Morphological transformations in primitive organisms have long been observed; however, its biomechanical roles are largely unexplored. In this study, we investigate the structural advantages of dimorphism in Arthrospira platensis, a filamentous multicellular cyanobacterium. We report that helical trichomes, the default shape, have a higher persistence length (Lp), indicating a higher resistance to bending or a large value of flexural rigidity (kf), the product of the local cell stiffness (E) and the moment of inertia of the trichomes’ cross-section (I). Through Atomic Force Microscopy (AFM), we determined that the E of straight and helical trichomes were the same. In contrast, our computational model shows that I is greatly dependent on helical radii, implying that trichome morphology is the major contributor to kf variation. According to our estimation, increasing the helical radii alone can increase kf by 2 orders of magnitude. We also observe that straight trichomes have improved gliding ability, due to its structure and lower kf. Our study shows that dimorphism provides mechanical adjustability to the organism and may allow it to thrive in different environmental conditions. The higher kf provides helical trichomes a better nutrient uptake through advection in aquatic environments. On the other hand, the lower kf improves the gliding ability of straight trichomes in aquatic environments, enabling it to chemotactically relocate to more favorable territories when it encounters certain environmental stresses. When more optimal conditions are encountered, straight trichomes can revert to their original helical form. Our study is one of the first to highlight the biomechanical role of an overall-shape transformation in cyanobacteria.

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A simple microwell-based microfluidic chip for microalgal cells trapping was fabricated. An electrostatic cell trapping mechanism, enabled by a positively charged glass surface, was used. The chip was capable of capturing multiple algal cell types. In the case of filamentous Spirulina platensis, we observed single filament occupancy of up to $30% available wells, as high as some previously proposed methods. Captured filaments were not of any preferential size, suggesting well randomized cell trapping. It was found that the electrostatic attraction did not affect the cell growth. Total replacement of liquid inside the wells could be achieved by pumping new solutions via the inlet, making single cell experiments in controlled chemical conditions possible. After the top layer of the chip was removed, cells in the wells could be simply transferred using a micropipette, turning the chip into a platform for strain selection. V C 2014 AIP Publishing LLC. [http://dx

The phycocyanin (PC) in the crude extract is one of the main active compounds that has significant anti-inflammatory properties and the potential to treat gingival inflammation, the common oral disease. This work reports the preparation and characterization of chitosan/pluronic F-127 hydrogels entrapping the crude extracts of PC from Arthrospira platensis (C005H and C005L) as a local drug delivery system aiming to prolong PC release for the treatment of gingivitis. The results showed that the total phenolic content (TPC) values of the crude extracts were in the range of 2 to 5 μg GAE/100g and presented above 85% inhibition in the protein denaturation test and over 65% using a lipoxygenase (LOX) inhibition test. The hydrogels incorporating the crude extracts from C005H and C005L were perfectly prepared via the electrostatic interaction between chitosan and pluronic F-127 with very high encapsulation efficiency. The crude extracts of PC C005H and C005L were released over 70% from the loaded hydrogel within 6 hours under artificial saliva conditions. The anti-inflammatory activity of the released supernatant from the hydrogels after 6 hours was around 32-47% by LOX inhibition. The hydrogel vehicles and loaded-hydrogels did not show any cytotoxic effects against mouse fibroblast cell lines (L929) and human gingival fibroblast cells. Our current work shows that the crude extract PC-loaded chitosan/pluronic F-127 hydrogel is biocompatibility with human cells and shows prolonged crude extract release properties, suggesting it as an alternative treatment approach for gingivitis. Keywords: Phycocyanin, Gingivitis, Hydrogel, Chitosan, Pluronic F-127

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