Comparing toxicity and bioactivity of gold nanoparticles synthetized using two brown algae Cystoseira sp

• ¹ Centre of Molecular and Environmental Biology, Department of Biology, University of Minho, Portugal
• ² Department of Inorganic Chemistry, University of Vigo, Spain
• ³ Laboratório Ibérico Internacional de Nanotecnologia (INL), Portugal
• ⁴ Institute of Science and Innovation for Bio-Sustainability, University of Minho, Portugal

The marine ecosystem has captured a major attention in recent years since various biologically active compounds have been isolated and screened for pharmacological activity from dissimilar marine provenience. Marine biological resources can be considered an essential for nanotechnology, researchers had been interested to synthesize metallic nanoparticles from marine source because it is thought to be ecofriendly, nontoxic, environmentally acceptable ‘‘green procedures”, reduces the down-streaming process making it very cost effective and the availableness of the source from the diverse marine ecosystem becomes a much easier task. The biosynthesized nanoparticles from marine compound offer stabilized nanoparticles through compounds present in the marine source that make them more efficient for both biomedical and industrial applications[1]. In this regard, we have focus our attention in two algae of Cystoseira. It is a genus of marine brown macroalgae composed of about 40 species. It is widely distributed in the North East Atlantic, the Baltic Sea and the Mediterranean. This genus contains a wide variety of secondary metabolites (e.g. terpenoids, steroids, phlorotannins, phenolic compounds, carbohydrates, triacylglycerols/fatty acids, pigments, vitamins) that are associated with pharmacological properties, such as antioxidant, anti-inflammatory, cytotoxicity, anticancer, cholinesterase inhibition and anti-diabetic activities but also antibacterial, antifungal and anti-parasitic activities [2]. Cystoseira baccata (CB) and Cystoseira tamariscifolia (CT) are two species of this genus that differ in geographic distribution, morphology and possibly content of secondary metabolites. Gold nanoparticles are presently under intensive study since they can be the remarkable scaffold for novel biological and chemical applications owing to their unique electrical, chemical and optical properties. Such as their easy synthesis and good biocompatibility due to the low reactivity of the golden core. Therefore presenting potential applications in the development of new technologies in different fields such as in the food, cosmetic and pharmaceutical industry [3,4]. Previously, González-Ballesteros et al have reported the synthesis of gold nanoparticles with antitumor activity led by the macroalga CB [5]. In the present study, we have compared the ability of C. baccata and C. tamariscifolia (CT) in the synthesis of gold nanoparticles. With this aim, aqueous extracts of the two macroalgae were prepared and their reducing activity, total phenolic content and DPPH scavenging activity were determined before and after the synthesis of nanoparticles. Results showed that CT possess three times more reducing power, almost 4 times more phenolic content and 4 time more DPPH scavenging activity than CB. The nanoparticles obtained were characterized by UV-Vis spectroscopy and Transmission electron microscopy confirming the formation of spherical nanoparticles with a mean diameter of 8.4 ± 2.2 nm in the case of Au@CB and 7.6 ± 2.2 nm for Au@CT. In order to compare the biological potential of both CT and CB extracts and their respective gold nanoparticles (Au@CT and Au@CB), it was investigated whether they affect the viability in mouse (L929 cell line) and human (BJ5-ta cell line) fibroblast cells as in vitro models, by evaluating cellular metabolism by tetrazolium-based colorimetric cellular assay (MTT); cell membrane integrity by lactate dehydrogenase activity (LDH); wound-healing assay to asses effects on cell proliferation and migration capacity. Both algae extracts and derived nanoparticles present a non-cytotoxic profile in lower concentrations, which are efficient in cell regeneration, although with some differences between both species. For a correlation between in vitro and in vivo toxicity, the zebrafish embryo toxicity (ZET) assay, recomended by OECD to evaluate acute and chronic toxicity, was performed. This model organism has a translucent body, allowing real time observation, and allows the evaluation of whole organism responses, from mortality to more specific parameters such as neurotoxicity. The results show that toxicity is evident only at very high concentrations. These promising results thus support that green synthesis in CB and CT extracts of non-toxic, bioactive nanoparticles have an interesting potential for biomedical applications.