B. M. Lacava

Phylloseptins: a novel class of anti-bacterial and anti-protozoan peptides from the Phyllomedusa genus.

Six novel peptides called phylloseptins (PS-1, -2, -3, -4, -5, and -6) showing anti-bacterial (PS-1) and anti-protozoan (PS-4 and -5) activities were isolated from the skin secretion of the Brazilian tree-frogs, Phyllomedusa hypochondrialis and Phyllomedusa oreades. Phylloseptins have a primary structure consisting of 19-21 amino acid residues (1.7-2.1 kDa). They have common structural features, such as a highly conserved N-terminal region and C-terminal amidation. Phylloseptin-1 (FLSLIPHAINAVSAIAKHN-NH2) demonstrated a strong effect against gram-positive and gram-negative bacteria (MICs ranging from 3 to 7.9 microM), without showing significant hemolytic activity (<0.6% at the MIC range) towards mammalian cells. Atomic force microscopy experiments indicated that the bacteriolytic properties of these peptides might be related to their disruptive action on the cell membrane, characterized by a number of bubble-like formations, preceding every cell lysis. PS-4 and PS-5 showed anti-protozoan activity with IC50 at about 5 microM for Trypanosoma cruzi.

Particle sizing of magnetite-based magnetic fluid using atomic force microscopy: A comparative study with electron microscopy and birefringence

Atomic force microscopy (AFM), transmission electron microscopy (TEM), and static magnetic birefringence (SMB) were used to unfold the particle size polydispersity profile of a magnetite-based magnetic fluid sample. The data obtained from different techniques were curve fitted using the lognormal distribution function, from which the mean particle diameter (Dm) and the standard deviation (σ) were obtained. In comparison to the TEM data, the AFM data show a reduction of Dm (about 20%) and an increase of σ (about 15%). In contrast, close agreement between the TEM and SMB data was found.

Nanoparticle sizing: a comparative study using atomic force microscopy, transmission electron microscopy, and ferromagnetic resonance

Abstract Atomic force microscopy (AFM), transmission electron microscopy (TEM), and ferromagnetic resonance (FMR) were used to unfold the nanoparticle size of a ferrofluid sample. Compared to TEM, the AFM method showed a nanoparticle diameter (Dm) reduction of 20% and standard deviation (σ) increase of 15%. The differences in Dm and σ were associated with the AFM tip and the nanoparticle concentration on the substrate.

Investigation of a magnetohyperthermia system efficacy

This study reports on the successful use of magnetic albumin nanosphere (MAN) with in vivo magnetohyperthermia (MHT) in a mouse Ehrlich tumor. Maghemite nanoparticles (8.9 nm average diameter) were encapsulated within MAN (73.0 nm average diameter). Ehrlich tumor obtained after implantation of tumor cells in the subcutaneous tissue of mice was used as a model throughout this study. MHT was performed with MAN (40 μL) containing 1.2 × 1015 particle/mL and 40 Oe amplitude ac magnetic field oscillating at 1 MHz. Animals not treated, treated with MAN, or exposed to the ac field were used as controls. Histopathological analysis was carried out after 2, 5, or 11 days of tumor implantation. We found that the MHT most efficient condition was obtained while applying the ac field protocol twice a day during three consecutive days. Further, in this ac field-treated group no proliferation cells were detected.

Atomic force microscopy and magnetization investigation of a water-based magnetic fluid

Abstract Atomic force microscopy (AFM) and magnetization measurements were used to unfold the particle-size polydispersity profile of a magnetite-based magnetic fluid sample. The sample preparation and the experimental conditions used to obtain the AFM image are described. The differences found in both the average diameter ( D m ) and particle-size dispersion ( σ ) values obtained from the two techniques are discussed.

Photoacoustic investigation of maghemite-based nanocomposite

Photoacoustic spectroscopy was used to investigate magnetic nanocomposites incorporating nanosized maghemite particles into styrene-divinylbenzene copolymer template. Typical photoacoustic features were observed in bands C, S and L in the wavelength region of 300-1000 nm. The relative intensity of band-C scaled with the nominal concentration of nanosized maghemite incorporated into the polymeric template whereas the lowest relative intensity of band-S was found in the sample in which the template polymerization took place in the presence of the highest polar-like reaction medium. X-ray diffraction and transmission electron microscopy were used to characterize the magnetic nanosized phase as maghemite, with average particle diameter of 6.9 nm (sample Est34), 7.0 nm (sample H30), and 7.9 nm (sample Em15).