POTENTIAL EFFICACY OF A DELTA-5-AMINOLEVULINIC ACID BIOADHESIVE GEL FORMULATION FOR THE PHOTODYNAMIC TREATMENT OF LESIONS OF THE GASTROINTESTINAL-TRACT IN MICE

delta fi-aminolevulinic acid (ALA) bioadhesive gel has been developed and evaluated in an in-vivo mouse model for photodynamic treatment of gastric cancer or Barrett's oesophagus. Four gels were tested: noveon AA-1, keltrol T, lutrol and blanose. An initial in-vitro study of gel adhesion showed that noveon and keltrol had longer polyethylene transi t times than lutrol and blanose. In-vivo assays indicated that protopo rphyrin IX was synthesized by gastric mucosa when ALA-noveon and ALA-l utrol were used (preferable results for noveon). Keltrol was eliminate d from the study after these investigations. Only ALA-noveon gel was r etained for studies of the relationship between ALA dose and fluoresce nce. Fluorescence measurements in-vivo showed that ALA concentration a nd application time had an influence on protoporphyrin IX synthesis. M aximum intensity (2091 counts s(-1)) was found with 2 mg mL(-1) ALA, a nd fluorescence intensities differed with application time, reaching 1 805 counts s(-1) after 240 min. ALA-noveon, showing good adhesion and enabling efficient diffusion of ALA at a pH < 6, was considered the be st formulation for maintaining ALA stability.