Exploring the chemical sensitivity of a carbon nanotube/green tea composite

Polyphenol-Containing Nanoparticles: Synthesis, Properties, and Therapeutic Delivery

Polyphenols, the phenolic hydroxyl group-containing organic molecules, are widely found in natural plants and have shown beneficial effects on human health. Recently, polyphenol-containing nanoparticles have attracted extensive research attention due to their antioxidation property, anticancer activity, and universal adherent affinity, and thus have shown great promise in the preparation, stabilization, and modification of multifunctional nanoassemblies for bioimaging, therapeutic delivery, and other biomedical applications. Additionally, the metal-polyphenol networks, formed by the coordination interactions between polyphenols and metal ions, have been used to prepare an important class of polyphenol-containing nanoparticles for surface modification, bioimaging, drug delivery, and disease treatments. By focusing on the interactions between polyphenols and different materials (e.g., metal ions, inorganic materials, polymers, proteins, and nucleic acids), a comprehensive review on the synthesis and properties of the polyphenol-containing nanoparticles is provided. Moreover, the remarkable versatility of polyphenol-containing nanoparticles in different biomedical applications, including biodetection, multimodal bioimaging, protein and gene delivery, bone repair, antibiosis, and cancer theranostics is also demonstrated. Finally, the challenges faced by future research regarding the polyphenol-containing nanoparticles are discussed.

Solid State Sensors for Hydrogen Peroxide Detection

Hydrogen peroxide (H2O2) is a key molecule in numerous physiological, industrial, and environmental processes. H2O2 is monitored using various methods like colorimetry, luminescence, fluorescence, and electrochemical methods. Here, we aim to provide a comprehensive review of solid state sensors to monitor H2O2. The review covers three categories of sensors: chemiresistive, conductometric, and field effect transistors. A brief description of the sensing mechanisms of these sensors has been provided. All three sensor types are evaluated based on the sensing parameters like sensitivity, limit of detection, measuring range and response time. We highlight those sensors which have advanced the field by using innovative materials or sensor fabrication techniques. Finally, we discuss the limitations of current solid state sensors and the future directions for research and development in this exciting area.

Biogenic synthesis of a green tea stabilized PPy/SWCNT/CdS nanocomposite and its substantial applications, photocatalytic degradation and rheological behavior

A green tea leaf-derived cadmium sulfide quantum dot-based system containing different weight percentages of single-walled carbon nanotubes (SWCNTs) and polypyrrole, named PSC, was designed via a green method. The photocatalytic degradation of Ponceau BS dye (λ _max 505 nm) in the presence of PSC was measured. PSC with the highest weight percentage of SWCNTs (7-PSC) showed maximum photocatalytic activity, with 94.6% dye degradation in 55 minutes of irradiation time. This significant enhancement was due to the synergism in the intrinsic properties of the parent components. Alongside this, the rheological behavior of the prepared nanomaterial PSC was examined at constant (100 s^-1) and varying shear rate from 0 to 500 s^-1 at a fixed temperature of 25 °C for a specified volume percentage of 0.1% using Castrol class: 15W-40 engine oil as a base fluid. The objective of lowering the viscosity of engine oil by 98.9% (initial: 0.221000 Pa s, final: 0.0022 Pa s.) was achieved by chartering/mixing the prepared PSC nanomaterial into the engine oil. A comparative study of the experimental and simulation outputs implied the high precision of the modeling via a neural network with minute 0.373 average % errors.

Amyloid-Polyphenol Hybrid Nanofilaments Mitigate Colitis and Regulate Gut Microbial Dysbiosis

It is a desirable and powerful strategy to precisely fabricate functional soft matter through self-assembly of molecular building blocks across a range of length scales. Proteins, nucleic acids, and polyphenols are the self-assemblers ubiquitous in nature. Assembly of proteins into flexible biocolloids, amyloid fibrils with high aspect ratio, has emerged as an unchallenged templating strategy for high-end technological materials and bio-nanotechnologies. We demonstrate the ability of these fibrils to support the deposition and self-assembly of polyphenols into hybrid nanofilaments and functional macroscopic hydrogels made thereof. The length scale of the substance that amyloid fibrils can attach with acting as the building templates was extended from nanometer down to sub-nanometer. Significantly increased loading capacities of polyphenols (up to 4.0 wt %) compared to that of other delivery systems and improved stability were realized. After oral administration, the hydrogels could transport from the stomach to the small intestine and finally to the gut (cecum, colon, rectum), with a long retention time in the colon. Oral administration of the hydrogels significantly ameliorated colitis in a mouse model, promoted intestinal barrier function, suppressed the pro-inflammatory mRNA expression, and very significantly (P < 0.01) regulated gut microbial dysbiosis. Specifically, it reduced the abundance of normally enriched operational taxonomic units related to colitis, especially targeting facultative anaerobes of the phylum Proteobacteria, such as Aestuariispira and Escherichia. The short-chain fatty acid metabolites were enriched. Combined with their nontoxic nature observed in this long-term study in mice, the obtained amyloid-polyphenol gels have high application potentials for gastrointestinal diseases by "drugging the microbiome".

Devising Carbon Nanotube, Green Tea, and Polyaniline Based Nanocomposite plus Investigating Its Rheological together with Bactericidal Efficacies

Subsequently, engines are designed to operate at low viscosity engine oils. Low viscosity oils take less power from engines, bring down the internal drag, cut the fuel consumption, and ultimately improve the engine's efficiency. Considering this focus, an approach has been made to formulate a multiwalled carbon nanotube based green tea and polyaniline nanocomposite, that is, GT/MWCNT/PANI, and incorporate it in engine oil (base fluid). The objective was to reduce the viscosity of engine oil by examining the effects of the constant shear rate and varying shear rates on the viscosity of Castrol class 15W-40 engine oil. The investigation was performed at a constant temperature of 25 °C for a fixed volume fraction of 0.1% GT/MWCNT/PANI in engine oil on the experimental setup rheometer from Anton Paar Series. Primordial findings revealed that, at a constant shear rate of 100 s-1, engine oil viscosity was lowered from 0.221000 to 0.001402 Pa·s, that is, 99% reduction in viscosity of the engine oil, after incorporating the GT/MWCNT/PANI nanocomposite. Furthermore, a new correlation has been proposed considering the experimental and theoretical models with an average percentage error of 0.040%. Also, at varying shear rates, up to 90 s-1, the shear viscosity of nanofluid decreases significantly, leading to shear-thinning behavior of the nanofluid, while at a shear rate of >90 s-1, it shows Newtonian behavior. Besides, the ternary nanocomposite with 0.2 wt % GT/MWCNT/PANI also showed significant bactericidal effects with the zones of inhibition of 19, 18, and 15 mm against Gram-negative (Pseudomonas aeruginosa, Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria, respectively, as measured using the well diffusion method.

Grafting of Gallic Acid onto a Bioactive Ti6Al4V Alloy: A Physico-Chemical Characterization

Despite increasing interest in the use of natural biomolecules for different applications, few attempts of coupling them to inorganic biomaterials are reported in literature. Functionalization of metal implants with natural biomolecules could allow a local action, overcoming the issue of low bioavailability through systemic administration. In the present work, gallic acid was grafted to a pre-treated Ti6Al4V in order to improve its biological response in bone contact applications. The grafting procedure was optimized by choosing the concentration of gallic acid (1 mg/mL) and the solvent of the solution, which was used as a source for functionalization, in order to maximize the amount of the grafted molecule on the titanium substrate. The functionalized surfaces were characterized. The results showed that functionalization with Simulated Body Fluid (SBF) as solvent medium was the most effective in terms of the amount and activity of the grafted biomolecule. A key role of calcium ions in the grafting mechanism is suggested, involving the formation of coordination compounds formed by way of gallic acid carboxylate and Ti–O− as oxygenated donor groups. Bioactive behavior and surface charge of the pre-treated Ti6Al4V surface were conserved after functionalization. The functionalized surface exposed a greater amount of OH groups and showed higher wettability.

ROS-responsive capsules engineered from green tea polyphenol–metal networks for anticancer drug delivery

Reactive oxygen species (ROS)-responsive nanocapsules for cancer drug delivery were engineered from green tea polyphenol–metal networks.

High efficient anti-cancer drug delivery systems using tea polyphenols reduced and functionalized graphene oxide

Targeted drug delivery is urgently needed for cancer therapy, and green synthesis is important for the biomedical use of drug delivery systems in the human body. In this work, we report two targeted delivery systems for anticancer drugs based on tea polyphenol functionalized and reduced graphene oxide (TPGs). The obtained TPGs demonstrated an efficient doxorubicin loading capacity as high as 3.430 × 106 mg g−1 and 3.932 × 104 mg g−1, and exhibited pH-triggered release. Furthermore, the kinetic models, adsorption isotherms, and possible loading mechanisms were investigated in details. Compared to TPG1 and free doxorubicin, TPG2 is biocompatible to normal cells even at high concentrations and promotes tumor cells death by delivering the doxorubicin mainly to the nuclei. These results were confirmed using cell viability tests and confocal laser microscopy. Moreover, apoptosis tests showed that the mechanism of cancer cell death induced by TPG1 and TPG2 might follow the similar mechanisms. Taken together, these results demonstrate that TPGs provide a multifunctional drug delivery system with a greater loading capacity and pH-sensitive drug release for enhanced cancer therapy. The high drug payload capability and enhanced antitumor efficacy demonstrate that we developed systems are promising for various biomedical applications and cancer therapy.

Oligomer-coated carbon nanotube chemiresistive sensors for selective detection of nitroaromatic explosives

High-performance chemiresistive sensors were made using a porous thin film of single-walled carbon nanotubes (CNTs) coated with a carbazolylethynylene (Tg-Car) oligomer for trace vapor detection of nitroaromatic explosives. The sensors detect low concentrations of 4-nitrotoluene (NT), 2,4,6-trinitrotoluene (TNT), and 2,4-dinitrotoluene (DNT) vapors at ppb to ppt levels. The sensors also show high selectivity to NT from other common organic reagents at significantly higher vapor concentrations. Furthermore, by using Tg-Car/CNT sensors and uncoated CNT sensors in parallel, differential sensing of NT, TNT, and DNT vapors was achieved. This work provides a methodology to create selective CNT-based sensors and sensor arrays.

Nanostructuring of biosensing electrodes with nanodiamonds for antibody immobilization

While chemical vapor deposition of diamond films is currently cost prohibitive for biosensor construction, in this paper, we show that sonication-assisted nanostructuring of biosensing electrodes with nanodiamonds (NDs) allows harnessing the hydrolytic stability of the diamond biofunctionalization chemistry for real-time continuous sensing, while improving the detector sensitivity and stability. We find that the higher surface coverages were important for improved bacterial capture and can be achieved through proper choice of solvent, ND concentration, and seeding time. A mixture of methanol and dimethyl sulfoxide provides the highest surface coverage (33.6 ± 3.4%) for the NDs with positive zeta-potential, compared to dilutions of dimethyl sulfoxide with acetone, ethanol, isopropyl alcohol, or water. Through impedance spectroscopy of ND-seeded interdigitated electrodes (IDEs), we found that the ND seeds serve as electrically conductive islands only a few nanometers apart. Also we show that the seeded NDs are amply hydrogenated to be decorated with antibodies using the UV-alkene chemistry, and higher bacterial captures can be obtained compared to our previously reported work with diamond films. When sensing bacteria from 10(6) cfu/mL E. coli O157:H7, the resistance to charge transfer at the IDEs decreased by ∼ 38.8%, which is nearly 1.5 times better than that reported previously using redox probes. Further in the case of 10(8) cfu/mL E. coli O157:H7, the charge transfer resistance changed by ∼ 46%, which is similar to the magnitude of improvement reported using magnetic nanoparticle-based sample enrichment prior to impedance detection. Thus ND seeding allows impedance biosensing in low conductivity solutions with competitive sensitivity.

Green tea polyphenol–reduced graphene oxide: derivatisation, reduction efficiency, reduction mechanism and cytotoxicity

This paper reports on the derivatisation, reduction efficiency, reduction mechanism and cytotoxicity of green tea polyphenol–reduced graphene oxide (GTP–RGO).

Protonation of epigallocatechin-3-gallate (EGCG) results in massive aggregation and reduced oral bioavailability of EGCG-dispersed selenium nanoparticles

The current results show that epigallocatechin-3-gallate (EGCG), in the form of phenolic anions at pH 8.0, can effectively disperse selenium nanoparticles. However, at gastric juice pH (1.0), the EGCG-dispersed selenium nanoparticles (referred to as E-Se) extensively aggregated, so that nano features largely disappeared. This demonstrates that deprotonated phenolic anions of EGCG play an important role in maintaining E-Se stability and suggests that E-Se would suffer from reduced oral bioavailability. To validate this conjecture, size-equivalent E-Se and bovine serum albumin (BSA)-dispersed selenium nanoparticles (B-Se), whose physicochemical properties were not altered at pH 1.0, were orally administered to selenium-deficient mice. In comparison to B-Se, the bioavailabilities of E-Se as indicated with hepatic and renal glutathione peroxidase activity and hepatic selenium levels were significantly (p < 0.01) reduced by 39, 32, and 31%, respectively. Therefore, the present study reveals that size-equivalent selenium nanoparticles prepared by different dispersers do not necessarily guarantee equivalent oral bioavailability.

Remotely actuated shape memory effect of electrospun composite nanofibers

One class of biodegradable polymer composite nanofibers was fabricated with an electrospinning process using chemically cross-linked poly(ε-caprolactone) (c-PCL) as the matrix and multiwalled carbon nanotubes (MWNTs) as the reinforced filler coated with Fe(3)O(4) nanoparticles as a magnetism responsive source. The composite fibers showed an excellent shape memory effect, triggered both by hot water and by an alternating magnetic field. The heat in the PCL matrix generated from magnetic nanoparticles via hysteresis loss in the magnetic field was also determined quantitatively. The Fe(3)O(4)-loaded MWNT composite nanoparticles (Fe(3)O(4)@CD-M) were synthesized through two steps: (1) the raw MWNTs were firstly functionalized by grafting maleic anhydride (MA) on their surface through a free radical reaction and later covalently modified by β-cyclodextrin (β-CD) through an esterification reaction; (2) Fe(3)O(4)@CD-M composite nanoparticles were prepared by chemical co-precipitation of Fe(2+) and Fe(3+) ions on the surface of the β-CD functionalized MWNTs with an electrostatic self-assembly approach using β-CD as the depositional locus. Alamar blue assay was also performed from culturing osteoblast populations to evaluate the cytotoxicity. The result showed that the electrospun composite fibers possessed good biocompatibility and could be applied in biomedical fields.

Controlled green tea polyphenols release from electrospun PCL/MWCNTs composite nanofibers

Poly(ɛ-caprolactone)/multi-walled carbon nanotubes (PCL/MWCNTs) composite nanofibers with various content of green tea polyphenols (GTP) were successfully fabricated via an electrospinning technology to maintain the chemical structural stability of GTP. The non-covalent interaction between MWCNTs and GTP was measured by UV-vis spectrophotometer and FT-IR. The topographical features of the nanofibers were characterized by scanning electron microscopy (SEM). The dispersibility of MWCNTs and the distribution of GTP in nanofibers were observed by transmission electron microscopy (TEM) and laser scanning confocal microscope (LSCM), respectively. In vitro degradation was also characterized in terms of the morphological change and the mass loss of the nanofiber meshes. In vitro GTP release behavior was investigated in phosphate-buffered solution (PBS) at 37°C. Alamar blue assays were performed to estimate the cytotoxicity of the nanofibers with normal osteoblast cells and the antiproliferative effects to A549 and Hep G2 tumor cells. The results exhibited that the GTP-loaded composite nanofibers possessed a significant inhibition effect to tumor cells. Therefore, GTP, as a multifunctional drug, encapsulated into polymer composite nanofibers, must have broad application prospects in cancer therapy.

Facile synthesis of soluble graphene via a green reduction of graphene oxide in tea solution and its biocomposites

The chemical reduction of graphene oxide (GO) typically involves highly toxic reducing agents that are harmful to human health and environment, and complicated surface modification is often needed to avoid aggregation of the reduced GO during reduction process. In this paper, a green and facile strategy is reported for the fabrication of soluble reduced GO. The proposed method is based on the reduction of exfoliated GO in green tea solution by making use of the reducing capability and the aromatic rings of tea polyphenol (TP) that contained in tea solution. The measurements of the resultant graphene confirm the efficient removal of the oxygen-containing groups in GO. The strong interactions between the reduced graphene and the aromatic TPs guarantee the good dispersion of the reduced graphene in both aqueous and a variety of organic solvents. These features endow this green approach with great potential in constructing of various graphene-based materials, especially for high-performance biorelated materials as demonstrated in this study of chitosan/graphene composites.