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Optically detected magnetophoresis, using Boundary Element Method calculations, is exploited for characterizing the magnetic properties of low amounts of nanoparticles.

Surface-enhanced Raman scattering (SERS) has become a promising method for the detection of contaminants or biomolecules in aqueous media. The low interference of water, the unique spectral fingerprint, and the development of portable and handheld equipment for in situ measurements underpin its predominance among other spectroscopic techniques. Among the SERS nanoparticle substrates, those composed of plasmonic and magnetic components are prominent examples of versatility and efficiency. These substrates harness the ability to capture the target analyte, concentrate it, and generate unique hotspots for superior enhancement. Here, we have evaluated the use of gold-coated magnetite nanorods as a novel multifunctional magnetic-plasmonic SERS substrate. The nanostructures were synthesized starting from core-satellite structures. A series of variants with different degrees of Au coatings were then prepared by seed-mediated growth of gold, from core-satellite structures to core-shell with partial and complete shells. All of them were tested, using a portable Raman instrument, with the model molecule 4-mercaptobenzoic acid in colloidal suspension and after magnetic separation. Experimental results were compared with the boundary element method to establish the mechanism of Raman enhancement. The results show a quick magnetic separation of the nanoparticles and excellent Raman enhancement for all the nanoparticles both in dispersion and magnetically concentrated with limits of detection up to the nM range (∼50 nM) and a quantitative calibration curve. The nanostructures were then tested for the sensing of the antibiotic ciprofloxacin, highly relevant in preventing antibiotic contaminants in water reservoirs and drug monitoring, showing that ciprofloxacin can be detected using a portable Raman instrument at a concentration as low as 100 nM in a few minutes, which makes it highly relevant in practical point-of-care devices and in situ use.

Surface-enhanced Raman scattering (SERS) is an ideal technique for environmental and biomedical sensor devices due to not only the highly informative vibrational features but also to its ultrasensitive nature and possibilities toward quantitative assays. Moreover, in these areas, SERS is especially useful as water hinders most of the spectroscopic techniques such as those based on IR absorption. Despite its promising possibilities, most SERS substrates and technological frameworks for SERS detection are still restricted to research laboratories, mainly due to a lack of robust technologies and standardized protocols. We present herein the implementation of Janus magnetic/plasmonic Fe3O4/Au nanostars (JMNSs) as SERS colloidal substrates for the quantitative determination of several analytes. This multifunctional substrate enables the application of an external magnetic field for JMNSs retention at a specific position within a microfluidic channel, leading to additional amplification of the SERS signals. A microfluidic device was devised and 3D printed as a demonstration of cheap and fast production, with the potential for large-scale implementation. As low as 100 μL of sample was sufficient to obtain results in 30 min, and the chip could be reused for several cycles. To show the potential and versatility of the sensing system, JMNSs were exploited with the microfluidic device for the detection of several relevant analytes showing increasing analytical difficulty, including the comparative detection of p-mercaptobenzoic acid and crystal violet and the quantitative detection of the herbicide flumioxazin and the anticancer drug erlotinib in plasma, where calibration curves within diagnostic concentration intervals were obtained.

Raman spectroscopy is becoming increasingly popular as an in vitro bioimaging technique, when coupled with plasmonic substrates such as gold nanoparticles (AuNPs). Plasmonic AuNPs not only display excellent biocompatibility but can also induce the surface-enhanced Raman scattering (SERS) effect, which can be exploited for cell labeling, as an interesting alternative to fluorescence-based techniques. SERS bioimaging requires the use of so-called SERS tags or SERS-encoded AuNPs. A remaining difficulty toward the general implementation of this method is the difficulty to correlate the SERS signal (spectral intensity) with the number of SERS tags. Therefore, a general correlation method, suitable for arbitrary AuNP morphologies and Raman-active molecules (Raman reporters or RaRs), should largely improve the quantitative character of SERS as an imaging technique. We propose a protocol, with an associated app (SERSTEM), which enables the user to determine the average SERS intensity per nanoparticle from transmission electron microscopy (TEM) and SERS data. As a proof of concept, we demonstrated the method for Au nanostars and nanorods, carrying four different RaRs, and implemented the SERSTEM app, which is publicly available from an open-source platform.

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.

Anisotropic gold nanostructures are attracting attention due to the strong correlation between their shape and the localized surface plasmon resonances, which allows tuning their optical responses ...

10 Figuras, 2 Tablas, Graphene oxide nanoribbons (GONRs), obtained from the oxidative unzipping of carbon nanotubes, have been investigated as building blocks towards reaching active platforms in surface‐enhanced Raman scattering (SERS). The complete development of carbon nanomaterials is strongly related to the exploitation of their chemical versatility, so this work is focused on the positive effect that a specific chemical functionalization provides to the SERS effect when gold nanoparticles are used. The covalent derivatization of GONRs with terminal thiol groups boosts their interaction with different types of gold nanoparticles (namely, ‘naked’ or citrate‐stabilized), and the resulting two‐dimensional aggregates show an intense enhancement of the Raman scattering from the carbon nanostructures because of their two‐dimensional extended aggregation pattern. The SERS effect has been corroborated by theoretical calculations and a conceptual proof of SERS‐based sensing., AC, LL and MM would like to thank the University of Padova for funding (P‐DiSC #04BIRD2016‐UNIPD and the strategic program NAMECA). This project has received funding from the European Union's Horizon 2020 Research and Innovation Programme under the Marie Skłodowska‐Curie Grant Agreement n° 734834 (INFUSION) and from the PEOPLE Programme (Marie Curie Actions) of the European Union's Seventh Framework Programme FP7 Grant Agreement n°290023 (RADDEL).

Competitive reactions, on the surface of plasmonic nanostructures, allow exploiting SERS signals for quantitative Therapeutic Drug Monitoring. As an example, the concentration of Erlotinib, an anti-EGFR small molecule, used for the treatment of non-small cell lung and pancreatic cancer, is determined. The numerous side effects and the variability of patient responses make Erlotinib a good candidate for monitoring. The new SERS based sensor can estimate Erlotinib down to nanomolar concentration and is based on the chemical reaction of the drug and of a competitor SERS reporter on the surface of gold nanostructures. Colloid solutions of naked gold nanoparticles obtained by laser ablation in solution were used for obtaining nanostructures with very efficient hot spots for SERS and with a clean surface for chemistry. Detection of the drug in the nanomolar concentration range is shown to be possible also in spiked plasma samples.

The presence of non-hexagonal rings in the honeycomb carbon arrangement of graphene produces rippled graphene layers with valuable chemical and physical properties. In principle, a bottom-up approach to introducing distortion from planarity of a graphene sheet can be achieved by careful insertion of curved polyaromatic hydrocarbons during the growth of the lattice. Corannulene, the archetype of such non-planar polyaromatic hydrocarbons, can act as an ideal wrinkling motif in 2D carbon nanostructures. Herein we report an electrochemical bottom-up method to obtain egg-box shaped nanographene structures through a polycondensation of corannulene that produces a new conducting layered material. Characterization of this new polymeric material by electrochemistry, spectroscopy, electron microscopy (SEM and TEM), scanning probe microscopy, and laser desorption-ionization time of flight mass spectrometry provides strong evidence that the anodic polymerization of corannulene, combined with electrochemically induced oxidative cyclodehydrogenations (Scholl reactions), leads to polycorannulene with a wavy graphene-like structure., A bottom-up synthesis of wavy graphene structures obtained through an anodic polymerization process, combined with an electrochemically triggered oxidative cyclodehydrogenation, of the bowl-shaped polyaromatic hydrocarbon corannulene.

Liquid biopsy represents a new frontier of cancer diagnosis and prognosis, which allows the isolation of tumor cells released in the blood stream. The extremely low abundance of these cells needs appropriate methodologies for their identification and enumeration. Herein we present a new protocol based on surface enhanced resonance Raman scattering (SERRS) gold multivalent nanostructures to identify and enumerate tumor cells with epithelial and mesenchimal markers. The validation of the protocol is obtained with spiked samples of peripheral blood mononuclear cells (PBMC). Gold nanostructures are functionalized with SERRS labels and with antibodies to link the tumor cells. Three types of such nanosystems were simultaneously used and the protocol allows obtaining the identification of all individual tumor cells with the help of a Random Forest ensemble learning method.

Methods to image complex 3D cell cultures are limited by issues such as fluorophore photobleaching and decomposition, poor excitation light penetration, and lack of complementary techniques to verify the 3D structure. Although it remains insufficiently demonstrated, surface-enhanced Raman scattering (SERS) imaging is a promising tool for the characterization of biological complex systems. To this aim, a controllable 3D cell culture model which spans nearly 1 cm(2) in surface footprint is designed. This structure is composed of fibroblasts containing SERS-encoded nanoparticles (i.e., SERS tags), arranged in an alternating layered structure. This "sandwich" type structure allows monitoring of the SERS signals in the z-axis and with mm dimensions in the xy-axis. Taking advantage of correlative microscopy techniques such as electron microscopy, it is possible to corroborate nanoparticle positioning and distances in z-depths of up to 150 mu m. This study reveals a proof-of-concept method for detailed 3D SERS imaging of a complex, dense 3D cell culture model.

In this work we study the surface enhanced Raman scattering (SERS) produced by hierarchical nanostructures obtained by coupling different anisotropic nanomaterial of two SERS active metals, namely Ag nanostars (AgNSs) and Au nanowires (AuNWs). Ag nanostars (AgNSs) are prepared, by a two-step one-pot synthesis by reduction of AgNO3 with hydroxylamine, trisodium citrate and NaOH. AuNWs are obtained by electroless templated synthesis in track-etched polycarbonate membranes with following etching of the template. The two precursors are bound together by bridging with the bifunctional cysteamine molecule, obtaining AgNS@AuNW hierarchical structures. Benzenethiol (BT) is adsorbed on the nanostructured material and used as SERS probe to study the amplification of Raman signals. Experimental results indicate significantly larger Raman enhancement when BT is adsorbed onto the AgNS@AuNW in comparison to AuNWs alone or decorated with quasi-spherical silver nanoparticles obtaining AgNP@AuNW. Digital simulations performed by the boundary element method agree with the experimental findings, showing higher number of hot spots and significantly higher SERS enhancements for AgNS@AuNW versus AuNWs or AgNSs or AgNP@AuNW.

We demonstrate that the protonation chemistry of molecules adsorbed at nanometer distances from the surface of anisotropic gold nanoparticles can be manipulated through the effect of surface morphology on the local proton density of an organic coating. Direct evidence of this remarkable effect was obtained by monitoring surface-enhanced Raman scattering (SERS) from mercaptobenzoic acid and 4-aminobenzenethiol molecules adsorbed on gold nanostars. By smoothing the initially sharp nanostar tips through a mild thermal treatment, changes were induced on protonation of the molecules, which can be observed through changes in the measured SERS spectra. These results shed light on the local chemical environment near anisotropic colloidal nanoparticles and open an alternative avenue to actively control chemistry through surface morphology. LL and LML-M acknowledge funding from European Commission Grant (EUSMI 731019). Funding is also acknowledged from the Spanish MINECO (MAT2017-86659-R and MDM-2017-0720 to LML-M; MAT2017-88492-R and SEV2015-0522 to JGA) and the European Research Council (Advanced Grant 787510 4DBIOSERS to LML-M; Advanced Grant 789104-eNANO to JGA).

In the field of nanomaterials, multifunctional nanosystems play a prominent role in many applications as new magnetically recoverable catalysts, information processing, fuel cells, efficient bio/na...

The hydrophobic collapse is a structural transition of grafted polymer chains in a poor solvent. Although such a transition seems an intrinsic event during clustering of polymer-stabilized nanoparticles in the liquid phase, it has not been resolved in real time. In this work, we implemented a microfluidic 3D-flow-focusing mixing reactor equipped with real-time analytics, small-angle X-ray scattering (SAXS), and UV–vis–NIR spectroscopy to study the early stage of cluster formation for polystyrene-stabilized gold nanoparticles. The polymer shell dynamics obtained by in situ SAXS analysis and numerical simulation of the solvent composition allowed us to map the interaction energy between the particles at early state of solvent mixing, 30 ms behind the crossing point. We found that the rate of hydrophobic collapse depends on water concentration, ranging between 100 and 500 nm/s. Importantly, we confirmed that the polymer shell collapses prior to the commencement of clustering.

Early detection is the most effective mean of improving prognosis for many fatal diseases such as cancer. In this context, the Surface Enhanced Resonance Raman Scattering (SERRS) technique is being proposed as alternative to fluorescent methods in detection of biomarkers, because SERRS nanostructures are bright as fluorescent tags but more stable and clearly detectable using the narrow Raman “fingerprints” of a suitable reporter. Here we show that biocompatible SERRS active gold nanostructures, functionalized with an engineered PreS1 peptide (AuNP@PEG-PreS1), detect the presence of the SerpinB3 antigen overexpressed on liver tumor cells, a biomarker of the onset of liver cell carcinomatous transformation. A proper engineering of the targeting unit, linked to the nanostructure by a polymer chain, affords a sensitivity and specificity larger than 80%, at subnanomolar concentrations. Taking into account the high sensitivity of SERRS and that SB3 overexpression is an early event in liver cell carcinomatous transformation, AuNP@PEG-PreS1 nanostructures could be used in routine diagnostic activities, to improve the accuracy of HCC detection in particular in patients with chronic liver diseases.

Colloidal gold nanostructures are nowadays widely involved in sensor applications. One of the most interesting techniques that takes advantage of them is certainly the Surface Enhanced Raman Scattering (SERS) effect, even if it is often considered a tricky technique due to structural constraints required by the nanostructured substrates to obtain high enhancement factors (EFs), i.e. the presence of hot spots. Because of the easy preparation and high number of hot spots, aggregated gold nanospheres seem to be the most efficient through the SERS colloids, but their characteristic high disorder makes them unpredictable and difficult to compare between different batches. For this reason, less SERS effective, but more regular and organized substrates are usually preferred. In this study, a method based on Boundary Element Method (BEM) simulation is used to accurately predict the colloidal SERS EFs of gold nanoparticle (AuNP) aggregates, starting from their experimental extinction spectra. Surprisingly, it was found that larger aggregates do not exhibit stronger hot spots, but rather higher amounts of them, influencing the overall predicted EFs, which well reflect the results obtained experimentally.

Laser synthesis emerges as a suitable technique to produce ligand-free nanoparticles, alloys and functionalized nanomaterials for catalysis, imaging, biomedicine, energy and environmental applications. In the last decade, laser ablation and nanoparticle generation in liquids has proven to be a unique and efficient technique to generate, excite, fragment and conjugate a large variety of nanostructures in a scalable and clean way. In this work, we give an overview on the fundamentals of pulsed laser synthesis of nanocolloids and new information about its scalability towards selected applications. Biomedicine, catalysis and sensing are the application areas mainly discussed in this review, highlighting advantages of laser-synthesized nanoparticles for these types of applications and, once partially resolved, the limitations to the technique for large-scale applications.

Multimodal contrast agents offer new interesting diagnostic possibilities, summing the benefits of multiple imaging techniques. Magnetic resonance and optical imaging are complementary techniques. The first allows total body screening, even though it suffers from low spatial resolution and needs high loadings, whereas the second shows lower penetration, but bright signals, and a higher spatial resolution and needs lower loadings. We present a plasmonic nanosystem as a MRI (magnetic resonance imaging) and SERRS (surface enhanced resonance Raman scattering) multimodal contrast agent. Naked gold nanoparticles, obtained by laser ablation synthesis in solution, are organized as a highly efficient SERRS substrate with a naphthalocyanine reporter and functionalized with a MRI contrast agent with a newly synthesized 3DOTA-PEG polymer, with a high GdIII loading. As a proof of concept, in vivo and ex vivo MRI and SERRS experiments are also performed. The plasmonic property of the nanosystem is then exploited to show its usefulness for localized hyperthermia.

Magneto-plasmonic nanostructures functionalized with cell targeting units are of great interest for nanobiotechnology applications. Photothermal treatment of cells targeted with antibody functionalized nanostructures and followed by magnetic isolation, allows killing selected cells and hence is one of the applications of great interest. The magneto-plasmonic nanostructures reported herein were synthesized using naked gold and magnetite nanoparticles obtained through a green approach based on laser ablation of bulk materials in water. These particles do not need purifications steps for biocompatibility and are functionalized with a SERRS (surface enhanced resonance Raman scattering) active molecule for detection and with an antibody for targeting prostate tumor cells. Quantitative results for the cell targeting and selection efficiency show an overall accuracy of 94% at picomolar concentrations. The photothermal treatment efficiently kills targeted and magneto-selected cells producing a viability below 5% after 3 min of irradiation, compared with almost 100% viability of incubated and irradiated, but non targeted cells.

A major challenge in cancer treatment is the quantification of biomarkers associated with a specific cancer type. Important biomarkers are the circulating tumor cells (CTCs) detached from the main cancer and circulating in the blood. CTCs are very rare and their identification is still an issue. Although CTCs quantification can be estimated by using fluorescent markers, all the fluorescence techniques are strongly limited by the number of emissions (therefore markers) that can be discriminated with one exciting line, by their bleaching characteristics, and by the intrinsic autofluorescence of biological samples. An emerging technique that can overcome these limitations is Surface Enhanced Raman Scattering (SERS). Signals of vibrational origin with intensity similar to those of fluorescence, but narrower bandwidths, can be easily discriminated even by exciting with a single laser line. We recently showed the benefit of this method with cells fixed on a surface. However, this approach is too demanding to be applied in clinical routine. To effectively increase the throughput of the SERS analysis, microfluidics represents a promising tool. We report two different hydrodynamic strategies, based on device geometry and liquids viscosity, to successfully combine a microfluidic design with SERS.

Plasmonic nanostructures show important properties for biotechnological applications, but they have to be guided on the target for exploiting their potentialities. Antibodies are the natural molecules for targeting. However, their possible adverse immunogenic activity and their cost have suggested finding other valid substitutes. Small molecules like peptides can be an alternative source of targeting agents, even if, as single molecules, their binding affinity is usually not very good. GE11 is a small dodecapeptide with specific binding to the epidermal growth factor receptor (EGFR) and low immunogenicity. The present work shows that thousands of polyethylene glycol (PEG) chains modified with lysines and functionalized with GE11 on clusters of naked gold nanoparticles, obtained by laser ablation in water, achieves a better targeting activity than that recorded with nanoparticles decorated with the specific anti-EGFR antibody Cetuximab (C225). The insertion of the cationic spacer between the polymeric part of the ligand and the targeting peptide allows for a proper presentation of GE11 on the surface of the nanosystems. Surface enhanced resonance Raman scattering signals of the plasmonic gold nanoparticles are used for quantifying the targeting activity. Molecular dynamic calculations suggest that subtle differences in the exposition of the peptide on the PEG sea are important for the targeting activity.

The present research is focused on the setting up of an advanced analytical system for the detection of synthetic dyes. The system is based on the combination of an innovative thin layer chromatography (TLC) plate coupled with enhanced infrared (MU-ATR, metal underlayer attenuated total reflection) and Surface Enhanced Raman (SERS) spectroscopy. In particular, a TLC plate made of silver iodide (AgI) applied onto a gold coated glass slide (AgI@Au) is proposed as an efficient stationary phase for the separation of dyes mixtures. The separated dyes are then identified by means of both enhanced FTIR and SERS, performed directly on the same eluted spots. The use of a mid-IR transparent inorganic salt as stationary phase coupled with the underneath gold layer avoids spectral interferences, enhancing the signal obtained from ATR analyses. At the same time, SERS spectra can be recorded as the TLC plate may act as a SERS active substrate due to the photoreduction of AgI to metallic Ag caused by the exposure to the laser during the Raman analysis. Different mixtures of synthetic dyes of known composition, widely used in dyeing processes, have been tested and the method resulted to be effective in identifying trace amounts in the order of tens nanograms. Moreover, the method has been further evaluated on a real case study represented by dyes extracted from dyed wool.

Zoe Pikramenou, Catriona McCallion, Sara Carreira, Peter Dobson, Katherine Brown, Yuri Antonio Diaz Fernandez, Maha Abdollah, Dejian Zhou, Dan Sun, Sandhya Moise, Lucio Litti, Lanry L. Yung, Stefan Borsley, Nadiya Dragneva, Annette Barchanski, Mostafa El-Sayed, Amelie Heuer-Jungemann, Roger M. Pallares, Edman Tsang, Nicolas Barry, Scott Mitchell, Nguyen T. K. Thanh, Maya Thanou, Ivan Parkin, Paresh Ray and Richard Jones

Ultrasensitive detection of low-quantity drugs is important for personalized therapeutic approaches in several diseases and, in particular, for cancer treatment. In this field, surface-enhanced Raman scattering (SERS) can be very useful for its ability to precisely identify analytes from their unique vibrational spectra, with very high sensitivity. Here, we report a study about SERS detection of sunitinib, paclitaxel and irinotecan, i.e. three commonly used antineoplastic drugs, and of SN-38, i.e. the metabolite of irinotecan, dissolved in methanol solutions. By using commercial Klarite substrates, we found that sunitinib, irinotecan and SN-38 have detection limits of 20–70 ng, which is below the threshold for applications in cancer therapy. Conversely, the SERS signal was not appreciable with paclitaxel, and this is explained by the absence of optical resonances in the visible range. Overall, our results show that ultrasensitive SERS detection of sunitinib, irinotecan and SN-38 is feasible, encouraging further development of this technology also for other drugs with similar molecular structure especially for those analytes with absorption bands in the visible range.

In the field of analytical chemistry, many scientific efforts have been devoted to develop experimental procedures for the characterization of organic substances present in heterogeneous artwork samples, due to their challenging identification. In particular, performances of immunochemical techniques have been recently investigated, optimizing ad hoc systems for the identification of proteins. Among all the different immunochemical approaches, the use of metal nanoparticles - for surface enhanced Raman scattering (SERS) detection - remains one of the most powerful methods that has still not been explored enough for the analysis of artistic artefacts. For this reason, the present research work was aimed at proposing a new optimized and highly efficient indirect immunoassay for the detection of ovalbumin. In particular, the study proposed a new SERRS probe composed of gold nanoparticles (AuNPs) functionalised with Nile Blue A and produced with an excellent green and cheap alternative approach to the traditional chemical nanoparticles synthesis: the laser ablation synthesis in solution (LASiS). This procedure allows us to obtain stable nanoparticles which can be easily functionalized without any ligand exchange reaction or extensive purification procedures. Moreover, the present research work also focused on the development of a comprehensive analytical approach, based on the combination of potentialities of immunochemical methods and Raman analysis, for the simultaneous identification of the target protein and the different organic and inorganic substances present in the paint matrix. An advanced mapping detection system was proposed to achieve the exact spatial location of all the components through the creation of false colour chemical maps.

Peter Dobson, Lanry L. Yung, Liane Rossi, Sara Carreira, Paresh Ray, Catherine Amiens, Katherine Brown, Dejian Zhou, Asterios Gavriilidis, Nguyen T. K. Thanh, Sandhya Moise, Lucio Litti, Hedi Mattoussi, Matthew Todd, Scott Mitchell, Stefan Borsley, Amelie Heuer-Jungemann, Oliver Reiser, Edman Tsang, Maya Thanou, Tom Berkleman, Dalibor Soukup, Kerry Chester, Ivan Parkin, Yuri Antonio Diaz Fernandez and Benjamin P. Burke

The analysis of dyes in cultural heritage samples is a well-known challenging task, due to their inherent high tinting strength and consequent low concentration in the carrying matrix a fact that severely limits the number of analytical techniques that can be efficiently and micro-destructively employed for their detection and unambiguous identification. In the present study, an advanced and alternative SEIRA based analytical protocol for the analysis of small quantities of synthetic colorants has been proposed. The method has been set up for the identification of Acid Orange 7 (AO7) using Au nanoparticles obtained by laser ablation in solution (LASiS). Analyses have been performed applying a drop containing a mixture between the colorant and the Au colloidal solution in its unaggregated state on a gold coated glass slide for RAS (Reflection Absorption Spectroscopy) analysis. The first results showed that, thanks to the enhancement produced by the nanoparticles, it is possible to analyze small amount of diluted solutions containing the colorant. Thus, the method has been successfully applied for the analysis of few pieces of dyed wool, after the development of a suitable micro extraction procedure.

Diagnostic approaches based on multimodal imaging are needed for accurate selection of the therapeutic regimens in several diseases, although the dose of administered contrast drugs must be reduced to minimize side effects. Therefore, large efforts are deployed in the development of multimodal contrast agents (MCAs) that permit the complementary visualization of the same diseased area with different sensitivity and different spatial resolution by applying multiple diagnostic techniques. Ideally, MCAs should also allow imaging of diseased tissues with high spatial resolution during surgical interventions. Here a new system based on multifunctional Au-Fe alloy nanoparticles designed to satisfy the main requirements of an ideal MCA is reported and their biocompatibility and imaging capability are described. The MCAs show easy and versatile surface conjugation with thiolated molecules, magnetic resonance imaging (MRI) and computed X-ray tomography (CT) signals for anatomical and physiological information (i.e., diagnostic and prognostic imaging), large Raman signals amplified by surface enhanced Raman scattering (SERS) for high sensitivity and high resolution intrasurgical imaging, biocompatibility, exploitability for in vivo use and capability of selective accumulation in tumors by enhanced permeability and retention effect. Taken together, these results show that Au-Fe nanoalloys are excellent candidates as multimodal MRI-CT-SERS imaging agents.

Gold nanoparticles (AuNPs) assisted laser desorption ionization mass spectrometry (LDI-MS) emerged as an effective technique for the detection of analytes with high sensitivity. The surface chemistry and the size of AuNPs are the crucial parameters for lowering the detection limits and increasing the selectivity of LDI-MS. Here we show that chemical-free size selected AuNPs, obtained by laser ablation synthesis in solution (LASiS), have very low background in the low mass region (