Effects of pluronic silica nanoparticles on the photophysical and photodynamic therapy behavior of triphenyl-p-phenoxy benzoic acid metalloporphyrins

5, 10, 15, Triphenyl-20-p-phenoxy benzoic acid porphyrins (P) containing Zn (ZnP), Ga (GaP), and Si (SiP) were synthesized and conjugated to pluronic-silica (PluS) nanoparticles (NPs) where the fluorescence and singlet oxygen generating behavior of the porphyrins were investigated. The highest singlet oxygen quantum yield (Φ_Δ) was obtained for ZnP. When the porphyrins were conjugated to the PluS NPs, the Φ_Δ was quenched and fluorescence was enhanced. The pore size of the NPs upon conjugation decreased from 18.9 nm for PluS NPs to 2.4 nm (for ZnP as an example) as determined by applying the Brunauer–Emmett–Teller method. The porphyrin complexes and their conjugates were tested for their photodynamic therapy (PDT) activity on MCF-7 breast cancer cells. It was found that ZnP and its conjugate showed the highest PDT activity. The p > 0.05 indicated that ZnP is significantly different than GaP and SiP.     

Synthesis of phenothiazine-functionalized porphyrins with high fluorescent quantum yields

Two porphyrins with oligo-phenothiazine arms have been synthesized by a combination of Heck and Adler reaction, and their photophysical properties have been investigated by absorption and steady-state fluorescence spectroscopy. It is found that the excitation energy transfer occurs from the phenothiazine units to the porphyrin core, and that the porphyrins can emit intense red light with high fluorescent quantum yields.     

Improving singlet oxygen generating abilities of phthalocyanines: aluminum tetrasulfonated phthalocyanine in the presence of graphene quantum dots and folic acid

Glutathione-capped graphene quantum dots (GQDs@GSH) were covalently linked to folic acid (FA). Aluminum tetrasulfonated phthalocyanine (ClAlTSPc) was then adsorbed on the GQDs@GSH-FA conjugate to form GQDs@GSH-FA/ClAlTSPc or on GQDs@GSH and pristine GQDs alone to form GQDs@GSH/ClAlTSPc and GQDs/ClAlTSPc, respectively. We report for the first time on the photophysicochemical behavior of the resulting nanoconjugates. The fluorescence quantum yields of pristine GQDs, GQDS@GSH, or GQDs@GSH-FA conjugate were quenched upon non-covalent interaction (π–π) with ClAlTSPc. There was an increase in triplet quantum yields from 0.38 for ClAlTSPc alone to 0.60, 0.75, and 0.73 when ClAlTSPc was linked to pristine GQDs, GQDs@GSH, and GQDs@GSH-FA, respectively. The singlet oxygen quantum yields also increased from 0.37 for ClAlTSPc alone to 0.42 (for ClALTSPc with pristine GQDs), 0.52 (for ClAlTSPc with GQDs@GSH), and 0.54 (for ClAlTSPc with GQDs@GSH-FA). Thus, the present work may lead to a new generation of carbon-based nanomaterial photodynamic therapy agents with overall performance superior to conventional agents in terms of singlet oxygen generation, water dispersibility, and biocompatibility.     

双光子诱导产生单重态氧的三重态光敏剂的研究

自2001年以来,双光子敏化产生单重态氧的三重态光敏剂的研究取得了一定的进展。双光子三重态光敏剂对肿瘤组织的近红外激光和红外激光的光动力治疗作用具有广阔的应用前景。本文重点分析了近些年已报道的双光子三重态光敏剂种类,如疏水性、水溶性等不同的敏化剂;介绍了可以根据分子的激发态性质、利用化学手段对双光子三重态敏化剂的性质以及光敏产生单重态氧的量子产率进行调控;概括了双光子三重态敏化剂的相对和绝对双光子横截面的测量方法;总结了双光子三重态敏化剂发展中面临的一些关键问题,并展望了双光子三重态敏化剂的发展方向。     

Immobilization of porphyrins in poly(hydroxymethylsiloxane)

Three tetracationic porphyrins differing in the position of charged nitrogen atoms on the peripheral substituents — 5,10,15,20-tetrakis(N-methylpyridinium-4-yl)porphyrin (TMPyP4), 5,10,15,20-tetrakis(N-methylpyridinium-2-yl)porphyrin (TMPyP2), 5,10,15,20-tetrakis(4-trimethylammoniophenyl) porphyrin (TMAPP), and hydrophobic 5,10,15,20-tetraphenylporphyrin (TPP), were immobilized by adsorption and encapsulation in poly(hydroxymethylsiloxane) (PHOMS). The so prepared porphyrin-PHOMS composites were characterized by porosimetry, scanning electron microscopy, fluorescence and diffuse reflectance UV-VIS spectroscopy. It was found that porphyrins are immobilized in the PHOMS matrix in the free base monomer form Their irradiation produced singlet oxygen O₂(¹Δ_g) with the lifetime of 10–30 μs.     

Solvent effects in molecular complexes of porphyrins and metalloporphyrins

The apparent stability constants for porphyrin and metalloporphyrin complexes with an electron acceptor have been determined in mixed solvents. The variation of the apparent stability with solvent composition is evaluated in terms of solvation of the complex and reactant species and in terms of the exclusion of the solvent from the solvation sheath of the reactants, according to the equilibrium AS _a +DS _b =CS _x +yS.     

Absolute quantum yield measurements for the formation of oxygen atoms after UV laser excitation of SO2 at 222-4 nm

The dynamics of formation of oxygen atoms after UV photoexcitation of SO₂ in the gas-phase was studied by pulsed laser photolysis-laser-inducedfluorescence ‘pump-and-probe’ technique in a flow reactor. SO₂ at room-temperature was excited at the KrCl excimer laser wavelength (222.4 nm) and O(³P_j) photofragments were detected under collision-free conditions by vacuum ultraviolet laser-induced fluorescence. The use of narrow-band probe laser radiation, generated viaresonant third-order sum-difference frequency conversion of dye laser radiation in Krypton, allowed the measurement of the nascent O(³P_j=2,1,0) fine-structure state distribution:n _j=2/n_j=1/n_j=0 = (0.88 ± 0.02)/(0.10 ± 0.01)/(0.02 ± 0.01). Employing NO₂photolysis as a reference, a value of Φ₀(³P) = 0.13 ± 0.05 for the absolute O(³P) atom quantum yield was determined. The measured O(³P) quantum yield is compared with the results of earlier fluorescence quantum yield measurements. A suitable mechanism is suggested in which the dissociation proceeds via internal conversion from high rotational states of the initially excited SO₂(~C¹B₂ (1, 2, 2) vibronic level to nearby continuum states of the electronic ground state.     

Singlet Oxygen‐Induced Furan Oxidation for Site‐Specific and Chemoselective Peptide Ligation

A novel chemoselective ligation methodology has been developed for the facile construction of peptide‐based fluorescent probes. Furan‐containing peptides were activated by singlet oxygen and covalently engaged by nitrogen nucleophiles to yield stable conjugates. Singlet oxygen was compatible with sensitive amino acid residues within the peptides and a range of fluorophores, bearing different functionalities, were successfully incorporated, illustrating the broad scope of the developed strategy.     

Characterization and physicochemical studies of the conjugates of graphene quantum dots with differently charged zinc phthalocyanines

Unsubstituted zinc phthalocyanine (ZnPc), 2,9,16,23-tetrakis[4-(N-methylpyridyloxy)]-phthalocyanine (ZnTPPcQ) and Zn tetrasulfo phthalocyanine (ZnTSPc) were non-covalently (electrostatic and/or π–π interaction) attached to graphene quantum dots (GQDs) to form GQDs-Pc nanoconjugates. Relative to Pcs alone, the presence of GQDs improved the triplet quantum yields with the following values: GQDs-ZnPc (0.73), GQDs-ZnTPPcQ (0.76) and GQDs-ZnTSPc (0.67). Respective Förster resonance energy transfer (FRET) efficiencies were calculated to be 0.81, 0.80 and 0.28. However, singlet oxygen generating abilities of the as-synthesized nanoconjugates were relatively low due to the screening effect of GQDs and quenching in water. This study shows that, the type of Pc, loading and solvent used are among the vital properties to consider when constructing GQD-nanoconjugate systems with optimal triplet quantum yield properties and investigation of their physicochemical properties.     

Spectroscopic Investigations of Porphyrin-TiO2 Nanoparticles Complexes

This study presents the spectral characterization of TiO₂ nanoparticles (NPs) functionalized with three porphyrin derivatives: 5,10,15,20-(Tetra-4-aminophenyl) porphyrin (TAPP), 5,10,15,20-(Tetra-4-methoxyphenyl) porphyrin (TMPP), and 5,10,15,20-(Tetra-4-carboxyphenyl) porphyrin (TCPP). UV-Vis absorption and Fourier transform infrared spectroscopy–attenuated total reflection (FTIR-ATR) spectroscopic studies of these porphyrins and their complexes with TiO₂ NPs were performed. In addition, the efficiency of singlet oxygen generation, the key species in photodynamic therapy, was investigated. UV-Vis absorption spectra of the NPs complexes showed the characteristic bands of porphyrins. These allowed us to determine the loaded porphyrins on TiO₂ NPs functionalized with porphyrins. FTIR-ATR revealed the formation of porphyrin-TiO₂ complexes, suggesting that porphyrin adsorption on TiO₂ may involve the pyrroles in the porphyrin ring, or the radicals of the porphyrin derivative. The quantum yield for singlet oxygen generation by the studied porphyrin complexes with TiO₂ was higher compared to bare porphyrins for TAPP and TMPP, while for the TCPP-TiO₂ NPs complex, a decrease was observed, but still maintained a good efficiency. The TiO₂ NPs conjugates can be promising candidates to be tested in photodynamic therapy in vitro assays.     

Supramolecular Control of Singlet Oxygen Generation

Singlet oxygen (¹O₂) is the excited state electronic isomer and a reactive form of molecular oxygen, which is most efficiently produced through the photosensitized excitation of ambient triplet oxygen. Photochemical singlet oxygen generation (SOG) has received tremendous attention historically, both for its practical application as well as for the fundamental aspects of its reactivity. Applications of singlet oxygen in medicine, wastewater treatment, microbial disinfection, and synthetic chemistry are the direct results of active past research into this reaction. Such advancements were achieved through design factors focused predominantly on the photosensitizer (PS), whose photoactivity is relegated to self-regulated structure and energetics in ground and excited states. However, the relatively new supramolecular approach of dictating molecular structure through non-bonding interactions has allowed photochemists to render otherwise inactive or less effective PSs as efficient ¹O₂ generators. This concise and first of its kind review aims to compile progress in SOG research achieved through supramolecular photochemistry in an effort to serve as a reference for future research in this direction. The aim of this review is to highlight the value in the supramolecular photochemistry approach to tapping the unexploited technological potential within this historic reaction.     

Theoretical study on photooxidation mechanism of ruthenium complex [Ru(II)‐(bpy)2(TMBiimH2)]2+ with molecular oxygen

Photoinduced reactions of ruthenium complexes with molecular oxygen have attracted a lot of experimental attention; however, the reaction mechanism remains elusive. In this work, we have used the density functional theory method to scrutinize the visible‐light induced photooxidation mechanism of the ruthenium complex [Ru(II)‐(bpy)₂(TMBiimH₂)]²⁺ (bpy: 2, 2‐bipyridine and TMBiimH₂: 4, 5, 4, 5‐tetramethyl‐2, 2‐biimidazole) initiated by the attack of molecular oxygen. The present computational results not only explain very well recent experiments, also provide new mechanistic insights. We found that: (1) the triplet energy transfer process between the triplet molecular oxygen and the metal‐ligand charge transfer triplet state of the ruthenium complex, which leads to singlet molecular oxygen, is thermodynamically favorable; (2) the singlet oxygen addition process to the S₀ ruthenium complex is facile in energy; (3) the chemical transformation from endoperoxide to epidioxetane intermediates can be either two‐ or one‐step reaction (the latter is energetically favored). These findings contribute important mechanistic information to photooxidation reactions of ruthenium complexes with molecular oxygen. © 2016 Wiley Periodicals, Inc.     

One- and two-photon singlet oxygen generation with new fluorene-based photosensitizers.

The spectral properties of new fluorene-based photosensitizers for efficient singlet oxygen production are investigated at room temperature and 77 K. Two-photon absorption (2PA) cross-sections of the fluorene derivatives are measured by the open aperture Z-scan method. The quantum yields of singlet oxygen generation under one- and two-photon excitation (phi(delta) and 2PAphi(delta), respectively), are determined by the direct measurement of singlet oxygen luminescence at approximately 1270 nm. The values of phi(delta) are independent of excitation wavelength, ranging from 0.6-0.9. The singlet oxygen quantum yields under two-photon excitation are 2PAphi(delta) approximately 1/2 phi(delta), indicating that the two processes exhibit the same mechanism of singlet oxygen production, independent of the mechanism of photon absorption.     

Aza‐BODIPY Derivatives: Enhanced Quantum Yields of Triplet Excited States and the Generation of Singlet Oxygen and their Role as Facile Sustainable Photooxygenation Catalysts

A new series of aza‐BODIPY derivatives ( 4 a – 4 c , 5 a , c , and 6 b , c ) were synthesized and their excited‐state properties, such as their triplet excited state and the yield of singlet‐oxygen generation, were tuned by substituting with heavy atoms, such as bromine and iodine. The effect of substitution has been studied in detail by varying the position of halogenation. The core‐substituted dyes showed high yields of the triplet excited state and high efficiencies of singlet‐oxygen generation when compared to the peripheral‐substituted systems. The dye 6 c , which was substituted with six iodine atoms on the core and peripheral phenyl ring, showed the highest quantum yields of the triplet excited state (Φ_T=0.86) and of the efficiency of singlet‐oxygen generation (Φ_Δ=0.80). Interestingly, these dyes were highly efficient as photooxygenation catalysts under artificial light, as well as under normal sunlight conditions. The uniqueness of these aza‐BODIPY systems is that they are stable under irradiation conditions, possess strong red‐light absorption (620–680 nm), exhibit high yields of singlet‐oxygen generation, and act as efficient and sustainable catalysts for photooxygenation reactions.     

Synthesis, excitation energy transfer and singlet oxygen photogeneration of covalently linked N-confused porphyrin-porphyrin and Zn(II) porphyrin dyads

Dyads of a N-confused porphyrin (NCP) moiety covalently linked to a porphyrin free-base (H₂P) or a zinc(II) porphyrinate (ZnP) moiety via a flexible alkyl chain of variable length have been synthesized. Photoluminescence study demonstrated an efficient excitation energy transfer from H₂P/ZnP moiety to the NCP moiety. Measurement of the near-IR emission of singlet oxygen produced by these dyads via photosensitization showed that the NCP-ZnP dyads (Ф_Δ = (0.61-0.65) ± 0.13) were better ¹O₂ generators than the NCP-P dyads (Ф_Δ = (0.36-0.41) ± 0.08).     

Singlet oxygen‐induced protein aggregation: Lysozyme crosslink formation and nLC‐MS/MS characterization

Singlet molecular oxygen (¹O₂) has been associated with a number of physiological processes. Despite the recognized importance of ¹O₂‐mediated protein modifications, little is known about the role of this oxidant in crosslink formation and protein aggregation. Thus, using lysozyme as a model, the present study sought to investigate the involvement of ¹O₂ in crosslink formation. Lysozyme was photochemically oxidized in the presence of rose bengal or chemically oxidized using [¹⁸O]‐labeled ¹O₂ released from thermolabile endoperoxides. It was concluded that both ¹O₂ generating systems induce lysozyme crosslinking and aggregation. Using SDS‐PAGE and nano‐scale liquid chromatography coupled to electrospray ionization mass spectrometry, the results clearly demonstrated that ¹O₂ is directly involved in the formation of covalent crosslinks involving the amino acids histidine, lysine, and tryptophan.     

Selective oxidation of ethylbenzene catalyzed by fluorinated metalloporphyrins with molecular oxygen

This paper reported the oxidation of ethylbenzene catalyzed by fluorinated metalloporphyrins under mild conditions without any additives.The results showed that the cobalt(Ⅱ)(5,10,15,20-tetrakis(pentafluorophenyl))porphyrin was the best catalyst among the fluorinated metalloporphyrins.The conversion of ethylbenzene reached 38.6%,the selectivity to acetophenone reached 94.0%,and the turnover number is 2719 under the optimal conditions.     

Ab initio study of exciton transfer dynamics from a core–shell semiconductor quantum dot to a porphyrin-sensitizer

The observed resonance energy transfer in nanoassemblies of CdSe/ZnS quantum dots and pyridyl-substituted free-base porphyrin molecules [Zenkevich et al., J. Phys. Chem. B 109 (2005) 8679] is studied computationally by ab initio electronic structure and quantum dynamics approaches. The system harvests light in a broad energy range and can transfer the excitation from the dot through the porphyrin to oxygen, generating singlet oxygen for medical applications. The geometric structure, electronic energies, and transition dipole moments are derived by density functional theory and are utilized for calculating the Förster coupling between the excitons residing on the quantum dot and the porphyrin. The direction and rate of the irreversible exciton transfer is determined by the initial photoexcitation of the dot, the dot–porphyrin coupling and the interaction to the electronic subsystem with the vibrational environment. The simulated electronic structure and dynamics are in good agreement with the experimental data and provide real-time atomistic details of the energy transfer mechanism.     

The nature of molecular oxygen binding and activation in Mn-O2 complex

Non-empirical calculations of CASSCF energies, electric dipole moments, Einstein coefficients, matrix elements of the operator of spin-orbital interaction between states of different multiplicity in a model complex ^6,8[Mn-O₂] of C _2v symmetry have been made in 3-21G, 6-31G, 6-31G** basis sets. The crosssections of the potential energy surface (PES) of the ground and excited states were built. It is found that oxygen bonding to manganese is possible when excited atoms of manganese collide with molecular oxygen, singlet oxygen with Mn[⁶ S _5/2] atoms, or in a close contact O₂[X³Σ _g ^? ] + Mn[⁶ S _5/2] and is determined by charge transfer states ^6,8CTS(Mn⁺O ₂ ^? ). Mechanisms of singlet oxygen activation/deactivation are determined by a considerably increased probability of electric dipole transitions b ¹Σ _g ⁺ ?a ¹Δ_g, a ¹Δ_g?X³Σ _g ^? , b ¹Σ _g ⁺ ?X³Σ _g ^? induced in oxygen in the collision process.