NIR-Active Gold Dogbone Nanorattles Impregnated in Cationic Dextrin Nanoparticles for Cancer Nanotheranostics.

Theranostic systems, which integrate therapy and diagnosis into a single platform, have gained significant attention as a promising approach for noninvasive cancer treatment. The field of image-guided therapy has revolutionized real-time tumor detection, and within this domain, plasmonic nanostructures have garnered significant attention. These structures possess unique localized surface plasmon resonance (LSPR), allowing for enhanced absorption in the near-infrared (NIR) range. By leveraging the heat generated from plasmonic nanoparticles upon NIR irradiation, target cancer cells can be effectively eradicated. This study introduces a plasmonic gold dogbone-nanorattle (AuDB NRT) structure that exhibits broad absorption in the NIR region and demonstrates a photothermal conversion efficiency of 35.29%. When exposed to an NIR laser, the AuDB NRTs generate heat, achieving a maximum temperature rise of 38 °C at a concentration of 200 µg/mL and a laser power density of 3 W/cm2. Additionally, the AuDB NRTs possess intrinsic electromagnetic hotspots that amplify the signal of a Raman reporter molecule, making them an excellent probe for surface-enhanced Raman scattering-based bioimaging of cancer cells. To improve the biocompatibility of the nanorattles, the AuDB NRTs were conjugated with mPEG-thiol and successfully encapsulated into cationic dextrin nanoparticles (CD NPs). Biocompatibility tests were performed on HEK 293 A and MCF-7 cell lines, revealing high cell viability when exposed to AuDB NRT-CD NPs. Remarkably, even at a low laser power density of 1 W/cm2, the application of the NIR laser resulted in a remarkable 80% cell death in cells treated with a nanocomposite concentration of 100 µg/mL. Further investigation elucidated that the cell death induced by photothermal heat followed an apoptotic mechanism. Overall, our findings highlight the significant potential of the prepared nanocomposite for cancer theranostics, combining effective photothermal therapy along with the ability to image cancer cells.

Plasmonic gold dogbone nanorattles sniff out trace molecules through surface enhanced Raman scattering.

In this study, a highly sensitive and efficient surface-enhanced Raman spectroscopy (SERS) substrate was developed using Au dogbone nanorattles (Au-DBNRTs) deposited on a 3D wrinkled polymeric heat shrink film. The plasmonic structures of Au-DBNRTs, which possess a solid gold dogbone-shaped core and a thin, porous gold shell, and Au nanorod nanorattles (Au-NRNRTs), which have a rod-shaped core, were synthesized and their SERS performance was evaluated. Au-DBNRTs exhibited better Raman signal enhancement. The substrate was used to detect the pesticide thiabendazole with a limit of detection of up to 10-8 M. The unique optical properties and geometry of the Au-DBNRT nanoparticles, which have portruding corners in the vicinity of the metal shell, along with the shrinkage of the film after heat treatment, led to the creation of a 3D surface morphology, resulting in the generation of plasmonic electromagnetic hot spots. The fabricated substrate achieved an enhancement factor of 2.77 × 1010 for BDT, and the detection limit was 10-13 M. The current work offers a simple, cost-effective, and sensitive SERS substrate design that has great potential for sensing and detecting trace analytes.

The Rise of Structurally Anisotropic Plasmonic Janus Gold Nanostars.

Nanostructures intrinsically possessing two different structural or functional features, often called Janus nanoparticles, are emerging as a potential material for sensing, catalysis, and biomedical applications. Herein, we report the synthesis of plasmonic gold Janus nanostars (NSs) possessing a smooth concave pentagonal morphology with sharp tips and edges on one side and, contrastingly, a crumbled morphology on the other. The methodology reported herein for their synthesis - a single-step growth reaction - is different from any other Janus nanoparticle preparation involving either template-assisted growth or a masking technique. Interestingly, the coexistence of lower- and higher-index facets was found in these Janus NSs. The general paradigm for synthesizing gold Janus NSs was investigated by understanding the kinetic control mechanism with the combinatorial effect of all the reagents responsible for the structure. The optical properties of the Janus NSs were realized by corelating their extinction spectra with the simulated data. The size-dependent surface-enhanced Raman scattering (SERS) activity of these Janus NSs was studied with 1,4-BDT as the model analyte. Finite-difference time-domain simulations for differently sized particles revealed the distribution of electromagnetic hot-spots over the particles resulting in enhancement of the SERS signal in a size-dependent manner.

Plasmonic 3-D wrinkled polymeric shrink film-based SERS substrates for pesticide detection on real-world surfaces.

The continuous and excessive use of agrochemicals for crop improvement and protection has raised widespread concern, as they exert adverse effects on human health and the local environment. Surface Enhanced Raman Spectroscopy (SERS) provides a method for the quick identification and detection of such hazardous substances in a short amount of time due to its properties of being robust, accurate, sensitive and non-destructive. Despite the fact that several SERS substrates have been developed, the bulk of them are ineffective in terms of sample collection or providing reproducible results. In this study, we showed that a 3-D wrinkled polymeric heat-shrink film coated with Au bead@Ag nanorods (silver nanorods) serves as a potential SERS substrate for trace analysis. The surface of the heat-shrink film became wrinkled after heating, and this, along with the spatial arrangement of nanoparticles, significantly enhances the Raman signal of the analytes. The fabricated SERS substrate was able to sense two model analytes 1,4-benzenedithiol (BDT) and 2-naphthalenethiol (NT) up to 10-13 M and 10-11 M concentrations. The fabricated substrate was also effective in sensing thiram down to 10-13 M concentration. Additionally, the SERS substrate was applied in a real-world setting for the detection of the pesticide thiram spiked onto apple skin surfaces. To collect the thiram residues, the substrate was simply swabbed across the surface of the apple. This allowed for the detection of thiram at concentrations as low as 10-9 M (1 ppb). The fabricated SERS substrate can thus detect analytes in an efficient, sensitive, dependable and accurate manner, allowing for the sensing of trace analytes like pesticides in a real-world environment.

Nanotechnology Toolkit for Combating COVID-19 and Beyond.

The outbreak of SARS-CoV-2 is unlikely to be contained anytime soon with conventional medical technology. This beckons an urgent demand for novel and innovative interventions in clinical protocols, diagnostics, and therapeutics; to manage the current "disease X" and to be poised to counter its successor of like nature if one were to ever arise. To meet such a demand requires more attention to research on the viral-host interactions and on developing expeditious solutions, the kinds of which seem to spring from promising domains such as nanotechnology. Inducing activity at scales comparable to the viruses themselves, nanotechnology-based preventive measures, diagnostic tools and therapeutics for COVID-19 have been rapidly growing during the pandemic. This review covers the recent and promising nanomedicine-based solutions relating to COVID-19 and how some of these are possibly applicable to a wider range of viruses and pathogens. We also discuss the type, composition, and utility of nanostructures which play various roles specifically under prevention, diagnosis, and therapy. Further, we have highlighted the adoption and commercialization of some the solutions by large and small corporations alike, as well as providing herewith an exhaustive list on nanovaccines.

Superior Peroxidase-Like Activity of Gold Nanorattles in Ultrasensitive H2 O2 Sensing and Antioxidant Screening.

Nanozymes are artificial enzyme systems which are easy to produce, highly stable and cost-effective in comparison to natural enzymes. Herein, we evaluated the peroxidase-like activity of gold nanorattles (Au NRTs) having a solid gold octahedron core and thin, porous cubic gold shell. We also prepared solid gold nanocubes and nanospheres of similar sizes and surface charge as that of Au NRTs and compared their activity with standard horse radish peroxidase (HRP). All the prepared nanostructures followed Michaelis-Menten kinetics as observed from their substrate concentration vs. initial reaction velocity plot using 3,3',5,5'-tetramethylbenzidine (TMB) as a substrate. The kinetic parameters and the catalytic efficiency for the peroxidase-like activity of the nanostructures and HRP were calculated, and it was observed that Au NRTs possess the best nanozymatic activity with lowest KM and highest catalytic efficiency (kcat /KM ). The better activity of Au NRTs compared with other nanostructures and HRP could be attributed to the hollow porous structure with a solid core where different surfaces are available for reaction. Au NRTs, being the best amongst the tested nanozymes were further used for the sensing of hydrogen peroxide (H2 O2 ) and were found to sense H2 O2 down to 0.5 µM. Further, two naturally occurring antioxidants, tannic acid and ascorbic acid showed inhibitory effect on the peroxidase-like activity of Au NRTs in a concentration dependent manner which can be further used for screening of antioxidants or for determining the antioxidant potential.

Novel electrochemical biosensor for serotonin detection based on gold nanorattles decorated reduced graphene oxide in biological fluids and in vitro model.

Abnormal level of serotonin (ST) in body fluids is related to various clinical conditions including behavioral and psychotic disorders; hence its fast detection in clinically relevant ranges have tremendous importance in medical science. In view of this, we have developed a novel biosensor for ST detection using Au-nanorattles (AuNRTs)- reduced graphene oxide (rGO) nanocomposite coated on to the gold nanoparticles (AuNPs) deposited glassy carbon electrode (GCE). The nanocomposite/sensor probe was characterized using UV-Vis, TEM, SAED, EDX, AFM, and electrochemical techniques including LSV and EIS. Thereafter, the suitability of fabricated GCE/AuNPs/AuNRTs-rGO-Naf sensor probe was applied for ST determination which showed a linear dynamic range (LDR) of 3 × 10-6 - 1 × 10-3 M and the detection limit (DL) of 3.87 (±0.02) ×10-7 (RSD < 4.2%) M, which falls in the ranges of normal as well as various abnormal pathophysiological conditions. The designed sensor is successfully applied to detect ST in various real matrices viz. urine, blood serum, and in vitro model to show its direct clinical/practical applicability. Interferences due to the coexisting molecules were assessed and the long-term stability of the designed sensor was also examined which was found to be 8 weeks.