A Simple Electrochemical Cytosensor Array for Dynamic Analysis of Carcinoma Cell Surface Glycans

In Situ Glycan Analysis and Editing in Living Systems

Besides proteins and nucleic acids, carbohydrates are also ubiquitous building blocks of living systems. Approximately 70% of mammalian proteins are glycosylated. Glycans not only provide structural support for living systems but also act as crucial regulators of cellular functions. As a result, they are considered essential pieces of the life science puzzle. However, research on glycans has lagged far behind that on proteins and nucleic acids. The main reason is that glycans are not direct products of gene coding, and their synthesis is nontemplated. In addition, the diversity of monosaccharide species and their linkage patterns contribute to the complexity of the glycan structures, which is the molecular basis for their diverse functions. Research in glycobiology is extremely challenging, especially for the in situ elucidation of glycan structures and functions. There is an urgent need to develop highly specific glycan labeling tools and imaging methods and devise glycan editing strategies. This Perspective focuses on the challenges of in situ analysis of glycans in living systems at three spatial levels (i.e., cell, tissue, and in vivo) and highlights recent advances and directions in glycan labeling, imaging, and editing tools. We believe that examining the current development landscape and the existing bottlenecks can drive the evolution of in situ glycan analysis and intervention strategies and provide glycan-based insights for clinical diagnosis and therapeutics.

Arginine-modified black phosphorus quantum dots with dual excited states for enhanced electrochemiluminescence in bioanalysis

The electrochemiluminescence (ECL) is generally emitted via radiative transition of singlet or triplet excited state (S₁ or T₁). Herein, an ECL mechanism with the transitions of both S₁ and T₁ of black phosphorus quantum dots (BPQDs) is found, and an arginine (Arg) modification strategy is proposed to passivate the surface oxidation defects of BPQDs, which could modulate the excited states for enhancing the ECL efficiency of BPQDs. The Arg modification leads to greater spatial overlap of highest and lowest occupied molecular orbitals, and spectral shift of radiative transitions, and improves the stability of anion radical of BPQDs. To verify the application of the proposed mechanism, it is used to construct a sensitive method for conveniently evaluating the inhibiting efficiency of cyclo-arginine-glycine-aspartic acid-d-tyrosine-lysine to cell surface integrin by using Arg containing peptide modified BPQDs as signal tag. The dual excited states mediated ECL emitters provide a paradigm for adjustable ECL generation and extend the application of ECL analysis.

Glycan Labeling and Analysis in Cells and In Vivo

As one of the major types of biomacromolecules in the cell, glycans play essential functional roles in various biological processes. Compared with proteins and nucleic acids, the analysis of glycans in situ has been more challenging. Herein we review recent advances in the development of methods and strategies for labeling, imaging, and profiling of glycans in cells and in vivo. Cellular glycans can be labeled by affinity-based probes, including lectin and antibody conjugates, direct chemical modification, metabolic glycan labeling, and chemoenzymatic labeling. These methods have been applied to label glycans with fluorophores, which enables the visualization and tracking of glycans in cells, tissues, and living organisms. Alternatively, labeling glycans with affinity tags has enabled the enrichment of glycoproteins for glycoproteomic profiling. Built on the glycan labeling methods, strategies enabling cell-selective and tissue-specific glycan labeling and protein-specific glycan imaging have been developed. With these methods and strategies, researchers are now better poised than ever to dissect the biological function of glycans in physiological or pathological contexts.

Monose-modified organic electrochemical transistors for cell surface glycan analysis via competitive recognition to enzyme-labeled lectin

A competitive strategy for glycan determination on cell surface with organic electrochemical transistors (OECTs) has been developed. The carboxylic multi-wall carbon nanotubes were firstly immobilized on the gate interface to cross-link the specific monose with adipic dihydrazide as the linker, which could then competitively recognize horseradish peroxidase (HRP)-labeled lectin with the target monose on the cell surface. The HRP captured on the gate interface through the affinity of lectin to monose finally catalyzed the reduction of hydrogen peroxide to produce the output current signal for detection of cell surface monose under the optimal gate voltage of 0.9 V. Using mannose and galactose groups as the target models, HRP-labeled concanavalin A and peanut agglutinin were used to competitively recognize these groups on both cell surface and gate interface, respectively. The amounts of mannose and galactose on HeLa cells were measured to be 3.41 × 10⁸ and 2.92 × 10⁸ molecules per cell, respectively. The changes of the mannose and galactose expressions upon external stimulation were also observed with the proposed biosensors, which showed consistent results with flow cytometric analysis, indicating that the OECT-based biosensor is suitable for analysis of different glycan expressions on cell surface. Graphical abstract.

A Nature-Inspired Metal-Organic Framework Discriminator for Differential Diagnosis of Cancer Cell Subtypes

Metabolic glycan labeling (MGL) followed by bioorthogonal chemistry provides a powerful tool for tumor imaging and therapy. However, selectively metabolic labeling of cells or tissues of interest remains a challenge. Particularly, owing to tumor heterogeneity including tumor subtypes and interpatient heterogeneity, it is far more difficult to realize tumor-cell-selective metabolic labeling for precise diagnosis. Inspired by nature, we designed azidosugar-functionalized metal-organic frameworks camouflaged with cancer cell membranes to accomplish cancer-cell-selective MGL in vivo. With abundant receptors, this biomimetic platform not only selectively targets homotypic cells but also realizes different breast cancer subtype-selective MGL. Moreover, the endo/lysosomal-escaped ZIF-8 can make azidosugar escape from lysosomes and accelerate its metabolic incorporation. This strategy also takes advantage of cancer-tissue-derived cell membranes, which may have huge potential for personalized diagnosis and therapy.

Antibody glycosylation in autoimmune diseases

The glycosylation of the fragment crystallizable (Fc) region of immunoglobulins (Ig) is critical for the modulation of antibody effects on inflammation. Moreover, antibody glycosylation may induce pathologic modifications and ultimately contribute to the development of autoimmune diseases. Thanks to progress in the analysis of glycosylation, more data are available on IgG and its subclass structures in the context of autoimmune diseases. In this review, we focused on the impact of Ig glycosylation in autoimmunity, describing how it modulates the immune response and how glycome profiles can be used as biomarkers of disease activity. The analysis of antibody glycosylation demonstrated specific features in human autoimmune and chronic inflammatory conditions, including rheumatoid arthritis, systemic lupus erythematosus, inflammatory bowel disease and autoimmune liver diseases, among others. Within the same disease, different patterns are associated with disease severity and treatment options. Future research may increase the information available on the distinct glycome profiles and expand their potential role as biomarkers and as targets for treatment, ultimately favoring an individualized approach.

A facile strategy for quantitative sensing of glycans on cell surface using organic electrochemical transistors

This work designed a facile sensing strategy for quantitation of glycans on cell surface using organic electrochemical transistors (OECTs). The sensing strategy was performed by covalently binding target cells on mercaptopropionic acid modified gate electrode for the recognition of horseradish peroxidase (HRP) labeled lectins to specific glycans on cell surface, which led to sensitive channel current signal responding to the captured HRP and thus the expression of cell surface glycans. The quantitation of glycans on cell surface was achieved by using glycan modified microspheres to simulate the cells, on which the amounts of glycans were detected with enzyme linked immunosorbent assay. The proposed sensing strategy had been used for the detection of mannose and galactose on HeLa cells with Concanavalin A and peanut agglutinin as the specific lectins, which showed 1.37 × 10⁸ mannose and 1.13 × 10⁸ galactose on each cell, respectively. By treating HeLa cells with exoglycosidases, the mannose and galactose expression levels showed the same changes as those detected with flow cytometric analysis, indicating the practical application of the OECT-based biosensor in cell surface glycan expression analysis.

Polymer-Based Device Fabrication and Applications Using Direct Laser Writing Technology

Polymer materials exhibit unique properties in the fabrication of optical waveguide devices, electromagnetic devices, and bio-devices. Direct laser writing (DLW) technology is widely used for micro-structure fabrication due to its high processing precision, low cost, and no need for mask exposure. This paper reviews the latest research progresses of polymer-based micro/nano-devices fabricated using the DLW technique as well as their applications. In order to realize various device structures and functions, different manufacture parameters of DLW systems are adopted, which are also investigated in this work. The flexible use of the DLW process in various polymer-based microstructures, including optical, electronic, magnetic, and biomedical devices are reviewed together with their applications. In addition, polymer materials which are developed with unique properties for the use of DLW technology are also discussed.

Bifunctional cleavable probes for in situ multiplexed glycan detection and imaging using mass spectrometry

In situ analysis of glycans is of great significance since they mediate a range of biological activities. Aberrant changes of glycosylation are closely related to cancer onset and progression. In this work, bifunctional laser cleavable mass probes (LCMPs) were developed for in situ glycan detection from both cells and tissues using laser desorption ionization mass spectrometry (LDI-MS). Specific recognition of glycans was achieved by lectins, and inherent signal amplification was achieved by the conversion of the detection of glycans to that of mass tags which overcame the low ionization efficiency and complicated mass spectra of glycans. Multiplexed glycan profiling was easy to implement due to the simple and generic synthetic route to LCMPs and serial alternative mass tags, which offers high sensitivity, low interference and in situ detection of glycans. Moreover, as an excellent inherent matrix, LCMPs facilitated direct glycan detection from the cell surface and tissue imaging using LDI-MS. Intrinsic and fine glycan distribution in human cancer and paracancerous tissues was strictly demonstrated by MS imaging to explore the correlation between glycosylation and various cancers. This approach presented a versatile LDI-MS based platform for fast and in situ multiplexed glycan engineering, thus providing a new perspective in glycobiology and clinical diagnosis.

Near-Infrared Light Excited and Localized Surface Plasmon Resonance-Enhanced Photoelectrochemical Biosensing Platform for Cell Analysis

Under near-infrared (NIR) light of 810 nm wavelength for irradiation, a very simple and highly sensitive photoelectrochemical (PEC) biosensing platform has been established using the localized surface plasmon resonance effect of Au nanoparticles (NPs) as signal amplification for the nondestructive analysis of living cells. The water-dispersible Ag₂S quantum dots (QDs) synthesized by a one pot method were employed as photoelectrochemically active species, and they exhibited excellent PEC properties irradiated with NIR light which was chosen due to the obvious absorption and fluorescent emission in the NIR light region. After the incorporation of Au NPs on the Ag₂S QDs modified ITO electrode, the photoelectric conversion efficiency was greatly increased, at ∼2.5 times that of the pure Ag₂S QDs modified electrode. Additionally, 4-mercaptophenylboronic acid (MPBA) molecules, as recognition elements, self-assembled on the electrode surface through Au-S bonds. On the basis of the chemical reaction between sialic acid on the cytomembranes and boric acid of MPBA, the very simple PEC biosensing platform was used for the quantitative determination of MCF-7 cells and dynamic evaluation of cell surface glycan expression under the external stimulus of sialidase. Under NIR light of 810 nm and a potential of 0.15 V, this proposed strategy exhibited a wide linear range from 1 × 10² to 1 × 10⁷ cells/mL, with an experimental detection limit of 100 cells/mL. Importantly, this work provided a promising application for NIR Ag₂S QDs coupled with Au NPs in the development of a novel PEC biosensing platform for the nondestructive analysis of biological samples.

Organic Electrochemical Transistors for the Detection of Cell Surface Glycans

Cell surface glycans play critical roles in diverse biological processes, such as cell-cell communication, immunity, infection, development, and differentiation. Their expressions are closely related to cancer growth and metastasis. This work demonstrates an organic electrochemical transistor (OECT)-based biosensor for the detection of glycan expression on living cancer cells. Herein, mannose on human breast cancer cells (MCF-7) as the target glycan model, poly dimethyl diallyl ammonium chloride-multiwall carbon nanotubes (PDDA-MWCNTs) as the loading interface, concanavalin A (Con A) with active mannose binding sites, aptamer and horseradish peroxidase co-immobilized gold nanoparticles (HRP-aptamer-Au NPs) as specific nanoprobes are used to fabricate the OECT biosensor. In this strategy, PDDA-MWCNT interfaces can enhance the loading of Con A, and the target cells can be captured through Con A via active mannose binding sites. Thus, the expression of cell surface can be reflected by the amount of cells captured on the gate. Specific nanoprobes are introduced to the captured cells to produce an OECT signal because of the reduction of hydrogen peroxide catalyzed by HRP conjugated on Au nanoparticles, while the aptamer on nanoprobes can selectively recognize the MCF-7 cells. It is reasonable that more target cells are captured on the gate electrode, more HRP-nanoprobes are loaded thus a larger signal response. The device shows an obvious response to MCF-7 cells down to 10 cells/μL and can be used to selectively monitor the change of mannose expression on cell surfaces upon a treatment with the N-glycan inhibitor. The OECT-based biosensor is promising for the analysis of glycan expressions on the surfaces of different types of cells.

In Situ Cellular Glycan Analysis

Glycan decorates all mammalian cell surfaces through glycosylation, which is one of the most important post-modifications of proteins. Glycans mediate a wide variety of biological processes, including cell growth and differentiation, cell-cell communication, immune response, pathogen interaction, and intracellular signaling events. Besides, tumor cells aberrantly express distinct sets of glycans, which can indicate different tumor onsets and progression processes. Thus, analysis of cellular glycans may contribute to understanding of glycan-related biological processes and correlation of glycan patterns with disease states for clinical diagnosis and treatment. Although proteomics and glycomics have included great efforts for in vitro study of glycan structures and functions using lysis samples of cells or tissues, they cannot offer real-time qualitative or quantitative information, especially spatial distribution, of glycans on/in intact cells, which is important to the revelation of glycan-related biological events. Moreover, the complex lysis and separation procedures may bring unpredictable loss of glycan information. Focusing on the great urgency for in situ analysis of cellular glycans, our group developed a series of methods for in situ analysis of cellular glycans in the past 10 years. By construction of electrochemical glycan-recognizable probes, glycans on the cell surface can be quantified by direct or competitive electrochemical detection. Using multichannel electrodes or encoded lectin probes, multiple glycans on the cell surface can be dynamically monitored simultaneously. Through design of functional nanoprobes, the cell surface protein-specific glycans and intracellular glycan-related enzymes can be visualized by fluorescence or Raman imaging. Besides, some biological enzymes-based methods have been developed for remodeling or imaging of protein-specific glycans and other types of glycoconjugates, such as gangliosides. Through tracing the changes of glycan expression induced by drugs or gene interference, some glycan-related biological processes have been deduced or proved, demonstrating the reliability and practicability of the developed methods. This Account surveys the key technologies developed in this area, along with the discussion on the shortages of current methodology as well as the possible strategies to overcome those shortages. The future trend in this topic is also discussed. It is expected that this Account can provide a versatile arsenal for chemical and biological researchers to unravel the complex mechanisms involved in glycan-related biological processes and light new beacons in tumor diagnosis and treatment.

Binding-responsive catalysis of Taq DNA polymerase for the sensitive and selective detection of cell-surface proteins

Here we develop a new method for the sensitive and selective detection of cell-surface proteins with an aptamer probe designed for binding-responsive catalysis of Taq DNA polymerase. Taking the biotin receptor as a model, the method allows the detection of target protein on surfaces of different types of cancer cells.

Quantum dots: from fluorescence to chemiluminescence, bioluminescence, electrochemiluminescence, and electrochemistry

During the past decade, nanotechnology has become one of the major forces driving basic and applied research. As a novel class of inorganic fluorochromes, research into quantum dots (QDs) has become one of the fastest growing fields of nanotechnology today. QDs are made of a semiconductor material with tunable physical dimensions as well as unique optoelectronic properties, and have attracted multidisciplinary research efforts to further their potential bioanalytical applications. Recently, numerous optical properties of QDs, such as narrow emission band peaks, broad absorption spectra, intense signals, and remarkable resistance to photobleaching, have made them biocompatible and sensitive for biological assays. In this review, we give an overview of these exciting materials and describe their potential, especially in biomolecules analysis, including fluorescence detection, chemiluminescence detection, bioluminescence detection, electrochemiluminescence detection, and electrochemical detection. Finally, conclusions are made, including highlighting some critical challenges remaining and a perspective of how this field can be expected to develop in the future.

Bioinspired Pollen-Like Hierarchical Surface for Efficient Recognition of Target Cancer Cells

The efficient recognition and isolation of rare cancer cells holds great promise for cancer diagnosis and prognosis. In nature, pollens exploit spiky structures to realize recognition and adhesion to stigma. Herein, a bioinspired pollen-like hierarchical surface is developed by replicating the assembly of pollen grains, and efficient and specific recognition to target cancer cells is achieved. The pollen-like surface is fabricated by combining filtering-assisted assembly and soft lithography-based replication of pollen grains of wild chrysanthemum. After modification with a capture agent specific to cancer cells, the pollen-like surface enables the capture of target cancer cells with high efficiency and specificity. In addition, the pollen-like surface not only assures high viability of captured cells but also performs well in cell mixture system and at low cell density. This study represents a good example of constructing cell recognition biointerfaces inspired by pollen-stigma adhesion.

Spontaneous and specific binding of enterohemorrhagic Escherichia coli to overoxidized polypyrrole-coated microspheres

Specific identification of enterohemorrhagic Escherichia coli was achieved using microspheres coated with overoxidized polypyrrole.

Functionalized magnetic microparticle-based colorimetric platform for influenza A virus detection

A colorimetric platform for influenza A virus detection was developed by using the high efficiency of enzymatic catalysis and the reduction of gold ions with hydrogen peroxide. Aptamer-functionalized magnetic microparticles were synthesized to capture the influenza A virus. This was followed by the binding of ConA-GOx-AuNPs to the H3N2 virus through the ConA-glycan interaction. The sandwich complex was subsequently dispersed in glucose solution to trigger an enzymatic reaction to produce hydrogen peroxide, which controlled the growth of gold nanoparticles and produced colored solutions. The determination of H3N2 concentration was realized by comparing the two differently colored gold nanoparticles. This method could detect the target virus as low as 11.16 μg ml(-1). Furthermore, it opens new opportunities for sensitive and colorimetric detection of viruses and proteins.

Electrochemical estrogen screen method based on the electrochemical behavior of MCF-7 cells

It was an urgent task to develop quick, cheap and accurate estrogen screen method for evaluating the estrogen effect of the booming chemicals. In this study, the voltammetric behavior between the estrogen-free and normal fragmented MCF-7 cell suspensions were compared, and the electrochemical signal (about 0.68V attributed by xanthine and guanine) of the estrogen-free fragmented MCF-7 cell suspension was obviously lower than that of the normal one. The electrochemistry detection of ex-secretion purines showed that the ability of ex-secretion purines of cells sharp decreased due to the removing of endogenous estrogen. The results indicated that the electrochemical signal of MCF-7 cells was related to the level of intracellular estrogen. When the level of intracellular estrogen was down-regulated, the concentrations of the xanthine and hypoxanthine decreased, which led to the electrochemical signal of MCF-7 cells fall. Based on the electrochemical signal, the electrochemical estrogen screen method was established. The estrogen effect of estradiol, nonylphenol and bisphenol A was evaluated with the electrochemical method, and the result was accordant with that of MTT assay. The electrochemical estrogen screen method was simple, quickly, cheap, objective, and it exploits a new way for the evaluation of estrogenic effects of chemicals.

Electrocatalytic reduction of a coreactant using a hemin–graphene–Au nanoparticle ternary composite for sensitive electrochemiluminescence cytosensing

A sensitive electrochemiluminescence cytosensor was designed using a hemin–RGO–Au ternary composite with high electrocatalytic activity for H₂O₂ reduction.

An electrochemical glycan biosensor based on a thionine-bridged multiwalled carbon nanotube/gold nanoparticle composite-modified electrode

A MWCNT/Th/AuNP composite, used to construct an electrochemical biosensor for the mannose assay of living cancer cells, contained thionine as an electron mediator and simplified detection based on enzymatic catalysis for signal amplification.

Reusable and dual-potential responses electrogenerated chemiluminescence biosensor for synchronously cytosensing and dynamic cell surface N-glycan evaluation

A novel reusable and dual-potential responsive electrogenerated chemiluminescence (ECL) biosensor was fabricated for synchronous detection of cancer cells and their surface N-glycan. In this strategy, a cancer cell recognized aptamer hybridized with a capture DNA was immobilized on electrochemically reduced MoS2 nanosheets, and Ru(phen)3(2+) as ECL probes was intercalated into the grooves of the double-strand DNA. In the presence of target cells, the capture DNA and Ru(phen)3(2+) were released from the electrode interface owing to the specific interaction between cancer cells and the aptamer. Meanwhile, concanavalin A (Con A), a mannose binding protein, and a conjugated gold nanoparticle modified graphite-C3N4 (Con A@Au-C3N4) was used as a negative ECL nanoprobe and applied for the cell surface N-glycan evaluation owing to the excellent ECL properties of g-C3N4 at negative potential. The cytosensing and cell surface N-glycan evaluation could be simultaneously realized with high sensitivity and excellent selectivity based on the ratio of ECL intensity between the negative potential and positive potential (ΔECLn/ΔECLp), avoiding the traditional routing cell counting procedures. Moreover, the aptamer modified electrode can be regenerated in the presence of capture DNA solutions for cyclic utilization. As a proof-of-concept, the ECL cytosensor showed excellent performances for the analysis of the MCF-7 cancer cell and its surface N-glycan evaluation in human serum samples. The reusable and dual potential response ECL biosensor endows a feasibility tool for clinical diagnosis and drug screening especially in complex biological systems.

Ultrasensitive detection of cancer cells and glycan expression profiling based on a multivalent recognition and alkaline phosphatase-responsive electrogenerated chemiluminescence biosensor

A multivalent recognition and alkaline phosphatase (ALP)-responsive electrogenerated chemiluminescence (ECL) biosensor for cancer cell detection and in situ evaluation of cell surface glycan expression was developed on a poly(amidoamine) (PAMAM) dendrimer-conjugated, chemically reduced graphene oxide (rGO) electrode interface. In this strategy, the multivalency and high affinity of the cell-targeted aptamers on rGO provided a highly efficient cell recognition platform on the electrode. The ALP and concanavalin A (Con A) coated gold nanoparticles (Au NPs) nanoprobes allowed the ALP enzyme-catalyzed production of phenols that inhibited the ECL reaction of Ru(bpy)3(2+) on the rGO electrode interface, affording fast and highly sensitive ECL cytosensing and cell surface glycan evaluation. Combining the multivalent aptamer interface and ALP nanoprobes, the ECL cytosensor showed a detection limit of 38 CCRF-CEM cells per mL in human serum samples, broad dynamic range and excellent selectivity. In addition, the proposed biosensor provided a valuable insight into dynamic profiling of the expression of different glycans on cell surfaces, based on the carbohydrates recognized by lectins applied to the nanoprobes. This biosensor exhibits great promise in clinical diagnosis and drug screening.

Sensitive electrochemical aptamer biosensor for dynamic cell surface N-glycan evaluation featuring multivalent recognition and signal amplification on a dendrimer-graphene electrode interface

We demonstrate a multivalent recognition and highly selective aptamer signal amplification strategy for electrochemical cytosensing and dynamic cell surface N-glycan expression evaluation by the combination of concanavalin A (Con A), a mannose binding protein, as a model, conjugated poly(amidoamine) dendrimer on a chemically reduced graphene oxide (rGO-DEN) interface, and aptamer- and horseradish peroxidase-modified gold nanoparticles (HRP-aptamer-AuNPs) as nanoprobes. In this strategy, the rGO-DEN can not only enhance the electron transfer ability but also provide a multivalent recognition interface for the conjugation of Con A that avoids the weak carbohydrate-protein interaction and dramatically improves the cell capture efficiency and the sensitivity of the biosensor for cell surface glycan. The high-affinity aptamer- and HRP-modified gold nanoparticles provide an ultrasensitive electrochemical probe with excellent specificity. As proof-of-concept, the detection of CCRF-CEM cell (human acute lymphoblastic leukemia) and its surface N-glycan was developed. It has demonstrated that the as-designed biosensor can be used for highly sensitive and selective cell detection and dynamic evaluation of cell surface N-glycan expression. A detection limit as low as 10 cells mL(-1) was obtained with excellent selectivity. Moreover, this strategy was also successfully applied for N-glycan expression inhibitor screening. These results imply that this biosensor has potential in clinical diagnostic and drug screening applications and endows a feasibility tool for insight into the N-glycan function in biological processes and related diseases.

Fabrication of magneto-controlled moveable architecture to develop reusable electrochemical biosensors

Electrochemical biosensors have been studied intensively for several decades. Numerous sensing concepts and related interface architectures have been developed. However, all such architectures suffer a trade-off: simple architectures favour usability, whereas complex architectures favour better performance. To overcome this problem, we propose a novel concept by introducing a magneto-controlled moveable architecture (MCMA) instead of the conventional surface-fixed architecture. As a model, human breast cancer cells were used in this study. The results showed that a detection range from 100 to 1 × 10⁶ cells could be achieved. Moreover, the whole detection cycle, including the measurement and the regeneration, could be completed in only 2 min. Thus, usability and excellent performance can be achieved in a single biosensor.

Three-dimensional nano-biointerface as a new platform for guiding cell fate

The recent explorations of three-dimensional nano-biointerfaces for cell-related fundamental biological studies and advanced biomedical applications are reviewed.

A new hybrid signal amplification strategy for ultrasensitive electrochemical detection of DNA based on enzyme-assisted target recycling and DNA supersandwich assemblies

A highly sensitive electrochemical sequence-specific DNA detection strategy is demonstrated by coupling N.BstNB I (a nicking endonuclease)-assisted target recycling amplification with DNA supersandwich assembly signal enhancement. The proposed method avoids any extra chemical labeling steps and offers high selectivity against single-base mismatch sequences and a low detection limit down to 0.36 fM.

Profiling surface glycans on live cells and tissues using quantum dot-lectin nanoconjugates

The surface of mammalian cells is densely coated with complex glycans, which are directly involved in cell-cell or cell-protein interactions that trigger various biological responses. Here, we present a novel glycomics approach that uses quantum dot (Qdot)-lectin nanoconjugates to interrogate the surface glycans of tissues and patterned cells. Our approach allows highly sensitive in situ monitoring of specific lectin-glycan interactions and quantitative information on surface glycans for each examined cell line and tissue. The results clearly show significant changes in glycosylation for each cell line and tissue sample. We expect that these results will be applicable in cancer diagnostics and promote the development of new analytical tools for glycomics.

Signal amplification using functional nanomaterials for biosensing

Signal amplification based on biofunctional nanomaterials has recently attracted considerable attention due to the need for ultrasensitive bioassays and the trend towards miniaturized assays. The biofunctional nanomaterials can not only produce a synergic effect among catalytic activity, conductivity and biocompatibility to accelerate the signal transduction, but also provide amplified recognition events by high loading of signal tags, leading to a highly sensitive and specific biosensing. Most importantly, nanoscaled materials are in direct contact with the environment, which permits them to act as chemical and biological sensors in single-molecule detection of biomolecules. In this tutorial review, we will focus on recent significant advances in signal amplification strategies combining the cross-disciplines of chemistry, biology, and materials science, and highlight some elegant applications of biofunctional nanomaterials as excellent electronic or optical signal tags in ultrasensitive bioanalysis. The biofunctional nanomaterials-based biosensing opens a series of concepts for basic research and offers new tools for detection of trace amounts of a wide variety of analytes in clinical, environmental, and industrial applications.