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Self-Propelled Nanomotors
Published in Klaus D. Sattler, st Century Nanoscience – A Handbook, 2020
FCS is a single-molecule method that measures fluctuations in fluorescence intensity as a result of particles diffusing in and out of a diffraction-limited confocal volume. It requires the particles to be fluorescent. The advantage of this method lies in its selectivity, as only the motion of fluores-cent particles is detected, while unlabeled impurities remain undetected (Figure 13.8).
Optical Methods of Single Molecule Detection and Applications in Biosensors
Published in George K. Knopf, Amarjeet S. Bassi, Smart Biosensor Technology, 2018
Anna Shahmuradyan, Ulrich J. Krull
Fluorescence correlation spectroscopy (FCS) measures the time-dependent fluctuating fluorescence intensity in a defined area or volume of optical interrogation as the number of fluorescent molecules changes due to diffusion, or due to transition between fluorescent and nonfluorescent states (19,41,42). The name of this fluorescence method is given by the mathematical process of signal analysis. The light intensity emitted from the sampling zone is proportional to the number of fluorescent molecules present, and the fluorescence intensity signal will change as a result of any chemical and photophysical reactions, and conformational alterations of these fluorescent molecules (19). By temporally autocorrelating the fluorescence intensity i.e. comparing the similarity between observations as a function of time difference between the measurements, the signal fluctuations can be quantified in terms of strength and duration. For a small number of molecules present in the detection volume, the fluctuations in the light intensity are large considering the amplitude and decay rate. FCS has been used as a tool to study single molecule behaviour where the sample volume is on the order of nano- or pico-liters (42). Very low focal volume and a high quantum yield of the fluorophore are desired (42).
Review of Nanoscale Spectroscopy in Medicine
Published in Sarhan M. Musa, Nanoscale Spectroscopy with Applications, 2018
Chintha C. Handapangoda, Saeid Nahavandi, Malin Premaratne
FCS is a technique that can be used to investigate a variety of biological processes such as protein-protein interactions, binding equilibria for drugs, and clustering of membrane-bound receptors (Prasad 2003). In this technique, the sample (either in vitro or in vivo) is illuminated by a light source focused to a very small volume, typically in the order of 1 ll. or less. The fluorescence originating from particles diffusing in and out of the detection volume is recorded (Jameson et al. 2009). Therefore, in FCS, spontaneous fluorescence intensity fluctuations in a microscopic volume consisting of only a small number of molecules are monitored as a function of time (Prasad 2003).
In situ characterizations for EPS-involved microprocesses in biological wastewater treatment systems
Published in Critical Reviews in Environmental Science and Technology, 2019
Peng Zhang, Bo Feng, You-Peng Chen, You-Zhi Dai, Jin-Song Guo
Nutrient substrates or toxic substances that enter the microbial aggregates could either diffuse into the EPS matrix or bind onto EPS. The diffusion or binding affects the utilization rate of substrates, the toxicity effect of toxicants, and the migration and fate of toxicants in the water environment. The diffusion process and binding kinetics are associated with the porosity of microbial aggregates, the solution chemistry, and the surface charge, hydrophobicity, and binding sites in EPS. FCS is a type of fluorescence spectroscopy technique that analyzes the fluorescence intensity versus time. FCS can measure the fluorescence intensity fluctuation of a fluorophore caused by Brownian motion or a chemical reaction in the micro area.
Anion exchange membrane fuel cell modelling
Published in International Journal of Sustainable Energy, 2018
P. Fragiacomo, E. Astorino, G. Chippari, G. De Lorenzo, W. T. Czarnetzki, W. Schneider
The fuel cell (FC) is a technology that can be based upon sustainable sources of energy. FCs are devices that convert the chemical energy stored in some fuels directly into electrical energy and heat. The preferred fuel for many FCs is hydrogen, which is a renewable source of energy; hence FC technology has received considerable attention in recent years.
Block catiomer with flexible cationic segment enhances complexation with siRNA and the delivery performance in vitro
Published in Science and Technology of Advanced Materials, 2021
Wenqian Yang, Takuya Miyazaki, Pengwen Chen, Taehun Hong, Mitsuru Naito, Yuji Miyahara, Akira Matsumoto, Kazunori Kataoka, Kanjiro Miyata, Horacio Cabral
Because the size of PEG-PLL PICs is too small for precise assessment by DLS with Zetasizer even at the polymer concentration of 10 mg/mL, we then studied the complexation behavior of siRNA with PEG-PLL and PEG-PGBA by FCS. In the FCS measurement, fluorescence is used for recording the diffusion time of molecules. Thus, Cy5-labeled siRNA was used at a diluted concentration of 20 nM to avoid saturation of the fluorescence signal. Accordingly, the changes in D of Cy5-siRNA were measured by FCS after mixing with the catiomers at increasing N/P ratio, while keeping the total concentration of anionic and cationic residues constant to avoid changes in the ionic strength [30]. In the complexation of PEG-PLL and Cy5-siRNA, D decreased from 142 ± 5 μm2/s of free Cy5-siRNA to 113 ± 4 μm2/s of uPICs with the increasing of N/P above 1 (Figure 2(d)). Adding more PEG-PLL to siRNA did not induce significant changes in D, which supports the steady formation of uPICs as observed in previous reports [18]. In addition, the hydrodynamic diameter of PEG-PLL uPICs was calculated based on diffusion coefficient obtained from the FCS measurements (Supplementary Figure 5). The results showed that the uPICs of PEG-PLL/siRNA at N/P equal to – and higher than – 1 are approximately 7 nm, which is consistent with the previously reported diameter of 8.7 nm [18]. In the case of PEG-PGBA, the diffusion coefficient decreased to the level of uPIC with increasing of N/P to 1. It is worth noting that the different siRNA concentrations in the DLS and FCS measurements affected the formation of PEG-PGBA/siRNA PICs at N/P = 1.0. Thus, the PEG-PGBA/siRNA PICs exhibited a diameter of 104 nm and polydispersity index (PDI) of 0.13 by DLS (Figure 2(a,b)), though the normalized derived count rate for this sample was still quite low, suggesting a small amount of multimolecular PICs being formed in the solution. These multimolecular PICs of PEG-PGBA/siRNA at N/P = 1.0 observed in DLS at 10 μM are not stable upon dilution to 20 nM, becoming uPICs as indicated by the FCS results. Both PEG-PGBA/siRNA and PEG-PLL/siRNA PICs were also found to have comparable levels of diffusion coefficient at N/P = 1 by FCS, indicating the formation of uPICs for both polymers.