title: Influence of nanostructure composition on its morphometric characterization by different techniques.
abstract: Morphometric characterization of nanoparticles is crucial to determine their biological effects and to obtain a formulation pattern. Determining the best technique requires knowledge of the particles being analyzed, the intended application of the particles, and the limitations of the techniques being considered. The aim of this article was to present transmission (TEM) and scanning (SEM) electron microscopy protocols for the analysis of two different nanostructures, namely polymeric nanoemulsion and poly(lactic-co-glycolic acid) (PLGA) nanoparticles, and to compare these results with conventional dynamic light scattering (DLS) measurements. The mean hydrodynamic diameter, the polydispersity index, and zeta potential of the nanostructures of polymeric nanoemulsion were 370.5 ± 0.8 nm, 0.133 ± 0.01, and -36.1 ± 0.15 mV, respectively, and for PLGA nanoparticles were 246.79 ± 5.03 nm, 0.096 ± 0.025, and -4.94 ± 0.86 mV, respectively. TEM analysis of polymeric nanoemulsion revealed a mean diameter of 374 ± 117 nm. SEM analysis showed a mean diameter of 368 ± 69 nm prior to gold coating and 448 ± 70 nm after gold coating. PLGA nanoparticles had a diameter of 131 ± 41.18 nm in TEM and 193 ± 101 nm in SEM. Morphologically, in TEM analysis, the polymeric nanoemulsions were spherical, with variable electron density, very few showing an electron-dense core and others an electron-dense surface. PLGA nanoparticles were round, with an electron-lucent core and electron-dense surface. In SEM, polymeric nanoemulsions were also spherical with a rough surface, and PLGA nanoparticles were round with a smooth surface. The results show that the "gold standards" for morphometric characterization of polymeric nanoemulsion and PLGA nanoparticles were, respectively, SEM without gold coating and TEM with negative staining.
authors.affiliation: Institute of Biological Sciences, University of Brasilia - (IB/UnB) 70.910-900, Brasilia/DF, Brazil.
authors.forename: Renata
authors.initials: R
authors.lastname: Carvalho Silva
authors.forename: Luis
authors.initials: L
authors.lastname: Alexandre Muehlmann
authors.forename: Jaqueline
authors.initials: J
authors.lastname: Rodrigues Da Silva
authors.forename: Ricardo
authors.initials: R
authors.lastname: de Bentes Azevedo
authors.forename: Carolina
authors.initials: C
authors.lastname: Madeira Lucci
mesh_terms: D057446:Hydrodynamics; D019344:Lactic Acid / Q000737:chemistry*; D053758:Nanoparticles / Q000737:chemistry / Q000648:ultrastructure*; D010316:Particle Size; D011100:Polyglycolic Acid / Q000737:chemistry*; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer
chemical_list: D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011100:Polyglycolic Acid; D019344:Lactic Acid
keywords: electron microscopy; morphometry; nanoemulsion; nanoparticles