Triangular gold nanoplates/two-dimensional nano mica platelets with a 3D lightning-rod effect as flexible nanohybrid substrates for SERS bacterial detection

Temperature Sensitive PNIPAm-g-PEI/Gold Nanotriangle for Gene Delivery Promotion

As a two-dimensional material, gold nanotriangles (GNTs) are rarely studied in the field of gene delivery. In this study, a temperature-responsive GNTs was developed as a novel carrier for gene delivery. The temperature-sensitive copolymer PNIPAm-g-PEI was grafted onto the surface of GNTs to construct a PNIPAm-g-PEI/GNTs composite controllable release platform. The lower critical solution temperature (LCST) of PNIPAm-g-PEI/GNTs was found to be 42 °C, and the particle size of PNIPAm-g-PEI/GNTs was 150 nm at this temperature. Gel electrophoresis experiments showed that PNIPAm-g-PEI/GNTs completely condensed DNA at 20 μg/mL, and PNIPAm-g-PEI/GNTs promoted the release of DNA under laser irradiation. Luciferase and green fluorescent protein reporter gene assays demonstrated that the transfection efficiency of PNIPAm-g-PEI/GNTs was 1.5 and 7.2 times that of PEI, respectively. These results demonstrated the promising potential of temperature-responsive GNTs as effective and safe gene delivery vectors.

Molecular Stratification and Treatment Monitoring of Lung Cancer Using a Small Extracellular Vesicle-Activated Nanocavity Architecture

Development of molecular diagnostics for lung cancer stratification and monitoring is crucial for the rational planning and timely adjustment of treatments to improve clinical outcomes. In this regard, we propose a nanocavity architecture to sensitively profile the protein signature on small extracellular vesicles (sEVs) to enable accurate, noninvasive staging and treatment monitoring of lung cancer. The nanocavity architecture is formed by molecular recognition through the binding of sEVs with the nanobox-based core-shell surface-enhanced Raman scattering (SERS) barcodes and mirrorlike, asymmetric gold microelectrodes. By imposing an alternating current on the gold microelectrodes, a nanofluidic shear force was stimulated that supported the binding of sEVs and the efficient assembly of the nanoboxes. The binding of sEVs further induced a nanocavity between the nanobox and the gold microelectrode that significantly amplified the electromagnetic field to enable the simultaneous enhancement of Raman signals from four SERS barcodes and generate patient-specific molecular sEV signatures. Importantly, evaluated on a cohort of clinical samples (n = 76) on the nanocavity architecture, the acquired patient-specific sEV molecular signatures achieved accurate identification, stratification, and treatment monitoring of lung cancer patients, highlighting its potential for transition to clinical utility.

Flexible nanohybrid substrates utilizing gold nanocubes/nano mica platelets with 3D lightning-rod effect for highly efficient bacterial biosensors based on surface-enhanced Raman scattering

In this study, gold nanocubes (AuNCs) were quickly synthesized using the seed-mediated growth method and reduced onto the surface of two-dimensional (2D) delaminated nano mica platelets (NMPs), enabling the development of AuNCs/NMPs nanohybrids with a 3D lightning-rod effect. First, the growth-solution amount can be changed to easily adjust the AuNCs average-particle size within a range of 30-70 nm. The use of the cationic surfactant cetyltrimethylammonium chloride as a protective agent allowed the surface of AuNCs and nanohybrids to be positively charged. Positively charged nanohybrid surfaces presented a good adsorption effect for detecting molecules with negative charges on the surface. Additionally, the NMP surfaces were rich in ionic charges and provided a large specific surface area for stabilizing the growth of AuNCs. Delaminated AuNCs/NMPs nanohybrids can generate a 3D hotspot effect through self-assembly to enhance the Raman signal. Surface-enhanced Raman scattering (SERS) is highly sensitive in detecting adenine biomolecules. Its limit of detection (LOD) and Raman enhancement factor reached 10-9 M and 3.6 × 108, respectively. Excellent reproducibility was obtained owing to the relatively regular arrangement of AuNC particles, and the relative standard deviation (RSD) was 10.7%. Finally, the surface of NMPs was modified by adding the hydrophilic poly(oxyethylene)-diamine (POE2000) and amphiphilic PIB-POE-PIB copolymer at different weight ratios. The adjustment of the surface hydrophilicity and hydrophobicity of AuNCs/NMPs nanohybrids led to better adsorption and selectivity for bacteria. AuNCs/POE/NMPs and AuNCs/PIB-POE-PIB/NMPs were further applied to the SERS detection of hydrophilic Staphylococcus aureus and hydrophobic Escherichia coli, respectively. The SERS-detection results suggest that the LOD of hydrophilic Staphylococcus aureus and hydrophobic Escherichia coli reached 92 CFU mL-1 and 1.6 × 102 CFU mL-1, respectively. The AuNCs/POE/NMPs and AuNCs/PIB-POE-PIB/NMPs nanohybrids had different hydrophilic-hydrophobic affinities, which greatly improved the selectivity and sensitivity for detecting bacteria with different hydrophilicity and hydrophobicity. Therefore, fast, highly selective, and highly sensitive SERS biological-detection results were obtained.

Application of Nanohybrid Substrates with Layer-by-Layer Self-Assembling Properties to High-Sensitivity Surface-Enhanced Raman Scattering Detection

The present study was conducted to prepare and investigate large-area, high-sensitivity surface-enhanced Raman scattering (SERS) substrates. Organic/inorganic nanohybrid dispersants consisting of an amphiphilic triblock copolymer (hereafter referred to simply as "copolymer") and graphene oxide (GO) were used to stabilize the growth and size of gold nanoparticles (AuNPs). Ion-dipole forces were present between the AuNPs and copolymer dispersants, while the hydrogen bonds between GO and the copolymer prevented the aggregation of GO, thereby stabilizing the AuNP/GO nanohybrids. Transmission electron microscopy (TEM) revealed that the AuNPs had particle sizes of 25-35 nm and a relatively uniform size distribution. The AuNP/GO nanohybrids were deposited onto the glass substrate by using the solution drop-casting method and employed for SERS detection. The self-assembling properties of two-dimensional sheet-like GO led to a regular lamellar arrangement of AuNP/GO nanohybrids, which could be used for the preparation of large-area SERS substrates. Following removal of the copolymer by annealing at 300 °C for 2 h, measurements were obtained under scanning electron microscopy. The results confirmed that 2D GO nanosheets were capable of stabilizing AuNPs, with the final size reaching approximately 40 nm. These AuNPs were adsorbed on both sides of the GO nanosheets. Because the GO nanosheets were merely 5 nm-thick, a good three-dimensional hot-junction effect was generated along the z-axis of the AuNPs. Lastly, the prepared material was used for the SERS detection of rhodamine 6G (R6G), a commonly used highly fluorescent dye. An enhancement factor (EF) of up to 3.5 × 106 was achieved, and the limit of detection was approximately 10-10 M. Detection limits of 10-10 M and < 10-10 M were also observed with the detection of Direct Blue 200 and the biological molecule adenine. It is therefore evident that AuNP/copolymer/GO nanohybrids are large-area flexible SERS substrates that hold great potential in environmental monitoring and biological system detection applications.