Chemical nature and structure of organic coating of quantum dots is crucial for their application in imaging diagnostics

Rumiana Bakalova1, Zhivko Zhelev1, Daisuke Kokuryo1, Lubomir Spasov2, Ichio Aoki1, Tsuneo Saga11Molecular Imaging Center, National Institute of Radiological Sciences, Chiba, Japan; 2Medical Faculty, Sofia University, Sofia, BulgariaBackground: One of the most attractive properties of quantum dots is their potential to extend the opportunities for fluorescent and multimodal imaging in vivo. The aim of the present study was to clarify whether the composition and structure of organic coating of nanoparticles are crucial for their application in vivo.Methods: We compared quantum dots coated with non-crosslinked amino-functionalized polyamidoamine (PAMAM) dendrimers, quantum dots encapsulated in crosslinked carboxyl-functionalized PAMAM dendrimers, and silica-shelled amino-functionalized quantum dots. A multimodal fluorescent and paramagnetic quantum dot probe was also developed and analyzed. The probes were applied intravenously in anesthetized animals for visualization of brain vasculature using two-photon excited fluorescent microscopy and visualization of tumors using fluorescent IVIS® imaging (Caliper Life Sciences, Hopkinton, MA) and magnetic resonance imaging.Results: Quantum dots coated with non-crosslinked dendrimers were cytotoxic. They induced side effects in vivo, including vasodilatation with a decrease in mean arterial blood pressure and heart rate. The quantum dots penetrated the vessels, which caused the quality of fluorescent imaging to deteriorate. Quantum dots encapsulated in crosslinked dendrimers had low cytotoxicity and were biocompatible. In concentrations <0.3 nmol quantum dots/kg bodyweight, these nanoparticles did not affect blood pressure and heart rate, and did not induce vasodilatation or vasoconstriction. PEGylation (PEG [polyethylene glycol]) was an indispensable step in development of a quantum dot probe for in vivo imaging, based on silica-shelled quantum dots. The non-PEGylated silica-shelled quantum dots possessed low colloidal stability in high-salt physiological fluids, accompanied by rapid aggregation in vivo. The conjugation of silica-shelled quantum dots with PEG1100 increased their stability and half-life in the circulation without significant enhancement of their size. In concentrations <2.5 nmol/kg bodyweight, these quantum dots did not affect the main physiological variables. It was possible to visualize capillaries, which makes this quantum dot probe appropriate for investigation of mediators of vasoconstriction, vasodilatation, and brain circulation in intact animals in vivo. The multimodal silica-shelled quantum dots allowed visualization of tumor tissue in an early stage of its development, using magnetic resonance imaging.Conclusion: The present study shows that the type and structure of organic/bioorganic shells of quantum dots determine their biocompatibility and are crucial for their application in imaging in vivo, due to the effects of the shell on the following properties: colloidal stability, solubility in physiological fluids, influence of the basic physiological parameters, and cytotoxicity.Keywords: quantum dot, organic shell, biocompatibility, in vivo imaging, two-photon excited fluorescent microscopy, magnetic resonance imagin

Wolman Disease and Liver Transplantation: Case Report

Wolman disease (WD) is an autosomal recessive lysosomal storage disorder, caused by a deficiency of lysosomal acid lipase. Affected infants usually develop abdominal distension, hepatosplenomegaly, steatorrhea, severe malabsorption and malnutrition, and adrenal calcification. Despite treatment attempts, the clinical outcome is poor. We report a case of a 4-month-old girl with WD, presented with a rapidly progressive liver failure and a liver transplantation was performed. The graft was retrieved from her mother. The postoperative period was uneventful. The child was in a satisfactory condition about 8 weeks after surgery and the enzyme replacement therapy (ERT) was started. During the treatment weight loss and vomiting persisted and a diarrhea started. Patient died due to severe respiratory failure seven weeks after starting ERT

Electro-assisted drug delivery in cancer using size-controlled long-circulating polymer nanoparticles

後日入力24th International Conference of the Society of Bulgarian Scientists

Assessment of renal function by 7T MRI and prototype of contrast agent - Experimental model

The present study shows that nitroxide derivative (carbamoyl-PROPXYL) is suitable 1H-MRI contrast probe for visualization of hypercholesterolemia-induced renal dysfunction in intact animals and clarifying the mechanism(s) of renal damage mediated by cholesterol. The probe was applied in a concentration, which was 3 times lower than the LD50 for intravenous administration in C57Bl/6 mice. Since the probe is excreted by kidneys, it could be considered harmless for mammalians in the selected dose and appropriate candidate for translational research. The data were compared with those, obtained by conventional 1H-MRI contrast agent Gd/DTPA for assessment of renal function in experimental animals and patients