We describe the synthesis, characterization and photophysical properties of two new polycarboxylic photosensitizers. Owing to their structural design, these two compounds show water solubilities larger than natural carboxylic photosensitizers (e.g., protoporphyrin IX, hematoporphyrin, etc.) and also good singlet oxygen quantum yields. These compounds were tested as photo-antimicrobial agents against Staphylococcus aureus and Bacillus cereus strains. Results reveal that their photocytotoxicities are strongly dependent on their amphiphilic character and more precisely the number and position of the carboxylic acid and mesityl substituents