No abstract

The reaction of amines with pentafluorophenyl-substituted AB-porphyrins has been used to obtain different useful reactive groups for further functionalization and/or conjugation of these porphyrins to other substrates or materials. Porphyrins with alkenyl, alkynyl, amino, azido, epoxide, hydroxyl, and maleimido groups have thus been synthesized. For the first time such functionalized porphyrins have been conjugated to hyperbranched polyglycerol (hPG) as a biocompatible carrier system for photodynamic therapy (PDT) using the copper(i)-catalyzed 1,3-dipolar cycloaddition (CuAAC). The photocytotoxicity of selected porphyrins as well as of the porphyrin-hPG-conjugates has been assessed in cellular assays with human epidermoid carcinoma A-253 and squamous carcinoma CAL-27 cells. For several biomedical applications a release of the active drug and/or fluorescent dye is desired. Therefore, additionally, the synthesis of AB-porphyrins with cleavable linker moieties is presented, namely disulfide, cleavable in a reductive environment, and acetal linkers whose cleavage is pH triggered.

The antibacterial photodynamic activity of hyperbranched polyglycerol (hPG) loaded with zinc porphyrin photosensitizers and mannose units was investigated. hPG, with a M of 19.5 kDa, was functionalized with about 15 molecules of the photosensitizer {5,10,15-tris(3-hydroxyphenyl)-20-[4-(prop-2-yn-1-ylamino)tetrafluorophenyl]porphyrinato}-zinc(II) by using copper(I)-catalyzed 1,3-dipolar cycloaddition (CuAAC). These nanoparticle conjugates were functionalized systematically with increasing loadings of mannose in the range of approximately 20 to 110 groups. With higher mannose loadings (ca. 58-110 groups) the water-insoluble zinc porphyrin photosensitizer could thus be transferred into a water-soluble form. Targeting of the conjugates was proven in binding studies to the mannose-specific lectin concanavalin A (Con A) by using surface plasmon resonance (SPR). The antibacterial phototoxicity of the conjugates on Staphylococcus aureus (as a typical Gram-positive germ) was investigated in phosphate-buffered saline (PBS). It was shown that conjugates with approximately 70-110 mannose units exhibit significant antibacterial activity, whereas conjugates with approximately 20-60 units did not induce bacterial killing at all. These results give an insight into the multivalency effect in combination with photodynamic therapy (PDT). On addition of serum to the bacterial cultures, a quenching of this antibacterial phototoxicity was observed. In fluorescence studies with the conjugates in the presence of increasing bovine serum albumin (BSA) concentrations, protein-conjugate associations could be identified as a plausible cause for this quenching.