Surface-based Techniques Research Articles

"Binding" or "Binding and Switching"? A Perspective on Resolving Conformational Changes of Surface-Attached Biomolecular Receptors.

Understanding the structural reconfiguration of a biomolecular receptor remains a topic of particular interest to the biosensing community. This is because conformationally changing receptors are commonly employed in biosensors to harness their capability to bind specifically to their target. Often, such receptors are attached to surfaces so that binding can be transduced into a measurable response. Doing so, however, can impose constraints on the possible configurations they can adopt. Such constraints can ultimately influence, for example, their receptor-target binding models or their affinity, which is essential to provide the desired analytical performances in biosensors. Motivated by the idea of gaining further insights into the impact of surface attachment on conformationally switching receptors attached to surfaces, we explore here the various surface-based techniques capable of monitoring structural changes. We decided to narrow our survey to techniques that have been applied to the investigation of nucleic acids to provide an overview of their key features. We envision that this will bring a broader perspective of the field and the challenges ahead with the hopes of "finding the switch" in surface-attached biomolecular receptors.

Augmented Reality Implementation in Minimally Invasive Surgery for Future Application in Pulmonary Surgery: A Systematic Review.

This systematic review investigates of Augmented Reality (AR) systems used in minimally invasive surgery of deformable organs, focusing on initial registration, dynamic tracking, and visualization. The objective is to acquire a comprehensive understanding of the current knowledge, applications, and challenges associated with current AR-techniques, aiming to leverage these insights for developing a dedicated AR pulmonary Video or Robotic Assisted Thoracic Surgery (VATS/RATS) workflow. A systematic search was conducted within Embase, Medline (Ovid) and Web of Science on April 16, 2024, following the Preferred Reporting items for Systematic Reviews and Meta-Analyses (PRISMA). The search focused on intraoperative AR applications and intraoperative navigational purposes for deformable organs. Quality assessment was performed and studies were categorized according to initial registration and dynamic tracking methods. 33 articles were included, of which one involved pulmonary surgery. Studies used both manual and (semi-) automatic registration methods, established through anatomical landmark-based, fiducial-based, or surface-based techniques. Diverse outcome measures were considered, including surgical outcomes and registration accuracy. The majority of studies that reached an registration accuracy below 5mm applied surface-based registration. AR can potentially aid surgeons with real-time navigation and decision making during anatomically complex minimally invasive procedures. Future research for pulmonary applications should focus on exploring surface-based registration methods, considering their non-invasive, marker-less nature, and promising accuracy. Additionally, vascular-labeling-based methods are worth exploring, given the importance and relative stability of broncho-vascular anatomy in pulmonary VATS/RATS. Assessing clinical feasibility of these approaches is crucial, particularly concerning registration accuracy and potential impact on surgical outcomes.

Strength mechanisms and tunability in Al-Ce-Mg ternary alloys enabled by additive manufacturing

Al-Ce-based alloys are promising candidates for additive manufacturing (AM) due to their hot-cracking resistance and because they do not require heat treatment to obtain precipitation strengthening. Rapid solidification rates enabled by AM methods can lead to enhanced mechanical properties; however, the strengthening mechanisms over large composition ranges were unclear. Here, combinatorial synthesis by directed-energy deposition (DED) and hardness measurements were used to rapidly map the composition-dependent strength of the ternary Al-Ce-Mg system. Tensile testing and microstructure characterization of selected compositions were performed to elucidate the compositional dependence of the strengthening mechanisms. Al11Ce3 precipitates were present in all cases, and the maximum hardness (1.25 GPa) was measured for the Al-8Ce-10Mg composition. A combination of (i) Hall-Petch strengthening, based on the FCC-matrix-phase cell size; (ii) particle strengthening, based on Al11Ce3 volume fraction and size; and (iii) solid-solution strengthening, based on Mg composition of the matrix phase, were used to account for the measured strengths. Vickers hardness is shown to correlate well with ultimate tensile strength in these alloys, highlighting the value of surface-based techniques for rapid screening.

Surface-Based Techniques for IoT Networks: Opportunities and Challenges

This work provides an overview of recent techniques in the area of surface-based communications, describing their potential and advantages for IoT networks. Specifically, it is discussed how the use of reconfigurable intelligent surfaces could bring significant advantages in terms of energy consumption, self-sustainment, programmability, and self-organization of IoT networks, possibly enabling the use of mmWaves for IoT, and the improvement of back-scattering techniques. The newest paradigms in the area of surface-based communications are described, including nearly-passive surfaces, active surfaces, and plug-and-play surfaces, explaining how these advanced frameworks fit into the IoT context. Numerical examples are shown to substantiate the gains that surface-based communications can provide for IoT. Finally, open research directions are identified together with the main research challenges towards the implementation of energy-neutral, self-organizing surface-based IoT environments.

Highly Sensitive, Robust, and Recyclable TiO2/AgNP Substrate for SERS Detection.

Label-free biosensors provide an important platform for detecting chemical and biological substances without needing extra labeling agents. Unlike surface-based techniques such as surface plasmon resonance (SPR), interference, and ellipsometry, surface-enhanced Raman spectroscopy (SERS) possesses the advantage of monitoring analytes both on surfaces and in solutions. Increasing the SERS enhancement is crucial to preparing high-quality substrates without quickly losing their stability, sensitivity, and repeatability. However, fabrication methods based on wet chemistry, nanoimprint lithography, spark discharge, and laser ablation have drawbacks of waste of time, complicated processes, or nonreproducibility in surface topography. This study reports the preparation of recyclable TiO2/Ag nanoparticle (AgNP) substrates by using simple arc ion plating and direct-current (dc) magnetron sputtering technologies. The deposited anatase-phased TiO2 ensured the photocatalytic degradation of analytes. By measuring the Raman spectra of rhodamine 6G (R6G) in titrated concentrations, a limit of detection (LOD) of 10−8 M and a SERS enhancement factor (EF) of 1.01 × 109 were attained. Self-cleaning was performed via UV irradiation, and recyclability was achieved after at least five cycles of detection and degradation. The proposed TiO2/AgNP substrates have the potential to serve as eco-friendly SERS enhancers for label-free detection of various chemical and biological substances.

Early alterations of cortical thickness and gyrification in migraine without aura: a retrospective MRI study in pediatric patients

BackgroundMigraine is the most common neurological disease, with high social-economical burden. Although there is growing evidence of brain structural and functional abnormalities in patients with migraine, few studies have been conducted on children and no studies investigating cortical gyrification have been conducted on pediatric patients affected by migraine without aura.MethodsSeventy-two pediatric patients affected by migraine without aura and eighty-two controls aged between 6 and 18 were retrospectively recruited with the following inclusion criteria: MRI exam showing no morphological or signal abnormalities, no systemic comorbidities, no abnormal neurological examination. Cortical thickness (CT) and local gyrification index (LGI) were obtained through a dedicated algorithm, consisting of a combination of voxel-based and surface-based morphometric techniques. The statistical analysis was performed separately on CT and LGI between: patients and controls; subgroups of controls and subgroups of patients.ResultsPatients showed a decreased LGI in the left superior parietal lobule and in the supramarginal gyrus, compared to controls. Female patients presented a decreased LGI in the right superior, middle and transverse temporal gyri, right postcentral gyrus and supramarginal gyrus compared to male patients. Compared to migraine patients younger than 12 years, the ≥ 12-year-old subjects showed a decreased CT in the superior and middle frontal gyri, pre- and post-central cortex, paracentral lobule, superior and transverse temporal gyri, supramarginal gyrus and posterior insula. Migraine patients experiencing nausea and/or vomiting during headache attacks presented an increased CT in the pars opercularis of the left inferior frontal gyrus.ConclusionsDifferences in CT and LGI in patients affected by migraine without aura may suggest the presence of congenital and acquired abnormalities in migraine and that migraine might represent a vast spectrum of different entities. In particular, ≥ 12-year-old pediatric patients showed a decreased CT in areas related to the executive function and nociceptive networks compared to younger patients, while female patients compared to males showed a decreased CT of the auditory cortex compared to males. Therefore, early and tailored therapies are paramount to obtain migraine control, prevent cerebral reduction of cortical thickness and preserve executive function and nociception networks to ensure a high quality of life.

Time-Resolved and Label-Free Evanescent Light-Scattering Microscopy for Mass Quantification of Protein Binding to Single Lipid Vesicles.

In-depth understanding of the intricate interactions between biomolecules and nanoparticles is hampered by a lack of analytical methods providing quantitative information about binding kinetics. Herein, we demonstrate how label-free evanescent light-scattering microscopy can be used to temporally resolve specific protein binding to individual surface-bound (∼100 nm) lipid vesicles. A theoretical model is proposed that translates protein-induced changes in light-scattering intensity into bound mass. Since the analysis is centered on individual lipid vesicles, the signal from nonspecific protein binding to the surrounding surface is completely avoided, offering a key advantage over conventional surface-based techniques. Further, by averaging the intensities from less than 2000 lipid vesicles, the sensitivity is shown to increase by orders of magnitude. Taken together, these features provide a new avenue in studies of protein-nanoparticle interaction, in general, and specifically in the context of nanoparticles in medical diagnostics and drug delivery.

Standard operation procedure for switchSENSE DRX systems.

There is currently a large panel of technologies available to address molecular interactions in vitro. Each technology presents individual advantages and drawbacks, and it becomes challenging to choose which technology will be best suited for a molecular interaction of interest. Approaches can be broadly categorized as either microfluidic surface-bound methods (such as Surface Plasmon Resonance (SPR) or switchSENSE) or in-solution methods (such as Isothermal Titration Calorimetry (ITC) or MicroScale Thermophoresis (MST)). In-solution methods are advantageous in terms of sample preparation and ease of use as none of the binding partners are subjected to immobilization. On the other hand, surface-based techniques require only small amounts of immobilized interaction partner and provide off-rate characterization as unbound analytes can be removed from the surface to observe analyte dissociation. Here, a standard operating procedure (SOP) for the switchSENSE method is presented, which aims to guide new users through the process of a switchSENSE measurement, covering sample preparation, instrument and biochip handling as well as data acquisition and analysis. This guide will help researchers decide whether switchSENSE is the right method for their application as well as supporting novice users to get the most information out of a switchSENSE measurement. switchSENSE technology offers the unique advantage of a controlled DNA-based ligand surface within a microfluidic channel which allows the user to distribute specifically up to two different ligand molecules on the surface at a customized density and ratio. The technology offers multi-parameter characterization of binding kinetics, affinity, enzymatic activity, and changes in protein conformation.

Direct imaging, three-dimensional interaction spectroscopy, and friction anisotropy of atomic-scale ripples on MoS2

Theory predicts that two-dimensional (2D) materials may only exist in the presence of out-of-plane deformations on atomic length scales, frequently referred to as ripples. While such ripples can be detected via electron microscopy, their direct observation via surface-based techniques and characterization in terms of interaction forces and energies remain limited, preventing an unambiguous study of their effect on mechanical characteristics, including but not limited to friction anisotropy. Here, we employ high-resolution atomic force microscopy to demonstrate the presence of atomic-scale ripples on supported samples of few-layer molybdenum disulfide (MoS2). Three-dimensional force/energy spectroscopy is utilized to study the effect of ripples on the interaction landscape. Friction force microscopy reveals multiple symmetries for friction anisotropy, explained by studying rippled sample areas as a function of scan size. Our experiments contribute to the continuing development of a rigorous understanding of the nanoscale mechanics of 2D materials.

Imaging-assisted hydrogel formation for single cell isolation

We report a flexible single-cell isolation method by imaging-assisted hydrogel formation. Our approach consists of imaging-aided selective capture of cells of interest by encasing them into a polymeric hydrogel, followed by removal of unwanted cells and subsequent release of isolated cells by enzymatic hydrogel degradation, thus offering an opportunity for further analysis or cultivation of selected cells. We achieved high sorting efficiency and observed excellent viability rates (>98%) for NIH/3T3 fibroblasts and A549 carcinoma cells isolated using this procedure. The method presented here offers a mask-free, cost-efficient and easy-to-use alternative to many currently existing surface-based cell-sorting techniques, and has the potential to impact the field of cell culturing and isolation, e.g. single cell genomics and proteomics, investigation of cellular heterogeneity and isolation of best performing mutants for developing new cell lines.

Which is the best-suited landmark to assess the thoracic orientation?

Several skin surface-based techniques exist to non-invasively determine the spinal kinematics. However, the accuracy of these techniques is limited by soft-tissue artefacts. Furthermore, structures like the thorax are frequently assumed to be rigid but display considerable mobility within itself. This study aimed to quantify the accuracy at different thoracic landmarks for measuring mobility in healthy individuals during different activities to provide a recommendation for the best suited measurement location.The locations of 29 landmarks were continuously captured on 19 individuals (age: 25–59 years) during sitting, standing, walking, jumping, intra-thoracic motions, and different breathing depths using reflective markers. Marker triplets were used at every landmark to calculate their orientations by first backtracking the rigid-body motion (RBM) of the thorax in general, and subsequently calculating the RBM of each rigid marker triplet. Of the latter, the maximum axis angle for each exercise was statistically evaluated.Landmarks at the middle of the clavicles displayed the largest overall errors (approximately 90° during worst case scenario). However, the variability of errors among the investigated exercises was large. Landmarks at the cranial sternal region (particularly at the “Louis angle”) and at the T3 spinous process showed the smallest errors for all subjects and tasks (e.g., <5° and <11°, respectively, during normal breathing).When only one sensor is to be used, it is recommended to use the cranial sternal region to assess the thoracic orientation. Study results highly sensitive to thoracic orientation should be considered with care or performed using more appropriate methods.

Toblerone: Surface-Based Partial Volume Estimation.

Partial volume effects (PVE) present a source of confound for the analysis of functional imaging data. Correction for PVE requires estimates of the partial volumes (PVs) present in an image. These estimates are conventionally obtained via volumetric segmentation, but such an approach may not be accurate for complex structures such as the cortex. An alternative is to use surface-based segmentation, which is well-established within the literature. Toblerone is a new method for estimating PVs using such surfaces. It uses a purely geometric approach that considers the intersection between a surface and the voxels of an image. In contrast to existing surface-based techniques, Toblerone is not restricted to use with any particular structure or modality. Evaluation in a neuroimaging context has been performed on simulated surfaces, simulated T1-weighted MRI images and finally a Human Connectome Project test-retest dataset. A comparison has been made to two existing surface-based methods; in all analyses Toblerone's performance either matched or surpassed the comparator methods. Evaluation results also show that compared to an existing volumetric method (FSL FAST), a surface-based approach with Toblerone offers improved robustness to scanner noise and field non-uniformity, and better inter-session repeatability in brain volume. In contrast to volumetric methods, a surface-based approach negates the need to perform resampling which is advantageous at the resolutions typically used for neuroimaging.

Evolution Surfaces for Spatiotemporal Visualization of Vortex Features

Turbulent fluid flow data are often 4-D, spatially and temporally complex, and require specific techniques for visualization. Common visualization techniques neglect the temporal aspect of this data, limiting the ability to convey feature motion, or offering the user a complicated visualization. To remedy this, we present an approach-evolution surfaces-focused on the spatiotemporal rendering of user-selected flow features (i.e., vortices). By abstracting the spatial representation of these features, the approach renders their spatiotemporal behavior with reduced visual complexity. The behavior of vortex features is presented as surfaces, with textures indicating properties of motion and evolution events (e.g., bifurcation and amalgamation) represented by the surface topology. We evaluated the approach on two data sets generated from empirical measurement and computational simulation (Re = 28 000 and Re = 1200, respectively). Our approach's focus on handling evolution events makes it capable of visualizing higher Reynolds number (Re) flows than other surface-based techniques. This approach has been assessed by fluid dynamicists to assert the validity for flow analysis. Evolution surfaces offer a compact visualization of spatiotemporal vortex behaviors, opening potential avenues for exploration and analysis of fluid flows.

Transition Metal-Substituted Krebs-Type Polyoxometalate-Doped PEDOT Films.

The transition metal-substituted Krebs-type polyoxometalates (POMs) [Sb2W20M2O70(H2O)6]n-, M = Fe(III), Co(II), or Cu(II), were surface immobilized within the conducting polymer 3,4-ethylenedioxythiophene (PEDOT) on glassy carbon electrode surfaces. The immobilized films of different thicknesses were characterized by electrochemical and surface-based techniques. The inherent redox activity for the Krebs-type POMs, [Sb2W20M2O70(H2O)6]n-, M = Fe(III), Co(II), or Cu(II), that were observed in the solution phase were maintained in the polymeric PEDOT matrix. The resulting films were found to be extremely stable toward redox switching between the various POM-based redox states. The films exhibited pH-dependent redox activity and thin layer behavior up to 100 mV s-1. The films were found to be highly conductive through the employment of electrochemical impedance spectroscopy. Surface characterization of the films was carried out by X-ray photoelectron spectroscopy, atomic force microscopy, and scanning electron microscopy graph.

The Superficial White Matter in Autism and Its Role in Connectivity Anomalies and Symptom Severity.

In autism spectrum disorders (ASDs), the majority of neuroimaging studies have focused on the analysis of cortical morphology. White matter changes remain less understood, particularly their association to cortical structure and function. Here, we focused on region that has gained only little attention in ASD neuroimaging: the superficial white matter (SWM) immediately beneath the cortical interface, a compartment playing a prominent role in corticogenesis that incorporates long- and short-range fibers implicated in corticocortical connectivity. Studying a multicentric dataset of ASD and neurotypical controls, we harnessed surface-based techniques to aggregate microstructural SWM diffusion features. Multivariate analysis revealed SWM anomalies in ASD compared with controls in medial parietal and temporoparietal regions. Effects were similar in children and adolescents/adults and consistent across sites. Although SWM anomalies were more confined when correcting for cortical thickness and surface area, findings were overall robust. Diffusion anomalies modulated functional connectivity reductions in ASD and related to symptom severity. Furthermore, mediation models indicated a link between SWM changes, functional connectivity, and symptom load. Analyses targeting the SWM offer a novel perspective on the interplay between structural and functional network perturbations in ASD, highlighting a potentially important neurobiological substrate contributing to its diverse behavioral phenotype.

Neuroimaging in epilepsy.

Epilepsy neuroimaging is important for detecting the seizure onset zone, predicting and preventing deficits from surgery and illuminating mechanisms of epileptogenesis. An aspiration is to integrate imaging and genetic biomarkers to enable personalized epilepsy treatments. The ability to detect lesions, particularly focal cortical dysplasia and hippocampal sclerosis, is increased using ultra high-field imaging and postprocessing techniques such as automated volumetry, T2 relaxometry, voxel-based morphometry and surface-based techniques. Statistical analysis of PET and single photon emission computer tomography (STATISCOM) are superior to qualitative analysis alone in identifying focal abnormalities in MRI-negative patients. These methods have also been used to study mechanisms of epileptogenesis and pharmacoresistance.Recent language fMRI studies aim to localize, and also lateralize language functions. Memory fMRI has been recommended to lateralize mnemonic function and predict outcome after surgery in temporal lobe epilepsy. Combinations of structural, functional and post-processing methods have been used in multimodal and machine learning models to improve the identification of the seizure onset zone and increase understanding of mechanisms underlying structural and functional aberrations in epilepsy.

Cortical Thickness and Local Gyrification in Children with Developmental Dyslexia.

Developmental dyslexia is frequently associated with atypical brain structure and function within regions of the left hemisphere reading network. To date, few studies have employed surface-based techniques to evaluate cortical thickness and local gyrification in dyslexia. Of the existing cortical thickness studies in children, many are limited by small sample size, variability in dyslexia identification, and the recruitment of prereaders who may or may not develop reading impairment. Further, no known study has assessed local gyrification index (LGI) in dyslexia, which may serve as a sensitive indicator of atypical neurodevelopment. In this study, children with dyslexia (n = 31) and typically decoding peers (n = 45) underwent structural magnetic resonance imaging to assess whole-brain vertex-wise cortical thickness and LGI. Children with dyslexia demonstrated reduced cortical thickness compared with controls within previously identified reading areas including bilateral occipitotemporal and occipitoparietal regions. Compared with controls, children with dyslexia also showed increased gyrification in left occipitotemporal and right superior frontal cortices. The convergence of thinner and more gyrified cortex within the left occipitotemporal region among children with dyslexia may reflect its early temporal role in processing word forms, and highlights the importance of the ventral stream for successful word reading.

Towards in vivo focal cortical dysplasia phenotyping using quantitative MRI.

Focal cortical dysplasias (FCDs) are a range of malformations of cortical development each with specific histopathological features. Conventional radiological assessment of standard structural MRI is useful for the localization of lesions but is unable to accurately predict the histopathological features. Quantitative MRI offers the possibility to probe tissue biophysical properties in vivo and may bridge the gap between radiological assessment and ex-vivo histology. This review will cover histological, genetic and radiological features of FCD following the ILAE classification and will explain how quantitative voxel- and surface-based techniques can characterise these features. We will provide an overview of the quantitative MRI measures available, their link with biophysical properties and finally the potential application of quantitative MRI to the problem of FCD subtyping. Future research linking quantitative MRI to FCD histological properties should improve clinical protocols, allow better characterisation of lesions in vivo and tailored surgical planning to the individual.

Shear Wave Velocity Profiles of Roadway Substructures from Multichannel Analysis of Surface Waves and Waveform Tomography

Assessment of roadway subsidence caused by embedded low-velocity anomalies is critical to the health and safety of the traveling public. Surface-based seismic techniques are often used to assess roadways because of data acquisition convenience and large depths of characterization. To mitigate the negative impact of closing a traffic lane under traditional seismic testing, a new test system that uses a land streamer is presented. The main advantages of the system are the elimination of the need to couple the geophones to the roadway, the use of only one source at the end of the geophone array, and the movement of the whole test system along the roadway quickly. For demonstration, experimental data were collected on asphalt pavement overlying a backfilled sinkhole that was experiencing further subsidence. For the study, a 24-channel land streamer and a propelled energy generator to generate seismic energy were used. The test system was pulled by a pickup truck along the roadway and the data were collected with 81 shots at every 3 m for a road segment of 277.5 m, with a total data acquisition time of about 1 h. The measured seismic data set was analyzed by the standard multichannel analysis of surface waves (MASW) and advanced two-dimensional (2-D) waveform tomography methods. Eighty-one one-dimensional shear wave velocity (VS) profiles from the MASW were combined to obtain a single 2-D profile. The waveform tomography method was able to characterize subsurface structures at a high resolution (1.5- × 1.5-m cells) along the test length to a depth of 22.5 m. Very low S-wave velocity was obtained at the repaired sinkhole location. The 2-D VS profiles from the MASW and waveform tomography methods are consistent. Both methods were able to delineate high- and low-velocity soil layers and variable bedrock.

A computer and image-assisted guidance system for radial head arthroplasty

Accurately positioning components during radial head arthroplasty is difficult due to the complex shape of the radial head. The objective of this study was to develop a navigation system for patient-specific radial head implants using intra-operative surface-based registration techniques. Using an optical tracking system, an implant stem was navigated using real-time visualisation of the implant position and orientation (n = 8). Absolute positioning errors in the ML and AP directions were 0.8 ± 0.5 mm (and 1.1 ± 0.9°) and 0.8 ± 0.6 mm (and 1.2 ± 1.7°), respectively. Registration error was less than 1.0 mm. The current system is an important first step in the development of a computer-assisted system for implant navigation.