Deformable Smart DNA Nanomachine for Synergistic Intracellular Cancer-Related miRNAs Imaging and Chemo-Gene Therapy of Drug-Resistant Tumors.

Diagnosis and treatment of tumor especially drug-resistant tumor remains a huge challenge, which requires intelligent nanomedicines with low toxic side effects and high efficacy. Herein, deformable smart DNA nanomachines are developed for synergistic intracellular cancer-related miRNAs imaging and chemo-gene therapy of drug-resistant tumors. The tetrahedral DNA framework (MA-TDNA) with fluorescence quenched component and five antennas is self-assembled first, and then DOX molecules are loaded on the MA-TDNAs followed by linking MUC1-aptamer and Mcl-1 siRNA to the antennas of MA-TDNA, so that the apt-MA-TDNA@DOX-siRNA (DNA nanomachines) is constructed. The DNA nanomachine can respond to two tumor-related miRNAs in vitro and in vivo, which can undergo intelligent miRNA-triggered opening of the framework, resulting in the "turn on" of the fluorescence for sensitively and specifically sensing intracellular miRNAs. Meanwhile, both miRNA-responded rapid release and pH-responded release of DOX are achieved for chemotherapy of tumor. In addition, the gene therapy of the DNA nanomachines is achieved due to the miRNA-specific capture and the RNase H triggered release of Mcl-1 siRNA. The DNA nanomachines intergrading both tumor imaging and chemo-gene therapy in single nanostructures realized efficient tumor-targeted, image-guided, and microenvironment-responsive tumor diagnosis and treatment, which provides a synergetic antitumor effect on drug-resistant tumor.

Whole-exome sequencing screening for candidate genes and variants associated with primary sporadic keratoconus in Chinese patients.

The pathogenesis of keratoconus (KC) is complex, and genetic factors play an important role. The purpose of this study was to screen and analyse candidate genes and variants in Chinese patients with primary sporadic KC. Whole-exome sequencing (WES) was performed to identify candidate genes and variants in 105 unrelated Chinese patients with primary sporadic KC. Through a series of screening processes, 54 candidate variants in 26 KC candidate genes were identified in 53 KC patients (53/105, 50.5%). These 54 candidate variants included 10 previously identified variants in 9 KC candidate genes and 44 novel variants in 20 KC candidate genes. The previously identified variants occurred in 25.7% (27/105) of patients. Of these, 4 variants (COL6A5, c.5014T > G; CAST, c.1814G > A; ZNF469, c.946G > A; and MPDZ, c.3836A > G) were identified for the first time in Chinese KC patients. The novel variants occurred in 33.3% (35/105) of patients. Of the 26 screened KC candidate genes, 11 KC candidate genes (CAT, COL12A1, FLG, HKDC1, HSPG2, PLOD1, ITGA2, TFAP2B, USH2A, WNT10A, and COL6A5) were found to be potentially pathogenic in Chinese KC patients for the first time. Gene Ontology (GO) biological process (BP) enrichment analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were performed on the 26 KC candidate genes using the Database for Annotation, Visualization, and Integrated Discovery (DAVID). The results showed that the KC candidate genes were significantly enriched in biological processes such as collagen fibril organization and extracellular matrix (ECM) organization and in ECM-receptor interaction and protein digestion and absorption pathways. The results further expand the spectrum of KC candidate variants and provide a basis for further KC gene studies.

Accuracy of 14 intraocular lens power calculation formulas in extremely long eyes.

PURPOSE: To compare the accuracy of 14 formulas in calculating intraocular lens (IOL) power in extremely long eyes with axial length (AL) over 30.0 mm. METHODS: In this retrospective study, 211 eyes (211 patients) with ALs > 30.0 mm were successfully treated with cataract surgery without complications. Ocular biometric parameters were obtained from IOLMaster 700. Fourteen formulas were evaluated using the optimized A constants: Barrett Universal II (BUII), Kane, Emmetropia Verifying Optical (EVO) 2.0, PEARL-DGS, T2, SRK/T, Holladay 1, Holladay 2, Haigis and Wang-Koch AL adjusted formulas (SRK/Tmodified-W/K, Holladay 1modified-W/K, Holladay 1NP-modified-W/K, Holladay 2modified-W/K, Holladay 2NP-modified-W/K). The mean prediction error (PE) and standard deviation (SD), mean absolute errors (MAE), median absolute errors (MedAE), and the percentage of prediction errors (PEs) within ± 0.25 D, ± 0.50 D, ± 1.00 D were analyzed. RESULTS: The Kane formula had the smallest MAE (0.43 D) and MedAE (0.34 D). The highest percentage of PE within ± 0.25 D was for EVO 2.0 (37.91%) and the Holladay 1NP-modified-W/K formulas (37.91%). The Kane formula had the highest percentage of PEs in the range of ± 0.50, ± 0.75, ± 1.00, and ± 2.00 D. There was no significant difference in PEs within ± 0.25, ± 0.50 ± 0.75 and ± 1.00 D between BUII, Kane, EVO 2.0 and Wang-Koch AL adjusted formulas (P > .05) by using Cochran's Q test. The Holladay 2modified-W/K formula has the lowest percentage of hyperopic outcomes (29.38%). CONCLUSIONS: The BUII, Kane, EVO 2.0 and Wang-Koch AL adjusted formulas have comparable accuracy for IOL power calculation in eyes with ALs > 30.0 mm.

Colorimetric Detection of Met Dimerization on Live Cells via Smartphone for High-Sensitivity Sensing of the HGF/Met Signaling Pathway.

Membrane protein dimerization regulates numerous cellular biological processes; therefore, highly sensitive and facile detection of membrane protein dimerization are very crucial for clinical diagnosis and biomedical research. Herein, a colorimetric detection of Met dimerization on live cells via smartphone for high-sensitivity sensing of the HGF/Met signaling pathway was developed for the first time. The Met monomers on live cells were recognized by specific ligands (aptamers) first, and the Met dimerizations triggered the proximity-ligation-assisted catalytic hairpin assembly (CHA) reaction to generate large amounts of G-quadruplex (G4) fragments which can further combine hemin to form G4/hemin DNAzymes possessing the horseradish-peroxidase-like catalytic activity for catalyzing the oxidation of ABTS by H2O2 and producing the colorimetric signal (i.e., color change). The colorimetric detection of Met on live cells was then achieved by image acquisition and processing via a smartphone. As a proof-of-principle, the HGF/Met signaling pathway based on Met-Met dimerization was facile monitored, and the human gastric cancer cells MKN-45 with natural Met-Met dimers were sensitively tested and a wide linear working range from 2 to 1000 cells with a low detection limit of 1 cell was obtained. The colorimetric assay possesses a good specificity and high recovery rate of MKN-45 cells spiked in peripheral blood, which indicates that the proposed colorimetric detection of Met dimerization can be used for convenient observation of the HGF/Met signaling pathway and has extensive application prospects in point-of-care testing (POCT) of Met-dimerization-related tumor cells.

Path sampling and integration method to calculate speckle patterns.

A stable speckle pattern is generated when a coherent beam illuminates a stationary scattering medium that contains numerous scatterers with fixed positions. To date, there has been no valid method to the best of our knowledge for calculating the speckle pattern of a macro medium with a large number of scatterers. Here, a new method based on possible path sampling with corresponding weights and coherent superposition is presented for the simulation of optical field propagation in a scattering medium and output speckle patterns. In this method, a photon is launched onto a medium with fixed scatterers. It propagates in one direction; upon collision with a scatterer, its direction is updated. The procedure is repeated until it exits the medium. A sampled path is obtained in this manner. By repeatedly launching photons, numerous independent optical paths can be sampled. A speckle pattern, corresponding to the probability density of the photon, is formed by the coherent superposition of sufficiently sampled path lengths ending on a receiving screen. This method can be used in sophisticated studies of the influences of medium parameters, motion of scatterers, sample distortions on speckle distributions, and morphological appearances. It can be used for micro-examination of optical fields in scattering media and may inspire new methods and techniques for non-invasive precision detection and diagnosis of scattering media.

Constructing perfect cubic Ag-Cu alloyed nanoclusters through selective elimination of phosphine ligands.

The aspiration of chemists has always been to design and achieve control over nanoparticle morphology at the atomic level. Here, we report a synthesis strategy and crystal structure of a perfect cubic Ag-Cu alloyed nanocluster, [Ag55Cu8I12(S-C6H32,4(CH3)2)24][(PPh4)] (Ag55Cu8I12 for short). The structure of this cluster was determined by single-crystal X-ray diffraction (SCXRD) and further validated by X-ray photoelectron spectroscopy (XPS), inductively coupled plasma (ICP), Energy-dispersive X-ray spectroscopy (EDX), thermogravimetric analysis (TGA), and 1H and 31P nuclear magnetic resonance (NMR). The surface deviation of the cube was measured to be 0.291 Å, making it the flattest known cube to date.

Intracellular miRNA-Triggered Surface-Enhanced Raman Scattering Imaging and Dual Gene-Silencing Therapy of Cancer Cell.

Development of theranostic nanosystems integrating cascaded surface-enhanced Raman scattering (SERS) imaging and gene silencing therapy for accurate cancer diagnosis and treatment is still a big challenge and rarely reported. Herein, a novel Au nanoparticles (AuNPs)-based theranostic nanosystem containing AuNP-Ys and AuNP-Ds for highly sensitive and specific cancer diagnosis and treatment was proposed for cascaded SERS imaging of intracellular cancer-related miR-106a and miR-106a-triggered DNAzyme-based dual gene-silencing therapy of cancer cells. The AuNP-Ys were prepared by modifying the AuNPs with specially designed Y-motifs, and the AuNP-Ds were obtained by colabeling Raman molecules and dsDNA linkers on AuNPs. When identifying the intracellular cancer-related miRNAs, the Y-motifs and dsDNA linkers undergoes miRNA-triggered ATP-driven conformational transitions and releases the miRNA for recycling, which results in the formation of AuNP network nanostructures to generate significantly enhanced SERS signals for sensitive identification of the cancer cells as well as the amplification and specific activation of DNAzymes to catalyze the Mg2+-assisted cleavage of the Survivin and c-Jun mRNAs for effective dual gene-silencing therapy of cancer cells. The AuNP-based theranostic nanosystem achieves the synergism of target-triggered SERS imaging and DNAzyme-based dual gene-silencing therapy with enhanced specificity, sensitivity, and curative effect, which can be a powerful tool for accurate diagnosis and efficient treatment of cancers.

DNA-mediated dynamic plasmonic nanostructures: assembly, actuation, optical properties, and biological applications.

Recent advances in DNA technology have made it possible to combine with the plasmonics to fabricate reconfigurable dynamic nanodevices with extraordinary property and function. These DNA-mediated plasmonic nanostructures have been investigated for a variety of unique and beneficial physicochemical properties and their dynamic behavior has been controlled by endogenous or exogenous stimuli for a variety of interesting biological applications. In this perspective, the recent efforts to use the DNA nanostructures as molecular linkers for fabricating dynamic plasmonic nanostructures are reviewed. Next, the actuation media for triggering the dynamic behavior of plasmonic nanostructures and the dynamic response in optical features are summarized. Finally, the applications, remaining challenges and perspectives of the DNA-mediated dynamic plasmonic nanostructures are discussed.

Effects of smoking on the retina of patients with dry age-related macular degeneration by optical coherence tomography angiography.

BACKGROUND: The macula of the retina is analysed using optical coherence tomography angiography (OCTA) to provide clinical basis and explain the mechanism of smoking as a risk factor in dry age-related macular degeneration (AMD). METHODS: This cross-sectional study included 49 normal control nonsmokers, 12 normal control smokers, 38 dry AMD nonsmokers and 35 dry AMD smokers. The foveal avascular zone (FAZ), foveal density (FD) in a 300 µm region around FAZ, vessel densities of the superficial (SCP) and deep (DCP) capillary plexuses and central fovea retinal thickness (FRT) were compared using OCTA. The bivariate correlation analysis was used to evaluate the effect of pack-year history on retina-related indices. RESULTS: The vessel densities of whole, foveal and parafoveal of SCP and whole and parafoveal of DCP in the control nonsmoking group were all significantly higher than those in the dry AMD nonsmoking group (all P < 0.05), whereas the whole vessel density of SCP in the normal smoking group was higher than that in the dry AMD smoking group (P = 0.04). The thickness values of the inner and full-layer FRT in the normal nonsmoking group were significantly thicker than those in the dry AMD nonsmoking group (all P < 0.01). The pack-year history was negatively correlated with the parafoveal vessel density of DCP (r = - 0.224, P < 0.01). CONCLUSIONS: FD, SCP, DCP and FRT are sensitive indices for the detection of early and intermediate dry AMD. DCP is a sensitive indicator that reflects the effects of smoking on the retina. Considerable changes are observed in retinal vessels, suggesting that dry AMD may affect the retinal tissue to a certain extent.

Quantitative Analysis of the RPC Vessel Density and the RNFL Thickness in Patients with Type 2 Diabetes Mellitus by Using OCT Angiography.

INTRODUCTION: This study aims to compare the structural differences in the optic disc blood perfusion and the peripapillary retinal nerve fibre layer (pRNFL) thickness in age-matched healthy subjects and patients with type 2 diabetes mellitus (DM) by using quantitative analysis with optical coherence tomography angiography (OCTA). METHODS: A cross-sectional cohort study on patients with type 2 DM with or without diabetic retinopathy (DR) and healthy subjects was conducted. The 4.5-mm scanning angio-disc pattern of the OCTA system was used to assess the optic disc. The analysed indices included radial peripapillary capillary (RPC) vessel density and pRNFL thickness. RESULTS: A total of 78 eyes from 78 patients with type 2 DM, including 27 without clinical DR (NDR), 26 with non-proliferative DR (NPDR), and 25 with proliferative DR (PDR), and 28 age-matched healthy subjects were enrolled. The average RPC vessel density of the whole (p < 0.001) and the peripapillary (p < 0.001) regions was significantly different in different groups, whereas the pRNFL was not statistically significant (p = 0.764). Compared with that in healthy subjects, the RPC vessel densities in 4, 5, and 8 peripapillary sectors in NDR (all p < 0.05), NPDR (all p < 0.05), and PDR (all p < 0.05) groups, respectively, were reduced. Compared with that in healthy subjects, the pRNFL thickness significantly decreased in the inferior nasal sector (p = 0.001) in NDR but significantly increased in the 2 sectors (all p < 0.01) in PDR. The DR severity was negatively correlated with the peripapillary RPC vessel density (r = -0.583, p < 0.001) but had no correlation with the pRNFL thickness (r = -0.045, p = 0.648). The positive correlation between the peripapillary RPC vessel density and the pRNFL thickness was statistically significant in the control (r = 0.531, p = 0.004), NDR (r = 0.528, p = 0.004), and NPDR (r = 0.405, p = 0.040) groups but not in the PDR group (r = 0.394, p = 0.05). CONCLUSIONS: The peripapillary RPC perfusion decreased with DR aggravation, which may be considered as a useful indicator of DR severity. However, the pRNFL thickness had little diagnostic power in differentiating healthy and DM eyes.

Programming Surface-Enhanced Raman Scattering of DNA Origami-templated Metamolecules.

DNA origami holds an unprecedented capability on assembling metallic nanoparticles into designer plasmonic metamolecules of emerging properties, including surface-enhanced Raman scattering (SERS). SERS metamolecules were produced by positioning nanoparticles in close proximity to each other on a DNA origami template for Raman enhancement. In earlier reports, SERS metamolecules were generally assembled into clusters containing small number of nanoparticles (2, 3, or 4) and thus had limited programmability over SERS. Herein, we expanded the structural complexity of SERS metamolecules by increasing the number of nanoparticles and by arranging them into sophisticated configurations. DNA origami hexagon tile was used as the assembling template to fabricate clusters consisting of 6, 7, 12, 18, and 30+ metallic nanoparticles. Programmable SERS was realized via controlling the size, number, or spatial arrangement of nanoparticles. We believe this method offers a general platform for fabricating sophisticated nanodevices with programmable SERS that may be applied to a variety of fields including plasmonics, nanophotonics, and sensing.

DNA Origami-Based Nanoprinting for the Assembly of Plasmonic Nanostructures with Single-Molecule Surface-Enhanced Raman Scattering.

Metallic nanocube ensembles exhibit tunable localized surface plasmon resonance to induce the light manipulation at the subwavelength scale. Nevertheless, precisely control anisotropic metallic nanocube ensembles with relative spatial directionality remains a challenge. Here, we report a DNA origami based nanoprinting (DOBNP) strategy to transfer the essential DNA strands with predefined sequences and positions to the surface of the gold nanocubes (AuNCs). These DNA strands ensured the specific linkages between AuNCs and gold nanoparticles (AuNPs) that generating the stereo-controlled AuNC-AuNP nanostructures (AANs) with controlled geometry and composition. By anchoring the single dye molecule in hot spot regions, the dramatic enhanced electromagnetic field aroused stronger surface enhanced Raman scattering (SERS) signal amplification. Our approach opens the opportunity for the fabrication of stereo-controlled metal nanostructures for designing highly sensitive photonic devices.

A dual signal amplification strategy for the highly sensitive fluorescence detection of nucleic acids.

The development of convenient sensing probes and strategies for the highly sensitive and specific detection of biomolecules is greatly significant for the diagnosis of diseases. Herein, a dual signal amplification strategy comprising target-triggered recycling and duplex-specific nuclease (DSN)-mediated amplifications was designed and proposed for a highly sensitive fluorescence assay of nucleic acids. In this strategy, three special hairpin structured single-stranded DNAs (i.e., H1, H2 and H3) were designed, and target-triggered recycling was operated on H1-modified AuNPs (i.e., AuNP-H1 probes) in the presence of target DNA, H2 and H3 to form trefoil DNAs on AuNPs (i.e., AuNP-trefoil). DSN was then incubated with AuNP-trefoil to cleave the double-stranded trefoil DNAs, causing the ROX molecules labelled on H2 and H3 to fall off the AuNPs, which resulted in the recovery of the previous AuNP-quenched fluorescence signal of ROX. The sensing mechanism was confirmed by polyacrylamide gel electrophoresis and fluorescence characterizations, and the sensing strategy was optimized from several aspects, such as the MCH blocking time of the AuNP-H1 probes (20 min) and the concentration (0.3 U) and immobilization time (15 min) of DSN. The practicability of the probes and the dual signal amplification strategy was investigated by a fluorescence assay of target DNA in human serum. A good linear calibration curve from 50 fM to 100 pM was obtained with a low detection limit of 47.68 fM. The sensing strategy showed good specificity, which could efficiently distinguish the target DNA from the single-base mismatched (SM) and completely unmatched (UM) DNAs. The recovery values ranging from 91.85% to 106.3% with the relative standard deviations (RSD) less than 7.30% also illustrated the good reliability of the proposed sensing probes and strategy. The AuNP-H1 probes and dual signal amplification strategy provide highly effective diagnostic agents and method for the analysis of disease-related nucleic acid biomarkers at the molecular level for early disease detection.

A target-mediated fuel-initiated molecular machine for high-sensitive fluorescence assay of the ZIKV gene via strand displacement reaction-based signal recovery and cycling amplification.

Zika virus (ZIKV) is a serious threat to human health due to its widespread human arboviral infections, and early diagnosis is one of the keys to preventing infections from spreading, but there is a lack of highly sensitive and specific detection. In this work, a target-mediated fuel-initiated molecular machine was proposed for the high-sensitive fluorescence assay of the ZIKV gene via strand displacement reaction-based signal recovery and cycling amplification. The molecular machine was prepared by modifying AuNP surfaces with specially designed lock-like DNAs (LLDs). The LLDs assembled with a hairpin DNA (H1) and a fluorescent aDNA can be opened under the trigger of the ZIKV gene and the strand displacement reactions are further initiated with the help of the DNA fuel (H2), which results in the release of the aDNAs and ZIKV genes from the AuNPs, causing the recovery of the fluorescence signal and the cyclic amplification of the gene. The target-mediated fuel-initiated molecular machines output an amplified fluorescence signal with the enhancement of 360%, and possess good sensitivity for detecting the ZIKV gene in serum with a linear calibration curve from 100 pM to 1 fM and a low limit of detection of 0.90 fM. The molecular machines can differentiate the ZIKV gene from the single base mismatched DNA obviously and show good recovery of ZIKV gene detection, which demonstrates the good specificity, reproducibility and reliability of the highly sensitive assay for the early detection of the virus.

Highly sensitive SERS assay of DENV gene via a cascade signal amplification strategy of localized catalytic hairpin assembly and hybridization chain reaction.

Pathogenic viruses with worldwide distribution, high incidence and great harm are significantly and increasingly threatening human health. However, there is still lack of sufficient, highly sensitive and specific detection methods for on-time and early diagnosis of virus infection. In this work, taking dengue virus (DENV) as an example, a highly sensitive SERS assay of DENV gene was proposed via a cascade signal amplification strategy of localized catalytic hairpin assembly (LCHA) and hybridization chain reaction (HCR). The SERS assay was performed by two steps, i.e., the operation of cascade signal amplification strategy and the following SERS measurements by transferring the products on SERS-active AgNRs arrays. The sensitivity of the cascade signal amplification strategy is significantly amplified, which is 4.5 times that of individual CHA, and the signal-to-noise ratio is also improved to 5.4 relative to 1.8 of the CHA. The SERS sensing possesses a linear calibration curve from 1 fM to 10 nM with the limit of detection low to 0.49 fM, and has good specificity, uniformity and recovery, which indicates that the highly sensitive SERS assay provides an attractive tool for reliable, early diagnosis of DENV gene and is worth to be popularized in a wide detection of other viruses.

Plasmonic Heterodimers with Binding Site-Dependent Hot Spot for Surface-Enhanced Raman Scattering.

A novel plasmonic heterodimer nanostructure with a controllable self-assembled hot spot is fabricated by the conjugation of individual Au@Ag core-shell nanocubes (Au@Ag NCs) and varisized gold nanospheres (GNSs) via the biotin-streptavidin interaction from the ensemble to the single-assembly level. Due to their featured configurations, three types of heterogeneous nanostructures referred to as Vertice, Vicinity, and Middle are proposed and a single hot spot forms between the nanocube and nanosphere, which exhibits distinct diversity in surface plasmon resonance effect. Herein, the calculated surface-enhanced Raman scattering enhancement factors of the three types of heterodimers show a narrow distribution and can be tuned in orders of magnitude by controlling the size of GNSs onto individual Au@Ag NCs. Particularly, the Vertice heterodimer with unique configuration can provide extraordinary enhancement of the electric field for the single hot spot region due to the collaborative interaction of lightning rod effect and interparticle plasmon coupling effect. This established relationship between the architecture and the corresponding optical properties of the heterodimers provides the basis for creating controllable platforms which can be exploited in the applications of plasmonic devices, electronics, and biodetection.

Copper oxide-modified graphene anode and its application in organic photovoltaic cells.

Graphene is an ideal substitute for indium tin oxide electrode in organic photovoltaic (OPV) devices, due to its outstanding electrical, optical, chemical and mechanical properties. However, the graphene electrode suffers from work function mismatch with common hole injection layer and intrinsic hydrophobic property. Here, CuxO is proposed to modify monolayer graphene in order to increase the work function of graphene (from 4.45 to 4.76 eV) and decrease the water contact angle (from 88° to 59°). Then, the OPV devices based on the CuxO modified graphene anode are fabricated successfully, and power conversion efficiency (PCE) is enhanced from 4.00 ± 0.44 to 5.23 ± 0.47%. Furthermore, the ternary blended polymer solar cell is fabricated by adding a small molecular material 1, 2, 5-thiadiazole-fused 12-ring polyaromatic hydrocarbon into the active layer, and the PCE is improved to 6.03 ± 0.53%, due to the enhanced absorption and depressed recombination inside the active layer.

DNA-Origami-Based Assembly of Anisotropic Plasmonic Gold Nanostructures.

Precise control over the assembly of anisotropic plasmonic gold nanostructures with relative spatial directionality and sequence asymmetry remains a major challenge and offers great fundamental insight and optical application possibilities. Here, a novel strategy is developed to anisotropically functionalize gold nanorods (AuNRs) by using a DNA-origami-based precise machine to transfer essential DNA sequence configurations to the surface of the AuNRs through an intentionally designed toehold-initiated displacement reaction. Different AuNR products are examined via hybridization with DNA-AuNPs that display distinct elements of regiospecificity. These assembled anisotropic plasmonic gold nanostructures based on the DNA-origami precise machine inherit the encoded information from the parent platform with high fidelity and show fixed orientation and bonding anisotropy, thereby generating discrete plasmonic nanostructures with enhanced Raman resonance.

Rapid and accurate SERS assay of disease-related nucleic acids based on isothermal cascade signal amplifications of CRISPR/Cas13a system and catalytic hairpin assembly.

Developing rapid, accurate and convenient nucleic acid diagnostic techniques is essential for the prevention and control of contagious diseases that are prone to gene mutations and may have homologous sequences, especially emerging infectious diseases such as the SARS-CoV-2 pandemic. Herein, a one-pot SERS assay integrating isothermal cascade signal amplification strategy (i.e., CRISPR/Cas13a system (Cas13a) and catalytic hairpin assembly (CHA), Cas13a-CHA) and SERS-active silver nanorods (AgNRs) sensing chips was proposed for rapid and accurate detection of disease-related nucleic acids. Taking SARS-CoV-2 RNA assay as a model, the Cas13a-CHA based SERS sensing strategy can achieve ultra-high sensitivity low to 5.18 × 102 copies·mL-1 within 60 min, and excellent specificity, i.e., not only the ability to identify SARS-CoV-2 RNA from gene mutations, but also incompatibility with coronaviruses such as severe acute respiratory syndrome (SARS-CoV), Middle East respiratory syndrome (MERS-CoV), and other respiratory viruses. The proposed Cas13a-CHA based SERS assay for SARS-CoV-2 RNA has satisfactory sensitivity, specificity, uniformity, and repeatability, and can be easily expanded and universalized for screening different viruses, which is expected to promise as a crucial role for diagnosis of disease-related nucleic acids in various medical application scenarios.

Portable SERS biosensor based on aptamer-assisted catalytic hairpin assembly signal amplification for ultrasensitive detection of Staphylococcus aureus.

Bacteria infections pose a serious threat to public health, and it is urgent to develop facile and accurate detection methods. To meet the important need, a potable and high-sensitive surface enhanced Raman scattering (SERS) biosensor based on aptamer recognition and catalytic hairpin assembly (CHA) signal amplification was proposed for point-of-care detection of Staphylococcus aureus (S. aureus). The SERS biosensor contains three parts: recognition probes, SERS sensing chip, and SERS tags. The feasibility of the strategy was verified by gel electrophoresis, and the one-step test route was optimized. The bacteria SERS biosensor has a good linear relationship ranging from 10 to 107 CFU mL-1 with high sensitivity low to 5 CFU mL-1, and shows excellent specificity, uniformity, and repeatability on S. aureus identification and enumeration, which can distinguish S. aureus from other bacteria. The SERS biosensor shows a good recovery rate (95.73 %-109.65 %) for testing S. aureus spiked in milk, and has good practicability for detecting S. aureus infected mouse wound, which provides a facile and reliable approach for detection of trace bacteria in the real samples.