PubMed · 13213429
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R S ELLERY. 1954-11-06. Gold.. https://doi.org/10.5694/j.1326-5377.1954.tb66943.x
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Sustainable nanomaterial synthesis has emerged as a critical strategy to reduce the environmental burden associated with conventional chemical synthesis method. Microalgae-derived biomolecules offer a promising platform for the green production of metal nanoparticles due to their rich bioactive compounds capable of acting as natural reducing and stabilizing agents. Here, we report the eco-friendly synthesis of gold nanoparticles (AuNPs) using extract of Indonesian microalga Chlorella vulgaris extract. To optimize the synthesis process, the effects of precursor-to-extract ratio, temperature, and incubation time were evaluated. Optimal synthesis of C5-AuNPs was obtained at 37 °C for 20 h with precursor to extract ratio of 6:4, resulting in moderately stable C5-AuNPs characterized by a surface plasmon resonance (SPR) peak at 541 nm. Furthermore, Fourier-transmission infra-red (FT-IR) analysis revealed the involvement of functional groups of C. vulgaris extract in the interaction with Au+ during the production of C5-AuNPs. Transmission electron microscopy (TEM) demonstrated the formation of uniformly spherical nanoparticles with an average diameter of approximately 8.8 nm. Biological evaluation showed that the synthesized C5-AuNPs exerted pronounced dose-dependent cytotoxicity against MCF-7 breast cancer cells with an IC50 threshold of 21.17 ppm, while no toxicity appears in normal HEK293 cells. Mechanistically, the C5-AuNPs induced early apoptosis and inhibit cell-cycle progression at the stage of G0/G1. Collectively, these findings demonstrate that C. vulgaris-mediated AuNPs represent a promising preliminary in vitro findings for cancer therapy candidate.
Peptides containing the tripeptide sequence Arg-Gly-Asp (RGD) have the ability to bind to members of the integrin superfamily of cell-surface receptors and direct cellular adhesion and haptotaxis. The goal of this work is the development of a rapid and effective method for the quantitative submonolayer spatial composition mapping of surfaces displaying molecular assemblies of RGD-containing organomercaptan peptides on a Au surface using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-MS). Quantitation of the RGD peptide is achieved by determining the peak intensity of the protonated molecular ion, (M + H)+, relative to the (M + H)+ peak for an internal standard, which is similar chemically but with glutamic acid (E) substituted for aspartic acid (D). Using optimized sample preparation procedures, a bilinear calibration was obtained between the quantitative peak intensity ratio and the mole fraction of the RGD-containing peptide. Quantitative compositions were determined with relative standard deviations of <10%, even in the presence of 10x spot-to-spot variations in the absolute signal intensities, by using this internal standard approach. This MALDI-MS quantitative analysis method was employed to probe variable-width two-component counterpropagating electrochemically generated gradients of the two peptides, prepared by coupling in-plane electrochemical potential gradients with the electrosorption reactions of organothiols to vary the composition laterally. The measured lateral composition profiles match the quasi-linear potential gradient model and yield profiles that overlap to a high degree of fidelity in potential space. Thus, MALDI-MS spatial composition mapping should become a powerful tool for the preparation of designed surfaces facilitating the study of cellular adhesion and motility and cell-cell interactions.
A new W-Cu target was designed to replace the existing Au target on a linear accelerator model in common use in radiotherapy. This work shows that targets of different material composition can be designed to produce beams with the same dosimetric character over a wide range of beam energies without adjusting the beam energy. The target design objective was to improve mechanical robustness, replacing water in the beam path with a Cu heat sink, without altering the beam properties for the nominal clinical energy range of 4-25 MV. The W-Cu could then be installed in place of the Au target without recommissioning. The effect of the target swap was measured in the test cells for 11 different beams ranging in nominal energy from 4 to 25 MV, with focus on open field dose distributions, including diagonal profiles taken for the largest (40x40 cm) field, measured at 4 different gantry angles. Depth dose curves agreed to 0.4% or better, profiles to 1.2% or better. Monte Carlo simulations of the treatment head were done for representative energies of 6 and 18 MV. Calculated and measured dose distributions generally matched within 1%, although dose measured in the build-up region of large fields was significantly more than in the simulations. Calculated spectral distributions on the central axis and angular distributions of energy fluence matched for the two targets, whereas angular distributions of fluence were significantly different. Matching energy fluence gave a more favorable match of dose profiles than matching fluence. The target was further tested on several machines operating in a radiotherapy clinic. Measurements were made for a wide range of open field sizes and with selected wedges and blocks. Dose distributions for the two targets agreed to 1.4% or better, including the dose in wedged fields. Wedge factors changed by no more than 0.5%, transmission through a 4.4 HVL block no more than 1.5%. The response of the monitor chamber was found to change, generally by 1%-2%. Therefore, when the W-Cu target was used to replace the Au target, the output of the machine was measured and adjusted appropriately, but there was no requirement for recommissioning.