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    Cellular interactions and design principles of glyco-gold nanoparticles for drug delivery applications
    (Elsevier, 2023) Akturk, Omer; Yilmaz, Bengi
    An escalating tendency prevails to manipulate gold-based nanoparticles decorated on their surfaces with different types of carbohydrates or glycopolymers for the development of versatile nanoplatforms—the so-called glyco-gold nanoparticles (GAuNPs) here—for drug delivery applications. Due to the ease of their surface modification, inherent inertness, and biocompatible nature, gold nanoparticles (AuNPs) are one of those first preferred candidates in this field. Coating of AuNPs with saccharide moieties also makes them gain unique properties such as multivalent binding abilities, active targeting, receptor-mediated internalization of drugs, enhanced biocompatibility, colloidal stability, stealth ability, and so on. This chapter deals with the synthesis methods and design parameters of GAuNPs followed by very detailed drug delivery applications, mainly focusing on the cellular interactions and design parameters in state-of-the-art research. The chapter ends with a concluding remark emphasizing the hurdles encountered in synthesis methodologies and the translation of the bench-top characterization results to different biomedical applications. © 2024 Elsevier Inc. All rights reserved.
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    Colloidal stability and biological activity evaluation of microbial exopolysaccharide levan-capped gold nanoparticles
    (ELSEVIER, 2020) Akturk, Omer
    The main objectives of this study were to explore the suitability of the exopolysaccharide levan, biosynthesized by Bacillus subtilis, to aid in the formation of gold nanoparticles (AuNPs) and to investigate the colloidal stability and in vitro biological activity of this biopolymer-AuNPs complex. AuNPs (mainly spherical, 8-10 nm-sized, and monodispersed) were successfully synthesized in levan concentrations up to 0.5% w/v (L-AuNP0.5) while exposed to ultraviolet C (UVC) irradiation. The increase of levan quantity decreased the size of AuNPs according to Transmission Electron Microscopy (TEM) images and enhanced the colloidal stability significantly. The presence of L-AuNP0.5 at the highest treatment dose (1000 mu g/mL) exhibited substantial cytotoxicity towards L-929 mouse fibroblasts for all incubation periods. Dose-dependent toxicity was observed for the first day while, after this threshold value, medium (100 mu g/mL) and the lowest (10 mu g/mL) treatment doses were non-cytotoxic during 7 days of incubation, implying dose and time-independent cell viabilities ( > 95%) compared to the negative control (complete cell culture medium). There occurred a special surface interaction with cells and LAuNP0.5, especially when the cells were subjected to deliberate starvation periods to increase L-AuNP0.5 internalization via passive and active endocytosis. Scanning Electron Microscopy (SEM) images showed high accumulation of L-AuNP0.5 around or inside the cell membrane after 7 days. Overall, this attribute (high uptake of L-AuNP0.5) could make them promising candidates for prospective cancer therapeutics or drug delivery systems by enabling the cell internalization of anticancer drugs.
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    One-pot facile synthesis of silk sericin-capped gold nanoparticles by UVC radiation: Investigation of stability, biocompatibility, and antibacterial activity
    (Wiley, 2019) Akturk, Omer; Gok, Zehra Gun; Erdemli, Ozge; Yigitoglu, Mustafa
    Herein, an easy one-pot synthesis method for gold nanoparticles (AuNPs), involving only gold salt and sericin extracted from silkworm cocoon in the presence of ultraviolet C (UVC) radiation, was developed. Nanoparticle formation was confirmed by characteristic surface plasmon resonance peaks at 520-540 nm wavelengths, and the influence of silk sericin on enhancing the colloidal stability of AuNPs was confirmed. Transmission electron microscopy examination showed the average size (<10 nm) and size distribution decreased significantly with higher sericin concentration. No antibacterial activity was observed on Gram-positive Bacillus subtilis or Gram-negative Escherichia coli for sole AuNPs (0.065-0.26 mg/ml), but the conjugation of AuNPs with streptomycin antibiotic decreased significantly the required minimum inhibitory concentration doses, as also confirmed with agar plating, Scanning Electron Microscopy and Atomic Force Microscopy analyses. Furthermore, sericin-capped AuNPs showed high cell viabilities (>100%) and no sign of any detectable apoptosis or necrosis in 1-day incubation. Also, high real-time cell proliferation results of AuNPs competitive with positive control groups implied excellent in vitro biocompatibility. These results evidenced that sericin enhanced the colloidal stability of AuNPs and the biological activities of sericin-capped AuNPs reported here could render them suitable nanoscale vehicles for biomedical applications.
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    Wet electrospun silk fibroin/gold nanoparticle 3D matrices for wound healing applications
    (Royal Soc Chemistry, 2016) Akturk, Omer; Kismet, Kemal; Yasti, Ahmet C.; Kuru, Serdar; Duymus, Mehmet E.; Kaya, Feridun; Keskin, Dilek
    This study aimed to fabricate 3D silk fibroin (SF) matrices for skin tissue engineering applications. SF/poly(ethylene oxide) solutions were wet electrospun to obtain a fibrous network (0.7-20 mm diameter), which were then lyophilized to obtain 3D porous nanofibrous matrices (SFM-E: ethanol treated silk fibroin matrices). SF matrices were loaded with citrate-capped gold nanoparticles (AuNPs, 14.27 ppm, D-average = 24 nm) (SFM-AuE: ethanol treated silk fibroin matrices incorporated with AuNPs) and investigated for structural and chemical properties, in vitro biocompatibility and in vivo full-thickness dermal wound healing efficacy in a rat model. AuNP incorporation enhanced the degradation profiles and mechanical properties significantly. SFM-E and SFM-AuE showed similar cell attachment and layer by layer proliferation behaviour, but cells had more spread and flattened morphology on SFM-AuE. Both matrix extracts had high cell viability (>90%), indicating good in vitro biocompatibility. Wound closure was statistically more than the untreated skin control (UTSC) in SFM-E and SFM-AuE applied groups. The recovered tensile strength and elastic modulus of SFM-E and SFM-AuE (40-60%) were not as high as the unwounded skin control (UWSC), but they had elongation at break values similar to UWSC. This was attributed to the still ongoing medium to high inflammation levels leading to a low and immature extent of collagen fibrils on postoperative 14th day. There was only a small amount of epithelialization due to scab formation and medium to high level inflammation for both SFM-E and SFM-AuE, but they were better than UTSC in terms of neovascularization and granulation tissue formation. As a whole, inclusion of AuNPs to SF matrices at 14.27 ppm loading brought some enhancement in the matrix properties and did not cause any toxicity in in vitro and in vivo conditions and even had potency to promote wound healing stages.