Hydrogel-based thermosensor using peptide nucleic acid and PEGylated graphene oxide

Developing a ready-to-use miniaturized thermosensor is a great challenge due to its individual use on a large scale for daily business such as food industry and healthcare. Herein, a polyethylene glycol (PEG)-modified graphene oxide (GO)-based hydrogel thermosensor was established with a fluorescent dye-labeled peptide nucleic acid (F-PNA). The size-tunable hydrogel with high water content and sufficient solidity allowed free movement of the oligonucleotides through the pores and improved usability for handling the sensor. In the PEG-GO hydrogel, the DNA/F-PNA duplex could be denatured by increasing the temperature, followed by selective PNA capture on the PEG-GO. Using this principle, the PEG-GO hydrogel exhibited a change in the fluorescence signal of F-PNA in a temperature-dependent manner, allowing real-time visualization of temperature on a large scale. The temperature detection range of this system can be adjusted by designing the PNA strands based on the melting temperature of the DNAzyme/PNA duplex. Its sensing specificity and detection range could be increased and broadened by observing multi-color detection using PNA probes labeled with different fluorescent dyes of different lengths in a single hydrogel. In addition, the hydrogel platform is easy to store for long time periods via dehydration and can be restored with the addition of water, allowing easy transport, storage, and use of the thermosensor in everyday life.

The Effect of PEGylated Graphene Oxide Nanoparticles on the Th17-Polarization of Activated T Helpers

We investigated the direct effect of PEGylated graphene oxide (P-GO) nanoparticles on the differentiation, viability, and cytokine profile of activated T helper type 17 (Th17) in vitro. The subject of the study were cultures of "naive" T-helpers (CD4+) isolated by immunomagnetic separation and polarized into the Th17 phenotype with a TCR activator and cytokines. It was found that P-GO at low concentrations (5 µg/mL) had no effect on the parameters studied. The presence of high concentrations of P-GO in T-helper cultures (25 μg/mL) did not affect the number and viability of these cells. However, the percentage of proliferating T-helpers in these cultures was reduced. GO nanoparticles modified with linear polyethylene glycol (PEG) significantly increased the percentage of Th17/22 cells in cultures of Th17-polarized T helpers and the production of IFN-γ, whereas those modified with branched PEG suppressed the synthesis of IL-17. Thus, a low concentration of PEGylated GO nanoparticles (5 μg/mL), in contrast to a concentration of 25 μg/mL, has no effect on the Th17-polarization of T helpers, allowing their further use for in-depth studies of the functions of T lymphocytes and other immune cells. Overall, we have studied for the first time the direct effect of P-GO nanoparticles on the conversion of T helper cells to the Th17 phenotype.

Evaluating the effect of graphene oxide PEGylation on the properties of chitosan-graphene oxide nanocomposite scaffold

In this study, graphene oxide (GO) was functionalized with polyethylene glycol (PEG) to understand the effect of PEGlayted GO on properties of chitosan-based nanocomposite scaffold. GO was synthesized according to modified Hummer's method and covalently linked to polymeric chains of PEG to produce polyethylene glycolated GO (PGO). Successful preparation of GO and PGO was confirmed by FT-IR and Raman techniques, where the chemical bonding of PEG and GO nanosheets were concluded based on PGOs' lower zeta potential compared to GO. Nanocomposite scaffolds were prepared by adding equal amounts of GO and PGO into 2% (w/v) chitosan (Cs) solutions. The highly porous scaffolds were developed by lyophilization of solutions. Incorporation of GO and PGO into chitosan scaffold network resulted in uniform and spherical pores. Modified samples offered higher porosity and density, indicating adequate scaffold structure. Improvements in the physical properties of prepared chitosan scaffolds were concluded through higher water absorption and retention values. Compressive strength measurement showed 6.33 and 5.5 times improvement respectively for Cs-GO and Cs-PGO samples compared to Cs scaffold. The Cs-GO scaffolds showed minimum susceptibility toward enzymatic degradation and higher degrees of protein adsorption (26% and 23% improvement in value of adsorbed protein respectively for Cs-GO and Cs-PGO compared to Cs scaffold) and biomineral formation on scaffold surface. Also, Cs-PGO sample showed the highest degree of cell viability and lower hemolysis than both Cs and Cs-GO scaffolds. Investigations showed that cell infiltration into scaffold porous structure was more prominent in Cs-PGO scaffolds than in Cs and Cs-GO scaffolds.

Synergistic Antifungal Study of PEGylated Graphene Oxides and Copper Nanoparticles against Candida albicans

The coupling reactions of polyethylene glycol (PEG) with two different nano-carbonaceous materials, graphene oxide (GO) and expanded graphene oxide (EGO), were achieved by amide bond formations. These reactions yielded PEGylated graphene oxides, GO-PEG and EGO-PEG. Whilst presence of the newly formed amide links (NH-CO) were confirmed by FTIR stretches observed at 1732 cm⁻¹ and 1712 cm⁻¹, the associated Raman D- and G-bands resonated at 1311/1318 cm⁻¹ and 1584/1595 cm⁻¹ had shown the carbonaceous structures in both PEGylated products remain unchanged. Whilst SEM images revealed the nano-sheet structures in all the GO derivatives (GO/EGO and GO-PEG/EGO-PEG), TEM images clearly showed the nano-structures of both GO-PEG and EGO-PEG had undergone significant morphological changes from their starting materials after the PEGylated processes. The successful PEGylations were also indicated by the change of pH values measured in the starting GO/EGO (pH 2.6–3.3) and the PEGylated GO-PEG/EGO-PEG (pH 6.6–6.9) products. Initial antifungal activities of selective metallic nanomaterials (ZnO and Cu) and the four GO derivatives were screened against Candida albicans using the in vitro cut-well method. Whilst the haemocytometer count indicated GO-PEG and copper nanoparticles (CuNPs) exhibited the best antifungal effects, the corresponding SEM images showed C. albicans had, respectively, undergone extensive shrinkage and porosity deformations. Synergistic antifungal effects all GO derivatives in various ratio of CuNPs combinations were determined by assessing C. albicans viabilities using broth dilution assays. The best synergistic effects were observed when a 30:70 ratio of GO/GO-PEG combined with CuNPs, where MIC₅₀ 185–225 μm/mL were recorded. Moreover, the decreased antifungal activities observed in EGO and EGO-PEG may be explained by their poor colloidal stability with increasing nanoparticle concentrations.

Molecular Insights into the Loading and Dynamics of Doxorubicin on PEGylated Graphene Oxide Nanocarriers

Molecular dynamics (MD) simulations were performed to investigate the loading and dynamics of doxorubicin (DOX) anticancer drug on graphene oxide (GO) and poly(ethylene glycol) (PEG) decorated GO (PEGGO) nanocarriers in an aqueous environment at human body temperature (310 K) and physiological pH level of 7.4. Mechanisms of DOX adsorption on PEGGO as a function of PEG chain length were revealed. While the total DOX-nanocarrier interaction energy was the same for the DOX/GO (control), DOX/Sh-PEGGO (short PEG chains consisting of 15 repeat units), and DOX/L-PEGGO (long PEG chains consisting of 30 repeat units) within the margin of error, the PEG-DOX interactions increased with an increase in the PEG chain length. At the same time, the PEG-DOX solvent-accessible contact area almost doubled going from the short to long PEG chains. PEGylation of the GO effectively causes an increase in the average water density around the nanocarrier, which can act as a barrier, leading to the DOX migration to the solvated PEG-free part of the GO surface. This effect is more pronounced for shorter PEG chains. The DOX-DOX solvent-accessible contact area is smaller in the DOX/GO system, which means the drug molecules are less aggregated in this system. However, the level of DOX aggregation is slightly higher for the PEGGO systems. The computational results in this work shed light on the fact that increasing the PEG chain length benefits DOX loading on the nanocarrier, revealing an observation that is difficult to acertain through experiments. Moreover, a detailed picture is provided for the DOX adsorption and retention in PEGGO drug delivery systems, which would enable the researchers to improve the drug's circulation time, as well as its delivery and targeting efficiency.

Cytotoxicity of PEGylated graphene oxide on lymphoma cells

Graphene oxide (GO) is a hotspot, especially in the field of biomedical. However, the clinical application of GO is still faces a lot of challenges. In order to improve the solubility and biocompatibility of GO, polyethylene glycol (PEG) was grafted on the surface of graphene oxide by amide reaction. PEGylated graphene oxide (PEG-GO) was characterized using Fourier transform infrared spectroscopy (FTIR). The stability of PEG-GO detected in different solutions. Raji cell was selected as a lymphoma cell model to study the cytotoxicity of PEG-GO. Cell viability was detected using the Cell Counting Kit-8 assay. Cells were treated with different concentrations (10-100 μg/mL) of PEG-GO at different time points (6, 12, and 24 h). The FTIR spectrum of PEG-GO indicated that polyethylene glycol was successfully grafted onto GO. PEG-GO had excellent stability in all solutions. Cells treated with PEG-GO (10-100 μg/mL) for 24 hours had survival rates were over 80%. These results demonstrate that PEG-GO had an excellent dispersion in biological solutions and the toxicity of PEG-GO to lymphoma cells was low. The paper may provide cytological evidence for the application of PEG-GO in medicine.