1. Efficient Method for the Concentration Determination of Fmoc Groups Incorporated in the Core-Shell Materials by Fmoc-Glycine
Elżbieta Szczepańska, Beata Grobelna, Jacek Ryl, Amanda Kulpa, Tadeusz Ossowski, Paweł Niedziałkowski Molecules. 2020 Sep 1;25(17):3983. doi: 10.3390/molecules25173983.
In this paper, we described the synthesis procedure of TiO2@SiO2 core-shell modified with 3-(aminopropyl)trimethoxysilane (APTMS). The chemical attachment of Fmoc-glycine (Fmoc-Gly-OH) at the surface of the core-shell structure was performed to determine the amount of active amino groups on the basis of the amount of Fmoc group calculation. We characterized nanostructures using various methods: transmission electron microscope (TEM), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS) to confirm the modification effectiveness. The ultraviolet-visible spectroscopy (UV-vis) measurement was adopted for the quantitative determination of amino groups present on the TiO2@SiO2 core-shell surface by determination of Fmoc substitution. The nanomaterials were functionalized by Fmoc-Gly-OH and then the fluorenylmethyloxycarbonyl (Fmoc) group was cleaved using 20% (v/v) solution of piperidine in DMF. This reaction led to the formation of a dibenzofulvene-piperidine adduct enabling the estimation of free Fmoc groups by measurement the maximum absorption at 289 and 301 nm using UV-vis spectroscopy. The calculations of Fmoc loading on core-shell materials was performed using different molar absorption coefficient: 5800 and 6089 dm3 × mol-1 × cm-1 for λ = 289 nm and both 7800 and 8021 dm3 × mol-1 × cm-1 for λ = 301 nm. The obtained results indicate that amount of Fmoc groups present on TiO2@SiO2-(CH2)3-NH2 was calculated at 6 to 9 µmol/g. Furthermore, all measurements were compared with Fmoc-Gly-OH used as the model sample.
2. Size-Controlled Synthesis of Modifiable Glycine-Terminated Au Nanoclusters as a Platform for Further Functionalization
Maryam Alyari, Robert W J Scott Langmuir. 2021 Nov 16;37(45):13471-13478. doi: 10.1021/acs.langmuir.1c02225. Epub 2021 Nov 5.
An improved and simple synthetic method for producing stable narrow-sized glycine-cystamine (Gly-CSA)-functionalized Au nanoclusters (NCs) from protected Fmoc-glycine-cystamine (Fmoc-Gly-CSA)-functionalized Au NCs is demonstrated in this study. The NC size and size distribution can be controlled directly as a function of reducing agent concentration with the formation of smaller NC core diameters at higher concentrations of NaBH4. Furthermore, when using 0.30 M NaBH4, three UV-vis absorption peaks at 690, 440, and 390 nm were seen, which are consistent with the formation of Fmoc-Gly-CSA-functionalized Au25L18 NCs. After deprotection of the Gly-CSA-functionalized Au NCs, the reactivity of the primary amine groups was investigated. Methyl acrylate-glycine-cystamine (MA-Gly-CSA)-functionalized Au NCs with terminal acetyl groups were formed via the Michael addition reaction of terminal amine groups with methyl acrylate. This reaction resulted in the formation of ester-terminated Au NCs including atom-precise MA-Gly-CSA Au25(SR)18 NCs. The functionalization of the ligand was confirmed by 1H NMR and UV-vis spectra, and TEM images of MA-Gly-CSA- and Gly-CSA-functionalized Au NCs showed that the size of the NCs remained unchanged after the reaction. With controllable NC size and facile functionalization of the Gly-CSA-functionalized Au NCs, these clusters have promising potential as scaffolds for biomedical applications.
3. Fmoc-PEG Coated Single-Wall Carbon Nanotube Carriers by Non-covalent Functionalization: An Experimental and Molecular Dynamics Study
Yesim Yeniyurt, et al. Front Bioeng Biotechnol. 2021 May 14;9:648366. doi: 10.3389/fbioe.2021.648366. eCollection 2021.
Due to their structural characteristics at the nanoscale level, single-walled carbon nanotubes (SWNTs), hold great promise for applications in biomedicine such as drug delivery systems. Herein, a novel single-walled carbon nanotube (SWNT)-based drug delivery system was developed by conjugation of various Fmoc-amino acid bearing polyethylene glycol (PEG) chains (Mw = 2,000, 5,000, and 12,000). In the first step, full-atom molecular dynamics simulations (MD) were performed to identify the most suitable Fmoc-amino acid for an effective surface coating of SWNT. Fmoc-glycine, Fmoc-tryptophan, and Fmoc-cysteine were selected to attach to the PEG polymer. Here, Fmoc-cysteine and -tryptophan had better average interaction energies with SWNT with a high number of aromatic groups, while Fmoc-glycine provided a non-aromatic control. In the experimental studies, non-covalent modification of SWNTs was achieved by Fmoc-amino acid-bearing PEG chains. The remarkably high amount of Fmoc-glycine-PEG, Fmoc-tryptophan-PEG, and Fmoc-cysteine-PEG complexes adsorbed onto the SWNT surface, as was assessed via thermogravimetric and UV-vis spectroscopy analyses. Furthermore, Fmoc-cysteine-PEG5000 and Fmoc-cysteine-PEG12000 complexes displayed longer suspension time in deionized water, up to 1 and 5 week, respectively, underlying the ability of these surfactants to effectively disperse SWNTs in an aqueous environment. In vitro cell viability assays on human dermal fibroblast cells also showed the low cytotoxicity of these two samples, even at high concentrations. In conclusion, synthesized nanocarriers have a great potential for drug delivery systems, with high loading capacity, and excellent complex stability in water critical for biocompatibility.
