Organization of Cooperating Aluminum Pairs in Ferrierite Evidenced by Luminescence Quenching.

We show that four cooperating Al atoms located at the two neighboring six-membered (6-MR) rings in the ferrierite framework can be readily discerned by luminescence studies. Thus, luminescent Zn(II) cations accommodated by one aluminum pair of the 6-MR ring can be effectively quenched by neighboring Co(II) ions stabilized by the second ring. Quenching occurs via the energy transfer mechanism and allows estimation of the critical radius of Zn(II)-Co(II) interactions. This points to the appropriate geometry and distance of the transition metal ions accommodated within zeolite, providing direct evidence of the four-aluminum atom arrangement in the ferrierite framework.

Structural, optical, and bioimaging characterization of carbon quantum dots solvothermally synthesized from o-phenylenediamine.

Carbon quantum dots as a novel type of carbon nanomaterials have attracted the attention of many researchers because of their unique optical, antibacterial, and anticancer properties as well as their biocompatibility. In this study, for the first time, carbon quantum dots were prepared from o-phenylenediamine dissolved in toluene by a solvothermal route. Subsequently, the prepared carbon quantum dots were encapsulated into polyurethane films by a swelling-encapsulation-shrink method. Analyses of the results obtained by different characterization methods (AFM, TEM, EDS, FTIR, photoluminescence, and EPR) indicate the significant influence of the precursor on structural, chemical, and optical properties. Antibacterial and cytotoxicity tests showed that these dots did not have any antibacterial potential, because of the low extent of reactive oxygen species production, and showed low dark cytotoxicity. By investigating the cellular uptake, it was established that these dots penetrated the HeLa cells and could be used as probes for bioimaging.

Photodynamic-active smart biocompatible material for an antibacterial surface coating.

Here we present a new effective antibacterial material suitable for a coating, e.g., surface treatment of textiles, which is also time and financially undemanding. The most important role is played by hydrophobic carbon quantum dots, as a new type of photosensitizer, produced by carbonization of different carbon precursors, which are incorporated by swelling from solution into various polymer matrices in the form of thin films, in particular polyurethanes, which are currently commercially used for industrial surface treatment of textiles. The role of hydrophobic carbon quantum dots is to work as photosensitizers upon irradiation and produce reactive oxygen species, namely singlet oxygen, which is already known as the most effective radical for elimination different kinds of bacteria on the surface or in close proximity to such modified material. Therefore, we have mainly studied the effect of hydrophobic carbon quantum dots on Staphylococcus aureus and the cytotoxicity tests, which are essential for the safe handling of such material. Also, the production of singlet oxygen by several methods (electron paramagnetic spectroscopy, time-resolved near-infrared spectroscopy), surface structures (atomic force microscopy and contact angle measurement), and the effect of radiation on polymer matrices were studied. The prepared material is easily modulated by end-user requirements.

Polystyrene and Poly(ethylene glycol)-b-Poly(ε-caprolactone) Nanoparticles with Porphyrins: Structure, Size, and Photooxidation Properties.

The transport of a photosensitizer to target biological structures followed by the release of singlet oxygen is a critical step in photodynamic therapy. We compared the (photo)physical properties of polystyrene nanoparticles (TPP@PS) of different sizes and self-assembled poly(ethylene glycol)-b-poly(ε-caprolactone) core/shell nanoparticles (TPP@PEG-PCL) with different lengths of copolymer blocks, both suitable for the transport of the tetraphenylporphyrin (TPP) photosensitizer. The singlet oxygen was formed inside both nanoparticles after irradiation with visible light. Its kinetics was controlled by the size of TPP@PS; its lifetime (τΔ) increased with increasing nanoparticle size (from 6.5 to 16 µs) because of hindered diffusion into the external aqueous environment, where it was quickly deactivated. Accordingly, the prolongation of the singlet oxygen-sensitized delayed fluorescence kinetics was found for TPP@PS of high size. The TPP@PEG-PCL self-assemblies allowed for enhanced oxygen diffusion, and the estimated low values of τΔ ≈ 3.7 µs were independent of the size of building blocks. The delayed fluorescence in oxygen-free conditions originating from triplet-triplet annihilation indicated a high mobility of TPP in the PCL core in comparison with fixed molecules in the PS matrix. Photooxidation of uric acid revealed the highest efficacy for TPP@PS of small sizes, whereas the largest TPP@PS exhibited the lowest activity, and the efficacy of TPP@PEG-PCL remained independent of the sizes of the building blocks.

Phosphinatophenylporphyrins tailored for high photodynamic efficacy.

The development of effective photosensitizers is particularly attractive for photodynamic therapy of cancer. Three novel porphyrin photosensitizers functionalized with phosphinic groups were synthesized and their physicochemical, photophysical, and photobiological properties were collected. Phosphinic acid groups (R1R2POOH) attached to the porphyrin moiety (R1) contain different R2 substituents (methyl, isopropyl, phenyl in this study). The presence of phosphinic groups does not influence absorption and photophysical properties of the porphyrin units, including the O2(1Δg) productivity. In vitro studies show that these porphyrins accumulate in cancer cells, are inherently nontoxic, however, exhibit high phototoxicity upon irradiation with visible light with their phototoxic efficacy tuned by R2 substituents on the phosphorus centre. Thus, phosphinatophenylporphyrin with isopropyl substituents has the strongest photodynamic efficacy due to the most efficient cellular uptake. We demonstrate that these porphyrins are attractive candidates for photodynamic applications since their photodynamic efficacy can be easily tuned by the R2 substituent.

Carbon Quantum Dots Modified Polyurethane Nanocomposite as Effective Photocatalytic and Antibacterial Agents.

Development of new types of antibacterial coatings or nanocomposites is of great importance due to widespread multidrug-resistant infections including bacterial infections. Herein, we investigated biocompatibility as well as structural, photocatalytic, and antibacterial properties of photoactive hydrophobic carbon quantum dots/polyurethane nanocomposite. The swell-encapsulation-shrink method was applied for production of these nanocomposites. Hydrophobic carbon quantum dots/polyurethane nanocomposites were found to be highly effective generator of singlet oxygen upon irradiation by low-power blue light. Analysis of conducted antibacterial tests on Staphyloccocus aureus and Escherichia coli showed 5-log bactericidal effect of these nanocomposites within 60 min of irradiation. Very powerful degradation of dye (rose bengal) was observed within 180 min of blue light irradiation of the nanocomposites. Biocompatibility studies revealed that nanocomposites were not cytotoxic against mouse embryonic fibroblast cell line, whereas they showed moderate cytotoxicity toward adenocarcinomic human epithelial cell line. Minor hemolytic effect of these nanocomposites toward red blood cells was revealed.

Singlet Oxygen Production and Biological Activity of Hexanuclear Chalcocyanide Rhenium Cluster Complexes [{Re6Q8}(CN)6]4- (Q = S, Se, Te).

Octahedral rhenium cluster complexes have recently emerged as relevant building blocks for the design of singlet oxygen photosensitizing materials toward biological applications such as blue-light photodynamic therapy. However, their singlet oxygen generation ability as well as biological properties have been studied only superficially. Herein we investigate in detail the singlet oxygen photogeneration, dark and photoinduced cytotoxicity, cellular uptake kinetics, cellular localization and in vitro photoinduced oxidative stress, and photodynamic cytotoxicity of the series of octahedral rhenium cluster complexes [{Re6Q8}(CN)6]4-, where Q = S, Se, Te. Our results demonstrate that the selenium-containing complex possesses optimal properties in terms of absorption and singlet oxygen productivity. These features coupled with the cellular internalization and low dark toxicity lead to the first photoinduced cytotoxic effect observed for a molecular [{M6Q8}L6] complex, making it a promising object for further study in terms of blue-light PDT.

Nanoscaled porphyrinic metal-organic frameworks: photosensitizer delivery systems for photodynamic therapy.

The photocytotoxic activity of porphyrin-containing materials including metal-organic frameworks (MOFs) has attracted ever increasing interest. We have developed a simple synthesis of hexagonal PCN-222/MOF-545 nanoparticles, which are powerful in inducing reactive oxygen species-mediated apoptosis of cancer cells upon visible light irradiation. The extent of the cytotoxic effect well correlates with the nanoparticle size and structural instability. High phototoxicity of the presented nanoparticles and their deactivation within several hours open up the door to possible applications in cancer therapy.

Tetra(3,4-pyrido)porphyrazines Caught in the Cationic Cage: Toward Nanomolar Active Photosensitizers.

Investigation of a series of tetra(3,4-pyrido)porphyrazines (TPyPzs) substituted with hydrophilic substituents revealed important structure-activity relationships for their use in photodynamic therapy (PDT). Among them, a cationic TPyPz derivative with total of 12 cationic charges above, below and in the plane of the core featured a unique spatial arrangement that caught the hydrophobic core in a cage, thereby protecting it fully from aggregation in water. This derivative exhibited exceptionally effective photodynamic activity on a number of tumor cell lines (HeLa, SK-MEL-28, A549, MCF-7) with effective concentrations (EC50) typically below 5 nM, at least an order of magnitude better than the EC50 values obtained for the clinically approved photosensitizers verteporfin, temoporfin, protoporphyrin IX, and trisulfonated hydroxyaluminum phthalocyanine. Its very low dark toxicity (TC50 > 400 µM) and high ability to induce photodamage to endothelial cells (EA.hy926) without preincubation suggest the high potential of this cationic TPyPz derivative in vascular-targeted PDT.

Photophysical characterisation and studies of the effect of palladium(II) 5,10,15,20-tetrakis-(4-sulfonatophenyl)-porphyrin on isometric contraction of isolated human mesenteric artery: good news for photodynamic therapy.

BACKGROUND: Considering the important roles of porphyrins in biological systems and their promising use in photodynamic therapy (PDT), the present work investigated the photophysical properties of palladium(II) 5,10,15,20-tetrakis-(4-sulfonatophenyl)-porphyrin (PdTSPP) and the effects of non-activated by light form of this porphyrin on contractile behaviour of isolated healthy endothelium-denuded human mesenteric arteries. METHODS: The photophysical characterisation of PdTSPP: the formation of the triplet states and the singlet oxygen were studied using laser flash photolysis. The effect of PdTSPP on the isometric contraction of artery segments from human mesentery was assessed utilising the precise method of artery isometric tension recording using Mulvany-Halpern wire myograph. RESULTS: We found that PdTSPP had a high lifetime of the triplet states τT=270µs. The calculated Stern Volmer rate constant kq=1.7×10(9)M(-1)s(-1) showed an efficient quenching by oxygen that indicated formation of singlet oxygen, O2((1)Δg). The photophysical parameters of PdTSPP, in particular its ability to generate O2((1)Δg) has defined it as an exceptionally interesting molecule for PDT. The results of the contraction study showed that PdTSPP applied in increasing concentrations (1-100µM) had no effect on the basal tone of human mesenteric artery under isometric condition. Furthermore, PdTSPP failed to potentiate or to attenuate the isometric contraction of the artery preparations precontracted with high extracellular potassium (42mM KCl) or with 1nM endothelin-1. CONCLUSIONS: The excellent photophysical properties of PdTSPP as well as the lack of an effect on the contractility of human vasculature in vitro characterise PdTSPP as a suitable compound for potential medical applications.

Water-soluble non-aggregating zinc phthalocyanine and in vitro studies for photodynamic therapy.

Newly synthesized zinc phthalocyanine bearing sixteen quaternized imidazolyl moieties on the periphery displays high water-solubility, lack of aggregation and high singlet oxygen quantum yield in water (ΦΔ > 0.33). The in vitro tests indicated excellent anticancer photodynamic activity (EC50 = 36.7 nM) and low dark toxicity to non-cancerous cells (TC50 = 395 µM).

Virucidal nanofiber textiles based on photosensitized production of singlet oxygen.

Novel biomaterials based on hydrophilic polycaprolactone and polyurethane (Tecophilic®) nanofibers with an encapsulated 5,10,5,20-tetraphenylporphyrin photosensitizer were prepared by electrospinning. The doped nanofiber textiles efficiently photo-generate O(2)((1)Δ(g)), which oxidize external chemical and biological substrates/targets. Strong photo-virucidal effects toward non-enveloped polyomaviruses and enveloped baculoviruses were observed on the surface of these textiles. The photo-virucidal effect was confirmed by a decrease in virus infectivity. In contrast, no virucidal effect was detected in the absence of light and/or the encapsulated photosensitizer.

Light-activated nanofibre textiles exert antibacterial effects in the setting of chronic wound healing.

The maintenance of an aseptic environment for chronic wounds is one of the most challenging tasks in the wound-healing process. Furthermore, the emergence of antibiotic-resistant bacterial strains is on the rise, rendering conventional treatments less effective. A new antibacterial material consisting of a polyurethane Tecophilic(™) nanofibre textile (NT) that was prepared by electrospinning and doped by a tetraphenylporphyrin (TPP) photosensitizer activated by visible light was tested for use in wound beds and bandages. In vitro experiments were performed to assess the antibacterial activity of the textile against three bacterial strains. Furthermore, the new textile was tested in 162 patients with chronic leg ulcers. A complete inhibition of in vitro growth of the three tested bacterial strains was observed on the surface of NTs that had been illuminated with visible light and was clinically demonstrated in 89 patients with leg ulcers. The application of the textiles resulted in a 35% decrease in wound size, as assessed via computer-aided wound tracing. Wound-related pain, which was estimated using a visual analogue scale, was reduced by 71%. The results of this trial reveal that the photoinactivation of bacteria through the photosensitized generation of short-lived, highly reactive singlet oxygen O(2) ((1) Δ(g) ) results in relatively superficial antibacterial effects in comparison with standard antiseptic treatment options. Thus, such treatment does not interfere with the normal healing process. This method therefore represents a suitable alternative to the use of topical antibiotics and antiseptics and demonstrates potentially broad applications in medicine.

Modulation of porphyrin binding to serum albumin by pH.

In this study, we show that the difference in acidity of functional groups in porphyrin photosensitizers provides a meaningful avenue to achieve differential localization and retention of porphyrins in tissues and cells, and in the end could be a positive factor in the photodynamic treatment of cancer (PDT). We have demonstrated that meso-tetraphenylporphyrin derivative with four phosphonate (bond P(double bond O)(bond OH)(2)) moieties exists in aqueous solutions mainly in four forms that differ by a degree of protonation of the porphyrin ring and ionization of the phosphonate group. It is shown that each porphyrin form has different affinities toward the model protein (bovine serum albumin, BSA). Thus pH of the medium significantly modulates the affinity of the phosphonate porphyrin toward BSA. At lower pH (pH 6.0), the phosphonate porphyrin and BSA form a complex with affinity constant of K(b)=6.9 x 10(5) M(-1), while at pH 7.0 the K(b)=6.1 x 10(5) M(-1). At pH 8.0 the association is significantly lower. Because cancerous cells have generally lower pH (pH approximately 6.9) compared to healthy cells (pH approximately 7.4), the pH of such cells could be a decisive factor for cellular retention of the porphyrin in the form of an associate with intracellular proteins. Moreover, we have also demonstrated that the protonation/deprotonation equilibria do not negatively affect the photophysical properties or ability of phosphonate porphyrin to generate singlet oxygen.