Search

Introduction Alpha-emitting radionuclides have gained considerable attention as payloads for cancer targeting molecules due to their high cytotoxicity. One attractive radionuclide for this purpose is 212 Pb, which by itself is a β-emitter, but acts as an in vivo generator for its short-lived α-emitting daughters. The standard method of preparing 212 Pb-labeled antibodies requires handling and evaporation of strong acids containing high radioactivity levels by the end user. An operationally easier and more rapid process could be useful since the 10.6h half-life of 212 Pb puts time constraints on the preparation protocol. In this study, an in situ procedure for antibody labeling with 212 Pb, using a solution of the generator nuclide 224 Ra, is proposed as an alternative protocol for preparing 212 Pb-radioimmunoconjugates. Methods Radium-224, the generator radionuclide of 212 Pb, was extracted from its parent nuclide, 228 Th. Lead-212-labeling of the TCMC-chelator conjugated monoclonal antibody trastuzumab was carried out in a solution containing 224 Ra in equilibrium with progeny. Subsequently, the efficiency of separating the 212 Pb-radioimmunoconjugate from 224 Ra and other unconjugated daughter nuclides in the solution using either centrifugal separation or a PD-10 desalting size exclusion column was evaluated and compared. Results Radiolabeling with 212 Pb in 224 Ra-solutions was more than 90% efficient after only 30min reaction time at TCMC-trastuzumab concentrations from 0.15mg/mL and higher. Separation of 212 Pb-labeled trastuzumab from 224 Ra using a PD-10 column was clearly superior to centrifugal separation. This method allowed recovery of approximately 75% of the 212 Pb-antibody-conjugate in the eluate, and the remaining amount of 224 Ra was only 0.9±0.8% (n=7). Conclusions The current work demonstrates a novel method of producing 212 Pb-based radioimmunoconjugates from a 224 Ra-solution, which may be simpler and less time-consuming for the end user compared with the method established for use in clinical trials of 212 Pb-TCMC-trastuzumab.

Nanoparticulates responsive to X-rays offer increased efficacy of radiation therapy. However, successful demonstrations of such nanoparticle use are limited so far due to lack of significant radiosensitizing effects or poor nanoparticle stability in a biological system. Zinc oxide (ZnO) is the most promising biocompatible material for medicinal applications. In this paper, we report preparation and characterization of scintillating ZnO/SiO2 core-shell nanoparticles. The ZnO/SiO2 nanoparticles absorb ultraviolet (UV) radiation (below 360nm) and emit green fluorescence (400-750nm, maximum 550nm). Under X-ray irradiation (200kVp), the nanoparticles scintillate emitting luminescence in the region 350-700nm (maximum 420nm). The synthesized ZnO/SiO2 nanoparticles are stable in a biologically relevant environment (water and cell growth medium). The potential of the ZnO/SiO2 nanoparticles for radiosensitization is demonstrated in human prostate adenocarcinoma cell lines (LNCaP and Du145). The nanoparticles enhance radiation-induced reduction in cell survival about 2-fold for LNCaP and 1.5-fold for Du145 cells. Radiosensitizing effect can be attributed to X-ray-induced radiocatalysis by the nanoparticles.

Alpha-emitting radionuclides have gained considerable attention as payloads for cancer targeting molecules due to their high cytotoxicity. One attractive radionuclide for this purpose isRadium-224, the generator radionuclide ofRadiolabeling withThe current work demonstrates a novel method of producing

Medicinal applications of luminescent quantum dots (QDs) are of growing interest. In spite of the fact that their fabrication and imaging functions have been extensively investigated during the last decade, very little is known on curative potential of the QDs. In this study, we focus on cytotoxicity and phototoxicity of red-absorbing (

Semiconductor quantum dots and nanoparticles composed of metals, lipids or polymers have emerged with promising applications for early detection and therapy of cancer. Quantum dots with unique optical properties are commonly composed of cadmium contained semiconductors. Cadmium is potentially hazardous, and toxicity of such quantum dots to living cells, and humans, is not yet systematically investigated. Therefore, search for less toxic materials with similar targeting and optical properties is of further interest. Whereas, the investigation of luminescence nanoparticles as light sources for cancer therapy is very interesting. Despite advances in neurosurgery and radiotherapy the prognosis for patients with malignant gliomas has changed little for the last decades. Cancer treatment requires high accuracy in delivering ionizing radiation to reduce toxicity to surrounding tissues. Recently some research has been focused in developing photosensitizing quantum dots for production of radicals upon absorption of visible light. In spite of the fact that visible light is safe, this approach is suitable to treat only superficial tumours. Ionizing radiation (X-rays and gamma rays) penetrate much deeper thus offering a big advantage in treating patients with tumours in internal organs. Such concept of using quantum dots and nanoparticles to yield electrons and radicals in photodynamic and radiation therapies as well their combination is reviewed in this article.

So far most of the work on nanoparticles and quantum dots has been focused on methods of production and applications in fluorescence imaging. The possibility to use quantum dots as photosensitizers (nanosensitizers) remains unexplored: Can these nanocrystals generate reactive oxygen and nitrogen species (RONS) in biological environments? A potential possibility of using quantum dots simultaneously with red light for photodynamic therapy has been demonstrated in this study in aqueous solutions, cultured cells and skin of mice. Dihydrorhodamine 123 (DHR) had been chosen as a radical probe. High production of Rh123 (oxidation product of DHR) confirms radical generation of nitrogen oxides (NOX). One of them, peroxynitrite (ONOO−), is a product of the reaction of nitric oxide (NO) with superoxide (O−2) being evidence for that the latter anion can also be generated by quantum dots and red light. Lack of photooxidation of 9,10-dimethylanthracene (DMA) and the Singlet Oxygen Sensor Green (SOSG) indicates that singlet oxygen may not be generated by quantum dots under the present conditions. Quantum dots can also be used in photochemical internalization: Exposure of cancer cells incubated with quantum dots in vitro to blue light leads to lysosomal rupture and to increase of the fluorescence of the quantum dots (photoactivation). Quantum dots composed of CdSe with ZnS shell were more effective to oxidize DHR than quantum dots composed of non-heavy metals InGaP with ZnS shell.

Targeting cancer vasculature is an emerging field in cancer treatment. Photochemical internalization (PCI) is a drug delivery technology based on photochemical lysis of drug-bearing endocytic vesicles originally designed to target cancer cells. Recent investigations have revealed a lower PCI efficacy in vascular endothelial cells (HUVECs) in vitro than in HT1080 fibrosarcoma cells. This manuscript aims to explore the limiting factor for the PCI effect in HUVECs. Cellular uptake of the photosensitizers AlPcS(2a) and TPPS(2a), and a model compound for macromolecular drugs taken up by fluid phase endocytosis, Alexa⁴⁸⁸-dextran, was explored by flow cytometry. The uptake of AlPcS(2a) and TPPS(2a) was 3.8-fold and 37-fold higher in HUVECs than in HT1080 cells, respectively, while the Alexa⁴⁸⁸-dextran uptake was 50% lower. AlPcS(2a) (but not TPPS(2a)) was shown to reduce Alexa⁴⁸⁸-dextran uptake in a concentration-dependent manner, resulting in 66% and 33% attenuation of Alexa⁴⁸⁸-dextran uptake at 20 μg/ml AlPcS(2a) in HUVECs and HT1080 cells respectively. Studies of intracellular localization of Alexa⁴⁸⁸-dextran and AlPcS(2a) by confocal microscopy in HUVECs uncovered a concentration-dependent AlPcS(2a)-induced inhibition of Alexa⁴⁸⁸-dextran trafficking into AlPcS(2a)-stained and acidic vesicles. The localization of Alexa⁴⁸⁸-dextran to AlPcS(2a)-localizing compartments was reduced by 40% when the AlPcS(2a) concentration was increased from 5 to 20 μg/ml. The treatment dose of AlPcS(2a) was found to influence on the efficacy of PCI of saporin, but to a lesser extent than expected considering the data from cellular uptake and intracellular trafficking of Alexa⁴⁸⁸-dextran. The implications of these results for further development of vascular targeting-PCI are discussed.

Immunotherapy (IT) with the anti-CD20 monoclonal antibody rituximab in combination with chemotherapy has resulted in significantly improved response rate and survival in patients with various types of CD20 positive B-cell lymphoproliferative disorders. To be effective, rituximab depends on selective expression of a sufficient number of CD20 antigens per cell. Treatment with rituximab alone or in combination with chemotherapy can, however, result in disappearance of the CD20 expression, which may result in reduced clinical effect of subsequent CD20 targeted treatments. We have discovered that treatment of NHL in vitro and in vivo with the anti-CD37 antibody radionuclide conjugate (ARC) 177Lu-DOTA-HH1 (177Lu-HH1 or Betalutin™) results in an upregulation of the CD20 antigen expression, and therefore represents a rationale for a combination treatment with both agents. The in vitro expression of CD20 in Burkitt's Lymphoma, Daudi, cells 1-7 days after treatment with 177Lu-HH1 increased up to 120 % when compared with cells treated with unlabeled mAb, while Ramos (Burkitt's Lymphoma) and Rec-1 (Mantle Cell Lymphoma) cells showed 10 to 30 % increase, indicating a variation of the antigen upregulation in vitro with different cell lines. An upregulation of CD20 at the same order of magnitude was observed when cells where treated with similar absorbed radiation doses of external beam radiation. Treatment of nude mice with Ramos xenografts with 177Lu-HH1 resulted in a 3 times higher uptake of radiolabeled rituximab in tumor xenografts 5 days after start of treatment than in mice treated with unlabeled HH1 (p < 0.05) while uptake in normal organs was similar in both treatment groups (p > 0.05). SCID mice with intravenously injected Rec-1 cells were treated with NaCl, 100 mg rituximab, 40 MBq/kg 177Lu-HH1 or with the combination of 40 MBq/kg 177Lu-HH1 followed with 100 mg rituximab 5 days later. The combination of 177Lu-HH1 and rituximab resulted in significantly improved survival as compared with NaCl or rituximab alone, and a strong therapeutic gain as compared with 177Lu-HH1 alone (Table 1). In conclusion, 177Lu-HH1 treatment seems to improve uptake of rituximab and increase tumor suppression when used prior to anti-CD20 monoclonal antibody targeting in preclinical models. The reason for the upregulation of CD20 is probably related to the oxidative stress induced by the ARC-treatment, which will be evaluated in further studies. If the upregultation of CD20 is confirmed in clinical studies this effect could affect the way ARC and CD20 immunotherapy would be used in the future. Table 1. Therapy experiment groups and result Group Median ± SD Surviving fraction at the end of the study % Increase in symptom free survival compared to control NaCl + NaCl 64 ± 2 0.1 ---- NaCl + Rituximab 75 ± 10 0.3 15.4 177 Lu-HH1 + NaCl 92 ± 14 * 0.3 43.8 177 Lu-HH1 + Rituximab > 132 * 0.7 > 106.3 *Significantly different from NaCl + NaCl group (p < 0.01) Disclosures Repetto-Llamazares: Nordic Nanovector ASA: Employment, Equity Ownership. Larsen:Nordic Nanovector ASA: Equity Ownership, Membership on an entity's Board of Directors or advisory committees. Stokke:Nordic nanovector ASA: Equity Ownership. Generalov:Nordic Nanovector ASA: Employment. Dahle:Nordic Nanovector ASA: Employment, Equity Ownership.

Roman Generalov1,2, Simona Kavaliauskiene1, Sara Westrøm1, Wei Chen3, Solveig Kristensen2, Petras Juzenas11Department of Radiation Biology, Institute for Cancer Research, Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway; 2School of Pharmacy, University of Oslo, Oslo, Norway; 3Department of Physics, The University of Texas at Arlington, Arlington, TX, USAAbstract: Quantum dots have emerged with great promise for biological applications as fluorescent markers for immunostaining, labels for intracellular trafficking, and photosensitizers for photodynamic therapy. However, upon entry into a cell, quantum dots are trapped and their fluorescence is quenched in endocytic vesicles such as endosomes and lysosomes. In this study, the photophysical properties of quantum dots were investigated in liposomes as an in vitro vesicle model. Entrapment of quantum dots in liposomes decreases their fluorescence lifetime and intensity. Generation of free radicals by liposomal quantum dots is inhibited compared to that of free quantum dots. Nevertheless, quantum dot fluorescence lifetime and intensity increases due to photolysis of liposomes during irradiation. In addition, protein adsorption on the quantum dot surface and the acidic environment of vesicles also lead to quenching of quantum dot fluorescence, which reappears during irradiation. In conclusion, the in vitro model of phospholipid vesicles has demonstrated that those quantum dots that are fated to be entrapped in endocytic vesicles lose their fluorescence and ability to act as photosensitizers.Keywords: fluorescence lifetime, free radicals, liposomes, lipodots, reactive oxygen species

Aims: Polysaccharide nanoparticles were studied as drug delivery vehicles for chemopreventive agents. Materials & methods: Green tea polyphenol epigallocatechin-3-gallate (EGCG) was incorporated into a carbohydrate matrix of gum arabic and maltodextrin with an encapsulation efficiency of approximately 85%. Results: Encapsulated EGCG retained its biological activity, reducing the cell viability and inducing apoptosis of Du145 prostate cancer cells. Clonogenic assay demonstrated that encapsulation of EGCG enhanced its inhibitory effect on cell proliferation (10–20%) at lower concentrations (1–2 µM), compared with free EGCG. Conclusion: This study highlights the use of polysaccharide nanoparticles in chemoprevention as they can be used to deliver natural antioxidants capable of inhibiting steps of the tumorigenesis process.

Medicinal applications of luminescent semiconductor quantum dots are of growing interest. In spite of the fact that their fabrication and imaging applications have been extensively investigated for the last decade, very little is documented on photodynamic action of quantum dots. In this study we demonstrate generation of singlet oxygen and other radical species upon exposure of quantum dots to blue light and therapeutic red light. Extent of radical production can be readily modified by antioxidants. Lay and scientific communities are two sites concerning potential hazards and enthusiastic applications of nanotechnology. Synthesis of quantum dots composed of less toxic materials is of great interest. A new candidate is a ubiquitous element carbon, which on nanoscale exhibits strong photoluminescence.