The discovery of the interesting intrinsic properties of graphene, a two-dimensional nanomaterial, has boosted further research and development for various types of applications from electronics to biomedicine. During the last decade, graphene and several graphene-derived materials, such as graphene oxide, carbon nanotubes, activated charcoal composite, fluorinated graphenes and three-dimensional graphene foams, have been extensively explored as components of biosensors or theranostics, or to remotely control cell-substrate interfaces, because of their remarkable electro-conductivity. To date, despite the intensive progress in human stem cell research, only a few attempts to use carbon nanotechnology in the stem cell field have been reported. Interestingly, most of the recent in vitro studies indicate that graphene-based nanomaterials (i.e. mainly graphene, graphene oxide and carbon nanotubes) promote stem cell adhesion, growth, expansion and differentiation. Although cell viability in vitro is not affected, their potential nanocytoxicity (i.e. nanocompatibility and consequences of uncontrolled nanobiodegradability) in a clinical setting using humans remains unknown. Therefore, rigorous internationally standardized clinical studies in humans that would aim to assess their nanotoxicology are requested. In this paper we report and discuss the recent and pertinent findings about graphene and derivatives as valuable nanomaterials for stem cell research (i.e. culture, maintenance and differentiation) and tissue engineering, as well as for regenerative, translational and personalized medicine (e.g. bone reconstruction, neural regeneration). Also, from scarce nanotoxicological data, we also highlight the importance of functionalizing graphene-based nanomaterials to minimize the cytotoxic effects, as well as other critical safety parameters that remain important to take into consideration when developing nanobionanomaterials.

Metal nanoparticles (NPs) have received much attention for potential applications in medicine (mainly in oncology, radiology and infectiology), due to their intriguing chemical, electronical, catalytical, and optical properties such as surface plasmon resonance (SPR) effect. They also offer ease in controlled synthesis and surface modification (e.g., tailored properties conferred by capping/protecting agents including N-, P-, COOH-, SH-containing molecules and polymers such as thiol, disulfide, ammonium, amine, and multidentate carboxylate), which allows (i) tuning their size and shape (e.g., star-shaped and/or branched) (ii) improving their stability, monodispersity, chemical miscibility, and activity, (iii) avoiding their aggregation and oxidation over time, (iv) increasing their yield and purity. The bottom-up approach, where the metal ions are reduced in the NPs grown in the presence of capping ligands, has been widely used compared to the top-down approach. Besides the physical and chemical synthesis methods, the biological method is gaining much consideration. Indeed, several drawbacks have been reported for the synthesis of NPs via physical (e.g., irradiation, ultrasonication) and chemical (e.g., electrochemisty, reduction by chemicals such as trisodium citrate or ascorbic acid) methods (e.g., cost, and/ortoxicity due to use of hazardous solvents, low production rate, use of huge amount of energy). However, (organic or inorganic) eco-friendly NPs synthesis exhibits a sustainable, safe, and economical solution. Thereby, a relatively new trend for fast and valuable NPs synthesis from (live or dead) algae (i.e., microalgae, macroalgae and cyanobacteria) has been observed, especially because of its massive presence on the Earth’s crust and their unique properties (e.g., capacity to accumulate and reduce metallic ions, fast propagation). This article discusses the algal-mediated synthesis methods (either intracellularly or extracellularly) of inorganic NPs with special emphasis on the noblest metals, i.e., silver (Ag)- and gold (Au)-derived NPs. The key factors (e.g., pH, temperature, reaction time) that affect their biosynthesis process, stability, size, and shape are highlighted. Eventually, underlying molecular mechanisms, nanotoxicity and examples of major biomedical applications of these algal-derived NPs are presented.

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Organically-modified siloxanes were used as host materials to examine the influence of surface chemistry on protein conformation in a crowded environment. The sol-gel materials were prepared from tetramethoxysilane and a series of monosubstituted alkoxysilanes, RSi(OR′) 3 , featuring alkyl groups of increasing chain length in the R-position. Using circular dichroism spectroscopy in the far-UV region, apomyoglobin was found to transit from an unfolded state to a native-like helical state as the content of the hydrophobic precursor increased from 0-15%. At a fixed molar content of 5% RSi(OR') 3 , the helical structure of apomyoglobin increased with the chain length of the R-group, i.e. methyl < ethyl < n-propyl < n-butyl < n-hexyl. This trend also was observed for the tertiary structure of ribonuclease A, suggesting that protein folding and biological activity are sensitive to the hydrophilic/hydrophobic balance of neighboring surfaces. The observed changes in protein structure did not correlate with total surface area or the average pore size of the modified glasses, but scanning electron microscopy images revealed an interesting relationship between surface morphology and alkyl chain length. The unexpected benefit of incorporating a low content of hydrophobic groups into a hydrophilic surface may lead to materials with improved biocompatibility for use in biosensors and implanted devices.

The developed grape-based cream could be efficiently and safely applied to improve a number of skin conditions (e.g. hyper-pigmentation, premature ageing, acne).

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Hybrid organic−inorganic crystalline materials have been obtained from a simple solvent-free synthesis in highly basic conditions. The formation of an organized hybrid structure has been achieved for the first time via sol−gel without employing bridged organosilica precursors. 3-glycidoxypropyltrimethoxysilane, which is an organically modified alkoxide bearing a terminal epoxy group, has been used for the synthesis. The opening of the epoxy has been observed to produce poly/oligo(ethylene oxide) chains or p-dioxane species. In the second case crystalline hybrids have been formed by self-organization during gelation. Analysis performed by wide-angle X-ray scattering and X-ray diffraction have confirmed the crystalline nature of the aggregates, epoxy ring opening/self-condensation which resulted in a pillared-type organic−inorganic hybrid structure with Si-substituted 2,5-bis(propoxymethyl)-1,4-dioxane organic spacer as pillar.

Marine algae are rich in bioactive nutraceuticals (e.g., carbohydrates, proteins, minerals, fatty acids, antioxidants, and pigments). Biotic (e.g., plants, microorganisms) and abiotic factors (e.g., temperature, pH, salinity, light intensity) contribute to the production of primary and secondary metabolites by algae. Easy, profitable, and sustainable recovery methods include novel solid-liquid and liquid-liquid extraction techniques (e.g., supercritical, high pressure, microwave, ultrasound, enzymatic). The spectacular findings of algal-mediated synthesis of nanotheranostics has attracted further interest because of the availability of microalgae-based natural bioactive therapeutic compounds and the cost-effective commercialization of stable microalgal drugs. Algal extracts can serve as stabilizing/capping and reducing agents for the synthesis of thermodynamically stable nanoparticles (NPs). Different types of nanotherapeutics have been synthesized using physical, chemical, and biological methods. Marine algae are a fascinating source of lead theranostics compounds, and the development of nanotheranostics has been linked to enhanced drug efficacy and safety. Indeed, algae are remarkable nanobiofactories, and their pragmatic properties reside in their (i) ease of handling; (ii) capacity to absorb/accumulate inorganic metallic ions; (iii) cost-effectiveness; and (iv) capacity of eco-friendly, rapid, and healthier synthesis of NPs. Preclinical and clinical trials shall enable to really define effective algal-based nanotherapies. This review aims to provide an overview of the main algal compounds that are nutraceuticals and that can be extracted and purified for nanotheranostic purposes.