Mitochondria-Specific Molecular Crosstalk between Ferroptosis and Apoptosis Revealed by In Situ Raman Spectroscopy.

Ferroptosis and apoptosis are two types of regulated cell death that are closely associated with the pathophysiological processes of many diseases. The significance of ferroptosis-apoptosis crosstalk in cell fate determination has been reported, but the underlying molecular mechanisms are poorly understood. Herein mitochondria-mediated molecular crosstalk is explored. Based on a comprehensive spectroscopic investigation and mass spectrometry, cytochrome c-involved Fenton-like reactions and lipid peroxidation are revealed. More importantly, cytochrome c is found to induce ROS-independent and cardiolipin-specific lipid peroxidation depending on its redox state. In situ Raman spectroscopy unveiled that erastin can interrupt membrane permeability, specifically through cardiolipin, facilitating cytochrome c release from the mitochondria. Details of the erastin-cardiolipin interaction are determined using molecular dynamics simulations. This study provides novel insights into how molecular crosstalk occurs around mitochondrial membranes to trigger ferroptosis and apoptosis, with significant implications for the rational design of mitochondria-targeted cell death reducers in cancer therapy.

In Situ Raman Spectroscopy Reveals Cytochrome c Redox-Controlled Modulation of Mitochondrial Membrane Permeabilization That Triggers Apoptosis.

The selective interaction of cytochrome c (Cyt c) with cardiolipin (CL) is involved in mitochondrial membrane permeabilization, an essential step for the release of apoptosis activators. The structural basis and modulatory mechanism are, however, poorly understood. Here, we report that Cyt c can induce CL peroxidation independent of reactive oxygen species, which is controlled by its redox states. The structural basis of the Cyt c-CL binding was unveiled by comprehensive spectroscopic investigation and mass spectrometry. The Cyt c-induced permeabilization and its effect on membrane collapse, pore formation, and budding are observed by confocal microscopy. Moreover, cytochrome c oxidase dysfunction is found to be associated with the initiation of Cyt c redox-controlled membrane permeabilization. These results verify the significance of a redox-dependent modulation mechanism at the early stage of apoptosis, which can be exploited for the design of cytochrome c oxidase-targeted apoptotic inducers in cancer therapy.

In Situ Monitoring of Membrane Protein Electron Transfer via Surface-Enhanced Resonance Raman Spectroscopy.

In situ analysis of membrane protein-ligand interactions under physiological conditions is of significance for both fundamental and applied science, but it is still a big challenge due to the limits in sensitivity and selectivity. Here, we demonstrate the potential of surface-enhanced resonance Raman spectroscopy (SERRS) for the investigation of membrane protein-protein interactions. Lipid biolayers are successfully coated on silver nanoparticles through electrostatic interactions, and a highly sensitive and biomimetic membrane platform is obtained in vitro. Self-assembly and immobilization of the reduced cytochrome b5 on the coated membrane are achieved and protein native biological functions are preserved. Owing to resonance effect, the Raman fingerprint of the immobilized cytochrome b5 redox center is selectively enhanced, allowing for in situ and real-time monitoring of the electron transfer process between cytochrome b5 and their partners, cytochrome c and myoglobin. This study provides a sensitive analytical approach for membrane proteins and paves the way for in situ exploration of their structural basis and functions.

Flexible SERS Biosensor Based on Core-Shell Nanotags for Sensitive and Multiple Detection of T1DM Biomarkers.

Sensitive and multiple detection of the biomarkers of type 1 diabetes mellitus (T1DM) is vital to the early diagnosis and clinical treatment of T1DM. Herein, we developed a SERS-based biosensor using polyvinylidene fluoride (PVDF) membranes as a flexible support for the detection of glutamic acid decarboxylase antibodies (GADA) and insulin autoantibodies (IAA). Two kinds of silver-gold core-shell nanotags embedded with Raman probes and attached with GADA or IAA antibodies were synthesized to capture the targets, enabling highly sensitive and highly selective detection of GADA and IAA. The embedded Raman probes sandwiched between silver and gold layers guaranteed spectral stability and reliability. Moreover, the utilization of two Raman probes enables simultaneous and multiplexing detection of both GADA and IAA, improving the detection accuracy for T1DM. The proposed SERS-based method has been proven feasible for clinical sample detection, demonstrating its great potential in sensitive, reliable, and rapid diagnosis of T1DM.

In Situ and Real-Time Monitoring of Mitochondria-Endoplasmic Reticulum Crosstalk in Apoptosis via Surface-Enhanced Resonance Raman Spectroscopy.

The crosstalk between mitochondria and endoplasmic reticula plays a crucial role in apoptotic pathways in which reactive oxygen species (ROS) produced by microsomal monooxygenase (MMO) are believed to accelerate cytochrome c release. Herein, we successfully demonstrate the potential of surface-enhanced resonance Raman spectroscopy (SERRS) for monitoring MMO-derived ROS formation and ROS-mediated cytochrome c release. Silver nanoparticles coated with nickel shells are used as both Raman signal enhancers and electron donors for cytochrome c. SERRS of cytochrome c is found to be sensitive to ROS, allowing for in situ probing of ROS formation with a cell death inducer. Label-free evaluation of ROS-induced apoptosis is achieved by SERRS-based monitoring of cytochrome c release in living cells. This study verifies the capability of SERRS for label-free, in situ, and real-time monitoring of the mitochondria-endoplasmic reticulum crosstalk in apoptosis and provides a novel strategy for the rational design and screening of ROS-inducing drugs for cancer treatment.

Co-Immobilization of GOD & HRP on Y-Shaped DNA Scaffold and the Regulation of Inter-Enzyme Distance.

In multienzymes cascade reaction, the inter-enzyme spacing is supposed to be a factor affecting the cascade activity. Here, a simple and efficient Y-shaped DNA scaffold is assembled using two partially complementary DNA single strands on magnetic microspheres, which is used to coimmobilize glucose oxidase (GOD) and horseradish peroxidase (HRP). As a result, on poly(vinyl acetate) magnetic microspheres (PVAC), GOD/HRP-DNA@PVAC multienzyme system is obtained, which can locate GOD and HRP accurately and control the inter-enzyme distance precisely. The distance between GOD and HRP is regulated by changing the length of DNA strand. It showed that the cascade activity is significantly distance-dependent. Moreover, the inter-enzyme spacing is not the closer the better, and too short distance would generate steric hindrance between enzymes. The cascade activity reached the maximum value of 967 U mg-1 at 13.6 nm, which is 3.5 times higher than that of free enzymes. This is ascribed to the formation of substrate channeling.

A New Evidential Reasoning Rule Considering Interval Uncertainty and Perturbation.

The evidential reasoning (ER) rule has been widely applied in the multiple attribute decision making (MADM), which makes the decision-making process transparent and credible by using a belief structure. To improve the ability of the ER rule in dealing with the interval uncertainty, a new interval ER (IER) rule is proposed in this article. The interval uncertainty is described as the interval grade in the new frame of discernment (FoD) to model the local ignorance. It is proved that the IER rule is a generalization of the ER rule. To study the influence of perturbation on the IER rule, the perturbation is first introduced to the belief structure, and the perturbation analysis (PA) is conducted for the IER rule. An optimization model is established to estimate the perturbation threshold, which can measure the effectiveness of the inference result under perturbation. Two numerical examples and a case study are carried out, respectively, to show the implementation process of the proposed IER rule and validate its effectiveness in different decision-making scenarios.

Detection of prostate cancer biomarkers via a SERS-based aptasensor.

The overexpression of specific biomarkers in serum is closely related to diseases, and accurate and sensitive detection of them is beneficial for the early diagnosis and treatment of cancer. In this study, we developed a novel surface-enhanced Raman spectroscopy (SERS)-based aptasensor to detect the prostate-specific antigen biomarkers, consisting of total prostate-specific antigen (PSA) and free prostate-specific antigen (f-PSA). A composite structure containing arrays of polystyrene colloidal sphere @Ag shell (PS@Ag) was fabricated as a SERS-active chip. A complementary DNA probe (SH-DNA) and PSA aptamer (Apt) were immobilised stepwise on the chip, followed by the binding of a Raman reporter methylene blue (MB) to the guanine base of the aptamer. PSA-Apt recognition causes the release of MB-Apt and a decrease in the SERS intensity of MB on the chip, which correlates with the PSA concentration. The proposed biosensor has high spectral reproducibility, selectivity, and sensitivity and successfully determines the PSA levels in serum samples collected from prostate cancer patients, demonstrating great potential for clinical diagnosis.

Innovative Application of SERS in Food Quality and Safety: A Brief Review of Recent Trends.

Innovative application of surface-enhanced Raman scattering (SERS) for rapid and nondestructive analyses has been gaining increasing attention for food safety and quality. SERS is based on inelastic scattering enhancement from molecules located near nanostructured metallic surfaces and has many advantages, including ultrasensitive detection and simple protocols. Current SERS-based quality analysis contains composition and structural information that can be used to establish an electronic file of the food samples for subsequent reference and traceability. SERS is a promising technique for the detection of chemical, biological, and harmful metal contaminants, as well as for food poisoning, and allergen identification using label-free or label-based methods, based on metals and semiconductors as substrates. Recognition elements, including immunosensors, aptasensors, or molecularly imprinted polymers, can be linked to SERS tags to specifically identify targeted contaminants and perform authenticity analysis. Herein, we highlight recent studies on SERS-based quality and safety analysis for different foods categories spanning the whole food chain, 'from farm to table' and processing, genetically modified food, and novel foods. Moreover, SERS detection is a potential tool that ensures food safety in an easy, rapid, reliable, and nondestructive manner during the COVID-19 pandemic.

Electron transfer between cytochrome c and microsomal monooxygenase generates reactive oxygen species that accelerates apoptosis.

Generation of reactive oxygen species (ROS) are possibly induced by the crosstalk between mitochondria and endoplasmic reticula, which is physiologically important in apoptosis. Cytochrome c (Cyt c) is believed to play a crucial role in such signaling pathway by interrupting the coupling within microsomal monooxygenase (MMO). In this study, the correlation of ROS production with the electron transfer between Cyt c and the MMO system is investigated by resonance Raman (RR) spectroscopy. Binding of Cyt c to MMO is found to induce the production of ROS, which is quantitatively determined by the in-situ RR spectroscopy reflecting the interactions of Cyt c with generated ROS. The amount of ROS that is produced from isolated endoplasmic reticulum depends on the redox state of the Cyt c, indicating the important role of oxidized Cyt c in accelerating apoptosis. The role of electron transfer from MMO to Cyt c in the apoptotic mitochondria-endoplasmic reticulum pathway is accordingly proposed. This study is of significance for a deeper understanding of how Cyt c regulates apoptotic pathways through the endoplasmic reticulum, and thus may provide a rational basis for the design of antitumor drugs for cancer therapy.

Metal-semiconductor heterostructures for surface-enhanced Raman scattering: synergistic contribution of plasmons and charge transfer.

After 45 years of its first observation, surface-enhanced Raman spectroscopy (SERS) has become an ultrasensitive tool applied in chemical analysis, materials science, and biomedical research. SERS-active nanomaterials, such as noble metals, transition metals, and semiconductors, have undergone extensive development. The hybridization of semiconductors with plasmonic metal nanomaterials is highly effective in boosting light harvesting and conversion, which enables the rapid growth of metal-semiconductor hybrid nanostructures in SERS-based research fields. With the combination of the unique photoelectric properties and giant SERS signals attributed to the synergistic contribution of plasmons and change transfer (CT), metal-semiconductor heterostructures allow diverse and novel applications of SERS in CT investigations for the rational design of photovoltaic devices and ultrasensitive chemical or biological sensing. In this review, we specifically discuss SERS-active metal-semiconductor heterostructures including their building blocks, enhancement mechanisms, and applications. Moreover, we highlight the current challenges and opportunities for future research in this field based on our recent studies and other related research.

Comprehensive Strategy for Sample Preparation for the Analysis of Food Contaminants and Residues by GC-MS/MS: A Review of Recent Research Trends.

Food safety and quality have been gaining increasing attention in recent years. Gas chromatography coupled to tandem mass spectrometry (GC-MS/MS), a highly sensitive technique, is gradually being preferred to GC-MS in food safety laboratories since it provides a greater degree of separation on contaminants. In the analysis of food contaminants, sample preparation steps are crucial. The extraction of multiple target analytes simultaneously has become a new trend. Thus, multi-residue analytical methods, such as QuEChERs and adsorption extraction, are fast, simple, cheap, effective, robust, and safe. The number of microorganic contaminants has been increasing worldwide in recent years and are considered contaminants of emerging concern. High separation in MS/MS might be, in certain cases, favored to sample preparation selectivity. The ideal sample extraction procedure and purification method should take into account the contaminants of interest. Moreover, these methods should cooperate with high-resolution MS, and other sensitive full scan MSs that can produce a more comprehensive detection of contaminants in foods. In this review, we discuss the most recent trends in preparation methods for highly effective detection and analysis of food contaminants, which can be considered tools in the control of food quality and safety.

High-efficiency charge transfer on SERS-active semiconducting K2Ti6O13 nanowires enables direct transition of photoinduced electrons to protein redox centers.

Photoinduced charge transfer (PICT) plays a crucial role in the chemical mechanism of surface-enhanced Raman scattering (SERS), in which small organic molecules are generally used as probes. Herein, semiconducting K2Ti6O13 nanowires (NWs) are synthesized and are found to exhibit high SERS activity probed by 4-mercaptobenzoic acid (4-MBA). Density functional theory (DFT) calculations reveal high-efficiency CT on the K2Ti6O13 nanowires. Furthermore, PICT on the K2Ti6O13 NWs is for the first time evidenced by a redox protein, cytochrome c (Cyt c). Under optimized experimental conditions, the transformation of oxidized Cyt c to its reduced state clearly verifies the electron transfer (ET) from the K2Ti6O13 nanowire to the protein. The ET mechanism is explored based on energy levels of semiconductors and molecular dynamics simulations, thus revealing the importance of energy level matching and electron tunneling from the semiconductor surface to the redox center. This study indicates a great potential of multiple-layered K2Ti6O13 NWs in the application of SERS on semiconducting materials and more importantly, it provides a new route for the rational design of protein-semiconductor interfaces for investigating electron transfer processes of redox proteins and biocatalytic reactions.

In-situ fingerprinting phosphorylated proteins via surface-enhanced Raman spectroscopy: Single-site discrimination of Tau biomarkers in Alzheimer's disease.

Protein phosphorylation, a post-translational modification of proteins, is of vital importance in biological regulation. Highly sensitive and site-specific identification of phosphorylated proteins is a key requirement for unraveling crucial signal transduction pathways relevant to cancers and neurodegenerative disorders. Traditional detection methods, however, suffer from relying on antibodies, labels or fragmentation prior to analysis. Here, an antibody- and label-free in situ approach to fingerprint protein phosphorylation was developed based on intrinsic Raman vibrational information of phosphorylated tyrosine, serine, threonine, or histidine residues. Combining surface-enhanced Raman scattering (SERS) spectroscopy and an immobilized-metal affinity strategy, this method is ultrasensitive to discriminate a single-site phosphorylated S396 in a Tau410 protein, an important biomarker in Alzheimer's disease. The binding feasibility of phosphorylated proteins to the modified SERS-active materials is further evidenced by molecular dynamics simulations. This proof-of-concept study paves a new way for the evaluation of site-specific and intact protein phosphorylation in both fundamental mechanical investigation and clinical applications.

Role of 2‒13C Isotopic Glyphosate Adsorption on Silver Nanoparticles Based on Ninhydrin Reaction: A Study Based on Surface-Enhanced Raman Spectroscopy.

Glyphosate is one of the most commonly used and non-selective herbicides in agriculture, which may directly pollute the environment and threaten human health. A simple and effective approach to its detection is thus quite necessary. Surface-enhanced Raman scattering (SERS) spectroscopy was shown to be a very effective method to approach the problem. However, sensitivity in SERS experiments is quite low, caused by different orientation/conformation of the adsorbed molecules on the metal surface, which limit its detection by using SERS. In this paper, 2‒13C‒glyphosate (hereafter: 13-GLP) was designed as a model molecule for theoretical and experimental studies of the molecule structure. Vibrational modes were assigned based on the modeling results obtained at the B3LYP/6-311++G** level by density functional theory (DFT) calculations, which were performed to predict the FT‒IR and Raman spectra. Band downshifts were caused by 13C atom isotopic substitution with mass changed. Moreover, SERS spectra of 13-GLP by combining ninhydrin reaction on Ag NPs were obtained. Isotopic Raman shifts are helpful in identifying the components of each Raman band through vibrations across the molecular system. They are coupled by probe molecules and thus bind to the substrates, indirectly offering the opportunity to promote interactions with Ag NPs and reduce the complex equilibrium between different orientation/conformation of glyphosate molecules on the metal surface.

Mechanistic Insights into the Cytotoxicity of Graphene Oxide Derivatives in Mammalian Cells.

Graphene oxide derivatives (GODs) have superb physical/chemical properties with promise for applications in biomedicine. Shape, size, and chemistry of the GODs are identified as the key parameters that impact any biological system. In this work, the GODs with a wide range of shapes (sheets, helical/longitudinal ribbons, caps, dots), sizes (10 nm to 20 µm), and chemistry (partially to fully oxidized) are synthesized, and their cytotoxicity in normal cells (NIH3T3) and colon cancer cells (HCT116) are evaluated. The mechanisms by which the GODs induce cytotoxicity are comprehensively investigated, and the toxic effects of the GODs on the NIH3T3 and the HCT116 cells are compared. While the GODs show no toxicity under the size of 50 nm, they impose moderate toxic effects at the sizes of 100 nm to 20 µm (max viability >57%). For the GODs with the similar size (100-200 nm), the helical ribbon-like structure is found to be much less toxic than the longitudinal ribbon structure (max viability 83% vs 18%) and the tubular structure (0% viability for the oxidized carbon nanotubes). It is also evident that the level of oxidation of the GOD is inversely related to the toxicity. Although the extent of GOD-induced cytotoxicity (reduction of cell viability) to the two cell lines is similar, their toxicity mechanisms are interestingly found to be substantially different. In the HCT116 cancer cells, cell membrane leakage leads to DNA damage followed by cell death, whereas in the NIH3T3 normal cells, increases in oxidative stress and physical interference between the GODs and the cells are identified as the main toxicity sources.

Qualitative analysis of contrast-enhanced ultrasound in the diagnosis of small, TR3-5 benign and malignant thyroid nodules measuring ≤1 cm.

OBJECTIVE: To evaluate the performance of contrast-enhanced ultrasound in the diagnosis of small, solid, TR3-5 benign and malignant thyroid nodules (≤1 cm). METHODS: From January 2016 to March 2018, 185 thyroid nodules from 154 patients who underwent contrast enhanced ultrasound (CEUS) and fine-needle aspiration or thyroidectomy in Shanghai General Hospital were included. The χ2 test was used to compare the CEUS characteristics of benign and malignant thyroid nodules, and the CEUS features of malignant nodules assigned scores. The total score of the CEUS features and the scores of the above nodules were evaluated according to the latest 2017 version of the Thyroid Imaging Reporting and Data System (TI-RADS). The diagnostic performance of the two were compared based on the receiver operating characteristic curves generated for benign and malignant thyroid nodules. RESULTS: The degree, enhancement patterns, boundary, shape, and homogeneity of enhancement in thyroid small solid nodules were significantly different (p＜0.05). No significant differences were seen between benign and malignant thyroid nodules regarding completeness of enhancement and size of enhanced lesions (p＞0.05). The sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of the TI-RADS classification TR5 in diagnosis of malignant nodules were 90.10%, 55.95%, 74.59%, 72.22%, and 82.46%, respectively (area under the curve [AUC]=0.738; 95% confidence interval[CI], 0.663-0.813). The sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of the total score of CEUS qualitative analysis indicators were 86.13%, 89.29%, 87.57%, 90.63%, and 84.27% respectively (AUC = 0.916; 95% CI, 0.871-0.961). CONCLUSION: CEUS qualitative analysis is superior to TI-RADS in evaluating the diagnostic performance of small, solid thyroid nodules. Qualitative analysis of CEUS has a significantly higher specificity for diagnosis of malignant thyroid nodules than TI-RADS. ADVANCES IN KNOWLEDGE: The 2017 version of TI-RADS has recently suggested the malignant stratification of thyroid nodules by ultrasound. In this paper we applied this system and CEUS to evaluate 185 nodules and compare the results with pathological findings to access the diagnostic performance.

Direct Dynamic Evidence of Charge Separation in a Dye-Sensitized Solar Cell Obtained under Operando Conditions by Raman Spectroscopy.

Interfaces play an important role in enhancing the energy conversion performance of dye-sensitized solar cells (DSCs). The interface effects have been studied by many techniques, but most of the studies only focused on one part of a DSC, rather than on a complete solar cell. Hence, monitoring the interface evolution of a DSC is still very challenging. Here, in situ/operando resonance Raman (RR) spectroscopic analyses were carried out to monitor the dynamics of the photovoltaic conversion processes in a DSC. We observed the creation of new species (i.e., polyiodide and iodine aggregates) in the photosensitization process. We also obtained molecular-scale dynamic evidence that the bands from the C=C and C=N bonds of 2,2'-bipyridyl (bpy), the S=C=N bonds of the NCS ligand, and photochemical products undergo reasonably strong intensity and frequency changes, which clearly demonstrates that they are involved in charge separation. Furthermore, RR spectroscopy can also be used to quickly evaluate the performance of DSCs.

Redox-State-Mediated Regulation of Cytochrome†c Release in Apoptosis Revealed by Surface-Enhanced Raman Scattering on Nickel Substrates.

The interaction of cytochrome c (Cyt c) with cardiolipin (CL) is believed to play an important role in the initial events of apoptosis. Herein, we investigate the structural changes of CL-bound Fe2+ Cyt c and the correlation with Cyt c release through surface-enhanced Raman spectroscopy (SERS) on nickel substrates. The SERS results together with molecular dynamics simulation reveal that Fe2+ Cyt c undergoes autoxidation and a relatively larger conformational alteration after binding with CL, inducing higher peroxidase activity of Cyt c and higher permeability of the CL membrane compared with those induced by the Fe3+ Cyt c. The proapoptotic activity and SERS effect of the Ni nanostructures allow the in situ study of the redox-state-dependent Cyt c release from isolated mitochondria, which reveals for the first time that the ferrous state of Cyt c most likely plays a more important role in triggering apoptosis.

Frequency Shifts in Surface-Enhanced Raman Spectroscopy-Based Immunoassays: Mechanistic Insights and Application in Protein Carbonylation Detection.

Frequency-shift based surface-enhanced Raman spectroscopy (SERS) has exhibited great potential applications in bioanalytical chemistry and biomedicine in recent years. The basis and the crucial factors determining frequency shifts are, however, still unclear. Herein, we have systematically investigated how solvents, antigens, and antibodies affect the band shifts in SERS-based immunoassays. By applying the charge transfer theory together with the Stark effect and time-dependent density functional theory (TDDFT) calculation, mechanistic insights into the frequency shifts in immunoreactions is proposed and discussed in detail. Accordingly, the experimental condition is further optimized and is successfully applied for the first time to detect carbonylated proteins, promising diagnostic biomarkers for human diseases. This study provides theoretical guidance for designing SERS frequency shift-based immunoassays and paves a new avenue for further applications of the strategy in clinical diagnosis.