Characterization techniques for studying the properties of nanocarriers for systemic delivery

Nanocarriers have attracted a huge interest in the last decade as efficient drug delivery systems and diagnostic tools. They enable effective, targeted, controlled delivery of therapeutic molecules while lowering the side effects caused during the treatment. The physicochemical properties of nanoparticles determine their in vivo pharmacokinetics, biodistribution and tolerability. The most analyzed among these physicochemical properties are shape, size, surface charge and porosity and several techniques have been used to characterize these specific properties. These different techniques assess the particles under varying conditions, such as physical state, solvents etc. and as such probe, in addition to the particles themselves, artifacts due to sample preparation or environment during measurement. Here, we discuss the different methods to precisely evaluate these properties, including their advantages or disadvantages. In several cases, there are physical properties that can be evaluated by more than one technique. Different strengths and limitations of each technique complicate the choice of the most suitable method, while often a combinatorial characterization approach is needed

Photodynamic activity of protoporphyrin IX in Harderian glands of Wistar rats: Monitoring by gland fluorescence

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)This paper presents results on Wistar rat Harderian glands photodegradation experimental study under visible light. Tests were conducted on 20 rats and a 632.8 nm He-Ne laser light was utilized for gland irradiation. The tissue degradation was evaluated by the microphotograph analysis, which demonstrated progressive disappearance of the acinus architecture and a increase in number of nuclei in the pyknotic form, characteristic for the cell degradation. At the same time, the intensities of initial fluorescence peaks at 636.2 nm and 705.8 nm, were diminished with increase in irradiation time and formation of a new peak with a maximum at 680 nm was observed. The systematic observation of the Harderian gland fluorescence spectrum evolutions in comparison with its tissue degradation factor demonstrated high occurrence of the result repetition for different animals even at very low light fluencies. This fact makes it possible to evaluate the tissue photodegradation level via monitoring of its fluorescence spectra as a function of the irradiation time and suggests that the Harderian glands provide an excellent experimental model for the study of the photodynamic process in vivo. Analysis of the Harderian gland fluorescence spectra evolution under light irradiation in comparison with that of protoporphyrin IX in solutions demonstrated that it is protoporphyrin IX responsible for gland fluorescence and photodynamic degradation. The formation of singlet oxygen under light irradiation of protoporphyrin IX solutions demonstrated that the principal mechanism of gland photodegradation is the Type II photodynamic. (C) 2012 Elsevier B.V. All rights reserved.1373236FAEP/UNICAMPFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Formation of cytotoxic intermediates in the course of photodecomposition of a nitroheterocyclic antiseptic quinifuryl

Phototoxicity of quinifuryl, 2-(5'-nitro-2'-furanyl)ethenyl-4-{n-[4'-(n,n-diethylamino)-1-methylbutyl]carbamoyl}quinoline, towards tumor cells has already been shown. Since no cytotoxicity of the final products of its photodecomposition was observed, we have supposed that cytotoxicity should be caused by reactive intermediates in the quinifuryl photolysis. We succeeded in detecting three species in the course of quinifuryl photolysis: singlet oxygen (1 A.), nitric oxide (NO) and superoxide anion (02 Singlet oxygen was detected by its specific phosphorescence in the course of the quinifuryl photoexcitation in both acetonitrile and aqueous solutions with lifetimes of 74.7 mu s and 3.5 mu s, respectively. The quantum yield of the (1)Delta g formation in water was 0.29 +/- 0.03. Nitric oxide release was detected by specific chemiluminescence of excited radical *NO2, formed in the reaction of NO with O-3. The yield of NO was 0.45 +/- 0.03 mol/mol of photodecomposed quinifuryl. The formation Of O-2(center dot-) was detected spectrophotometrically (epinephrine oxidation to adrenochrome) and by EPR (stable nitroxyl free radical formation). (c) 2006 Elsevier B.V. All rights reserved.184416719810