In recent years, there have been a lot of papers and reports on the DNA-templated silver nanoclusters. These nanoclusters are ultra-bright and stable fluorescent beacons. Application of DNA-templated silver nanoclusters for biomolecules detection and bioimaging seems promising. However, direct conjugation between DNA-templated silver nanoclusters and antibodies is complicated while nanoclusters tend to degrade under conjugation conditions. To overcome this problem, it is possible to create a probe that not only can serve as an fluorescence reporter but also can contain the recognition motif that could selectively bind with target biomolecules. In the present work, we developed DNA-templated silver nanoclusters based on aptamer to lung cancer. Various sequences were added to core aptamer nucleotide sequence to form fluorescent nanoclusters. The synthesis of DNA-templated silver nanoclusters using borohydride reduction was conducted. Nanoclusters with 567 nm excitation and 630 nm emission were produced. The fluorescence quantum yield was 32 %. The storage technique of DNA-templated silver nanoclusters was optimized to ensure their photostability during the storage. Thus, bright and stable fluorescent red-emitting DNA-templated silver nanoclusters based on novel aptamer to lung cancer were developed. However, the potential use of DNA Ag NC for cell staining is complicated by the partial quenching of DNA Ag NC fluorescence in the presence of biomolecules.
The use of Dunaliella salina microalgae as bioreactors allows to produce gold nanoparticles with anticancer activity by means of green chemistry. The method has been reported for the synthesis of gold nanoparticles using extract of D. salina. This green synthesis technique involves using bright sunlight that we consider as poorly controlled condition. The mechanism of nanoparticles toxicity is not yet elucidated. The toxic effect might arise either from toxic intermediates production during bioreduction of gold ions or from physical adsorption of bioactive molecules on nanoparticles surfaces. This research aimed to optimize gold nanoparticles biosynthesis using aqueous extract of D. salina (AED) and to clarify cytotoxic properties of synthesized nanoparticles. The synthesis of nanoparticles involved heating the reaction mixture and was carried out without using sunlight exposure. The fluorometric alamar blue-based toxicity tests with mammalian cell cultures HeLa and Vero were conducted. The following pollutants were tested: biogenic nanoparticles (AED-AuNPs), 15 nm citrate-capped gold nanoparticles stabilized by aqueous extract of D. salina (Cit-AuNPs@AED), 15 nm citrate-capped gold nanoparticles stabilized by polyethylene glycol (Cit-AuNPs@PEG). We have shown that heating the reaction mixture during bioreduction of HAuCl4 by AED led to the formation of gold nanoparticles with average diameter 12.1±4.1 nm. It has been shown that AED-AuNPs exerted a selective cytotoxic effect on the cancer cell line HeLa. Kidney epithelial cell line Vero appeared to be much more resistant to AED-AuNP than HeLa cells over testconcentration range 50-400 mg Au/L. Cit-AuNPs@AED were found to be non toxic. This evidence indicate that the toxicity of biogenic nanoparticles is likely to be associated with biotransformation of D. salina metabolites during the bioreduction of chloroaurate ions.
Gold nanoparticles are intensively studied in biomedicine. Assessment of their biocompatibility is highly important. Currently there is lack of evidence, concerning nanotoxicity of ultrasmall gold nanoparticles < 5 nm. Existing data are rather contradictory. The aim of that study was to evaluate the toxicity of 2 nm colloidal gold, using microalga Dunaliella salina. Cellular barriers of that microalga are very similar to animal cells so it might be considered as a valuable model for nanotoxicity testing. Chlorophyll content as a test–function was used. Spectrophotometric method for chlorophyll determination in vivo in suspensions of D.salina cultures was applied. Calculated EC50 48h value of ionic gold was 25.8 ± 0.3 mg Au/L. EC50 value of phosphine-stabilized gold nanoclusters was 32.2 ±1.1 mg Au/L. It was not possible to calculate EC50 for 15 nm citrate gold nanoparticles, as they were non-toxic at all concentrations tested. These results are confirmed by fluorescent –microscopic monitoring of the same probes. It was shown that 10-fold growth of phosphine-stabilized gold nanoparticles (from 2.3 ± 0.9 nm to 21.1 ± 7.5 nm) led to 7-fold decrease of their toxicity.
It was shown in the experience with 60 white mice that separate and combined effects of stress factors: noctidial lighting (800 lux), sodium nitrite (0.2% solution in water) and p-toluidine (with food) within 107 days causes a change in impedance value of erythrocytes at frequencies 1 Hz – 1MHz. Changes in the activity of intracellular aminotransferases, creatinine and urea were observed, indicating cardiotoxic and hepatotoxic effects.
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