The ability to culture cells in three-dimensions has many applications, from drug discovery to wound healing. 3D cell culture methods often require appropriate scaffolds that mimic the cellular environments of different tissue types. The choice of material from which these scaffolds are made is of paramount importance, as its properties will define the manner in which cells interact with the scaffold. Caf1 is a protein polymer that is secreted from its host organism, Yersinia pestis, to enable escape from phagocytosis. In vitro, cells adhere poorly to the protein unless adhesion motifs are specifically introduced. Caf1 is a good candidate biomaterial due to its definable bioactivity, economical production and its ability to form hydrogels, through the use of cross-linkers. In this study, the thermostability of Caf1 was tested over a range of chemical conditions, and an initial characterisation of its rheological properties conducted in order to assess the suitability of Caf1 as a biomedical material. The results show that Caf1 retains its high thermostability even in harsh conditions such as extremes of pH, high salt concentrations and the presence of detergents. In solution, the concentrated polymer behaves as a complex viscous liquid. Due to these properties, Caf1 polymers are compatible with 3D bioprinting technologies and could be made to form a stimuli-responsive biomaterial that can alter its macrorheological properties in response to external factors. Caf1 biomaterials could therefore prove useful as 3D cell scaffolds for use in cell culture and wound repair.
Green fluorescent protein (GFP) molecules are attached to titanium dioxide and cadmium oxide nanoparticles via sol-gel method and fluorescence dynamics of such a protein-metal oxide assembly is investigated with a conventional time correlated single photon counting technique. As compared to free fluorescent protein molecules, time-resolved experiments show that the fluorescence lifetime of GFP molecules bound to these metal oxide nanoparticles gets shortened dramatically. Such a decrease in the lifetime is measured to be 22 and 43 percent for cadmium oxide and titanium dioxide respectively, which is due to photoinduced electron transfer mechanism caused by the interaction of GFP molecules (donor) and metal oxide nanoparticles (acceptor). Our results yield electron transferrates of 3.139 x 108 sand 1.182 x 108 s_ 1 from the GFP molecules to titanium dioxide and cadmium oxide nanoparticles, respectively. The electron transfer rates show a marked decrease with increasing driving force energy. This effect represents a clear example of the Marcus inverted region electron transfer process
Petroselinum hortense L.) plants cultivated under controlled conditions were exposed to different doses of cadmium to investigate the antioxidant capacity and cadmium accumulation in the samples. Two-months-old parsley seedlings were treated with four different concentrations of CdCl 2 (0, 75, 150, and 300 μM) for fifteen days. Cadmium level in leaves increased significantly by increasing the Cd contamination in the soil. Total chlorophyll and carotenoid content declined considerably with Cd concentration. Cd treatment caused a significant increase lipid peroxidation in tissue of leaf. Superoxide dismutase activity (SOD, EC 1.15.1.1) increased partially at 75 and 150 μM CdCl 2 concentrations whereas the activity decreased at 300 μM CdCl 2. Catalase (CAT, EC 1.11.1.6) and ascorbate peroxidase (APX, EC 1.11.1.11) activities were reduced by Cd application. Total phenolic compound amount increased significantly with increasing Cd concentration, as ferric reduction power, superoxide anion radical, and DPPH˙ free radical scavenging activities elevated slightly by the concentration. These results suggest that antioxidant enzymes activities were repressed depending on accumulation of cadmium in leaves of parsley while the non-enzymatic antioxidant activities slightly increased.
The fast charge recombination kinetics and poor sensitizing ability in dye-sensitized solar cells (DSSCs) result in a significant electron loss and performance degradation. However, the retarding of electron recombination and/or increasing light-harvesting efficiency (LHE) via employing an appropriate interface modifier in DSSCs has rarely been investigated. Here, we firstly report a molecularly engineered Caf1 protein (both in monomeric and polymeric forms) to modify the surface states by effectively shielding the unfavorable reactions and improve the light absorption properties by introducing alternative anchoring facilities. Using this novel Caf1bio-polymer with high thermal stability (even at 90 o C), we achieved an unprecedented efficiency of 8.31% under standard illumination test conditions and maintain the output performance even under prolonged irradiation. Time-resolved fluorescence spectroscopy measurement reveals an improved electron transfer rate (k ET = 0.26 to 0.98×10 8 s -1 ), whereas V oc decay rate is lower (70% decay in 90 s) for Caf1-P@TiO 2 based cell than that of bare one (~85% decay in <10 s). We attributed this trend to the presence of chains in bio-polymer structure and the enhanced population of binding facilities with sensitizer molecules, promoting rapid charge transfer into TiO 2 and enhanced dye-loading capability. Our results shed light on the interface engineering and this novel Caf1bio-polymer offers a meaningful transfer of energy to develop efficient electrochemical cells with attractive properties for scale up and practical applications.
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