Changes in choroidal hemodynamics of form-deprivation myopia in Guinea pigs.

PURPOSE: We studied changes in the choroid, particularly variation in blood flow, during the development of myopia. The hemodynamic mechanism in play remains unclear. We evaluated blood flow by quantitating indocyanine green (ICG) fluorescence in a guinea pig model of form-deprivation myopia. METHODS: Guinea pigs were divided into form-deprivation myopia (FDM) and normal control (NC) groups. Ocular biometric and choroidal hemodynamics parameters were quantitatively derived via ICG imaging, and included the maximal ICG fluorescence intensity (Imax), rising time (Trising), blood flow index (BFI), and mean transit time (MTT). RESULTS: Form deprivation was associated with significant interocular differences in terms of both refractive error and axial length. ICG fluorescence hemodynamic maps of fundal blood flow and vasculature density were evident. In deprived eyes, the fluorescence signals exhibited significantly longer Trising and MTT but lower Imax and BFI than fellow eyes and NC group. The interocular differences in terms of the ocular biometric and hemodynamic parameters were significantly correlated. Hemodynamic analysis of choriocapillaris lobules revealed weakened fluorescence intensity and prolonged arrival and filling times in deprived eyes. Form deprivation reduced the number of lobulated choriocapillaris structures. CONCLUSION: Form-deprivation myopia triggered changes in the hemodynamic and vascular network structures of the choroid and choriocapillaris. The ICG fluorescence imaging/analysis method provides a unique tool for further myopia research.

Intramolecular Charge Transfer of Gold Nanoclusters for pH Indicating.

The investigation of the intramolecular charge transfer (ICT) process of gold nanoclusters (AuNCs) is critical to understand the unique features of the nanomaterials, which also benefits their further applications. Herein, 6-methyl-2-thiouracil (CH3-2-TU) and polyvinylpyrrolidone (PVP)-stabilized AuNCs are prepared, and the ICT behaviors are carefully studied. Protonation or deprotonation of the ligands around AuNCs could be used to regulate the ICT state, influencing the electron distribution and band gap. Shifted fluorescence emission phenomena are thus observed, which respond to external pH stimuli. In addition, the AuNCs are developed as color-switchable indicators for the highly sensitive detection of biogenic amines. As a proof of concept, the performance of this strategy in the evaluation of food spoilage by probing pH conditions is validated with satisfactory results. The discoveries in this work offer a convenient route to regulate the optical properties of AuNCs and the design of pH-based sensing applications.

Nano-Impact Electrochemical Biosensing Based on a CRISPR-Responsive DNA Hydrogel.

Nano-impact electrochemistry (NIE) enables simple, rapid, and high-throughput biocoupling and biomolecular recognition. However, the low effective collision frequency limits the sensitivity. In this study, we propose a novel NIE sensing strategy amplified by the CRISPR-responsive DNA hydrogel and cascade DNA assembly. By controlling the phase transition of DNA hydrogel and the self-electrolysis of silver nanoparticles, we can obtain significant electrochemical responses. The whole process includes target miRNA-induced strand displacement amplification, catalytic hairpin assembly, and CRISPR/Cas trans-cutting. Thus, ultrahigh sensitivity is promised. This NIE biosensing strategy achieves a limit of detection as low as 4.21 aM for miR-141 and demonstrates a high specificity for practical applications. It may have wide applicability in nucleic acid sensing and shows great potential in disease diagnosis.

Magnetic Multipedal DNA Walking Nanomachine Driven by Catalytic Hairpin Assembly.

miRNAs in circulating blood have been regarded as promising biomarkers for the diagnosis of a series of diseases. Development of ultrasensitive, reliable, and convenient methods for miRNA assay is of great significance. Herein, we present a novel electrochemical sensing strategy. The assembly of DNA walker strands on membrane-coated nanomaterials, target-mediated recycling activation, and electrochemical signal enrichment are integrated. Multipedal DNA walking with magnetic cores and a catalytic hairpin assembly at the electrode lead to the increase of electrochemical response, which can be used to probe initial target miRNA. This DNA walking nanomachine shows enhanced signal amplification efficiency and facile magnetic separation steps. It enables rapid analysis of miRNA at the attomole level and performs satisfactorily in samples of human circulating blood. Given the powerful sensitivity, facile operation, and excellent specificity, this magnetic multipedal DNA walker provides a promising way to determine miRNA level for biomedical applications.

Quantification of Multiplex miRNAs by Mass Spectrometry with Duplex-Specific Nuclease-Mediated Amplification.

Early quantification of multiplex biomarkers such as microRNAs (miRNAs) is critical during disease pathologic development and therapy. To tackle challenges of low abundance and multiplexing, we herein report a mass-encoded biosensing approach with duplex-specific nuclease (DSN) mediated signal amplification. Magnetic Fe3O4 cores are coated with small gold nanoparticles (AuNPs), which are applied to achieve facile DNA immobilization subsequent separation. This biosensor integrates multiple mass reporters corresponding to different targets (five miRNAs as examples). Due to the excellent resolution of mass spectrometry, these targets can be successfully distinguished in a single spectrum. Wide detection ranges from 10 fM to 1 nM are achieved, and the limits of detection are estimated to be 10 fM. High selectivity is promised due to the enzyme activity of DSN, and practical application in human serum samples performs satisfactorily. The number of targets to be tested can be further expanded by designing different specific mass tags in theory. Therefore, the proposed method can be utilized as an important and valuable tool to quantify multiplex miRNAs for disease screening as well as biomedical investigations.

Irregular DNA Triangular Prism/Triplex Assembly for Duplicate MiRNA Analysis with Nicking Endonuclease-Mediated Amplification.

Highly sensitive and selective detection of microRNA (miRNA) is becoming more and more important in the discovery, diagnosis, and prognosis of various diseases. Herein, we develop a three-dimensional DNA nanostructure based electrochemical platform for duplicate detection of miRNA amplified by nicking endonuclease. Target miRNA first helps construction of three-way junction structures on the surfaces of gold nanoparticles. After nicking endonuclease-powered cleavage reactions, single-stranded DNAs labeled with electrochemical species are released. These strands can be facilely immobilized at four edges of the irregular triangular prism DNA (iTPDNA) nanostructure via triplex assembly. By evaluating the electrochemical response, target miRNA levels can be determined. In addition, the triplexes can be disassociated by simply changing pH conditions, and the iTPDNA biointerface can be regenerated for duplicate analyses. The developed electrochemical method not only exhibits an excellent prospect in the detection of miRNA but also may inspire the engineering of recyclable biointerfaces for biosensing platforms.

Bio-Inspired Electrochemical Detection of Nitric Oxide Promoted by Coordinating the Histamine-Iron Phthalocyanine Catalytic Center on Microelectrode.

Biomimetic structures to fabricate bioelectronic interfaces that allow sensors to electrically communicate with electrodes have potential applications in the development of biosensors. Herein, inspired by the structure feature of nitric oxide (NO) sensory protein, we constructed a biomimetically catalytic center, the histamine coordinated iron phthalocyanine (FePc), for efficient and sensitive detection of NO. In specific, NO is recognized by axial tethered FePc, and the oxidative signal of NO on FePc is converted into output signal through electrocatalytic oxidation. Based on the fabricated catalytic structure on the carbon fiber electrode, on one hand, the macrocyclic π system of FePc enabled a rapid redox process, which facilitates electron transfer, thereby greatly improving sensitivity. On the other hand, by coordination with histamine on the electrode surface, FePc can enhance the electrochemical oxidation activity toward NO and promote catalytic detection, which have been revealed by electrochemical characterizations and density functional theory theoretical calculations. The designed electrochemical microsensor exhibits a low limit of detection (0.03 nM) and shows a wide detection range (0.1 nM-2 µM). In addition, the electrochemical microsensor has been successfully used for real-time monitoring of NO release by live cells. So, this work shows a new strategy for the design of bio-inspired electrochemical microsensors that may provide a potential analytical tool for tracing biological signal molecules with enzyme-free biomimetically catalytic centers.

Deep-learning-based 3D blood flow reconstruction in transmissive laser speckle imaging.

Transmissive laser speckle imaging (LSI) is useful for monitoring large field-of-view (FOV) blood flow in thick tissues. However, after longer transmissions, the contrast of the transmitted speckle images is more likely to be blurred by multiple scattering, resulting in decreased accuracy and spatial resolution of deep vessels. This study proposes a deep-learning-based strategy for high spatiotemporal resolution three-dimensional (3D) reconstruction from a single transilluminated laser speckle contrast image, providing more structural and functional details without multifocus two-dimensional (2D) imaging or 3D optical imaging with point/line scanning. Based on the correlation transfer equation, a large training dataset is generated by convolving vessel masks with depth-dependent point spread functions (PSF). The UNet and ResNet are used for deblurring and depth estimation. The blood flow in the reconstructed 3D vessels is estimated by a depth-dependent contrast model. The proposed method is evaluated with simulated data and phantom experiments, achieving high-fidelity structural reconstruction with a depth-independent estimation of blood flow. This fast 3D blood flow imaging technique is suitable for real-time monitoring of thick tissue and the diagnosis of vascular diseases.

Partial collapse of DNA tetrahedron for miRNA assay with duplex-specific nuclease-assisted amplification.

We establish a facile electrochemical approach for detecting miRNA. Programmable DNA tetrahedron is designed using thiol groups for electrode modification, the amino group for the localization of electrochemical species and a hairpin structure that responds to target miRNA. In addition, duplex-specific nuclease-assisted amplification helps improve the sensitivity of this biosensor. The target-initiated partial collapse of the DNA tetrahedron event integrates recognition, electrode immobilization, signal recruitment and amplification. By measuring the sharp silver stripping peak, the highly sensitive detection of miRNA is achieved, which also performs satisfactorily challenging biological samples. This method is featured with simple operation, high sensitivity and practical utility, exhibiting great application potential in clinical diagnosis.

Ultrasensitive electrochemical detection and inhibition evaluation of DNA methyltransferase based on cascade strand displacement amplification.

An electrochemical sensing approach for ultrasensitive DNA methyltransferase (MTase) activity assay is proposed. After specific cleavage reaction in the presence of a methylated state, strand displacement polymerization (SDP) is initiated in the solution. The product of upstream SDP further triggers downstream SDP, which enriches abundant electrochemical species at the electrode. The whole process is quite convenient with shared enzymes. Due to the cascade signal amplification, ultrahigh sensitivity is promised. Inhibitor screening results are also demonstrated to be good. Besides, target MTase can be accurately determined in human serum samples, confirming excellent practical utility. This work provides a reliable approach for the analysis of MTase activity, which is of vital importance for related biological studies and clinical applications.

Tetrahedral DNA Supported Walking Nanomachine for Ultrasensitive miRNA Detection in Cancer Cells and Serums.

A three-dimensional DNA tetrahedral nanostructure is constructed to support a walker strand on top and multiple track strands around it via the assembly of triplex-forming oligonucleotide (TFO). This design facilitates the regeneration of the sensing interface by simply adjusting pH conditions. On the basis of the tetrahedral DNA supported walking nanomachine, ultrasensitive electrochemical analysis of miRNA (miR-141) is achieved. Target miRNA assists the formation of three-way junction nanostructure. It contains a duplex region (hybridized by track and walker strands) that could be specially recognized and digested by certain nicking endonuclease. As a result, walker strand and target miRNA are released and move around the attached tracks for continuous cleavage reactions, releasing a larger number of signal reporters. By measuring the variation of signal responses, ultrasensitive analysis of miRNA is achieved. The limit of detection (LOD) is calculated to be 4.9 aM, which is rather low. In addition, the proposed method is successfully applied for the detection of miRNA in cell and serum samples, which could distinguish pathological information from healthy controls.

Ratiometric Electrochemical Switch for Circulating Tumor DNA through Recycling Activation of Blocked DNAzymes.

Circulating tumor DNA (ctDNA) serves as a powerful noninvasive and viable biomarker for the diagnosis of cancers. The abundance of ctDNA in patients with advanced stages is significantly higher than that in patients with early stages. Herein, a ratiometric electrochemical biosensor for the detection of ctDNA is developed by smart design of DNA probes and recycles of DNAzyme activation. The conformational variation of DNA structures leads to the changes of two types of electrochemical species. This enzyme-free sensing strategy promotes excellent amplification efficiency upon target recognition. The obtained results assure good analytical performances and a limit of detection as low as 25 aM is achieved. Additionally, this method exhibits outstanding selectivity and great application prospects in biological sample analysis.

DNA-MnO2 Nanoconjugates Investigation and Application for Electrochemical Polymerase Chain Reaction.

Manganese dioxide (MnO2) nanosheets are emerging for biomedical applications with excellent physical and chemical properties. Adsorption of DNA on MnO2 is important for biosensing, bioimaging, and therapy. Nevertheless, current fundamental understanding about the interaction is preliminary. Herein, UV-vis absorption spectra are applied to systematically explore the biointerfacial interaction between DNA and MnO2 with the factors of salt concentration, pH value, temperature, DNA concentration, and length. The results offer important fundamental insights into the investigation of DNA-MnO2 nanocomposites. Meanwhile, the optimal parameters are applied to construct a screen-printed electrode (SPE) modified with polymerase chain reaction (PCR) primer-decorated MnO2 nanosheets. An electrochemical PCR system is then developed for ultrasensitive detection of circulating tumor DNA (ctDNA). The limit of detection is determined to be 0.1 fM, and high selectivity is demonstrated. Combining the merits of SPE, DNA-MnO2 nanosheets, and an amplified reaction, this developed strategy shows great promise in bioanalysis, clinical disease diagnosis, and biomedicine applications.

Electrochemical Aptasensing of SARS-CoV-2 Based on Triangular Prism DNA Nanostructures and Dumbbell Hybridization Chain Reaction.

Development of convenient, accurate, and sensitive methods for rapid screening of severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) infection is highly desired. In this study, we have developed a facile electrochemical aptasensor for the detection of the SARS-CoV-2 S1 protein amplified by dumbbell hybridization chain reaction (DHCR). A triangular prism DNA (TPDNA) nanostructure is first assembled and modified at the electrode interface. Due to the multiple thiol anchors, the immobilization is quite stable. The TPDNA nanostructure also provides an excellent scaffold for better molecular recognition efficiency on the top single-strand region (DHP0). The aptamer sequence toward the SARS-CoV-2 S1 protein is previously localized by partial hybridization with DHP0. In the presence of the target protein, the aptamer sequence is displaced and DHP0 is exposed. After further introduction of the fuel stands of DHCR, compressed DNA linear assembly occurs, and the product can be stacked on the TPDNA nanostructure for the enrichment of electrochemical species. This electrochemical method successfully detects the target protein in clinical samples, which provides a simple, robust, and accurate platform with great potential utility.

Roll-to-Roll DNA Nanomachine for Ultrasensitive Electrochemical Determination of miRNA.

MicroRNAs (miRNAs) are a family of endogenous noncoding RNAs with the functions of gene regulation, which serve as promising markers for a range of diseases such as diabetic foot ulcers, cancers, etc. In this work, we engineered a roll-to-roll DNA nanomachine for highly sensitive electrochemical detection of miRNA. A dumbbell-structured DNA probe could be transitioned to be wheel-structured conformation upon target recognition, which rolls around track strands on the surface of gold nanoparticles (AuNPs) in the presence of nicking endonuclease. The resulting single strands on AuNPs are activated for the second round of rolling at the DNA-modified electrode interface, leading to the variation of electrochemical responses. The roll-to-roll amplification behavior allows a wide detection range with a limit of detection as low as 10 aM. The practicability is also demonstrated by the application in human serum samples with satisfactory results. It is expected that the proposed electrochemical method offers a new paradigm to develop miRNA assays based on DNA nanotechnology.

Synergetic Dielectric and Magnetic Losses of a Core-Shell Co/MnO/C Nanocomplex toward Highly Efficient Microwave Absorption.

High-performance microwave-absorbing materials (MAMs) derived from metal-organic frameworks (MOFs) have attracted considerable attention due to their tunable chemical composition and microstructure. In this contribution, a core-shell-structured Co/MnO/C nanocomplex was prepared using a CoMn-MIL MOF by a facile hydrothermal synthesis and subsequent pyrolysis process. The optimal microwave absorption (MA) property of the as-prepared Co/MnO/C nanocomplex was achieved by the regulation of the Co2+/Mn2+ molar ratio. The minimum reflection loss (RLmin) of the Co/MnO/C-31 nanocomplex was low to -55.0 dB at 16.2 GHz with a thickness of 1.49 mm, and the effective absorption bandwidth (EAB) was high to 5.95 GHz (12.05-18 GHz) at a thickness of 1.8 mm. The mixed-metal nanocomplex with the core-shell structure exhibited outstanding MA performance, corresponding to the synergetic effect of the magnetic and dielectric loss. It provides a high efficiency strategy for rendering low reflection loss and broad EAB to high-performance MAMs.

Inhomogeneous defect distribution of triangular WS2 monolayer revealed by surface-enhanced and tip-enhanced Raman and photoluminescence spectroscopy.

Confocal optical microscopy and tip-enhanced optical microscopy are applied to characterize the defect distributions in chemical vapor deposition-grown WS2 monolayer triangles qualitatively and quantitatively. The presence of defects in individual monolayer WS2 triangles is revealed with diffraction-limited spatial resolution in their photoluminescence (PL) images, from which the inhomogeneous defect density distribution is calculated, showing an inverse relationship to the PL intensity. The defect-related surface-enhanced Raman spectroscopy (SERS) effect is investigated by depositing a thin copper phthalocyanine layer (5 nm) as the probe molecule on the monolayer WS2 triangles surface. Higher SERS enhancement effects are observed at the defect-rich areas. Furthermore, tip-enhanced optical measurements are performed, which can reveal morphologically defected areas invisible in the confocal optical measurements. Furthermore, the area with high defect density appears brighter than the low-defected area in the tip-enhanced optical measurements, which are different from the observation in the confocal optical measurements. The underlying reasons are attributed to the near-field enhancement of the defect exciton emission induced by the optically excited tip and to an improved coupling efficiency between the tip-generated near-field with the altered dipole moment orientation at the local defect.

Light-triggered multifunctional nanoplatform for efficient cancer photo-immunotherapy.

Cancer immunotherapy is limited by the immune escape of tumor cells and adverse effects. Photo-immunotherapy, the combination of immunotherapy and phototherapy (such as photodynamic therapy (PDT) and photothermal therapy (PTT)), can improve the effectiveness of immunotherapy in cancer treatment. Here, we first explored mesoporous hexagonal core-shell zinc porphyrin-silica nanoparticles (MPSNs), which are composed of a zinc porphyrin core and a mesoporous silica shell, and exhibit high laser-triggered photodynamic and photothermal activity, as well as outstanding drug loading capacity. In other words, MPSNs can be used not only as excellent photosensitizers for photo-immunotherapy, but also as an ideal drug carrier to achieve more efficient synergy. After loading with R837 (imiquimod, a toll-like receptor-7 agonist), MPSNs@R837 will elicit high-efficiency immunogenic cell death via PDT and PTT, and promote dendritic cell maturation after the PH-responsive release of R837, thereby, inducing tumor-specific immune responses. When combined with a programmed death ligand-1 checkpoint blockade, the photo-immunotherapy system markedly restrains primary tumors and metastatic tumors with negligible systemic toxicity. Therefore, the therapeutic strategy of integrating PTT, PDT and checkpoint blockade, shows great potential for suppressing cancer metastasis.

Surgical repair of a special category of arteriovenous fistula outflow stenosis caused by venous valve hyperplasia.

OBJECTIVE: This study evaluated a special category of arteriovenous fistula outflow stenosis caused by venous valve hyperplasia and explored the effectiveness of surgical repair in dealing with this kind of stenosis. STUDY DESIGN: This retrospective cohort study was conducted from February 2016 to January 2020 in our center. Patients with arteriovenous fistula dysfunction, including flow rate insufficiency, venous hypertension, thrombosis, and aneurysm dilation enlargement, were selected. Stenosis lesions presenting with venous valve hyperplasia were selected after ultrasound screening. All patients underwent surgical repair and were followed up every 6 months after surgery. RESULTS: Forty-three patients (median age, 54.5 ± 11.2 years; 65.1% men) were included. All procedures were technically successful. Based on intraoperative exploration, 56.5% were reconstructed via autologous vein patch, 17.4% of patients were reconstructed with end-to-end reconstruction after cutting the stenotic segment, 13.0% of cases simply had the valve resected, and 13.0% of cases involved a longitudinal incision and transverse suture. All patients returned to routine dialysis the following day and avoided catheter insertion. The mean follow-up time was 22.5 ± 14.0 (range, 1.3-49.8) months. The patency rates at 2 and 4 years were 92.2% and 79.0%, respectively. Valves harvested from patients were analyzed via Masson staining and immunohistochemical staining, indicating collagen fiber and myofibroblast hyperplasia in outflow venous valve hyperplasia (OVVH). CONCLUSIONS: Outflow venous valve hyperplasia can lead to fistula dysfunction. Ultrasound is the main method to diagnosis OVVH. Special surgical repair can preserve valuable vascular resources and relieve stenosis, is safe and effective, and has a high patency rate.

Long-term patency and comparisons of venous outflow in hemodialysis forearm arteriovenous grafts.

INTRODUCTION: This retrospective study investigated the factors and the effects of different venous outflows on forearm arteriovenous graft patency. METHODS: The venous outflow sites included basilic, cephalic, median antecubital, and deep veins. Comparisons among multiple groups were analyzed. FINDINGS: A total of 179 patients with forearm loop arteriovenous grafts met the inclusion criteria. Of these, 72 were basilic, 48 were cephalic, 44 were median antecubital, and 15 were deep. The median observation period was 19 months. The survival rate was 84.9% at 24 months and 78.2% at 48 months. Primary, secondary, and assisted primary patency rates for all arteriovenous grafts were 48.9%, 72.4%, and 68.4% at 12 months; 13.8%, 33.9%, and 23.6% at 24 months; and 0.6%, 4.6%, and 2.3% at 48 months, respectively. Differences in primary patency were statistically significant compared with those of secondary and assisted primary patency (P < 0.05). Primary patency rates for cephalic, median antecubital, basilic, and deep were 47.9%, 48.6%, 47.7%, and 40.0% at 12 months and 12.5%, 13.9%, 22.7%, and 0% at 24 months, respectively. Secondary patency rates for cephalic, median antecubital, basilic, and deep were 75.0%, 69.4%, 75.0%, and 73.3% at 12 months and 39.6%, 30.6%, 38.6%, and 13.3% at 24 months, respectively. There was no significant difference in primary thrombosis among basilic, cephalic, median antecubital and deep. There were no significant differences observed in primary or secondary patency rates among all the groups. Stenoses in the venous anastomosis and outflow vein were frequently observed in all types of arteriovenous grafts. Central venous stenosis was most commonly seen in deep (26.67%). On average, 1.9 interventions per patient were performed on the graft to maintain function. CONCLUSION: Different venous outflow selections were not associated with long-term patency and the occurrence of thrombosis in hemodialysis forearm loop arteriovenous grafts.