Secreted carbohydrates by Chlorella vulgaris cells were used for reducing and capping Silver nanoparticles (AgNPs). Oxygen-bearing functional groups on the carbohydrates found to be the main biochemical groups responsible for anchoring the metal nanoparticles. Transmission electron microscopy (TEM) micrographs showed that isotropic small particles with mean particles size of 7 nm were synthesized. Comparing the TEM results with DLS analysis revealed that the thickness of carbohydrate capping was about 2 nm. A zeta potential of +26 mV made the particles colloidally stable and desirable for anticancer and antimicrobial applications. The MIC against gram positive (Staphylococcus aureus) and gram negative bacteria (Escherichia coli) were determined to be 37.5 μg ml−1 and 9.4 μg ml−1, respectively. Treatment of Hep-G2 cells with 4.7 μg ml−1 AgNPs for 24 h reduced the cell viability to 61%. This concentration was also reduced the cell viability to 37% after 48 h of exposure.

Zinc oxide (ZnO) nanoparticles have gained widespread interest due to their unique properties, making them suitable for a range of applications. Several methods for their production are available, and of these, controlled synthesis techniques are particularly favourable. Large-scale culturing of Chlorella vulgaris produces secretory carbohydrates as a waste product, which have been shown to play an important role in directing the particle size and morphology of nanoparticles. In this investigation, ZnO nanorods were produced through a controlled synthesis approach using secretory carbohydrates from C. vulgaris, which presents a cost-effective and sustainable alternative to the existing techniques. Fourier transform infrared (FTIR) spectroscopy, X-ray powder diffraction (XRD) analysis, transmission electron microscopy (TEM), and UV-Vis spectroscopy were used to characterise the nanorods. The prepared nanorods exhibited a broad range of UV absorption, which suggests that the particles are a promising broadband sun blocker and are likely to be effective for the fabrication of sunscreens with protection against both UVB (290–320 nm) and UVA (320–400 nm) radiations. The antimicrobial activity of the prepared nanorods against Gram-positive and Gram-negative bacteria was also assessed. The nanostructures had a crystalline structure and rod-like appearance, with an average length and width of 150 nm and 21 nm, respectively. The nanorods also demonstrated notable antibacterial activity, and 250 μg/mL was determined to be the most effective concentration. The antibacterial properties of the ZnO nanorods suggest its suitability for a range of antimicrobial uses, such as in the food industry and for various biomedical applications.

Zinc is one of the essential trace elements, and plays an important role in human health. Severe zinc deficiency can negatively affect organs such as the epidermal, immune, central nervous, gastrointestinal, skeletal, and reproductive systems. In this study, we offered a novel biocompatible xanthan gum capped zinc oxide (ZnO) microstar as a potential dietary zinc supplementation for food fortification. Xanthan gum (XG) is a commercially important extracellular polysaccharide that is widely used in diverse fields such as the food, cosmetic, and pharmaceutical industries, due to its nontoxic and biocompatible properties. In this work, for the first time, we reported a green procedure for the synthesis of ZnO microstars using XG, as the stabilizing agent, without using any synthetic or toxic reagent. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM) were used to study the structure, morphology, and size of the synthesized ZnO structures. The results showed that the synthesized structures were both hexagonal phase and starlike, with an average particle size of 358 nm. The effect of different dosages of XG-capped ZnO nanoparticles (1–9 mM) against Gram-negative (Escherichia coli) and Gram-positive (Bacillus licheniformis, Bacillus subtilis, and Bacillus sphaericus) bacteria were also investigated. Based on the results, the fabricated XG-capped ZnO microstars showed a high level of biocompatibility with no antimicrobial effect against the tested microorganisms. The data suggested the potential of newly produced ZnO microstructures for a range of applications in dietary supplementation and food fortification.

Cell immobilization on the magnetic nanoparticles (MNPs) and magnetic harvesting is a novel approach for microalgal cells separation. To date, the effect of these nanoparticles on microalgal cells was only studied over a short period of time. More studies are hence needed for a better understanding of the magnetic harvesting proposes or environmental concerns relating to long-term exposure to nanoparticles. In this study, the impact of various concentrations of MNPs on the microalgal cells growth and their metabolic status was investigated over 12 days. More than 60% reduction in mitochondrial activity and pigments (chlorophyll a, chlorophyll b, and carotenoids) content occurred during the first 6 days of exposure to ≥50 µg/mL nanoparticles. However, more than 50% growth inhibitory effect was seen at concentrations higher than 400 µg/mL. Exposure to MNPs gradually induced cellular adaptation and after about 6 days of exposure to stress generating concentrations (˂400 µg/mL) of IONs, microalgae could overcome the imposed damages. This work provides a better understanding regarding the environmental impact of MNPs and appropriate concentrations of these particles for future algal cells magnetic immobilization and harvesting.

Various studies were performed to fabricate self-assembling nanoobjects out of noble metals, but a few efforts were made for engineering iron-based nanorods toward sell-assembling blocks. In this regard β-FeOOH nanorods were fabricated in various sizes to achieve iron-based rod nanoblocks with selfassembling potential. Hydrolysis of ferric ions in various concentrations was successfully developed as a novel approach to control the growth of β-FeOOH crystals and tuning the length of rods in the nano range, below 100 nm. It was found that the concentration of ferric ion has no effect on the widths of nanorods, but the length was affected. By increasing the concentration of ferric ions, an increase in the length of nanorods and an increase of aspect ratio occurred. All sizes of the resulting FeOOH nanorods exhibited mesoporous feature, but interestingly the hysteresis loops were different due to different pore patterns. In fact, pores on the larger particles were more uniform in size and shape. Nanorods of small length did not make suitable interactions toward ordered phase formation, but rods with the mean length of about 90 nm or longer, at a certain concentration, were able to form nematic phases. The large (∼+40 mV) zeta-potential of nanorods prevents formation of dense arrays, and just bundle-like structures were observed. These findings highlight the importance of size, surface charge, and concentration of nanoobjects in the formation of 3D structures. The developed technique in the fabrication of β-FeOOH nanorods provides pure structures that are free from any size-controlling agent. These pure structures are suitable for further functionalization or coating. Self-assembling nanoobjects is a developing field in nanotechnology, and therefore studies can help our understanding over the assembling process.