prevent its incorporation at undesired recognition sites affecting the signal-to-noise ratio. NAC-ATRIDAT was subjected to gallium-68 complexation with >75% radiolabeling yield. The radiocomplex was purified through the tc18 cartridge to obtain 99.89% radiochemical yield. IC-50 of the NAC-ATRIDAT conjugate was 0.8 mM in A549 cells as evaluated through 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazonium bromide assay. Binding affinity experiments on A549 cells showed noteworthy binding with KD in the nanomolar range. A time course study showed a Km value of 0.19 µM and Vmax value of 0.49 pmol/µg protein/min showing reasonable tumor kinetics. Efflux studies showed that the synthesized radioligand is transported majorly by LAT followed by the ASC system. Clearance was found to be renal with 7.67 ± 1.48% ID/g uptake at 30 min which substantially declined to 0.52 ± 0.% ID/g at 4 h. A significant uptake of 10.06 ± 1.056% ID/g was observed at the tumor site in mice at 1 h. µPET images revealed a high contrast with a tumor-to-kidney ratio of 4.8 and a tumor-to-liver ratio of 35.85 at 1 h after injection. These preclinical in vitro and in vivo evaluation supports its potential on the way of becoming a successful 68Ga-radiolabeled amino acid-based PET imaging agent.

Rose Bengal attached and dextran coated gadolinium oxide nanoparticles for potential diagnostic imaging applications.

We report here, reverse micelle mediated synthesis of multifunctional dextran (dex) coated Gd2O3 nanoparticles (NPs) carrying rose bengal (RB) dye for magnetic resonance and optical imaging. The diameter of these RB attached dex coated Gd2O3 NPs (Gd-dex-RB NPs) was found to be ~17 nm as measured by TEM. NMR line broadening effect on the surrounding water protons affirmed the paramagnetic nature of these NPs. Optical properties of Gd-dex-RB NPs were validated by UV-Vis and fluorescence spectroscopy. Time dependent release profile of RB from NPs at two different pH of 7.4 and 5.0 revealed that these NPs behave as slow releasing system. In-vitro study revealed that NPs are efficiently taken up by cells and show optical activity in cellular environment. In vitro cell viability (SRB) assay was performed on cancerous (A-549, U-87) and normal (HEK-293) cell lines, showed the absence of cytotoxic effect of Gd-dex-RB NPs. Therefore, such multifunctional NPs can be efficiently used for bio-imaging and optical tracking.

99mTc-Methionine Hybrid SPECT/CT for Detection of Recurrent Glioma: Comparison With 18F-FDG PET/CT and Contrast-Enhanced MRI.

OBJECTIVES: Posttherapy changes in treated glioma patients cannot be reliably differentiated from tumor recurrence. We evaluated the role of Tc-methionine SPECT/CT for the detection of recurrent glioma and compared the same with F-FDG PET/CT and contrast-enhanced MRI (CeMRI). METHODS: Forty-four patients with histologically proven, previously treated glioma and clinical suspicion of recurrence were prospectively enrolled in the study. Of these 44 patients, 39 (28 male and 11 female subjects; age, 38.05 ± 9.7 years) underwent Tc-methionine SPECT/CT, F-FDG PET/CT, and CeMRI of the brain and were included for final analysis. Combination of repeat imaging, biopsy, and/or clinical follow-up (6-36 months) was taken as reference standard. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were calculated. Diagnostic values among modalities were compared. RESULTS: Positive predictive value and negative predictive value for Tc-methionine SPECT/CT, F-FDG PET/CT, and CeMRI were 95.6% and 56.2%, 92.3% and 61.5%, and 79.4% and 42.9%, respectively. Sensitivity and specificity for the 3 modalities were 75.9% and 90%, 82.8% and 80%, and 87.1% and 30%. Specificity of Tc-methionine SPECT/CT was significantly higher than that of CeMRI (P < 0.0001) but not of F-FDG PET/CT (P = 0.36). No significant difference was seen between the modalities for sensitivity and accuracy. CONCLUSIONS: Tc-methionine is a promising tracer for detection of recurrent glioma. Diagnostic values of Tc-methionine SPECT/CT are similar to F-FDG, although it is more specific than CeMRI. So it may be used as a cost-effective alternative and also where PET/CT is not available.

Differentiation of Recurrent/Residual Glioma From Radiation Necrosis Using Semi Quantitative 99mTc MDM (Bis-Methionine-DTPA) Brain SPECT/CT and Dynamic Susceptibility Contrast-Enhanced MR Perfusion: A Comparative Study.

PURPOSE: In this study, Tc MDM (bis-methionine-DTPA) SPECT was used for the detection and differentiation of recurrent/residual glioma from radiation necrosis and the results were compared with dynamic susceptibility contrast-enhanced (DSCE)-MRI and clinical findings. MATERIALS AND METHODS: Twenty-eight patients (18 men and 10 women; mean ± SD age, 41.4 ± 15.03 years) with histologically proven glioma (grade IV, 14; grade III, 7; grade II, 7) who were planned for postsurgical standard radio/chemo therapy were recruited prospectively. All the patients underwent technetium Tc MDM SPECT/CT and DSCE-MRI imaging at 6 months after surgery/radio-chemotherapy, 9 of 28 patients also underwent SPECT imaging at 1 to 2 weeks after surgery. RESULTS: Tc MDM SPECT/CT analysis demonstrated significantly higher target to nontarget (T/NT) ratio of the radiotracer in tumor recurrence than in radiation necrosis (3.59 ± 1.70 vs 1.16 ± 0.42). Likewise, the normalized cerebral blood volume (nCBV) values in patients with tumor recurrence were also significantly higher than in radiation necrosis (5.16 ± 2.30 vs 1.63 ± 0.94). A positive correlation (rho = 0.823, P < 0.0001) between T/NT ratios and nCBV was observed. The cutoff T/NT ratios and nCBV values estimated by receiver operating characteristic analysis were greater than 1.50 (area under the curve, 0.944 ± 0.34) and greater than 2.12 (area under the curve, 0.931 ± 0.39), respectively. Combining the results of Tc MDM SPECT/CT, DSCE-MRI, and clinical findings, diagnosis of recurrent/residual glioma or radiation necrosis was made in 18 and 10 patients, respectively. Sensitivity and specificity of 2 techniques were comparable, that is, 92.0%: 78.6% for MDM SPECT/CT and of 92.0%: 71.4% for DSCE-MRI, respectively. CONCLUSION: Thus, combining MDM SPECT with DSCE MRI may provide an accurate method for differentiation of tumor recurrence from radiation-induced necrosis in glioma patients.

PEG coated and doxorubicin loaded multimodal Gadolinium oxide nanoparticles for simultaneous drug delivery and imaging applications.

We report water-in-oil microemulsion mediated synthesis of PEG1 coated Gd2O3 NPs2 loaded with fluorescent anti-cancer drug dox3 for synchronous drug delivery, optical and MR4 imaging applications. These PEG covered Gd2O3 NPs loaded with dox (Gd-PEG-dox NPs) were found to possess spherical morphology with 13nm size as measured from TEM and the hydrodynamic diameter comes out to be 37nm as determined from DLS. Fluorescence spectra and fluorescence microscopy images confirmed optical activity of the NPs. The paramagnetic nature of NPs was affirmed by NMR line broadening effect on the spectrum of surrounding water protons. Therefore, these particles can be efficiently used as CA5 in MR imaging. In vitro analysis showed significant cellular uptake of particles by A-549 cells. A pH dependent drug release pattern was observed for the NPs. Cell viability assay performed on A-549, PANC-1 and U-87 cancerous cell lines revealed that Gd-PEG-dox NPs are cytotoxic. On the basis of these observations, it can be concluded that these multi-modal paramagnetic NPs promise potential cancer therapy along with optical and MR imaging applications.