Sensitive and selective detection of Mucin1 in pancreatic cancer using hybridization chain reaction with the assistance of Fe3O4@polydopamine nanocomposites.

Pancreatic cancer is characterized as the worst for diagnosis lacking symptoms at the early stage, which results in a low overall survival rate. The frequently used techniques for pancreatic cancer diagnosis rely on imaging and biopsy, which have limitations in requiring experienced personnel to operate the expensive instruments and analyze the results. Therefore, there is a high demand to develop alternative tools or methods to detect pancreatic cancer. Herein, we propose a new strategy to enhance the detection sensitivity of pancreatic cancer cells both in biofluids and on tissues by combining the unique property of dopamine coated Fe3O4 nanoparticles (Fe3O4@DOP NPs) to specifically quench and separate free 6-carboxyfluorescein (FAM) labeled DNA (H1-FAM/H2-FAM), and the key feature of hybridization chain reaction (HCR) amplification. We have determined the limit of detection (LOD) to be 21 ~ 41 cells/mL for three different pancreatic cancer cell lines. It was also discovered that the fluorescence intensity of pancreatic cancer cells was significantly higher than that of HPDE-C7 and HepG-2 cells (control cell lines), which express lower MUC1 protein. Moreover, the HCR amplification system was used to identify the cancer cells on pancreatic tissue, which indicated the versatility of our strategy in clinical application. Therefore, the presented detection strategy shows good sensitivity, specificity and has great potential for the diagnosis of pancreatic cancer.

Enhanced Stability of Enzyme Immobilized in Rationally Designed Amphiphilic Aerogel and Its Application for Sensitive Glucose Detection.

Natural enzyme complex with the subunits cooperating with each other could catalyze cascade reactions in biological system but, just like the limitation of free-floating natural enzymes, usually suffer from deactivation in harsh environment such as high temperature. In this study, a purpose-driven design of amphiphilic aerogel working as the enzymes-immobilization substrate to form the multienzyme complex (MEC) was demonstrated. The aerogel was synthesized only by a single polymer poly(vinyl alcohol) (PVA) as well as a surface modulator maleic acid (MA), the incorporation of which tunes the surface wettability. The usage of the amphiphilic aerogel may do favor for multienzyme immobilization, conserving the enzyme conformation as well as stabilizing the enzymes in high temperature. As a typical example, glucose oxidase and hemin were firmly coimmobilized in the aerogel matrix and actively catalyze the cascade reactions of (i) glucose to gluconic acid and (ii) 3,3,5,5-tetramethylbenzidine (TMB) to its oxidized state. The enzymes could resist the degradation under high temperature (70-100 °C) which is witnessed by the rate of decrease in activity was progressively slackened. Taking the advantage of the chromogenic reaction of TMB, a glucose sensor based on aerogel-enzyme composite for glucose detection in whole blood and sweat was established, exhibiting reliable results and satisfactory recovery. The modified aerogel could also withstand multiple physical deformation meantime maintaining good adsorption capacity as well as catalytic performance. The enzymes-loading aerogel model may hopefully contribute to composing sensors based on other analytes.

Polydopamine Nanotubes as an Effective Fluorescent Quencher for Highly Sensitive and Selective Detection of Biomolecules Assisted with Exonuclease III Amplification.

In this work, the effective fluorescence quenching ability of polydopamine nanotubes (PDANTs) toward various fluorescent dyes was studied and further applied to fluorescent biosensing for the first time. The PDANTs could quench the fluorophores with different emission frequencies, aminomethylcoumarin acetate (AMCA), 6-carboxyfluorescein (FAM), 6-carboxytetramethylrhodamine (TAMRA), and Cy5. All the quenching efficiencies reached to more than 97%. Taking advantage of PDANTs' different affinities toward ssDNA and dsDNA and utilizing the complex of FAM-labeled ssDNA and PDANTs as a sensing platform, we achieved highly sensitive and selective detection of human immunodeficiency virus (HIV) DNA and adenosine triphosphate (ATP) assisted with Exonuclease III amplification. The limits of detection (LODs) of HIV DNA and ATP reached to 3.5 pM and 150 nM, respectively, which were all lower than that of previous nanoquenchers with Exo III amplification, and the platform also presented good applicability in biological samples. Fluorescent sensing applications of this nanotube enlightened other targets detection based upon it and enriched the building blocks of fluorescent sensing platforms. This polydopamine nanotube also possesses excellent biocompatibility and biodegradability, which is suitable for future drug delivery, cell imaging, and other biological applications.

A Nanoscale Multichannel Closed Bipolar Electrode Array for Electrochemiluminescence Sensing Platform.

In this work, we report a nanoscale multichannel closed bipolar electrode (BPE) array based on the poly(ethylene terephthalate) (PET) membrane for the first time. With our design, oxidants, coreactants, quenchers, and even biomarkers can be detected in a Ru(bpy)3(2+)/TPA (tripropylamine) electrochemiluminescence (ECL) system. The multichannel PET membrane was etched according to our desire by NaOH, and then Au nanofibers were decorated in the inner region of the channel as a BPE array. Using ECL as a signal readout, a series of targets including TPA, Ru(bpy)3(2+), dopamine, H2O2, alpha-fetoprotein (AFP), and carcino-embryonic antigen (CEA) can be detected with this device. The practical application of the proposed multichannel closed BPE array was verified in the detection of AFP and CEA in human serum with satisfying results. This kind of nanoscale device holds promising potential for multianalysis. More importantly, as the PET membrane used in this device can be etched with a desirable diameter (nano- to microscale) and different BPE array densities (ion tracks of 10(8)/cm(2), 10(6)/cm(2), 10(4)/cm(2)), our design can be served as a useful platform for future advances in nanoscale bipolar electrochemistry.

Anionic Lipid, pH-Sensitive Liposome-Gold Nanoparticle Hybrids for Gene Delivery - Quantitative Research of the Mechanism.

Gene therapy is a potential method for treating a large range of diseases. Gene vectors are widely used in gene therapy for promoting the gene delivery efficiency to the target cells. Here, gold nanoparticles (AuNPs) coated with dimethyldioctadecylammonium bromide (DODAB)/dioleoylphosphatidylethanolamine (DOPE) are synthesized using a facile method for a new gene vector (DODAB/DOPE-AuNPs), which possess 3- and 1.5-fold higher transfection efficiency than those of DODAB-AuNPs and a commercial transfection agent, respectively. Meanwhile, it is nontoxic with concentrations required for effective gene delivery. Imaging and quantification studies of cellular uptake reveal that DOPE increases gene copies in cells, which may be attributed to the smaller size of AuNPs/DNA complexes. The dissociation efficiency of DNA from the endocytic pathway is quantified by incubating with different buffers and investigated directly in the cells. The results suggest that DOPE increases the internalization of AuNPs/DNA complexes and promotes DNA release from early endosomes for the vector is sensitive to the anionic lipid membrane and the decreasing pH along the endocytic pathway. The new vector contains the potential to be the new alternative as gene delivery vector for biomedical applications.

Nanomaterials with enzyme-like characteristics (nanozymes): next-generation artificial enzymes.

Over the past few decades, researchers have established artificial enzymes as highly stable and low-cost alternatives to natural enzymes in a wide range of applications. A variety of materials including cyclodextrins, metal complexes, porphyrins, polymers, dendrimers and biomolecules have been extensively explored to mimic the structures and functions of naturally occurring enzymes. Recently, some nanomaterials have been found to exhibit unexpected enzyme-like activities, and great advances have been made in this area due to the tremendous progress in nano-research and the unique characteristics of nanomaterials. To highlight the progress in the field of nanomaterial-based artificial enzymes (nanozymes), this review discusses various nanomaterials that have been explored to mimic different kinds of enzymes. We cover their kinetics, mechanisms and applications in numerous fields, from biosensing and immunoassays, to stem cell growth and pollutant removal. We also summarize several approaches to tune the activities of nanozymes. Finally, we make comparisons between nanozymes and other catalytic materials (other artificial enzymes, natural enzymes, organic catalysts and nanomaterial-based catalysts) and address the current challenges and future directions (302 references).

Dual-signal readout sensing of ATP content in single dental pulp stem cells during differentiation via functionalized glass nanopipettes.

Adenosine triphosphate (ATP) is regarded as the "energy currency" in living cells, so real-time quantification of content variation of intracellular ATP is highly desired for understanding some important physiological processes. Due to its single-molecule readout ability, nanopipette sensing has emerged as a powerful technique for molecular sensing. In this study, based on the effect of targeting-aptamer binding on ionic current, and fluorescence resonance energy transfer (FRET), we reported a dual-signal readout nanopipette sensing system for monitoring ATP content variation at the subcellular level. In the presence of ATP, the complementary DNA-modified gold nanoparticles (cDNAs-AuNPs) were released from the inner wall of the nanopipette, which leads to sensitive response variations in ionic current rectification and fluorescence intensity. The developed nanopipette sensor was capable of detecting ATP in single cells, and the fluctuation of ATP content in the differentiation of dental pulp stem cells (DPSCs) was further quantified with this method. The study provides a more reliable nanopipette sensing platform due to the introduction of fluorescence readout signals. Significantly, the study of energy fluctuation during cell differentiation from the perspective of energy metabolism is helpful for differentiation regulation and cell therapy.

Functional micro/nanostructures: simple synthesis and application in sensors, fuel cells, and gene delivery.

In order to develop new, high technology devices for a variety of applications, researchers would like to better control the structure and function of micro/nanomaterials through an understanding of the role of size, shape, architecture, composition, hybridization, molecular engineering, assembly, and microstructure. However, researchers continue to face great challenges in the construction of well-defined micro/nanomaterials with diverse morphologies. At the same time, the research interface where micro/nanomaterials meet electrochemistry, analytical chemistry, biomedicine, and other fields provides rich opportunities to reveal new chemical, physical, and biological properties of micro/nanomaterials and to uncover many new functions and applications of these materials. In this Account, we describe our recent progress in the construction of novel inorganic and polymer nanostructures formed through different simple strategies. Our synthetic strategies include wet-chemical and electrochemical methods for the controlled production of inorganic and polymer nanomaterials with well-defined morphologies. These methods are both facile and reliable, allowing us to produce high-quality micro/nanostructures, such as nanoplates, micro/nanoflowers, monodisperse micro/nanoparticles, nanowires, nanobelts, and polyhedron and even diverse hybrid structures. We implemented a series of approaches to address the challenges in the preparation of new functional micro/nanomaterials for a variety of important applications This Account also highlights new or enhanced applications of certain micro/nanomaterials in sensing applications. We singled out analytical techniques that take advantage of particular properties of micro/nanomaterials. Then by rationally tailoring experimental parameters, we readily and selectively obtained different types of micro/nanomaterials with novel morphologies with high performance in applications such as electrochemical sensors, electrochemiluminescent sensors, gene delivery agents, and fuel cell catalysts. We expect that micro/nanomaterials with unique structural characteristics, properties, and functions will attract increasing research interest and will lead to new opportunities in various fields of research.

Solid-state label-free integrated aptasensor based on graphene-mesoporous silica-gold nanoparticle hybrids and silver microspheres.

Taking advantage of strand-displacement DNA polymerization and parallel-motif DNA triplex system as dual amplifications, a new electrochemical label-free integrated aptasensor based on silver microspheres (SMSs) as a separation element and graphene-mesoporous silica-gold nanoparticle (NP) hybrids (GSGHs) as an enhanced element of the sensing platform was first reported. In this sensing design (schematic representation of the sensing procedure for adenosine triphosphate detection, Scheme 1 in manuscript text), which contains an enhanced three-step magnification process, SMSs with "clean" surface were first used to separate the undesirable aptamer and aptamer-adenosine triphosphate (ATP) complex attached on SMSs surface after aptamer-ATP interaction, which lead to the detachment of blocker DNA into the solution phase. Then, under the assistance of blocker DNA, an amplified method based on the inherent signal-transduction mechanism of the hairpin probe and strand-displacement property of DNA polymerase was introduced. The obtained duplex DNA was used to hybridize with an acceptor DNA assembled on electrode to form triplex DNA, which could bring a more obvious detection signal compared with the duplex DNA without the amplification. The electrochemical signal came from the GSGH-based enhanced sensing interface containing positively charged ferrocene-appended poly(ethyleneimine) (Fc-PEI). Using the above multiple effects, we could achieve the sensitive analysis of a model small molecule-ATP (an important "molecular currency" of intracellular energy transfer) in a wide detection range from 0.05 nM to 56.5 nM with the detection limit of 0.023 nM.

Solid-state probe based electrochemical aptasensor for cocaine: a potentially convenient, sensitive, repeatable, and integrated sensing platform for drugs.

Aptamers, which are artificial oligonucleotides selected in vitro, have been employed to design novel biosensors (i.e., aptasensors). In this work, we first constructed a label-free electrochemical aptasensor introducing a probe immobilization technique by the use of a layer-by-layer (LBL) self-assembled multilayer with ferrocene-appended poly(ethyleneimine) (Fc-PEI) on an indium tin oxide (ITO) array electrode for detection of cocaine. The Fc-PEI and gold nanoparticles (AuNPs) were LBL assembled on the electrode surface via electrostatic interaction. Then, cocaine aptamer fragments, SH-C2, were covalently labeled onto the outermost AuNP layer. When the target cocaine and cocaine aptamer C1 were present simultaneously, the SH-C2 layer hybridized partly with C1 to bind the cocaine, which led to a decreased differential pulse voltammetry (DPV) signal of Fc-PEI. This DPV signal change could be used to sensitively detect cocaine with the lowest detectable concentration down to 0.1 microM and the detection range up to 38.8 microM, which falls in the the expected range for medical use of detecting drug abuse involving cocaine. Meanwhile, the sensor was specific to cocaine in complex biologic fluids such as human plasma, human saliva, etc. The sensing strategy had general applicability, and the detection of thrombin could also be realized, displayed a low detection limit, and exhibited worthiness to other analytes. The aptasensor based on the array electrode held promising potential for integration of the sensing ability in multianalysis for simultaneous detection.

Microfabricated on-chip integrated Au-Ag-Au three-electrode system for in situ mercury ion determination.

In this paper, a new two-step photolithography fabrication method is used for the fabrication of an on-chip integrated two-metal electrode system, with a Ag reference electrode and two gold electrodes used as working and counter electrodes, respectively. Combined with a microfluidic channel, the total detector has the advantages of ease of use, low analyte consumption, fast sensing time and is suited for in situ target metal ion determination. Herein, the three-electrode system was used for Hg(2+) ion measurement, and both the capabilities of Au working and Ag reference electrodes were characterized by using electrochemical techniques. The results show that the as-prepared on-chip integrated electrochemical detector performed with high sensitivity and good reproducibility in Hg(2+) determination. The detection range extends from 10 to 1000 ppb with a good linear correlation, and the detection limit is low to 3 ppb (S/N = 3). Our method provides a rapid and effective, miniaturized electrochemical analysis platform in Hg(2+) measurement and demonstrates great potential for the application of in situ or on-line mercuric pollutant analysis.

Ultrasensitive colorimetric detection of protein by aptamer-Au nanoparticles conjugates based on a dot-blot assay.

A simple, rapid and ultrasensitive colorimetric detection of protein using aptamer-Au nanoparticles (AuNPs) conjugates based on a dot-blot array has been developed, which was combined with the unique optical properties of AuNPs, enabling the visual detection of protein within minutes without any instrument.

Investigation of an eco-friendly aerogel as a substrate for the immobilization of MoS2 nanoflowers for removal of mercury species from aqueous solutions.

An adsorbent that exhibits high affinity for inorganic mercury (Hg2+) with a high removal efficiency of methylmercury (MeHg+) has been developed. The adsorbent demonstrates a symbiotic relationship between its two components, molybdenum disulphide nanoflowers (MoS2NFs) and a poly (vinyl alcohol) (PVA) aerogel. Furthermore, we modified the distribution and loading of the MoS2NFs, which was possible due to the stable porous support, and investigated the biocompatibility of the aerogel-support adsorbent. The performance of the optimized material exhibited a distribution coefficient of 9.71 × 107 mL g-1. In addition, the adsorbent was effective over a wide pH range and could efficiently purify both contaminated lake and sea water. The key motivation for using an aerogel support was to stabilise the MoS2NFs during purification of the water (resulting in improved performance compared to using freestanding MoS2NFs) and the ability to regenerate the used adsorbent. In addition, animal tests confirmed an extremely low toxicity of the adsorbent to fish, along with the excellent purification results.

Exploiting Polydopamine Nanospheres to DNA Computing: A Simple, Enzyme-Free and G-Quadruplex-Free DNA Parity Generator/Checker for Error Detection during Data Transmission.

Molecular logic devices with various functions play an indispensable role in molecular data transmission/processing. However, during any kinds of data transmission, a constant and unavoidable circumstance is the appearance of bit errors, which have serious effects on the regular logic computation. Fortunately, these errors can be detected via plugging a parity generator (pG) at the transmitting terminal and a parity checker (pC) at the receiving terminal. Herein, taking advantage of the efficient adsorption/quenching ability of polydopamine nanospheres toward fluorophore-labeled single-stranded DNA, we explored this biocompatible nanomaterial to DNA logic computation and constructed the first simple, enzyme-free, and G-quadruplex-free DNA pG/pC for error detection through data transmission. Besides, graphene oxide (GO) was innovatively introduced as the "corrective element" to perform the output-correction function of pC. All the erroneous outputs were corrected to normal conditions completely, ensuring the regular operation of later logic computing. The total operation of this non-G4 pG/pC system (error checking/output-correction) could be completed within 1 h (about 1/3 of previous G4 platform) in a simpler and more efficient way. Notably, the odd pG/pC with analogous functions was also achieved through negative logic conversion to the fabricated even one. Furthermore, the same system could also perform three-input concatenated logic computation (XOR-INHIBIT), enriching the complexity of PDs-based logic computation.

Smart modification of the single conical nanochannel to fabricate dual-responsive ion gate by self-initiated photografting and photopolymerization.

A simple, rapid and general method of self-initiated photografting and photopolymerization (SIPGP) was first introduced to fabricate dual-responsive nanochannel with a solid-state conical nanopore for the first time. The high density of carboxyl and hydroxyl groups on the internal surface of the etched poly(ethylene terephthalate) (PET) nanochannel acted as photo-active sites to provide further growth and amplification of polymer brushes via SIPGP. Poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) was chosen as a prototypical polymer which can be grafted on the surface of the nanochannel with high efficiency. SIPGP provided a smart and simple strategy to graft polymer brush on the surface of the nanochannel without the need of a surface bonded initiator. Series of characterizations including current-voltage curves, scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) indicated the successful construction of the polymer. The functionalized nanochannel was finally used for the construction of smart gate with perfect responsibility, reversibility and stability towards CO2 and temperature. This modification strategy combined with unique character of the polymer may hold a great potential in building various smart responsive systems.

A polydopamine nanosphere based highly sensitive and selective aptamer cytosensor with enzyme amplification.

With CCRF-CEM as the model cell, a highly sensitive and selective cytosensor was developed by taking advantage of polydopamine nanospheres for the first time. The strategies of aptamer/membrane protein recognition and Exonuclease III assisted cycle amplification were used for improving selectivity and sensitivity. The detection of limit reached was as low as 15 cells per mL.

Attachment of gold nanoparticles to glassy carbon electrode and its application for the direct electrochemistry and electrocatalytic behavior of hemoglobin.

Gold nanoparticles have been attached onto glassy carbon electrode surface through sulfhydryl-terminated monolayer and characterized by X-ray photoelectron spectroscopy, atomic force microscopy, electrochemical impedance spectroscopy and cyclic voltammetry. The gold nanoparticles-attached glassy carbon electrodes have been applied to the immobilization/adsorption of hemoglobin, with a monolayer surface coverage of about 2.1 x 10(-10) mol cm(-2), and consequently obtained the direct electrochemistry of hemoglobin. Gold nanoparticles, acting as a bridge of electron transfer, can greatly promote the direct electron transfer between hemoglobin and the modified glassy carbon electrode without the aid of any electron mediator. In phosphate buffer solution with pH 6.8, hemoglobin shows a pair of well-defined redox waves with formal potential (E0') of about -0.085 V (versus Ag/AgCl/saturated KCl). The immobilized hemoglobin maintained its biological activity, showing a surface controlled electrode process with the apparent heterogeneous electron transfer rate constant (ks) of 1.05 s(-1) and charge-transfer coefficient (a) of 0.46, and displays the features of a peroxidase in the electrocatalytic reduction of hydrogen peroxide. A potential application of the hemoglobin-immobilized gold nanoparticles modified glassy carbon electrode as a biosensor to monitor hydrogen peroxide has been investigated. The steady-state current response increases linearly with hydrogen peroxide concentration from 2.0 x 10(-6) to 2.4 x 10(-4) M. The detection limit (3sigma) for hydrogen peroxide is 9.1 x 10(-7) M.

Mimetic biomembrane-AuNPs-graphene hybrid as matrix for enzyme immobilization and bioelectrocatalysis study.

A hybrid composite constructed of phospholipids bilayer membrane, gold nanoparticles and graphene was prepared and used as matrices for microperoxidase-11 (MP11) immobilization. The direct electrochemistry and corresponding bioelectrocatalysis of the enzyme electrode was further investigated. Phospholipid bilayer membrane protected gold nanoparticles (AuNPs) were assembled on polyelectrolyte functionalized graphene sheets through electrostatic attraction to form a hybrid bionanocomposite. Owing to the biocompatible microenvironment provided by the mimetic biomembrane, microperoxidase-11 entrapped in this matrix well retained its native structure and exhibited high bioactivity. Moreover, the AuNPs-graphene assemblies could efficiently promote the direct electron transfer between the immobilized MP11 and the substrate electrode. The as-prepared enzyme electrode presented good direct electrochemistry and electrocatalytic responses to the reduction of hydrogen peroxide (H2O2). The resulting H2O2 biosensor showed a wide linear range (2.0×10(-5)-2.8×10(-4) M), a low detection limit (2.6×10(-6) M), good reproducibility and stability. Furthermore, this sensor was used for real-time detection of H2O2 dynamically released from the tumor cells MCF-7 in response to a pro-inflammatory stimulant.

PEI/Zr4⁺-coated nanopore for selective and sensitive detection of ATP in combination with single-walled carbon nanotubes.

By virtue of a biomimetic nanopore and single-walled carbon nanotubes, a new sensor for adenosine triphosphate (ATP) detection is designed. As compared to the routine approach, the present scenario does not entail the surface modification of nanopore with analyte-specific probes. The underlying mechanism relies on a symmetric nanopore sequentially modified with polyethyleneimine (PEI) and Zr(4+) that can quantitate the concentration of ATP-bound aptamer, while other free aptamers are removed by single-walled carbon nanotubes (SWNTs). The detection limit of the nanopore sensor is 27.46 nM, and the linear range is from 50 nM to 400 nM. The biosensor with an excellent selectivity against guanosine triphosphate (GTP), uridine triphosphate (UTP), and cytosine triphosphate (CTP) can be applied in the real samples such as Hela cell.

Direct electrochemistry of hemoglobin in egg-phosphatidylcholine films and its catalysis to H(2)O(2).

Direct electrochemistry of hemoglobin was observed in stable thin film composed of a natural lipid (egg-phosphatidylcholine) and hemoglobin on pyrolytic graphite (PG) electrode. Hemoglobin in lipid films shows thin layer electrochemistry behavior. The formal potential E degrees ' of hemoglobin in the lipid film was linearly varied with pH in the range from 3.5 to 7.0 with a slope of -46.4 mV pH(-1). Hemoglobin in the lipid film exhibited elegant catalytic activity for electrochemical reduction of H(2)O(2), based which a unmediated biosensor for H(2)O(2) was developed.