title: PLA-PEG nanocapsules radiolabeled with 99mTechnetium-HMPAO: release properties and physicochemical characterization by atomic force microscopy and photon correlation spectroscopy.
abstract: The present work describes the preparation, characterization and labelling of conventional and surface-modified nanocapsules (NC) with 99m Tc-HMPAO. The size, size distribution and homogeneity were determined by photon correlation spectroscopy (PCS) and zeta potential by laser doppler anemometry. The morphology and the structural organization were evaluated by atomic force microscopy (AFM). The stability and release profile of the NC were determined in vitro in plasma. The results showed that the use of methylene blue induces significant increase in the encapsulation efficiency of 99m Tc-HMPAO, from 24.4 to 49.8% in PLA NC and 22.37 to 52.93% in the case of PLA-PEG NC (P<0.05) by improving the complex stabilization. The average diameter of NC calculated by PCS varied from 216 to 323 nm, while the average diameter determined by AFM varied from 238 to 426 nm. The AFM analysis of diameter/height ratios suggested a greater homogeneity of the surface-modified PLA-PEG nanocapsules compared to PLA NC concerning their flattening properties. The in vitro release of the 99m Tc-HMPAO in plasma medium was faster for the conventional PLA NC than for the surface-modified NC. For the latter, 60% of the radioactivity remained associated with NC, even after 12h of incubation. The results suggest that the surface-modified 99m Tc-HMPAO-PLA-PEG NC was more stable against label leakage in the presence of proteins and could present better performance as radiotracer in vivo.
authors.affiliation: Departamento de Análises Clínicas, Faculdade de Farmácia, Universidade Federal de Minas Gerais, Av. Antônio Carlos 6627, Belo Horizonte, MG 31270-901, Brazil.
authors.forename: Maira Alves
authors.initials: MA
authors.lastname: Pereira
authors.forename: Vanessa Carla Furtado
authors.initials: VC
authors.lastname: Mosqueira
authors.forename: José Mário Carneiro
authors.initials: JM
authors.lastname: Vilela
authors.forename: Margareth Spangler
authors.initials: MS
authors.lastname: Andrade
authors.forename: Gilson Andrade
authors.initials: GA
authors.lastname: Ramaldes
authors.forename: Valbert Nascimento
authors.initials: VN
authors.lastname: Cardoso
mesh_terms: D000465:Algorithms; D004355:Drug Stability; D005079:Excipients / Q000737:chemistry; D007773:Lactates / Q000737:chemistry*; D017078:Laser-Doppler Flowmetry / Q000379:methods; D008751:Methylene Blue / Q000737:chemistry; D018625:Microscopy, Atomic Force / Q000379:methods*; D015394:Molecular Structure; D053769:Nanocapsules / Q000737:chemistry*; D010316:Particle Size; D017785:Photons; D011092:Polyethylene Glycols / Q000737:chemistry*; D012995:Solubility; D013057:Spectrum Analysis / Q000379:methods*; D055672:Static Electricity; D019690:Technetium Tc 99m Exametazime / Q000737:chemistry / Q000493:pharmacokinetics*; D013997:Time Factors
chemical_list: D005079:Excipients; D007773:Lactates; D053769:Nanocapsules; C088513:poly(lactic acid-ethylene glycol); D019690:Technetium Tc 99m Exametazime; D011092:Polyethylene Glycols; D008751:Methylene Blue