Pursuing shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) for concomitant detection of breast lesions and microcalcifications

Physicochemical understanding of biomineralization by molecular vibrational spectroscopy: From mechanism to nature

The process and mechanism of biomineralization and relevant physicochemical properties of mineral crystals are remarkably sophisticated multidisciplinary fields that include biology, chemistry, physics, and materials science. The components of the organic matter, structural construction of minerals, and related mechanical interaction, etc., could help to reveal the unique nature of the special mineralization process. Herein, the paper provides an overview of the biomineralization process from the perspective of molecular vibrational spectroscopy, including the physicochemical properties of biomineralized tissues, from physiological to applied mineralization. These physicochemical characteristics closely to the hierarchical mineralization process include biological crystal defects, chemical bonding, atomic doping, structural changes, and content changes in organic matter, along with the interface between biocrystals and organic matter as well as the specific mechanical effects for hardness and toughness. Based on those observations, the special physiological properties of mineralization for enamel and bone, as well as the possible mechanism of pathological mineralization and calcification such as atherosclerosis, tumor micro mineralization, and urolithiasis are also reviewed and discussed. Indeed, the clearly defined physicochemical properties of mineral crystals could pave the way for studies on the mechanisms and applications.

Probing plasmon-induced surface reactions using two-dimensional correlation vibrational spectroscopy

Surface plasmon resonance (SPR) has the ability to drive catalytic conversion of the reactant molecules via the production of hot electrons, which in general requires high activation energy. The reactions driven by these hot electrons are critical and essential in various heterogeneous surface catalytic reactions. However, there is a need to understand the dynamics of surface reactions and the underlying mechanism, which are influenced by several factors such as the constitution of the nanoparticle, exposure time, and reaction conditions to name a few. However, the effect of solvent in stabilizing the electron-hole pair, the orientation, and the surface coverage of the analyte are poorly understood due to the limitations of current methods. To get deeper insights into the reaction dynamics, we have demonstrated the combined utility of plasmon-enhanced Raman spectroscopy and Two-dimensional correlation spectroscopy (2DCOS) to study the plasmon-driven conversion of 4-nitrothiophenol on the surface of plasmonic nanoparticles. Interestingly, this combined technique provided us with previously unobservable results regarding surface catalysis by conventional spectroscopic analysis alone. Specifically, for the first time, 2DCOS provided critical insights in bridging the gap in our understanding of the interplay of solvent effect, orientation, and surface packing of the analyte molecules. It was observed that certain species like 4,4-dimercaptoazobenzene (DMAB) or 4-aminothiophenol (4-ATP) can be selectively formed based on the ordered or disordered phases of the analytes on the surface, thus paving the way to precisely control light-driven reactions through operando spectroscopy.

Raman spectroscopy: current applications in breast cancer diagnosis, challenges and future prospects

Despite significant improvements in the way breast cancer is managed and treated, it continues to persist as a leading cause of death worldwide. If detected and diagnosed early, when tumours are small and localised, there is a considerably higher chance of survival. However, current methods for detection and diagnosis lack the required sensitivity and specificity for identifying breast cancer at the asymptomatic or very early stages. Thus, there is a need to develop more rapid and reliable methods, capable of detecting disease earlier, for improved disease management and patient outcome. Raman spectroscopy is a non-destructive analytical technique that can rapidly provide highly specific information on the biochemical composition and molecular structure of samples. In cancer, it has the capacity to probe very early biochemical changes that accompany malignant transformation, even prior to the onset of morphological changes, to produce a fingerprint of disease. This review explores the application of Raman spectroscopy in breast cancer, including discussion on its capabilities in analysing both ex-vivo tissue and liquid biopsy samples, and its potential in vivo applications. The review also addresses current challenges and potential future uses of this technology in cancer research and translational clinical application.

A universal polymer shell-isolated nanoparticle (SHIN) design for single particle spectro-electrochemical SERS sensing using different core shapes

Shell-isolated nanoparticles (SHINs) have attracted increasing interest for non-interfering plasmonic enhanced sensing in fields such as materials science, biosensing, and in various electrochemical systems. The metallic core of these nanoparticles is isolated from the surrounding environment preventing direct contact or chemical interaction with the metal surface, while still being close enough to enable localized surface plasmon enhancement of the Raman scattering signal from the analyte. This concept forms the basis of the shell isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) technique. To date, the vast majority of SHIN designs have focused on SiO₂ shells around spherical nanoparticle cores and there has been very limited published research considering alternatives. In this article, we introduce a new polymer-based approach which provides excellent control over the layer thickness and can be applied to plasmonic metal nanoparticles of various shapes and sizes without compromising the overall nanoparticle morphology. The SHIN layers are shown to exhibit excellent passivation properties and robustness in the case of gold nanosphere (AuNP) and anisotropic gold nanostar (AuNS) core shapes. In addition, in situ SHINERS spectro-electrochemistry measurements performed on both SHIN and bare Au nanoparticles demonstrate the utility of the SHIN coatings. Correlated confocal Raman and SEM mapping was achieved to clearly establish single nanoparticle SERS sensitivity. Finally, confocal in situ SERS mapping enabled visualisation of the redox related molecular structure changes occurring on an electrode surface in the vicinity of individual SHIN-coated nanoparticles.

Advancing Raman spectroscopy from research to clinic: Translational potential and challenges

Raman spectroscopy has emerged as a non-invasive and versatile diagnostic technique due to its ability to provide molecule-specific information with ultrahigh sensitivity at near-physiological conditions. Despite exhibiting substantial potential, its translation from optical bench to clinical settings has been impacted by associated limitations. This perspective discusses recent clinical and biomedical applications of Raman spectroscopy and technological advancements that provide valuable insights and encouragement for resolving some of the most challenging hurdles.

Molecular fingerprint of precancerous lesions in breast atypical hyperplasia

OBJECTIVE

To identify atypical hyperplasia (AH) of the breast by shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS), and to explore the molecular fingerprinting characteristics of breast AH.

METHODS

Breast hyperplasia was studied in 11 hospitals across China from January 2015 to December 2016. All patients completed questionnaires on women's health. The differences between patients with and without breast AH were compared. AH breast lesions were detected by Raman spectroscopy followed by the SHINERS technique.

RESULTS

There were no significant differences in clinical features and risk-related factors between patients with breast AH (n = 37) and the control group (n = 2576). Fifteen cases of breast AH lesions were detected by Raman spectroscopy. The main different Raman peaks in patients with AH appeared at 880, 1001, 1086, 1156, 1260, and 1610 cm^-1, attributed to the different vibrational modes of nucleic acids, β-carotene, and proteins. Shell-isolated nanoparticles had different enhancement effects on the nucleic acid, protein, and lipid components in AH.

CONCLUSION

Raman spectroscopy can detect characteristic molecular changes in breast AH lesions, and may thus be useful for the non-invasive early diagnosis and for investigating the mechanism of tumorigenesis in patients with breast AH.

Characterization and imaging of surgical specimens of invasive breast cancer and normal breast tissues with the application of Raman spectral mapping: A feasibility study and comparison with randomized single-point detection method

A mapping technique was used in the present study to explore the biological and imaging characteristics of invasive breast cancer and normal breast tissues in Raman examination data and construct a diagnostic model for breast cancer. Raman examination data reflect the biochemical or molecular characteristics of the target tissues. A total of 45 specimens from patients with breast cancer who underwent surgery and 25 adjacent normal breast tissue specimens were included in the present study. Using the specimens, a total of 53 sets of mapping data and 2,597 pieces of Raman spectral data were obtained. The collected spectra were corrected and fitted, the Raman spectra were analyzed by robust statistical methods, and a diagnostic model was constructed using the k-Nearest Neighbor (KNN) method. The KNN classification method was applied to analyze the characteristics of the mapping test application. The percentage of outliers in the mapping data for malignant and normal breast tissues was 12.7 and 6.6%, respectively. The percentage of outlier data in the conventional single-point detection data for malignant and normal breast tissues was 24.5 and 26.0%, respectively. Analysis using a t-test identified a significant difference in the number of outliers between mapping and single-point detection for malignant (t=−6.169; P<0.001) and normal breast tissues (t=−8.873; P<0.001). Based on the mapping data, the accuracy, sensitivity and specificity for breast cancer detection by the diagnostic model constructed using the KNN method was 99.56, 96.6 and 98.48%, respectively. The positive and negative predictive value of this model was 99.56 and 89.04%, respectively. The data obtained by mapping technology demonstrated improved stability and contained less outliers compared with single-point detection. The diagnostic model constructed using the mapping data demonstrated excellent diagnostic performance and good correspondence with pathological results. The findings of the present study demonstrated the feasibility of the application of the diagnostic model for intraoperative real-time imaging for patients with breast cancer. This study provided the foundation of Raman spectroscopy-based diagnostic imaging at the molecular level.

A Review of Chinese Raman Spectroscopy Research Over the Past Twenty Years

This paper introduces the major Chinese research groups in the fields of biomedicine, food safety, environmental testing, material research, archaeological and cultural relics, gem identification, forensic science, and other research areas of Raman spectroscopy and combined methods spanning the two decades from 1997 to 2017. Briefly summarized are the research directions and contents of the major Chinese Raman spectroscopy research groups, giving researchers engaged in Raman spectroscopy research a more comprehensive understanding of the state of Chinese Raman spectroscopy research and future development trends to further develop Raman spectroscopy and its applications.

Optical Imaging Approaches to Investigating Radiation Resistance

Radiation therapy is frequently the first line of treatment for over 50% of cancer patients. While great advances have been made in improving treatment response rates and reducing damage to normal tissue, radiation resistance remains a persistent clinical problem. While hypoxia or a lack of tumor oxygenation has long been considered a key factor in causing treatment failure, recent evidence points to metabolic reprogramming under well-oxygenated conditions as a potential route to promoting radiation resistance. In this review, we present recent studies from our lab and others that use high-resolution optical imaging as well as clinical translational optical spectroscopy to shine light on the biological basis of radiation resistance. Two-photon microscopy of endogenous cellular metabolism has identified key changes in both mitochondrial structure and function that are specific to radiation-resistant cells and help promote cell survival in response to radiation. Optical spectroscopic approaches, such as diffuse reflectance and Raman spectroscopy have demonstrated functional and molecular differences between radiation-resistant and sensitive tumors in response to radiation. These studies have uncovered key changes in metabolic pathways and present a viable route to clinical translation of optical technologies to determine radiation resistance at a very early stage in the clinic.

Advanced Spectroelectrochemical Techniques to Study Electrode Interfaces Within Lithium-Ion and Lithium-Oxygen Batteries

Lithium battery technologies have revolutionized mobile energy storage, but improvements in the technology are still needed. Critical to delivering new light weight, high capacity, safe devices is an improved understanding of the dynamic processes occurring at the electrode-electrolyte interfaces. Therefore, alongside advances in materials there has been a parallel progression in advanced characterization methods. Herein, recent developments for operando spectro-electrochemical techniques centered on Raman, infrared, and sum frequency generation are described within the context of lithium-ion and non-aqueous lithium-oxygen battery research. In particular, shell-isolated nanoparticles for enhanced Raman spectroscopy (SHINERS), surface-enhanced infrared absorption spectroscopy (SEIRAS), and near-field infrared are explained and critically evaluated, and future opportunities discussed. The aim is to introduce the wider community to the developing range of methodologies and tools now available in the hope that it encourages greater usage across the sector.

Functionalized core–shell Ag@TiO2 nanoparticles for enhanced Raman spectroscopy: a sensitive detection method for Cu(ii) ions

A shell-isolated nanoparticle enhanced surface Raman technique for detection of copper(ii).

High-Performance SERS Substrate Based on Hierarchical 3D Cu Nanocrystals with Efficient Morphology Control

Cu nanocrystals of various shapes are synthesized via a universal, eco-friendly, and facile colloidal method on Al substrates using hexadecylamine (HDA) as a capping agent and glucose as a reductant. By tuning the concentration of the capping agent, hierarchical 3D Cu nanocrystals show pronounced surface-enhanced Raman scattering (SERS) through the concentrated hot spots at the sharp tips and gaps due to the unique 3D structure and the resulting plasmonic couplings. Intriguingly, 3D sword-shaped Cu crystals have the highest enhancement factor (EF) because of their relatively uniform size distribution and alignment. This work opens new pathways for efficiently realizing morphology control for Cu nanocrystals as highly efficient SERS platforms.

Phenolic acids induced growth of 3D ordered gold nanoshell composite array as sensitive SERS nanosensor for antioxidant capacity assay

A novel method based on surface-enhanced Raman scattering (SERS) was developed to estimate the reducing capacity of phenolic acids by using self-assembled three-dimensionally (3D) ordered gold nanoparticles (GNPs) precursor composite (SiO₂/GNPs) arrays as nanoprobes. In the present work, the 3D ordered SiO₂/GNPs arrays immersed in the growth solution containing different phenolic acids, the SiO₂/GNPs were enlarged to varying degrees. Phenolic acids with one or more phenolic hydroxyl groups served as reductants for the growth of GNPs. The enlargement conditions varied with the different reducing capacity of phenolic acids, exhibiting specific morphologies differ from the complete gold nanoshells (GNSs). Consequently, the UV-vis spectra and SERS spectra for the phenolic acid-treated SiO₂/GNPs arrays were gradually changed. The change of the intensities of the SERS spectra correlated well with phenolic acids concentration which indicated that this SiO₂/GNPs array is a suitable SERS nanoprobe for phenolic acids. Results showed that the higher reducing capacity of phenolic acid, the stronger SERS of the enlarged GNSs. Thus, the SERS results could be used to evaluate the antioxidant capacity of phenolic acids by utilizing 3D ordered SiO₂/GNPs arrays as nanoprobes. The results also indicated that the reducing capacity of these three phenolic acids was in the order gallic acid > syringic acid > vanillic acid. The detection ranges of vanillic acid, syringic acid and gallic acid were 10-250 µM, 10-110 µM and 5-55 µM, respectively.

Silica-Coated Plasmonic Metal Nanoparticles in Action

Hybrid colloids consisting of noble metal cores and metal oxide shells have been under intense investigation for over two decades and have driven progress in diverse research lines including sensing, medicine, catalysis, and photovoltaics. Consequently, plasmonic core-shell particles have come to play a vital role in a plethora of applications. Here, an overview is provided of recent developments in the design and utilization of the most successful class of such hybrid materials, silica-coated plasmonic metal nanoparticles. Besides summarizing common simple approaches to silica shell growth, special emphasis is put on advanced synthesis routes that either overcome typical limitations of classical methods, such as stability issues and undefined silica porosity, or grant access to particularly sophisticated nanostructures. Hereby, a description is given, how different types of silica can be used to provide noble metal particles with specific functionalities. Finally, applications of such nanocomposites in ultrasensitive analyte detection, theranostics, catalysts, and thin-film solar cells are reviewed.

Core-Shell Nanoparticle-Enhanced Raman Spectroscopy

Core-shell nanoparticles are at the leading edge of the hot research topics and offer a wide range of applications in optics, biomedicine, environmental science, materials, catalysis, energy, and so forth, due to their excellent properties such as versatility, tunability, and stability. They have attracted enormous interest attributed to their dramatically tunable physicochemical features. Plasmonic core-shell nanomaterials are extensively used in surface-enhanced vibrational spectroscopies, in particular, surface-enhanced Raman spectroscopy (SERS), due to the unique localized surface plasmon resonance (LSPR) property. This review provides a comprehensive overview of core-shell nanoparticles in the context of fundamental and application aspects of SERS and discusses numerous classes of core-shell nanoparticles with their unique strategies and functions. Further, herein we also introduce the concept of shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) in detail because it overcomes the long-standing limitations of material and morphology generality encountered in traditional SERS. We then explain the SERS-enhancement mechanism with core-shell nanoparticles, as well as three generations of SERS hotspots for surface analysis of materials. To provide a clear view for readers, we summarize various approaches for the synthesis of core-shell nanoparticles and their applications in SERS, such as electrochemistry, bioanalysis, food safety, environmental safety, cultural heritage, materials, catalysis, and energy storage and conversion. Finally, we exemplify about the future developments in new core-shell nanomaterials with different functionalities for SERS and other surface-enhanced spectroscopies.

Uptake, Accumulation and Toxicity of Silver Nanoparticle in Autotrophic Plants, and Heterotrophic Microbes: A Concentric Review

Nanotechnology is a cutting-edge field of science with the potential to revolutionize today's technological advances including industrial applications. It is being utilized for the welfare of mankind; but at the same time, the unprecedented use and uncontrolled release of nanomaterials into the environment poses enormous threat to living organisms. Silver nanoparticles (AgNPs) are used in several industries and its continuous release may hamper many physiological and biochemical processes in the living organisms including autotrophs and heterotrophs. The present review gives a concentric know-how of the effects of AgNPs on the lower and higher autotrophic plants as well as on heterotrophic microbes so as to have better understanding of the differences in effects among these two groups. It also focuses on the mechanism of uptake, translocation, accumulation in the plants and microbes, and resulting toxicity as well as tolerance mechanisms by which these microorganisms are able to survive and reduce the effects of AgNPs. This review differentiates the impact of silver nanoparticles at various levels between autotrophs and heterotrophs and signifies the prevailing tolerance mechanisms. With this background, a comprehensive idea can be made with respect to the influence of AgNPs on lower and higher autotrophic plants together with heterotrophic microbes and new insights can be generated for the researchers to understand the toxicity and tolerance mechanisms of AgNPs in plants and microbes.

Exploring Morphological and Biochemical Linkages in Fungal Growth with Label-Free Light Sheet Microscopy and Raman Spectroscopy

Imaging tip growth in fungal hyphae is highly warranted to unravel the molecular mechanism of this extraordinarily precise and localized phenomenon. In situ probing of fungal cultures, however, have been challenging due to their inherent complexity and light penetration issues associated with conventional optical imaging. In this work, we report a label-free approach using a combination of light sheet microscopy and Raman spectroscopy to obtain concomitant morphological and biochemical information from the growing specimen. We show that the variance in morphology in the symbiotic fungus Piriformospora indica are rooted in the underlying differences in chemical composition in the specific growth zones. Our findings suggest that this potent two-pronged approach can comprehensively characterize growth areas and elucidate microbe interactions in still developing colonies with high sensitivity and multiplexing capability.

Cytochrome c-Capped Fluorescent Gold Nanoclusters: Imaging of Live Cells and Delivery of Cytochrome c

Cytochrome c-capped fluorescent gold nanoclusters (Au-NCs) are used for imaging of live lung and breast cells. Delivery of cytochrome c inside the cells is confirmed by covalently attaching a fluorophore (Alexa Fluor 594) to cytochrome c-capped Au-NCs and observing fluorescence from Alexa 594 inside the cell. Mass spectrometry studies suggest that in bulk water, addition of glutathione (GSH) to cytochrome c-capped Au-NCs results in the formation of glutathione-capped Au-NCs and free apo-cytochrome c. Thus glutathione displaces cytochrome c as a capping agent. Using confocal microscopy, the emission spectra and decay of Au-NCs are measured in live cells. From the position of the emission maximum it is shown that the Au-NCs exist as Au8 in bulk water and as Au13 inside the cells. Fluorescence resonance energy transfer from cytochrome c-Au-NC (donor) to Mitotracker Orange (acceptor) indicates that the Au-NCs localise in the mitochondria of live cells.