Inorganic Chemistry, Vol.56, No.12, 7210-7216, 2017
Synthesis and Photophysical and Photocatalytic Properties of a Highly Fluorinated and Durable Phthalocyanine-Peptide Bioconjugate for Potential Theranostic Applications
The functionalized, asymmetric fluoro-fluoroalkyl scaffold F48H2COOHPcZn (3) was used to prepare F48H7COOPcZn-6-amino-hexanoate-CTVALPGGYVRVC (5), a Pep42 peptide bioconjugate envisioned for photodynamic therapy, which can specifically target the GRP78 chaperone protein overexpressed and exclusively localized on some cancer cell surfaces. The analogous F48H7COOHPcCu (4) has also been prepared, and its single-crystal X-ray structure was elucidated. Despite reduced steric hindrance relative to the nonfunctionalized, single-site complexes of the F64PC scaffold, no aggregation was detected in solution via UV-vis spectroscopy, for either 3, 4, or 5, consistent with the lack of pi stacking observed for the crystalline 4. The 6-aminohexanoic acid-Pep42 moiety diminishes the fluorescence efficiency of 5, relative to 3, but for singlet oxygen (O-1(2)) generation, photochemical hydroperoxidation of beta-(-)-citronellol using 5 and 3 occurs with comparable substrate turnover efficiency, albeit at a slower initial triplet oxygen uptake for 5. The bioconjugate 5 is durable; it does not decompose under O-1(2) photoreaction conditions. These results suggest a synthetic coupling pathway for obtaining diverse biotargeting polypeptide-fluorinated phthalocyanine bioconjugates of potential utility as both fluorescence reporters and photocatalysts and highlight the importance of fluorinated scaffolds for generating chemically resilient, catalytic, theranostic materials.