PubMed · 15062387
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Roberto de Franchis, Emanuele Rondonotti, Carla Abbiati, Gizela Beccari, Clementina Signorelli. 2004. Small bowel malignancy.. https://doi.org/10.1016/j.giec.2003.10.006
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This study investigates the fluorogenic characteristics of the chitosan-genipin reaction for applications in microencapsulation research. Results showed that the chitosan-genipin reaction generated a colored and fluorescent product, with optimal excitation and emission wavelengths at 369 and 470 nm, respectively. Furthermore, it was found that reaction conditions affected the fluorescence intensity of the product. Mixture at the ratio of 4:1 (chitosan: genipin by weight) fluoresced the most. It also fluoresced stronger if the reaction occurred at higher temperature, with the intensity of 10.4 x 10(5) CPS at 37 degrees C, 5.9 x 10(5) CPS at 20 degrees C, and 2.5 x 10(5) CPS at 4 degrees C. As well, the fluorescence of the mixture developed gradually over time, attaining the emission maxima of 2.9 x 10(5), 7.6 x 10(5), and 10.0 x 10(5) CPS in 1, 6, and 18 h, respectively. Chitosan-coated alginate microcapsules were prepared without prior labeling, to which subsequent genipin treatment was applied in order to examine the potential of using genipin in microcapsule characterization. Chitosan bound to the alginate beads interacted with genipin, from which the resultant fluorescent signals allowed for clear visualization of the chitosan coating under confocal laser scanning microscopy. The relative fluorescence intensity across the chitosan membrane was found to be considerably higher than the controls (175 vs. 50). The membrane thickness measured was 29.2 +/- 7.3 microm. These findings demonstrate a convenient and effective way of characterizing chitosan-based microcapsules using genipin as a fluorogenic marker, a technique that will be useful in microcapsule research and other biomedical applications.
This study aimed to develop a simple UV spectrophotometric method for the analysis and the dissolution test of flunarizine in capsules. The UV absorbance was both measured directly and by the first derivative measurements at 254 and 268 nm, respectively. The developed methods were validated for their linearity, accuracy, precision, limit of detection (LOD) and limit of quantitation (LOQ) in comparison with the reported HPLC method. The UV spectrophotometric method illustrated excellent linearity (r2 > 0.9999) in the concentration range of 6-24 microg/mL. Precision (%R.S.D. < 1.50) and recoveries were good (%R > 99.62). The LOD of direct UV and first derivative measurements were 0.09 and 0.84 microg/mL, respectively, and the LOQ were 0.26 and 2.55 microg/mL, respectively. Results from the assay of flunarizine in capsules by the UV spectrophotometric methods, both direct and first derivative measurements were not significantly different from those of the HPLC method (P > 0.05). Additionally, the method was successfully used for the dissolution test of flunarizine capsule and was found to be reliable, simple, fast, and inexpensive.
A common limitation of using polymeric nanoparticles in aqueous suspension is due to their poor chemical and physical stability when conserved for a long time. Therefore, freeze drying of these colloidal systems is an alternative method to achieve long-term stability. Nanocapsules have thin and fragile shell structure, which may not resist to the stress of such process. The aim of this study is to investigate the formulation and process parameters in order to ensure the stability of polycaprolactone nanocapsules (PCL NC) by freeze drying. In this paper, we studied the freeze drying of PCL NC prepared by the emulsion-diffusion method and stabilized by poly(vinyl alcohol) (PVA). Different parameters have been tested throughout the freeze-thawing study including PVA and PCL concentration, cooling rate, cryoprotectant concentrations, nature of encapsulated oil and NC purification. On the other hand, nanocapsules have been freeze dried both before and after purification. Freeze dried purified PCL NC were characterized by particle size measurement, collapse temperature, T'g determination, scanning electron microscope observation, environmental scanning electron microscope imaging and residual humidity quantification. Finally, the effect of annealing on the NC stability and the sublimation rate has been well explored. The results suggest that PCL NC could be freeze dried without a cryoprotectant if the concentration of PVA stabilizer is sufficient (5%), while for the purified NC the addition of 5% of cryoprotectant seems to be necessary to ensure the stability of NC. The type of cryoprotectants had practically negligible effects on the size and the rehydration of freeze dried nanocapsules. The annealing process could accelerate the sublimation with the conservation of nanocapsules size.