1%��7.9% on day 6 (Fig. 5). Figure 5 Larvicidal photosensitizing effect of C14 porphyrin. Larvicidal efficacy of C14 porphyrin The LC50 values of C14 on 3rd�C4th instar Ae. aegypti larvae showed an inverse relationship with the irradiation time (Fig. 6). After 1 h irradiation at a fluence rate of 1.0�C4.0 mW/cm2, the C14 LC50 was 0.46 ��M (Table 2), and selleck chemicals its value halved after 12 h irradiation. An additional overnight incubation in the dark of larvae already irradiated for 12 h further decreased the C14 LC50 to 0.11 ��M, corresponding to less than 1/4 of the value obtained after 1 h irradiation (Table 2). Figure 6 Influence of irradiation time on C14 porphyrin LC50 on Ae. aegypti larvae. Table 2 Median lethal concentrations (LC50) of C14 porphyrin.

Larvicidal efficacy of C14-loaded PFP This experiment was carried out to investigate the route of intake and site of action of porphyrin C14 in the mosquito larvae. Larvae incubated in clean spring water added with PFP pre-incubated with the photosensitizing agent (group A) showed 92.2% mortality after irradiation (Fig. 7). No statistical difference was observed between this mortality level and the 87.1% and 78.2% mortalities achieved, respectively, by a freshly prepared C14 solution containing untreated PFP and a 5 ��M C14 solution which had been incubated in the dark for 5 days before the introduction of untreated PFP (groups D and C). A lower mortality of 38.4% (p��0.002) was observed in larvae exposed to the porphyrin solution ��eluate��, i.e. the solution obtained by filtrating the PFP from its incubation medium (group B, see methods for details).

In this treatment group, the highest percentage of dying larvae (49.8%; p��0.002) was also observed, in contrast with all the other experimental groups where dying larvae amounted to 6.5%�C19.1%. These mortality data confirm that C14 was loaded onto the ��carrier�� PFP, and show that C14 efficiently exerts its photosensitizing effect when adsorbed onto the PFP. The incubation solution, after being deprived of the C14-loaded PFP, has a lower C14 concentration and causes less mortality to the larvae. Incubating a C14 solution for five days in the absence of PFP resulted in a larvicidal medium that was equally effective as freshly prepared C14 solutions or C14-loaded PFP, indicating that the lower activity observed in the ��eluate�� (group B) is not due to the degradation of the porphyrin in water.

Figure 7 Larvicidal activities of C14 porphyrin-incubated and non incubated PFP. When photoexcited at 450�C490 nm, C14 emits a red fluorescence which allowed for a qualitative assessment and comparison of the photosensitizer uptake by the larvae. In all the treated larvae, such fluorescence appeared to be limited to the midgut and the gastric caeca (Fig. 8). A strong GSK-3 fluorescence was observed in the midgut of larvae exposed to all the C14 treatments (experimental groups A, C and D; Fig.