Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Three porphyrins, (5,10,15,20-tetra(3-hydroxyphenyl) porphyrin, 5-hexyl-10,20-bis(3-hydroxyphenyl)porphyrin and 5-hexyl-10,15,20-tris(3-hydroxyphenyl) porphyrin), with different amphiphilicities and equal singlet oxygen quantum yields in ethanol, were encapsulated into 50: 50 poly(lactide-co-glycolide), nanoparticles prepared by the emulsion/evaporation technique. A 2(2) factorial design was utilized to evaluate the influence of the porphyrin/polymer mass ratio and the percentage of ethanol in the aqueous phase on the size and zeta potential of the nanoparticles. Increasing both the amount of ethanol and the porphyrin/polymer ratio decreases the size and increases zeta potential for the photosensitizers studied, except for 5-hexyl-10,15,20-tri(3-hydroxyphenyl) porphyrin. Entrapment efficiency depended on the individual m-hydroxyphenylporphyrin and ranged from 69 to 97%. After 1.5 h incubation with m-hydroxyphenylporphyrin-loaded nanoparticles the percentages of intracellular uptake were the same for all porphyrins since the molecules are confined in the nanoparticles, hampering the interaction of the amphiphilic photosensitizers with the cellular membrane. All encapsulated porphyrins caused the same decrease of cell viability and always localized in the perinuclear region of the cells. Results show that these m-hydroxyphenylporphyrins, although with different amphiphilicities, have equal photodynamic efficacies.14862746286Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Health Research BoardConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)