Nrf2-/- regulated lung DNA demethylation and CYP2E1 DNA methylation under PM2.5 exposure.

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.

Phosphoproteomics Reveals the Wolframin-Calcium Axis as an Important Pathogenic Signaling Node in Primary Aldosteronism.

BACKGROUND: Aldosterone-producing adenoma (APA) is a benign adrenal tumor with autonomous aldosterone production which causes hypertension and excess cardiovascular risk. Protein phosphorylation regulates aldosterone secretion from adrenal cortical cells, but how signaling networks are remodeled in APA remains unknown. METHODS: We performed an integrated proteomic and phosphoproteomic profiling of 15 APA and 10 matched nonfunctioning adrenocortical tumors (NFAT) based on the 4-dimensional label-free technique. We further validated our main findings in enlarged APA samples, mice, and adrenocortical cell line. RESULTS: The proteomic and phosphoproteomic profiling of APA and NFAT quantified 5989 proteins and 9011 phosphopeptides. We highlighted differentially expressed and phosphorylated proteins which modulated aldosterone synthesis and secretion from APA. As intracellular calcium is the central signal for aldosterone synthesis, our integrated calcium signaling network implicated wolframin in the control of calcium influx and CYP11B2 (aldosterone synthase) activation in APA (ratio of wolframin expression in APA to NFAT: 6.411, P<0.001). Among 97 APA cases for validation, a higher expression level of wolframin was associated with a higher plasma aldosterone concentration postcaptopril challenge test and a higher systolic blood pressure. In vitro, the secretion of aldosterone was enhanced by wolframin overexpression, while aldosterone secretion in response to potassium or angiotensin II was inhibited by the knockdown of wolframin. Further in vivo and in vitro data demonstrated the wolframin-calcium axis as an important regulator of CYP11B2 expression and aldosterone production. CONCLUSIONS: Wolframin is a regulatory protein in aldosterone hypersecretion. Remodeled calcium transportation and mitochondrial function are involved in wolframin-related aldosterone secretion.

Metabolic dysfunction associated fatty liver disease: The new nomenclature and its impact.

BACKGROUND: In 2020, an international expert panel proposed a new definition of fatty liver: Metabolic dysfunction-associated fatty liver disease (MAFLD). The MAFLD added the criteria for defining metabolic dysfunctions, which are high-risk factors for liver-related and cardiovascular events. Contrary to the non-alcoholic fatty liver disease (NAFLD) definition, it allows the coexistence of MAFLD and significant alcohol use in the same patient. AIM: To review the existing data that evaluate the clinical profile and long-term outcome difference between the patients identified as MAFLD and NAFLD. METHODS: Databases MEDLINE via PubMed and EMBASE were searched and relevant publications up to June 28, 2022 were assessed. Studies were included if they involved human participants diagnosed with MAFLD. RESULTS: A total of 2324 records were reviewed, of which 1575 duplicate citations were removed. Of the 2324 records screened, 207 articles were excluded, and 542 articles were assessed for their eligibility, for which 511 were excluded. The remaining 31 articles were selected for review. MAFLD diagnostic criteria were able to identify more individuals with fatty liver. Studies have shown that patients included using the MAFLD criteria were associated with higher risks of hepatic fibrosis when compared to NAFLD. All-cause mortality, cardiovascular disease-related, and cancer-related mortality were shown to be higher in MAFLD patients. MAFLD patients also had higher baseline metabolic derangement, and risks of developing obesity, diabetes, and cardiovascular events. Of the 3 subtypes, diabetes mellitus has the strongest association with negative outcomes, followed by metabolic dysfunction and elevated body mass index. Within the subtypes of MAFLD, patients with more metabolic conditions at the time of diagnosis had worse hepatic and liver injury compared to those with a single metabolic condition. CONCLUSION: MAFLD is a new definition of fatty liver disease that is gaining increasing acceptance. It is based on empirical clinical practice on positive inclusion of metabolic risk factors and recent evidence suggests that it helps to identify patients with higher risk for liver-related as well as cardiovascular events.

Nondestructive analysis of rolling contact fatigue cracks using induced scanning thermography.

Rolling contact fatigue (RCF) produced by wheel-rail interaction is now considered to be a critical factor that causes failure. Throughout this work, induced scanning thermography (IST) for detecting RCF defects at different depths is investigated. The original thermal sequences could not utilize the features at the heat dissipation stage; thus, a data reconstruction method, including principal component analysis (PCA) and Tucker factorization, was employed to extract the spatial and time patterns. In addition, detectability was evaluated across a range of speed studies. The Tucker-PCA combination algorithms obtained defects with improved quality, showing a clear boundary over the velocity range of 1-4km/h, which dramatically suppressed background noise. A unique gradient response characteristic in the cooling phase was summarized and utilized through experimental verification in order to recognize defect width.

GLIS3 mediated by the Rap1/PI3K/AKT signal pathway facilitates real-ambient PM2.5 exposure disturbed thyroid hormone homeostasis regulation.

Exposure to fine particulate matter (PM2.5) could damage multiple organs and systems. Recent epidemiological studies have shown that PM2.5 can disrupt dynamic balance of thyroid hormone (TH). However, the underlying mechanism by which PM2.5 interferes with TH remains unclear. This study evaluated the role of Gli-similar3 (GLIS3) in the effect of PM2.5 on TH synthesis in mice using a real-ambient exposure system, in Shijiazhuang City, Hebei Province. The PM2.5exposure group (PM) and filtered air group (FA) were placed in the exposure device for four and eight weeks. The results showed that the PM2.5 exposure altered the structure of the thyroid gland. Moreover, after PM2.5 exposure for eight weeks, the exposure level of free thyroxine (FT4) increased and the expression level of thyroid stimulating hormone (TSH) decreased in serum of mice. In addition, PM2.5 exposure significantly increased the expression of proteins related to thyroid hormone synthesis, such as sodium iodide transporter (NIS), thyroid peroxidase (TPO) and thyroglobulin (TG). Next, we found that GLIS3 and thyroid transcription factor Paired box 8 (PAX8) also increased after PM2.5 exposure. In order to further explore the potential molecular mechanism, we carried out transcriptome sequencing. KEGG analysis of the top 10 pathways revealed that the Ras-associated protein 1 (Rap1) signaling pathway could activate transcription factors and is related to thyroid cell survival. Additionally, PM2.5 exposure significantly increased the protein levels of Rap1 and its active form (Rap1 +GTP). We speculate that the active state of Rap1 is believed to be involved in activating the expression of transcription factor GLIS3. In conclusion, PM2.5 exposure induces histological changes in the thyroid gland and thyroid dysfunction in mice. The exposure activates GLIS3 through the Rap1/PI3K/AKT pathway to promote the expression of proteins related to thyroid hormone synthesis, leading to increased dysregulating TH homeostasis.

Value of passive anterior tibial subluxation on axial MRI in identifying anterior cruciate ligament functional deficiency in patients with advanced anteromedial osteoarthritis of the knee: a case-control study.

BACKGROUND: A functionally deficient anterior cruciate ligament (ACL) is considered one of the contraindications in unicompartmental knee arthroplasty (UKA). But there is still a lack of standardized and reproducible methods to assess ACL functional integrity in patients with advanced anteromedial osteoarthritis of the knee (AMOA). This study explores the value of passive anterior tibial subluxation (PATS) on axial MRI in evaluating ACL status in this population. METHODS: Patients who met UKA indications between November 2017 and September 2020 were included and grouped into "intact" (ACLI) or "deficient" (ACLD) group according to their ACL status during surgery. All participants underwent MRI with a standardized protocol. The measurements of medial and lateral PATS were conducted on axial MRI, and the mean of them was calculated as global PATS. Then the reliability and diagnostic ability of PATS were determined. RESULTS: A total of 85 patients (45 for ACLI group, 40 for ACLD group) were included after selection. The measurements of PATS showed excellent intra- and inter-observer reliabilities (with an intraclass correlation coefficient of at least 0.986). The global PATS of the ACLI group was significantly lower than that of the ACLD group (- 2.30 ± 1.96 vs. 1.03 ± 1.96 mm, P<0.0001). The diagnostic ability of global PATS was good (area under the curve = 0.897), and a threshold of 1.2 mm had a specificity of 100%, a sensitivity of 55%, and an accuracy of 78.82%. CONCLUSION: An axial global PATS of 1.2 mm on MRI is greatly specific for identifying a functionally deficient ACL in patients with advanced AMOA.

Prevalence and Risk Factors of Osteoporosis in Chinese Postmenopausal Women Awaiting Total Knee Arthroplasty.

BACKGROUND: Total knee arthroplasty (TKA) complications associated with low bone quality are challenging for orthopaedic surgeons to treat, but little is known about bone quality in Chinese postmenopausal women awaiting TKA. This study investigated the incidence of osteoporosis (OP) and explored the preoperative risk factors for OP in this population. METHODS: We retrospectively reviewed the data of Chinese postmenopausal women who were indicated for TKA between May 2017 and June 2020. The bone mineral density (BMD) of the hip and lumbar spine and multiple preoperative parameters were collected and analyzed. Binary logistic regression analysis was performed to identify independent risk factors for OP in this population. RESULTS: A total of 204 postmenopausal women with advanced knee OA were included in the study (age: 69.7±8.5 years; body mass index [BMI]: 25.5±4.0 kg/m2). The OP prevalence among all participants was 59.8%, and the patients aged 60-80 years had a significantly lower BMD than did the age/ethnicity-adjusted population. An age ≥60 years, a BMI<25, and the presence of a varus knee deformity were independent risk factors for preoperative OP in the postmenopausal women awaiting TKA. CONCLUSION: The prevalence of OP in Chinese postmenopausal women awaiting TKA is higher than that in the age/ethnicity-adjusted normal population. An age ≥60 years, a BMI<25, and the presence of a varus knee deformity are independent risk factors that can be used to predict preoperative OP in this population.

Effects of Ion Energy and Density on the Plasma Etching-Induced Surface Area, Edge Electrical Field, and Multivacancies in MoSe2 Nanosheets for Enhancement of the Hydrogen Evolution Reaction.

Plasma functionalization can increase the efficiency of MoSe2 in the hydrogen evolution reaction (HER) by providing multiple species but the interactions between the plasma and catalyst are not well understood. In this work, the effects of the ion energy and plasma density on the catalytic properties of MoSe2 nanosheets are studied. The through-holes resulting from plasma etching and multi-vacancies induced by plasma-induced damage enhance the HER efficiency as exemplified by a small overpotential of 148 mV at 10 mA cm-2 and Tafel slope of 51.6 mV dec-1 after the plasma treatment using a power of 20 W. The interactions between the plasma and catalyst during etching and vacancies generation are evaluated by plasma simulation. Finite element and first-principles density functional theory calculations are also conducted and the results are consistent with the experimental results, indicating that the improved HER catalytic activity stems from the enhanced electric field and more active sites on the catalyst, and reduced bandgap and adsorption energy arising from the etched through-holes and vacancies, respectively. The results convey new fundamental knowledge about the plasma effects and means to enhance the efficiency of catalysts in water splitting as well insights into the design of high-performance HER catalysts.

Ecofriendly and Biodegradable Soybean Protein Isolate Films Incorporated with ZnO Nanoparticles for Food Packaging.

ZnO nanoparticles (ZnONPs) are synthesized and incorporated into soybean protein isolate (SPI) to obtain SPI/ZnONPs (SZ) films, and the morphology, size distribution, and stability are determined. The effects of different contents of ZnONPs in the SZ films on the oxygen barrier, antibacterial activity, and thermal and mechanical properties are evaluated. A ZnONPs content of 0.2% in the SZ films improves the tensile strength and microbial inhibition by 231% and 16%, respectively. The thermal stability and oxygen barrier properties of the SZ films are also enhanced with addition of ZnONPs. The ZnONPs dispersed uniformly in the SPI film enhance the interactions between SPI molecules via hydrogen bonding, and the results suggest potential application of ZnONPs in food packaging.

Degradable and Photocatalytic Antibacterial Au-TiO2/Sodium Alginate Nanocomposite Films for Active Food Packaging.

A degradable and antibacterial sodium alginate film containing functional Au-TiO2 nanocomposites for food packaging was successfully developed. The Au-TiO2 nanocomposites are synthesized hydrothermally and mixed with the alginate solution to form the film by a casting method. The Au-TiO2 nanocomposites enable the film with excellent visible light absorption and transfer ability with the light absorption rang covering UV⁻visible wavelength (300⁻800 nm) and induce the increase of the film water contact angle from 40° to 74°, which contributes to the film shape stability. Furthermore, compared to the TiO2 nanoparticle-incorporated film, the antibacterial ability of Au-TiO2/sodium alginate composite film is improved approximately by 60% and 50% against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli), respectively, in light conditions. The antibacterial property of the film arises from the increased production of reactive oxygen species (ROS) induced by the surface plasmonic resonance of Au nanoparticles. The degradable and antibacterial properties render the composite film of great application potential in food packaging industry.

Liquid L-thyroxine versus tablet L-thyroxine in patients on L- thyroxine replacement or suppressive therapy: a meta-analysis.

PURPOSE: To compare the effectiveness of liquid L-T4 (L-thyroxine) and tablet L-T4 in patients on L-T4 replacement or suppressive therapy. METHODS: The Cochrane Library, PubMed, Embase, and Web of Science databases were searched to identify relevant articles. All prospective or randomized controlled studies (RCTs) comparing liquid L-T4 and tablet L-T4 in patients on L-T4 replacement or suppressive therapy were included in the analysis. RESULTS: Overall, the initial search of the four databases identified 1278 published studies; of these, eight studies were ultimately included in the meta-analysis. TSH (thyroid stimulating hormone) levels were significantly suppressed in patients on liquid L-T4 compared with those on tablet L-T4, in patients on L-T4 suppressive therapy with L-T4 malabsorption (Mean Difference (MD) = -2.26, 95% Confidence Interval (CI): -3.59, -0.93; P = 0.0009)). However, liquid L-T4 and tablet L-T4 did not show a statistically significant difference in patients on L-T4 suppressive therapy without malabsorption (MD = 0.08, 95% CI: -0.31, 0.47; P = 0.69). TSH levels were significantly normalized in patients on liquid L-T4 compared with those on tablet L-T4, in Patients on L-T4 replacement therapy with L-T4 malabsorption (MD = -3.20, 95% CI: -5.08, -1.32; P = 0.0009). However, liquid L-T4 and tablet L-T4 did not show a statistically significant difference in patients on L-T4 replacement therapy without malabsorption (MD = 0.91, 95% CI: -0.03, 1.86; P = 0.06). CONCLUSION: Liquid L-T4 is more efficient than tablet L-T4 in patients on L-T4 replacement or suppressive therapy with malabsorption. No significant differences were observed in patients without malabsorption. Further studies should be conducted to verify these findings.

Bisphenol A is not associated with a 5-year incidence of type 2 diabetes: a prospective nested case-control study.

AIMS: The relationship between bisphenol A (BPA) and diabetes remains controversial. This study aims to investigate whether serum BPA level could predict the 5-year incidence of type 2 diabetes (T2D). METHODS: A nested case-control study was performed among Chinese who participated in the environment, inflammation and metabolic diseases study (2008-2013). Of the 3510 subjects who were free of diabetes, 232 subjects developed diabetes during the 5-year follow-up. Cases and controls were matched for age and gender by a ratio of 1:1. Homoeostasis model assessment was used to estimate basal ß-cell function (HOMA-ß) and insulin resistance (HOMA-IR). Participants were stratified into tertiles based on low, median and high baseline serum BPA levels. Regression models were used to analyze the relationship between serum BPA concentration and the incidence of T2D. RESULTS: At baseline, no significant difference in serum BPA concentration was observed between patients with T2D and controls [1.3 (0.3, 3.7) vs. 1.6 (0.4, 3.9) µmol/L, P = 0.199]; serum BPA concentration was positively associated with fasting plasma glucose (r = 0.27, P < 0.001); however, neither HOMA-ß nor HOMA-IR correlated with serum BPA concentration. During the follow-up, baseline BPA levels could not predict the 5-year T2D incidence, whether or not adjusted for the potential confounders such as body mass index and blood pressure. [Low BPA tertile was the reference, OR 0.66 (95% CI 0.30, 1.44) for median, OR 0.93 (95% CI 0.41, 2.13) for high.] CONCLUSION: BPA is not associated with a 5-year T2D incidence. These data do not support previous cross-sectional study that BPA exerted a detrimental effect on glucose metabolism.

Paecilomyces tenuipes extract prevents depression-like behaviors in chronic unpredictable mild stress-induced rat model via modulation of neurotransmitters.

The medicinal fungus Paecilomyces tenuipes exhibits a variety of pharmacological effects, including antidepressive effects. The chronic unpredictable mild stress (CUMS)­induced rat model has served an important role in studies involving antidepressants screening. The aim of the present study was to evaluate the antidepressant­like activity of P. tenuipes N45 aqueous extract (PTNE) in a CUMS­induced rat model of behavioral despair depression. Following 4 weeks of PTNE treatment, behavioral tests were conducted to investigate the antidepressant­like activities, and the levels of neurotransmitters and hormones in blood and hypothalamus were measured. The results demonstrated that PTNE treatment significantly increased movement in the forced running test, whereas the immobility time was reduced in the hotplate test and the forced swim test in depression­model rats. PTNE treatment was able to normalize the levels of hormones and neurotransmitters in serum and hypothalamus of CUMS rats. The data demonstrated that PTNE treatment may be a potential pharmaceutical agent in treatment­resistant depression, and the effects of PTNE may be partly mediated through normalizing the levels of neurotransmitters.

Cell-borne 2D nanomaterials for efficient cancer targeting and photothermal therapy.

Two of the challenges for clinical implementation of nano-therapeutic strategies are optimization of tumor targeting and clearance of the nanoagents in vivo. Herein, a cell-mediated therapy by transporting 2D Bi2Se3 nanosheets within macrophage vehicles is described. The Bi2Se3 nanosheets with excellent near-infrared photothermal performance exhibit high macrophage uptake and negligible cytotoxicity thus facilitating the fabrication of Bi2Se3-laden-macrophages. Compared with bare Bi2Se3, the Bi2Se3-laden-macrophages after intravenous injection show prolonged blood circulation and can overcome the hypoxia-associated drug delivery barrier to target the tumor efficiently and dramatically enhance the efficiency of photothermal cancer therapy. The Bi2Se3-laden-macrophages possess good biocompatibility as demonstrated by the biochemical and histological analyses and furthermore, most of the materials are excreted from the body within 25 days. Our findings reveal a desirable system for highly efficient near-infrared photothermal cancer therapy.

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.

Evaporative Self-Assembly of Gold Nanorods into Macroscopic 3D Plasmonic Superlattice Arrays.

Millimeter-scale 3D superlattice arrays composed of dense, regular, and vertically aligned gold nanorods are fabricated by evaporative self-assembly. The regular organization of the gold nanorods into a macroscopic superlattice enables the production of a plasmonic substrate with excellent sensitivity and reproducibility, as well as reliability in surface-enhanced Raman scattering. The work bridges the gap between nanoscale materials and macroscopic applications.

Metabolizable Small Gold Nanorods: Size-dependent Cytotoxicity, Cell Uptake and In Vivo Biodistribution.

Gold nanorods (AuNRs) with unique plasmonic properties in the near-infrared region have promising biomedical applications but suffer from poor in vivo 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 in vivo. 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 in vivo 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 in vivo have large clinical potential.

Small gold nanorods laden macrophages for enhanced tumor coverage in photothermal therapy.

One of the challenges to adopt photothermal ablation clinically is optimization of the agent delivery in vivo. Herein, a cell-mediated delivery and therapy system by employing macrophage vehicles to transport 7 nm diameter Au nanorods (sAuNRs) is described. Owing to the small size, the sAuNRs exhibit much higher macrophage uptake and negligible cytotoxicity in comparison with commonly used 14 nm diameter AuNRs to achieve healthy BSA-coated sAuNRs-laden-macrophages. By delivering BSA-coated sAuNRs to the entire tumor after intratumoral injection, the BSA-coated sAuNRs-laden-macrophages show greatly improved photothermal conversion almost everywhere in the tumor, resulting in minimized tumor recurrence rates compared to free BSA-coated sAuNRs. Our findings not only provide a desirable approach to improve the photothermal therapy efficiency by optimizing the intratumoral distribution of the agents, but also expedite clinical application of nanotechnology to cancer treatment.

Ultrasmall Black Phosphorus Quantum Dots: Synthesis and Use as Photothermal Agents.

Black phosphorus quantum dots (BPQDs) were synthesized using a liquid exfoliation method that combined probe sonication and bath sonication. With a lateral size of approximately 2.6 nm and a thickness of about 1.5 nm, the ultrasmall BPQDs exhibited an excellent NIR photothermal performance with a large extinction coefficient of 14.8 L g(-1) cm(-1) at 808 nm, a photothermal conversion efficiency of 28.4%, as well as good photostability. After PEG conjugation, the BPQDs showed enhanced stability in physiological medium, and there was no observable toxicity to different types of cells. NIR photoexcitation of the BPQDs in the presence of C6 and MCF7 cancer cells led to significant cell death, suggesting that the nanoparticles have large potential as photothermal agents.

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.