PLGA-PVA-PEG Single Emulsion Method as a Candidate for Aminolevulinic Acid (5-ALA) Encapsulation: Laboratory Scaling Up and Stability Evaluation.

One of the most widely used molecules used for photodynamic therapy (PDT) is 5-aminolevulinic acid (5-ALA), a precursor in the synthesis of tetrapyrroles such as chlorophyll and heme. The 5-ALA skin permeation is considerably reduced due to its hydrophilic characteristics, decreasing its local bioavailability and therapeutic effect. For this reason, five different systems containing polymeric particles of poly [D, L-lactic-co-glycolic acid (PLGA)] were developed to encapsulate 5-ALA based on single and double emulsions methodology. All systems were standardized (according to the volume of reagents and mass of pharmaceutical ingredients) and compared in terms of laboratory scaling up, particle formation and stability over time. UV-VIS spectroscopy revealed that particle absorption/adsorption of 5-ALA was dependent on the method of synthesis. Different size distribution was observed by DLS and NTA techniques, revealing that 5-ALA increased the particle size. The contact angle evaluation showed that the system hydrophobicity was dependent on the surfactant and the 5-ALA contribution. The FTIR results indicated that the type of emulsion influenced the particle formation, as well as allowing PEG functionalization and interaction with 5-ALA. According to the 1H-NMR results, the 5-ALA reduced the T1 values of polyvinyl alcohol (PVA) and PLGA in the double emulsion systems due to the decrease in molecular packing in the hydrophobic region. The results indicated that the system formed by single emulsion containing the combination PVA-PEG presented greater stability with less influence from 5-ALA. This system is a promising candidate to successfully encapsulate 5-ALA and achieve good performance and specificity for in vitro skin cancer treatment.

A strategy for the targeting of photosensitizers. Synthesis, characterization, and photobiological property of porphyrins bearing glycodendrimeric moieties.

This paper describes the conception, synthesis, and characterization of new tetrapyrrolic chromophores bearing glycodendrimeric moieties inducing a potential increase of tumor targeting by a cluster effect. Two families of monoglycodendrimeric photosensitizers bearing three glycosyl units were designed, prepared with an acceptable overall efficiency and characterized by NMR, UV-visible, and fluorescence spectroscopies. The polarity and log P were evaluated by HPLC and the stir-flask method, respectively. The in vitro photoefficiency against two human tumor cell lines was assessed. The presence of the glycodendrimeric group does not appear to increase the tumor in vitro targeting.

Spectroscopic behavior of some A(3)B type tetrapyrrolic complexes in several organic solvents and micellar media.

The paper presents spectral studies of some unsymmetrical A(3)B tetrapyrrolic, porphyrin-type complexes with Cu(II) and Zn(II) in different solvents and micellar media aimed at estimating their properties in connection with the living cell. The results indicate that the position of the absorption and emission peaks is mostly influenced by the central metal ion and less by the environmental polarity or the peripheric substituents of the porphyrinic core. The comparison between the overall absorption and emission spectra of the compounds in methanol or cyclohexane vs. direct and reverse Triton X micellar systems, respectively, suggests for all compounds the localization at the interface between the polyethylene oxide chains and the tert-octyl-phenyl etheric residue of the Triton X-100 molecules. These findings could be important when testing the compounds embedded in liposomes or other delivery systems to the targeted cell.

Tetrapyrrole singlet excited state quenching by carotenoids in an artificial photosynthetic antenna.

Two artificial photosynthetic antenna models consisting of a Si phthalocyanine (Pc) bearing two axially attached carotenoid moieties having either 9 or 10 conjugated double bonds are used to illustrate some of the function of carotenoids in photosynthetic membranes. Both models studied in toluene, methyltetrahydrofuran, and benzonitrile exhibited charge separated states of the type C*+-Pc*- confirming that the quenching of the Pc S1 state is due to photoinduced electron transfer. In hexane, the Pc S1 state of the 10 double bond carotenoid-Pc model was slightly quenched but the C*+-Pc*- transient was not spectroscopically detected. A semiclassical analysis of the data in hexane at temperatures ranging from 180 to 320 K was used to demonstrate that photoinduced electron transfer could occur. The model bearing the 10 double bond carotenoids exhibits biexponential fluorescence decay in toluene and in hexane, which is interpreted in terms of an equilibrium mixture of two isomers comprising s-cis and s-trans conformers of the carotenoid. The shorter fluorescence lifetime is associated with an s-cis carotenoid conformer where the close approach between the donor and acceptor moieties provides through-space electronic coupling in addition to the through-bond component.

Ultrastructural and histochemical features of the ground substance in cyclosporin A-induced gingival overgrowth.

The overgrowth-affected gingiva of patients treated with cyclosporin A after kidney transplant was examined with ultrastructural and histochemical methods to evaluate the involvement of connective tissue. Gingival overgrowth has the same clinical signs as local edema. The ultrastructural study showed that the dimensional increase was largely due to increased production of amorphous ground substance by fibroblasts, possibly resulting from an increased release of histamine by mast cells. The histochemical data revealed that the affected tissues contained higher levels of glycosaminoglycans and that cyclosporin A induced comparably high levels of glycosaminoglycans in in vitro cultures of fibroblasts obtained from normal gingiva. The combination of ultrastructural and histochemical data, therefore, strongly suggests that the response of the connective tissue in gingival overgrowth cannot be ignored and may be the main cause of the observed pathological condition.

An improved technique for the histological evaluation of the mucus-secreting status in rat cecum.

Mucin secreted into the alimentary tract often forms a mucus layer on the mucosa and is believed to protect the underlying epithelium against various factors in the lumen. We developed an improved histological technique for the evaluation of the mucus layer in the rat cecum. We used this technique to compare the effect of three nonstarch poly- and oligosaccharides on the status of mucus layer. Rats were divided into four groups (fiber-free [FF], cellulose [CEL], fructooligosaccharide [FOS], or guar gum [GG]). The frozen cecum with its contents was cut into cross-sections (5 mm thick) and fixed overnight in half-strength Bouin's solution. The sections were then transferred to 80% ethanol for 24 h. After being stained with alcian green, the mucus layers were clearly visualized in thin sections of the rat cecum, except for those that received FOS where the mucus layer had disappeared; the strong signal of mucus was seen in the cecal digesta of FOS-fed rats. Our histological method successfully provided information about the status of mucus layer that is important for an assessment of the epithelial state in the intestine.

Synthesis and anion binding studies of o-phenylenevinylene-bridged tetrapyrrolic macrocycle as an expanded analogue of calix[4]pyrrole.

An o-phenylenevinylene-bridged tetrapyrrolic macrocycle (2) was synthesized by means of a Horner-Wadsworth-Emmons reaction between benzylbisphosphonate and SEM-protected diformylpyrrole, followed by deprotection of the SEM groups. This conformationally flexible tetrapyrrole can be considered as an expanded calix[4]pyrrole analogue, which acts as a receptor for the chloride and bromide anions in THF-d8, but undergoes deprotonation upon exposure to the fluoride anion.

Photodynamic inactivation of biofilm: taking a lightly colored approach to stubborn infection.

Microbial biofilms are responsible for a variety of microbial infections in different parts of the body, such as urinary tract infections, catheter infections, middle-ear infections, gingivitis, caries, periodontitis, orthopedic implants, and so on. The microbial biofilm cells have properties and gene expression patterns distinct from planktonic cells, including phenotypic variations in enzymic activity, cell wall composition and surface structure, which increase the resistance to antibiotics and other antimicrobial treatments. There is consequently an urgent need for new approaches to attack biofilm-associated microorganisms, and antimicrobial photodynamic therapy (aPDT) may be a promising candidate. aPDT involves the combination of a nontoxic dye and low-intensity visible light which, in the presence of oxygen, produces cytotoxic reactive oxygen species. It has been demonstrated that many biofilms are susceptible to aPDT, particularly in dental disease. This review will focus on aspects of aPDT that are designed to increase efficiency against biofilms modalities to enhance penetration of photosensitizer into biofilm, and a combination of aPDT with biofilm-disrupting agents.

A green light-absorbing phycoerythrin is present in the high-light-adapted marine cyanobacterium Prochlorococcus sp. MED4.

In the high-light-adapted unicellular marine cyanobacterium Prochlorococcus sp. MED4 the cpeB gene is the only gene coding for a structural phycobiliprotein. The absence of any other phycoerythrin gene in the fully sequenced genome of this organism, the previous inability to detect a gene product, and the mutation of two out of four cysteine residues, normally involved in binding chromophores, suggested that MED4-cpeB might not code for a functional protein. Here, transcription of MED4-cpeB at a low level was detected and the transcriptional start site was mapped. Enrichment of the protein identified phycoerythrobilin as its sole chromophore in vivo, which was confirmed by chromophorylation assays in vitro using the recombinant protein. Phycourobilin is the major chromophore in low-light-adapted Prochlorococcus ecotypes such as strain SS120. Therefore, spectrally tuned phycoerythrins are a characteristic feature of distinct Prochlorococcus ecotypes. Further in vitro mutagenesis experiments replacing one or both cysteines C61R/C82S by arginine or serine, respectively, revealed that only Cys82 is required for chromophore binding. Thus, an unusual green light-absorbing phycoerythrin evolved in the high-light-adapted ecotypes of Prochlorococcus, which potentially serves as a photoreceptor.