Porphyrin–Coumarin Dyads: Investigation of Photophysical Properties and DNA Interactions

A Coumarin-Porphyrin FRET Break-Apart Probe for Heme Oxygenase-1

Heme oxygenase-1 (HO-1) is a vital enzyme in humans that primarily regulates free heme concentrations. The overexpression of HO-1 is commonly associated with cardiovascular and neurodegenerative diseases including atherosclerosis and ischemic stroke. Currently, there are no known chemical probes to detect HO-1 activity, limiting its potential as an early diagnostic/prognostic marker in these serious diseases. Reported here are the design, synthesis, and photophysical and biological characterization of a coumarin-porphyrin FRET break-apart probe to detect HO-1 activity, Fe-L1. We designed Fe-L1 to "break-apart" upon HO-1-catalyzed porphyrin degradation, perturbing the efficient FRET mechanism from a coumarin donor to a porphyrin acceptor fluorophore. Analysis of HO-1 activity using Escherichia coli lysates overexpressing hHO-1 found that a 6-fold increase in emission intensity at 383 nm was observed following incubation with NADPH. The identities of the degradation products following catabolism were confirmed by MALDI-MS and LC-MS, showing that porphyrin catabolism was regioselective at the α-position. Finally, through the analysis of Fe-L2, we have shown that close structural analogues of heme are required to maintain HO-1 activity. It is anticipated that this work will act as a foundation to design and develop new probes for HO-1 activity in the future, moving toward applications of live fluorescent imaging.

Zinc porphyrin-anthraquinonylimidazole supramolecular dyads

In this work, the synthesis and spectroscopic characterization of new zinc porphyrin-anthraquinone dyads is proposed. In particular, electron donor units based on zinc meso-tetraphenylporphyrin (ZnTPP) and zinc octaethylporphyrin (ZnOEP) have been coupled with differently substituted anthraquinones as acceptors. The quinone moiety was properly functionalized with imidazole, thus ensuring porphyrin complexation through zinc ion coordination. Accordingly, absorption and emission measurements demonstrated that the coordination occurred, and calculated binding constants were in the range 6.6 [Formula: see text] 10[Formula: see text]–3.9 [Formula: see text] 10[Formula: see text] M[Formula: see text]. Transient absorption spectroscopy for ZnTPP and ZnOEP dyads demonstrated that the electron transfer occurred, with the formation of the corresponding charge separated state, ZnTPP[Formula: see text]-AQ. Moreover, in ZnOEP complexes, a strong correlation between the chain length and flexibility with the charge separated state lifetime was observed.

Photophysical Properties of Fluorescent Self-Assembled Peptide Nanostructures for Singlet Oxygen Generation

In this work, a drug delivery system for perillyl alcohol based on the peptide self-assembly containing 3-(2-benzothiazolyl)-7-(diethylamino)coumarin (C6) as a fluorescent additive is obtained, and its photophysical characteristics as well as its release dynamics were studied by steady-state and time-resolved fluorescence spectroscopy. Results proved the dynamics of drug release from the peptide nanostructures and showed that the system formed by the self-assembled peptide and C6, along with perillyl alcohol, presents unique photophysical properties that can be exploited to generate singlet oxygen (1O2) upon irradiation, which is not achieved by the sole components. Through epifluorescence microscopy combined with time-correlated single photon counting fluorescence spectroscopy, the release mechanism was proven to occur upon peptide structure interconversion, which is controlled by environmental changes.

Nanomolar photodynamic activity of porphyrins bearing 1,4,7-trioxanonyl and 2-methyl-5-nitroimidazole moieties against cancer cells

Despite the continuous development of medicine, there is still a lack of effective and fully safe protocols for the treatment of neoplastic diseases. The drug-drug conjugates approach seems to give a chance to obtain more efficient molecules. New alkoxy and metronidazole substituted porphyrins were synthesized. Novel porphyrins were purified by flash column chromatography and characterized using NMR, MS, UV-Vis and HPLC. The Nuclear Magnetic Resonance study was performed to annotate experimentally observed ¹H NMR and ¹³C NMR signals of new compounds. The 2D NMR techniques such as ¹H-¹H COSY (Correlation Spectroscopy), ¹H-¹³C HSQC (Heteronuclear Single Quantum Correlation) and 1H-13C HMBC (Heteronuclear Multiple Bond Correlation) were used for the structure elucidation of the new compounds. In the range of 250-450 nm of the absorption spectra, the Soret band was observed, whereas the Q band was noted in the range of 500-650 nm. Compounds revealed a fluorescence quantum yield in the range 0.03-0.12. Singlet oxygen generation quantum yields up to 0.54 were determined. Electrochemical properties has also been studied. It has been noticed electropolymerization of compound bearing 5-nitroimidazole substituents. The photodynamic activity of the studied porphyrins against A549 and HEK001/HPV16 cancer cells were examined. The most active against A549 and HEK 001/HPV16 was light-excited trioxanonylporphyrin with the values of IC₅₀ equal to 0.49 μM and 50 nM respectively.