Browsing by Author "Toprak M.S."

Now showing 1 - 3 of 3

A versatile strategy to synthesize sugar ligand coated superparamagnetic iron oxide nanoparticles and investigation of their antibacterial activity
(2021-03-20) Saladino G.M.; Hamawandi B.; Demir M.A.; Yazgan I.; Toprak M.S.
For the time being, a great attention has been given to the search of green and reusable materials with antibacterial properties. The present research focused on the design and synthesis of hybrid structures constituting superparamagnetic iron oxide nanoparticles (SPIONs) coated with sugar ligands (SL), synthesized using a green and efficient microwave (MW)-assisted hydrothermal synthesis. The sugar ligands were selectively engineered to obtain antibacterial characteristics towards multi-drug resistant bacterial strains, which are among the most problematic bacterial species in antibiotic development efforts. The superparamagnetic behavior was obtained by synthesizing core iron oxide nanoparticles with a diameter below twenty nm. The MW-assisted hydrothermal method yielded a uniform coating of SPIONs with several sugar ligands, granting strongly negative-charged surfaces, which have eventually contributed to their bactericidal activity. The research work allowed to get insights into the magnetic properties of the sugar ligand coated SPIONs, as well as on morphological and functional characteristics of the hybrid nanoparticles, by employing both spectroscopy and imaging techniques, such as FT-IR, Scanning/Transmission Electron Microscopy (S/TEM). Detailed characterizations of the nanoparticles’ charge, using zeta potential analysis helped to identify the highly charged hybrids for antibacterial applications. Furthermore, studies on the bactericidal properties of selected SL-SPION hybrids highlighted a high selectivity towards both gram-negative and gram-positive bacteria along with improving bactericidal activity of streptomycin/penicillin mixture. Detailed studies done on Pseudomonas aeruginosa revealed that the SPIONs selectively downregulated the virulence factor pyoverdine and altered bacterial morphology depending on the SL chemistry. The synthesized materials with antibacterial activity pave the way for an effective path towards the design and development of nanostructures and coatings against antibiotic-resistant bacterial species.
Carbon quantum dots conjugated rhodium nanoparticles as hybrid multimodal contrast agents
(2021-09-01) Saladino G.M.; Kilic N.I.; Brodin B.; Hamawandi B.; Yazgan I.; Hertz H.M.; Toprak M.S.
Nanoparticle (NP)‐based contrast agents enabling different imaging modalities are sought for non‐invasive bio‐diagnostics. A hybrid material, combining optical and X‐ray fluorescence is presented as a bioimaging contrast agent. Core NPs based on metallic rhodium (Rh) have been demonstrated to be potential X‐ray Fluorescence Computed Tomography (XFCT) contrast agents. Microwave‐assisted hydrothermal method is used for NP synthesis, yielding large‐scale NPs within a significantly short reaction time. Rh NP synthesis is performed by using a custom designed sugar ligand (LODAN), constituting a strong reducing agent in aqueous solution, which yields NPs with primary amines as surface functional groups. The amino groups on Rh NPs are used to directly conjugate excitation‐independent nitrogen‐doped carbon quantum dots (CQDs), which are synthesized through citrate pyrolysis in ammonia solution. CQDs provided the Rh NPs with optical fluorescence properties and improved their biocompatibility, as demonstrated in vitro by Real‐Time Cell Analysis (RTCA) on a macrophage cell line (RAW 264.7). The multimodal characteristics of the hybrid NPs are confirmed with confocal microscopy, and X‐ray Fluorescence (XRF) phantom ex-periments.
On the effect of modified carbohydrates on the size and shape of gold and silver nanostructures
(2020-07-01) Yazgan I.; Gümüş A.; Gökkuş K.; Demir M.A.; Evecen S.; Sönmez H.A.; Miller R.M.; Bakar F.; Oral A.; Popov S.; Toprak M.S.
Gold (Au) and silver (Ag) nanostructures have widespread utilization from biomedicine to materials science. Therefore, their synthesis with control of their morphology and surface chemistry have been among the hot topics over the last decades. Here, we introduce a new approach relying on sugar derivatives that work as reducing, stabilizing, and capping agents in the synthesis of Au and Ag nanostructures. These sugar derivatives are utilized alone and as mixture, resulting in spherical, spheroid, trigonal, polygonic, and star-like morphologies. The synthesis approach was further tested in the presence of acetate and dimethylamine as size-and shape-directing agents. With the use of transmission electron microscopy (TEM), selected area electron diffraction (SAED), x-ray diffraction (XRD), scanning electron microscopy (SEM), and ultraviolet-visible (UV-vis) absorption spectroscopy techniques, the particle size, shape, assembly, aggregation, and film formation characteristics were evaluated. NPs’ attributes were shown to be tunable by manipulating the sugar ligand selection and sugar ligand/metal-ion ratio. For instance, with an imine side group and changing the sugar moiety from cellobiose to lactose, the morphology of the Ag nanoparticles (NPs) transformed from well dispersed cubic to rough and aggregated. The introduction of acetate and dimethylamine further extended the growth pattern and morphological properties of these NPs. As examples, L5 AS, G5AS, and S5AS ligands formed spherical or sheet-like structures when used alone, which upon the use of these additives transformed into larger multicore and rough NPs, revealing their significant effect on the NP morphology. Selected samples were tested for their stability against protein corona formation and ionic strength, where a high chemical stability and resistance to protein coating were observed. The findings show a promising, benign approach for the synthesis of shape-and size-directed Au and Ag nanostructures, along with a selection of the chemistry of carbohydrate-derivatives that can open new windows for their applications.