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Surface-enhanced Raman spectroscopy has demonstrated its ability as powerful tool that can provide us information about the structure and the conformation of molecules such as DNA. In this work, we used an Hamamatsu commercial SERS substrate [1], to study the interaction between a DNA sequence consisting of 20 Bases of poly-Thymin (PolyT) with its complementary poly-Adenin (PolyA). The PolyA strand is grafted at the surface of the gold nanostructured surface using a thiol group at the 5' extremity of the DNA strand. the SERS substrate is incubated in 450 µl of PolyA (10-4 M) in TE buffer for 15 hours. The surface is then washed to remove the PolyA excess. We assume that we form a monolayer of PolyA. Some solutions of PolyT with different concentrations (10-7, 10-6, 10-5 and 10-4 M) are successively deposited on the SERS substrate. We performed Raman mapping on the surface and we recorded 400 spectra using a 633 nm excitation wavelength. One can observe the 735 cm-1 band assigned to the ring breathing mode of the PolyA and some variations of its intensity depending on the position on the map. By changing the concentration, we observe a decrease of the average SERS intensity of this band as well as a decrease of the standard deviation of the intensity of this band. We interpret this intensity change by some modification of the orientation and flexibility of the PolyA DNA strands interacting with the PolyT [2]. The increase of the concentration of Poly-T induced a loss of flexibility of the PolyT/PolyA molecular complex. This study provides a new approach for the reliable quantification and structural analysis of biological molecules.

Circulating tumor cells (CTCs) can be used as important biomarkers to reflect the progress and malignancy of tumors. However, current CTC detection technologies have some limitations for clinical applications due to their complexity, low specificity and high cost. Herein, we develop a terahertz anti-resonance hollow core fiber (THz AR-HCF) biosensor for CTC detection. Through simulation and experiment comparisons, the low-loss property of the THz AR-HCF is verified, and a suitable fiber is selected for biosensing applications. By measuring different cell numbers and different types of cancer cells, a good linear relationship between THz transmittance and the numbers of cells between 10 and 106 was found. Meanwhile, different types of tumor cells can be distinguished by comparing THz transmission spectra, indicating that the biosensor has high sensitivity and specificity for CTC detection. The biosensor only required a small amount of sample, as low as 100 μl, and enables label-free and nondestructive quantitative detection. Flow cytometry results showed that the cell viability was as high as 98.5±0.26% after whole assay process and there was no statistically significant difference compared with the negative control. This study demonstrated that the proposed THz AR-HCF has great potential for highly sensitive, label-free and nondestructive detection of CTCs in clinical samples.

Logistic regression (LR) is a supervised multiple linear regression model, which uses linear weighted calculation for input to obtain weight coefficients of model. The surface enhanced Raman spectroscopy (SERS) technology greatly enhances the Raman signal of analyte. LR model was used to analyze the data of seven types of pancreatic cancer-related miRNAs obtained from commercial SERS substrate. The classification ability of the model on such data was observed under the configurations of different key parameters (classification mode, regularization method and loss function optimization way), and the effect of the two types of data formats were also evaluated. The results showed that though LR model used to classify this data did not perform well as expected, miRNA-191 and miRNA-4306 still had high recalls (sensitivity), which laid a theoretical foundation for the purpose of using LR model to identify these two miRNAs to jointly diagnose of pancreatic cancer at miRNA level.

Gold colloidal nanoparticles (NPs) were functionalized in acetonitrile with a Cu(I) complex consisting of one 2,2′-bipyridine ligand possessing a lipoic acid moiety and one 2,9-dimesitylene-1,10-ph...

The dipolar approximation model that describes the heat delivered by a nanoparticle under continuous light irradiation provides a relation in which the dissipated power is proportional to the extinction cross-section. This relation works fairly well for small particles in which all the energy is absorbed, but fails for larger structures due to the non-negligible power scattered in the free space that does not contribute to heat generation. Here we show that, if we consider the light-induced dipolar field in the calculation of the dissipated power, we recover the proportionality with the absorption cross-section of the nanoparticle.

Sensitive and specific detection of microRNAs (miRNAs) is of critical significance for early diagnosis of cancers such as pancreatic cancer with atypical initial symptoms and high mortality. Despite exponential amplification reaction (EXPAR) is an attractive isothermal amplification method for detecting miRNAs, it faces the problems of the dependence difference and low specificity. To address such challenges, herein, a nicking-assisted entropy-driven DNA circuit triggered exponential amplification reaction (NAED-EXPAR) was firstly employed for ultrasensitive and specific detection of miRNA in "one-pot" manner at constant temperature. Nicking-assisted entropy-driven DNA circuit can specifically recognize the target miRNA, leading to continuous disassembly of DNA substrates via intramolecular toehold-mediated branch migration. During the reaction, the catalytic circuit can consume excess fuel DNA strands to produce a large number of primers. Then the newly formed primers can trigger EXPAR for highly efficient signal amplification. Mechanism analysis shows that the amplification efficiency of NAED-EXPAR is superior than that of single EXPAR. For miR-21, the detection limit of NAED-EXPAR can reach 100 aM, which is at least five orders of magnitude higher than the standard EXPAR that directly uses the target as primer. NAED-EXPAR shows improved specificity for identifying single nucleotide variations and enables sensitive and accurate analysis of miR-21 in human cancer cell lines. This method is expected to offer a new approach for the reliable quantification of miRNAs in complex biological matrices and provide valuable information for early cancer diagnosis.

International audience; Green LED plasmon excitation (525 nm) of colloidal gold nanoparticles (NPs), onto which a copper(ii) complex was grafted, in the presence of nitrobenzaldehyde and nitromethane in DMF lead to the formation of the corresponding nitroaldol with high efficiency. Kinetic studies using H-1 NMR and Raman spectroscopies showed that the reaction was faster under irradiation with green light, especially when in close proximity to the NPs (ca. 100% conversion after 100 min). After reaction completion, it was possible to recover the nanocatalyst and run two subsequent reactions. Green LED excitation of plasmonic nanocatalyst is shown to be a straightforward and efficient method for accelerating the rate of the Henry reaction with a lower energy demand and over a shorter reaction time when compared to the reaction performed under classical conditions.

Tire and Road Wear Particles (TRWP) are non-exhaust particulate matter generated by road transport means during the mechanical abrasion of tires, brakes and roads. TRWP accumulate on the roadsides and are transported into the aquatic ecosystem during stormwater runoffs. Due to their size (sub-millimetric) and rubber content (elastomers), TRWP are considered microplastics (MPs). While the amount of the MPs polluting the water ecosystem with sizes from ~ 5 μm to more than 100 μm is known, the fraction of smaller particles is unknown due to the technological gap in the detection and analysis of < 5 μm MPs. Here we show that Raman Tweezers, a combination of optical tweezers and Raman spectroscopy, can be used to trap and chemically analyze individual TWRPs in a liquid environment, down to the sub-micrometric scale. Using tire particles mechanically grinded from aged car tires in water solutions, we show that it is possible to optically trap individual sub-micron particles, in a so-called 2D trapping configuration, and acquire their Raman spectrum in few tens of seconds. The analysis is then extended to samples collected from a brake test platform, where we highlight the presence of sub-micrometric agglomerates of rubber and brake debris, thanks to the presence of additional spectral features other than carbon. Our results show the potential of Raman Tweezers in environmental pollution analysis and highlight the formation of nanosized TRWP during wear.

We report on the use of Raman Tweezers, a combination of Optical Tweezers and Raman Spectroscopy, for the detection and chemical identification of nanometric particles of plastics and car tires fragments dispersed in water, at the single particle level.

International audience; We study the interaction between one aptamer and its analyte (the MnSOD protein) by the combination of surface-enhanced Raman scattering and multivariate statistical analysis. We observe the aptamer structure and its evolution during the interaction under different experimental conditions (in air or in buffer). Through the spectral treatment by principal component analysis of a large set of SERS data, we were able to probe the aptamer conformations and orientations relative to the surface assuming that the in-plane nucleoside modes are selectively enhanced. We demonstrate that the aptamer orientation and thus its flexibility rely strongly on the presence of a spacer of 15 thymines and on the experimental conditions with the aptamer lying on the surface in air and standing in the buffer. We reveal for the first time that the interaction with MnSOD induces a large loss of flexibility and freezes the aptamer structure in a single conformation.

Correction for ‘CTL–doxorubicin (DOX)–gold complex nanoparticles (DOX–AuGCs): from synthesis to enhancement of therapeutic effect on liver cancer model’ by Qiqian Liu et al., Nanoscale Adv., 2020, 2, 5231–5241. https://doi.org/10.1039/D0NA00758G.

Based on high sensitivity, specific fingerprinting spectra and real-time detection, surface-enhanced Raman spectroscopy (SERS) is a powerful tool for the observation, the detection and the identification of chemical or biological species at low concentrations. One of the key elements for the SERS detection is the choice of SERS substrate. This latter one can be either a home-made one or either commercially purchased. For researchers who don’t have facilities to fabricate SERS substrates, the commercial ones are a necessary and optimal choice. Thus, a comprehensive evaluation of their reproducibility is urgently needed and carried out in this paper. The blank spectra as well as the SERS spectra of three probes molecules (4-mercaptobenzoic acid (4-MBA), 1, 2-bis (4-pyridyl) ethylene (BPE) and methylene blue (MB)) were analysed for two excitation wavelengths (532 and 785 nm). The most suitable detection condition was determined for each substrate. Under the optimum conditions, the SERS mapping were carried to measure the relative standard deviations (RSDs) to further evaluate the reproducibility of the substrates. The results demonstrated that the Enspectrc, Q-SERSTM and Hamamatsu substrates were the more suitable for reproducible SERS measurements.

Deoxyribonucleic acid (DNA) detection is essential for the accurate and early diagnosis of a disease. In this study, a femtomolar DNA detection method based on the exploitation of the localized surface plasmon (LSP) resonance of gold nanoparticles (AuNPs) was developed. We prepared Poly Ethylen Glycol (PEG) functionalized AuNPs with a specific DNA capture probe (CP) directly modified on the gold surface. Two strategies are proposed using different kinds of CP to detect the target DNA (tDNA). In the first strategy, CP is the complementary of the complete sequence of the DNA (CCP method). For the second strategy, we used two CPs, which were half complementary to tDNA, and these were hybridized with tDNA to form sandwich structures (MIX method). The results showed that our detection methods are highly sensitive and that the limits of detection of 124 am and 2.54 fm tDNA can be reached when using the CCP and MIX methods, respectively. In addition, the specificity of our two strategies is also demonstrated with mismatched DNAs. The proposed method provides a simple, fast, sensitive and specific DNA biosensor, which has the potential to be used for point-of-care tests (POCT).

Large protein complexes carry out some of the most complex activities in biology1,2. Such structures are often assembled spontaneously through the process of self-assembly and have characteristic chemical or biological assets in the cellular mechanisms3. Gold-based nanomaterials have attracted much attention in many areas of chemistry, physics and biosciences because of their size- and shape-dependent optic, electric, and catalytic properties. Here we report for the first time a one step synthesis in which Manganese Superoxide Dismutase protein plays a key role in the reduction of gold salts via the use of a Good's buffer (HEPES) to produce gold nanoparticles, compared to other proteins as catalase (CAT) and bovine serum albumin (BSA).We prove that this effect is directly related with the biological activities of the proteins that have an effect on the gold reduction mechanisms. Such synthesis route also induces the integration of proteins directly in the AuNPs that are intrinsically safe by design using a one-step production method. This is an important finding that will have uses in various applications, particularly in the green synthesis of novel nanomaterials.

This paper reports on a systematic study of the plasmonic properties of periodic arrays of gold cylindrical nanoparticles in contact with a gold thin film. Depending on the gold film thickness, it observes several plasmon bands. Using a simple analytical model, it is able to assign all these modes and determine that they are due to the coupling of the grating diffraction orders with the propagating surface plasmons travelling along the film. With finite difference time domain (FDTD) simulations, it demonstrates that large field enhancement occurs at the surface of the nanocylinders due to the resonant excitation of these modes. By tilting the sample, it also observes the evolution of the spectral position of these modes and their tuning through nearly the whole visible range is possible. Such plasmonic substrates combining both advantages of the propagative and localised surface plasmons could have large applications in enhanced spectroscopies.

Terahertz (THz) spectroscopy has drawn great interest for the functional and conformational investigations of nucleic acids, but its intrinsic sensitivity hinders potential bio-sensing applications. Here, a novel THz biosensor was developed for detecting microRNA (miRNA) samples based on metamaterials coupled with nanoparticles and strand displacement amplification (SDA). In this method, the SDA reaction amplifies the target miRNA and generates copious yields of secondary DNA molecules (Trigger DNA), which are subsequently conjugated to metallic nanoparticles that form nanoparticle-Trigger DNA complexes. These complexes produce remarkable frequency shifts of metamaterials when linked to a large refractive index metallic nanoparticle like Au. The dependence of the metamaterial resonance on the nanoparticle diameter and metal type was investigated experimentally and theoretically. Under optimal conditions, the THz metamaterial biosensor presents good detection sensitivity with a limit of detection of 14.54 aM and exhibits a linear response for miRNA-21 at a concentration range from 1 fM to 10 pM. By measuring the miRNA-21 in spiked clinical serum samples, the sample recoveries were determined to be in the range between 90.92% and 107.01%. These findings demonstrate that the novel THz biosensor offers the capability for highly sensitive miRNA detection, with noteworthy potential applications in nucleic acid analysis and cancer diagnosis.

Herein, we report a new approach to rapidly actuate the plasmonic characteristics of thin gold films perforated with nanohole arrays that are coupled with arrays of gold nanoparticles. The near-field interaction between the localized and propagating surface plasmon modes supported by the structure was actively modulated by changing the distance between the nanoholes and nanoparticles and varying the refractive index symmetry of the structure. This approach was applied by using a thin responsive hydrogel cushion, which swelled and collapsed by a temperature stimulus. The detailed experimental study of the changes and interplay of localized and propagating surface plasmons was complemented by numerical simulations. We demonstrate that the interrogation and excitation of the optical resonance to these modes allow the label-free SPR observation of the binding of biomolecules, and is applicable for in situ SERS studies of low molecular weight molecules attached in the gap between the nanoholes and nanoparticles.

Experimental results obtained in different laboratories world‐wide by researchers using surface‐enhanced Raman scattering (SERS) can differ significantly. We, an international team of scientists with long‐standing expertise in SERS, address this issue from our perspective by presenting considerations on reliable and quantitative SERS. The central idea of this joint effort is to highlight key parameters and pitfalls that are often encountered in the literature. To that end, we provide here a series of recommendations on: a) the characterization of solid and colloidal SERS substrates by correlative electron and optical microscopy and spectroscopy, b) on the determination of the SERS enhancement factor (EF), including suitable Raman reporter/probe molecules, and finally on c) good analytical practice. We hope that both newcomers and specialists will benefit from these recommendations to increase the inter‐laboratory comparability of experimental SERS results and further establish SERS as an analytical tool., Parameters and pitfalls: Key parameters and pitfalls that are often encountered in surface‐enhanced Raman scattering (SERS) are highlighted. Good analytical practice is proposed to increase the inter‐laboratory comparability of experimental SERS results and further establish SERS as an analytical tool.

In this work, we bring back a rapid way to conceive doxorubicin (DOX) hybrid gold nanoparticles, in which DOX and Au(III) ions were complexed with a hydrochloride-lactose-modified chitosan, named CTL and dicarboxylic acid-terminated polyethylene-glycol (PEG), leading to hybrid polymer-sugar-metal nanoparticles (DOX–AuGSs). All formulations were assessed by spectroscopic techniques (Raman and UV-Vis) and transmission electron microscopy (TEM). To estimate the therapeutic effect of DOX–AuGSs in liver cancer, murine HepG2 cells were used to induce a hepatic carcinoma model in nude mice. The survival time of the tumor-bearing mice, body weight and tumor volume were measured and recorded. The cytokines were used to detect the serum inflammatory factors, and the blood cell analyzer was used to determine the blood cell content of different groups of nude mice. The outcomes demonstrate that DOX–AuGCs significantly suppressed the tumor growth derived from human HepG2 injection and reduce the tumor index without affecting the body weight of mice. Moreover, DOX–AuGCs significantly reduced the serum levels of cytokines IL-6, TNF-α and IL-12 P70. Finally, a histological analysis of the heart tissue sections indicated that DOX–AuGCs significantly reduce the chronic myocardial toxicity of DOX during the period of treatment.

Since the discovery of Surface Enhanced Raman Spectroscopy (SERS) and the proven ability for this technique to detect molecules at trace level, numerous techniques have been reported for fabricating substrates that ensure reliable and reproducible SERS signal on its whole surface. In this paper we studied the capabilities and sensing performances of three commercial SERS substrates (RAM-SERS-SP from Ocean Optics, QSERS from Nanova Inc. and Hamamatsu from Hamamatsu Photonics) by using diluted solution of 4-mercaptobenzoic acid (MBA) at two different excitation wavelengths (633 and 785 nm). Large datasets were obtained through Raman mappings collected randomly on different areas on the substrate surface. The averaged SERS signals for one specific vibrational band of the MBA were used to compare limit of detection (LOD), limit of quantification (LOQ) and sensitivity of the three substrates. LOD and LOQ between 1 μM and 10 μM were calculated with a range of use of only one or two orders of magnitude. The best sensing performances were reached by the Hamamatsu substrate for an excitation wavelength of 633 nm.

The use of phosphonate ligands to modify the nanoparticle (NPs) surface has attracted a strong interest in the last years for the design of highly functional hybrid materials. Here, we applied a methodology to synthesize bisphosphonates having functionalized PEG side chains with a specific length in order to design a novel class of hybrid nanomaterials composed by tetraphosphonate-complex-gold COOH-terminated PEG-coated NPs (Bis-PO-PEG-AuNPs). The synthetic approach consist in three steps: (1) Complexation between new phosphonate ligands (Bis PO) and tetrachloroauric acid (HAuCl4) to form gold clusters; (2) adsorption of COOH-terminated PEG molecules (PEG) onto Bis PO-Au complex; (3) reduction of metal ions in that vicinity, growth of gold particles and colloidal stabilization. The obtained snow-shape-like hybrid nanoparticles, have been characterized by ultra-violet/visible, Raman spectroscopies, and electron microscopy imaging, involving their optical properties and photothermal activity in pancreatic adenocarcinoma cancer cells (PDAC).

International audience; Photoniques 90 Diffusion Raman exaltée de surface : principe et mécanismes La spectroscopie Raman permet d'ac-céder aux niveaux vibrationnels des molécules (tout comme la spectros-copie infra-rouge) et par conséquent d'identifier la composition chimique et la structure de systèmes molécu-laires de façon certaine. D'un point de vue physique, l'onde électroma-gnétique provenant d'une source laser monochromatique induit un moment dipolaire oscillant dans la molécule (le moment dipolaire in-duit P est lié au tenseur polarisabi-lité [α] de la molécule et au vecteur champ électrique incident E, selon : P = [α] E). Si cette spectroscopie présente de nombreux avantages comme par exemple de pouvoir travailler avec des échantillons sous différents états physiques (solide, liquide ou gaz), elle présente un inconvénient majeur, à savoir que le spectre ob-tenu, pour des échantillons à faible concentration, est de faible intensité et peut être complètement masqué par sa fluorescence. La diffusion Raman exaltée de surface (DRES) ou SERS en anglais (surface enhanced Raman scattering) permet de surmon-ter cette limitation en amplifiant le signal Raman [1]. La méthode consiste à exploiter une surface mé-tallique nano-structurée (principale-ment en Au, Ag ou Cu) pour exalter de plusieurs ordres de grandeurs l'intensité de la réponse Raman des molécules présentes au voisinage de la surface métallique (voir le schéma de principe sur la figure 1). Il est en effet établi que l'effet SERS trouve principalement son origine dans un phénomène d'amplification du champ électromagnétique diffusé par les particules métalliques (ce mé-canisme est dit électromagnétique COMPRENDRE La diffusion Raman exaltée de surface La spectroscopie Raman est une spectroscopie vibrationnelle très peu sensible qui limite l'analyse d'espèces chimiques aux fortes concentrations. Néanmoins, lorsque des molécules sont placées au voisinage d'une surface métallique nanostructurée, il est possible d'exalter considérablement leur signature Raman. On parle alors de diffusion Raman exaltée de surface. Les remarquables potentialités de cette technique ont nourri de nombreux champs d'étude tant pour le design de substrats dits SERS-actifs, que pour l'exploration d'applications en médecine, pharmacologie, défense ou le monde de l'art.

International audience; The coating of fused silica by an organized layer of silica nanospheres (NS) is an important issue for the design of optical and topographic properties especially for lithography techniques such as nanosphere lithography (NSL) or nanosphere photolithography (NSPL). Here, the spin coating of NS dispersed in N, N-dimethylformamide (DMF) is studied. The role of the NS diameter, the spin-coating acceleration, and the volume fraction are the parameters to take into account for the formation and organization of NS in single or double closely packed layers. We propose an explanation for this behavior based on the transition between sedimentation and a viscous regime on the basis of the silica NS organization.

Surface-enhanced Raman scattering (SERS) is a mature vibrational spectroscopic technique, and its application in chemical, material, especially life sciences is increasing rapidly. SERS alone cannot meet the demands of current analysis, while the desirable features of nucleic acid isothermal amplification (NAIA) make the simple, economical and flexible SERS become a reality. SERS has been combined with NAIA to provide researchers with more sensitive and precise analysis specifications in biological samples. However, there is no comprehensive review of the SERS analysis combined with NAIA yet. The present review introduces the development of SERS briefly and summarizes the necessary theory for understanding SERS and NAIA. The SERS analyses integrated with NAIA are the centerpiece of this review. They cover a broad range of topics, for example, hybridization chain reaction (HCR), catalytic hairpin assembly (CHA), entropy-driven catalytic reaction (EDR), strand displacement amplification (SDA), recombinase polymerase amplification (RPA), exponential amplification reaction (EXPAR), rolling circle amplification (RCA), and loop-mediated isothermal amplification (LAMP). In the end, the challenges and prospective opinions of the SERS in application are discussed.

Exosomal microRNA (miRNA) is a promising non-invasive biomarker for liquid biopsies. Herein, we fabricated a terahertz (THz) metamaterial biosensor that comprises an array of gold (Au) discs surrounded by annular grooves for exosomal miRNA assays based on duplex-specific nuclease (DSN)-triggered rolling circle amplification (RCA). In this strategy, the target miRNA is captured by a probe P0 immobilized on magnetic beads (MBs); it then repeatedly releases a primer P1 under the action of DSN, which acts as a highly specific initiator of the subsequent RCA step utilizing biotin-dUTP. After target recycling and nucleic acid amplification, the biotinylated amplification products were captured by the streptavidin (SA)-functionalized THz metamaterials, and further conjugated to SA-modified AuNPs that permit formation of a trimeric complex of SA-biotinylated RCA products-AuNP. The complex population scales with the starting concentration of the target miR-21, resulting in a red shift of the resonance peak of the THz metamaterials. This biosensor can lead to highly specific and sensitive detection with one-base mismatch discrimination and a limit of detection (LOD) down to 84 aM. Significant distinctions are seen in the frequency shifts for exosomal miR-21 quantitation in clinical plasma samples between pancreatic cancer patients and healthy controls. The frequency shifts of the THz metamaterials are consistent versus the reverse transcription-polymerase chain reaction (RT-PCR) results, illustrating the applicability and accuracy of our assay in real clinical samples.

A fast and sensitive colorimetric assay for the determination of prostatic acid phosphatase (PAP) levels using biphosphonates-PEG-coated gold nanoparticles (BP-PEG-AuNPs) has been developed. Addition of different amounts of PAP to the AuNPs results in a significant change of color, from a red-wine color to purple, and finally to blue. The PAP should bind onto the AuNPs surface and crosslink the AuNPs inducing their aggregation and as a consequence a color change of the solution from wine red to purple/blue. The color change was monitored by UV–vis spectrophotometry or with the naked eye. The ensuing concentration-dependent red-shift of surface plasmon resonance absorption allows the determination concentration within the fg range in 10 min. Importantly, the visual detection limit (1 ng/mL) allows the rapid differential diagnosis with naked eye or image analyzer. This demonstrates that the color modification observed with BP-PEG-AuNP is effectively due to an interaction between PAP and BP. Keywords: Prostatic acid phosphatase, Gold nanoparticles, Bisphosphonates, Colorimetric detection, Localized surface plasmon resonance

We report a simple and original method to synthesize water-soluble gold nanoparticles in which a polyphenolic fraction, extracted by two plants originated from Reunion Island, was mixed to tetrachloroauric acid (HAuCl4) leading to shell-like hybrid flavonoid-metal nanoparticles (NPs). The nanoparticles have been characterized by ultra-violet/visible Raman spectroscopy, and also by electron microscopy imaging (TEM). The results of these analytical green methodologies highlight nanometric sized, stable, hybrid complexes of about 15 nm, or flower-shaped 40 nm diameter with outer surface rich of functional chemical groups. This paper, through an original chemical approach, will occupy an important position in the field of Nanomedicine, and the authors hope that novel perspectives will be proposed for the development of a double nanotheranostic (plasmonic phototherapeutic and X-ray based computed tomography (CT scan)) in order to treat cancer simultaneously by plasmonic phototherapy (PTT), and at the same time to allow the visualization by X-ray based computed tomography. Keywords: AuNPs, Flavonoids, CT scan, Gold complex, Nanomedicine

We report an original approach to synthesize hybrid gold nanostructures in which doxorubicin (DOX), mixed to Poliethylenglycole diacid (PEG-COOH) led to original hybrid gold nanovector (DOX IN PEG AuNPs). In this work, we investigate the ability of DOX IN PEG-AuNPs to detect the amplification of the hybridization process by a sensitive Quartz crystal Microbalance with dissipation (QCM-D) by intercalation process. The sensing layer was carried out by self-assembled monolayer of β mercaptoethylamine (cysteamine) on gold-coated quartz crystal sensor composed by a rigid homobifunctional cross-linker 1,4 phenilenediisothiocyanate (PDITC) linked covalently with amino-probe oligonucleotides. By QCM characterization in the range from 8 µM to 20 nM, we demonstrate high specificity of DOX IN PEG-AuNPs-DNA with a limit of detection (LOD) of 9 nM. This result is very promising for development of sensitive and effective nanoparticle-based biosensor for quantifying small biomolecules concentration in physiological liquids. These results open a possibility to realize a new class of nanovector which will be tailored for different biomedical application, such as imaging, targeting and drugs delivery. Keywords: Quartz Crystal Microbalance (QCM), Chemical surface, DNA hybridization, Gold nanoparticles, Doxorubicin

The effective detection volume in the case of confocal fluorescence microscopy was investigated in situ by two methods the fluorescence correlation spectroscopy (FCS) of diluted fluorophore solutions, and the measurement of the point spread function (PSF) with calibrated fluorescent microspheres. The determination of the effective volume depends on many parameters and the optical variations in the refractive index were studied experimentally by measuring the PSF under various environmental conditions. The fluorescent microspheres were embedded in different refractive index surroundings media, and excited by a focused Gaussian beam. This allowed us to demonstrate that the mismatches that occur in the refractive index between the media and the sample induce a significant difference in the size of the effective volume and hence in the evolution of the optical resolution. The experimental confocal volume values were compared with those reported in theoretical studies based on the Lanni and Gibson model.

The surface characterization of branched and spherical gold nanoparticles was done by two complementary techniques: scattering correlation spectroscopy (SCS) and surface-enhanced Raman spectroscopy (SERS). Thiophenol was used as a surface marker to probe the surface area and the gold–thiophenol interaction in gold nanourchins (GNUs) and gold nanospheres (GNSs). We observed that, for GNU, the thiophenol is first grafted on the core, with a saturation concentration of about 10–3 M as observed for GNSs. Afterward, the saturation of the branches occurs at a higher thiophenol concentration (∼1 M). A numerical calculation of the surface areas of GNSs of different sizes allowed for the estimation of the GNU surface area. The hydrodynamic radius was measured at different steps of thiophenol–GNP functionalization. By comparing spherical and nonspherical nanoparticles, we demonstrate that the molecule–GNP interaction is highly dependent on the nanoparticle morphology (size and shape).

Environmental and biomedical nanoparticles can pose potential health risks to the human respiratory system by inducing severe lung inflammation. The aim of this case study is to present a comparison of the inflammatory response in four in vitro models of the human lung epithelium, differing by composition and/or culturing substrates, when exposed to gold nanoparticles (AuNPs). Three in vitro models of lung adenocarcinoma (A549) cells and a commercially available three-dimensional (3D) culture (MucilAir™) were tested. The models were exposed to AuNPs for 3, 6, and 24 h. AuNPs internalisation was investigated by confocal, electron microscopy, and Raman spectroscopy. Enzyme-Linked Immuno-Sorbent Assay (ELISA) was used for quantifying the secretion of the inflammatory mediator Interleukin-6 (IL-6) following exposure to AuNPs. Finally, a microfluidic approach was developed in-house to investigate whether pro-inflammatory mediators present in supernatants harvested from the AuNPs-treated cell cultures could trigger monocyte activation. Our results demonstrated that AuNPs were internalised only in submerged cultures grown on glass substrates. Nevertheless, AuNPs internalisation did not trigger a significant IL-6 secretion. Significant amounts of IL-6 were secreted by AuNPs-treated mono-cultures grown on Transwell™ inserts, triggering monocyte activation in dynamic microfluidic experiments. AuNPs did not induce IL-6 secretion in co-cultures and MucilAir™ models, although supernatants harvested from co-cultures triggered monocyte activation. Our case study demonstrates that in vitro complexity, as well as culturing substrates, deeply influence the detectable cellular responses to nanoparticles, and advocate for the adoption of more advanced tissue-mimetic cultures of the human respiratory system for nanomaterials testing.

Plasmonic and surface enhanced Raman scattering (SERS) studies have been performed on aluminum nanocylinders arrays of different diameters. We observed sharps localized surface plasmon resonance (LSPR) peaks that can be tuned on the whole visible range and having the same behavior than gold nanocylinders. The near-field enhancement was measured by SERS on probe molecules as well as on the indium tin oxide (ITO) substrate using two excitation wavelengths: 660 and 785 nm. No SERS signal of the probe molecules was detected. Using the ITO substrate SERS signal, we were able to measure a small near-field enhancement largely lower than the one reached with gold nanocylinders indicating that this kind of structure in not usable for SERS in this spectral range. A spectral shift is also observed between the SERS measurement and the LSPR position. All the experimental results are compared to DDA simulation in order to provide interpretation of the data.

As a fast-growing technology, terahertz time-domain spectroscopy (THz-TDS) is becoming increasingly pervasive in biological applications, targeting a range of biomaterials from biomolecules to tissues. However, THz-TDS studies at the cellular level are quite limited. Thus, a study to analyze the living state and hydration state of a tumor cell in a label-free manner is carried out and reported here. Combined with a specially designed THz metamaterial, a tumor cell monolayer was detected continuously over a period of time. In addition, in order to explore the possible impact of the metamaterial on tumor cells, the secretion of IL-6, IL-8, GM-CSF and GROα of cell supernatants was detected. The results demonstrated that the technology could characterize the living state by monitoring the extracellular water and investigate the hydration state inside a tumor cell in real time, showing great application potential for the label-free detection of normal cells and tumor cells of diverse malignant degree.

An indirect aptamer-based SERS assay for insulin-like growth factor 2 receptor (IGF-IIR) protein was developed. The gold substrate and silver nanoparticles (AgNPs) were employed simultaneously to achieve double enhancement for SERS signals. Firstly, the five commercial SERS substrates including Enspectr, Ocean-Au, Ocean-AG, Ocean-SP and Q-SERS substrates were evaluated using 4-mercaptobenzoic acid (4-MBA). The Q-SERS substrate was selected based on low relative standard deviation (RSD, 8.6%) and high enhancement factor (EF, 8.7*105), using a 785 nm laser. The aptamer for IGF-IIR protein was designed to include two sequences: one grafted on gold substrate to specifically capture the IGF-IIR protein and a second one forming a 3′ sticky bridge to capture SERS nanotags. The SERS nanotag was composed by AgNPs (20 nm), 4-MBA and DNA probes that can hybridize with the aptamer. Due to the steric-hindrance effect, when the aptamer doesn’t combine with IGF-IIR protein, it only can capture the SERS nanotags. Therefore, there was a negative correlation between the concentration of IGF-IIR protein and the intensity of 4-MBA at 1076 cm−1. The detection limit reached to 141.2 fM and linear range was from 10 pM to 1 μM. The SERS aptasensor also exhibits a high reproducibility with an average RSD of 4.5%. The interference test was conducted with other four proteins to verify the accuracy of measuring. The study provides an approach to quantitative determination of proteins based on specific recognition and nucleic acid hybridization of aptamers, to establish sandwich structure for SERS enhancement.

Aptamers are functional small single-strand oligonucleotides (DNA) that show high affinity to their target molecules such as proteins or small analytes through the formation of specific secondary structures. In the present paper, we study the interaction of one aptamer with its target protein, the manganese superoxide dismutase (MnSOD), under specific conditions of surface chemical grafting. For this purpose, we exploit two different chemical strategies to graft the aptamers onto pegylated gold nanoparticles: the carbodiimide chemistry (EDC/NHS method) and the thiol covalent bond (S–Au bond). We also study the influence of the presence of a spacer of 15 thymine bases at the aptamer extremity. The aptamer interactions with the MnSOD were characterized by UV-Vis absorption on a large range of MnSOD concentrations (from 10−12 up to 10−5 M). We observe that the interaction is strongly dependent on the MnSOD concentration and also on the aptamer structure at the surface of the gold nanoparticles. We demonstrate that the highest affinity is obtained for the aptamer with the 15 thymine bases spacer and grafted with the carbodiimide method. We assume that the grafting method has a strong influence on the accessibility and the conformation of the aptamer at the nanoparticle surface and thus on its possibility to interact with the MnSOD.

Our understanding of the fate and distribution of micro- and nano- plastics in the marine environment is limited by the intrinsic difficulties of the techniques currently used for the detection, quantification, and chemical identification of small particles in liquid (light scattering, vibrational spectroscopies, and optical and electron microscopies). Here we introduce Raman Tweezers (RTs), namely optical tweezers combined with Raman spectroscopy, as an analytical tool for the study of micro- and nanoplastics in seawater. We show optical trapping and chemical identification of sub-20 mu m plastics, down to the 50 nm range. Analysis at the single particle level allows us to unambiguously discriminate plastics from organic matter and mineral sediments, overcoming the capacities of standard Raman spectroscopy in liquid, intrinsically limited to ensemble measurements. Being a microscopy technique, RTs also permits one to assess the size and shapes of particles (beads, fragments, and fibers), with spatial resolution only limited by diffraction. Applications are shown on both model particles and naturally aged environmental samples, made of common plastic pollutants, including polyethylene, polypropylene, nylon, and polystyrene, also in the presence of a thin ecocorona. Coupled to suitable extraction and concentration protocols, RTs have the potential to strongly impact future research on micro and nanoplastics environmental pollution, and enable the understanding of the fragmentation processes on a multiscale level of aged polymers.

Colistin is recognized as the last therapeutic option for multidrug-resistant Gram-negative bacteria infection. In addition, bacterial resistance to colistin could be transmitted between different species through plasmid-mediated mcr-1 gene transfer. Therefore, rapid screening of colistin-resistant isolates will play a key role in controlling the spread of resistance and improving patient outcomes. We developed a rapid method for the detection of colistin-resistance in Escherichia coli, Acinetobacter baumannii, and Pseudomonas aeruginosa bacteria based on Raman spectroscopy and hierarchical cluster analysis. Bacteria were incubated with and without colistin using CAMHB as the liquid culture medium. They were then centrifuged and dried on a glass slide. Five Raman spectra of each of the samples were recorded and analyzed by the hierarchical cluster analysis method to determine whether the bacteria were resistant. To evaluate this method, 123 clinical bacterial isolates (42 isolates of E. coli, 41 isolates of A. baumannii and 40 isolates of P. aeruginosa) were tested. The detection sensitivity and specificity were 90.9% and 91.1%, respectively, compared with the reference broth microdilution method. The screening is easy to perform and can be completed in 1.5 h, suggesting that it holds great potential to be an initial screening method in countries and areas where colistin becomes the last resort antibiotic.

The study of protein interactions with gold nanoparticles (GNP) is a key step prior to any biomedical application. These interactions depend on many GNP parameters such as size, surface charge, chemistry, and shape. In this work, we propose to use a sensitive technique named scattering correlation spectroscopy or SCS to study protein interactions with GNP. SCS allowed the investigation of the GNP hydrodynamic radius with a very high sensitivity before and after interaction with proteins. No labeling is needed. As a proof-of-concept, two of the most used morphologies of GNP-based nanovectors have been used within this work: spherical-shaped GNP (GNS) and branched-shaped GNP (GNU). The measurement of several parameters such as the number of proteins binding to one GNP, the binding affinity and the cooperativeness of binding for three different plasma proteins on the GNP surface was carried out. While GNS showed an increase in the hydrodynamic radius, indicating that each kind of protein binds on the GNS in a specific orientation, GNU showed different orientations of proteins due to their multi-oriented surfaces (tips) with a higher surface to volume area. Quantitative data based on the Hill model were extracted to obtain the affinity of the proteins to both GNS and GNU surfaces. Data variations can be understood in terms of the electrostatic properties of the proteins, which interact differently with the negatively charged GNP surfaces.

Terahertz (THz) metamaterial-based reflection spectroscopy is proposed for label-free sensing of living cells by a self-referenced method. When sensing the living Madin-Darby canine kidney cell monolayer and phosphate buffered saline solution, self-referenced signals showed significant differences in peak intensity because of inherent discrepancy in the imaginary part of their complex refractive indices, as confirmed by 3D-FDTD simulations. The resonance peak intensity was unaffected by cell monolayer thickness variation, demonstrating feasibility for sensing various cells. Simulations and experiments showed that saponin-induced changes in cell permeability could be monitored in real-time. The self-referenced signal was linearly dependent on the adherent cell density, illustrating a label-free in situ THz metamaterial-based cell sensor.

Comparing the optical properties of plasmonic nanoparticles in terms of scattering, absorption and extinction is an active and delicate issue in nano-optics. Absorption cross sections are usually difficult to be reliably measured. In this work, the absorption of gold and aluminum nanodisks was measured using quantitative wavefront sensing. We evidence a spectral shift between the retrieved absorption and the extinction maxima. Discrete dipole approximation calculations enabled us to unravel the origins of the spectral shifts, which are different depending on the material. In the case of gold nanodisks, the mismatch between extinction and absorption (∼15 nm) is related to the frequency shift of the plasmonic field intensity between near-field and far-field regimes, respectively probed through the heat generated within the nanoparticles and the optical extinction. For aluminum nanodisks, displaying dipolar plasmon resonances in the wavelength range 700 to 850 nm, the spectral shift between extinction and ab...

The aim of this study is to compare the optical scattering properties of different gold nanoparticles (GNPs), with different shapes (spherical, GNSs, and flower-shaped, GNFs), sizes (20, 30, and 50 nm), and surface chemistries (with and without PEG). These scattering properties give geometrical characterization of hydrodynamic sizes of GNPs by using the scattering correlation spectroscopy. Afterward, a multiparametric comparative study of the scattering efficiency is presented depending on various parameters such as GNPs geometry, excitation wavelength (532 and 633 nm) and powers (from 5 to 100 μW). As predicted by Mie theory, we demonstrate that the increase in GNSs size leads to an increase of the scattered intensity, proportional to the excitation power. The scattered signal is the highest when the excitation wavelength is closer to the localized surface plasmon resonance. In the case of GNFs, the measured scattered signal is around 1000 times stronger than that for GNSs of the same size and concentrat...

Simple, rapid, and efficient cell viability assays play a fundamental role in much of biomedical research, including cell toxicology investigations and antitumor drug screening. Here, we demonstrate for the first time a rapid and label-free cell viability assay using THz spectroscopy in combination with a new optical clearing agent (OCA) and microfluidic technology. This strategy uses a considerably less absorptive OCA to replace the highly absorptive water molecules around the living cells and thus to decrease the background signal interference. Three low-viscosity oils were screened as potential OCA candidates, among which fluorinated oil was selected because of its lower absorption and lowest cytotoxicity. After the liquid medium was replaced with fluorinated oil in a microfluidic chip, an obvious THz spectral difference was observed between the fluorinated oils with and without living cells. This change in THz response was preliminarily attributed to the distinguishable signals between the cells and the fluorinated oil. In addition, we applied this method to cell viability assays of human breast cancer cells (MDA-MB-231) after treatment with different antitumor drugs. The results indicated that THz spectroscopy with the aid of the proposed water-replacement strategy presented excellent quantification of cell viability with the advantages of a rapid, label-free, nondestructive microassay, which offers significant potential to developing a convenient and practical cell analysis platform.