Study of Interfacial Adhesion and Re-Ir Alloy Coating in Chalcogenide Glass Molding.

Precision glass molding (PGM) has become an efficacious technique to fabricate high-precision optics. Chalcogenide (ChG) glass is increasingly used in thermal imaging, night vision, etc., because of its excellent infrared optical properties. Nevertheless, glass-mold interfacial adhesion has emerged as a pivotal issue within the PGM process. The interfacial adhesion during PGM has the potential to significantly undermine the performance of molded optics and reduce the longevity of molds. It is important to investigate interfacial adhesion behaviors in the PGM. In this study, the interfacial adhesion mechanism between ChG glass and the nickel-phosphorus (Ni-P) mold is analyzed using the cylindrical compression test. The effect of ChG glass internal stress on physical adhesion is investigated by finite element method (FEM) simulation. The spherical preform is proven to be capable of reducing the stress concentration and preventing physical adhesion. More importantly, a rhenium-iridium (Re-Ir) alloy coating is deposited on the Ni-P mold surface by ion sputtering to prevent atomic diffusion and resolve the problem of chemical adhesion. Finally, ChG glass microstructures with high accuracy are fabricated using the spherical ChG glass preform and the Re-Ir-coated Ni-P mold by PGM.

Click chemistry-mediated cyclic cleavage of metal ion-dependent DNAzymes for amplified and colorimetric detection of human serum copper (II).

The determination of the level of Cu2+ plays important roles in disease diagnosis and environmental monitoring. By coupling Cu+-catalyzed click chemistry and metal ion-dependent DNAzyme cyclic amplification, we have developed a convenient and sensitive colorimetric sensing method for the detection of Cu2+ in human serums. The target Cu2+ can be reduced by ascorbate to form Cu+, which catalyzes the azide-alkyne cycloaddition between the azide- and alkyne-modified DNAs to form Mg2+-dependent DNAzymes. Subsequently, the Mg2+ ions catalyze the cleavage of the hairpin DNA substrate sequences of the DNAzymes and trigger cyclic generation of a large number of free G-quadruplex sequences, which bind hemin to form the G-quadruplex/hemin artificial peroxidase to cause significant color transition of the sensing solution for sensitive colorimetric detection of Cu2+. This method shows a dynamic range of 5 to 500 nM and a detection limit of 2 nM for Cu2+ detection. Besides, the level of Cu2+ in human serums can also be determined by using this sensing approach. With the advantages of simplicity and high sensitivity, such sensing method thus holds great potential for on-site determination of Cu2+ in different samples. Graphical abstract Sensitive colorimetric detection of copper (II) by coupling click chemistry with metal ion-dependentDNAzymes.

Effects of interface thermal resistance on surface morphology evolution in precision glass molding for microlens array.

To study the effects of the interface thermal resistance on surface morphology evolution in precision glass molding (PGM) for microlens array with different mold materials, including Tungsten carbide and heat-resistant stainless steel, the glass-mold interface thermal resistance is calculated, and heat-transfer simulation of PGM based on an interface thermal resistance model at the heating stage is conducted correspondingly. The effect of flattening behavior on the glass-mold interface is explained. Then, experiments evaluating the relationship between heating time and glass surface roughness are carried out, and the glass adhesion phenomenon appearing on the heat-resistant stainless steel mold is observed and analyzed. Finally, the microlens array is fabricated on the nickel phosphorous plating layer on the heat-resistant stainless steel substrate by diamond-ball nose-end milling, and experiments of PGM for the microlens array are carried out to verify the interface thermal resistance model. The result shows that a high-quality surface can be obtained by the combination of a smooth mold and rough glass. Compared with the microlens array fabricated with the rough glass preform, using the smooth glass preform achieves higher form accuracy without defects or blurs.

Surface defect analysis on formed chalcogenide glass Ge22Se58As20 lenses after the molding process.

Chalcogenide glass (ChG) is increasingly used in infrared optical systems owing to its excellent infrared optical properties and scalable production using precision glass molding (PGM). However, surface scratches affected by the molding temperature and microdimples on the lens surface caused by gas release seriously impair the quality of the formed lens. To reduce these surface defects when molding Ge22Se58As20 ChG, the temperature effect must be studied, and the gas generation must be minimized, while the gas escape must be maximized. In this work, we studied the effect of temperature on the surface defects. Additionally, we studied the influences of the roughness and curvature of the contact surfaces, as well as the pressing force on the formation of the microdimples. It was found that the molding temperature should be approximately 30°C higher than the softening temperature (Ts) to avoid surface scratches. The gas generation could be inhibited by increasing the pressing force and decreasing the roughness of the mold surface, and finally, increasing the curvature difference between the mold and glass preform surfaces improved the gas escape.

Aptamer pseudoknot-functionalized electronic sensor for reagentless and single-step detection of immunoglobulin E in human serum.

The development of electronic sensors with minimized usage of reagents and washing steps in the sensing protocols will significantly facilitate the detection of biomolecules. In this work, by using a new pseudoknot design of the aptamer probes, the construction of an electronic sensor for reagentless and single-step detection of immunoglobulin E (IgE) in human serum is described. The pseudoknot aptamer probes are self-assembled on the disposable electrode surface. The association of IgE with the aptamer probes leads to conformational changes of the pseudoknot aptamer structures and brings the redox-tags in close proximity to the electrode, resulting in amplified current response for monitoring IgE. The effects of the pseudoknot structure and the immobilization concentration of the aptamer probes on the sensor performance are evaluated. Under optimal conditions, the detection limit for IgE is estimated to be 60 pM. The sensor is also selective and can be employed to detect IgE in human serum samples. The developed sensor can achieve reagentless, washing-free and low-cost (with the disposable electrode) electrochemical detection of proteins, making this device a convenient sensing platform for the monitoring of different biomarkers when coupled with the appropriate aptamer probes.

Coupling of background reduction with rolling circle amplification for highly sensitive protein detection via terminal protection of small molecule-linked DNA.

In this work, by coupling background current reduction with rolling circle amplification (RCA), we describe the development of an ultrasensitive electrochemical sensing method for protein detection based on a small molecule-linked DNA terminal protection strategy. Our detection platform employs a typical streptavidin (STV)-biotin interaction system. Biotin-linked single-stranded DNA (SH-ssDNA-biotin) is self-assembled on a gold electrode to capture the target protein, STV. The binding of STV with the biotin small molecule recognition element protects the SH-ssDNA-biotin against hydrolysis by exonuclease I (Exo I), while the unbound SH-ssDNA-biotin is effectively hydrolyzed and removed from the electrode surface. The bound STV further interacts with long, RCA-amplified biotin DNAs to facilitate the adsorption of numerous electroactive reporters, hexaammineruthenium(III) chloride (RuHex) via electrostatic interactions, which results in significantly amplified signals for the quantitative determination of STV. Moreover, the removal of the unbound SH-ssDNA-biotin probes from the sensing electrode obviates the accumulation of RuHex and leads to a highly minimized background current. The simultaneous RCA signal amplification and background current reduction is expected to significantly enhance the signal-to-noise ratio and to achieve ultrahigh sensitivity. The results reveal that the developed strategy provides a low detection limit of 0.4 pM with high selectivity.

Hepatoid Adenocarcinoma of the Lung: A Systematic Review of the Literature From 1981 to 2020.

OBJECTIVES: We report the first case of hepatoid adenocarcinoma of the lung (HAL) with PIK3CA mutation. In addition, we analyzed data from HAL cases over the past 40 years to study its main treatment methods, prognosis, and the relationship between prognosis and the serum alpha-fetoprotein (AFP) level before treatment. METHODS: We report a 66-year-old male case who was diagnosed with locally advanced HAL with PIK3CA mutation and carried out a systematic literature search for HAL cases documented between 1981 and 2020. General patient information including case characteristics was extracted and summarized. The median OS (mOS) of HAL patients was determined using the KM survival curve. The Cox proportional hazards regression model was used to evaluate the effect of tumor size, location, and serum AFP value before treatment and radical surgery (RS) on the prognosis of patients. RESULTS: A total of 46 studies including 51 HAL patients was included in our review. Our study revealed that 52.9% of tumors were located in the upper lobe of the right lung. The proportion of serum AFP-positive patients before treatment, early-stage patients (TNM stage I and II), and patients who had received surgery were 69.2%, 34.1%, and 40%, respectively. The mOS of HAL patients was 16.0 months. The 2-year and 5-year survival rates of the patients were 35.3% and 8.0%, respectively. In the subgroup analysis, the 2-year survival rate for patients who received RS was 62.5%, while for patients who were unable to undergo RS, it was only 12.5% (p = 0.009). The Cox proportional hazards regression model indicated that RS can significantly improve the prognosis of HAL patients (p = 0.011), although the location and size of tumor as well as the serum AFP value before treatment had no significant effect on their prognosis (p = 0.82, p = 0.96, p = 0.25). CONCLUSIONS: HAL patients have a poor prognosis, and the survival benefits for patients receiving chemoradiotherapy or chemotherapy alone appear to be limited. We demonstrate statistically for the first time that pretreatment serum AFP values are not related to the prognosis of HAL patients and RS can significantly improve patient prognosis.

Development of Rapid and High-Precision Colorimetric Device for Organophosphorus Pesticide Detection Based on Microfluidic Mixer Chip.

The excessive pesticide residues in cereals, fruit and vegetables is a big threat to human health, and it is necessary to develop a portable, low-cost and high-precision pesticide residue detection scheme to replace the large-scale laboratory testing equipment for rapid detection of pesticide residues. In this study, a colorimetric device for rapid detection of organophosphorus pesticide residues with high precision based on a microfluidic mixer chip was proposed. The microchannel structure with high mixing efficiency was determined by fluid dynamics simulation, while the corresponding microfluidic mixer chip was designed. The microfluidic mixer chip was prepared by a self-developed liquid crystal display (LCD) mask photo-curing machine. The influence of printing parameters on the accuracy of the prepared chip was investigated. The light source with the optimal wavelength of the device was determined by absorption spectrum measurement, and the relationship between the liquid reservoir depth and detection limit was studied by experiments. The correspondence between pesticide concentration and induced voltage was derived. The minimum detection concentration of the device could reach 0.045 mg·L-1 and the average detection time was reduced to 60 s. The results provide a theoretical and experimental basis for portable and high-precision detection of pesticide residues.

Preparation of the Coupling Co-Precipitation and Impregnation Catalyst Ag/Al2O3 with High Catalytic Performance in Selective Catalytic Reduction of NO with C3H6.

This brief paper reported an Ag/Al2O3 catalyst of high catalytic performance in C3H6-SCR (selective catalytic reduction with C3H6 as the reducer), and demonstrated a new strategy for the preparation of high active Ag/Al2O3 catalyst by the coupling co-precipitation and impregnation method. The results show that the coupling co-precipitation and impregnation catalyst was higher active than the usual impregnated catalyst in C3H6-SCR of NO with broad active temperature window (420-600 °C), and the highest conversions of NO achieved 91% over the coupling co-precipitation and impregnation catalyst at 500 °C. The porous structure parameter, crystal phase structure, surface acidity property and particle morphology of the Ag/Al2O3 catalyst were characterized by the Brunauer-Emmett-Teller (BET) method, X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-vis spectra and temperature programmed desorption of ammonia (NH3-TPD), respectively. Based on the characterization, it is found that the catalyst prepared by the coupling co-precipitation and impregnation method has smaller particles and better dispersion than the usual impregnated catalyst, and so the catalyst exhibited excellent catalytic activity. NH3-TPD results illustrate that the weak and medium-strong acid sites is conducive to the reactivity of catalyst.

Recent advances in supported molecular sieve catalysts with wide temperature range for selective catalytic reduction of NO X with C3H6.

NO X is a major atmospheric pollutant that is emanated by motor vehicles, thermal power plants, and industrial boilers. Therefore, the removal of NO X is a research hotspot in the exhaust gas treatment field. Numerous methods have been used to eliminate NO X : the selective catalytic reduction of NO X using C3H6 as the reducing agent (C3H6-SCR) is an effective method to remove NO X . The key issue in NO X removal in C3H6-SCR is to obtain catalysts with low-temperature activity and wide operating temperatures. Till date, different supported wide-temperature-active molecular sieve catalysts have been prepared and used in C3H6-SCR reactions. Studies have shown that the catalytic performance of supported catalysts is related not only to the active component but also to the structural and textural parameters of the molecular sieve supports. This review summarizes the structural and textural characteristics, catalytic properties, and catalytic mechanism of molecular sieve catalysts with different pore structures for C3H6-SCR reactions. The design strategies of supported molecular sieve catalysts are suggested. The goal of this review is to highlight (1) the structural and textural characteristics and low-temperature catalytic performance of different supported molecular sieve catalysts; (2) the relationship between wide-temperature window and loaded active components, as well as carriers of the supported molecular sieve catalysts; and (3) design strategies and development prospects of supported molecular sieve catalysts with low-temperature activity and wide-temperature operating range for C3H6-SCR reactions.

S100A9 promotes the proliferation and migration of cervical cancer cells by inducing epithelial­mesenchymal transition and activating the Wnt/ß­catenin pathway.

S100 calcium­binding protein A9 (S100A9), a member of the S100 protein family, is often upregulated in various cancers, including cervical cancer. Elevated S100A9 expression is thought to serve an important role in tumorigenesis; however, the exact role of S100A9 in the modulation of cervical cancer and the underlying molecular mechanism remain unknown. In the present study, we aimed to investigate the effects of S100A9 on the proliferation and migration of cervical cancer cells, as well as the molecular mechanisms underlying these effects. Our results demonstrated that endogenous expression of S100A9 in SiHa and CaSki cell lines was significantly higher than in the HeLa cell line. As expected, overexpression of S100A9 enhanced the proliferation and migration of cervical cancer cells. In addition, S100A9 overexpression induced epithelial­mesenchymal transition (EMT) as determined by reduced expression levels of the epithelial marker E­cadherin, whereas the expression levels of the mesenchymal marker vimentin were upregulated. Furthermore, it was reported that the effects of S100A9 in the modulation of cervical cancer cells were mediated through the Wnt/ß­catenin signaling pathway as ß­catenin knockdown significantly suppressed the ability of S100A9 to enhance the proliferation and migration of cervical cancer cells. Collectively, these findings suggest that S100A9 promoted the proliferation and migration of cervical cancer cell lines. Furthermore, the underlying molecular mechanisms may be partially attributed to the induction of EMT and activation of the Wnt/ß­catenin signaling pathway.

Cascaded signal amplification via target-triggered formation of aptazyme for sensitive electrochemical detection of ATP.

The construction of reliable sensors for adenosine triphosphate (ATP) detection gains increasing interest because of its important roles in various enzymatic activities and biological processes. Based on a cascaded, significant signal amplification approach by the integration of the aptazymes and catalytic hairpin assembly (CHA), we have developed a sensitive electrochemical sensor for the detection of ATP. The target ATP leads to the conformational change of the aptazyme sequences and their association with the hairpin substrates to form active aptazymes, in which the hairpin substrates are cyclically cleaved by the metal ion cofactors in buffer to release the enzymatic sequences that can also bind the hairpin substrates to generate active DNAzymes. The catalytic cleavage of the hairpin substrates in the aptazymes/DNAzymes thus results in the generation of a large number of intermediate sequences. Subsequently, these intermediate sequences trigger catalytic capture of many methylene blue-tagged signal sequences on the electrode surface through CHA, producing significantly amplified current response for sensitive detection of ATP at 0.6nM. Besides, the developed sensor can discriminate ATP from analogous interference molecules and be applied to human serum samples, making the sensor a useful addition to the arena for sensitive detection of small molecules.

Fabrication of a Micro-Lens Array Mold by Micro Ball End-Milling and Its Hot Embossing.

Hot embossing is an efficient technique for manufacturing high-quality micro-lens arrays. The machining quality is significant for hot embossing the micro-lens array mold. This study investigates the effects of micro ball end-milling on the machining quality of AISI H13 tool steel used in the micro-lens array mold. The micro ball end-milling experiments were performed under different machining strategies, and the surface roughness and scallop height of the machined micro-lens array mold are measured. The experimental results showed that a three-dimensional (3D) offset spiral strategy could achieve a higher machining quality in comparison with other strategies assessed in this study. Moreover, the 3D offset spiral strategy is more appropriate for machining the micro-lens array mold. With an increase of the cutting speed and feed rate, the surface roughness of the micro-lens array mold slightly increases, while a small step-over can greatly reduce the surface roughness. In addition, a hot embossing experiment was undertaken, and the obtained results indicated higher-quality production of the micro-lens array mold by the 3D offset spiral strategy.

BCL6B suppresses proliferation and migration of colorectal carcinoma cells through inhibition of the PI3K/AKT signaling pathway.

B­cell CLL/lymphoma 6 member B (BCL6B), a BCL6­homologous gene, has been reported to be a tumor suppressor that is silenced in a variety of human cancers, including colorectal cancer (CRC). Although it was recently demonstrated that reduced expression of BCL6B is associated with tumor stage and lymph node metastasis in CRC, little is known on whether BCL6B contributes to CRC development, or the related underlying mechanism. The aim of the present study was to detect BCL6B expression in CRC cells, and determine the molecular mechanisms underlying the role of BCL6B in CRC development by investigating cell proliferation and migration in vitro. As a result, BCL6B expression was found to be notably repressed in CRC cells compared with normal intestinal epithelial cells by reverse transcription­polymerase chain reaction and western blot analysis. CRC cell proliferation was significantly inhibited by BCL6B upregulation, as indicated by MTT and colony­forming assays. Cell apoptosis was markedly induced, as indicated by flow cytometry, and BCL6B­transfected CRC cells exhibited decreased migration ability. Additionally, BCL6B overexpression diminished the phosphorylation level of AKT in CRC cells. These effects of BCL6B were empowered by treatment with the specific phosphoinositide 3 kinase (PI3K)/AKT inhibitor LY294002. Furthermore, overexpression of BCL6B resulted in upregulation of E­cadherin and downregulation of cyclin D1 and matrix metalloproteinase­9, which were strongly enhanced by LY294002. In conclusion, the findings of the present study demonstrated that BCL6B suppressed the proliferation and migration of CRC cells indirectly, via inhibition of PI3K.

S100A6 promotes the proliferation and migration of cervical cancer cells via the PI3K/Akt signaling pathway.

Cervical cancer is the second most common gynecological cancer worldwide and remains one of the leading causes of cancer-associated mortality among women. S100A6 has been reported to be associated with the development of many types of cancer. The aim of the present study was to investigate the effect of S100A6 on the proliferation, apoptosis and migration of cervical cancer cells and its underlying molecular mechanisms. Quantative polymerase chain reaction (qPCR) was used to detect the basic mRNA level of S100A6 in HeLa, SiHa and CaSki cells. Western blot analysis was used to detect the protein level of S100A6, epithelial cadherin, neuronal cadherin, phosphorylated protein kinase B (p-Akt), t-Akt, p-glycogen synthase kinase 3ß (GSK3ß), t-GSK3ß and ß-catenin. Semi-qPCR was used to detect the mRNA level of Snail, Twist and Vimentin. MTT and Hoechst staining assays were used to detect the proliferation and apoptosis of cells, and wound healing and Transwell assays were used to detect the migration of cells. The results of the present study demonstrate that the levels of S100A6 were decreased in HeLa cells compared with in SiHa and CaSki cells. Overexpression of S100A6 in HeLa and CaSki cells promoted the proliferative and migratory ability, and had no significant effect on cellular apoptosis. Whereas the knockdown of S100A6 in SiHa and CaSki cells inhibited the proliferative and migratory ability, it had no significant effect on apoptosis. The overexpression of S100A6 in HeLa cells increased the levels of neuronal (N)-cadherin, vimentin, Snail and Twist. Conversely, knockdown of S100A6 in SiHa cells decreased the levels of N-cadherin, vimentin, Snail and Twist and increased the levels of epithelial (E)-cadherin. Furthermore, overexpression of S100A6 in HeLa cells activated the phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) signaling pathway, and treatment with the PI3K inhibitor LY294002 partially repressed S100A6-enhanced proliferation and migration of cervical cancer cells. These results indicate that S100A6 facilitates the malignant potential of cervical cancer cells, particularly metastatic ability and epithelial-mesenchymal transition, which is mediated by activating the PI3K/Akt signaling pathway.

Metallo-Toehold-Activated Catalytic Hairpin Assembly Formation of Three-Way DNAzyme Junctions for Amplified Fluorescent Detection of Hg2.

Because of their irreversible toxicological impacts on the environment and human body, the development of reliable and sensitive Hg2+ detection methods with high selectivity is of great significance. On the basis of the substantial signal amplification by metallo-toehold-triggered, catalytic hairpin assembly (CHA) formation of three-way DNAzyme junctions, we have constructed a highly selective and sensitive fluorescent sensing system for the determination of Hg2+ in different environmental water samples. The presence of the target Hg2+ ions can lead to the generation of T-Hg2+-T base mismatched metallo-toeholds, which trigger the catalytic assembly of three split-DNAzyme containing hairpins to form many Mg2+-dependent DNAzyme junction structures upon binding to the fluorescently quenched substrate sequences. The Mg2+ ions then cyclically cleave the fluorescently quenched substrate sequences of the Mg2+-dependent DNAzymes to generate drastically enhanced fluorescent signals for sensitively detecting Hg2+ at the low 4.5 pM level. The developed sensing method offers high selectivity toward the target Hg2+ over other possible competing metal ions due to the specific T-Hg2+-T bridge structure chemistry in the metallo-toehold domain, and reliable detection of spiked Hg2+ in environmentally relevant water samples with this method is also verified. Considering the nucleic acid nature of the trigger and assembly sequences, the developed approach thus holds great potentials for designing new enzyme-free signal amplification strategies to achieve highly sensitive determination of different DNA and RNA targets.

Development of the aza-crown ether metal complexes as artificial hydrolase.

Hydrolases play a crucial role in the biochemical process, which can catalyze the hydrolysis of various compounds like carboxylic esters, phosphoesters, amides, nucleic acids, peptides, and so on. The design of artificial hydrolases has attracted extensive attention due to their scientific significance and potential applications in the field of gene medicine and molecular biology. Numerous macrocyclic metal complexes have been used as artificial hydrolase in the catalytic hydrolysis of the organic substrate. Aza-crown ether for this comment is a special class of the macrocyclic ligand containing both the nitrogen atoms and oxygen atoms in the ring. The studies showed that the aza-crown complexes exhibited high activity of hydrolytic enzyme. However, the aza-crown ether metal complex as artificial hydrolase is still very limited because of its difficulty in synthesis. This review summarizes the development of the aza-crown ether metal complexes as the artificial hydrolase, including the synthesis and catalysis of the transition metal complexes and lanthanide metal complexes of aza-crown ethers. The purpose of this review is to highlight: (1) the relationship between the structure and hydrolytic activity of synthetic hydrolase; (2) the synergistic effect of metal sites and ligands in the course of organic compound hydrolysis; and (3) the design strategies of the aza-crown ethers as hydrolase.

S100A8 facilitates the migration of colorectal cancer cells through regulating macrophages in the inflammatory microenvironment.

Previous studies have shown that S100 calcium-binding protein A8 (S100A8) contributes to the survival and migration of colorectal cancer (CRC) cells. However, whether S100A8 participates in the progression and metastasis of CRC via the regulation of macrophages in the tumor inflammatory microenvironment remains unknown. In this study, phorbol myristate acetate (PMA) was used to induce the differentiation of THP-1 monocytes to macrophages. MTT assay, western blot analysis, immunofluorescence staining, semi-quantitative RT-PCR (semi-PCR), quantitative real-time PCR (qPCR), Gaussia luciferase activity assay and ELISA were performed to analyze the roles and molecular mechanisms of S100A8 in the modulation of macrophages. MTT assay, flow cytometric analysis, Hoechst staining, wound healing and Transwell migration assay were used to test the effect of S100A8 on the viability and migration of CRC cells co-cultured with macrophages in the inflammatory microenvironment. We found that THP-1 monocytes were induced by PMA and differentiated to macrophages. S100A8 activated the NF-κB pathway in the macrophages and promoted the expression of miR-155 and inflammatory cytokines IL-1ß and TNF-α in the inflammatory microenvironment mimicked by lipopolysaccharides (LPS). Furthermore, S100A8 contributed to augment the migration but not the viability of the CRC cells co-cultured with the macrophages in the inflammatory microenvironment. Altogether, our study demonstrated that S100A8 facilitated the migration of CRC cells in the inflammatory microenvironment, and the underlying molecular mechanisms may be partially attributed to the overexpression of miR-155, IL-1ß and TNF-α through activation of the NF-κB pathway in macrophages.

Multiplexed electrochemical coding of DNA-protein bindings.

A simple, sensitive and multiplexed electrochemical sensor for the detection of DNA-protein binding based on the exonuclease protection strategy is described. Two electroactive species, methylene blue (MB)- and ferrocene (Fc)-labeled dsDNA probes are self-assembled on a gold electrode to prepare the sensor surface. The target proteins, vascular endothelial growth factor (VEGF) and estrogen receptor (ERα), bind to the dsDNA probes and protect the probes from digesting by exonuclease III due to the steric hindrance of the bound proteins. These protein-protected, MB/Fc-labeled sequences remaining on the sensor surface display two distinct voltammetric peaks, whose peak potentials (MB: -0.27 V; Fc: +0.27 V) and intensities reflect the identities and amounts of the corresponding target proteins, for simultaneous and multiplexed detection of DNA-protein bindings. The proposed sensor is also selective to the target proteins against other interference molecules. By using labels with distinct voltammetric peaks, the developed method can be easily expanded for simultaneous detection of multiple DNA-protein bindings.

Terminal protection of small molecule-linked ssDNA for label-free and sensitive fluorescent detection of folate receptor.

In this work, based on terminal protection of folate-linked ssDNA (FA-ssDNA) and the SYBR Gold fluorescent dye, we describe the development of a label-free fluorescent strategy for the detection of folate receptors (FRs). The binding between the target FR and the FA moiety of the FA-ssDNA protects the FR bound FA-ssDNA from digesting by Exo I. The binding of SYBR Gold to the terminal protected, un-digested FA-ssDNA leads to enhanced fluorescent emission for the monitoring of FR with a detection limit of 30 pM. Besides, the developed method also shows high selectivity toward FR against other control proteins. Moreover, our approach avoids the labeling of the probes with fluorescent tags and achieves label-free detection of FR. With these advantages, the proposed method thus holds promising potential for the development of simple and convenient strategies for the detection of other proteins by using different small molecule receptor/protein ligand pairs.