Noninvasive morpho-molecular imaging reveals early therapy-induced senescence in human cancer cells

Anticancer therapy screening in vitro identifies additional treatments and improves clinical outcomes. Systematically, although most tested cells respond to cues with apoptosis, an appreciable portion enters a senescent state, a critical condition potentially driving tumor resistance and relapse. Conventional screening protocols would strongly benefit from prompt identification and monitoring of therapy-induced senescent (TIS) cells in their native form. We combined complementary all-optical, label-free, and quantitative microscopy techniques, based on coherent Raman scattering, multiphoton absorption, and interferometry, to explore the early onset and progression of this phenotype, which has been understudied in unperturbed conditions. We identified TIS manifestations as early as 24 hours following treatment, consisting of substantial mitochondrial rearrangement and increase of volume and dry mass, followed by accumulation of lipid vesicles starting at 72 hours. This work holds the potential to affect anticancer treatment research, by offering a label-free, rapid, and accurate method to identify initial TIS in tumor cells

Optimization of gas-filled quartz capillary discharge waveguide for high-energy laser wakefield acceleration

A hydrogen-filled capillary discharge waveguide made of quartz is presented for high-energy laser wakefield acceleration (LWFA). The experimental parameters (discharge current and gas pressure) were optimized to mitigate ablation by a quantitative analysis of the ablation plasma density inside the hydrogen-filled quartz capillary. The ablation plasma density was obtained by combining a spectroscopic measurement method with a calibrated gas transducer. In order to obtain a controllable plasma density and mitigate the ablation as much as possible, the range of suitable parameters was investigated. The experimental results demonstrated that the ablation in the quartz capillary could be mitigated by increasing the gas pressure to similar to 7.5-14.7 Torr and decreasing the discharge current to similar to 70-100 A. These optimized parameters are promising for future high-energy LWFA experiments based on the quartz capillary discharge waveguide

Ultralow-emittance measurement of high-quality electron beams from a laser wakefield accelerator

By designing a cascaded laser wakefield accelerator, high-quality monoenergetic electron beams (e beams) with peak energies of 340–360MeV and rms divergence of <0.3 mrad were produced. Based on this accelerator, the e-beam betatron radiation spectra were measured exactly via the single-photon counting technique to diagnose the e-beam transverse emittance in a single shot. The e-beam transverse size in the wakefield was estimated to be ~0.35 lm by comparing the measured X-ray spectra with the analytical model of synchrotron-like radiation. By combining the measured e-beam energy and divergence, the normalized transverse emittance was estimated to be as low as 56 um mrad and consistent with particle-in-cell simulations. These high-energy ultralow-emittance e beams hold great potential applications in developing free electron lasers and high-energy X-ray and gamma ray sources

Enhanced betatron radiation by steering a laser-driven plasma wakefield with a tilted shock front

We have experimentally realized a scheme to enhance betatron radiation by manipulating transverse oscillation of electrons in a laser-driven plasma wakefield with a tilted shock front (TSF). Very brilliant betatron x-rays have been produced with significant enhancement both in photon yield and peak energy but almost maintain the e-beam energy spread and charge. Particle-in-cell simulations indicate that the accelerated electron beam (e beam) can acquire a very large transverse oscillation amplitude with an increase in more than 10-fold, after being steered into the deflected wakefield due to the refraction of the driving laser at the TSF. Spectral broadening of betatron radiation can be suppressed owing to the small variation in the peak energy of the low-energy-spread e beam in a plasma wiggler regime. It is demonstrated that the e-beam generation, refracting, and wiggling can act as a whole to realize the concurrence of monoenergetic e beams and bright x-rays in a compact laser-wakefield accelerator

Hybrid capillary discharge waveguide for laser wakefield acceleration

A hybrid capillary discharge waveguide formed by injecting low-pressure hydrogen (< 3.8 Torr) into a pure ablative capillary is presented to supply the stable guiding for multi-GeV laser wakefield acceleration. The injected low-pressure gas only provides the seed plasma for ablative discharge breakdown, like the adsorbed gas in the inner wall of the ablative capillary. With this hybrid capillary, a stable discharge with low jitter (~ 5 ns) can be achieved in a simple way, and the plasma density inside can also be controlled in a range of ~0.7 x 1018cm-3-1.2 x 1018cm-3 within a 150-ns plasma channel temporal window. Furthermore, the hybrid capillary can also be easily extended to a longer length by adding multiple segments, and femtosecond laser pulses can be well guided both in the single and multiple segments mode. With these advantages, the hybrid capillary may provide an attractive plasma channel for multi-GeV-scale laser wakefield acceleration

DNA DIRECTED SELF-ASSEMBLED NANOSTRUCTURES FOR SURFACE ENHANCED RAMAN SCATTERING

This thesis entitled “DNA directed self-assembled nanostructures for surface enhanced Raman scattering” focuses on the fabrication of plasmonic nanostructures and their applications in surface enhanced Raman scattering (SERS). Surface enhance Raman spectroscopy techniques enable the investigation of a particular analyte within complex mixtures with high sensitivity, which further helps the understanding of the normally hidden heterogeneities of complex biological and chemical systems. Plasmonic nanostructures concentrate light into small volumes, which greatly enhance the local electromagnetic (EM) field near the metal nanostructures, leading to a strong enhancement of usually weak Raman signals. For the fabrication of highly efficient plasmonic nanostructures, the two nanoparticles have to be placed close to each other with an interparticle gap of few nanometers in high precision. A novel fabrication method of nanostructures composed of gold nanoparticles (Au NPs) with tunable and precise interparticle gap has been described. By transferring a certain number of clusters of single-stranded DNA (ssDNA) to the surface of nanoparticles, nanostructures can be self-assembled from nanoparticles with the direct of DNA hybridization. When AuNP dimer is evenly coated with compounds, the strong local EM field at the interparticle gap can induce the enhanced Raman signal of the compound according to the mechanism of SERS. By coating AuNP dimer with 4-mercaptobenzonitrile (4-MCN), a compound exhibiting strong Raman peak in the cellular Raman silent region, the position of AuNP dimer inside the cell after AuNP dimer being internalized can be tracked by doing Raman mapping measurements. Tracking the position of nanoparticles inside cells is crucial for us to know whether therapeutic agents are precisely delivered to specific targeted sites

DNA DIRECTED SELF-ASSEMBLED NANOSTRUCTURES FOR SURFACE ENHANCED RAMAN SCATTERING

This thesis entitled “DNA directed self-assembled nanostructures for surface enhanced Raman scattering” focuses on the fabrication of plasmonic nanostructures and their applications in surface enhanced Raman scattering (SERS). Surface enhance Raman spectroscopy techniques enable the investigation of a particular analyte within complex mixtures with high sensitivity, which further helps the understanding of the normally hidden heterogeneities of complex biological and chemical systems. Plasmonic nanostructures concentrate light into small volumes, which greatly enhance the local electromagnetic (EM) field near the metal nanostructures, leading to a strong enhancement of usually weak Raman signals. For the fabrication of highly efficient plasmonic nanostructures, the two nanoparticles have to be placed close to each other with an interparticle gap of few nanometers in high precision. A novel fabrication method of nanostructures composed of gold nanoparticles (Au NPs) with tunable and precise interparticle gap has been described. By transferring a certain number of clusters of single-stranded DNA (ssDNA) to the surface of nanoparticles, nanostructures can be self-assembled from nanoparticles with the direct of DNA hybridization. When AuNP dimer is evenly coated with compounds, the strong local EM field at the interparticle gap can induce the enhanced Raman signal of the compound according to the mechanism of SERS. By coating AuNP dimer with 4-mercaptobenzonitrile (4-MCN), a compound exhibiting strong Raman peak in the cellular Raman silent region, the position of AuNP dimer inside the cell after AuNP dimer being internalized can be tracked by doing Raman mapping measurements. Tracking the position of nanoparticles inside cells is crucial for us to know whether therapeutic agents are precisely delivered to specific targeted sites

An Adaptive ORB-SLAM3 System for Outdoor Dynamic Environments

Recent developments in robotics have heightened the need for visual SLAM. Dynamic objects are a major problem in visual SLAM which reduces the accuracy of localization due to the wrong epipolar geometry. This study set out to find a new method to address the low accuracy of visual SLAM in outdoor dynamic environments. We propose an adaptive feature point selection system for outdoor dynamic environments. Initially, we utilize YOLOv5s with the attention mechanism to obtain a priori dynamic objects in the scene. Then, feature points are selected using an adaptive feature point selector based on the number of a priori dynamic objects and the percentage of a priori dynamic objects occupied in the frame. Finally, dynamic regions are determined using a geometric method based on Lucas-Kanade optical flow and the RANSAC algorithm. We evaluate the accuracy of our system using the KITTI dataset, comparing it to various dynamic feature point selection strategies and DynaSLAM. Experiments show that our proposed system demonstrates a reduction in both absolute trajectory error and relative trajectory error, with a maximum reduction of 39% and 30%, respectively, compared to other systems

Self-Assembled Bimetallic Au–Ag Nanorod Vertical Array for Single-Molecule Plasmonic Sensing

Ordered plasmonic nanoparticle arrays are highly desirable for optical sensing as they provide uniformly distributed plasmonic hotspots due to their periodic order and near-field coupling. Anisotropic-shaped bimetallic nanoparticles are of particular interest, as their hybridized plasmonic modes enable precise tuning of plasmonic resonance and optical responses. However, the controlled assembly of large-scale arrays of bimetallic nanoparticles with uniformly distributed hotspots remains a challenge. In this study, we present a highly robust and reproducible method for creating large-area vertically aligned arrays of bimetallic Au–Ag nanorods by epitaxially growing Ag over preassembled Au nanorods. Structural characterization using electron microscopy and X-ray photoelectron spectroscopy confirms the formation of a uniform thin layer of Ag, creating a bimetallic Au–Ag nanorod array. We also demonstrate the efficacy of the designed nanoarrays for surface-enhanced Raman scattering (SERS) spectroscopy. Our experimental and computational studies show considerably enhanced optical responses of bimetallic Au–Ag nanorods compared to their monometallic counterparts. The scalability, cost-effectiveness, and reproducibility of this method make it a versatile platform for creating various structures by varying guest nanoparticles in suspensions with broad applications in biomedical research, food safety surveillance, and environmental monitoring