In this work, we demonstrated the ability of the cyanobacterium Pseudanabaena/Limnothrix sp. to produce ultra-small silver nanoparticlesin the forms of metallic silver (Ag⁰) and silver oxides (Ag_xO_y) via a facile green synthetic process. The biological compounds in the cyanobacterial cellular extract acted both as reducing agents for silver ions and functional stabilizing agents for the silver nanoparticles. Furthermore, the antibacterical activity of the as-synthesized nanoparticles against Gram-negative Escherichia coli and Gram-positive Corynebacterium glutamicum bacterial cells was evaluated. The experimental results revealed a remarkable bactericidal activity of the nanoparticles that was both time-dependent and dose-dependent. In addition to their excellent bactericidal properties, the developed nanoparticles can be used as nanosupports in various environmental, biological, and medical applications.

Graphene exhibits exceptional properties, including high tensile strength, mechanical stiffness, and electron mobility. Chemical functionalization of graphene with boron and nitrogen is a powerful strategy for tuning these properties for specific applications. Molecular self-assembly provides an efficient pathway for the tailored synthesis of doped graphene, depending on the molecular precursor used. This study presents a scalable approach to synthesizing large-area boron- and nitrogen-doped graphene using two borazine precursors bearing thiol functionalities. After self-assembly on electropolished polycrystalline copper foil, the precursors undergo photopolymerization under UV irradiation, and subsequent annealing in vacuum transforms the cross-linked BN-doped layer into a graphenoid structure. X-ray photoelectron spectroscopy confirms the integration of the borazine rings into the BNC architecture, while Raman spectroscopy reveals a red shift in the characteristic G bands along with intense and broad D bands, highlighting boron-nitrogen contributions. Transmission electron microscopy provides insight into the morphology and structural quality of the BNC films. The BNC films were successfully integrated as counter electrodes in dye-sensitized solar cells, achieving a power conversion efficiency of up to 6% under 1 sun illumination and 11.8% under low-intensity indoor ambient light. Hence, this work not only establishes a straightforward, controllable route for heteroatom doping but also introduces a novel concept of Pt-free counter electrodes for efficient indoor energy harvesting applications.

Carbon nanotubes (CNTs) possess excellent physicochemical and structural properties alongside their nano dimensions, constituting a medical platform for the delivery of different therapeutic molecules and drug systems. Hydroxytyrosol (HT) is a molecule with potent antioxidant properties that, however, is rapidly metabolized in the organism. HT immobilized on functionalized CNTs could improve its oral absorption and protect it against rapid degradation and elimination. This study investigated the effects of cellular oxidized multiwall carbon nanotubes (oxMWCNTs) as biocompatible carriers of HT. The oxidation of MWCNTs via H₂SO₄ and HNO₃ has a double effect since it leads to increased hydrophilicity, while the introduced oxygen functionalities can contribute to the delivery of the drug. The in vitro effects of HT, oxMWCNTS, and oxMWCNTS functionalized with HT (oxMWCNTS_HT) were studied against two different cell lines (NIH/3T3 and Tg/Tg). We evaluated the toxicity (MTT and clonogenic assay), cell cycle arrest, and reactive oxygen species (ROS) formation. Both cell lines coped with oxMWCNTs even at high doses. oxMWCNTS_HT acted as pro-oxidants in Tg/Tg cells and as antioxidants in NIH/3T3 cells. These findings suggest that oxMWCNTs could evolve into a promising nanocarrier suitable for targeted drug delivery in the future.

Non-toxic carbon-based hybrid nanomaterials based on carbon nanodisks were synthesized and assessed as novel antibacterial agents. Specifically, acid-treated carbon nanodisks (oxCNDs), as a safe alternative material to graphene oxide, interacted through covalent and non-covalent bonding with guanidinylated hyperbranched polyethyleneimine derivatives (GPEI5K and GPEI25K), affording the oxCNDs@GPEI5K and oxCNDs@GPEI25K hybrids. Their physico-chemical characterization confirmed the successful and homogenous attachment of GPEIs on the surface of oxCNDs, which, due to the presence of guanidinium groups, offered them improved aqueous stability. Moreover, the antibacterial activity of oxCNDs@GPEIs was evaluated against Gram-negative E. coli and Gram-positive S. aureus bacteria. It was found that both hybrids exhibited enhanced antibacterial activity, with oxCNDs@GPEI5K being more active than oxCNDs@GPEI25K. Their MIC and MBC values were found to be much lower than those of oxCNDs, revealing that the GPEI attachment endowed the hybrids with enhanced antibacterial properties. These improved properties were attributed to the polycationic character of the oxCNDs@GPEIs, which enables effective interaction with the bacterial cytoplasmic membrane and cell walls, leading to cell envelope damage, and eventually cell lysis. Finally, oxCNDs@GPEIs showed minimal cytotoxicity on mammalian cells, indicating that these hybrid nanomaterials have great potential to be used as safe and efficient antibacterial agents.

Graphene-based nanomaterials have transformed biomedical applications due to their exceptional physicochemical properties, and nitrogen (N)-doping further enhances the electrocatalytic activity of graphene. Driven by the demand for safer and more sustainable nanomaterials, in this work, we compared eco-friendly produced N- doped graphene (bD) with conventionally synthesized N- doped graphene (cD) in three different cell lines. Across all cell types and assays, cD was more toxic than bD. In NIH/3T3 fibroblast cells, cD activated the Nrf2 signaling pathway, whereas in HaCaT keratinocytes, it triggered oxidative stress responses and increased the apoptotic population. High doses of cD also affected THP-1-derived macrophages by inducing apoptosis and arresting the cell cycle in the G0/G1 phase. Although high doses of bD were also cytotoxic, overall, its effects were milder than cD. Our results confirm that green exfoliation of N- doped graphene retains its desirable biomedical properties while enhancing its biocompatibility, making bD a safer choice for future biomedical applications.