Signal Enhancement Research Articles

Development of a multiplexing method for the quantification of “high-risk” host cell lipases in biotherapeutics by Luminex

Clearance of residual Host Cell Proteins (HCPs) is critical for the manufacturing processes of biotherapeutics. HCPs have the potential to impact product efficacy and quality, posing a risk to patient safety. It is therefore essential to be able to both identify and quantitate HCPs throughout drug development, even if the proteins are present in low concentrations. Traditional Enzyme-Linked Immunosorbent Assays (ELISAs) have historically served as the gold standard for monitoring HCPs; however, ELISA methods are labor-intensive and costly. With an increase of HCPs being identified below detectable quantification levels, there is a need for simultaneous detection of selectively targeted HCPs. Here, we develop a Luminex multiplexing method that is able to accurately quantify two “high-risk” lipases Lipoprotein Lipase (LPL) and Phospholipase B-Like 2 (PLBL2) within the same assay. This study outlines the method development for optimizing parameters such as antibody constructs, conjugation ratios, signal enhancement, and more in order to create the most efficient multiplexing method. As a result, a Luminex multiplexing method can provide a similar result to a monoplexing ELISA method but in a faster and more cost-effective manner. This method can be expanded to include other “high-risk” HCPs and used for future HCP applications.

Development of an untargeted DNA adductomics method by ultra-high performance liquid chromatography coupled to high-resolution mass spectrometry

Genotoxicants originating from inflammation, diet, and environment can covalently modify DNA, possibly initiating the process of carcinogenesis. DNA adducts have been known for long, but the old methods allowed to target only a few known DNA adducts at a time, not providing a global picture of the “DNA adductome”. DNA adductomics is a new research field, aiming to screen for unknown DNA adducts by high resolution mass spectrometry (HRMS). However, DNA adductomics presents several analytical challenges such as the need for high sensitivity and for the development of effective screening approaches to identify novel DNA adducts. In this work, a sensitive untargeted DNA adductomics method was developed by using ultra-high performance liquid chromatography (UHPLC) coupled via an ESI source to a quadrupole-time of flight mass spectrometric instrumentation. Mobile phases with ammonium bicarbonate gave the best signal enhancement. The MS capillary voltage, cone voltage, and detector voltage had most effect on the response of the DNA adducts. A low adsorption vial was selected for reducing analyte loss. Hybrid surface-coated analytical columns were tested for reducing adsorption of the DNA adducts. The optimized method was applied to analyse DNA adducts in calf thymus, cat colon, and human colon DNA by performing a MSE acquisition (all-ion fragmentation acquisition) and screening for the loss of deoxyribose and the nucleobase fragment ions. Fifty-four DNA adducts were tentatively identified, hereof 38 never reported before. This is the first untargeted DNA adductomics study on human colon tissue, and one of the few untargeted DNA adductomics studies in the literature reporting the identification of such a high number of unknowns. This demonstrates promising results for the application of this sensitive method in future human studies for investigating novel potential cancer-causing factors.

First Detection of the Enigmatic Low Latitude 150‐km Echoes in the UHF Band

AbstractThrough applying a 4‐MHz linear frequency modulation waveform, which has high range resolution and signal intensity, we successfully detected for the first time the ionospheric 150‐km echo enhancement at 430–450 MHz of the Ultra‐High‐Frequency (UHF) band using the newly built Sanya Incoherent Scatter Radar (SYISR). The obtained low signal enhancement (less than 0.5 dB) explains why previous UHF experiments did not detect them. We also found that our measured fine structure shows a much wider forbidden region than previous results and covers a much larger altitudinal and local time region. In comparison with recent upper‐hybrid instability theory and simulation, our results confirmed the predicted higher altitude occurrence, wider gaps between enhancements, the turn corner feature around sunrise, and perhaps the weak enhancement, which provide an independent evaluation of the newly proposed mechanism in UHF band. Future UHF experiments could further improve the physical understanding of 150‐km echo phenomenon.

KMnO4/Pb staining allows uranium free imaging of tissue architectures in low vacuum scanning electron microscopy

Scanning electron microscopy under low-vacuum conditions allows high-resolution imaging of complex cell/tissue architectures in nonconductive specimens. However, the conventional methods for metal staining of biological specimens require harmful uranium compounds, which hampers the applications of electron microscopy. Here, we introduce a uranium-free KMnO4/Pb metal staining protocol that allows multiscale imaging of extensive cell/tissue architectures to intensive subcellular ultrastructures. The obtained image contrast was equivalent to that of Ur/Pb staining and sufficient for ultrastructural observation, showing the fine processes of podocytes in the glomerulus, which were invisible by light microscopy. The stainability in the elastic tissue indicated that the distinct histochemical properties of KMnO4 oxidation led to Pb deposition and BSE signal enhancement superior to Ur staining. Elemental analysis clarified that the determinant of the backscattered electron signal intensity was the amount of Pb deposition enhanced by KMnO4 oxidation. This user-friendly method is anticipated to create a new approach for biomedical electron microscopy.

Rapid screening and identification strategy of lactic acid bacteria and yeasts based on Ramanomes technology and its application in fermented food

There is an urgent need for quick, sensitive, thorough, and low-cost preliminary screening and rapid identification method for probiotic resource development. Here, we constructed a culture-free, accurate and sensitive “separation-enrichment-detection” rapid evaluation and identification method of probiotics in fermented food based on Ramanomes technology, and established a Ramanome reference of lactic acid bacteria and yeasts by AgNPs nanostructure array (AgNPs NSA) chips with uniform “hot spots” and high signal enhancement ability as SERS substrates. Systematic cluster analysis could clearly distinguish among different genera of lactic acid bacteria and yeast, and could indicate the affinity and difference between lactic acid bacteria of the same genus and yeast of the same genus. The recognition accuracy of convolutive neural networks was 100 %, and the recognition sensitivity was less than 10 CFU/mL. We constructed a probiotic isolation and enrichment method by velocity gradient centrifugation and density gradient differential centrifugation, and the average recoveries of lactobacilli and yeasts were greater than 98 % in the practical application, and the accuracy of the verified classification was 100 %. In conclusion, this study has established a preliminary screening strategy of “screening before cultivating” for lactic acid bacteria and yeasts, which breaks through the principle limitation of the current traditional paradigm of “cultivating before screening”. It can greatly improve the preliminary screening rate of probiotics in fermented foods, and provide a good technical support for the mining of probiotic resources from environmental or complex matrix samples.

Kiwi-Inspired Rational Nanoarchitecture with Intensified and Discrete Magneto-Fluorescent Functionalities for Ultrasensitive Point-of-Care Immunoassay.

Fluorescent lateral flow immunoassays (FLFIA) is a well-established rapid detection technique for quantitative analysis. However, achieving accurate analysis of biomarkers at the pg mL-1 level using FLFIA still poses challenges. Herein, an ultrasensitive FLFIA platform is reported utilizing a kiwi-type magneto-fluorescent silica nanohybrid (designated as MFS) that serves as both a target-enrichment substrate and an optical signal enhancement label. The spatially-layered architecture comprises a Fe3O4 core, an endocarp-fibers like dendritic mesoporous silica, seed-like quantum dots, and a kiwi-flesh like silica matrix. The MFS demonstrates heightened fluorescence brightness, swift magnetic response, excellent size uniformity, and dispersibility in water. Through liquid-phase capturing and fluorescence-enhanced signal amplification, as well as magnetic-enrichment sample amplification and magnetic-separation noise reduction, the MFS-based FLFIA is successfully applied to the detection of cardiac troponin I that achieved a limit of detection at 8.4 pg mL-1, tens of times lower than those of previously published fluorescent and colorimetric lateral flow immunoassays. This work offers insights into the strategic design of magneto-fluorescent synergetic signal amplification on LFIA platform and underscores their prospects in high-sensitive rapid and on-site diagnosis of biomarkers.

A Systematic Investigation Based on BCI and EEG Implemented using Machine Learning Algorithms

BCI is a strong tool that improves human-system communication. It improves the brain's ability to interact with its surroundings. Recent decades have seen substantial advances in neuroscience and computer science. This has made BCI a leader in computational neuroscience and intelligence research. Recent technological advances including wearable sensing devices, real-time data streaming, machine learning, and deep learning have raised the need for electroencephalographic (EEG)-based brain-computer interface (BCI) in clinical and translational applications. EEG-based Brain-Computer Interfaces (BCIs) detect cognitive state variations throughout laborious tasks, making them advantageous for individuals. To fill in the gaps in the wide overview of the past five years (2019-2024), we surveyed the newest research on EEG signal detection and computational intelligence in brain-computer interfaces. To provide a more accurate account, we will begin by reviewing Brain-Computer Interface (BCI) technology and its main challenges. Modern signal detection and enhancement techniques for EEG signal collection and refinement follow. We also provide advanced computational intelligence methods for tracking, maintaining, and monitoring human cognitive and operational performance in everyday applications. Combinations, interpretable fuzzy models, transfer learning, and deep learning are used. We conclude with a sample of cutting-edge BCI-driven healthcare applications and explore future EEG-based BCI research.

Chenodeoxycholic acid fortified diet drives ovarian steroidogenesis to improve embryo implantation through enhancing uterine receptivity via progesterone receptor signaling pathway in rats

Infertility is a worldwide reproductive health problem influenced by the embryo implantation efficiency. We previously revealed that dietary chenodeoxycholic acid (CDCA) positively influence the early embryo implantation. But how CDCA regulate embryo implantation is largely unexplored. Herein, we investigated the mechanism behind CDCA's regulation on embryo implantation in rats. Results showed that CDCA promoted uterine receptivity, leading to increased number of implantation sites. Mechanistically, CDCA reshaped maternal amino acid metabolism and enhanced serum progesterone levels. CDCA enhanced ovarian progesterone synthesis by improving steroidogenesis-related protein (StAR and CYP11A1) expression via Takeda G-protein-coupled receptor 5. Elevated progesterone exaggerated uterine progesterone but weakened the estradiol signaling in the CDCA group, contributing to better uterine receptive for embryo implantation. Additionally, elevated transcription repressor Stat5b induced the down-regulation of progesterone-metabolizing enzyme 20-hydroxysteroid dehydrogenase 20α-HSD, complementally explained uterine progesterone signaling enhancement. Overall, our data revealed that CDCA drove ovarian steroidogenesis to improve embryo implantation through enhancing uterine receptivity via progesterone receptor pathway in rats. Therefore, CDCA diet may be a potential favorable nutritional strategy for infertility and pregnancy management.

Phosphopeptide-bridged NH2-TiO2-mediated carbon dots self-enhancing and electrochemiluminescence microsensors for label-free protein kinase A detection.

A novel electrochemiluminescence (ECL) method was developed for determination of protein kinase A (PKA) ultra-sensitively based on amidated nano-titanium (NH2-TiO2) embellished carbon dots (Mg@N-CDs) fluorescent probe, which integrated the target recognition and ECL signal enhancement. The Cys-labeled kemptides were employed to build a serine-rich synthetic substrate-heptapeptide (Cys-kemptide) on the Au-electrode surface. Then, the PKA-induced biosensor was triggered as a signal switch to introduce the large amounts of TiO2 decorated Mg@N-CD nanohybrid (Ti@NMg-CDs) into AuE/Cys-phosphopeptides for signal output. In particular, the presence of PKA could induce the formation of Cys-phosphopeptides by the catalytic reaction between specific substrate (kemptide) and PKA, which acts as an initiator to link the Ti@NMg-CDs according to the bridge interactions Ti-O-P. In this way, multiple Cys-phosphopeptides were adsorbed onto a single Ti@NMg-CDs, and the Ti@NMg-CDs not only provided high specific selectivity but also large surface area, as well as unprecedented high ECL efficiency. Using this PKA-induced enhanced sensor, the limit of detection of the PKA was 4.89 × 10-4 U/mL (S/N = 3). The proposed ECL biosensor was also universally applicable for the screening of PKA inhibitors and determining of other kinases activity. Our sensing system has excellent performance of specificity and the screening of kinase inhibitors, as well as it will inspire future effort in clinical diagnostics and new drug discovery.

DNA methylation-mediated FGFR1 silencing enhances NF-κB signaling: implications for asthma pathogenesis.

Fibroblast growth factor receptor 1 (FGFR1) is known to play a crucial role in the pathogenesis of asthma, although the precise mechanism remains unclear. This study aims to investigate how DNA methylation-mediated silencing of FGFR1 contributes to the enhancement of NF-κB signaling, thereby influencing the progression of asthma. RT-qPCR was utilized to assess FGFR1 mRNA levels in the serum of asthma patients and BEAS-2B, HBEpiC, and PCS-301-011 cells. CCK8 assays were conducted to evaluate the impact of FGFR1 overexpression on the proliferation of BEAS-2B, PCS-301-011, and HBEpiC cells. Dual-luciferase and DNA methylation inhibition assays were performed to elucidate the underlying mechanism of FGFR1 gene in asthma. The MassARRAY technique was employed to measure the methylation levels of the FGFR1 DNA. Elevated FGFR1 mRNA levels were observed in the serum of asthma patients compared to healthy controls. Overexpression of FGFR1 in BEAS-2B cells significantly enhanced cell proliferation and stimulated NF-ĸB transcriptional activity in HERK-293T cells. Furthermore, treatment with 5-Aza-CdR, a DNA demethylating agent, markedly increased the expression of FGFR1 mRNA in BEAS-2B, PCS-301-011, and HBEpiC cells. Luciferase activity analysis confirmed heightened NF-ĸB transcriptional activity in FGFR1-overexpressing BEAS-2B cells and BEAS-2B cells treated with 5-Aza-CdR. Additionally, a decrease in methylation levels in the FGFR1 DNA promoter was detected in the serum of asthma patients using the MassARRAY technique. Our findings reveal a potential mechanism involving FGFR1 in the progression of asthma. DNA methylation of FGFR1 inactivates the NF-ĸB signaling pathway, suggesting a promising avenue for developing effective therapeutic strategies for asthma.

Universal All-In-One Lateral Flow Immunoassay with Triple Signal Amplification for Ultrasensitive and Simple Self-Testing of Treponema pallidum Antibodies.

Lateral flow immunoassay (LFIA) is valued for its simplicity and rapidity for on-site screening, however, it experienced false negatives in real sample analysis due to low sensitivity. Although many signal amplification techniques can improve the sensitivity, they usually require additional complicated steps. To address these issues, taking Treponema pallidum (T. pallidum) antibodies as a model detecting target, herein, we report an all-in-one LFIA (AIO-LFIA) with triple-step signal amplification to significantly improve sensitivity while maintaining simplicity. This LFIA utilizes a biotin-streptavidin system for initial signal amplification, followed by introducing a release controller with a specific imprinted structure for timed multicomponent release, which avoids the extra steps when adding components in traditional LFIA. Particularly, a 3D-printed programmed metal in situ growth (MISG) device is integrated to localize signal enhancement at specific sites, overcoming limitations of traditional MISG and substantially reducing reagent usage and assay time, and the nitrocellulose membrane surface was much cleaner than the conventional approach, which facilitates signal readout. After optimization, the proposed AIO-LFIA is capable of visual detection down to 1 pg/mLT. pallidum antibodies in 15 min, 1000-fold lower than the gold nanoparticle-based LFIA. In clinical testing of 152 samples, the AIO-LFIA can distinguish all positive samples, outperforming commercial LFIA which missed those positive samples with relatively low antibody levels. Thus, this study presents a universal ultrasensitive and reliable AIO-LFIA strategy for infectious diseases self-testing, providing an effective promising prospect to address the challenge over emerging infectious diseases in the future.

Hydrogen Is the Superior Nebulization Gas for Desorption and Electrospray Ionization.

A previous comparative study between helium and nitrogen as nebulizing and desolvation gases in electrospray ionization (ESI) and desorption electrospray ionization (DESI) found that the signal responses of compounds of varying sizes and polarities were improved. Here, an expanded selection of nebulizing gases was evaluated to investigate mechanisms of improvement. The set of nebulizing gases included hydrogen, helium, nitrogen, argon, and carbon dioxide. Results indicate that the signal enhancements are achieved by gases lighter than nitrogen and that the previously described helium effects can be improved by using the more economical and sustainable hydrogen as a nebulizing gas. Additionally, H2 and He reduce the desorption footprint, which could be potentially useful in increasing the resolution of chemical imaging microscopy, especially since, despite the smaller footprint obtained using helium and hydrogen, higher signals are obtained compared to nitrogen.

The bifunctional transcription factor NAC32 modulates nickel toxicity responses through repression of root-nickel compartmentalization and activation of auxin biosynthesis

Nickel (Ni) is an important micronutrient, but excess Ni is toxic to many plant species. Currently, relatively little is known about the genetic basis of the plant responses to Ni toxicity. Here, we demonstrate that NAC32 transcription factor functions as a core genetic hub to regulate the Ni toxicity responses in Arabidopsis. NAC32 negatively regulates root-Ni concentration through the IREG2 (IRON REGULATED2) encoding a transporter. NAC32 also induces local auxin biosynthesis in the root-apex transition zone by upregulating YUCCA 7 (YUC7)/8/9 expression, which results in a local enhancement of auxin signaling in root tips, especially under Ni toxicity, thereby impaired primary root growth. By analyses of various combinations of nac32 and ireg2 mutants, as well as nac32 and yuc7/8/9 triple mutants, including high-order quadruple mutant, we demonstrated that NAC32 negatively regulates Ni stress tolerance by acting upstream of IREG2 and YUC7/8/9 to modulate their function in Ni toxicity responses. ChIPqPCR, EMSA (electrophoretic mobility shift assay) and transient dual-LUC reporter assays showed that NAC32 transcriptionally represses IREG2 expression but activates YUC7/8/9 expression by directly binding to their promoters. Our work demonstrates that NAC32 coordinates Ni compartmentation and developmental plasticity in roots, providing a conceptual framework for understanding Ni toxicity responses in plants.

High-Volume Production of Repeatable High Enhancement SERS Substrates Using Solid-State Superionic Stamping

Abstract Surface-enhanced Raman spectroscopy (SERS) is emerging as a powerful tool for detecting and identifying chemical and biological substances because of its high sensitivity, specificity, speed, and label-free detection. For SERS substrates to be effective in sensing applications, they must exhibit reproducible and robust high signal enhancement and cost-effective scalability. This article introduces a highly sensitive, large-area silver SERS substrate patterned with a uniform array of 3D retroreflecting inverted pyramids and develops a manufacturing pathway for it, using a novel and facile electrochemical imprinting process called solid-state superionic stamping (S4). Substrates, approximately 4 mm2 in area, are produced and tested with 1,2-bis(4-pyridyl) ethylene (BPE). Uniformly high and reproducible spatially averaged enhancement factor (EF), typically around a value of 2 × 107 with a relative standard deviation of 6.7% and a high batch-to-batch repeatability with a relative standard deviation of 10.5% between batches were observed. Passivating a substrate's surface with atomically thin layers of alumina, deposited using atomic layer deposition (ALD) was effective in maintaining the EF constant over a 60-day period, albeit with a trade-off between its EF and its lifespan. S4 has the potential to make substrates with EF consistently greater than 107 available at a cost of $1 to $2 per substrate, allowing SERS to be adopted across a wide spectrum of high-volume applications, including security, food safety, medical diagnostics, and chem-bio analysis.

Built-in electric field mediated S-scheme high-quality charge separation in BiVO4/NiAl-LDH heterojunction for highly efficient photocatalytic degradation of antibiotics

As an up and coming technology for antibiotics removal from water, photocatalysis required well-pleasing charge isolation, migration, and utilization efficiency to come true an efficaciously photocatalytic performance, but developing affordable and high-efficiency photocatalyst remains a great challenging. Herein, an emerging S-scheme BiVO4/NiAl-LDH heterojunction was ingeniously fabricated by mulberry-like BiVO4 microrods immobilized onto the surfaces of flower-like NiAl-LDH microspheres. The physicochemical properties of the BiVO4/NiAl-LDH heterojunctions were analyzed by multiple techniques. Expectedly, the manufactured BiVO4/NiAl-LDH heterojunction endowed a significantly strengthened removal rate of tetracycline compared to mono-component BiVO4 and NiAl-LDH under visible light. Specifically, the optimized BVO-NAL-3 manifested the exceptional tetracycline removal efficiency with an apparent rate constant of up to 0.0409 min−1, which was close to 34.1 and 4.4 times more rapid than those of neat NiAl-LDH and BiVO4, severally. This signal enhancement was centrally related to the creation of S-scheme heterojunction, which accelerated high-quality charge separation and strengthened redox capacity under the force of created a built-in electric field, which was corroborated by experiments results together with density functional theory calculations. Besides, the generation of superoxide radicals and photogenerated holes played an imperative role in the tetracycline degradation over BVO-NAL-3. Noteworthily, BVO-NAL-3 expressed the satisfactory stability and exceptional resistance to environmental interferences. More amazingly, other refractory antibiotics including ciprofloxacin, levofloxacin and amoxicillin were also efficaciously eliminated by BVO-NAL-3. Ultimately, the possible degradation mechanism and pathways of tetracycline were logically inferred. This work unveils a valuable afflatus for the reasonable layout and establishment of S-scheme heterojunction with high-quality charge separation for the eradication of antibiotics.

Multiplex detection of meningitis pathogens by a vertical flow paper microarray and signal enhancement suitable for low-resource settings: Proof of concept

ObjectivesMeningitis is a medical emergency, and it is crucial to diagnose it accurately and promptly in order to manage patients effectively. It would, therefore, be essential to introduce and have fast, accurate, and user-friendly methods to determine the cause of these infections. This study aimed to demonstrate a potentially cost-effective new approach for detecting meningitis using a paper-based vertical flow microarray, which could be useful in settings with limited resources. MethodsWe describe a multiplex paper microarray for detecting Neisseria meningitidis, Haemophilus influenzae, Streptococcus pneumoniae, and Salmonella spp. by the passive vertical flow of PCR-amplified clinical samples. A multibiotinylated amplicon was obtained as a product of PCR in the presence of both a biotinylated primer and biotin-11-dUTP. An enhancement step based on an enzyme-free gold enhancement protocol was also used to facilitate visual detection. ResultsThis study showed that the vertical flow microarray (previously evaluated for one pathogen) can discriminately detect the amplification results down to the 102 copies of DNA limit for four meningitis pathogens in a multiplexed set-up. The study further demonstrated the ability of this device and setup to detect three of the four pathogens from clinical biosamples. DiscussionThis study demonstrated the capacity of a vertical flow microarray device to detect amplification products for four prevalent meningitis pathogens in a multiplex format. The vertical flow microarray demonstrated consistent visualization of the expected gene amplification results; however, indicating limitations in the pre- and amplification steps. This study highlights the potential of this multiplexing method for diagnosing meningitis and other syndromic diseases caused by various pathogens, especially in resource-limited areas.

Enhancement of Calcium Libs Signals by the Simultaneous Use of Nanoparticles Together with the Application of a Weak Electric Field

Enhancement of Calcium Libs Signals by the Simultaneous Use of Nanoparticles Together with the Application of a Weak Electric Field

Real-time SERS sensing of highly toxic seawater contaminants using plasmonic silver assembled pyramidal/nanowire heterostructures

Hierarchically oriented plasmonic nanostructures have attracted an advanced molecular sensing platform for multifaceted applications. In the present work, we have attempted to fabricate ultrasensitive and cost-effective pyramidal/nanowire hetero arrays, hosted with silver nanoparticles for the effective surface-enhanced Raman spectroscopy (SERS) assisted detection of toxic water contaminants. Three-dimensionally oriented pyramidal/nanowire hetero arrays with enhanced surface area were fabricated by combining wet etching and metal-assisted chemical etching techniques. The regulation of structural features was achieved by controlling the process parameters during fabrication. Particularly, the evolution of morphological properties of the hybrid sensor was investigated in terms of nanowire aspect ratio and further analyzed in terms of SERS properties. The hetero arrays exhibited significant enhancement in Raman signal for sensing organic pollutants. Moreover, these hetero arrays with a nanowire length of ∼1 µm exhibited the highest signal enhancement. Further, the excellent reproducibility and reusability characteristics were also demonstrated for the fabricated sensors. Different cationic and anionic organic pollutants were employed for efficacy studies which showed detection limits ranging from femtomolar to picomolar levels. Finally, the real-time sensing of organic contaminants such as aniline was also investigated from seawater with an estimated enhancement factor of 8 × 108, indicating that as-fabricated hetero arrays can perform as outstanding SERS sensors for environmental remediation applications.

Formation of Armored Silicon Nanowires Array via High-Repetition-Rate Femtosecond Laser Oxidation for Robust Surface-Enhanced Raman Scattering Detection.

Superhydrophobic nanostructures with dense hotspots and high concentration efficiency are of paramount importance for highly sensitive surface-enhanced Raman scattering (SERS) detection. However, their low mechanical strength makes them susceptible to damage from external interferences, leading to hotspot loss and superhydrophobicity failure. In this study, robust SERS detection is achieved using an armored superhydrophobic silicon nanowires array. A micro/nanocross-scale oxide mask is created through high-repetition-rate femtosecond laser oxidation to fabricate the armored nanowires array. The underlying mechanisms of the nanoparticle layer serving as a mask in deep reactive ion etching (DRIE) are analyzed to elucidate the formation of the silicon nanowires. The armored nanowires array SERS substrate exhibits a high contact angle of 158°, demonstrating exceptional analyte enrichment capability. Combined with the dense hotspots provided by the high aspect ratio nanostructures, the detection limit for Rhodamine 6G is 10-13 M, and the enhancement factor (EF) is 4.35 × 109. After undergoing various mechanical tests, the substrate maintains its superhydrophobicity along with a stable Raman signal enhancement, demonstrating its resistance to potential external interference in SERS detection. The sensitive detection of various analytes highlights the promising applications of the armored nanowires substrate in diverse SERS scenarios.

Pronounced signal enhancement with gourd-shaped hollow PtCoNi bunched nanochains for electrochemical immunosensing of alpha-fetoprotein

Alpha-fetoprotein (AFP) is a vital biomarker for hepatocellular carcinoma (HCC), whose accurate analysis is essential to early diagnosis and prognosis. Herein, gourd-shaped hollow PtCoNi bunched nanochains (GH-PtCoNi BNCs) were synthesized in oleylamine under solvothermal condition coupled by acidic etching. The resulting GH-PtCoNi BNCs showed significantly enlarged specific surface area and exceptional electrocatalytic activity, as manifested by benchmarked hydrogen peroxide (H2O2) reduction, benefiting for label-free electrochemical immunoanalysis of AFP. The analytical characterizations were evaluated by a set of techniques such as chronoamperometry, cyclic voltammetry (CV), etc. The as-built biosensor displayed a broader linear range of 0.1 ∼ 105 pg mL−1 and a lower limit of detection down to 0.017 pg mL−1 in the optimized surroundings, integrated by detection of AFP in human serum samples with acceptable results. This study shows some constructive insights for development of advanced nanomaterials and applications in early diagnostics.