Metallic nanoparticles are important on several scientific, medical and industrial areas. The control of nanoparticles
characteristics has fundamental importance to increase the efficiency on the processes and applications in which they are
employed. The metallic nanoparticles present specific surface plasmon resonances (SPR). These resonances are related
with the collective oscillations of the electrons presents on the metallic nanoparticle. The SPR is determined by the
potential defined by the nanoparticle size and geometry.
There are several methods of producing gold nanoparticles, including the use of toxic chemical polymers. We already
reported the use of natural polymers, as for example, the agar-agar, to produce metallic nanoparticles under xenon lamp
irradiation. This technique is characterized as a “green” synthesis because the natural polymers are inoffensive to the
We report a technique to produce metallic nanoparticles and change its geometrical and dimensional characteristics using
a femtosecond laser. The 1 ml initial solution was irradiate using a laser beam with 380 mW, 1 kHz and 40 nm of bandwidth
centered at 800 nm.
The setup uses an Acousto-optic modulator, Dazzler, to change the pulses spectral profiles by introduction of several orders
of phase, resulting in different temporal energy distributions. The use of Dazzler has the objective of change the gold
nanoparticles average size by the changing of temporal energy distributions of the laser pulses incident in the sample. After
the laser irradiation, the gold nanoparticles average diameter were less than 15 nm.
The use of gold nanoparticles (AuNps) as the vehicle for 5-Aminolevulinic acid (ALA) delivery for photodynamic and photothermic plasmonic therapies is a promising approach, especially with the recent demonstration that this photosensitizer immobilization on the particle surface improves reactive oxygen species (ROS) formation, increasing its cytotoxicity. Gold nanorods (AuNRs) present an absorption spectrum shifted to 700 nm, within the tissue transparency window, which allows excitation of the nanoparticles situated deeper in the tissues. Here, we describe a new synthesis method that was applied to control the shape of the gold nanoparticles during its synthesis. To obtain ALA:AuNRs, precursor ALA:AuNps were irradiated by ultrashort laser pulses. The variation of the laser parameters such as pulse energy and duration and irradiation time was assessed. The relevant mechanisms are discussed.
Fluorescence technique appears very important for the diagnosis of cancer. Fluorescence detection has
advantages over other light-based investigation methods: high sensitivity, high speed, and safety.
Renal cell carcinoma (RCC) accounts for approximately 3% of new cancer incidence and mortality in the United States.
Unfortunately many RCC masses remain asymptomatic and nonpalpable until they are advanced. Diagnosis and
localization of early carcinoma play an important role in the prevention and curative treatment of RCC. Certain drugs or
chemicals such as porphyrin derivatives accumulate substantially more in tumors than normal tissues.
The autofluorescence of blood porphyrin of healthy and tumor induced male SCID mice was analyzed using
fluorescence and excitation spectroscopy. A significant contrast between normal and tumor blood could be established.
Blood porphyrin fluorophore showed enhanced fluorescence band (around 630 nm) in function of the tumor growth. This
indicates that either the autofluorescence intensity of the blood fluorescence may provide a good parameter for the "first
approximation" characterization of the tumor stage.
Development of cholesterol biosensors is of great importance in clinical analysis because the concentration of
cholesterol in blood is a fundamental parameter for the prevention and diagnosis of a number of clinical disorders such
as heart disease, hypertension and arteriosclerosis. In general, determination of cholesterol is based on
spectrophotometry; but this method involves complicated procedures and the cost is high because expensive enzyme
must be used in each assay.
We report here the observation, for the first time, of the enhancement of Europium-Tetracycline complex
emission in cholesterol solutions. This enhancement was initially observed with the addition of the enzyme cholesterol
oxidase, which produces H<sub>2</sub>O<sub>2</sub>, the agent driver of the Europium tetracycline complex, to the solution. However, it was
found that the enzyme is not needed to enhance the luminescence. A calibration curve was determined, resulting in an
easy-handling immobilization method with a cheap stable material. This method shows that the complex can be used as a
sensor to determine cholesterol in biological systems with good selectivity, fast response, miniature size, and
The tetracycline-europium (Tc-Eu) complex is known to show emission at 615 nm. On addition of hydrogen peroxide (HP), a strongly fluorescent complex is formed. In this paper it is reported that the europium fluorescence intensity is increased when urea hydrogen peroxide is added to the tetracycline-europium aqueous solution. It was conceived that this enhancement could be used to determine urea hydrogen peroxide (UHP) levels. This method is simple, practical, and relatively free of interference from coexisting substances, and it can be applied successfully to assess urea peroxide in biological samples, for example, on human whole blood. The values obtained for whole blood agree with the urea concentration variation verified in 50 patients, including 25 pre-dialysis, 15 dialysis subjects and 10 controls. This method is non invasive and can help in the identification of renal and cardiac diseases.
Compared with the traditional organic fluorescent materials, the lanthanide coordination compounds have a large variety of applications, for example glucose sensing, based on the luminescence enhancement of a lanthanide-tetracycline complex due to enzymatically generated H<sub>2</sub>O<sub>2</sub> at physiological glucose concentrations. It is known that the fluorescence is based on the energy-transfer from the ligand to the central lanthanide ion. The aim of this work was to study the optical properties of Europium, Erbium, Ytterbium, Holmium, Terbium and Neodymium tetracycline complexes. An increase in europium emission band was observed for the first time, with addition of urea peroxide in the solution. This method works at neutral pH and the luminescence was detected at visible lanthanides luminescence after a 10 min. incubation time of the samples.