Fluorescent polymeric microspheres are used in a wide range of biomedical and technological applications, including blood flow determination, screening, flow visualization, flow tracing, medical imaging, fluorescence microscopy and flow cytometry among others. Rhodamine 6G (R6G) is a lipophilic cationic dye, which is among the most stable organic fluorophores, and with a high quantum yield in fluorescence (absorption and emission) in the visible range (500-600 nm). It is mainly applied in laser technology, and also in fluorescent bioimage. In this work we present an efficient synthesis route to obtain Polyvinyl Alcohol/Polyvinyl Acetate (PVA/PVAc) spherical microparticles containing Rhodamine 6G in a concentration sufficient to exploit their fluorescent properties. The synthesis method comprises the suspension polymerization of Vinyl acetate (VAc) monomer in the presence of Rhodamine, followed by saponification. Microspheres loaded with 1.9% w / w of Rhodamine 6G were obtained. They presented good sphericity and a size distribution in the range of 20 to 1550 microns. The fluorescence intensity of the microspheres was measured by UV-Vis and fluorescence spectroscopy, and detected using an image-based experimental setup, respectively. The results obtained with these methodologies showed that our microspheres exhibit fluorescence and that they are quite detectable in water flows. However, the response of UV-Visible fluorescence and absorbance was affected by the presence of the PVA / PVAc polymer matrix.
RESUMEN En el presente trabajo se estudia el efecto de bebidas de consumo habitual como café, mate, té y agua mineral en la composición química de la superfície de un ionómero de vidrio comercial. Las muestras de ionómero se prepararon según las indicaciones del fabricante; se colocaron en las infusiones y se estacionaron en estufa de cultivo a 36 °C en el rango de 21 horas hasta 33 días. La evolución de la composición química a diferentes tiempos de almacenamiento se estudió mediante la técnica de Emisión de Rayos X inducida por Protones (PIXE). En todos los medios, excepto agua mineral, a tiempos largos se determinó la pérdida de Al, Si y Na, esto sugiere la disolución parcial de un aluminosilicato de Na. El perfil de concentración de Al y Si fue diferente en todos los medios, pero la relación Al:Si se mantuvo cercana a la unidad en todos los casos. El F se liberó asociado con Na en agua mineral, mientras que en el resto de bebidas su perfil de concentración infiere la formación de compuestros fluorados de Ca y La. Simultáneamente se observó la incorporación de Mn, Mg y Fe en la superficie del ionómero vítreo, no reportada anteriormente en la literatura.
Functionalized PVA microspheres are commonly used as drug carriers in the fields of pharmacy and medicine. With this aim, we obtained and test novel PVA-PVAc-AMPS sulfonated microspheres by free radical suspension polymerization of vinyl acetate (VAc) and 2-acrylamido-2-methyl-1-propanesulfonic sodium salt acid (AMPS), followed by saponification. The microspheres exhibited a porous core-shell structure with excellent sphericity, a mean size of 171 µm, and elasticity modulus comparable with commercial particles currently used in medical applications. Methylene blue (MB) which has shown similar adherence properties as the cytostatic drug doxorubicin was used as a model drug to study the drug loading/release characteristics of the sulfonated microspheres prepared in this work. 20.7 mg g-1 MB per gram of microspheres was the maximum adsorption capacity in two hours using UV-Vis absorption spectroscopy. The experimental data on adsorption were well described by the pseudo-second order kinetic model. The in vitro release profile of loaded MB microspheres showed rapid desorption in the first hour followed by slower MB release, reaching 8.6% elution at four hours. The diffusion process was found to be dominant in the MB desorption from the PVA-PVAc-AMPS microspheres.
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