Induction of antioxidant activities of Arthrospira platensis and Chlorella vulgaris by modified culture conditions.

Microalgae are considered a promising source for obtaining natural compounds with strong antioxidant activity. Despite the great progress made in this field, there is still need for further studies applying simple and cost-effective modifications to reveal their full potential and enhance antioxidant properties. Arthrospira platensis and Chlorella vulgaris are some of the most common cells studied for this purpose. In this study, it was aimed to develop a bioprocess for the enhancement of antioxidant properties of these two microalgae by evaluating the effect of different culture conditions. With this aim, the impacts of light intensity/reactive oxygen species and nitrogen sources/reactive oxygen species were evaluated for the A. platensis and C. vulgaris cells, respectively. Results showed that the antioxidant potential of A. platensis was found to be correlated with the phycocyanin and total phenolic content of cells, and 80 µmol photons m-2 s-1 light intensity induced antioxidant activity in a two-step cultivation mode. For C. vulgaris cells, maximum antioxidant activities of 68.10 ± 1.51% and 75.68 ± 0.66% were obtained in cultures with NH4Cl (0.016% (w/v)) for DPPH and ABTS assays, respectively. The applied oxidative stress factors exhibited different effects on the antioxidant activities of the cells because of their cellular morphologies and changing mechanisms of reactive oxygen species. These outcomes show the potential of applied modifications on cells and suggest a promising route to enhance antioxidant activities of microalgae for further research.

Comparative Evaluation of Chemical Garden Growth Techniques.

Chemical gardens are an exciting area of self-organized precipitation structures that form nano- and micro-sized structures in different shapes. This field has attracted great interest from researchers due to the specific characteristics and potential applications of these structures. Today, research on chemical gardens has provided deeper information regarding the formation mechanisms of these structures, and several techniques have been developed for chemical garden growth. However, they all show different growth patterns and lead to the formation of structures with a variety of morphological, chemical, or physical properties. This study aimed to evaluate the effects of different production techniques on chemical garden growth, taking into consideration the growth patterns, morphology, microstructure, and chemical composition. The chemical garden structures obtained in seed and injection experiments, two common methods, showed highly similar surface structures, void formation, and chemical composition. The membrane growth method has a small number of applications; thus, it was comprehensively evaluated to add new insights to the existing limited data. It produced the most stable and standard structures in a flat sheet-like shape and showed different morphologies than those observed in other two methods. Overall, this study presented significant results about the effect of growth techniques on chemical garden structures and similar systems.

Applications and sensory utilizations of magnetic levitation in 3D cell culture for tissue Engineering.

3D cell culture approaches are cell culture methods that provide good visualization of interactions between cells while preserving the natural growth pattern. In recent years, several studies have managed to implement magnetic levitation technology on 3D cell culture applications by either combining cells with magnetic nanoparticles (positive magnetophoresis) or applying a magnetic field directly to the cells in a high-intensity medium (negative magnetophoresis). The positive magnetophoresis technique consists of integrating magnetic nanoparticles into the cells, while the negative magnetophoresis technique consists of levitating the cells without labelling them with magnetic nanoparticles. Magnetic levitation methods can be used to manipulate 3D culture, provide more complex habitats and custom control, or display density data as a sensor.The present review aims to show the advantages, limitations, and promises of magnetic 3D cell culture, along with its application methods, tools, and capabilities as a density sensor. In this context, the promising magnetic levitation technique on 3D cell cultures could be fully utilized in further studies with precise control.

Aligned with sustainable development goals: microwave extraction of astaxanthin from wet algae and selective cytotoxic effect of the extract on lung cancer cells.

Astaxanthin is one of the most attractive carotenoid in the cosmetic, food, pharmaceutical, and aquaculture industries due to its strong bioactive properties. Among the various sources, several algae species are considered as rich sources of astaxanthin. Downstream processing of algae involves the majority of the total processing costs. Thus, elimination of high energy involved steps is imperative to achieve cost-effective scale in industry. This study aimed to determine operation conditions for astaxanthin extraction from wet Haematococcus pluvialis using microwave-assisted extraction. The isolated astaxanthin extract was evaluated for cytotoxicity on human lung cancer cells. The microwave-assisted extraction process at 75 °C under the power of 700 Watt for 7 min gave the highest astaxanthin yield (12.24 ± 0.54 mg astaxanthin/g wet cell weight). Based on MTT cell viability and Hoechst 33342 nuclear staining assays on A549 lung cancer cells, astaxanthin inhibited cell growth in dose- and time-dependent manners, where IC50 value was determined as 111.8 ± 14.8 µg/mL and apoptotic bodies were observed along with positive control group at 72 hr. These results showed that the treatment with astaxanthin extracted from wet H. pluvialis by microwave-assisted extraction exhibited anti-cancer activity on lung cancer cells indicating a newly potential to be utilized in industry.

Design of chemobrionic and biochemobrionic scaffolds for bone tissue engineering.

Chemobrionic systems have attracted great attention in material science for development of novel biomimetic materials. This study aims to design a new bioactive material by integrating biosilica into chemobrionic structure, which will be called biochemobrionic, and to comparatively investigate the use of both chemobrionic and biochemobrionic materials as bone scaffolds. Biosilica, isolated from Amphora sp. diatom, was integrated into chemobrionic structure, and a comprehensive set of analysis was conducted to evaluate their morphological, chemical, mechanical, thermal, and biodegradation properties. Then, the effects of both scaffolds on cell biocompatibility and osteogenic differentiation capacity were assessed. Cells attached to the scaffolds, spread out, and covered the entire surface, indicating the absence of cytotoxicity. Biochemobrionic scaffold exhibited a higher level of mineralization and bone formation than the chemobrionic structure due to the osteogenic activity of biosilica. These results present a comprehensive and pioneering understanding of the potential of (bio)chemobrionics for bone regeneration.

Development of a Controlled Injection Method Using Support Templates for the Production of Chemobrionic Materials.

Chemobrionics is a research field about the well-known self-organized inorganic structures. Numerous research works have focused on controlling their growth pattern and characteristic features. In the present study, a controlled injection method is proposed to produce more regular self-assembled chemobrionics compared to the standard direct injection technique. This method involves the injection of a metal salt solution into an agarose support template filled with an anionic solution. The obtained structures were studied by scanning electron microscopy, X-ray microtomography, X-ray photoelectron spectroscopy, Raman spectroscopy, Fourier-transform IR spectroscopy, and thermogravimetric analysis. Despite the complex mechanism and chemistry underlying the self-organization phenomena, the controlled injection method enabled the generation of regular standard chemobrionic structures with high experimental reproducibility. It provided the extraction of tubular structures from the reaction vessel without breakage, thus allowing comprehensive characterization. Furthermore, the morphological, chemical, and thermal features of these structures were highly correlated with the standard chemobrionics obtained in the direct injection method. The proposed controlled injection method holds great promise for understanding and controlling the properties of chemobrionics and related structures.

Computational fluid dynamics simulation in scaling-up of airlift photobioreactor for astaxanthin production.

The unicellular green microalga Haematococcus pluvialis accumulates large amounts of the red ketocarotenoid astaxanthin. Aiming to cultivate these microalgae with high astaxanthin efficiency, cultivations were scaled-up from 1000 mL bottle to 2 L and 8 L airlift photobioreactor using volumetric power consumption rate (W/m3) as scale up strategy. After cultivations, computational fluid dynamics (CFD) simulation was used to investigate the flow patterns, mixing efficiency and gas holdup profile within the 2 L photobioreactor. At the end, astaxanthin content was enhanced with increasing the cultivation volume and highest astaxanthin amount of 49.39 ± 1.64 mg/g cell was obtained in 8 L photobioreactor. Hydrodynamic characteristics of photobioreactor was simulated and gas holdup showed difference between the riser and the downcomer regions. Velocity profiles of air and medium had higher values inside the draft tube than obtained in downcomer region. However liquid circulation was achieved from draft tube to the downcomer, mixing was not provided effectively considering the turbulence kinetic energy. For the further research, some developments about column configuration, sparger diameter may be necessary to enhance the mixing characteristics.