Besides, other PSs such as methylene blue (MB) and 2-devinyl-2-(1-hexyloxyethyl) pyropheophorbide (HPPH) conjugated to PAA nanogels through covalent bonds have also been reported by Kopelman's group. Furthermore, using the in vitro release profiles from chitosan loaded with 40 mM of HAL, one can estimate that after a residence time of 10 min on the esophageal wall, the amount of HAL delivered to the epithelium will be sufficient to perform fluorescence diagnosis of Barrett's esophagus following swallowing of this formulation. Chitosan has shown the best esophageal adhesion both in vitro and in vivo. In order to visualize the mucoadhesive properties of the formulations, a blue dye was incorporated as contrast agent. In the present study, different mucoadhesive gels including poloxamer 407, cross-linked polyacrylic acid, hydroxypropylmethylcellulose, sodium carboxymethylcellulose and chitosan have been evaluated with respect to bioadhesion to the esophagus using an ex vivo rat model and a clinical study on healthy volunteers. Therefore, the aim of this study was to develop a bioadhesive formulation loaded with hexylaminolevulinate (HAL) targeting the esophageal lining. In order to further improve this methodology, topical application of lipophilic 5-ALA esters to the esophagus could be advantageous in terms of fluorescence contrast and fluorescence intensity in the target tissue, adverse side effects, as well as application time. four-quadrant random biopsies which are taken every 1-2 cm of the esophagus for histopathological analysis. Once being established, this technique will be a potential alternative to today's standard diagnosis, i.e. Finally, in vitro release profiles were correlated to the in vivo results.įluorescence diagnosis following oral administration of 5-aminolevulinic acid (5-ALA) has shown to enable the sensitive visualization of intestinal metaplasia, dysplasia and early carcinoma in Barrett's esophagus. Furthermore, similarly to other hydrogels previously tested, such a formulation shows a more complete HAL release in vitro than conventional cream vehicles, and tends to increase porphyrin accumulation in nude mice skin. Rheological evaluation has shown that a 17.0% poloxamer 407 hydrogel with a sol-gel transition at 24.8 +/- 0.6 degrees C was the best formulation for easy application and optimal residence time. Therefore, a poloxamer 407 thermosetting gel, which is liquid at room temperature and becomes a semi-solid when in contact with the female genital tract, has been evaluated in vitro and in vivo. Hydrogels have shown to be more appropriate for the local delivery of these derivatives, but due to the limited long-term stability of such formulations at 25 degrees C, the development of an extemporaneously prepared hydrogel targeting CIN can be advantageous. Therefore, lipophilic 5-ALA esters, such as hexylaminolevulinate (HAL), have led to improved local bioavailability and therapeutic efficacy. In this context, topical application of 5-ALA to the cervix is beneficial due to the small necessary dose and its minimal side effects. 5-Aminolevulinic acid (5-ALA)-mediated photodynamic therapy has been proposed as an alternative, cervix-sparing treatment for cervical intraepithelial neoplasia (CIN).
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