Au nanolenses for near-field focusing

Customized Self-Assembled Gold Nanoparticle-DNA Origami Composite Templates for Shape-Directed Growth of Plasmonic Structures

The metal plasmonic nanostructure has the optical property of plasmon resonance, which holds great potential for development in nanophotonics, bioelectronics, and molecular detection. However, developing a general and straightforward method to prepare metal plasmonic nanostructures with a controllable size and morphology still poses a challenge. Herein, we proposed a synthesis strategy that utilized a customizable self-assembly template for shape-directed growth of metal structures. We employed gold nanoparticles (AuNPs) as connectors and DNA nanotubes as branches, customizing gold nanoparticle-DNA origami composite nanostructures with different branches by adjusting the assembly ratio between the connectors and branches. Subsequently, various morphologies of plasmonic metal nanostructures were created using this template shape guided strategy, which exhibited enhancement of surface-enhanced Raman scattering (SERS) signals. This strategy provides a new approach for synthesizing metallic nanostructures with multiple morphologies and opens up another possibility for the development of customizable metallic plasmonic structures with broader applications.

Plasmonic Annular Nanotrenches with 1 nm Nanogaps for Detection of SARS-CoV-2 Using SERS-Based Immunoassay

This study represents the synthesis of a novel class of nanoparticles denoted as annular Au nanotrenches (AANTs). AANTs are engineered to possess embedded, narrow circular nanogaps with dimensions of approximately 1 nm, facilitating near-field focusing for detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) via a surface-enhanced Raman scattering (SERS)-based immunoassay. Notably, AANTs exhibited an exceedingly low limit of detection (LOD) of 1 fg/mL for SARS-CoV-2 spike glycoproteins, surpassing the commercially available enzyme-linked immunosorbent assay (ELISA) by 6 orders of magnitude (1 ng/mL from ELISA). To assess the real-world applicability, a study was conducted on 50 clinical samples using an SERS-based immunoassay with AANTs. The results revealed a sensitivity of 96% and a selectivity of 100%, demonstrating the significantly enhanced sensing capabilities of the proposed approach in comparison to ELISA and commercial lateral flow assay kits.

Determination of H2O2 and its antioxidant activity by BCM@Au NPs ratiometric SERS sensor

As a reactive oxygen species (ROS), excessive production of H2O2 contributes to the development of several diseases such as, inflammation, cancer, and respiratory diseases. Supplementation with endogenous or exogenous antioxidants can scavenge ROS and reduce the oxidation of cellular molecules, thus alleviating the generation of diseases. Therefore, the determination of H2O2 content and its antioxidant activity is of great importance in disease diagnosis and treatment. In this paper, a ratiometric SERS sensor with a flexible cellulose membrane was designed for quantitative detection of H2O2 and assessment of antioxidant activity. First, gold seeds were reduced on bacterial cellulose membrane (BCM) and Au NPs were smoothly deposited on the bacterial cellulose membrane (BCM) using halides to reduce the reduction potential in the growth solution to form a flexible BCM@Au NPs SERS substrate. Afterwards, the oxidation of H2O2 was used to convert 3-mercaptophenylboronic acid (3-MPBA) to the corresponding phenol form 3-hydroxyphenylethanol (3-HTP). The change of substance resulted in a good linear relationship between the intensity ratio corresponding to the two Raman shifts of 881 cm-1 and 995 cm-1 and the H2O2 concentration with a detection limit of 0.0186 μM. This opens up a new method for the detection of H2O2 with high sensitivity and accuracy. In addition, this SERS platform was successfully used for the determination of antioxidant activity. It is promising to be applied to disease diagnosis and efficacy evaluation.

Gene Therapy Using Efficient Direct Lineage Reprogramming Technology for Neurological Diseases

Gene therapy is an innovative approach in the field of regenerative medicine. This therapy entails the transfer of genetic material into a patient's cells to treat diseases. In particular, gene therapy for neurological diseases has recently achieved significant progress, with numerous studies investigating the use of adeno-associated viruses for the targeted delivery of therapeutic genetic fragments. This approach has potential applications for treating incurable diseases, including paralysis and motor impairment caused by spinal cord injury and Parkinson's disease, and it is characterized by dopaminergic neuron degeneration. Recently, several studies have explored the potential of direct lineage reprogramming (DLR) for treating incurable diseases, and highlighted the advantages of DLR over conventional stem cell therapy. However, application of DLR technology in clinical practice is hindered by its low efficiency compared with cell therapy using stem cell differentiation. To overcome this limitation, researchers have explored various strategies such as the efficiency of DLR. In this study, we focused on innovative strategies, including the use of a nanoporous particle-based gene delivery system to improve the reprogramming efficiency of DLR-induced neurons. We believe that discussing these approaches can facilitate the development of more effective gene therapies for neurological disorders.

Bimetallic alloy Ag@Au nanorings with hollow dual-rims focus near-field on circular intra-nanogaps

Here, we report a highly sensitive and reliable surface enhanced Raman scattering (SERS)-based immunoassay using bimetallic alloy Ag@Au hollow dual-rim nanorings (DRNs) where two hollow nanorings with different diameters are concentrically overlapped and connected by thin metal ligaments, forming circular hot-zones in the intra-nanogaps between the inner and outer rims. Pt DRNs were first prepared, and then Ag was deposited on the surface of the Pt skeleton, followed by Au coating, resulting in alloy Ag@Au hollow DRNs. The chemical stability of Au and the high optical properties of Ag are incorporated into a single entity, Ag@Au hollow DRNs, enabling strong single-particle SERS activity and biocompatibility through surface modification with thiol-containing functionalities. When Ag@Au hollow DRNs were utilized as nanoprobes for detecting human chorionic gonadotropin (HCG) hormone through a SERS-based immunoassay, a very low limit of detection of 10 pM with high reliability was achieved, strongly indicating their advantage as ultrasensitive SERS nanoprobes.

Heterogeneous Component Au (Outer)-Pt (Middle)-Au (Inner) Nanorings: Synthesis and Vibrational Characterization on Middle Pt Nanorings with Surface-Enhanced Raman Scattering

We report a synthetic approach for heterometallic (Au-Pt-Au) nanorings with intertwined triple rings (NITs), wherein three differently sized metal circular nanorings concentrically overlap in a single entity. The synthetic method allows one to control the component of core nanorings (Au or Pt) with a tunable gap distance. The narrow circular nanogaps between inner and outer Au rings strongly enhance the electromagnetic near-field via intraparticle coupling of localized surface plasmon resonance, which realizes surface-enhanced Raman scattering (SERS) at the single-particle level. Importantly, when the component of the middle ring is Pt, in situ SERS measurement for electrochemical reactions on Pt domains could be monitored with electrochemical potential variations due to the near-field focusing that is assisted by plasmonically active inner and outer Au nanorings, which is not feasible with pure Pt nanoparticle systems. The resulting NIT systems are robust and may benefit the synthesis of complicated nanostructures, giving myriad applications.

Synthesis of morphology controlled PtAu@Ag nanorings through concentric and eccentric growth pathways

We report the synthetic methodology for silver nanorings with controlled nanoscale morphology. The morphology of Ag nanorings was kinetically controlled by electrochemical potential tuning of Ag deposition using halide counter-ions, which resulted in concentric PtAu@Ag nanorings (i.e., Ag homogeneously wrapped around the Pt nanorings) and eccentric PtAu@Ag nanorings (i.e., Ag selectively deposited at the inner boundary of the Pt nanorings). The resulting high quality of each Ag nanoring allowed us to systematically investigate their corresponding localized surface plasmon resonance (LSPR) profiles as a function of their geometrical parameters. Additionally, we evaluated the application of the samples as surface-enhanced Raman spectroscopy (SERS) substrates composed of 2D monolayers of varied compositions of Ag and Au nanorings, which showed a different extent of enhancement depending on the adsorption characteristics of the analytes.