In this work, we theoretically and experimentally deal with photoacoustic resolution enhancement by means of saturated modulation quenching. It is shown that experimental systems for resolution enhancement with saturated modulation quenching in fluorescence microscopy are not necessarily suited for photoacoustic modulation quenching. Here, we show that modulation quenching is not limited to fluorescent dyes but can be also applied to metallic nanoparticles. For modulation quenching in photoacoustic microscopy it is sufficient that the signal saturates with increasing excitation intensity.
QDs synthesized in aqueous medium and functionalized with polyethylene glycol were used as fluorescent probes. They label and monitor living healthy and cancer brain glial cells in culture. Physical-chemical characterization was performed. Toxicological studies were performed by in vivo short and long-term inhalation in animal models. Healthy and cancer glial living cells were incubated in culture media with highly controlled QDs. Specific features of glial cancer cells were enhanced by QD labelling. Cytoplasmic labelling pattern was clearly distinct for healthy and cancer cells. Labelled cells kept their normal activity for same period as non-labelled control samples.
Biopsies are conventionally performed in two dimensions. Histological slices in general present some micrometers in thickness, allowing that some molecular domains stay out of the resulting image. Thus the histopathological assay potentially is based on an incomplete set of information. The use of quantum dots as fluorescente probes allows the investigation of labelling pattern and biomarkers expression, along the three-dimensions of fresh histological slices, leading to more precise results. Present work show and discuss pattern and fluorescence intensity emission at the visible region obtained as a function of tissue thickness in histological (thickness(z)=7.6μm) breast cancer samples labeled with compact (7-10 nm) water soluble quantum dots. Series of 154 three-dimensional (3D) images were recorded from each tissue sample by laser scanning confocal microscopy, using 488 nm excitation.. In order to compare the results obtained, all the acquisition parameters were maintained constant. Results point to the possibility of more accurate histological diagnostics, once they clearly show distinct labeling patterns across sample thickness.
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