The plasmonic properties of gold nanoparticle clusters formed via applying an AC electric field

Upconverting-photon quenching-mediated perforation influx as an intracellular delivery method using posAuNP@UCNPs nanocomposites for osteoarthritis treatment

Photoporation techniques based on plasmonic nanoparticles such as gold nanoparticles have been extensively studied for the intracellular delivery of substances via cell membrane disruption. However, the clinical application of AuNP is challenging due to its absorption in the 500 nm region of the light spectrum. To overcome this challenge, upconversion nanoparticles were employed to stimulate AuNP at NIR wavelengths. posAuNP@UCNPs nanocomposites were produced by coating 30 nm UCNPs on 80 nm AuNPs using DOPA-PEI, which were then irradiated with 980 nm NIR light to facilitate their intracellular delivery. TEM and DLS confirmed that posAuNP and UCNP combine to form nanocomposites. Additionally, multiphysics simulation was used to analyze the distribution of the posAuNP electric field based on morphological differences that change as the UCNP ratio increases. Next, effective LED irradiation conditions were established by applying upconverting-photon quenching-mediated perforation influx to C28/I2 cells as suspensions or spheroids. posAuNP@UCNP nanocomposites were confirmed to be effective for the delivery of baricitinib as a treatment for osteoarthritis in a three-dimensional osteoarthritis model. Finally, chondrocyte differentiation was induced through intracellular delivery of baricitinib using posAuNP@UCNPs. The findings suggest that posAuNP@UCNPs have great potential as a tool for non-invasive drug delivery via UCPPin.

Plasmonic alloy nanochains assembled via dielectrophoresis for ultrasensitive SERS

It is great challenge and interesting for researchers to fabricate substrates for enhanced Raman and sensor, and assemble some easy-to-synthesize metallic nanomaterials into controllable nanostructures with special morphologies and arrangements, via alternating current (AC) electric field. The Au-Ag alloy nanoparticles (Au-Ag alloy NPs) colloidal suspension with excellent dispersibility synthesized by wet chemical method, and the morphology of the assembly can be well controlled by regulating the frequency of the AC electric field. Au-Ag alloy nanochains array (Au-Ag ANCs) with dense plasmonic "hot spots" is formed when the AC electric field of 4V_pp-30kHz is applied, which is supported by the result of finite element method (FEM) numerical simulation. Experimental results demonstrate that Au-Ag ANCs show excellent SERS activity: Au-Ag ANCs can detect both Rhodamine 6G (Rh6G) and crystal violet (CV) in the magnitude order of 10^-10 M, and the Raman peaks intensity and analyte concentration has a strong linear correlation (R² is 0.99339 and 0.95916, respectively). Besides, the introduction of Au-Ag ANCs makes the Raman spectra intensity of thiram (a pesticide) with a concentration of 30 ppm on the surface of the blank ITO glass significantly enhanced, and it can detect thiram with a concentration as low as 0.03 ppm. In addition, Au-Ag ANCs substrate exhibits great uniformity and stability, so they have considerable application potential in the field of quantitative detection of trace substances.

Au Nanoparticles-Doped Polymer All-Optical Switches Based on Photothermal Effects

This article demonstrated the Au nanoparticles-doped polymer all-optical switches based on photothermal effects. The Au nanoparticles have a strong photothermal effect, which would generate the inhomogeneous thermal field distributions in the waveguide under the laser irradiation. Meanwhile, the polymer materials have the characteristics of good compatibility with photothermal materials, low cost, high thermo-optical coefficient and flexibility. Therefore, the Au nanoparticles-doped polymer material can be applied in optically controlled optical switches with low power consumption, small device dimension and high integration. Moreover, the end-pumping method has a higher optical excitation efficiency, which can further reduce the power consumption of the device. Two kinds of all-optical switching devices have been designed including a base mode switch and a first-order mode switch. For the base mode switch, the power consumption and the rise/fall time were 2.05 mW and 17.3/106.9 μs, respectively at the wavelength of 650 nm. For the first-order mode switch, the power consumption and the rise/fall time were 0.5 mW and 10.2/74.9 μs, respectively at the wavelength of 532 nm. This all-optical switching device has the potential applications in all-optical networks, flexibility device and wearable technology fields.

Effect of TAT-DOX-PEG irradiated gold nanoparticles conjugates on human osteosarcoma cells

The paper aims to investigate the cytotoxic effect on tumor cells of irradiated AuNPs in green light and subsequently functionalized with HS-PEG-NH2. The toxicity level of gold conjugates after their functionalization with DOX and TAT peptide was also evaluated. The AuNPs were prepared using the modified Turkevich method and exposed to visible light at a wavelength of 520 nm prior their PEGylation. The optical properties were analyzed by UV-vis spectroscopy, the surface modification was investigated using FTIR and XPS spectroscopies and their sizes and morphologies were evaluated by TEM and DLS techniques. DOX and TAT peptide were linked to the surface of PEGylated AuNPs by reacting their amino groups with glycidyloxypropyl of PEGylated DOX or TAT conjugates under mild conditions at room temperature and in the presence of ethanol as catalyst. The conjugates containing DOX or DOX and TAT have been characterized by fluorescence and FTIR techniques. The changes of electrochemical features were observed using cyclic voltammetry, suggesting a better stability of irradiated nanoparticles. By mass spectrometry it was confirmed that the compounds of interest were obtained. The cell viability test showed that irradiated and non-irradiated nanoparticles coated with PEG are not toxic in normal cells. Tumor cell viability analysis showed that the PEGylated nanoparticles modified with DOX and TAT peptide were more effective than pristine DOX, indicating cytotoxicity up to 10% higher than non-irradiated ones.

Study of Morphology and Optical Properties of Gold Nanoparticle Aggregates under Different pH Conditions

Gold nanoparticle (GNP) aggregation has a strong influence on the plasmonic resonance and hence the effectiveness in various photothermal applications. In relation to this, a comprehensive numerical model is developed to simulate and characterize the GNP aggregation process at various particle volume fractions and base fluid pH levels. Computational fluid dynamics techniques are utilized to model the base fluid, whereas discrete phase modeling is adopted in determining the nanoparticle trajectories. Two-way coupling is implemented to handle the particle-fluid interactions. Discrete dipole approximation approach is utilized to further examine the absorption and scattering efficiency of various GNP aggregate structures. At lower particle volume fraction, short chain-like structures are formed in the particle aggregation process, with a more complex interconnected "particle network" structure formed at higher particle volume fractions. With the three base fluid pH levels investigated, GNP aggregates are more compact with larger fractal dimensions and higher mean coordination numbers at pH = 3.5, whereas a more "loose" structure formed at pH = 6.7 and 9.4 because of larger electrostatic repulsive forces as a result of changes in the zeta potential and Debye length of the GNPs. Among the typical GNP aggregate structures characterized in this paper, the chain-like tetramer demonstrates the highest absorption efficiency of 1.83 at 700 nm wavelength-comparable to the plasmonic resonance of a nanorod-which lies in the optical window of biological tissue. Predictions of GNP optical properties are found to be in good agreement with the published experimental data.