A porphycene-gentamicin conjugate for enhanced photodynamic inactivation of bacteria.

A novel photoantimicrobial agent, namely 2-aminothiazolo[4,5-c]-2,7,12,17-tetrakis(methoxyethyl)porphycene (ATAZTMPo-gentamicin) conjugate, has been prepared by a click reaction between the red-light absorbing 9-isothiocyanate-2,7,12,17-tetrakis(methoxyethyl)porphycene (9-ITMPo) and the antibiotic gentamicin. The conjugate exhibits submicromolar activity in vitro against both Gram-positive and Gram-negative bacteria (Staphylococcus aureus and Escherichia coli, respectively) upon exposure to red light and is devoid of any cytotoxicity in the dark. The conjugate outperforms the two components delivered separately, which may be used to enhance the therapeutic index of gentamicin, broaden the spectrum of pathogens against which it is effective and reduce its side effects. Additionally, we report a novel straightforward synthesis of 2,7,12,17-tetrakis(methoxyethyl) porphycene (TMPo) that decreases the number of steps from nine to six.

Acid- and hydrogen-bonding-induced switching between 22-π and 18-π electron conjugations in 2-aminothiazolo[4,5-c]porphycenes.

2-Aminothiazolo[4,5-c]porphycenes are a novel class of 22-π electron aromatic porphycene derivatives prepared by click reaction of porphycene isothiocyanates with primary and secondary amines with high potential as near-infrared theranostic labels. Herein, the optical and photophysical properties of 2-aminothiazolo[4,5-c]porphycenes have been studied, revealing a strong dependence on hydrogen bond donor solvents and acids. High hydrogen bond donor solvents and acids shift the absorption and fluorescence emission of 2-aminothiazolo[4,5-c]porphycenes to the blue due to a contraction of their aromatic system from 22-π to 18-π electrons. Finally, the aromatic shift has been successfully used to measure the pH using 2-aminothiazoloporphycene-labelled gold nanoclusters, paving the way for the use of these compounds as near infrared pH-sensitive probes.

Fluorescent polyene ceramide analogues as membrane probes.

Three ceramide analogues have been synthesized, with sphingosine-like chains containing five conjugated double bonds. Pentaene I has an N-palmitoyl acyl chain, while the other two pentaenes contain also a doxyl radical, respectively, at C5 (Penta5dox) and at C16 (Penta16dox) positions of the N-acyl chain. Pentaene I maximum excitation and emission wavelengths in a phospholipid bilayer are 353 and 478 nm, respectively. Pentaene I does not segregate from the other lipids in the way natural ceramide does, but rather mixes with them in a selective way according to the lipid phases involved. Fluorescence confocal microscopy studies show that when lipid domains in different physical states coexist, Pentaene I emission is higher in gel than in fluid domains, and in liquid-ordered than in liquid-disordered areas. Electron paramagnetic resonance of the pentaene doxyl probes confirms that these molecules are sensitive to the physical state of the bilayer. Calorimetric and fluorescence quenching experiments suggest that the lipids under study orient themselves in lipid bilayers with their polar moieties located at the lipid-water interface. The doxyl radical in the N-acyl chain quenches the fluorescence of the pentaene group when in close proximity. Because of this property, Penta16dox can detect gel-fluid transitions in phospholipids. The availability of probes for lipids in the gel phase is important in view of novel evidence for the existence of gel microdomains in cell membranes.

Straightforward access to spisulosine and 4,5-dehydrospisulosine stereoisomers: probes for profiling ceramide synthase activities in intact cells.

A stereoselective synthesis of spisulosine (ES285) and 4,5-dehydrospisulosine stereoisomers is described. Hydrozirconation of 1-pentadecyne with Schwartz reagent, followed by diastereocontrolled addition to L- or D-alaninal afforded the required 2-amino-1,3-diol framework. The resulting sphingoid bases revealed as excellent probes for the profiling of ceramide synthase activity in intact cells. Among the sphingoid bases described in this work, spisulosine (ES285), RBM1-77, and RBM1-73 were the most suitable ones because of their highest acylation rates. These molecules should prove useful to study the role of the different ceramide synthases and the resulting N-acyl (dihydro)ceramides in cell fate.

Smart Dual-Functionalized Gold Nanoclusters for Spatio-Temporally Controlled Delivery of Combined Chemo- and Photodynamic Therapy.

We report the preparation of gold nanoclusters (AuNCs) as a delivery vehicle for the clinically approved photodynamic and chemotherapeutic agents Protoporphyrin IX (PpIX) and doxorubicin (DOX), respectively, and their effect on tumor cells. DOX was attached to the gold nanoclusters through a singlet oxygen-cleavable linker and was therefore released after PpIX irradiation with red light, contributing, synergistically with singlet oxygen, to induce cell death. The doubly functionalized AuNCs proved more effective than a combination of individually functionalized AuNCs. Unlike free DOX, the photoactive nanosystem was non-toxic in the absence of light, which paves the way to introduce a spatiotemporal control of the anticancer therapy and could contribute to reducing the undesirable side effects of DOX.