Inhibitory Impacts of Fulvic Acid-Coated Iron Oxide Nanoparticles on the Amyloid Fibril Aggregations.

Alzheimer's disease is considered as multi-factor diseases, the main hallmarks of which are extracellular amyloid-beta and intracellular tau protein aggregations, leading to neural death. With this in mind, most of the studies have been focused on eliminating these aggregations. Fulvic acid is one of the polyphenolic compounds which exhibits strong anti-inflammation and anti-amyloidogenic effects. On the other hand, iron oxide nanoparticles are able to reduce/eliminate the amyloid aggregations. Here in, the effect of fulvic acid-coated iron-oxide nanoparticles on the commonly used in-vitro model for amyloid aggregation studies, i. e., lysozyme from chicken egg white was investigated. The chicken egg white lysozyme forms the amyloid aggregation under acidic pH and high heat. The average size of nanoparticles was 10.7±2.7 nm. FESEM, XRD, and FTIR confirmed that fulvic acid was coated onto the surface of the nanoparticles. The inhibitory effects of the nanoparticles were verified by Thioflavin T assay, CD, and FESEM analysis. Furthermore, the toxicity of the nanoparticles on the neuroblastoma SH-SY5Y was assessed through MTT assay. Our results indicate that these nanoparticles efficiently inhibit amyloid aggregation formation, while exhibiting no in-vitro toxicity. This data shed light on the anti-amyloid activity of the nanodrug; paving the way for future drug development for treating Alzheimer's disease.

Photothermal treatment of glioblastoma cells based on plasmonic nanoparticles.

Photothermal therapy based on plasmonic gold nanoparticles is considered a promising approach for cancer treatment. Here, we investigate the in vitro photothermal effect of 30-nm gold nanoparticles, optically excited with a 532-nm continuous laser, on the U87MG malignant glioblastoma cells, and demonstrate the role of nanoparticle concentration and exposure power density in achieving its optimum performance. Laser-induced collective oscillation of electrons in plasmonic gold nanoparticles is employed to generate localized heat to denature tumor cells. Optical spectroscopy is used to measure the plasmonic band of nanoparticles and select the excitation laser light. The MTT assay for the IC50 viability assessment is performed to evaluate the live and metabolically active cells after treatment with plasmonic nanoparticles. The quantitative data is statistically analyzed using analysis of variance followed by Tukey's post hoc test. The viability test demonstrates that the metabolic activity of treated U87MG was decreased compared with untreated cells, leading to the determination of the IC50 as 92 [Formula: see text]. A 532-nm laser light was selected for the excitation of gold nanoparticles since the maximum plasmonic band is at 524 nm. The viability tests show that although cells have natural photothermal agents, their absorption efficiency is very low; therefore, the laser-induced plasmonic effect is necessary to observe photothermal effects. The optimal condition was achieved when the nanoparticle concentration was 92 [Formula: see text], and the exposure power density was 96 [Formula: see text]. Thus, it is demonstrated that plasmonic nanoparticle concentration and laser exposure power density are among the key parameters in the photothermal treatment of cancer cells, and higher concentrations of Au-NPs and laser power density lead to less cell viability in the selected range due to the excitation of gold nanoparticles' localized surface plasmon resonance.

Multi-Mode Lanthanide-Doped Ratiometric Luminescent Nanothermometer for Near-Infrared Imaging within Biological Windows.

Owing to its high reliability and accuracy, the ratiometric luminescent thermometer can provide non-contact and fast temperature measurements. In particular, the nanomaterials doped with lanthanide ions can achieve multi-mode luminescence and temperature measurement by modifying the type of doped ions and excitation light source. The better penetration of the near-infrared (NIR) photons can assist bio-imaging and replace thermal vision cameras for photothermal imaging. In this work, we prepared core-shell cubic phase nanomaterials doped with lanthanide ions, with Ba2LuF7 doped with Er3+/Yb3+/Nd3+ as the core and Ba2LaF7 as the coating shell. The nanoparticles were designed according to the passivation layer to reduce the surface energy loss and enhance the emission intensity. Green upconversion luminescence can be observed under both 980 nm and 808 nm excitation. A single and strong emission band can be obtained under 980 nm excitation, while abundant and weak emission bands appear under 808 nm excitation. Meanwhile, multi-mode ratiometric optical thermometers were achieved by selecting different emission peaks in the NIR window under 808 nm excitation for non-contact temperature measurement at different tissue depths. The results suggest that our core-shell NIR nanoparticles can be used to assist bio-imaging and record temperature for biomedicine.

Dual-mode nanophotonic upconversion oxygen sensors.

Nanophotonic biosensors capable of being excited in the NIR spectrum have applications in various sectors. Here, we develop a 980 nm-excitable nanophotonic sensor for real-time oxygen detection in both water and air by analyzing the photoluminescence lifetime and intensity using a nanocomposite of lanthanide-doped NaYF4:Yb3+,Tm3+ upconversion nanoparticles and a PtTFPP platinum porphyrin complex in a polystyrene matrix. Excellent overlap between the emission of the upconversion nanoparticles and the excitation band of the PtTFPP guarantees 68% efficient excitation of the PtTFPP molecules with a 980 nm NIR laser. For the first time, the oxygen sensitivity of the upconversion nanoparticles alone was reported, and it was demonstrated that the PL lifetime-based sensitivity slope was boosted more than 10 times by adding PtTFPP oxygen-sensitive molecules due to the energy transfer from the upconversion nano-emitters. In addition, the functionality of the upconversion-based sensor was investigated by analyzing its sensitivity, stability, reversibility, and temperature-dependent lifetime in both water and air, and its performance was compared with that of the sensor exposed to direct excitation at 410 nm. More importantly, the sensor was implanted under the skin of a chicken, and it was demonstrated that the PL intensity was amplified more than 12 times by employing the 980 nm excitation laser instead of 410 nm laser light. Therefore, excellent emission of the sensor under the skin paves the way for the development of implantable oxygen sensor platforms.

Hybrid Dissolved-Oxygen and Temperature Sensing: A Nanophotonic Probe for Real-Time Monitoring of Chlorella Algae.

Dissolved-oxygen concentration and temperature are amongst the crucial parameters required for the precise monitoring of biological and biomedical systems. A novel hybrid nanocomposite probe for real-time and contactless measurement of both dissolved-oxygen concentration and temperature, based on a combination of downconverting phosphorescent molecules of platinum octaethylporphyrin and lanthanide-doped upconverting nanoparticles immobilized in a host of polystyrene, is here introduced. Chlorella algae are employed here as a model to demonstrate the hybrid nanophotonic sensor's capability to monitor the aforementioned two parameters during the photosynthesis process, since these are among the parameters impacting their production efficiency. These algae have attracted tremendous interest due to their potential to be used for diverse applications such as biofuel production; however, feasibility studies on their economic production are still underway.

Nanoplasmonically-engineered random lasing in organic semiconductor thin films.

We demonstrate plasmonically nano-engineered coherent random lasing and stimulated emission enhancement in a hybrid gain medium of organic semiconductors doped with core-shell plasmonic nanoparticles. The gain medium is composed of a 300 ± 2 nm thin waveguide of an organic semiconductor, doped with 53 nm gold nanoparticle cores, isolated within silica shells. Upon loading the nanoparticles, the threshold of amplified spontaneous emission is reduced from 1.75 µJ cm-2× 102 for an undoped gain medium, to 0.35 µJ cm-2× 102 for a highly concentrated gain medium, and lasing spikes narrower than 0.1 nm are obtained. Most importantly, selection of silica shells with thicknesses of 10, 17 and 21 nm enables engineering of the plasmon-exciton energy coupling and consequently tuning of the laser slope efficiency. With this approach, the slope efficiency is increased by two times by decreasing the silica shell from 21 nm down to 10 nm, due to the enhancement of the localized electric field.