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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.

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.

A new method is introduced for self-assembling citrate-capped gold nanoparticles into supraparticles with crystallographically aligned building blocks. It consists in confining gld nanoparticles inside a cellulose acetate membrane. The constituent nanoparticles are in close contact in the superstructure, and therefore generate hot spots leading to intense Surface-Enhanced Raman Scattering (SERS) signals. They also generate more plasmonic heat than the nanoparticle building blocks. The supraparticles are internalized by cells and show low cytotoxicity, but can kill cancer cells when irradiated with a laser. This, along with the improved plasmonic properties arising from their assembly, makes the gold supraparticles promising materials for applications in bioimaging and nanomedicine.

A novel electrochemical detection methodology is described for the femtomolar detection of proteins which utilizes both DNA aptamer-functionalized nanoparticles and a surface enzymatic reaction. Immunoglobulin E (IgE) was used as a model protein biomarker, which possesses two distinct epitopes for antibody (anti-IgE) and DNA aptamer binding. A surface sandwich assay format was utilized involving the specific adsorption of IgE onto a gold electrode surface that was pre-modified with a monolayer of aptamer-nanoparticle conjugates followed by the specific interaction of alkaline phosphatase (ALP) conjugated anti-IgE. To clearly demonstrate the signal enhancement associated with nanoparticle use, anodic current measurements of the ALP catalyzed oxidation of the enzyme substrate 4-aminophenylphosphate (APP) were also compared with electrode surfaces upon which the aptamer was directly attached. The detection of an unlabelled protein at concentrations as low as 5 fM is a significant improvement compared to conventional electrochemical-based immunoassay approaches and provides a foundation for the practical use and incorporation of nanoparticle-enhanced detection into electrochemical biosensing technologies.

The understanding of the relationship between plasmonic and surface-enhanced Raman scattering (SERS) properties of dynamic nanoparticle assemblies is of paramount importance for the optimal design of related plasmonic nanostructures, especially for SERS applications. In this regard, recent studies have provided new important insights for well-ordered nanoparticle assemblies but little is known about the relationship between the physical and optical properties for large ensembles of randomly aggregated metal nanoparticles in suspension, which still represents the simplest and most common route to obtain highly effective SERS substrates. Here we exploit the triplex-assembling ability of DNA-conjugated silver nanoparticles to engineer interparticle junctions with controlled interparticle distance and tune the aggregation rate to allow accurate investigation into the correlation between the averaged time-dependent plasmonic and SERS responses within a complex ensemble of nanoparticles in suspension. Solution-based single particle tracking was used to characterize the heterogeneity of the nanoparticle assembly with statistical reliability, acting as a key tool to unravel the connection between these two bulk responses. To achieve this, we report the first example of the parallel hybridization of dye-labeled locked nucleic acid (LNA) silver nanoparticle probes to double stranded DNA bridges of different lengths to form a triplex assembly, that provides SERS enhancements directly related to the interparticle distance imposed by the high structural rigidity of the double stranded linker. This is also a crucial step towards utilising SERS for the study of DNA in its natural double stranded state and, ultimately, to obtain nanoscale distance-dependent information in challenging biological environments using specially designed nanoparticles.

A new method is proposed for the fabrication of a well-defined size and shape distribution of silver nanoparticles in solution; the method employs direct laser irradiation of an aqueous solution containing a silver salt and a surfactant in the absence of reducing agents.

The controlled side-by-side assembly of gold nanorods in solution together with Raman reporter dye molecules to create small SERRS-active clusters stabilised by a surrounding polymer layer is demonstrated. This promising new class of nanotags offers several advantages over spherical nanoparticles for bioimaging and is of potential importance for a wide range of plasmon-enhanced spectroscopies and can also serve as building blocks for more complex solution-phase nanostructures.

This paper describes an ultrasensitive surface plasmon resonance (SPR) detection method using biofunctionalized gold nanorods for the direct detection of protein biomarkers. Immunoglobulin E (IgE), which has separate antibody and DNA aptamer binding sites, was chosen as a model protein for which a sandwich assay platform was designed. Detection was achieved via the specific adsorption of unlabelled IgE proteins onto the surface immobilized aptamer followed by the specific adsorption of anti-IgE coated gold nanorods (Au-NRs). Using the biofunctionalized nanorods in conjunction with SPR, we were able to directly measure IgE proteins at attomolar concentrations. This is a remarkable 10(8) enhancement compared to conventional SPR measurements of the same surface sandwich assay format 'anti-IgE/IgE/surface bound IgE-aptamer' in the absence of gold nanorod signal amplification.

The application of protein biomarkers as an aid for the detection and treatment of diseases has been subject to intensified interest in recent years. The quantitative assaying of protein biomarkers in easily obtainable biological fluids such as serum and urine offers the opportunity to improve patient care via earlier and more accurate diagnoses in a convenient, non-invasive manner as well as providing a potential route towards more individually targeted treatment. Essential to achieving progress in biomarker technology is the ability to screen large numbers of proteins simultaneously in a single experiment with high sensitivity and selectivity. In this article, we highlight recent progress in the use of microarrays for high-throughput biomarker profiling and discuss some of the challenges associated with these efforts.

This paper introduces a novel approach to surface bioaffinity sensing based on the adsorption of nanoparticles onto a gold diffraction grating that supports the excitation of planar surface plasmons. A surface enzymatic amplification reaction is also incorporated into the detection scheme to enhance the sensitivity and utility of the nanoparticle-enhanced diffraction grating (NEDG) sensors. As a demonstration, the detection of microRNA is described where a combination of a surface polymerase reaction and DNA-modified nanoparticles is used to detect the bioaffinity adsorption of the target onto the probe-functionalized gold grating surface. The enzymatically-amplified NEDG sensors possess a great potential for a wide range of applications including the detection of biosecurity agents, DNA and RNA viruses, biomarkers, and proteins.