This work unveils the roles played by potato starch (ST) in the immobilization, photochemical reduction, and gas sensitivity of graphene oxide (GO) films. The ST/GO films are assembled layer by layer ...(LbL) onto quartz substrates by establishing mutual hydrogen bonds that drive a stepwise film growth, with equal amounts of materials being adsorbed in each deposition cycle. Afterward, the films are photochemically reduced with UV irradiation (254 nm), following a first-order kinetics that proceeds much faster when GO is assembled along with ST instead of a nonoxygenated polyelectrolyte, namely, poly(diallyl dimethylammonium) hydrochloride (PDAC). Finally, the gas-sensing performance of ST/reduced graphene oxide (RGO) and PDAC/RGO sensors fabricated via LbL atop of gold interdigitated microelectrodes is evaluated at different relative humidity levels and in different concentrations of ammonia, ethanol, and acetone. In comparison to the PDAC/RGO sensor, the ones containing ST are much more sensitive, especially when operating in a high-relative-humidity environment. An array comprising these chemical sensors provides unique electrical fingerprints for each of the investigated analytes and is capable of discriminating and quantifying them in a wide range of concentrations, from 10 to 1000 ppm.
Our study describes the successful preparation of non toxic Pluronic F127 micelles loading chloroaluminum phthalocyanine, highly efficient in decreasing cancer cells viability, to be applied in ...photodynamic therapy. Display omitted
Phthalocyanine derivatives comprise the second generation of photosensitizer molecules employed in photodynamic therapy (PDT) and have attracted much attention due to their outstanding photosensitizing performance. Most phthalocyanines are hydrophobic compounds that require association to drug delivery systems for clinical use. In this study, formulations of Pluronic F127 micelles incorporated with chloroaluminum phthalocyanine, or else F127/AlClPc, were produced at optimized conditions aiming at efficient and biocompatible PDT colloidal systems. Absorption/emission spectroscopies, as well as dynamic light scattering were performed to evaluate the optimum conditions for the F127 micelle formation and AlClPc incorporation. The micelles formation was attained with F127 concentrations ranging from 50 to 150mgmL−1. At these conditions, AlClPc photosensitizer molecules were encapsulated into the hydrophobic micelle core and, therefore, readily solubilized in physiological medium (PBS pH 7.2).
Encapsulation efficiency of about 90% resulted from different AlClPc concentrations. Identification of singlet oxygen production by irradiated F127/AlClPc formulations indicated good applicability for PDT. In vitro tests conducted with A549 human lung carcinoma cell line incubated with the F127/AlClPc formulations, at different AlClPc loadings, followed by only 18min of light irradiation (660nm LED, fluence of 25.3J/cm2), showed a cellular damage as high as 90% for rather low dosages of AlClPc (0.1–5.0μgmL−1). Further, no cytotoxicity occurred on non-irradiated cells. These findings suggest those F127/AlClPc formulations are highly promising for PDT applications, since they are easily prepared and the incubation and irradiation times are significantly shortened.
Excessive nitrite amounts harm the environment and put public health at high risk. Therefore, accurate and sensitive detection of nitrite in surface and groundwater is mandatory for mitigating its ...adverse effects. Herein, a highly sensitive electrochemical sensor based on carbon screen-printed electrodes (CSPE) surface-modified with photochemically-made gold nanoparticles (AuNPs, ~12 nm) is proposed for nitrite detection. Scanning electron microscopy, cyclic voltammetry, and electrochemical impedance spectroscopy show that AuNPs uniformly coat the CSPE, increase its surface area, and contribute to oxidizing nitrite to much lower potential (+0.5 V vs. Ag/AgCl) and faster rate. Under optimized differential pulse voltammetry conditions, the CSPE/AuNPs-PEI electrode responds linearly (R2 > 0.99) to nitrite within a wide concentration range (0.01–4.0 µM), showing a sensitivity of 0.85 µA·µM−1·cm−2 and limit of detection as low as 2.5 nM. The CSPE/AuNPs-PEI electrode successfully detects nitrite in tap water and canned water of olives, showing no influence of those matrices. In addition, the electrode’s response is highly reproducible since a relative standard deviation lower than 10% is observed when the same electrode is operated in five consecutive measurements or when electrodes of different fabrication batches are evaluated.
The present contribution proposes an optical method for the detection of glyphosate (GLY) using a Cu(II) bis-(oxamate) complex (Cu(opba)2−) as the fluorescent probe. It wa found that in acetonitrile ...solution, its fluorescence increases in the presence of GLY and scales linearly (R2 = 0.99) with GLY concentration in the range of 0.7 to 5.5 µM, which is far below that established by different international regulations. The probe is also selective to GLY in the presence of potential interferents, namely aminomethyl phosphonic acid and N-nitrosoglyphosate. Theoretical results obtained by time-dependent density functional theory coupled to a simplified treatment of the liquid environment by using a self-consistent reaction-field revealed that GLY molecules do not coordinate with the central Cu2+ ion of Cu(opba)2−; instead, they interact with its peripheral ligand through hydrogen bond formation. Thereby, GLY plays mainly the role of the proton donor. The results also suggest that GLY increases the dielectric constant of the medium when it contributes to the stabilization of the excited state of the Cu(opba)2− and enhancement of its fluorescence.
An iron oxide/reduced graphene oxide (ION-RGO) nanocomposite has been fabricated to functionalize a low-cost electrochemical nitrite sensor realized by light-scribed reduced graphene oxide (LRGO) ...electrodes on a PET substrate. To enhance the stability and adhesion of the electrode, the PET substrate was modified by RF oxygen plasma, and a thin layer of the cationic poly (diallyl dimethyl ammonium chloride) was deposited. Raman spectroscopy and scanning electron microscopy coupled to energy-dispersive X-ray spectroscopy (SEM-EDX) reveal that the light-scribing process successfully reduces graphene oxide while forming a porous multilayered structure. As confirmed by cyclic voltammetry, the LRGO electrochemical response to ferri-ferrocyanide and nitrite is significantly improved after functionalization with the ION-RGO nanocomposite film. Under optimized differential pulse voltammetry conditions, the LRGO/ION-RGO electrode responds linearly (R2 = 0.97) to nitrite in the range of 10–400 µM, achieving a limit of detection of 7.2 μM and sensitivity of 0.14 µA/µM. A single LRGO/ION-RGO electrode stands for 11 consecutive runs. The novel fabrication process leads to highly stable and reproducible electrodes for electrochemical sensors and thus offers a low-cost option for the rapid and sensitive detection of nitrite.
This paper reports on a sensitive, selective and reproducible electrochemical sensor for nitrite detection based on laser-induced graphene (LIG) electrode patterned onto a flexible poly(imide) ...substrate and further modified by COOH functionalized multiwalled carbon nanotubes (f-MWCNT) and gold nanoparticles (AuNPs) films. According to Raman spectroscopy, photoluminescence spectroscopy and scanning electron microscopy, the laser induced photothermal reactions produce ultrathin graphene-like sheets emerging from the substrate, which stay connected to the surface forming a three-dimensional microporous structure. This process permits to scribe in a single step and mask-free, working, counter and reference electrodes on a polymeric substrate. Cyclic voltammetry and electrochemical impedance spectroscopy performed in ferri-ferrocyanide redox pair show that the electroactive area of LIG modified by f-MWCNT- AuNPs is increased and the charge-transfer resistance is diminished in comparison to the modification by each nanomaterial alone. The sensor has a linear characteristic (R2 = 0.996) in the nitrite concentration range from 10 μM to 140 μM and a limit of detection of 0.9 μM following the 3Sb/m method. In presence of typical interfering ions, added in 100-fold excess, the sensor shows a relative standard deviation less than 10%. The results show that a single LIG/f-MWCNT-AuNPs electrode can perform electrochemical detection of nitrite for at least seven consecutive runs with a low signal variation of 2.63% corresponding to a nitrite concentration of 90 μM. Furthermore, seven different electrodes fabricated in the same batch performed identically, with a low signal variation of 2.80% corresponding to a nitrite concentration of 90 μM.
Square wave voltammetric detection of nitrite using gold nanoparticles decorated functionalized multiwalled carbon nanotubes modified laser induced graphene electrode. Display omitted
•Electrochemical sensor for detection of NO2- in tap water.•Flexible LIG modified with COOH-MWCNT and AuNPs.•Chemical surface modification of LIG working electrode with carboxyl COOH functionalized multi-walled carbon nanotubes and gold nanoparticles.•NO2− detection in PBS and tap water.•Interference study with other common ions such as Cl−, NO3−, SO42−, K+, and Ca2+.
The present contribution reports a novel electrode based on an ITO substrate surface-modified with a nanofilm of nickel tetrasulfonated phthalocyanine (NiTsPc) with cerium oxide nanoparticles (CeO2) ...for the effective differential pulse voltammetric detection of acetaminophen, which is a contaminant of emerging concern (CEC). The optimized ITO/NiTsPc/CeO2 electrode responds linearly (r2 > 0.99) to acetaminophen in the range of 0.4 to 11.2 µM, with a limit of detection (S/N = 3) of 54.7 nM. This response is reproducible for fourteen consecutive runs (RSD = 10.97%) and insensitive to the presence of interfering CECs (amoxicillin, atenolol, caffeine, diclofenac, ethinyl estradiol, and ibuprofen) at the same concentration. The electrode can be used to detect acetaminophen in tap water, synthetic urine, and pharmaceutical tablets, in which it performs similarly to UV-Vis spectroscopy at a 95% confidence level.
Background
Cancer constitutes group of diseases responsible for the second largest cause of global death, and it is currently considered one of the main public health concerns nowadays. Early ...diagnosis associated with the best choice of therapeutic strategy, is essential to achieve success in cancer treatment. In women, breast cancer is the second most common type, whereas ovarian cancer has the highest lethality when compared to other neoplasms of the female genital system. The present work, therefore, proposes the association of methylene blue with citrate-coated maghemite nanoparticles (MAGCIT–MB) as a nanocomplex for the treatment of breast and ovarian cancer.
Results
In vitro studies showed that T-47D and A2780 cancer cell lines underwent a significant reduction in cell viability after treatment with MAGCIT–MB, an event not observed in non-tumor (HNTMC and HUVEC) cells and MDA-MB-231, a triple-negative breast cancer cell line. Flow cytometry experiments suggest that the main mechanism of endocytosis involved in the interiorization of MAGCIT–MB is the clathrin pathway, whereas both late apoptosis and necrosis are the main types of cell death caused by the nanocomplex. Scanning electron microscopy and light microscopy reveal significant changes in the cell morphology. Quantification of reactive oxygen species confirmed the MAGCIT–MB cytotoxic mechanism and its importance for the treatment of tumor cells. The lower cytotoxicity of individual solution of maghemite nanoparticles with citrate (MAGCIT) and free methylene blue (MB) shows that their association in the nanocomplex is responsible for its enhanced therapeutic potential in the treatment of breast and ovarian cancer in vitro.
Conclusions
Treatment with MAGCIT–MB induces the death of cancer cells but not normal cells. These results highlight the importance of the maghemite core for drug delivery and for increasing methylene blue activity, aiming at the treatment of breast and ovarian cancer.
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