Effects of reaction conditions on light-dependent silver nanoparticle biosynthesis mediated by cell extract of green alga Neochloris oleoabundans.

Silver nanoparticles (AgNPs) were synthesized by incubating the mixture of AgNO3 solution and whole-cell aqueous extracts (WCAEs) of Neochloris oleoabundans under light conditions. By conducting single-factor and multi-factor optimization, the effects of parameters including AgNO3 concentration, pH, and extraction time were quantitatively evaluated. The optimal conditions in terms of AgNP yield were found to be 0.8 mM AgNO3, pH 5, and 9-h extraction. The AgNPs thus synthesized were quasi-spherical with a mean particle diameter of 16.63 nm and exhibited decent uniformity as well as antibacterial activities, which may facilitate AgNP biosynthesis's application in the near future.

Mechanism of light-dependent biosynthesis of silver nanoparticles mediated by cell extract of Neochloris oleoabundans.

This study investigated the role of chlorophyll and light in the biosynthesis of silver nanoparticles (AgNPs) using disrupted cell aqueous extract of Neochloris oleoabundans. It was found that, while increasing sonication time increased the percentage of disrupted cells and efficiency of aqueous cell extraction, over-sonication reduced AgNPs production. AgNPs biosynthesis required illumination of white, blue, or purple light while AgNPs formation was undetectable under dark condition or illumination of orange or red light, indicating only photons of high energy levels among the photosynthetic active radiations are capable of exciting the electrons of chlorophylls to a state that is sufficient for Ag+ reduction. Chlorophylls were demonstrated to be an essential component mediating the reduction of Ag+ and results of mass balance suggest that chlorophylls need to be recycled for the reaction to complete. The ultimate electron donor was hypothesized to be water, which supplemented electrons through water splitting catalyzed by photosynthetic enzyme complexes such as photosystem II. A hypothetical reaction mechanism is proposed for the light-dependent biosynthesis of AgNPs based on systematic experimental results and literature data for the first time.

[Oregano essential oil as an inhibitor of higher fatty acid oxidation].

Inhibition of the oxidation of fatty acids methyl esters by oregano essential oil was studied using capillary gas chromatography. A mixture of fatty acids which contained saturated, mono-, di-, and polyunsaturated acids with 16-24 carbon atoms was extracted from mice brain. Changes in the composition of esters in hexane solutions both in the presence of oregano essential oil and without it were examined during their autooxidation in light for 1 year. It was found that the oxidation rate of unsaturated fatty acids increases with increasing degree of their unsaturation. Oregano essential oil inhibited the oxidation process. Antioxidant activity of the oil increased with increase of its concentration. It was shown that carvacrol and thymol are the main antioxidant components of oregano oil.

Photodynamic therapy-generated tumor cell lysates with CpG-oligodeoxynucleotide enhance immunotherapy efficacy in human papillomavirus 16 (E6/E7) immortalized tumor cells.

Immunotherapy with photodynamic therapy (PDT) offers great promise as a new alternative for cancer treatment; however, its use remains experimental. In this study, we examined the immunotherapeutic significance of human papillomavirus (HPV)-immortalized tumor cell lysates induced by PDT with CpG-oligodeoxynucleotide (ODN). PDT-cell lysates were generated by irradiating Radachlorin (5 microg/mL) preloaded TC-1 cells carrying HPV 16 E7. PDT-cell lysates plus ODN coinjection for protection against E7-expressing tumors as well as specific immune responses were evaluated with the following tests: heat shock protein 70 (HSP70) enzyme-linked immunosorbent assay, in vitro and in vivo tumor growth inhibition, interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha) assay, cytotoxic T-lymphocyte assay, and fluorescence activated cell sorting (FACS) analysis. PDT-cell lysates plus ODN coinjection showed a significant suppression of tumor growth at both prophylactic and therapeutic levels, compared to PDT (or F/T)-cell lysates or ODN alone. In addition, we evaluated the level of the immune response with the coinjection. HSP70, an important regulator of inflammatory and immune response, was observed in abundance in the PDT-cell lysates. IFN-gamma production and cytotoxic T lymphocytes (CTL) responses were induced by PDT-cell lysates plus ODN injection. The coinjection resulted in PDT-cell lysate-specific antibodies (IgG1, IgG2a, IgG2b, and IgG3) and T-helper cell responses significantly higher than PDT-cell lysates alone. Moreover, IFN-gamma production and CTL responses were significantly induced in the PDT-cell lysate plus ODN immunized groups. These enhanced immune responses appeared to be mediated by CD8+ T cells only. These data suggest that PDT-cell lysates plus ODN injection may be an effective approach to induce CTL immune responses as a possible immunotherapeutic strategy for cancer therapy.

Induction of the synthesis of an UV-absorbing substance in the green alga Prasiola stipitata.

The chlorophyte Prasiola stipitata produces a UV-absorbing substance with an absorption maximum at 324 nm. The wavelength-dependent induction of the synthesis of this substance was investigated using simulated solar radiation in combination with 15 cut-off and one broad-band filter. The algae were exposed from three different distances (89, 100 and 119 cm) to the solar simulator producing a maximum of 203.58, 1.24 and 46.86 W/m(2) and a minimum of 107.94, 0.64 and 24.44 W/m(2) irradiances for PAR, UV-B and UV-A, respectively. A polychromatic action spectrum was calculated from the pooled results showing a clear maximum at 300 nm in the long-wavelength UV-B range, but there is still some induction caused by UV-A and PAR. The ratio of the effectiveness from PAR to UV-A to UV-B amounts to 1:2:22.

RNA-dependent DNA binding activity of the Pur factor, potentially involved in DNA replication and gene transcription.

The PUR element is a polypurine polypyrimidine motif that can stimulate transcription, encountered in the 5' regions of various genes and in the vicinity of several DNA replication initiation zones. We demonstrate that the PUR complex formation between the purine-rich strand of PUR and nuclear extracts can be prevented by pretreatment of nuclear extracts with RNA-damaging agents such as UV light or RNase A. A biochemical affinity method reveals that small RNA molecules copurify with the Pur factor. Moreover, the PUR binding activity of RNA-depleted nuclear extracts can be restored by addition of phenol-extracted RNAs. This work adds a new member in the emerging class of ribonucleoprotein particles as regulatory factors of the genetic expression.