Compact In Situ Electrochemical NMR with Wireless and Anti-interference Strategy in Multiscenario Applications.

The integration of electrochemistry with nuclear magnetic resonance (NMR) spectroscopy recently offers a powerful approach to understanding oxidative metabolism, detecting reactive intermediates, and predicting biological activities. This combination is particularly effective as electrochemical methods provide excellent mimics of metabolic processes, while NMR spectroscopy offers precise chemical analysis. NMR is already widely utilized in the quality control of pharmaceuticals, foods, and additives and in metabolomic studies. However, the introduction of additional and external connections into the magnet has posed challenges, leading to signal deterioration and limitations in routine measurements. Herein, we report an anti-interference compact in situ electrochemical NMR system (AICISENS). Through a wireless strategy, the compact design allows for the independent and stable operation of electrochemical NMR components with effective interference isolation. Thus, it opens an avenue toward easy integration into in situ platforms, applicable not only to laboratory settings but also to fieldwork. The operability, reliability, and versatility were validated with a series of biomimetic assessments, including measurements of microbial electrochemical systems, functional foods, and simulated drug metabolisms. The robust performance of AICISENS demonstrates its high potential as a powerful analytical tool across diverse applications.

A novel derivative synchronous fluorescence method for the rapid, non-destructive and intuitive differentiation of denitrifying bacteria.

It is challenging to differentiate bacteria residing in the same habitat by direct observation. This difficulty impedes the harvest, application and manipulation of functional bacteria in environmental engineering. In this study, we developed a novel method for rapid differentiation of living denitrifying bacteria based on derivative synchronous fluorescence spectroscopy, as exemplified by three heterotrophic nitrification-aerobic denitrification bacteria having the maximum nitrogen removal efficiencies greater than 90%. The intact bacteria and their living surroundings can be analyzed as an integrated target, which eliminates the need for the complex pre-processing of samples. Under the optimal synchronous scanning parameter (Δλ = 40 nm), each bacterium possesses a unique fluorescence spectral structure and the derivative synchronous fluorescence technique can significantly improve the spectral resolution compared to other conventional fluorescence methods, which enables the rapid differentiation of different bacteria through derivative synchronous fluorescence spectra as fast as 2 min per spectrum. Additionally, the derivative synchronous fluorescence technique can extract the spectral signals contributed by bacterial extracellular substances produced in the biological nitrogen removal process. Moreover, the results obtained from our method can reflect the real-time denitrification properties of bacteria in the biological nitrogen removal process of wastewater. All these merits highlight derivative synchronous fluorescence spectroscopy as a promising analytic method in the environmental field.

Exploring the molecular and immune-landscape of lung cancer associated with cystic airspaces.

To explore the molecular biological characteristics of lung cancer associated with cystic airspaces (LCCA) and its potential roles on prognosis. A total of 165 LCCAs and 201 non-LCCAs were enrolled in this study. Bulk RNA sequencing was implemented in eight LCCAs and nine non-LCCAs to explore the differentially expressed genes. TCGA data were used to analyze LCCA-specific genes that associated with overall survival (OS). The median age was 60 (IQR 53 to 65) years in LCCA cohort. We found LCCA were predominant in men and had less visceral pleura invasion (VPI) or lympho-vascular invasion (LVI). Moreover, LCCA presented with higher histological heterogeneity. Kaplan-Meier analysis showed that patients of age more than 60 and positive VPI had significantly less PFS in LCCA. Cox regression suggested that LCCA, micropapillary subtype proportion and VPI were the independent risk factors for PFS. LCCA had up-regulated pathways associated with EMT, angiogenesis and cell migration. In addition, LCCA displayed higher levels of immunosuppressor infiltration (M2 macrophages, CAFs and MDSCs) and distinct cell death and metabolic patterns. BCR/TCR repertoire analysis revealed less BCR richness, clonality and high-abundance shared clonotypes in LCCA. Finally, Cox regression analysis identified that four cystic-specific genes, KCNK3, NRN1, PARVB and TRHDE-AS1, were associated with OS of lung adenocarcinoma (LUAD). And cystic-specific risk scores (CSRSs) were calculated to construct a nomogram, which performance well. Our study for the first time indicated significantly distinct molecular biological and immune characteristics between LCCA and non-LCCA, which provide complementary prognostic values in early-stage non-small cell lung cancer (NSCLC).

Establishment of a spontaneous ventilation anesthesia model for beagle dogs.

While spontaneous ventilation (SV) anesthesia is in use for clinical patients, there is still little systematic experimental research into its basic aspects. The rabbit SV model that we established previously has some limitations including the model being too small, differences in anesthetic drugs and anesthesia procedures, so we set out to establish an SV anesthesia model for beagle dogs.•Single lumen tracheal intubation was performed on beagles connecting a ventilator, and the anesthetic dosage was adjusted for spontaneous ventilation before surgery.•5 mL of 1 % lidocaine was applied as a local infiltration anesthesia at the surgical incision.•After thoracotomy, 5 mL of 1% lidocaine was sprayed onto the surface of the lungs and a T3-T7 intercostal nerve block (1:1 2 % lidocaine:0.75 % ropivacaine) was performed.

Robotic-assisted navigation system for preoperative lung nodule localization: a pilot study.

Background: Preoperative percutaneous computed tomography (CT)-guided localization of pulmonary nodules plays a pivotal role in the diagnosis and treatment of early-stage lung cancer. However, conventional manual localization techniques have inherent limitations in achieving a high degree of accuracy. Consequently, a novel robotic-assisted navigation system was developed to attain precise localization of small lung nodules. This study aims to investigate the accuracy and safety of this system in clinical applications. Methods: Patients with peripheral solitary pulmonary nodules measuring less than 20 mm were enrolled. The robotic-assisted navigation system generated a three-dimensional (3D) model based on the patient's CT images, determining the optimal puncture path. The robotic arm then accurately located the nodule and, following percutaneous puncture, indocyanine green (ICG) was injected. The primary outcome measure was the accuracy of pulmonary nodule localization, while secondary outcomes included the complication rate, procedural duration, and total radiation exposure. Results: A total of 33 nodules were successfully localized using the robotic-assisted navigation system and resected through video-assisted thoracoscopic surgery (VATS). The first-pass success rate was 100%, with a median deviation of 6.1 mm [interquartile range (IQR), 2.5-7.2 mm] between the localizer and the nodule. The median localization time was 25.0 minutes, and the single and cumulative exam dose-length products (DLP) were 534.0 and 1491.0 mGy·cm, respectively. Notably, no observable complications were reported during the procedures. Conclusions: The innovative robotic-assisted navigation system demonstrated satisfactory accuracy and holds promise for improving the percutaneous localization of lung nodules. This method represents a safe and viable alternative to traditional CT-guided manual localization techniques.

Neoadjuvant camrelizumab plus chemotherapy for resectable, locally advanced esophageal squamous cell carcinoma (NIC-ESCC2019): A multicenter, phase 2 study.

Optimal treatment for resectable esophageal squamous cell carcinoma (ESCC) is controversial, especially in the context of potential benefit of combining PD-1 blockade with neoadjuvant therapy. This phase 2 study aimed to assess neoadjuvant camrelizumab plus chemotherapy in this population. Patients (clinical stage II-IVA) received two cycles of neoadjuvant chemoimmunotherapy (NIC) with camrelizumab (200 mg on day 1) plus nab-paclitaxel (260 mg/m2 in total on day 1 and day 8) and cisplatin (75 mg/m2 in total on days 1-3) of each 21-day cycle. Surgery was performed approximately 6 weeks after completion of NIC. Primary endpoint was complete pathologic response (CPR) rate in primary tumor. Secondary endpoints were objective response rate (ORR) per RECIST v1.1, 2-year progression-free survival (PFS) rate after surgery, PFS, overall survival (OS) and safety during NIC and perioperative period. Between 17 January 2020 and 8 December 2020, 56 patients were enrolled, and 51 received esophagectomy. Data cutoff date was 25 August 2021. The CPR rate was 35.3% (95% CI, 21.7%-48.9%). NIC had an ORR of 66.7% (95% CI, 40.0%-70.4%) and treatment-related adverse events (TRAEs) of low severity (grade 1-2, 75.0%; grade 3, 10.7%; grade 4-5, no). No perioperative mortality occurred. Three (5.9%) patients had tumor recurrence and one (2.0%) patient died. The 2-year PFS rate, median PFS and median OS had not been reached yet. Camrelizumab plus neoadjuvant chemotherapy in resectable ESCC demonstrates promising efficacy with acceptable toxicity, providing a feasible and effective option. Study is ongoing for long-term survival analyses.

Andrographolide alleviates bleomycin-induced NLRP3 inflammasome activation and epithelial-mesenchymal transition in lung epithelial cells by suppressing AKT/mTOR signaling pathway.

BACKGROUND: Andrographolide (Andro), a diterpenoid extracted from Andrographis paniculata, has been shown to attenuate pulmonary fibrosis in rodents; however, the potential mechanisms remain largely unclear. This study investigated whether and how Andro alleviates bleomycin (BLM)-induced NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome activation and epithelial-mesenchymal transition (EMT) in the lung epithelial cells. METHODS: The in vivo effects of Andro were evaluated in a rat model of BLM-induced pulmonary fibrosis. The roles of Andro in BLM-induced NLRP3 inflammasome activation, EMT and AKT/mTOR signaling were investigated using human alveolar epithelial A549 cells. RESULTS: We found that Andro significantly alleviated pulmonary edema and histopathological changes, decreased weight loss, and reduced collagen deposition. Andro downregulated the levels of NLRP3, the adaptor molecule apoptosis-associated speck-like protein containing a CARD (ASC), and Caspase-1 in the lungs of BLM-treated rats, suggesting the inhibitory effect of Andro on NLRP3 inflammasome activation in vivo. Additionally, the symptoms of BLM-mediated EMT phenotype in the lung were also attenuated after Andro administration. In vitro, Andro also markedly inhibited BLM-induced NLRP3 inflammasome activation and EMT in A549 cells. Moreover, Andro inhibited BLM-induced phosphorylation of AKT and mTOR in A549 cells, suggesting that AKT/mTOR inactivation mediates Andro-induced effects on BLM-induced NLRP3 inflammasome activation and EMT. CONCLUSIONS: These data indicate that Andro can reduce BLM-induced pulmonary fibrosis through suppressing NLRP3 inflammasome activation and EMT in lung epithelial cells via AKT/mTOR signaling pathway.

Video-assisted thoracoscopic surgery for primary lung cancer resections in patients with moderate to severe chronic obstructive pulmonary diseases.

BACKGROUND: Lung cancer patients with chronic obstructive pulmonary disease (COPD) are considered a high-risk population to receive radical surgical treatment due to the high incidence of cardiopulmonary complications. The aim of this study was to evaluate the clinical factors associated with postoperative complications in primary lung cancer patients with moderate to extremely severe grades of COPD. METHODS: From December 2015 to June 2020, 138 patients with moderate to extremely severe COPD who underwent video-assisted thoracoscopic surgery (VATS) lung cancer resection (lobectomy or sublobar resection) were retrospectively reviewed. Patients' postoperative complications were collected from clinical records. Clinical factors (such as COPD severity or surgical approaches, etc.) were evaluated to investigate the association with postoperative complications. RESULTS: Of the 138 patients included in the study, the mean age was 67 (63-74) years, the mean preoperative forced expiratory volume in one second (FEV1) was 1.33±0.39 L, the mean FEV1% was 51.23% (41.43-60.00%). 33% patients (46/138) had postoperative complications, and no mortality occurred. Univariate analysis revealed that incidence of overall complications (OCs) and respiratory complications (RCs) was markedly higher in extremely severe COPD patients compared to moderate (OCs, P=0.033; RCs, P=0.050) and severe (OCs, P=0.015; RCs, P=0.008) COPD patients, respectively. Multivariate analysis showed that COPD grade was an independent risk factor of RCs (P=0.024). Furthermore, the grades of COPD (moderate, P=0.029; severe, P=0.028; extremely severe, P=0.019) and the surgical procedure (lobectomy or sublobar resection, P=0.043) were independent risk factors for atelectasis, which was the most common postoperative complication. CONCLUSIONS: The aggravation of COPD was accompanied by an increase in the incidence of respiratory system complications postoperatively, especially atelectasis. For patients with moderate to extremely severe grades of COPD, careful perioperative evaluation should be performed to identify the indicators that influence the surgical choice between lobectomy and sublobar resection.

Artificial intelligence assisted display in thoracic surgery: development and possibilities.

In this golden age of rapid development of artificial intelligence (AI), researchers and surgeons realized that AI could contribute to healthcare in all aspects, especially in surgery. The popularity of low-dose computed tomography (LDCT) and the improvement of the video-assisted thoracoscopic surgery (VATS) not only bring opportunities for thoracic surgery but also bring challenges on the way forward. Preoperatively localizing lung nodules precisely, intraoperatively identifying anatomical structures accurately, and avoiding complications requires a visual display of individuals' specific anatomy for surgical simulation and assistance. With the advance of AI-assisted display technologies, including 3D reconstruction/3D printing, virtual reality (VR), augmented reality (AR), and mixed reality (MR), computer tomography (CT) imaging in thoracic surgery has been fully utilized for transforming 2D images to 3D model, which facilitates surgical teaching, planning, and simulation. AI-assisted display based on surgical videos is a new surgical application, which is still in its infancy. Notably, it has potential applications in thoracic surgery education, surgical quality evaluation, intraoperative assistance, and postoperative analysis. In this review, we illustrated the current AI-assisted display applications based on CT in thoracic surgery; focused on the emerging AI applications in thoracic surgery based on surgical videos by reviewing its relevant researches in other surgical fields and anticipate its potential development in thoracic surgery.

Neoadjuvant Four-Drug Combination Therapy for NSCLC With EGFR Mutation Avoiding Total Pneumonectomy.

We report a case of successful neoadjuvant four-drug combination therapy to avoid total pneumonectomy. A 33-year-old male patient was diagnosed with locally advanced non-squamous NSCLC harboring EGFR mutation in the left lower lobe. The patient experienced significant clinical downstaging after two cycles of neoadjuvant therapy, including icotinib, carboplatin, pemetrexed, and bevacizumab. He underwent a successful lobectomy avoiding pneumonectomy. The patient showed no recurrence in the follow-up of a chest computed tomographic scan, which is 17 months after surgery. The promising results of this neoadjuvant combination therapy provided a novel therapeutic option for patients with locally advanced EGFR-mutated NSCLC facing total pneumonectomy.

Andrographolide attenuates epithelial-mesenchymal transition induced by TGF-ß1 in alveolar epithelial cells.

Andrographolide (Andro), a component from Chinese medicinal herb Andrographis paniculata, could alleviate pulmonary fibrosis in rodents. Yet, whether and how Andro mitigates epithelial-mesenchymal transition (EMT) induced by TGF-ß1 remain unknown. This study aimed to explore the effect of Andro on TGF-ß1-induced EMT in human alveolar epithelial cells (AECs) and the mechanisms involved. We illustrated that Andro inhibited TGF-ß1-induced EMT and EMT-related transcription factors in alveolar epithelial A549 cells. Andro also reduced TGF-ß1-induced cell migration and synthesis of pro-fibrotic factors (ie CCN-2, TGF-ß1), matrix metalloproteinases (ie MMP-2, MMP-9) and extracellular matrix (ECM) components (ie collagen 1), implying the inhibiting effect of Andro on TGF-ß1-induced EMT-like cell behaviours. Mechanistically, Andro treatment not only repressed TGF-ß1-induced Smad2/3 phosphorylation and Smad4 nuclear translocation, but also suppressed TGF-ß1-induced Erk1/2 phosphorylation and nuclear translocation in A549 cells. And treatment with ALK5 inhibitor (SB431542) or Erk1/2 inhibitors (SCH772984 and PD98059) remarkably reduced EMT evoked by TGF-ß1. In addition, Andro also reduced TGF-ß1-induced intracellular ROS generation and NOX4 expression, and elevated antioxidant superoxide dismutase 2 (SOD2) expression, demonstrating the inhibiting effect of Andro on TGF-ß1-induced oxidative stress, which is closely linked to EMT. Furthermore, Andro remarkably attenuated TGF-ß1-induced down-regulation of sirtuin1 (Sirt1) and forkhead box O3 (FOXO3), implying that Andro protects AECs from EMT partially by activating Sirt1/FOXO3-mediated anti-oxidative stress pathway. In conclusion, Andro represses TGF-ß1-induced EMT in AECs by suppressing Smad2/3 and Erk1/2 signalling pathways and is also closely linked to the activation of sirt1/FOXO3-mediated anti-oxidative stress pathway.

Metallic Nanofilm Enhanced Fluorescence Cell Imaging: A Study of Distance-Dependent Intensity and Lifetime by Optical Sectioning Microscopy.

Simple, stable, easily-fabricated smooth metallic nanofilm can improve the imaging intensity and imaging contrast. However, its application in micrometer-scale cells has not been popularized due to the lack of full understanding of their related fluorescence properties. In this study, fluorescence enhancement of cell imaging on smooth Au nanofilm was investigated over a micrometer-scale range via employment of the optical sectioning method available with a laser scanning confocal fluorescence microscope. The fluorescence enhancement reduced with the distance away from the surface of metallic nanofilm, and this distance dependence was determined by the factors of numerical aperture, dye-substrate distance, and emission wavelength. In addition, distance-dependent fluorescence lifetime images of cells were also measured to study the interaction between fluorophores and metallic film. The enhancement effect of Au nanofilm on fluorescence cell imaging can be induced not only by the standing wave formed by the reflected light and exciting light but also by the interaction between fluorophore and surface plasmons on the metallic nanofilm. Our study on smooth metallic nanofilm should pave the way for utilizing its uniform fluorescence enhancement characteristic for biological imaging.

Potential of the glasses-free three-dimensional display system in shortening the learning curve of video-assisted endoscopic surgery: a self-controlled ex-vivo study.

BACKGROUND: One of the largest challenges in endoscopic surgical training is adapting to a two-dimensional (2D) view. The glasses-free three-dimensional (GF-3D) display system was designed to integrate the merits of both 2D and conventional 3D (C-3D) displays, allowing surgeons to perform video-assisted endoscopic surgery under a stereoscopic view without heavy and cumbersome 3D glasses. METHODS: In this study, 15 junior thoracic surgeons were divided to test one routine and one complex task three times each via traditional high-definition 2D (HD-2D) and GF-3D to determine whether there was any advantage when using the GF-3D system to acquire endoscopic skills. The duration, numbers of stitches, and distance between every two stitches were recorded for every procedure. RESULTS: Seven participants were enrolled in the HD-2D group and eight participants were enrolled in the GF-3D group. All 15 participants successfully completed porcine skin continuous suture and tracheal continuous anastomosis procedures three times each. For skin continuous suture, there was no significant difference between the two groups in terms of the learning curve for speed (P=0.683) and accuracy (P=0.556). For tracheal continuous anastomosis, there was a significant difference between the two groups in terms of the learning curve for speed (P=0.001), but no significant difference was observed between the two groups in terms of the learning curve for accuracy (P=0.211). CONCLUSIONS: In summary, both HD-2D and GF-3D display systems are efficient for routine and complex endoscopic surgery. With the help of GF-3D, surgeons can acquire new complex endoscopic skills faster than HD-2D and be free from burdensome polarized glasses. More comparative studies in a clinical setting are needed to further explore the feasibility, necessity, and economic aspects of the GF-3D display system.

[Determination of cylindrospermopsin, nodularin and microcystins in freshwater fish by dispersive solid phase extraction-liquid chromatography-tandem mass spectrometry].

A method was developed for the determination of cylindrospermopsin (CYN), nodularin (NOD), microcystin-RR (MC-RR), microcystin-YR (MC-YR) and microcystin-LR (MC-LR) in freshwater fish by dispersive solid phase extraction-liquid chromatography-tandem mass spectrometry (DSPE-LC-MS/MS). The analytes were extracted from fish tissues with acetonitrile-water-formic acid (89:10:1, v/v/v), and purified by DSPE using C18 as the adsorbent. The separation of analytes was performed on an Agilent ZORBAX Eclipse XDB C18 column with the gradient elution of acetonitrile and water as mobile phases. Qualitative analysis was performed using the multiple reaction monitoring (MRM) mode. The analytes were quantified by matrix-matched external standard curves. The chromatographic and MS parameters were optimized. Major factors affecting the extraction and cleanup efficiencies including the type of extraction solvent and cleanup sorbent were investigated. The linear correlation coefficients (R2) of the five target compounds were no less than 0.9954. The limits of detection (LODs, S/N=3) and limits of quantification (LOQs, S/N=10) of the five target compounds were 5-10 µg/kg and 15-40 µg/kg, respectively. The spiked recoveries of the five target compounds ranged from 62.3% to 101.2%. The developed method is simple, rapid, accurate, sensitive, and is suitable for the determination of cylindrospermopsin, nodularin and microcystins in freshwater fish.

High performance dual-mode surface plasmon coupled emission imaging apparatus integrating Kretschmann and reverse Kretschmann configurations for flexible measurements.

A Kretschmann (KR) and reverse Kretschmann (RK) dual-mode surface plasmon coupled emission (SPCE) imaging apparatus based on prism coupling was built up. Highly directional and polarized fluorescence images for both RK and KR configurations were obtained. Besides, surface plasmon field-enhanced fluorescence and free space imaging can also be measured conveniently from this apparatus. Combining the high sensitivity of KR mode and the simplicity of RK mode, the multifunctional imaging system is flexible to provide different configurations for imaging applications. Compared to the free space imaging, SPCE imaging provides enhanced fluorescence, especially large enhancement up to about 50 fold in KR configuration. Additionally, the degree of evanescent field enhancement effect was easily estimated experimentally using the apparatus to compare the different imaging configurations. We believed that the dual-mode SPCE imaging apparatus will be useful in fundamental study of plasmon-controlled fluorescence and be a powerful tool for optical imaging, especially for microarray and biological applications.

Clinical evaluation of dengue RNA, NS1, and IgM for diagnosis of dengue in Southern China.

In 2014, a large outbreak of dengue occurred in Guangzhou, China. This outbreak prompted us to evaluate NS1 and RNA for the early diagnosis of acute dengue infection, in addition to the combination with IgM antibody. We aimed to find the differences of three assays about dengue diagnosis. This study was an evaluation of diagnosis test. Based on WHO criteria 2009, dengue RNA, NS1, and IgM/IgG were detected from 294 patients (180 dengue patients, 114 non-dengue patients) by three diagnostic kits made in China. The χ(2) test, sensitivity, and specificity were used in statistical analysis. The ratios of dengue patients with low platelet counts (<100 × 10(9) /L 32.2%) or white blood cell counts (<4.0 × 10(9) /L 58.9%) were significantly higher compared to non-dengue patients (P < 0.05). Dengue NS1 was shown sensitive (93.9%) for diagnostic use. RNA had a better performance with 98.1% of sensitivity from day 1 to day 4 after illness onset. IgM performed better at day 5 or more with 74.0% of sensitivity. The diagnostic rate using a combination of RNA and IgM was 97.8% and 96.7% using NS1 and IgM. A patient with low platelet and white blood cell counts needs additional tests for dengue during an epidemic. RNA and NS1 were most valuable for early diagnosis of dengue, whereas IgM was best suited as a supplementary method for patients at day 5 or more after illness onset.

Surface Plasmon-Coupled Directional Enhanced Raman Scattering by Means of the Reverse Kretschmann Configuration.

Surface-enhanced Raman scattering (SERS) is a unique analytical technique that provides fingerprint spectra, yet facing the obstacle of low collection efficiency. In this study, we demonstrated a simple approach to measure surface plasmon-coupled directional enhanced Raman scattering by means of the reverse Kretschmann configuration (RK-SPCR). Highly directional and p-polarized Raman scattering of 4-aminothiophenol (4-ATP) was observed on a nanoparticle-on-film substrate at 46° through the prism coupler with a sharp angle distribution (full width at half-maximum of ∼3.3°). Because of the improved collection efficiency, the Raman scattering signal was enhanced 30-fold over the conventional SERS mode; this was consistent with finite-difference time-domain simulations. The effect of nanoparticles on the coupling efficiency of propagated surface plasmons was investigated. Possessing straightforward implementation and directional enhancement of Raman scattering, RK-SPCR is anticipated to simplify SERS instruments and to be broadly applicable to biochemical assays.

Modulation of surface plasmon coupled emission (SPCE) by a pulsed magnetic field.

The unique modulation of surface plasmon coupled emission (SPCE) on a Au/Cr/Co/Cr/glass substrate by an external magnetic field has been observed. The most positive regulation was triggered by employing the multilayered substrate with a 7.5 nm-thick Co layer. The new magnetoplasmonic strategy provides a simple way to modulate the SPCE signal.

Surface plasmon coupled emission in micrometer-scale cells: a leap from interface to bulk targets.

Surface plasmon coupled emission (SPCE) technique has attracted increasing attention in biomolecular interaction analysis and cell imaging because of its high sensitivity, low detection volume and low fluorescence background. Typically, the working range of SPCE is limited at nanometers to an interface. For micrometer-scale samples, new SPCE properties are expected because of complex coupling modes. In this work, cells with different subregions labeled were studied using a SPCE spectroscopy system. Angular and p-polarized emission was observed for cell membrane, cytoplasm, and nucleus labeled with DiI, Nile Red, and propidium iodide, respectively. The SPCE signals were always partially p-polarized, and the maximum emission angle did not shift, regardless of variations in emission wavelength, fluorophore distribution and stained layer thickness. Additionally, increased polarization and a broader angle distribution were also observed with an increase in sample thickness. We also investigated the impact of metallic substrates on the SPCE properties of cells. Compared with Au and Ni substrates, Al substrates presented better polarization and angle distribution. Moreover, the real-time detection of the cell labeling process was achieved by monitoring SPCE intensity. These findings expand SPCE from a surface technique to a 3D method for investigating bulk targets beyond the nanoscale interfaces, providing a basis to apply this technique to study cell membrane fluidity and biomolecule interactions inside the cell and to distinguish between cell subregions.

Label-free aptasensor based on ultrathin-linker-mediated hot-spot assembly to induce strong directional fluorescence.

We have demonstrated the proof-of-concept of a label-free biosensor based on emission induced by an extreme hot-spot plasmonic assembly. In this work, an ultrathin linking layer composed of cationic polymers and aptamers was fabricated to mediate the assembly of a silver nanoparticles (AgNPs)-dyes-gold film with a strongly coupled architecture through sensing a target protein. Generation of directional surface plasmon coupled emission (SPCE) was thus stimulated as a means of reporting biorecognition. Both the biomolecules and the nanoparticles were totally free of labeling, thereby ensuring the activity of biomolecules and allowing the use of freshly prepared metallic nanoparticles with large dimensions. This sensor smartly prevents the plasmonic assembly in the absence of targets, thus maintaining no signal through quenching fluorophores loaded onto a gold film. In the presence of targets, the ultrathin layer is activated to link NPs-film junctions. The small gap of the junction (no greater than 2 nm) and the large diameter of the nanoparticles (~100 nm) ensure that ultrastrong coupling is achieved to generate intense SPCE. A >500-fold enhancement of the signal was observed in the biosensing. This strategy provides a simple, reliable, and effective way to apply plasmonic nanostructures in the development of biosensing.