The Label-Free Detection and Identification of SARS-CoV-2 Using Surface-Enhanced Raman Spectroscopy and Principal Component Analysis.

The World Health Organization (WHO) declared in a May 2023 announcement that the COVID-19 illness is no longer categorized as a Public Health Emergency of International Concern (PHEIC); nevertheless, it is still considered an actual threat to world health, social welfare and economic stability. Consequently, the development of a convenient, reliable and affordable approach for detecting and identifying SARS-CoV-2 and its emerging new variants is crucial. The fingerprint and signal amplification characteristics of surface-enhanced Raman spectroscopy (SERS) could serve as an assay scheme for SARS-CoV-2. Here, we report a machine learning-based label-free SERS technique for the rapid and accurate detection and identification of SARS-CoV-2. The SERS spectra collected from samples of four types of coronaviruses on gold nanoparticles film, fabricated using a Langmuir-Blodgett self-assembly, can provide more spectroscopic signatures of the viruses and exhibit low limits of detection (<100 TCID50/mL or even <10 TCID50/mL). Furthermore, the key Raman bands of the SERS spectra were systematically captured by principal component analysis (PCA), which effectively distinguished SARS-CoV-2 and its variant from other coronaviruses. These results demonstrate that the combined use of SERS technology and PCA analysis has great potential for the rapid analysis and discrimination of multiple viruses and even newly emerging viruses without the need for a virus-specific probe.

Photomobile Polymer-Piezoelectric Composite for Enhanced Actuation and Energy Generation.

In this study, we present an innovative approach to increase the quantum yield and wavelength sensitivity of photomobile polymer (PMP) films based on azobenzene by doping the polymer matrix with noble metal nanoparticles. These doped PMP films showed faster and more significant bending under both UV as well as visible and near-infrared light regardless of whether it was coherent, incoherent, polarized, or unpolarized irradiation, expanding the potential of PMP-based actuators. To illustrate their practical implications, we created a proof-of-concept model of power generation by coupling it to flexible piezoelectric materials under simulated sunlight. This model has been tested under real operating conditions, thus demonstrating the possibility of generating electricity with variable light exposure. Additionally, our synthetic protocol is solvent-free, which is another benefit of environmental relevance. Our research lays the groundwork for the development of sunlight-sensitive devices, such as photomechanical actuators and advanced photovoltaic modules, which may break ground in the thriving field of smart materials. We are confident that the presented findings will contribute to the ongoing discourse in the field and inspire additional advances in renewable energy applications.

Development of LCEs with 100% Azobenzene Moieties: Thermo-Mechanical Phenomena and Behaviors.

Azobenzene is one of the most investigated photo-responsive liquid crystalline molecules. It can isomerize between two different isoforms, trans (E) and cis (Z) configurations, when stimulated by light. It is used as a molecular engine in photo-mobile materials (PMPs). The use of liquid crystals (LCs) as building blocks enhances the mechanical properties of the PMPs. It is not easy to obtain PMPs with monodomain configurations when the LCs are 100% azobenzene. In this work, we studied three LC mixtures, describing the thermo/mechanical phenomena that regulate the actuation of such materials. The nematic temperature of the LC elastomers was measured and the PMPs carefully characterized for their bending and speed capability. Our finding suggests that the ratio between linear and cross-linker monomer greatly influences the nematic temperature of the mixture. Furthermore, 100% azobenzene materials polymerized using dicumyl peroxide can be useful to design polarization-selective switches.

DNA Antiadhesive Layer for Reusable Plasmonic Sensors: Nanostructure Pitch Effect.

A long-term reusable sensor that provides the opportunity to easily regenerate the active surface and minimize the occurrence of undesired absorption events is an appealing solution that helps to cut down the costs and improve the device performances. Impressive advances have been made in the past years concerning the development of novel cutting-edge sensors, but the reusability can currently represent a challenge. Direct shielding of the sensor surface is not always applicable, because it can impact the device performance. This study reports an antiadhesive layer (AAL) made of 90 mg/mL DNA sodium salt from salmon testes (ssstDNA) for passivating gold plasmonic sensor surfaces. Our gold two-dimensional (2D) nanostructured plasmonic metasurfaces modified with AAL were used for DNA quantification. AAL is thin enough that the plasmonic sensor remains sensitive to subsequent deposition of DNA, which serves as an analyte. AAL protects the gold surface from unwanted nonspecific adsorption by enabling wash-off of the deposited analyte after analysis and thus recovery of the LSPR peak position (rLSPR). The calibration curve obtained on a single nanostructure (Achiral Octupolar, 100 nm pitch) gave an LOD = 105 ng/mL and an extraordinary dynamic range, performances comparable or superior to those of commercial UV-vis spectrometers for acid nucleic dosage. Two different analytes were tested: ssstDNA (∼2000 bp) in deionized water and double-strand DNA (dsDNA) of 546-1614 bp in 100 mM Tris buffer and 10 mM MgCl2. The two nanostructures (Achiral Octupolar 25 and 100) were found to have the same sensitivity to DNA in deionized water but different sensitivity to DNA in a salt/buffer solution, opening a potential for solute discrimination. To the best of our knowledge, this is the first report on the use of AAL made of several kilobase-pairs-long dsDNA to produce a reusable plasmonic sensor. The working principle and limitations are drawn based on the LSPR and SERS study.

Photo-Responsivity Improvement of Photo-Mobile Polymers Actuators Based on a Novel LCs/Azobenzene Copolymer and ZnO Nanoparticles Network.

The efficiency of photomobile polymers (PMP) in the conversion of light into mechanical work plays a fundamental role in achieving cutting-edge innovation in the development of novel applications ranging from energy harvesting to sensor approaches. Because of their photochromic properties, azobenzene monomers have been shown to be an efficient material for the preparation of PMPs with appropriate photoresponsivity. Upon integration of the azobenzene molecules as moieties into a polymer, they act as an engine, allowing fast movements of up to 50 Hz. In this work we show a promising approach for integrating ZnO nanoparticles into a liquid crystalline polymer network. The addition of such nanoparticles allows the trapping of incoming light, which acts as diffusive points in the polymer matrix. We characterized the achieved nanocomposite material in terms of thermomechanical and optical properties and finally demonstrated that the doped PMP was better performing that the undoped PMP film.

LSPR immuno-sensing based on iso-Y nanopillars for highly sensitive and specific imidacloprid detection.

Imidacloprid is the most widely used insecticide in agriculture and its intensive use over the last 30 years has caused a global concern due to its potentially toxic effects on the ecosystem. Considering the recent scientific interest in novel simple methods for imidacloprid analysis, we propose a label-free sensitive and specific localised surface plasmon resonance system for the detection of the insecticide based on 2D nanostructured metasurfaces with highly performing plasmonic properties. The specificity of the sensor proposed was achieved by covalent bio-functionalization of the metasurface using a smart and easy one-step procedure mediated by carbon disulphide. The biosensor produced was tested using a set of imidacloprid standard solutions showing a competitive limit of detection, lower than 1 ng mL-1. Our novel nanosensing configuration represents a valid and reliable solution to realize low-cost portable POC tests as an alternative to the laborious and expensive methods traditionally used for insecticide detection.

Plasmonic Metasurfaces Based on Pyramidal Nanoholes for High-Efficiency SERS Biosensing.

An inverted pyramidal metasurface was designed, fabricated, and studied at the nanoscale level for the development of a label-free pathogen detection on a chip platform that merges nanotechnology and surface-enhanced Raman scattering (SERS). Based on the integration and synergy of these ingredients, a virus immunoassay was proposed as a relevant proof of concept for very sensitive detection of hepatitis A virus, for the first time to our best knowledge, in a very small volume (2 µL), without complex signal amplification, allowing to detect a minimal virus concentration of 13 pg/mL. The proposed work aims to develop a high-flux and high-accuracy surface-enhanced Raman spectroscopy (SERS) nanobiosensor for the detection of pathogens to provide an effective method for early and easy water monitoring, which can be fast and convenient.

SERS Biosensor Based on Engineered 2D-Aperiodic Nanostructure for In-Situ Detection of Viable Brucella Bacterium in Complex Matrix.

Brucella is a foodborne pathogen globally affecting both the economy and healthcare. Surface Enhanced Raman Spectroscopy (SERS) nano-biosensing can be a promising strategy for its detection. We combined high-performance quasi-crystal patterned nanocavities for Raman enhancement with the use of covalently immobilized Tbilisi bacteriophages as high-performing bio-receptors. We coupled our efficient SERS nano-biosensor to a Raman system to develop an on-field phage-based bio-sensing platform capable of monitoring the target bacteria. The developed biosensor allowed us to identify Brucella abortus in milk by our portable SERS device. Upon bacterial capture from samples (104 cells), a signal related to the pathogen recognition was observed, proving the concrete applicability of our system for on-site and in-food detection.

Involvement of released sphingosine 1-phosphate/sphingosine 1-phosphate receptor axis in skeletal muscle atrophy.

Skeletal muscle (SkM) atrophy is caused by several and heterogeneous conditions, such as cancer, neuromuscular disorders and aging. In most types of SkM atrophy overall rates of protein synthesis are suppressed, protein degradation is consistently elevated and atrogenes, such as the ubiquitin ligase Atrogin-1/MAFbx, are up-regulated. The molecular regulators of SkM waste are multiple and only in part known. Sphingolipids represent a class of bioactive molecules capable of modulating the destiny of many cell types, including SkM cells. In particular, we and others have shown that sphingosine 1phosphate (S1P), formed by sphingosine kinase (SphK), is able to act as trophic and morphogenic factor in myoblasts. Here, we report the first evidence that the atrophic phenotype observed in both muscle obtained from mice bearing the C26 adenocarcinoma and C2C12 myotubes treated with dexamethasone was characterized by reduced levels of active phospho-SphK1. The importance of SphK1 activity is also confirmed by the specific pharmacological inhibition of SphK1 able to increase Atrogin-1/MAFbx expression and reduce myotube size and myonuclei number. Furthermore, we found that SkM atrophy was accomplished by significant increase of S1P transporter Spns2 and in changes in the pattern of S1P receptor (S1PRs) subtype expression paralleled by increased Atrogin-1/MAFbx expression, suggesting a role for the released S1P and of specific S1PR-mediated signaling pathways in the control of the ubiquitin ligase. Altogether, these findings provide the first evidence that SphK1/released S1P/S1PR axis acts as a molecular regulator of SkM atrophy, thereby representing a new possible target for therapy in many patho-physiological conditions.

Sphingosine 1-Phosphate Receptor 1 Is Required for MMP-2 Function in Bone Marrow Mesenchymal Stromal Cells: Implications for Cytoskeleton Assembly and Proliferation.

Bone marrow-derived mesenchymal stromal cell- (BM-MSC-) based therapy is a promising option for regenerative medicine. An important role in the control of the processes influencing the BM-MSC therapeutic efficacy, namely, extracellular matrix remodelling and proliferation and secretion ability, is played by matrix metalloproteinase- (MMP-) 2. Therefore, the identification of paracrine/autocrine regulators of MMP-2 function may be of great relevance for improving BM-MSC therapeutic potential. We recently reported that BM-MSCs release the bioactive lipid sphingosine 1-phosphate (S1P) and, here, we demonstrated an impairment of MMP-2 expression/release when the S1P receptor subtype S1PR1 is blocked. Notably, active S1PR1/MMP-2 signalling is required for F-actin structure assembly (lamellipodia, microspikes, and stress fibers) and, in turn, cell proliferation. Moreover, in experimental conditions resembling the damaged/regenerating tissue microenvironment (hypoxia), S1P/S1PR1 system is also required for HIF-1α expression and vinculin reduction. Our findings demonstrate for the first time the trophic role of S1P/S1PR1 signalling in maintaining BM-MSCs' ability to modulate MMP-2 function, necessary for cytoskeleton reorganization and cell proliferation in both normoxia and hypoxia. Altogether, these data provide new perspectives for considering S1P/S1PR1 signalling a pharmacological target to preserve BM-MSC properties and to potentiate their beneficial potential in tissue repair.

Sphingosine 1-Phosphate Receptors: Do They Have a Therapeutic Potential in Cardiac Fibrosis?

Sphingosine 1-phosphate (S1P) is a bioactive lipid that is characterized by a peculiar mechanism of action. In fact, S1P, which is produced inside the cell, can act as an intracellular mediator, whereas after its export outside the cell, it can act as ligand of specific G-protein coupled receptors, which were initially named endothelial differentiation gene (Edg) and eventually renamed sphingosine 1-phosphate receptors (S1PRs). Among the five S1PR subtypes, S1PR1, S1PR2 and S1PR3 isoforms show broad tissue gene expression, while S1PR4 is primarily expressed in immune system cells, and S1PR5 is expressed in the central nervous system. There is accumulating evidence for the important role of S1P as a mediator of many processes, such as angiogenesis, carcinogenesis and immunity, and, ultimately, fibrosis. After a tissue injury, the imbalance between the production of extracellular matrix (ECM) and its degradation, which occurs due to chronic inflammatory conditions, leads to an accumulation of ECM and, consequential, organ dysfunction. In these pathological conditions, many factors have been described to act as pro- and anti-fibrotic agents, including S1P. This bioactive lipid exhibits both pro- and anti-fibrotic effects, depending on its site of action. In this review, after a brief description of sphingolipid metabolism and signaling, we emphasize the involvement of the S1P/S1PR axis and the downstream signaling pathways in the development of fibrosis. The current knowledge of the therapeutic potential of S1PR subtype modulators in the treatment of the cardiac functions and fibrinogenesis are also examined.

Crosstalk between sphingolipids and vitamin D3: potential role in the nervous system.

Sphingolipids are both structural and bioactive compounds. In particular, ceramide and sphingosine 1-phosphate regulate cell fate, inflammation and excitability. 1-α,25-dihydroxyvitamin D3 (1,25(OH)2 D3 ) is known to play an important physiological role in growth and differentiation in a variety of cell types, including neural cells, through genomic actions mediated by its specific receptor, and non-genomic effects that result in the activation of specific signalling pathways. 1,25(OH)2 D3 and sphingolipids, in particular sphingosine 1-phosphate, share many common effectors, including calcium regulation, growth factors and inflammatory cytokines, but it is still not known whether they can act synergistically. Alterations in the signalling and concentrations of sphingolipids and 1,25(OH)2 D3 have been found in neurodegenerative diseases and fingolimod, a structural analogue of sphingosine, has been approved for the treatment of multiple sclerosis. This review, after a brief description of the role of sphingolipids and 1,25(OH)2 D3 , will focus on the potential crosstalk between sphingolipids and 1,25(OH)2 D3 in neural cells.

Surface plasmon resonance based on molecularly imprinted nanoparticles for the picomolar detection of the iron regulating hormone Hepcidin-25.

BACKGROUND: Molecularly imprinted polymer (MIP) technique is a powerful mean to produce tailor made synthetic recognition sites. Here precipitation polymerization was exploited to produce a library of MIP nanoparticles (NPs) targeting the N terminus of the hormone Hepcidin-25, whose serum levels correlate with iron dis-metabolisms and doping. Biotinylated MIP NPs were immobilized to NeutrAvidin™ SPR sensor chip. The response of the MIP NP sensor to Hepcidin-25 was studied. FINDINGS: Morphological analysis showed MIP NPs of 20-50 nm; MIP NP exhibited high affinity and selectivity for the target analyte: low nanomolar Kds for the interaction NP/Hepcidin-25, but none for the NP/non regulative Hepcidin-20. The MIP NP were integrated as recognition element in SPR allowing the detection of Hepcidin-25 in 3 min. Linearity was observed with the logarithm of Hepcidin-25 concentration in the range 7.2-720 pM. LOD was 5 pM. The response for Hepcidin-20 was limited. Hepcidin-25 determination in real serum samples spiked with known analyte concentrations was also attempted. CONCLUSION: The integration of MIP NP to SPR allowed the determination of Hepcidin-25 at picomolar concentrations in short times outperforming the actual state of art. Optimization is still needed for real sample measurements in view of future clinical applications.