Plasmonic Nanoplatform Research Articles

Portable microfluidic plasmonic chip for fast real-time cardiac troponin I biomarker thermoplasmonic detection.

Acute myocardial infarction is one of the most serious cardiovascular pathologies, impacting patients' long-term outcomes and health systems worldwide. Significant effort is directed toward the development of biosensing technologies, which are able to efficiently and accurately detect an early rise of cardiac troponin levels, the gold standard in detecting myocardial injury. In this context, this work aims to develop a microfluidic plasmonic chip for the fast and accurate real-time detection of the cardiac troponin I biomarker (cTnI) via three complementary detection techniques using portable equipment. Furthermore, the study focuses on providing a better understanding of the thermoplasmonic biosensing mechanism taking advantage of the intrinsic photothermal properties of gold nanoparticles. Specifically, a plasmonic nanoplatform based on immobilized gold nanobipyramids was fabricated, exhibiting optical and thermoplasmonic properties that promote, based on a sandwich-like immunoassay, the "proof-of-concept" multimodal detection of cTnI via localized surface plasmon resonance, surface enhanced Raman spectroscopy and thermoplasmonic effects under simulated conditions. Furthermore, after the integration of the plasmonic nanoplatform in a microfluidic channel, the determination of cTnI in 16 real plasma samples was successfully realized via thermoplasmonic detection. The results are compared with a conventional high-sensitivity enzyme-linked immunosorbent clinical assay (ELISA), showing high sensitivity (75%) and specificity (100%) as well as fast response features (5 minutes). Thus, the proposed portable and miniaturized microfluidic plasmonic chip is successfully validated for clinical applications and transferred to clinical settings for the early diagnosis of cardiac diseases, leading towards the progress of personalized medicine.

Caged gold nanostars: a novel plasmonic nanoplatform with potential theranostic applications.

Here, we first introduce caged gold nanostars (C-GNS), a novel hybrid nanoplatform combining the exceptional plasmonic properties of nanostars with the loading capability of hollow-shell structures. We present two synthetic routes used to produce C-GNS particles and highlight the benefits of the galvanic replacement-free approach. FEM simulations explore the enhanced plasmonic properties of this novel nanoparticle morphology. Finally, in a proof-of-concept study, we successfully demonstrate in vivo hyperspectral imaging and photothermal treatment of tumors in a mouse model with the C-GNS nanoplatform.

Integrated magneto-plasmonic nanostructures-based immunoassay for galectin-3 detection.

Cardiovascular diseases remain a leading cause of global mortality, highlighting the need for accurate diagnostic tools and the detection of specific cardiac biomarkers. Surface-enhanced Raman scattering (SERS) spectroscopy has proved to be a promising alternative diagnostic tool to detect relevant biomarkers compared to traditional methods. To our knowledge, SERS methodology has never been used to detect galectin-3 (Gal-3), a crucial biomarker for cardiovascular conditions. Our study aimed to develop plasmonic and magneto-plasmonic nanoplatforms for the sensitive immunodetection of Gal-3 using SERS. Spherical gold nanoparticles (AuNPs) were synthesized and functionalized with 11-mercaptoundecanoic acid (MUDA) to enable antibody binding and 4-mercaptobenzoic acid (4MBA) that served as a Raman reporter due to its intense Raman signal. Following bioconjugation with Gal-3 antibody, the AuNPs were employed in the immunodetection of Gal-3 in phosphate-buffer saline (PBS) solution, offering a limit of detection (LOD) of 12.2 ng mL-1 and a working range up to 120 ng mL-1. Furthermore, our SERS-based immunosystem demonstrated selectivity for Gal-3 (40 ng mL-1) in the presence of other biomolecules such as α-amylase, bovine serum albumin and human C-reactive protein. As a proof of concept, we developed magneto-plasmonic nanoparticles composed of silica-coated magnetite decorated with the bioconjugated AuNPs aimed at enhancing the uptake and detection of Gal-3 via SERS coupled with Raman imaging. Our findings underscore the potential of SERS-based techniques for the sensitive and specific detection of biomarkers, holding significant implications for improved diagnosis and surveillance of cardiovascular diseases. Future research will focus on further optimizing these nanoplatforms and their translation into clinical settings.

Selecting plasmonic nanoshells for colorimetric sensors

In this work, the use of gold and silver nanoshells was evaluated as a starting point for the establishment of colorimetric sensor platforms. The sensitivity and linearity of the nanoplatforms (SiO2 core–metallic shell nanoparticles) were assessed under the influence of the nanoshell configuration, color space, and light source illuminant. A computational procedure for selecting high-performance plasmonic colorimetric sensor platforms is described. The evaluation methodology involves considering five different color spaces and 15 different color components. By exploring crucial figures of merit for sensing, the performance of the plasmonic nanoplatforms was evaluated, exploring Mie theory. We determined that gold nanoshells are highly efficient on colorimetric sensing, while silver nanoshells are a better choice for spectroscopic sensors. Plasmonic nanoplatforms based on nanoshells with 10 nm SiO2 core radii and 5 nm thick Au shells presented sensitivity values up to 4.70RIU−1, considering the hue angle of the HSV color space. Color variation of up to 40% was observed, due to the adsorption of a 10 nm thick molecular layer on the gold nanoshell surface. In the search for advances in colorimetric biosensors, the optimization approach used in this work can be extended to different nanostructures.

Bimetallic Gold Nanostars Having High Aspect Ratio Spikes for Sensitive Surface-Enhanced Raman Scattering Sensing.

There has been increasing interest in evolution of plasmonic nanoplatforms based on noble metal nanoparticles to achieve ultrasensitive detection of trace analyte molecules through solution-based surface-enhanced Raman spectroscopy (SERS). This work presents a surfactant-free synthesis method of bimetallic gold nanostars coated with silver (BGNS-Ag) having sharp, high aspect-ratio spikes for achieving ultrahigh detection sensitivity and high reproducibility. Specifically, the unique BGNS-Ag platform combines both the strong SERS enhancement effects of gold nanostar sharp spikes and the high scattering feature of the silver–gold bimetallic structure. To achieve SERS reproducibility, this solution-based SERS measurement requires minimal sample preparation without addition of any external reagents, which can cause irregular aggregation of nanoparticles and reduce the reproducibility of SERS measurements. Moreover, we have streamlined our SERS sensing procedure by using standard well-plates and a portable Raman device for SERS measurements, which could be utilized for rapid on-site detection. This solution-based SERS performance was studied using methylene blue (MB) as a model analyte system. The detection limit of MB was as low as 42 pM, indicating high sensitivity of detection using BGNS-Ag. To illustrate the usefulness for environmental sensing, we showed that the SERS sensor can detect a pesticide, thiram, at a concentration as low as 0.8 nM. This study demonstrated that the BGNS-Ag system could serve as an effective and versatile plasmonic-active platform for reproducible, fast, and in-field detection of small organic analytes at trace levels.

Novel insight on chemo-specific detection of toxic environmental chromium residues existing as recalcitrant Cr(III)-carboxyl complexes using plasmonic silver nanoplatform bi-functionalized with citrate and PVP

Chromium (Cr) is a toxic environmental pollutant that majorly exists in trivalent and hexavalent forms. Though Cr(VI) is more dangerous than Cr(III), the trivalent Cr forms complexes with environmentally-available organic molecules. This makes them potentially harmful and difficult to detect. In this study, we have designed an ultrasensitive plasmonic nanosensor using citrate and PVP functionalized Ag nanoparticles (Ag-citrate-PVPNPs) for the detection of trivalent chromium organic complexes such as Cr(III)-EDTA (Cr-E), Cr(III)-acetate (Cr-A), Cr(III)-citrate (Cr-C) and Cr(III)-tartrate (Cr-T). The nanoparticles (NPs) were structurally characterized by XRD, SEM, HRTEM, SAED, EDX and elemental mapping. The citrate and PVP molecules played a vital role in the detection mechanism and stability of the sensor. Upon detection, the yellow-colored Ag-citrate-PVP NPs turned into different shades of brown depending on the type of the Cr complex and concentration. It was accompanied by diminishing and/or shifting UV–Visible absorbance peaks due to the aggregation of Ag-citrate-PVP NPs. Further, a linear relationship was observed between absorbance reduction and analyte concentration. The selectivity tests showed that the sensor was non-functional to other metal ions and inorganic anions. The sensor was optimized using pH and temperature studies. The mechanism of detection was elucidated with the help of characterization techniques such as Raman spectroscopy, FTIR, XPS and UV–visible spectrophotometer. The limit of detection (LOD) was found to be 3.29, 4.87, 1.76 and 1.79 nM for Cr-E, Cr-A, Cr-C and Cr-T complexes respectively. This study provides a rapid and sensitive approach for the detection of multiple Cr(III)-organic complexes present in an aqueous solution.

Thermoplasmonic-Assisted Cyclic Cleavage Amplification for Self-Validating Plasmonic Detection of SARS-CoV-2.

The coronavirus disease 2019 (COVID-19) has penetrated every populated patch of the globe and sows destruction in our daily life. Reliable and sensitive virus sensing systems are therefore of vital importance for timely infection detection and transmission prevention. Here we present a thermoplasmonic-assisted dual-mode transducing (TP-DMT) concept, where an amplification-free-based direct viral RNA detection and an amplification-based cyclic fluorescence probe cleavage (CFPC) detection collaborated to provide a sensitive and self-validating plasmonic nanoplatform for quantifying trace amounts of SARS-CoV-2 within 30 min. In the CFPC detection, endonuclease IV recognized the synthetic abasic site and cleaved the fluorescent probes in the hybridized duplex. The nanoscale thermoplasmonic heating dehybridized the shortened fluorescent probes and facilitated the cyclical binding–cleavage–dissociation (BCD) process, which could deliver a highly sensitive amplification-based response. This TP-DMT approach was successfully validated by testing clinical COVID-19 patient samples, which indicated its potential applications in fast clinical infection screening and real-time environmental monitoring.

High Performance Gold Dimeric Nanorods for Plasmonic Molecular Sensing

A metal dimeric nanostructure is an alternative design for a Localized Surface Plasmon Resonance sensor. At the dimer nanojunction, a high E-field enhancement (hot spot) is observed. In this work, nanostructure size parameters such as aspect ratio, junction, and length of gold dimeric nanorods (AuDNR) linked end-to-end by a thin dielectric junction were evaluated numerically, optimizing the sensing parameters of the plasmonic nanoplatform. The computational approach focused on the assessment of the LSPR extinction spectral peak shift to their local surrounding medium in order to estimate the behavior of sensing parameters such as the figure of merit (FoM), the bulk sensitivity ( η <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B</sub> ) and the η <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B</sub> × FoM. The nanostructure aspect ratio, junction, and rod length were evaluated, optimizing the plasmonic nanoplatforms sensing parameters. The optimized AuDNR achieved a high sensing performance with η <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B</sub> = 544 nm/RIU and FoM = 12.4 RIU <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> . Moreover, the obtained η <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B</sub> × FoM = 6745.6 nm/RIU <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> is the highest reported value in the literature. For molecular sensing, Campbell's model was explored to evaluate the wavelength shift as a result of molecular adsorption on the nanoparticle surface. We demonstrate that the dimeric nanostructure exhibit twice LSPR peak shift due to a thin molecular adsorption layer rather than a monomer of equivalent size. Our results show that optimized dimeric nanostructure is highly attractive for molecular identification, opening the possibility of establishing new nanoplatforms for medical diagnostic.

Preface to the special issue dedicated to Professor Richard P. Van Duyne (1945–2019)

Preface to the special issue dedicated to Professor Richard P. Van Duyne (1945–2019)

State-of-art plasmonic photonic crystals based on self-assembled nanostructures

Controlled self-assembly of plasmonic photonic nanostructures provides a cost-effective and efficient methodology to expand plasmonic photonic nano-platforms with unique, tunable, and coupled optical characteristics.

Plasmonic nanoplatforms: From surface‐enhanced Raman scattering sensing to biomedical applications

AbstractIn this work, we present an overview of the development and application of surface‐enhanced Raman scattering (SERS) and plasmonic nanoplatforms developed in our laboratory in recent years. We have developed a wide variety of plasmonics‐active substrates and nanoparticle‐based sensing platforms including inverse molecular sentinels (iMS) utilizing gold nanostars (AuNS) and nanorattle DNA sensors (NR). These platforms have been used for a wide variety of applications, such as monitoring genomic biomarkers in plants for renewable bioenergy research, point‐of‐care diagnostics of infectious diseases (dengue and malaria), and detection of cancer biomarkers for gastrointestinal and head and neck cancers. Applications of plasmonic AuNS in bioimaging, photothermal therapy (PTT), and immunotherapy are also presented. An interesting advance was the development of AuNS‐mediated PTT in combination with immunotherapy, a method referred to as Synergistic Immuno Photothermal Nanotherapy (SYMPHONY), which broadens and significantly enhances the efficacy of immunotherapy. This review highlights various applications of the unique plasmonics‐enabled sensing and therapeutic nanotechnologies that contribute to the lasting legacy of the discovery of SERS.

Gas Foaming Guided Fabrication of 3D Porous Plasmonic Nanoplatform with Broadband Absorption, Tunable Shape, Excellent Stability, and High Photothermal Efficiency for Solar Water Purification

AbstractSolar steam generation is an efficient way for water purification. However, it is still challenging to establish a steam generation system possessing high evaporation efficiency under natural sunlight condition with good durability. Herein a novel, free‐floating nanoplatform is constructed by a gas foaming strategy, embedding plasmonic Cu7S4‐MoS2‐Au nanoparticles (CMA NPs) in porous polydimethylsiloxane (PDMS) matrix. The gas diffusion process creates 3D porous PDMS matrix with low thermal conductivity and open channels, which allows for efficient energy confinement and fast water supply in an integral matrix, beneficial to mechanical strength of the system. By taking advantage of broadband absorption and high photothermal efficiency of CMA NPs and structural design of the matrix, the nanoplatform achieves a high evaporation rate (3.824 kg m−2 h−1) and photothermal conversion efficiency (96.6%) under one‐sun illumination (1 kW m−2). Moreover, such performance maintains stable even under harsh conditions in the presence of strong acid, strong base, strong oxidants, and high salinity, suggesting a broad prospect in seawater desalination, sewage treatment, sterilization and so on.

Versatile Polypeptide-Functionalized Plasmonic Paper as Synergistic Biocompatible and Antimicrobial Nanoplatform.

Nowadays, thanks to nanotechnological progress, which itself guides us more and more closely toward not only the efficient design of innovative nanomaterials or nanostructures, but to the improvement of their functionality, we benefit from an important asset in the battle against pathogenic illnesses. Herein, we report a versatile biocompatible plasmonic nanoplatform based on a Whatman paper incorporating positively-charged gold nanospherical particles via the immersion approach. The morphological characterization of the as-engineered-plasmonic paper was examined by SEM (scanning electron microscopy) and HRTEM (high-resolution transmission electron microscopy) investigations, while its surface chemical modification with a synthetic polypeptide, specifically RRWHRWWRR-NH2 (P2), was proved by monitoring the plasmonic response of loaded gold nanospheres and the emission signal of P2 via fluorescence spectroscopy. The as-functionalized plasmonic paper is non-cytotoxic towards BJ fibroblast human cells at bactericidal concentrations. Finally, the antimicrobial activity of the P2-functionalized plasmonic paper on both planktonic bacteria and biofilms was tested against two reference strains: Gram-positive Bacteria, i.e., Staphylococcus aureus and the Gram-negative Bacteria, i.e., Escherichia coli, determining microbial inhibition of up to 100% for planktonic bacteria. In line with the above presented nanoplatform’s proper design, followed by their functionalization with active antimicrobial peptides, new roads can be open for determining antibiotic-free treatments against different relevant pathogens.

Colorimetric determination of DNA using anaptamer and plasmonic nanoplatform.

A facile plasmonic nanoplatform was developed for rapid and sensitive determination of nucleic acid. Hg2+-regulated molecular beacon (MB, hairpin) containing rich thymine (T) bases at both ends is used as the probe. A hairpin structure can be formed in theMB probe due to the strong binding of Hg2+ to T. However, in the presence of target DNA, the hairpin structure is opened owing to target DNA-specific hybridization with theaptamer. Simultaneously, the opened MB interacts with poly(diallyldimethylammonium chloride) (PDDA) and hinders PDDA-induced aggregation of AuNPs, accompanied by a color change from blue to red and a decrease in absorption ratio (A620/A520). Hence, a good linear relationship was observed between the decreased absorption ratio (A620/A520) and DNA concentration ranging from 0.02 to 2nmol/L with a low detection limit of 4.42pmol/L. Moreover, this nanoplatform has been successfully utilized to discriminate between perfect target and mismatch sequences. More importantly, the bioassay is simple, versatile, rapid, and cost-effective compared with other common methods, which holds great promise for clinical diagnosis and biomedical application. Graphical abstract.

Self-assembly plasmonic metamaterials based on templated annealing for advanced biosensing.

In this paper, we introduce a novel method for the fabrication of self-assembly plasmonic metamaterials by exploiting fluid instabilities of optical thin films. Due to interplay between template reflow and spinodal dewetting, two metal nanoparticles of different sizes are generated on the top mesas of free-standing porous anodic aluminum oxide (AAO) template, which results in the apprearance of double resonant peaks in the extinction spectrum. These two resonant peaks possess refractive index resolution 3.27 × 10-4 and 2.53 × 10-4 RIU, respectively. This optical intensity modulation based plasmonic nanoplatform shows a dramatically surface sensing performance with outstanding detection capacity of biomolecules, because of the very small decay length of electric field at dual-modes. The detection ability for concanavalin A (Con A) demonstrats that the limit of detection of dual-modes reaches as small as 68 and 79 nM, respectively.

An enzyme-free and label-free visual sensing strategy for the detection of thrombin using a plasmonic nanoplatform.

An enzyme-free and label-free visual sensing strategy was developed for sensitively detecting thrombin using a plasmonic nanoplatform. Both the thrombin-triggered catalytic hairpin assembly (CHA) amplification reaction and G-quadruplex/hemin DNAzyme-controlled plasmonic signal readout were engineered on an electrospun nanofibrous membrane. Owing to its large specific surface area and porous structure, the nanofibrous membrane enhanced the loading capacity of B-H2 and the interface interaction efficiency. This plasmonic nanoplatform was used to perform the sensitive and naked-eye detection of thrombin as low as 1.0 pM in human serum samples. This visual strategy can discriminate thrombin from other co-existing proteins very well. Moreover, the visual sensing platform exhibited excellent reusability and long-term stability. The proposed enzyme-free and label-free plasmonic nanoplatform is low-cost, easy to operate and highly sensitive, and has potential applications in the point-of-care detection of protein biomarkers.

Plasmonic nanoplatform for point-of-care testing trace HCV core protein

Early diagnosis of hepatitis C virus (HCV) infection is still urgently desired as there is a global healthy burden and no vaccine available. In this work, a plasmonic nanoplatform was engineered with catalytic hairpin assembly (CHA) amplification reaction specifically of HCV core protein (HCVcp), G-quadruplex/hemin DNAzyme and nanofibrous membrane together. HCVcp was detected in whole serum at the ultralow concentration of 1.0 × 10−4 pg/mL with naked eye. By testing serum samples from 30 donors with different viral loads, detection sensitivity of the plasmonic nanoplatform turned out to be much better than that of the commercial ELISA kit. In addition, the plasmonic nanoplatform exhibited high specificity, excellent reusability and long-term stability. Naked-eye detection based on the plasmonic nanoplatform is expected to have potential applications in point-of-care testing (POCT) and early diagnosis of hepatitis C and other infectious diseases.

Multimodal Biosensing on Paper-Based Platform Fabricated by Plasmonic Calligraphy Using Gold Nanobypiramids Ink.

In this work, we design new plasmonic paper-based nanoplatforms with interesting capabilities in terms of sensitivity, efficiency, and reproducibility for promoting multimodal biodetection via Localized Surface Plasmon Resonance (LSPR), Surface Enhanced Raman Spectroscopy (SERS), and Metal Enhanced Fluorescence (MEF). To succeed, we exploit the unique optical properties of gold nanobipyramids (AuBPs) deposited onto the cellulose fibers via plasmonic calligraphy using a commercial pen. The first step of the biosensing protocol was to precisely graft the previously chemically-formed p-aminothiophenol@Biotin system, as active recognition element for target streptavidin detection, onto the plasmonic nanoplatform. The specific capture of the target protein was successfully demonstrated using three complementary sensing techniques. As a result, while the LSPR based sensing capabilities of the nanoplatform were proved by successive 13–18 nm red shifts of the longitudinal LSPR associated with the change of the surface RI after each step. By employing the ultrasensitive SERS technique, we were able to indirectly confirm the molecular identification of the biotin-streptavidin interaction due to the protein fingerprint bands assigned to amide I, amide III, and Trp vibrations. Additionally, the formed biotin-streptavidin complex acted as a spacer to ensure an optimal distance between the AuBP surface and the Alexa 680 fluorophore for achieving a 2-fold fluorescence emission enhancement of streptavidin@Alexa 680 on the biotinylated nanoplatform compared to the same complex on bare paper (near the plasmonic lines), implementing thus a novel MEF sensing nanoplatform. Finally, by integrating multiple LSPR, SERS, and MEF nanosensors with multiplex capability into a single flexible and portable plasmonic nanoplatform, we could overcome important limits in the field of portable point-of-care diagnostics.

Tailoring the Core-Satellite Nanoassembly Architectures by Tuning Internanoparticle Electrostatic Interactions.

The use of plasmonic nanoplatforms has received increasing interest in a wide variety of fields ranging from theranostics to environmental sensing to plant biology. In particular, the development of plasmonic nanoparticles into ordered nanoclusters has been of special interest due to the new chemical functionalities andoptical responses that they can introduce. However, achieving predetermined nanocluster architectures from bottom-up approaches in the colloidal solution state still remains a great challenge. Herein, we report a one-pot assembly approach that provides flexibility in precise control of core-satellite nanocluster architectures in the colloidal solution state. We found that the pH of the assembly medium plays a vital role in the hierarchy of the nanoclusters. The architecture along with the size of the satellite gold nanoparticles determines the optical responses of nanoclusters. Using electron microscopy and optical spectroscopy, we introduce a set of design rules for the synthesis of distinct architectures of silica-core gold satellites nanoclusters in the colloidal solution state. Our findings provide insight into advancing the colloidal solution state nanoclusters formation with predictable architectures and optical properties.

Designing Efficient Low-Cost Paper-Based Sensing Plasmonic Nanoplatforms.

Paper-based platforms can be a promising choice as portable sensors due to their low-cost and facile fabrication, ease of use, high sensitivity, specificity and flexibility. By combining the qualities of these 3D platforms with the optical properties of gold nanoparticles, it is possible to create efficient nanodevices with desired biosensing functionalities. In this work, we propose a new plasmonic paper-based dual localized surface plasmon resonance–surface-enhanced Raman scattering (LSPR-SERS) nanoplatform with improved detection abilities in terms of high sensitivity, uniformity and reproducibility. Specifically, colloidal gold nanorods (GNRs) with a well-controlled plasmonic response were firstly synthesized and validated as efficient dual LSPR-SERS nanosensors in solution using the p-aminothiophenol (p-ATP) analyte. GNRs were then efficiently immobilized onto the paper via the immersion approach, thus obtaining plasmonic nanoplatforms with a modulated LSPR response. The successful deposition of the nanoparticles onto the cellulose fibers was confirmed by LSPR measurements, which demonstrate the preserved plasmonic response after immobilization, as well as by dark-field microscopy and scanning electron microscopy investigations, which confirm their uniform distribution. Finally, a limit of detection for p-ATP as low as 10−12 M has been achieved by our developed SERS-based paper nanoplatform, proving that our optimized plasmonic paper-based biosensing design could be further considered as an excellent candidate for miniaturized biomedical applications.