Radiolabeled Chalcone Derivatives as Potential Radiotracers for ß-Amyloid Plaques Imaging.

Natural products often provide a pool of pharmacologically relevant precursors for the development of various drug-related molecules. In this review, the research performed on some radiolabeled chalcone derivatives characterized by the presence of the α-ß unsaturated carbonyl functional group as potential radiotracers for the imaging of ß-amyloids plaques will be summarized. Chalcones' structural modifications and chemical approaches which allow their radiolabeling with the most common SPECT (Single Photon Emission Computed Tomography) and PET (Positron Emission Tomography) radionuclides will be described, as well as the state of the art regarding their in vitro binding affinity and in vivo biodistribution and pharmacokinetics in preclinical studies. Moreover, an explanation of the rationale behind their potential utilization as probes for Alzheimer's disease in nuclear medicine applications will be provided.

Curcumin-Based ß-Diketo Ligands for Ga3+: Thermodynamic Investigation of Potential Metal-Based Drugs.

Curcumin is known for its therapeutic properties; among these, antioxidant, anti-inflammatory and anti-cancer ones stand out. Besides, curcumin metal complexes have shown widespread application in medicine and can be exploited as lead structures for developing metal-based drugs. Unfortunately, curcumin is poorly bioavailable, mainly due to its instability in physiological conditions; this weakness is tightly connected to the presence of the ß-diketo moiety undergoing tautomeric equilibrium. Stability and metal-chelating ability can be tuned by modulating the electronic effects and steric hindrance close to the ß-diketo moiety; in addition, formation of a metal complex shifts the tautomeric equilibrium towards the ß-keto-enol form and increases stability in biological media. Among the metals used in clinical therapy, gallium nitrate has shown to have significant antitumor activity against non-Hodgkin lymphoma and bladder cancer, thus indicating that gallium-based drugs have potential for further development as antineoplastic agents with improved therapeutic activity. Curcuminoids have demonstrated high affinity for gallium(III), allowing the formation of stable positively charged M:L 1:2 ß-diketonate complexes that benefit from the therapeutic activity of both the metal and the ligand. Seven new curcumin derivatives were synthesized and completely characterized. The new derivatives retain the solvent-dependent keto-enol tautomerism, with the prevalence of the diketo form in aqueous solution. Enhanced stability in simulated physiological conditions was observed in comparison to the lead compound curcumin. The presence of Ga3+ anticipates the dissociation of the enolic proton, allowing chelate complex formation, and simultaneously it shifts the tautomeric equilibrium towards the keto-enol form. A complete 1H/13C NMR and UV-Vis study was performed to define the metal-to-ligand stoichiometry ratio and the overall stability constants. In addition, we demonstrated that some of the derivatives have increased antiproliferative activity on colon cancer cells compared to curcumin and antioxidant properties. On the whole, the synthesized curcumin-based molecules may act as new gallium(III) chelators with improved stability with respect to curcumin and could open interesting perspectives for the development of novel therapeutic agents for cancer.

Topical L-Ascorbic Acid Formulation for a Better Management of Non-Melanoma Skin Cancer: Perspective for Treatment Strategies.

L-ascorbic acid, is a well-known molecule, sometimes used as antioxidant for skin care. Nonetheless, few studies have taken in account its utility as topical treatment for non-melanoma skin vancer. Non-melanoma skin cancer includes basal cell carcinoma and squamous cell carcinoma and is widespread worldwide with an increasing incidence. The purpose of this paper is to analyze the characteristics of L-ascorbic acid topical formulation, its percutaneous absorption and biochemical mechanism, focusing on its anti-cancer properties. In particular, it will be described how the pH and the concentration of the formulation are able to influence its distribution in the skin and tissues. We will report, the current knowledge on the pharmacokinetic aspects of L-ascorbic acid that allows us to reconsider it in the light of its ability to act as a prodrug and as an anticancer agent. Lastly, a short review with the aim to find any evidence of a possible clinical use of L-ascorbic acid for the treatment of non-melanoma skin cancer was made.

Gallium-68 and scandium-44 labelled radiotracers based on curcumin structure linked to bifunctional chelators: Synthesis and characterization of potential PET radiotracers.

Curcumin metal complexes showed widespread applications in medicine and can be exploited as a lead structure for developing new tracers for nuclear medicine application. Herein, the synthesis, chemical characterization and radiolabelling with gallium-68 and scandium-44 of two new targeting vectors based on curcumin scaffolds and linked to the chelators 1,4,7-triazacyclononane,1-glutaric acid-4,7-acetic acid (NODAGA) and 1,4-bis(carboxymethyl)-6-[bis(carboxymethyl)]amino-6-methylperhydro-1,4-diazepine (AAZTA) are reported. Synthesis of the precursors could be achieved with a 13% and 11% yield and radiolabelling generally afforded rapid incorporation under mild conditions (>95%). Stability in physiological media (~75% after 2 h in human blood for [68Ga]Ga-/[44Sc]Sc-AAZTA-PC21 and ~60% for [68Ga]Ga-NODAGA-C21, respectively) are generally enhanced if compared to the previously radiolabelled analogues. MSn fragmentation experiments showed high stability of the AAZTA-PC21 structure mainly due to the pyrazole derivatization of the curcumin keto-enol moiety and a more feasible radiolabelling was noticed both with gallium-68 and scandium-44 mainly due to the AAZTA-chelator properties. [68Ga]Ga-NODAGA-C21 showed the most favorable lipophilicity value (logD = 1.3). Due to these findings, both compounds appear to be promising candidates for the imaging of colorectal cancer, but further studies such as in vitro uptake and in vivo biodistribution experiments are needed.

64Cu and fluorescein labeled anti-miRNA peptide nucleic acids for the detection of miRNA expression in living cells.

MiRNAs are single stranded RNAs of 18-22 nucleotides. They are promising diagnostic and prognostic markers for several pathologies including tumors, neurodegenerative, cardiovascular and autoimmune diseases. In the present work the development and characterization of anti-miRNA radiolabeled probes based on peptide nucleic acids (PNAs) for potential non-invasive molecular imaging in vivo of giant cell arteritis are described. MiR-146a and miR-146b-5p were selected as targets because they have been found up-regulated in this disease. Anti-miR and scramble PNAs were synthesized and linked to carboxyfluorescein or DOTA. DOTA-anti-miR PNAs were then labelled with copper-64 (64Cu) to function as non-invasive molecular imaging tools. The affinity of the probes for the targets was assessed in vitro by circular dichroism and melting temperature. Differential uptake of fluorescein and 64Cu labeled anti-miRNA probes was tested on BCPAP and A549 cell lines, expressing different levels of miR-146a and -146b-5p. The experiments showed that the anti-miR-146a PNAs were more effective than the anti-miR-146b-5p PNAs. Anti-miR-146a PNAs could bind both miR-146a and miR-146b-5p. The uptake of fluorescein and 64Cu labeled anti-miR-146a PNAs was higher than that of the negative control scramble PNAs in miRNA expressing cells in vitro. 64Cu-anti-miR-146a PNAs might be further investigated for non-invasive PET imaging of miR-146 overexpressing diseases.

Development of a Potential Gallium-68-Labelled Radiotracer Based on DOTA-Curcumin for Colon-Rectal Carcinoma: From Synthesis to In Vivo Studies.

Colorectal cancer is the third most commonly occurring cancer in men and the second most commonly occurring cancer in women worldwide. We have recently reported that curcuminoid complexes labelled with gallium-68 have demonstrated preferential uptake in HT29 colorectal cancer and K562 lymphoma cell lines compared to normal human lymphocytes. In the present study, we report a new gallium-68-labelled curcumin derivative (68Ga-DOTA-C21) and its initial validation as marker for early detection of colorectal cancer. The precursor and non-radioactive complexes were synthesized and deeply characterized by analytical methods then the curcuminoid was radiolabelled with gallium-68. The in vitro stability, cell uptake, internalization and efflux properties of the probe were studied in HT29 cells, and the in vivo targeting ability and biodistribution were investigated in mice bearing HT29 subcutaneous tumour model. 68Ga-DOTA-C21 exhibits decent stability (57 ± 3% after 120 min of incubation) in physiological media and a curcumin-mediated cellular accumulation in colorectal cancer cell line (121 ± 4 KBq of radiotracer per mg of protein within 60 min of incubation). In HT29 tumour-bearing mice, the tumour uptake of 68Ga-DOTA-C21 is 3.57 ± 0.3% of the injected dose per gram of tissue after 90 min post injection with a tumour to muscle ratio of 2.2 ± 0.2. High amount of activity (12.73 ± 1.9% ID/g) is recorded in blood and significant uptake of the radiotracer occurs in the intestine (13.56 ± 3.3% ID/g), lungs (8.42 ± 0.8% ID/g), liver (5.81 ± 0.5% ID/g) and heart (4.70 ± 0.4% ID/g). Further studies are needed to understand the mechanism of accumulation and clearance; however, 68Ga-DOTA-C21 provides a productive base-structure to develop further radiotracers for imaging of colorectal cancer.

Post-Synthesis Incorporation of 64Cu in CuS Nanocrystals to Radiolabel Photothermal Probes: A Feasible Approach for Clinics.

We report a simple method for the incorporation of Cu(I) or (64)Cu(I) radionuclides in covellite nanocrystals (CuS NCs). After the in situ reduction of Cu(II) or (64)Cu(II) ions by ascorbic acid, their incorporation in PEG-coated CuS NCs takes place at room temperature. In all the reaction steps, the stability of the NCs under physiological conditions was ensured. The copper incorporation reaction could also take place on CuS NCs bearing biotin molecules at their surface, with no detrimental effects on the specific binding affinity of the NCs toward streptavidin after incorporation. At low loading of Cu ions, the strong near-infrared (NIR) absorption band of the starting CuS NCs was essentially preserved, which allowed for efficient plasmonic photothermal therapy. The combined presence in the NCs of (64)Cu ions, well suitable for positron emission tomography, and of free carriers responsible for the NIR absorption, should enable their theranostic use as radiotracers and as photothermal probes in tumor ablation treatments. Moreover, the simplicity of the preparation scheme, which involves the use of radioactive species only as a last step, makes the protocol easily transferable to the clinical practice.

Development of a simple kit-based method for preparation of pharmaceutical-grade 68Ga-DOTATOC.

INTRODUCTION: The use of germanium-68 (68Ge)/gallium-68 (68Ga) generators is still limited when compared with the 99Mo/99mTc counterpart, mainly because of the absence of commercial kits and a kit-based method for preparing Ga-labelled radiopharmaceuticals in a reliable way. The present study aimed to develop and optimize a reliable direct labelling of DOTATOC with 68Ga through a kit-based approach. MATERIALS AND METHODS: A fraction of the eluate of two different 68Ge/68Ga generators was directly injected into a vial prefilled with precursor, buffer and scavenger (the prototype of a potential lyophilized kit). The vial was directly warmed to 100°C and then buffered with a 1.5 mol/l sodium ascorbate solution. The parameters influencing the reaction were studied and optimized. The efficacy of the method in terms of incorporation yield and quality of the final radiotracer was compared with preparations performed with two commercial automatic synthesizers by applying the tests prescribed in the European Pharmacopeia monograph for 68Ga-DOTATOC. RESULTS: Under optimal conditions, the overall radiochemical yields of the kit-based process were 73±4 and 69±3% not decay-corrected for the IGG100 and itG generator, respectively. The radiochemical purity was 95±3% and the preparations were compliant with all specifications given in the pharmacopoeia monograph. CONCLUSION: The feasibility of a kit-based approach for the preparation of 68Ga-DOTATOC was proved and a first home-made version of a putative lyophilized kit was proposed.