Asymmetric Core–Shell Gold Nanoparticles and Controllable Assemblies for SERS Ratiometric Detection of MicroRNA

Surface-enhanced Raman scattering sensing for detection and mapping of key cellular biomarkers

Cellular biomarkers mainly contain proteins, nucleic acids, glycans and many small molecules including small biomolecule metabolites, reactive oxygen species and other cellular chemical entities. The detection and mapping of the key cellular biomarkers can effectively help us to understand important cellular mechanisms associated with physiological and pathological processes, which greatly promote the development of clinical diagnosis and disease treatment. Surface-enhanced Raman scattering (SERS) possesses high sensitivity and is free from the influence of strong self-fluorescence in living systems as well as the photobleaching of the dyes. It exhibits rich and narrow chemical fingerprint spectra for multiplexed detection, and has become a powerful tool to detect and map cellular biomarkers. In this review, we present an overview of recent advances in the detection and mapping of different classes of cellular biomarkers based on SERS sensing. These advances fully confirm that the SERS-based sensors and sensing methods have great potential for the exploration of biological mechanisms and clinical applications. Additionally, we also discuss the limitations of present research and the future developments of the SERS technology in this field.

Formation of miRNA Nanoprobes-Conjugation Approaches Leading to the Functionalization

Recently, microRNAs (miRNA) captured the interest as novel diagnostic and prognostic biomarkers, with their potential for early indication of numerous pathologies. Since miRNA is a short, non-coding RNA sequence, the sensitivity and selectivity of their detection remain a cornerstone of scientific research. As such, methods based on nanomaterials have emerged in hopes of developing fast and facile approaches. At the core of the detection method based on nanotechnology lie nanoprobes and other functionalized nanomaterials. Since miRNA sensing and detection are generally rooted in the capture of target miRNA with the complementary sequence of oligonucleotides, the sequence needs to be attached to the nanomaterial with a specific conjugation strategy. As each nanomaterial has its unique properties, and each conjugation approach presents its drawbacks and advantages, this review offers a condensed overview of the conjugation approaches in nanomaterial-based miRNA sensing. Starting with a brief recapitulation of specific properties and characteristics of nanomaterials that can be used as a substrate, the focus is then centered on covalent and non-covalent bonding chemistry, leading to the functionalization of the nanomaterials, which are the most commonly used in miRNA sensing methods.

Paper-Based Fluidic Sensing Platforms for β-Adrenergic Agonist Residue Point-of-Care Testing

The illegal use of β-adrenergic agonists during livestock growth poses a threat to public health; the long-term intake of this medication can cause serious physiological side effects and even death. Therefore, rapid detection methods for β-adrenergic agonist residues on-site are required. Traditional detection methods such as liquid chromatography have limitations in terms of expensive instruments and complex operations. In contrast, paper methods are low cost, ubiquitous, and portable, which has led to them becoming the preferred detection method in recent years. Various paper-based fluidic devices have been developed to detect β-adrenergic agonist residues, including lateral flow immunoassays (LFAs) and microfluidic paper-based analytical devices (μPADs). In this review, the application of LFAs for the detection of β-agonists is summarized comprehensively, focusing on the latest advances in novel labeling and detection strategies. The use of μPADs as an analytical platform has attracted interest over the past decade due to their unique advantages and application for detecting β-adrenergic agonists, which are introduced here. Vertical flow immunoassays are also discussed for their shorter assay time and stronger multiplexing capabilities compared with LFAs. Furthermore, the development direction and prospects for the commercialization of paper-based devices are considered, shedding light on the development of point-of-care testing devices for β-adrenergic agonist residue detection.

Patchy metal nanoparticles with polymers: controllable growth and two-way self-assembly

We report a new design of polymer-patched gold nanoparticles (AuNPs) with controllable interparticle interactions in terms of their direction and strength. Patchy AuNPs (pAuNPs) are prepared through hydrophobicity-driven surface dewetting under deficient ligand exchange conditions. Using the exposed surface on pAuNPs as seeds, a highly controllable growth of AuNPs is carried out via seed-mediated growth while retaining the size of polymer domains. As guided by ligands, these pAuNPs can self-assemble directionally in two ways along the exposed surface (head-to-head) or the polymer-patched surface of pAuNPs (tail-to-tail). Control of the surface asymmetry/coverage on pAuNPs provides an important tool in balancing interparticle interactions (attraction vs. repulsion) that further tunes assembled nanostructures as clusters and nanochains. The self-assembly pathway plays a key role in determining the interparticle distance and therefore plasmon coupling of pAuNPs. Our results demonstrate a new paradigm in the directional self-assembly of anisotropic building blocks for hierarchical nanomaterials with interesting optical properties.

A Liquid Interfacial SERS Platform on a Nanoparticle Array Stabilized by Rigid Probes for the Quantification of Norepinephrine in Rat Brain Microdialysates

For the reliable determination of trace chemicals in the brain, we created a SERS platform based on a functionalized AuNPs array formed at a liquid/liquid interface in a uniform fashion over a large substrate area through ternary regulations for real-time quantification of trace norepinephrine (NE). The rigid molecule, 4-(thiophen-3-ylethynyl)-benzaldehyde (RP1) was designed and co-assembled at AuNPs with 4-mercaptophenylboronic acid (MPBA) to chemically define NE via dual recognition. Meanwhile, the rigid structure assembly of RP1 and MPBA efficiently fixed the interparticle gap, guaranteeing reproducible SERS analysis. Furthermore, the Raman peak of C≡C group in the silent region was taken as a response element to further improve the accuracy. Combined with microdialysis, this SERS platform was developed for in-the-field testing of NE in rat brain microdialysates following anxiety.