Effects of currently used marine antifouling paint biocides on green fluorescent proteins in Anemonia viridis.

Some of the antifouling booster biocides affects the marine ecosystem negatively. The booster biocides that are resistant to degradation are accumulated in the sediment of the oceans. One of the sedentary organisms in the Mediterranean Sea is Anemonia viridis. This study aims at showing the toxicities of common biocides such as irgarol, seanine-211, zinc omadine, and acticide on the fluorescence by GFPs of A. viridis. The decreases in the fluorescence intensities of the GFP were measured within different booster biocide concentrations. The results show that fluorescent intensities of GFP proteins decrease more than 50% when they are exposed to different concentrations of irgarol, zinc omadine, acticide. In conclusion, ecosystem health should be prioritized when new antifouling paint compositions are proposed. From the results, it seems that A. viridis can be considered as a vulnerable organism and it is sensitive to booster biocides within self-polishing antifouling paint formulations.

Surfactant and metal ion effects on the mechanical properties of alginate hydrogels.

This paper addresses the controlled variation of the mechanical properties of alginate gel beads by changing the alginate concentration or by adding different surfactants or cross-linking cations. Alginate beads containing nonionic Brij 35 or anionic sodium dodecyl sulfate (SDS) surfactants were prepared with two different types of cations (Ca2+, Ba2+) as crosslinkers. Compression measurements were performed to investigate the effect of the surfactant and cation types and their concentrations on the Young's modulus of alginate beads. The Young's modulus was determined by using Hertz theory. For all types of alginate gel beads the Young's modulus showed an increasing value for increasing alginate contents. Addition of the anionic surfactant SDS increases the Young's modulus of the alginate beads while the addition of non-ionic surfactant Brij 35 leads to a decrease in Young's modulus. This opposite behavior is related to the contrary effect of both surfactants on the charge of the alginate beads. When Ba2+ ions were used as crosslinker cation, the Young's modulus of the beads with the surfactant SDS was found to be approximately two times higher than the modulus of beads with the surfactant Brij 35. An ion specific effect was found for the crosslinking ability of divalent cations.

Kinetic models for the dynamical behavior of polyacrylamide (PAAm)-κ-carrageenan (κC) composite gels.

A fluorescence method was employed for studying the drying and swelling of PAAm-κC composite gels, which were formed from acrylamide (AAm) and N, N'- methylenebisacrylamide (BIS) with various κ-carrageenan (κC) contents by free radical crosslinking copolymerization in water. Composite gels were prepared at 80 °C with pyranine (Py) as a fluorescence probe. Scattered light, I sc, and fluorescence emission intensities, I em, were monitored during drying and swelling of these gels. The fluorescence intensity of pyranine increased and decreased as drying and swelling time are increased, respectively, for all gel samples. The Stern-Volmer equation combined with moving boundary and Li-Tanaka models were used to explain the behavior of I em during drying and swelling processes respectively. It is found that the desorption coefficient D d decreased as κC contents were increased for a given temperature during drying. However, the cooperative diffusion coefficient, D s presented exactly the opposite case. Conventional gravimetrical and volumetric experiments were also carried out during drying and swelling of PAAm-κC composite gels. It was observed that D d and D s values measured with the fluorescence method were found to be much larger than they were measured with the conventional methods.

The role of pyranine in characterization of PAAm-κC composites by using fluorescence technique.

Polyacrylamide (PAAm) doped by κ-carrageenan (κC) gels were prepared with various amounts of κC varying in the range between 0 wt.% and 3 wt.%. Steady-state fluorescence (SSF) technique was employed for studying sol-gel transition and swelling of PAAm-κC composite gels which were prepared by free-radical crosslinking copolymerization. Pyranine was introduced as a fluorescence probe. Pyranine molecules start to bind to acrylamide polymer chains upon the initiation of the polymerization, thus the spectra of the bonded pyranines shift to the shorter wavelengths. Fluorescence spectra from the bonded pyranines allow one to monitor the sol-gel transition and to test the universality of the sol-gel transition as a function of some kinetic parameters like polymer concentration. Observations around the gel point, t ( c ) for PAAm-κC composite gels showed that the gel fraction exponent ß obeyed the percolation result for low κC (<2.0 wt. %) however classical results were produced at higher κC (>2.0 wt.%). On the other hand, fluorescence intensity of pyranine was measured during in situ swelling process at various amounts of κC and it was observed that fluorescence intensity values decreased as swelling is proceeded. Li-Tanaka equation was used to determine the swelling time constants, τ and cooperative diffusion coefficients, D.

Monitoring small molecule diffusion into hydrogels at various temperatures by fluorescence technique.

Steady state fluorescence technique was used to study small molecule diffusion into polyacrylamide (PAAm) gels at various temperatures. Pyranine (P(y)), dissolved in water was introduced as a probe and fluorescence emission (I(p)) from P(y) was monitored during diffusion. Scattered light intensities, I(sc) from PAAm gel was also monitored to observe structural variations during diffusion process. Increase in I(p) intensity was attributed to P(y) diffusion into PAAm gel. On the other hand decrease in I(sc) intensity was interpreted as the variation of the spatial heterogeneities in the system. Li-Tanaka and Fickian models were used to quantify the swelling and diffusion experiments and diffusion coefficients were produced in both cases. Related activation energies were also calculated from the corresponding physical processes.

Universal behaviour of gel formation from acrylamide-carrageenan mixture around the gel point: a fluorescence study.

The steady state fluorescence (SSF) technique was used to study the sol-gel transition, for the solution free radical crosslinking copolymerization of acrylamide (AAm) with various carrageenan content. N, N'- methylenebis (acrylamide) (BIS) and ammonium persulfate (APS) are used as crosslinker and an initiator, respectively. Pyranine (8-hydroxypyrene-1, 3,6-trisulfonic acid, trisodium salt, HPTS) was added as a floroprobe for monitoring the polymerization. Pyranine molecules start to bind to acrylamide polymer chains upon the initiation of the polymerization; thus, the spectra of the bonded pyranines shift to the shorter wavelengths. Fluorescence spectra from the bonded pyranines allows one to monitor the sol-gel transition, without disturbing the system mechanically, and to test the universality of the sol-gel transition as a function of some kinetic parameters like polymer concentration. Observations around the critical point show that the gel fraction exponent beta obeyed the percolation result for low carrageenan concentrations (< 2.0%) however classical results were produced at higher carrageenan concentration (> 2.0%).