The team demonstrated its capability by successfully imaging nanoscale defects over a period of 6 hours in a micrometer-sized, two-dimensional (2D) tungsten disulfide (WS 2) film – a material commonly used in optoelectronic devices. Ryo Kato, a designated Assistant Professor at the Institute of Post-LED Photonics at Tokushima University, and Associate Professor Takayuki Umakoshi and Professor Prabhat Verma from Osaka University, has now developed, for the first time, a stable TERS system that is not limited to a short imaging time window. ![]() In a new study published in Science Advances, a research team from Japan, led by Dr. To avoid this, TERS imaging needs to be completed within a time window of 30 minutes, a restriction that prevents imaging of any sample larger than 1 µm 2 with nanoscale resolution. This causes considerable distortions in the scattered signals. However, during imaging, the nanotip tends to drift due to unavoidable thermal and vibrational fluctuations under ambient conditions, causing either the sample to be out-of-focus or misalignment between the nanotip and focal spot, or both. TERS has been successfully used to analyze chemical compositions and surface defects in sample at nanoscale resolutions. The light interacts with the sample molecules on the surface and the imaging is performed by analyzing the scattered light. In TERS, a metallic nano-sized tip confines the light within a nano-sized volume just above the sample. All rights reserved.To improve the spatial resolution, another technique called “tip-enhanced Raman spectroscopy” (TERS) was invented, which can reach spatial resolutions below the diffraction limit. Thus, we concluded that qLD enables covering of the overlapping particle size range between RMM and FI.Īntibody(s) biopharmaceutical characterization microparticle(s) nanoparticle(s) protein aggregation protein formulation(s).Ĭopyright © 2019 The Authors. Both particle size distribution and concentration were in good agreement between RMM and qLD (0.3-2 μm) and between FI and qLD (2-20 μm). In addition, size distribution of a protein aggregates solution was compared by RMM, NTA, FI, LO, and qLD. Serial dilutions of the aggregates stock were analyzed by RMM, FI, and qLD to obtain the particle size distribution and concentration using each method. Protein aggregates were generated by stirring an immunoglobulin solution. ![]() This study aimed to compare particle size distributions and concentrations of protein aggregates using the orthogonal methods. However, the different detection principles of the methods potentially lead to inconsistencies in results. We have found that quantitative laser diffraction (qLD) is also effective for quantitative evaluation of protein aggregates over a wide size range. Recently, novel methods with enhanced reliability and sensitivity, such as nanoparticle tracking analysis (NTA), resonant mass measurement (RMM), and flow imaging (FI), have emerged. In the past, analysis of micron-sized (>1.0 μm) aggregates of therapeutic proteins has been limited to light obscuration (LO), and appropriate quantitative methods of evaluating protein aggregates need to be developed.
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