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A multimodal imaging platform can ascertain the spatial resolution and intracellular uptake of both the nanocarrier and drug as unique species.

A fundamental question crucial to surface-enhanced spatially offset Raman spectroscopy (SESORS) imaging and implementing it in a clinical setting for in vivo diagnostic purposes is whether a SESORS image can be used to determine the exact location of an object within tissue? To address this question, multiple experimental factors pertaining to the optical setup in imaging experiments using an in-house-built point-collection-based spatially offset Raman spectroscopy (SORS) system were investigated to determine those critical to the three-dimensional (3D) positioning capability of SESORS. Here, we report the effects of the spatial offset magnitude and geometry on locating nanoparticles (NPs) mixed with silica powder as an imaging target through tissue and outline experimental techniques to allow for the correct interpretation of SESORS images to ascertain the correct location of NPs in the two-dimensional x, y-imaging plane at depth. More specifically, the effect of "linear offset-induced image drag" is presented, which refers to a spatial distortion in SESORS images caused by the magnitude and direction of the linear offset and highlight the need for an annular SORS collection geometry during imaging to neutralize these asymmetric effects. Additionally, building on these principles, the concept of "ratiometric SESORS imaging" is introduced for the location of buried inclusions in three dimensions. Together these principles are vital in developing a methodology for the location of surface-enhanced Raman scattering-active inclusions in three dimensions. This approach utilizes the relationship between the magnitude of the spatial offset, the probed depth, and ratiometric analysis of the NP and tissue Raman intensities to ultimately image and spatially discriminate between two distinct NP flavors buried at different depths within a 3D model for the first time. This research demonstrates how to accurately identify multiple objects at depth in tissue and their location using SESORS which addresses a key capability in moving SESORS closer to use in biomedical applications.

The host-guest chemistry of coordination cages continues to promote significant interest, not least because confinement effects can be exploited for a range of applications, such as drug delivery, sensing, and catalysis. Often a fundamental analysis of noncovalent encapsulation is required to provide the necessary insight into the design of better functional systems. In this paper, we demonstrate the use of various techniques to probe the host-guest chemistry of a novel Pd2L4 cage, which we show is preorganized to selectively bind dicyanoarene guests with high affinity through hydrogen-bonding and other weak interactions. In addition, we exemplify the use of Raman spectroscopy as a tool for analyzing coordination cages, exploiting alkyne and nitrile reporter functional groups that are contained within the host and guest, respectively.

The rapid detection of biomolecules in a point of care (POC) setting is very important for diagnostic purposes. A platform which can provide this, whilst still being low cost and simple to use, is paper-based lateral flow immunoassays (LFIA). LFIA combine immunology and chromatography to detect a target by forming an immunocomplex with a label which traps them in a test zone. Qualitative analysis can be performed using the naked eye whilst quantitative analysis takes place by measuring the optical signal provided by the label at the test zone. There are numerous detection methods available; however, many suffer from low sensitivity and lack of multiplexing capabilities or are poor at providing POC quantitative analysis. An attractive method to overcome this is to use nanoparticles coated in Raman reporters as the labelled species and to analyse test zones using surface-enhanced Raman scattering (SERS). Due to the wide variety of metal nanoparticles, Raman reporter and laser excitations that are available, SERS-based LFIA have been adapted to identify and quantify multiple targets at once. Large Raman microscopes combined with long mapping times have limited the platform to the lab; however, by transferring the analysis to portable Raman instruments, rapid and quantitative measurements can be taken at the POC without any loss in sensitivity. Portable or handheld SERS-LFIA platforms can therefore be used anywhere, from modern clinics to remote and resource-poor settings. This review will present an overview of SERS-based LFIA platforms and the major recent advancements in multiplexing and portable and handheld detection with an outlook on the future of the platform. Graphical abstract

Vibrational spectroscopic chemical imaging is an important tool in the pharmaceutical industry for characterising the spatial distribution of components within final drug products. The applicability of these techniques is currently limited by the long data acquisition times required to obtain high-definition chemical images of a sample surface. Advancements in quantum cascade laser (QCL) technology have provided an exciting new opportunity for infrared (IR) imaging. Instead of collecting a full IR spectrum at each point, it is possible to focus on distinct spectral bands to reduce imaging data collection time. This study explores a laser direct infrared (LDIR) chemical imaging approach that couples QCL technology with rapid scanning optics to provide high-definition chemical images at an order of magnitude faster than traditional imaging techniques. The capabilities of LDIR chemical imaging were evaluated for pharmaceutical formulations and compared with other established spectroscopic chemical imaging techniques including Raman, near-infrared (NIR) and scanning electron microscopy-energy dispersive X-ray (SEM-EDX) spectroscopy with regards to data acquisition time and image quality. The study showed that LDIR imaging provided high-definition component distribution maps comparable to Raman and SEM-EDX at orders of magnitude faster in terms of time. The ability to obtain high-definition chemical images of the whole tablet surface in relatively fast time frames indicates LDIR imaging could be a promising tool in the pharmaceutical industry to rapidly characterise the size and distribution of components within tablets and could help enhance drug product manufacturing understanding.

Quantitative drug imaging in live cells is a major challenge in drug discovery and development. Many drug screening techniques are performed in solution, and therefore do not consider the impact of the complex cellular environment in their result. As such, important features of drug-cell interactions may be overlooked. In this study, Raman microscopy is used as a powerful technique for semi-quantitative imaging of Strathclyde-minor groove binders (S-MGBs) in mammalian cells under biocompatible imaging conditions. Raman imaging determined the influence of the tail group of two novel minor groove binders (S-MGB-528 and S-MGB-529) in mammalian cell models. These novel S-MGBs contained alkyne moieties which enabled analysis in the cell-silent region of the Raman spectrum. The intracellular uptake concentration, distribution and mechanism were evaluated as a function of the p

Statins have displayed significant, although heterogeneous, anti-tumour activity in breast cancer disease progression and recurrence. They offer promise as a class of drugs, normally used for cardiovascular disease control, that could have a significant impact on the treatment of cancer. Understanding their mode of action and accurately assessing their efficacy on live cancer cells is an important and significant challenge. Stimulated Raman scattering (SRS) microscopy is a powerful, label-free imaging technique that can rapidly characterise the biochemical responses of live cell populations following drug treatment. Here, we demonstrate multi-wavelength SRS imaging together with spectral phasor analysis to characterise a panel of breast cancer cell lines (MCF-7, SK-BR-3 and MDA-MB-231 cells) treated with two clinically relevant statins, atorvastatin and rosuvastatin. Label-free SRS imaging within the high wavenumber region of the Raman spectrum (2800-3050 cm -1) revealed the lipid droplet distribution throughout populations of live breast cancer cells using biocompatible imaging conditions. A spectral phasor analysis of the hyperspectral dataset enables rapid differentiation of discrete cellular compartments based on their intrinsic SRS characteristics. Applying the spectral phasor method to studying statin treated cells identified a lipid accumulating phenotype in cell populations which displayed the lowest sensitivity to statin treatment, whilst a weaker lipid accumulating phenotype was associated with a potent reduction in cell viability. This study provides an insight into potential resistance mechanisms of specific cancer cells towards treatment with statins. Label-free SRS imaging provides a novel and innovative technique for phenotypic assessment of drug-induced effects across different cellular populations and enables effective analysis of drug-cell interactions at the subcellular scale.

The use of Raman spectroscopy to determine the radiation response of human glioma cells and how this response differs depending on the cell's position in the cell cycle.

Currently, more than 80 % of commercial supercapacitors utilize chemically synthesized carbon nanomaterials which are expensive and necessitates non-renewable resources. Employing renewable, environment friendly and naturally available biomass feedstock as precursor for producing carbon materials is a low-cost and sustainable way for designing the electrodes of supercapacitors. In the present study, high surface area hierarchical porous multilayered graphene-like carbon is obtained via room temperature sono-exfoliation of the activated carbon synthesized via simple and environmentally friendly hydrothermal carbonization and potassium bicarbonate activation of waste hazelnut shells as the precursor. The high surface area graphene-like carbon showed excellent electrochemical performance with specific capacitance of 320.9 F g-1 at 0.2 A g-1 current density and exceptional capacitance retention of 77.8 % at 2 A g-1 current density after 10000 cycles in 1 M Na2SO4 electrolyte. Moreover, flexible supercapacitors fabricated using sono-exfoliated graphene-like activated carbon coated stainless steel mesh electrodes and biopolymer gel electrolyte exhibits an outstanding energy density of 38.7 W h kg-1 and power density of 198.4 W kg-1. These results show that mechanically exfoliated graphene-like activated carbon derived from hazelnut shells exhibit superior electrochemical performance that can compete with other activated carbon materials used in energy storage devices for real time applications.

Antibiotic resistant bacteria constitute a global health threat. It is essential for healthcare professionals to prescribe the correct dose of an effective antibiotic to mitigate the bacterial infection in a timely manner to improve the therapeutic outcomes to the patient and prevent the dissemination of antibiotic resistance. To achieve this, there is a need to implement a rapid and ultra-sensitive clinical diagnosis to identify resistant bacterial strains and monitor the effect of antibiotics. In this review, we highlight the use of surface enhanced Raman scattering (SERS) as a powerful diagnostic technique for bacterial detection and evaluation. Initially, this is viewed through a lens covering why SERS can surpass other traditional techniques for bacterial diagnosis. This is followed by different SERS substrates design, detection strategies that have been used for various bacterial biomarkers, how SERS can be combined with other diagnostic platforms to improve its performance towards the bacterial detection and the application of SERS for antibiotic resistance diagnosis. Finally, the recent progress in SERS detection methods in the last decade for the "

The low-frequency (terahertz) vibrational spectroscopy of two chlorophyll species, Chl-𝑎 and one of its magnesium derivatives (Chl-Mg-Na), has been investigated experimentally. The combination of terahertz time-domain spectroscopy and Fourier transform infrared spectroscopy has enabled a broad frequency range to be covered (0.2 to 18 THz). For Chl-Mg-Na, the terahertz spectra show clear and well-marked features at 1.44, 1.64, and 1.83 THz dominated by intermolecular interactions. The frequency dependent refractive index and absorption coefficient of Chl-Mg-Na were determined using the Fit@TDS software. Below 1.0 THz, a refractive index of 2.09 was measured. In order to acquire further understanding of the observed vibrational modes, a detailed study of the temperature dependence of the line positions of the lowest modes in Chl-Mg-Na was performed. As the temperature is increased from 88 K to 298 K, the feature at 1.83 THz experiences a notable red shift of frequency and line shape broadening, whereas the feature at 1.44 THz shows little change. These results suggest that the 1.83 THz feature is dominated by intermolecular motions occurring over the crystalline unit cell of the Chl-Mg-Na molecular crystal. Finally, terahertz time-domain was used to acquire the spectra of an ornamental plant bearing yellow-green variegated leaves (ivy, Aureomarginata variety), the yellow sectors having lower chlorophyll content compared to green sectors. In dehydrated green tissue, the chlorophyll molecules showed well-marked intermolecular vibrational modes at 1.85 THz, indicating that chlorophyll molecules are prone to pack with an ordered molecular arrangement. These results demonstrate the potential application of THz spectroscopy in agricultural sciences.

Antibiotic resistant bacteria constitute a global health threat. It is essential for healthcare professionals to prescribe the correct dose of an effective antibiotic to mitigate the bacterial infection in a timely manner to improve the therapeutic outcomes to the patient and prevent the dissemination of antibiotic resistance. To achieve this, there is a need to implement a rapid and ultra-sensitive clinical diagnosis to identify resistant bacterial strains and monitor the effect of antibiotics. In this review, we highlight the use of surface enhanced Raman scattering (SERS) as a powerful diagnostic technique for bacterial detection and evaluation. Initially, this is viewed through a lens covering why SERS can surpass other traditional techniques for bacterial diagnosis. This is followed by different SERS substrates design, detection strategies that have been used for various bacterial biomarkers, how SERS can be combined with other diagnostic platforms to improve its performance towards the bacterial detection and the application of SERS for antibiotic resistance diagnosis. Finally, the recent progress in SERS detection methods in the last decade for the "Big 5" antibiotic resistant challenges as demonstrators of public health major threats is reviewed, namely: Methicillin-resistant Staphylococcus aureus (MRSA), Carbapenem-resistant Enterobacteriaceae (CRE) / Extended-spectrum beta-lactamases (ESBLs), Mycobacterium tuberculosis (TB), Vancomycin-resistant Enterococcus (VRE) and Neisseria Gonorrhoea (NG). This review provides a comprehensive view of the current state of the art with regard to using SERS for assessing antibiotic resistance with a future outlook on where the field go head in the coming years.

BACKGROUND AND AIMS: Liver graft quality is evaluated by visual inspection prior to transplantation, a process highly dependent on surgeon's experience. We present an objective, non-invasive, quantitative way of assessing liver quality in real time using Raman spectroscopy, a laser-based tool for analysing biomolecular composition.APPROACH AND RESULTS: A novel porcine model of donation after circulatory death (DCD) with normothermic regional perfusion (NRP) allowed assessment of liver quality pre-mortem, during warm ischemia (WI) and post-NRP. 10% of circulating blood volume was removed in half of experiments to simulate blood recovery for DCD heart removal. Left median lobe biopsies were obtained before circulatory arrest, after 45 min of WI and after two hours of NRP, and analysed using spontaneous Raman spectroscopy, stimulated Raman spectroscopy (SRS) and staining. Measurements were also taken in situ from the porcine liver using a handheld Raman spectrometer at these time points from left median and right lateral lobes. Raman microspectroscopy detected congestion during WI by measurement of the intrinsic Raman signal of haemoglobin in red blood cells (RBCs), eliminating the need for exogenous labels. Critically, this microvascular damage was not observed during WI when 10% of circulating blood was removed before cardiac arrest. Two hours of NRP effectively cleared RBCs from congested livers. Intact RBCs were visualised rapidly at high resolution using SRS. Optical properties of ischemic livers were significantly different to pre-ischemic and post-NRP livers as measured using a handheld Raman spectrometer.CONCLUSIONS: Raman spectroscopy is an effective tool for detecting microvascular damage which could assist the decision to use marginal livers for transplantation. Reducing the volume of circulating blood before circulatory arrest in DCD may help reduce microvascular damage.

Peptide fibre formation via molecular self-assembly is a key step in a range of cellular processes and increasingly considered as an approach to produce supramolecular biomaterials. We previously demonstrated the self-assembly of the tripeptide lysine-dityrosine (KYY) as a substrate for the formation of proton-conducting melanin-like materials. Point based Raman scattering is one of several techniques which were used to characterise the secondary structure of the KYY nanofibre but as is often the case with this type of fibre, the spectra are rather complex and in addition there were variations in intensity between samples making interpretation difficult. Using Raman mapping we show that, as a drop of KYY in solution dries, it self-assembles into two different fibre forms and the simpler spectra obtained for each are easier to interpret. The tyrosine amide marker bands, 852 and 828 cm −1, are present in both forms with similar intensities indicating the formation of a similar secondary structure in both forms with some stacking of the tyrosine rings. However, the tyrosine marker bands at 1614 and 1661 cm −1 vary considerably in intensity between the two forms. It is concluded that both forms consist of stacked polypeptide units joined by hydrogen bonds to form structures similar to β-sheet structures in longer peptides. There are other clear differences such the large intensity difference in the lysine side chain band at 1330 cm −1 and the relative intensities of the bands at 982 and 1034 cm −1. These differences are attributed to changes in the conformation of tyrosine side chains causing different electron withdrawing effects on the ring.

Stimulated Raman scattering (SRS) microscopy is a powerful technique for visualising the cellular uptake and distribution of drugs and small molecules in live cells under biocompatible imaging conditions. The use of bio-orthogonal groups within the drug molecule, including alkynes and nitriles, has enabled the direct detection of a plethora of bioactive molecules in a minimally perturbative fashion. Limited progress has been made towards real-time detection of drug uptake and distribution into live cells under physiological conditions, despite the accordant potential it presents for preclinical drug development. SRS microscopy has been applied to the study of cellular dynamics of the drug 7RH, which is a potent inhibitor of dicoidin domain receptor 1 (DDR1) and prevents cellular adhesion, proliferation and migration in vitro. The uptake of 7RH into a variety of mammalian cell models was shown to be independent of DDR1 expression. Using a perfusion chamber, the recurrent treatment of live cancer cells was achieved, enabling 7RH uptake to be visualised in real-time using SRS microscopy, after which the viability of the same cellular population was assessed using commercially available fluorescent markers in a multimodal imaging experiment. The effect of 7RH treatment in combination with the chemotherapeutic, cisplatin was investigated using sequential perfusion and time-lapse imaging in the same live cell population, to demonstrate the application of the approach. SRS microscopy also identified potent inhibition of cellular adhesion and migration in breast cancer cell models with increasing 7RH treatment concentrations, thus representing a novel read-out methodology for phenotypic assays of this kind. The direct assessment of drug–cell interactions under physiological conditions offers significant potential for the preclinical drug development process.

Inspired by the role of intracellular liquid-liquid phase separation (LLPS) in formation of membraneless organelles, there is great interest in developing dynamic compartments formed by LLPS of intrinsically disordered proteins (IDPs) or short peptides. However, the molecular mechanisms underlying the formation of biomolecular condensates have not been fully elucidated, rendering on-demand design of synthetic condensates with tailored physico-chemical functionalities a significant challenge. To address this need, here we design a library of LLPS-promoting peptide building blocks composed of various assembly domains. We show that the LLPS propensity, dynamics, and encapsulation efficiency of compartments can be tuned by changes to the peptide composition. Specifically, with the aid of Raman and NMR spectroscopy, we show that interactions between arginine and aromatic amino acids underlie droplet formation, and that both intra- and intermolecular interactions dictate droplet dynamics. The resulting sequence-structure-function correlation could support the future development of compartments for a variety of applications.

Hyperspectral stimulated Raman scattering (SRS) microscopy is a powerful imaging modality for the analysis of biological systems. Here, we report the application of k-means cluster analysis (KMCA) of multi-wavelength SRS images in the high-wavenumber region of the Raman spectrum as a robust and reliable method for the segmentation of cellular organelles based on the intrinsic SRS spectrum. KMCA has been applied to the study of the endogenous lipid biochemistry of prostate cancer and prostate healthy cell models, while the corresponding SRS spectrum of the lipid droplet (LD) cluster enabled direct comparison of their composition. The application of KMCA in visualizing the LD content of prostate cell models following the inhibition of de novo lipid synthesis (DNL) using the acetyl-coA carboxylase inhibitor, 5-(tetradecyloxy)-2-furoic acid (TOFA), is demonstrated. This method identified a reliance of prostate cancer cell models upon DNL for metabolic requirements, with a significant reduction in the cellular LD content after treatment with TOFA, which was not observed in normal prostate cell models. SRS imaging combined with KMCA is a robust method for investigating drug-cell interactions in a label-free manner.

Microbial surface attachment negatively impacts a wide range of devices from water purification membranes to biomedical implants. Mimics of antimicrobial peptides (AMPs) constituted from poly(N‐substituted glycine) „peptoids“ are of great interest as they resist proteolysis and can inhibit a wide spectrum of microbes. We investigate how terminal modification of a peptoid AMP‐mimic and its surface immobilization affect antimicrobial activity. We also demonstrate a convenient surface modification strategy for enabling alkyne–azide „click“ coupling on amino‐functionalized surfaces. Our results verified that the N‐ and C‐terminal peptoid structures are not required for antimicrobial activity. Moreover, our peptoid immobilization density and choice of PEG tether resulted in a „volumetric“ spatial separation between AMPs that, compared to past studies, enabled the highest AMP surface activity relative to bacterial attachment. Our analysis suggests the importance of spatial flexibility for membrane activity and that AMP separation may be a controlling parameter for optimizing surface anti‐biofouling., Efficient anti‐biofouling: We show that an archetypical antimicrobial peptoid could retain high activity even with terminal modifications. Immobilization by alkyne–azide „click“ coupling on one‐step modified amino‐surfaces was demonstrated. Appropriate spatial separation between immobilized peptoids, rather than increasing surface density, was found to promote both resistance against bacterial attachment and AMP surface activity.

Surface-enhanced Raman scattering (SERS) is a powerful and sensitive technique for the detection of fingerprint sig-nals of molecules and for the investigation of a series of surface chemical reactions. Many studies introduced quantita-tive applications of SERS in various fields and several SERS methods have been implemented for each specific applica- tion, ranging in performance characteristics, analytes used, instruments, and analytical matrices. In general, very few methods have been validated according to international guidelines. As a consequence, the application of SERS in high-ly- regulated environments is still considered risky and the perception of a poorly reproducible and insufficiently robust analytical technique has persistently retarded its routine implementation. Collaborative trials are a type of interlabora-tory study (ILS) frequently performed to ascertain the quality of a single analytical method. The idea of an ILS of quan- tification with SERS arose within the framework of Working Group 1 (WG1) of the COST Action BM1401 Ra-man4Clinics32 in an effort to overcome the problematic perception of quantitative SERS methods. Here we report the first interlaboratory SERS study ever conducted, involving 15 laboratories and 41 researchers. In this study we tried to define a methodology to assess the reproducibility and trueness of a quantitative SERS method, and to compare differ- ent methods. In our opinion, this is a first important step toward a “standardization” process of SERS protocols, not proposed by a single laboratory but by a larger community.

Despite the excellent surface-enhanced Raman scattering (SERS) activity, the poor chemical stability of Ag nanoparticles severely hinders their application as SERS substrates. In this paper, a two-step process was used to prepare highly sensitive and chemically stable Ag@Au hetero-architectures, in situ growth of Ag nanoparticles on a Si wafer followed by Au coating through ion sputtering. Owing to the chemical inertness of Au, the Ag@Au hetero-architecture substrates exhibited enhanced chemical stability compared to pure Ag nanoparticle substrates. In particular, the deposition of Au coatings could efficiently modulate the gap between the neighboring Ag nanoparticles and strengthen the surface plasmon coupling effect. As a consequence, the Ag@Au hetero-architecture substrates exhibited a higher SERS sensitivity than pure Ag nanoparticle substrates. Furthermore, a possible mechanism for the enhanced SERS sensitivity of the Ag@Au hetero-architecture substrates was proposed and discussed. The present work came up with an effective and facile way to tune SERS sensitivity and chemical stability of Ag nanoparticle substrate, and in the meantime, implied a promising SERS application in oxidative environments or biological systems. This journal is

Gold nanoparticles (AuNPs) are widely used in various applications such as cancer imaging and drug delivery. The functionalisation of AuNPs has been shown to affect their cellular internalisation, accumulation and targeting efficiency. The mechanism of cellular uptake of functionalised AuNPs by different cancer cells is not well understood. Therefore, a detailed understanding of the molecular processes is necessary to improve AuNPs for their selective uptake and fate in specific cellular systems. This knowledge can greatly help in designing nanotags with higher cellular uptake for more selective and specific targeting capabilities with less off-target effects. Here, we demonstrate for the first time a straightforward and non-destructive 3D surface enhanced Raman spectroscopy (SERS) imaging approach to track the cellular uptake and localisation of AuNPs functionalised with an anti-ERα (estrogen receptor alpha) antibody in MCF-7 ERα-positive human breast cancer cells under different conditions including temperature and dynamin inhibition. 3D SERS enabled information rich monitoring of the intracellular internalisation of the SERS nanotags. It was found that ERα-AuNPs were internalised by MCF-7 cells in a temperature-dependent manner suggesting an active endocytosis-dependent mechanism. 3D SERS cell mapping also indicated that the nanotags entered MCF-7 cells using dynamin dependent endocytosis, since dynamin inhibition resulted in the SERS signal being obtained from, or close to, the cell surface rather than inside the cells. Finally, ERα-AuNPs were found to enter MCF-7 cells using an ERα receptor-mediated endocytosis process. This study addresses the role of functionalisation of SERS nanotags in biological environments and highlights the benefits of using 3D SERS for the investigation of cellular uptake processes., Use of sensitive, non-destructive and straightforward 3D SERS for investigating the cellular uptake processes of functionalised nanotags in entire cell volume.

Military-grade explosives such as 2,4,6-trinitroluene (TNT) are still a major worldwide concern in terms of terror threat and environmental impact. The most common methods currently employed for the detection of explosives involve colorimetric tests, which are known to be rapid and portable; however, they often display false positives and lack sensitivity. Other methods used include ion mobility mass spectrometry, gas chromatography-mass spectrometry (GC-MS), and liquid chromatography-mass spectrometry (LC-MS), which despite producing more reliable results often require large, expensive instrumentation and specially trained staff. Here we demonstrate an alternative approach that utilizes the formation of a colored Janowsky complex with nitroaromatic explosives through reaction of the enolate ion of 3-mercapto-2-butanone. The colored complex is formed rapidly and can then be detected sensitively using surface-enhanced Raman scattering (SERS). We demonstrate that SERS can be used as a quick, sensitive, and selective technique for the detection of 2,4,6-trinitrotoluene (TNT), hexanitrostillbene (HNS), and 2,4,6-trinitrophenylmethylnitramine (tetryl) with a detection limit of 6.81 ng mL -1 achieved for TNT, 17.2 ng mL -1 for tetryl, and 135.1 ng mL -1 for HNS. This method of detection also requires minimal sample preparation, can be done in a solution-based format, and utilizes the same precursor reagents for complex formation with each of the explosives which can then be identified due to the specificity of the unique SERS response obtained. We demonstrate the ability to simultaneously identify three explosive compounds within a total analysis time of 10 min. This method of detection shows promise for the development of rapid and portable SERS-based assays which can be utilized in the field in order to achieve reliable and quantitative detection.

The use of surface enhanced Raman scattering (SERS) for the detection of DNA has significant potential in terms of sensitivity, multiplex target detection and robust signal detection from nanoparticles. Current methods are usually performed with short chain DNA fragments or require additional separation steps for detection of longer chain fragments. We present an integrated method for the rapid and sensitive detection of extended (≥100-base) nucleic acids with reduced preparation and sample separation steps. Key to this is the DNA sequence-specific assembly of silver nanoparticles labelled with a Raman tag to provide an enhanced signal from the tag and hence molecular recognition of the target DNA. DNA probe orientation and hybridisation procedures are critical for the success of this assay. Effective detection of extended nucleic acids was achieved with head-to-head probes and by adding polyethylene glycol 10 000 (PEG 10 000) to the hybridisation buffer. This gave a 34-fold discriminatory enhancement factor when applied to a synthetic target. A structured approach toward maximising hybridisation procedures and SERS response is described, followed by an initial demonstration of SERS detection of single-stranded DNA target amplified by asymmetric PCR which was used without further separation. This has implications for future developments in using SERS for DNA detection due to the new-found ability to integrate SERS with asymmetric PCR.

Vibrational spectroscopic chemical imaging is a powerful tool in the pharmaceutical industry to assess the spatial distribution of components within pharmaceutical samples. Recently, the combination of vibrational spectroscopic chemical mapping with serial sectioning has provided a means to visualise the three-dimensional (3D) structure of a tablet matrix. There are recognised knowledge gaps in current tablet manufacturing processes, particularly regarding the size, shape and distribution of components within the final drug product. The performance of pharmaceutical tablets is known to be primarily influenced by the physical and chemical properties of the formulation. Here, we describe the data processing methods required to extract quantitative domain size and spatial distribution statistics from 3D vibrational spectroscopic chemical images. This provides a means to quantitatively describe the microstructure of a tablet matrix and is a powerful tool to overcome knowledge gaps in current tablet manufacturing processes, optimising formulation development.

Russ Algar, Tim Albrecht, Karen Faulds and Jun-Jie Zhu introduce the Analyst themed collection on analytical nanoscience.

A model for the prediction of the depth of two 'flavours' of surface enhanced Raman scattering (SERS) active nanotags embedded within porcine tissue is demonstrated using ratiometric analysis. Using a handheld spatially offset Raman (SORS) instrument, SESORS signals could be detected from nanotags at depths down to 48 mm for the first time using a backscattering SORS geometry.

Terahertz time-domain spectroscopy has been used to investigate the vibrational spectra of polycrystalline sodium magnesium chlorophyllin - one of the natural derivatives of chlorophyll - over the temperature range 88 K–298 K. A number of well-resolved absorption peaks were observed in the frequency range 0.2–2.5 THz, which are interpreted as originating from mixed character of intramolecular and intermolecular vibration modes. As the temperature is increased, the observed absorption features resolve into broader peaks. The peak centered at 1.83 THz shifts towards higher frequencies, indicating that for this feature, significant intermolecular anharmonicity exist.

Raman spectroscopy is a non-invasive technique that allows specific chemical information to be obtained from various types of sample. The detailed molecular information that is present in Raman spectra permits monitoring of biochemical changes that occur in diseases, such as cancer, and can be used for the early detection and diagnosis of the disease, for monitoring treatment, and to distinguish between cancerous and non-cancerous biological samples. Several techniques have been developed to enhance the capabilities of Raman spectroscopy by improving detection sensitivity, reducing imaging times and increasing the potential applicability for in vivo analysis. The different Raman techniques each have their own advantages that can accommodate the alternative detection formats, allowing the techniques to be applied in several ways for the detection and diagnosis of cancer. This feature article discusses the various forms of Raman spectroscopy, how they have been applied for cancer detection, and the adaptation of the techniques towards their use for in vivo cancer detection and in clinical diagnostics. Despite the advances in Raman spectroscopy, the clinical application of the technique is still limited and certain challenges must be overcome to enable clinical translation. We provide an outlook on the future of the techniques in this area and what we believe is required to allow the potential of Raman spectroscopy to be achieved for clinical cancer diagnostics., This article discusses the use of various Raman spectroscopy techniques and how they have been applied to different methods of detection for the diagnosis of cancer and in monitoring cancer treatment, with an outlook on how they can progress into a clinical environment.

Human African Trypanosomiasis (HAT) has been responsible for several deadly epidemics throughout the 20th century, but a renewed commitment to disease control has significantly reduced new cases and motivated a target for the elimination of Trypanosoma brucei gambiense-HAT by 2030. However, the recent identification of latent human infections, and the detection of trypanosomes in extravascular tissues hidden from current diagnostic tools, such as the skin, has added new complexity to identifying infected individuals. New and improved diagnostic tests to detect Trypanosoma brucei infection by interrogating the skin are therefore needed. Recent advances have improved the cost, sensitivity and portability of Raman spectroscopy technology for non-invasive medical diagnostics, making it an attractive tool for gambiense-HAT detection. The aim of this work was to assess and develop a new non-invasive diagnostic method for T. brucei through Raman spectroscopy of the skin. Infections were performed in an established murine disease model using the animal-infective Trypanosoma brucei brucei subspecies. The skin of infected and matched control mice was scrutinized ex vivo using a confocal Raman microscope with 532 nm excitation and in situ at 785 nm excitation with a portable field-compatible instrument. Spectral evaluation and Principal Component Analysis confirmed discrimination of T. brucei-infected from uninfected tissue, and a characterisation of biochemical changes in lipids and proteins in parasite-infected skin indicated by prominent Raman peak intensities was performed. This study is the first to demonstrate the application of Raman spectroscopy for the detection of T. brucei by targeting the skin of the host. The technique has significant potential to discriminate between infected and non-infected tissue and could represent a unique, non-invasive diagnostic tool in the goal for elimination of gambiense-HAT as well as for Animal African Trypanosomiasis (AAT)., Author summary Human African Trypanosomiasis (HAT), also known as sleeping sickness, is a disease caused by the parasite Trypanosoma brucei and has been responsible for the death of millions of people across Africa in the 20th century. It is also a major economic burden for countries endemic for trypanosomiasis, affecting livestock productivity in rural areas (Animal African Trypanosomiasis). A long-term international collaboration with the help of the World Health Organisation has resulted in the rate of human infection decreasing to less than 1000 new cases per year. However, the human disease continues to spread within remote villages. Current diagnosis is based on the detection of parasites in blood and serum samples, but this is challenging during chronic human infections with low or non-detectable parasitaemia. However, the recent discovery of extravascular skin-dwelling trypanosomes indicates that a reservoir of infection remains undetected, threatening the effort to eliminate the disease. In this study we have targeted the skin as a site for diagnosis using Raman spectroscopy and demonstrate that this method showed great promise in the laboratory, laying the foundation for field studies to examine its potential to strengthen current diagnostic strategies for detecting HAT cases.

Mitochondrial pH (pHmito) is intimately related to mitochondrial function, and aberrant values for pHmito are linked to several disease states. We report the design, synthesis, and application of mitokyne 1-the first small molecule pHmito sensor for stimulated Raman scattering (SRS) microscopy. This ratiometric probe can determine subtle changes in pHmito in response to external stimuli and the inhibition of both the electron transport chain and ATP synthase with small molecule inhibitors. In addition, 1 was also used to monitor mitochondrial dynamics in a time-resolved manner with subcellular spatial resolution during mitophagy providing a powerful tool for dissecting the molecular and cell biology of this critical organelle.

Surface enhanced Raman scattering (SERS) is a technique that demonstrates a number of advantages for the rapid, specific and sensitive detection of pathogenic microorganisms. In this review, an overview of label-free and label-based SERS approaches, including microfluidics, nucleic acid detection and immunoassays, for the multiplexed detection of pathogenic bacteria and viruses from the last decade will be discussed, as well as their transition into promising point-of-use detection technologies in industrial and medical settings., In this review we discuss surface enhanced Raman scattering (SERS) based techniques for the multiplexed detection of pathogenic microorganisms and their transition into point-of-use detection technologies in the field.

International audience; The terahertz absorption spectra of sodium magnesium chlorophyllin (Chl-Mg-Na) and sodium copper chlorophyllin (Cu-Chl), two major members of the chlorophyll derivative family, have been measured in the range 0.2−3.0 THz (6.6−100 cm-1), at room temperature. Additionally, surface-enhanced Raman scattering spectroscopy was used to supplement data in the higher frequency range. The capability of terahertz spectroscopy for quantitative characterization of Chl-Mg-Na intermolecular vibrations was investigated and the sensitivity of the 1.82-THz feature with degree of hydration by changes in the molecular environment was examined. For Cu-Chl derivative, a broad feature was observed around 1.8 THz which currently hinders clear Cu-Chl identification and quantification.

Clostridium difficile (C. diff) infection is one of the most contagious diseases associated with high morbidity and mortality rates in hospitalised patients. Accurate diagnosis can slow its spread by determining the most effective treatment. Herein, we report a novel testing platform as a proof-of-concept for the selective, sensitive, rapid and cost-effective diagnosis of C. diff infection (CDI) based on a duplex measurement. This was achieved by detecting two specific biomarkers, surface layer protein A (SlpA) and toxin B (ToxB), using a surface enhanced Raman scattering-based lateral flow assay (SERS-based LFA). The simultaneous duplex detection of SlpA with ToxB has not been described for the clinical diagnosis of CDI previously. The SlpA biomarker “AKDGSTKEDQLVDALA” was first reported by our group in 2018 as a species-specific identification tool. The second biomarker, ToxB, is the essential virulence biomarker of C. diff pathogenic strains and is required to confirm true infection pathogenicity. The proposed SERS-based LFA platform enabled rapid duplex detection of SlpA and ToxB on separate test lines using a duplex LF test strip within 20 minutes. The use of a handheld Raman spectrometer to scan test lines allowed for the highly sensitive quantitative detection of both biomarkers with a lowest observable concentration of 0.01 pg μL−1. The use of a handheld device in this SERS-based LFA instead of benchtop machine paves the way for rapid, selective, sensitive and cheap clinical evaluation of CDI at the point of care (POC) with minimal sample backlog.