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Nanostars on Nanopipettes: A Raman Probe for Quantifying Oxygen Levels in Hypoxia in Single Cells and Tumors
摘要： Multiple sharp-edged gold nanostars were efficiently assembled on nanopipette tips by 3-aminopropyltrimethoxysilane (APTES) via an electrostatic interaction for a potent intracellular hypoxia-sensing Raman probe. Colloidal stability and surface immobilization was checked using scanning electron microscopy, light scattering and zeta potential measurements. Site-specific intracellular hypoxia levels can be estimated in vitro and in vivo using Raman lancets (RL). Distinct Raman spectral changes for the nitro-(NO2) functional group of the redox maker 4-nitrothiophenol (4NTP) can be quantified according to the intracellular oxygen (O2) contents, ranging from 1% to 10%. Facile removal of RL from cells can be achieved after a short measurement time. Redox potential changes in mitochondrial respiration could also be examined using serial injection of inhibitors. Three-dimensional (3D)-cultured cells and in vivo tests were used to validate our methods of measuring tumour hypoxia; potential applications were validated in terms of judging the aggressiveness of cancer cells by differentiating spectral changes between malignant and benign cells.
关键词： Cancer aggressiveness,Hypoxia,Surface enhanced resonance Raman,Intracellular redox potential,Nanopipette lancets
更新于2025-09-23 15:23:52
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Variable-Temperature Resonance Raman Studies to Probe Interchain Ordering for Semiconducting Conjugated Polymers with Different Chain Curvature
摘要： The morphology and crystallinity of the polymers used to fabricate bulk heterojuction (BHJ) solar cells significantly influences the efficiency of the cells. We have used variable-temperature (VT) spectroscopy techniques, namely VT emission and VT resonance Raman spectroscopy (VT-RRS), to examine how the backbone linearity of a conducting polymer affects its electronic response to temperature and variations in solution behavior. We have studied two types of donor–acceptor polymers used in BHJ cells with differing backbone structures; they are poly-{5,6-bis(tetradecyloxy)-4-(thiophen-2-yl)benzo[c]-1,2,5-thiadiazole} (PTBT) which has a curved and poly-{5,6-bis(tetradecyloxy)-4-(thieno[3,2-b]-thiophen-2-yl)benzo[c]-1,2,5-thiadiazole} (PTTBT) which has a linear chain structure. Time-dependent density functional theory (TD-DFT) calculations and resonance Raman spectra (RRS) of PTTBT revealed the presence of three electronic transitions, with character that varies between p to p*, mixed p to p*/charge transfer and pure charge transfer in nature. Emission spectra of PTTBT showed spectral changes at 650 and 710 nm with varied temperature ((cid:2)10 to 60 8C). Variable-temperature RRS was measured in resonance with the lowest and highest energy electronic transitions. The changes were interpreted using two-dimensional correlation spectroscopy (2DCOS) analysis. PTTBT showed gradual shifts to lower wavenumbers of modes at around 1425, 1450 and 1500 cm(cid:2)1. For PTBT larger and more rapid spectral changes are observed at 1440 and 1460 cm(cid:2)1 consistent with greater variation in the electronic nature upon heating. Further study into the influence of polymer linearity on crystallinity and long range order was carried out using low-frequency Raman (LFR) to examine drop cast films under a variety of different conditions. LFR spectra showed that PTTBT has a band at 73 cm(cid:2)1. This is observed under a variety of film-forming conditions. PTBT does not show distinct low frequency modes, consistent with its low crystallinity.
关键词： resonance Raman spectroscopy,low-frequency Raman,long range order,variable temperature,conducting polymers
更新于2025-09-23 15:23:52
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Electrochemical surface plasmon resonance (EC-SPR) aptasensor for ampicillin detection
摘要： Surface plasmon resonance technique is highly sensitive to various processes taking place on a metal film and it has emerged as a powerful label-free method to study molecular binding processes taking place on a surface. Another important but less explored area of applications is the use of hybrid methods which combine electrochemistry with optical methods for better monitoring and understanding of biochemical processes. A detection method based on surface plasmon resonance was developed for ampicillin, applying electrochemical techniques for the elaboration and characterization of the aptasensing platform used in this study. Ampicillin is a broad-spectrum β-lactam antibiotic, used both in human and veterinary medicine for the treatment and prevention of primary respiratory, gastrointestinal, urogenital, and skin bacterial infections. It is widely used because of its broad spectrum and low cost. This widespread use can result in the presence of residues in the environment and in food leading to health problems for individuals who are hypersensitive to penicillins. The gold chip was functionalized through potential-assisted immobilization, using multipulse amperometry, first with a thiol-terminated aptamer, as a specific ligand and secondly, using the same procedure, with mercaptohexanol, used to cover the unoccupied binding sites on the gold surface in order to prevent the nonspecific adsorption of ampicillin molecules. After establishing the optimal conditions for the chip functionalization, different concentrations of ampicillin were detected in real time, in the range of 2.5–1000 μmol L?1, with a limit of detection of 1 μmol L?1, monitoring the surface plasmon resonance response. The selectivity of the aptasensor was proven in the presence of other antibiotics and drugs, and the method was successfully applied for the detection of ampicillin from river water.
关键词： Multipulse amperometry,Electrochemical surface plasmon resonance (EC-SPR),Ampicillin,QCM,Antibiotic detection,SPR aptasensor
更新于2025-09-23 15:23:52
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Radiomic analysis of imaging heterogeneity in tumours and the surrounding parenchyma based on unsupervised decomposition of DCE-MRI for predicting molecular subtypes of breast cancer
摘要： Objectives This study aimed to predict the molecular subtypes of breast cancer via intratumoural and peritumoural radiomic analysis with subregion identification based on the decomposition of contrast-enhanced magnetic resonance imaging (DCE-MRI). Methods The study included 211 women with histopathologically confirmed breast cancer. We utilised a completely unsupervised convex analysis of mixtures (CAM) method by unmixing dynamic imaging series from heterogeneous tissues. Each tumour and the surrounding parenchyma were thus decomposed into multiple subregions, representing different vascular characterisations, from which radiomic features were extracted. A random forest model was trained and tested using a leave-one-out cross-validation (LOOCV) method to predict breast cancer subtypes. The predictive models from tumoural and peritumoural subregions were fused for classification. Results Tumour and peritumour DCE-MR images were decomposed into three compartments, representing plasma input, fast-flow kinetics, and slow-flow kinetics. The tumour subregion related to fast-flow kinetics showed the best performance among the subregions for differentiating between patients with four molecular subtypes (area under the receiver operating characteristic curve (AUC) = 0.832), exhibiting an AUC value significantly (p < 0.0001) higher than that obtained with the entire tumour (AUC = 0.719). When the tumour- and parenchyma-based predictive models were fused, the performance, measured as the AUC, increased to 0.897; this value was significantly higher than that obtained with other tumour partition methods. Conclusions Radiomic analysis of intratumoural and peritumoural heterogeneity based on the decomposition of image time-series signals has the potential to more accurately identify tumour kinetic features and serve as a valuable clinical marker to enhance the prediction of breast cancer subtypes.
关键词： Magnetic resonance imaging,Diagnostic imaging,Breast neoplasms
更新于2025-09-23 15:23:52
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NIR-Fluorescent Multidye Silica Nanoparticles with Large Stokes Shifts for Versatile Biosensing Applications
摘要： We have synthesized and characterized of a series of single and multidye copolymerized nanoparticles with large to very large Stokes shifts (100 to 255 nm) for versatile applications as standalone or multiplexed probes in biological matrices. Nanoparticles were prepared via the St?ber method and covalently copolymerized with various combinations of three dyes, including one novel aminocyanine dye. Covalently encapsulated dyes exhibited no significant leakage from the nanoparticle matrix after more than 200 days of storage in ethanol. Across multiple batches of nanoparticles with varying dye content, the average yields and average radii were found to be highly reproducible. Furthermore, the batch to batch variability in the relative amounts of dye incorporated was small (relative standard deviations <2.3%). Quantum yields of dye copolymerized nanoparticles were increased 50% to 1000% relative to those of their respective dye-silane conjugates, and fluorescence intensities were enhanced by approximately three orders of magnitude. Prepared nanoparticles were surface modified with polyethylene glycol and biotin and bound to streptavidin microspheres as a proof of concept. Under single wavelength excitation, microsphere-bound nanoparticles displayed readily distinguishable fluorescence signals at three different emission wavelengths, indicating their potential applications to multicolor sensing. Furthermore, nanoparticles modified with polyethylene glycol and biotin demonstrated hematoprotective qualities and reduced nonspecific binding of serum proteins, indicating their potential suitability to in vivo imaging applications.
关键词： Fluorescent silica nanoparticles,Biocompatible nanoparticles,Large stokes shift,Near-infrared fluorescence,Multicolor assay,Resonance energy transfer
更新于2025-09-23 15:23:52
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Unidirectional light scattering by up–down Janus dimers composed of gold nanospheres and silicon nanorods
摘要： In this paper, a time-domain finite-difference (FDTD) method is used to simulate the scattering properties of a Janus dimer that a gold nanosphere is putted on the top of a silicon nanorod. We have demonstrated that the Janus dimer exhibits unidirectional scattering in the whole wavelength region of the sunlight. The unidirectionality of the dimer will improve with the height increase of the silicon nanorod and the gap decrease between two adjacent dimers. In our simulation, the forward-to-backward ratio (F/B) of the Janus dimer calculated dividing forward scattering spectra by backward scattering spectra can achieve the maximum of 20 when the height of silicon nanorod is 300 nm. What is more, we have applied the Janus dimers to amorphous silicon thin-film solar cells as antireflection structures. The reflectivity of the solar cells reduces by 39.40% and the short circuit current density improves by 5.04% than those of the reference. Therefore, the Janus dimers has a great application prospect in photovoltaic devices.
关键词： Amorphous silicon solar cells,Janus dimers,Unidirectional scattering,Electric and magnetic dipole resonance
更新于2025-09-23 15:23:52
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Bound states in the continuum in the double-period rectangular hole arrays perforated in one layer of photonic crystal slab in the visible wavelength region
摘要： We investigate optical bound states in the continuum (BICs) supported by a photonic crystal (PhC) slab penetrated with two periodic rectangular hole arrays embedded each other parallelly and vertically. It proves that the tunable off-Γ BICs can be found in the structure of both types, but the at-Γ BICs can only be obtained in the parallel structure. Quality factors (Q-factor) are obtained extremely high exceeding 105 for both types of structures. The tunable off-Γ BICs can be modulated by the structure parameters. Especially, the sensitivity of the resonant wavelength on the surrounding medium refractive index change is very large for the structure in both types, and tunable off-Γ BICs can be tuned by varying the environmental index. The results above accord well from the finite difference time domain method (FDTD) and the temporal coupled mode theory (CMT), which are beneficial to design practical resonance elements based on optical BICs in various new optical applications.
关键词： Double-periodic rectangular hole arrays,Photonic crystal,Fano resonance,Bound state in the continuum
更新于2025-09-23 15:23:52
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Electron energy-loss spectroscopy (EELS) with a cold-field emission scanning electron microscope at low accelerating voltage in transmission mode
摘要： A commercial electron energy-loss spectrometer (EELS) attached to a high-resolution cold-field emission scanning electron microscope in transmission mode (STEM) is evaluated and its potential for characterizing materials science thin specimens at low accelerating voltage is reviewed. Despite the increased beam radiation damage at SEM voltages on sensitive compounds, we describe some potential applications which benefit from lowering the primary electrons voltage on less-sensitive specimens. We report bandgap measurements on several dielectrics which were facilitated by the lack of Cherenkov radiation losses at 30 kV. The possibility of volume plasmon imaging to probe local composition changes in complex materials was demonstrated using energy-filtered STEM, either via spectrum imaging or elemental mapping using the 'three-windows' method. As plasmonic materials are increasing used for energy, electronics or biomedical applications, the ability of reliably evaluate their properties at low accelerating voltage in a SEM is very appealing and is demonstrated. The energy resolution of the spectrometer, taken as the full width at half maximum of the zero-loss peak, was routinely measured at around 0.55 eV and it is demonstrated that t/λ ratios up to 1.5 allowed practical EEL spectroscopy at 30 kV.
关键词： Damage,Plasmon resonance,Silver,STEM,Lithium,Zero-loss,Bandgap
更新于2025-09-23 15:23:52
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Development of an Aptamer-Conjugated Polyrotaxane-Based Biodegradable Magnetic Resonance Contrast Agent for Tumor-Targeted Imaging
摘要： Gadolinium-based magnetic resonance imaging (MRI) contrast agents with biodegradability, biosafety, and high efficiency are highly desirable for tumor diagnosis. Herein, a biodegradable, AS1411-conjugated, α-cyclodextrin polyrotaxane-based MRI contrast agent (AS1411-G2(DTPA-Gd)-SS-PR) was developed for targeted imaging of cancer. The polyrotaxane-based contrast agent was achieved by the complexation of α-cyclodextrin (α-CD) and a linear poly(ethylene glycol) (PEG) chain containing disulfide linkages at two terminals. The disulfides enable the de-threading of the polyrotaxane into excretable small units due to cleavage of the disulfide linkages by reducing agents such as intracellular glutathione (GSH). Furthermore, the second-generation lysine dendron conjugated with gadolinium chelates and AS1411, a G-quadruplex oligonucleotide that has high binding affinity to nucleolin generally presenting a high level on the surface of tumor cells, coupled to the α-CD via click chemistry. The longitudinal relaxivity of AS1411-G2(DTPA-Gd)-SS-PR (11.7 mM?1 s?1) was two times higher than the clinically used Gd-DTPA (4.16 mM?1 s?1) at 0.5 T. The in vitro degradability was confirmed by incubating with 10 mM 1,4-Dithiothreitol (DTT). Additionally, the cytotoxicity, histological assessment and gadolinium retention studies showed that the prepared polyrotaxane-based contrast agent had a superior biocompatibility and was predominantly cleared renally without long-term accumulation toxicity. Importantly, AS1411-G2(DTPA-Gd)-SS-PR displayed the enhanced performance in MRI of breast cancer cells in vitro as well as a subcutaneous breast tumor in vivo due to the targeting ability of AS1411 aptamer. The enhanced performance was due to efficient multivalent interactions with tumor cells, producing faster accumulation and longer contrast imaging time at the tumor site. This work clearly confirms that the specially designed and fabricated α-CD-based polyrotaxane is a promising contrast agent with excellent contrast imaging performance and biosafety for tumor MR imaging.
关键词： AS1411 aptamer,biodegradability,polyrotaxanes,magnetic resonance imaging,breast cancer targeting
更新于2025-09-23 15:23:52
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Evaluating Mechanical Properties of Polymers at the Nanoscale Level via Atomic Force Microscopy–Infrared Spectroscopy
摘要： Characterization and optimization of packaging materials requires accessing their composition with nanometric precision. A possible solution comes from AFM-IR, a technique based on the coupling of Atomic Force Microscope and InfraRed spectroscopy, capable to acquire IR spectra with a spatial resolution overpassing by far the limit of infrared spectroscopy. Differentiating polyolefins – typical component of packaging films – is complicated by the large similarity in the infrared response of this class of materials. Here, we propose a method to improve domains differentiation based on the analysis of IR spectra and viscoelastic properties, extracted via a routine similar to that employed in contact-resonance AFM.
关键词： Subdiffraction Resolution,Photothermal Induced Resonance.,AFM-IR,Polymers
更新于2025-09-23 15:23:52