PLLA Nanofibrous Paper-Based Plasmonic Substrate with Tailored Hydrophilicity for Focusing SERS Detection

We report a new paper-based surface enhanced Raman scattering (SERS) substrate platform contributed by a poly­(l-lactic acid) (PLLA) nanofibrous paper adsorbed with plasmonic nanostructures, which can circumvent many challenges of the existing SERS substrates. This PLLA nanofibrous paper has three-dimensional porous structure, extremely clean surface with good hydrophobicity (contact angle is as high as 133.4°), and negligible background interference under Raman laser excitation. Due to the strong electrostatic interaction between PLLA nanofiber and cetyltrimethylammonium bromide (CTAB) molecules, the CTAB-coated gold nanorods (GNRs) are efficiently immobilized onto the fibers. Such a hydrophobic paper substrate with locally hydrophilic SERS-active area can confine analyte molecules and prevent the random spreading of molecules. The confinement leads to focusing effect and the GNRs-PLLA SERS substrate is found to be highly sensitive (0.1 nM Rhodamine 6G and malachite green) and exhibit excellent reproducibility (∼8% relative standard deviation (RSD)) and long-term stability. Furthermore, it is also cost-efficient, with simple fabrication methodology, and demonstrates high sample collection efficiency. All of these benefits ensure that this GNRs-PLLA substrate is a really perfect choice for a variety of SERS applications

DataSheet1_Nrf2−/− regulated lung DNA demethylation and CYP2E1 DNA methylation under PM2.5 exposure.docx

Cytochrome P450 (CYP450) can mediate fine particulate matter (PM2.5) exposure leading to lung injury. Nuclear factor E2-related factor 2 (Nrf2) can regulate CYP450 expression; however, the mechanism by which Nrf2−/− (KO) regulates CYP450 expression via methylation of its promoter after PM2.5 exposure remains unclear. Here, Nrf2−/− (KO) mice and wild-type (WT) were placed in a PM2.5 exposure chamber (PM) or a filtered air chamber (FA) for 12 weeks using the real-ambient exposure system. The CYP2E1 expression trends were opposite between the WT and KO mice following PM2.5 exposure. After exposure to PM2.5,CYP2E1 mRNA and protein levels were increased in WT mice but decreased in KO mice, and CYP1A1 expression was increased after exposure to PM2.5 in both WT and KO mice. CYP2S1 expression decreased after exposure to PM2.5 in both the WT and KO groups. We studied the effect of PM2.5 exposure on CYP450 promoter methylation and global methylation levels in WT and KO mice. In WT and KO mice in the PM2.5 exposure chamber, among the methylation sites examined in the CYP2E1 promoter, the CpG2 methylation level showed an opposite trend with CYP2E1 mRNA expression. The same relationship was evident between CpG3 unit methylation in the CYP1A1 promoter and CYP1A1 mRNA expression, and between CpG1 unit methylation in the CYP2S1 promoter and CYP2S1 mRNA expression. This data suggests that methylation of these CpG units regulates the expression of the corresponding gene. After exposure to PM2.5, the expression of the DNA methylation markers ten-eleven translocation 3 (TET3) and 5-hydroxymethylcytosine (5hmC) was decreased in the WT group but significantly increased in the KO group. In summary, the changes in CYP2E1, CYP1A1, and CYP2S1 expression in the PM2.5 exposure chamber of WT and Nrf2−/− mice might be related to the specific methylation patterns in their promoter CpG units. After exposure to PM2.5, Nrf2 might regulate CYP2E1 expression by affecting CpG2 unit methylation and induce DNA demethylation via TET3 expression. Our study revealed the underlying mechanism for Nrf2 to regulate epigenetics after lung exposure to PM2.5.</p

Metabolizable Small Gold Nanorods: Size-dependent Cytotoxicity, Cell Uptake and <i>In Vivo</i> Biodistribution

Gold nanorods (AuNRs) with unique plasmonic properties in the near-infrared region have promising biomedical applications but suffer from poor <i>in vivo</i> clearance because of the large size. In this study, small AuNRs with a diameter of 7 nm (designated as sAuNRs) are found to have low toxicity and high clearance rates <i>in vivo</i>. Compared to common AuNRs with a diameter of 14 nm (designated as bAuNRs), sAuNRs exhibit similar surface plasmon resonance bands and photothermal efficiency as bAuNRs but have lower cytotoxicity as well as higher cell uptake. The <i>in vivo</i> biodistribution study indicates that only 0.68% of the intravenously injected sAuNRs remain in the body after 30 days, but the residual amount in the body after injection of bAuNRs is as high as 12.3%. The results demonstrate that the smaller AuNRs having lower toxicity and increased clearance <i>in vivo</i> have large clinical potential

Efficient Enrichment and Self-Assembly of Hybrid Nanoparticles into Removable and Magnetic SERS Substrates for Sensitive Detection of Environmental Pollutants

A structure consisting of a low surface energy substrate and low surface tension liquid is designed and prepared by taking advantage of perfluorinated fluid infusion into the porous Teflon membrane. This slippery platform allows efficient enrichment and self-assembly of hybrid nanoparticles and the assembled structure can be detached from the membrane. A macroscale superlattice array of Au nanorods doped with magnetic Fe₃O₄ nanoparticles is obtained by suppressing the outward capillary flow and coffee-ring effect during evaporative self-assembly. In SERS (surface enhanced Raman scattering) detection of environmental pollutants including thiram, diquat and polycyclic aromatic hydrocarbons, the removable plasmonic superlattice array with magnetic properties enables rapid separation of analytes from the solution resulting in excellent sensitivity and detection limits down to the nanomolar level. The self-assembly strategy shows great potential in the fabrication of removable 3D plasmonic superlattice arrays for SERS detections