Biocompatible Conductive Architecture of Carbon Nanofiber-Doped Chitosan Prepared with Controllable Electrodeposition for Cytosensing

Competitive electrochemical sensing for cancer cell evaluation based on thionine-interlinked signal probes

The development of effective methods for tracking cancer cells is of significant importance in the early diagnosis and treatment of tumor diseases. Compared with the developed techniques, the electrochemical assay has shown considerable potential for monitoring glycan expression on the cell surface using nondestructive means. However, the application expansion of the electrochemical strategy is strongly impeded owing to its dependence on electroactive species. In this study, a competitive electrochemical strategy was reported for monitoring cancer cells based on mannose (a typical glycan) as a clinical biomarker. Herein, functionalized carbon nanotubes were used to load the thiomannosyl dimer, and thionine-interlinking signal probes were designed for competitive recognition. After effective competition between cancer cells and the anchored mannose, a decreased current was obtained as the cell concentration increased. Under optimal conditions, the proposed biosensor exhibited attractive performance for cancer cell analysis with a detection limit as low as 20 cells per mL for QGY-7701 and 35 cells per mL for QGY-7703, facilitating great promise for the sensitive detection of cancer cells and thus showing potential applications in cancer diagnosis.

Hydrogel Nanoarchitectonics: An Evolving Paradigm for Ultrasensitive Biosensing

The integration of nanoarchitectonics and hydrogel into conventional biosensing platforms offers the opportunities to design physically and chemically controlled and optimized soft structures with superior biocompatibility, better immobilization of biomolecules, and specific and sensitive biosensor design. The physical and chemical properties of 3D hydrogel structures can be modified by integrating with nanostructures. Such modifications can enhance their responsiveness to mechanical, optical, thermal, magnetic, and electric stimuli, which in turn can enhance the practicality of biosensors in clinical settings. This review describes the synthesis and kinetics of gel networks and exploitation of nanostructure-integrated hydrogels in biosensing. With an emphasis on different integration strategies of hydrogel with nanostructures, this review highlights the importance of hydrogel nanostructures as one of the most favorable candidates for developing ultrasensitive biosensors. Moreover, hydrogel nanoarchitectonics are also portrayed as a promising candidate for fabricating next-generation robust biosensors.

Platinum-Based Nanocomposite Pt@BSA as an Efficient Electrochemical Biosensing Interface for Rapid and Ultrasensitive Determination of Folate Receptor-Positive Tumor Cells

Developing a cytosensing strategy based on electrochemical approaches has attracted wide interest due to the low cost, rapid response, and simple instrumentation. In this work, an electrochemical cytosensor employing the Pt@BSA nanocomposite as the biosensing substrate along with the covalent cross-linking of targeting molecules folic acid (FA) was constructed for highly sensitive determination of folate receptor (FR)-positive tumor cells. The prepared Pt@BSA nanocomposite revealed excellent biocompatibility for cell adhesion and proliferation, which was confirmed by cell viability evaluation using thiazolyl blue tetrazolium bromide (MTT) colorimetric methods. Due to the satisfactory electrical conductivity originating from Pt@BSA and the high binding affinity of FA to FR on the cell surface, an ultrasensitive and specific cytosensing device was designed for rapid and quantitative determination of HeLa cells (a model system) by differential pulse voltammetry (DPV) tests. This proposed cytosensor resulted in a wide HeLa cell determination range of 2.8 × 10¹-2.8 × 10⁶ cells mL^-1 with a low DPV detection limit of 9 cells mL^-1. The developed cytosensing approach exhibited highly specific recognition of FR-positive tumor cells, excellent inter-assay reproducibility with a relative standard deviation (RSD) of 4.7%, acceptable intra-assay precision, and favorable storage stability, expanding the application of electrochemical measurement technology in the biomedical field of early detection and diagnosis of cancers.

Highly Sensitive RNA-Based Electrochemical Aptasensor for the Determination of C-Reactive Protein Using Carbon Nanofiber-Chitosan Modified Screen-Printed Electrode

C-reactive protein (CRP) is one of the biomarkers related to coronavirus disease 2019 (COVID-19). Therefore, it is crucial to develop a highly sensitive, selective, and cost-effective biosensor for the determination of CRP. In this study, we designed an electrochemical aptasensor. For this purpose, the surface of a carbon screen-printed electrode was first modified with a carbon nanofiber-chitosan (CNFs-CHIT) nanocomposite. After that, the amino-terminal RNA aptamer probes were linked to the amino groups of CHIT via glutaraldehyde as the cross-linker. Finally, methylene blue (MB) as a redox probe was self-assembled on the surface of the aptasensor. The obtained results indicated that the CNFs-CHIT nanocomposite increased the surface coverage of the aptamer up to 5.9 times. The square-wave voltammetry was used for the measurement of CRP concentration in the linear range of 1.0-150.0 pM. The obtained results indicated that the signal had a logarithmic relationship with the concentration of CRP. The limit of detection (LOD) was obtained to be 0.37 pM. The dissociation constant (Kd) that demonstrates the affinity of the aptamer probe to its target was found to be 0.93 pM. The analytical performances of the proposed RNA aptasensor were better than the previously reported aptasensors for CRP. The proposed aptasensor was also applied for the determination of CRP in the human plasma samples. The obtained results indicated that there were no statistically significant differences between the responses of the proposed RNA aptasensor and an enzyme-linked immunosorbent assay kit (ELISA). The analytical performances of the proposed RNA aptasensor described in this paper are better than previously reported aptasensors for CRP determination.

Real-Time NMR Monitoring of Spatially Segregated Enzymatic Reactions in Multilayered Hydrogel Assemblies*

Compartmentalized chemical reactions at the microscale are important in biotechnology, yet monitoring the molecular content at these small scales is challenging. To address this challenge, we integrate a compact, reconfigurable reaction cell featuring electrochemical functionality with high‐resolution NMR spectroscopy. We demonstrate the operation of this system by monitoring the activity of enzymes immobilized in chemically distinct layers within a multi‐layered chitosan hydrogel assembly. As a benchmark, we observed the parallel activities of urease (Urs), catalase (Cat), and glucose oxidase (GOx) by monitoring reagent and product concentrations in real‐time. Simultaneous monitoring of an independent enzymatic process (Urs) together with a cooperative process (GOx + Cat) was achieved, with chemical conversion modulation of the GOx + Cat process demonstrated by varying the order in which the hydrogel was assembled.

Highly Sensitive Electrochemical Biosensor Using Folic Acid-Modified Reduced Graphene Oxide for the Detection of Cancer Biomarker

The detection of cancer biomarkers in the early stages could prevent cancer-related deaths significantly. Nanomaterials combined with biomolecules are extensively used in drug delivery, imaging, and sensing applications by targeting the overexpressed cancer proteins such as folate receptors (FRs) to control the disease by providing earlier treatments. In this investigation, biocompatible reduced graphene oxide (rGO) nanosheets combined with folic acid (FA)-a vitamin with high bioaffinity to FRs-is utilized to develop an electrochemical sensor for cancer detection. To mimic the cancer cell environment, FR-β protein is used to evaluate the response of the rGO-FA sensor. The formation of the rGO-FA nanocomposite was confirmed through various characterization techniques. A glassy carbon (GC) electrode was then modified with the obtained rGO-FA and analyzed via differential pulse voltammetry (DPV) for its specific detection towards FRs. Using the DPV technique, the rGO-FA-modified electrode exhibited a limit of detection (LOD) of 1.69 pM, determined in a linear concentration range from 6 to 100 pM. This excellent electrochemical performance towards FRs detection could provide a significant contribution towards future cancer diagnosis. Moreover, the rGO-FA sensing platform also showed excellent specificity and reliability when tested against similar interfering biomolecules. This rGO-FA sensor offers a great promise to the future medical industry through its highly sensitive detection towards FRs in a fast, reliable, and economical way.

Polydopamine nanoparticles-assisted impedimetric sensor towards label-free lung cancer cell detection

Polydopamine nanoparticles (PDA NPs), among nature-inspired building materials, show special functions for biomedical systems and exploring PDA derived nanostructures for future developments is a fast growing field. Herein, we demonstrated the first evaluation of the PDA NPs for the electrochemical determination of lung cancer cells. In the presented study, PDA NPs were synthesized in a mild and cost-effective fashion by self-polymerization of dopamine in an alkaline environment. The structural and chemical characterizations clearly demonstrated the formation of PDA NPs with controllable size (130 nm), hence applied as a suitable material to functionalize the pencil graphite electrode (PGE) surface to construct a cytosensing nanoprobe. The ability of the developed sensor (PDA NPs/PGE) for label-free electrochemical A-549 lung cancer cells detection was investigated. The designed PDA NPs based cytosensor exhibited good biocompatibility and sensitivity for impedimetric diagnosis of A-549 cells in a wide linear range (1.0 × 10²-1.0 × 10⁵ cells mL^-1) with low detection limit (25 cells mL^-1). Furthermore, the developed bioassay has great potential as liquid biopsy for early cancer detection.

Drug carrier three-layer nanofibrous tube for vascular graft engineering

Currently available synthetic grafts demonstrate moderate success at the macrovascular level, but there are still challenges at small vascular scale (inner diameter of less than 6 mm). In this paper, silk fibroin (SF)/polyurethane (PU)/SF three-layer drug carrier nanofibrous tubes were developed for blood vessel repair with several advantages over existing designs. Our design consisted of a bionic three-layer microtube that was synthesized from the drug carrier SF and oligomeric proanthocyanidin nanofibers as the inner layer, PU nanofibers as the middle layer, and SF nanofibers as the outer layer. The results suggested that these three-layer tubes are attractive biocompatible materials for use as vascular grafts.

An “OFF–ON” quantum dot–graphene oxide bioprobe for sensitive detection of micrococcal nuclease ofStaphylococcus aureus

mAb-Strep-QDs-GO probe in an OFF state due to energy transfer from QDs to GO turns into an ON state when the energy transfer is inhibited by MNase, thus allowing the sensing of MNase (Micrococcal Nuclease, an extracellular endonuclease ofStaphylococcus Aureus).

Synergistic effect of the Pd–Ni bimetal/carbon nanofiber composite catalyst in Suzuki coupling reaction

A novel Pd₁Ni₄ bimetal nanocomposite catalyst was prepared and showed better performance than their monometallic counterpart. What's more, the catalyst could be reused ten times without significant change in catalytic activity, which met the request of sustainable chemistry.

Sensitive detection of MCF-7 human breast cancer cells by using a novel DNA-labeled sandwich electrochemical biosensor

The simple, rapid, sensitive, and specific detection of cancer cells plays a pivotal role in the diagnosis and prognosis of cancer. We developed a novel DNA-labeled sandwich electrochemical biosensor based on a glassy carbon electrode modified with 3D graphene and a hybrid of Au nanocages (Au NCs)/amino-functionalized multiwalled carbon nanotubes (MWCNT-NH₂) for label-free and selective detection of MCF-7 breast cancer cells via differential pulse voltammetry. The layer-by-layer assembly and cell-detection performance of the Au NCs/MWCNTs-NH₂-based biosensor were investigated using scanning electron microscopy and electrochemical methods including cyclic voltammetry and electrochemical impedance spectroscopy. Owing to the advantages of DNA-labeled antibodies and a nanomaterial-based signal amplification strategy, the fabricated cytosensor exhibited high specificity and sensitivity when detecting MCF-7 cells in the range of 1.0 × 10² to 1.0 × 10⁶ cells mL^-1 with a low detection limit of 80 cells mL^-1 (3σ/slope). Furthermore, the biosensor exhibited high selectivity when detecting MCF-7 cells and showed considerable potential for practical applications. The proposed DNA-labeled sandwich electrochemical biosensor provides a stable, sensitive approach to detecting cancer cells and is promising in terms of potential applications to cancer diagnosis.

Fast Preparation of Polydopamine Nanoparticles Catalyzed by Fe2+/H2O2 for Visible Sensitive Smartphone-Enabled Cytosensing

It is highly desired to develop facile methods for fast preparation of polydopamine nanoparticles (PDANS) for intensive promising applications. Considering the system of Fe²⁺/H₂O₂ can generate reactive oxygen species efficiently, which can accelerate the self-oxidative polymerization of dopamine, a new time-saving method has been proposed to prepare PDANS catalyzed by Fe²⁺/H₂O₂. Thereafter, a novel kind of colorimetric nanoprobe for sensitive detection of human breast cancer cells (MDA-MB-231 cell) based on the obtained PDANS-loaded pH indicator molecules (thymolphthalein) has been developed successfully. The loading capacity of PDANS toward thymolphthalein molecules can reach as high as 165.40 mg/g, which will be a great help to enhancing the sensitivity. Following the color change principle of pH indicators, once simply triggered by basic water, the developed cytosensor offers a visible sensitive smartphone-enabled cytosensing of human breast cancer cells. It has been proved that the rational designed cytosensor is favorable to sensitive detection of cancer cells. By the virtue of its easy use, the proposed smartphone-enabled strategy can provide a novel testing approach for point-of-care bioassay beyond cytosensing in remote areas.

Review of Electrochemically Triggered Macromolecular Film Buildup Processes and Their Biomedical Applications

Macromolecular coatings play an important role in many technological areas, ranging from the car industry to biosensors. Among the different coating technologies, electrochemically triggered processes are extremely powerful because they allow in particular spatial confinement of the film buildup up to the micrometer scale on microelectrodes. Here, we review the latest advances in the field of electrochemically triggered macromolecular film buildup processes performed in aqueous solutions. All these processes will be discussed and related to their several applications such as corrosion prevention, biosensors, antimicrobial coatings, drug-release, barrier properties and cell encapsulation. Special emphasis will be put on applications in the rapidly growing field of biosensors. Using polymers or proteins, the electrochemical buildup of the films can result from a local change of macromolecules solubility, self-assembly of polyelectrolytes through electrostatic/ionic interactions or covalent cross-linking between different macromolecules. The assembly process can be in one step or performed step-by-step based on an electrical trigger affecting directly the interacting macromolecules or generating ionic species.

Ultrasensitive electrochemical detection of tumor cells based on multiple layer CdS quantum dots-functionalized polystyrene microspheres and graphene oxide - polyaniline composite

In this work, a novel ultrasensitive electrochemical biosensor was developed for the detection of K562 cell by a signal amplification strategy based on multiple layer CdS QDs functionalized polystyrene microspheres(PS) as bioprobe and graphene oxide(GO) -polyaniline(PANI) composite as modified materials of capture electrode. Due to electrostatic force of different charge, CdS QDs were decorated on the surface of PS by PDDA (poly(diallyldimethyl-ammonium chloride)) through a layer-by-layer(LBL) assemble technology, in which the structure of multiple layer CdS QDs increased the detection signal intensity. Moreover, GO-PANI composite not only enhanced the electron transfer rate, but also increased tumor cells load ratio. The resulting electrochemical biosensor was used to detect K562 cells with a lower detection limit of 3 cellsmL^-1 (S/N = 3) and a wider linear range from 10 to 1.0 × 10⁷ cellsmL^-1. This sensor was also used for mannosyl groups on HeLa cells and Hct116 cells, which showed high specificity and sensitivity. This signal amplification strategy would provide a novel approach for detection, diagnosis and treatment for tumor cells.

Boronic Acid vs. Folic Acid: A Comparison of the bio-recognition performances by Impedimetric Cytosensors based on Ferrocene cored dendrimer

A comparative study is reported where folic acid (FA) and boronic acid (BA) based cytosensors and their analytical performances in cancer cell detection were analyzed by using electrochemical impedance spectroscopy (EIS) method. Cytosensors were fabricated using self-assembled monolayer principle by modifying Au electrode with cysteamine (Cys) and immobilization of ferrocene cored polyamidiamine dendrimers second generation (Fc-PAMAM (G2)), after which electrodes were modified with FA and BA. Au/Fc-PAMAM(G2)/FA and Au/Fc-PAMAM(G2)/BA based cytosensors showed extremely good analytical performances in cancer cell detection with linear range of 1×10² to 1×10⁶cellsml^-1, detection limit of 20cellsml^-1 with incubation time of 20min for FA based electrode, and for BA based electrode detection limit was 28cellsml^-1 with incubation time of 10min. Next to excellent analytical performances, cytosensors showed high selectivity towards cancer cells which was demonstrated in selectivity study using human embryonic kidney 293 cells (HEK 293) as normal cells and Au/Fc-PAMAM(G2)/FA electrode showed two times better selectivity than BA modified electrode. These cytosensors are promising for future applications in cancer cell diagnosis.

Amplified detection of leukemia cancer cells using an aptamer-conjugated gold-coated magnetic nanoparticles on a nitrogen-doped graphene modified electrode

The increasing demands for early, accurate and ultrasensitive diagnosis of cancers demonstrate the importance of the development of new amplification strategies or diagnostic technologies. In the present study, an aptamer-based electrochemical biosensor for ultrasensitive and selective detection of leukemia cancer cells has been introduced. The thiolated sgc8c aptamer was immobilized on gold nanoparticles-coated magnetic Fe₃O₄ nanoparticles (Apt-GMNPs). Ethidium bromide (EB), intercalated into the stem of the aptamer hairpin, provides the read-out signal for the quantification of the leukemia cancer cells. After introduction of the leukemia cancer cells onto the Apt-GMNPs, the hairpin structure of the aptamer is disrupted and the intercalator molecules are released, resulting in a decrease of the electrochemical signal. The immobilization of nitrogen-doped graphene nanosheets on the electrode surface provides an excellent platform for amplifying the read-out signal. Under optimal conditions, the aptasensor exhibits a linear response over a wide dynamic range of leukemia cancer cells from 10 to 1×10⁶cellmL^-1. The present protocol provides a highly sensitive, selective, simple, and robust method for early stage detection of leukemia cancer. Furthermore, the fabricated aptasensor was successfully used for the detection of leukemia cancer cells in complex media such as human blood plasma, without any serious interference.

Highly sensitive detection of cancer cells with an electrochemical cytosensor based on boronic acid functional polythiophene

The detection of cancer cells through important molecular recognition target such as sialic acid is significant for the clinical diagnosis and treatment. There are many electrochemical cytosensors developed for cancer cells detection but most of them have complicated fabrication processes which results in poor reproducibility and reliability. In this study, a simple, low-cost, and highly sensitive electrochemical cytosensor was designed based on boronic acid-functionalized polythiophene. In cytosensors fabrication simple single-step procedure was used which includes coating pencil graphite electrode (PGE) by means of electro-polymerization of 3-Thienyl boronic acid and Thiophen. Electrochemical impedance spectroscopy and cyclic voltammetry were used as an analytical methods to optimize and measure analytical performances of PGE/P(TBA_0.5Th_0.5) based electrode. Cytosensor showed extremely good analytical performances in detection of cancer cells with linear rage of 1×10¹ to 1×10⁶ cellsmL^-1 exhibiting low detection limit of 10 cellsmL^-1 and incubation time of 10min. Next to excellent analytical performances, it showed high selectivity towards AGS cancer cells when compared to HEK 293 normal cells and bone marrow mesenchymal stem cells (BM-hMSCs). This method is promising for future applications in early stage cancer diagnosis.

Aptasensor based on fluorescence resonance energy transfer for the analysis of adenosine in urine samples of lung cancer patients

A new aptasensor was designed for the analysis of adenosine based on fluorescence resonance energy transfer (FRET) between CdS quantum dot (QDs) as a donor and polypyrrole (Ppy) as an acceptor. The QDs were covalently bonded to anti-adenosine aptamer where its fluorescence was quenched by Ppy. When Ppy was replaced by adenosine, the fluorescence of QDs was restored and its intensity was proportional to the adenosine concentration. Under the optimized conditions, a linear range was found to be 23-146 nM with a detection limit of 9.3 nM. The method was used for analysis of adenosine in urine samples of lung cancer patients and its accuracy was evaluated by comparison of the results of the proposed method with the standard method of HPLC-UV. Furthermore, the interactions of adenosine molecules with the aptamer were investigated using molecular modeling, including molecular dynamic simulations (MDS). The results demonstrated that each G-quadruplex aptamer can capture two adenosine molecules.

Multifunctional nanoreactor for comprehensive characterization of membrane proteins based on surface functionalized mesoporous foams

An integrated protocol is proposed here for efficient analysis of membrane proteins based on surface functionalized mesoporous graphene foams (MGF). The inherent hydrophobic nature of MGF and surface modification with hydrophilic chitosan (CS) make it highly suitable for the enrichment of hydrophobic membrane proteins from organic solvent, while remaining well-dispersed in aqueous solution for subsequent proteolysis. Therefore, such a multifunctional reactor ensures a facile solvent adjustment route. Furthermore, as a chitosan modified nanoporous reactor, it also provides a biocompatible nanoenvironment that can maintain the stability and activity of enzymes to realize efficient in situ digestion of the enriched membrane proteins. The concept was first proved with a standard hydrophobic membrane protein, bacteriorhodopsin, where a high number of identified peptides and amino acid sequence coverage were achieved even at extremely low protein concentration. The mesoporous reaction system was further applied to the analysis of complex real-case proteome samples, where 931 membrane proteins were identified in triplicate analyses by 2D LC-MS/MS. In contrast, with in-solution proteolysis, only 73 membrane proteins were identified from the same sample by the same 2D LC-MS/MS. The identified membrane proteins by the MGF-CS protocol include many biomarkers of the cell line. These results suggest that the multifunctional MGF-CS protocol is of great value to facilitate the comprehensive characterization of membrane proteins in the proteome research.

Construction of carbon nanotube based nanoarchitectures for selective impedimetric detection of cancer cells in whole blood

A carbon nanotube (CNT) based nanoarchitecture is developed for rapid, sensitive and specific detection of cancer cells by using real time electrical impedance sensing. The sensor is constructed with carbon nanotube (CNT) multilayers and EpCAM (epithelial cell adhesion molecule) antibodies, which are assembled on an indium tin oxide (ITO) electrode surface. The binding of tumor cells to EpCAM antibodies causes increase of the electron-transfer resistance. The electrochemical impedance of the prepared biosensors is linear with the logarithm of concentration of the liver cancer cell line (HepG2) within the concentration range of 10 to 10(5) cells per mL. The detection limit for HepG2 cells is 5 cells per mL. The proposed impedimetric sensing devices allow for sensitive and specific detection of cancer cells in whole-blood samples without any sample pretreatment steps.

Micro-competition system for Raman quantification of multiple glycans on intact cell surface

A micro-competition system integrated functionalized silica bubbles and Raman encoded nanoprobes to simultaneously assay multiple glycans on intact cell surfaces.

A micro-competition system is designed for simultaneous quantification of multiple glycans on intact cell surfaces, by integrating two-surface–one-molecule competition with surface enhanced Raman scattering (SERS). The micro-competition is achieved among multiple-polysaccharide-coated gold nanostars functionalized silica bubbles, target cells and gold nanoprobes at a micron scale. The gold nanoprobes are prepared by coating distinct Raman molecules and lectins on gold nanoparticles for signal resolution and glycan recognition, respectively. The silica bubble surface serves as an artificial glycan surface and a SERS substrate. Upon the competitive recognition of lectin to the corresponding glycan, the gold nanoprobes can be specifically captured by the bubbles and cells in a homogeneous system, and the amounts of different gold nanoprobes on bubbles are simultaneously detected by SERS to reflect the corresponding glycan amounts on the cell surface. This micro-competition system with multiple quantification capability provides a powerful tool for investigation of the complex glycan-related biological processes.

Synthesis of magnetic Fe3O4–Au hybrids for sensitive SERS detection of cancer cells at low abundance

A facile and rapid SERS-based immunoassay for living cancer cells using magnetic Fe₃O₄–Au hybrid nanoparticles is reported.

Ultra-sensitive detection of leukemia by graphene

Graphene oxide nanoplatelets (GONPs) with extremely sharp edges (lateral dimensions ∼ 20-200 nm and thicknesses <2 nm) were applied in extraction of the overexpressed guanine synthesized in the cytoplasm of leukemia cells. The blood serums containing the extracted guanine were used in differential pulse voltammetry (DPV) with reduced graphene oxide nanowall (rGONW) electrodes to develop fast and ultra-sensitive electrochemical detection of leukemia cells at leukemia fractions (LFs) of ∼ 10(-11) (as the lower detection limit). The stability of the DPV signals obtained by oxidation of the extracted guanine on the rGONWs was studied after 20 cycles. Without the guanine extraction, the DPV peaks relating to guanine oxidation of normal and abnormal cells overlapped at LFs <10(-9), and consequently, the performance of rGONWs alone was limited at this level. As a benchmark, the DPV using glassy carbon electrodes was able to detect only LFs ∼ 10(-2). The ultra-sensitivity obtained by this combination method (guanine extraction by GONPs and then guanine oxidation by rGONWs) is five orders of magnitude better than the sensitivity of the best current technologies (e.g., specific mutations by polymerase chain reaction) which not only are expensive, but also require a few days for diagnosis.

Mechanism of DNA adsorption and desorption on graphene oxide

Graphene oxide (GO) adsorbing a fluorophore-labeled single-stranded (ss) DNA serves as a sensor system because subsequent desorption of the adsorbed probe DNA from GO in the presence of complementary target DNA enhances the fluorescence. In this study, we investigated the interaction of single- and double-stranded (ds) DNAs with GO by using a fluorescently labeled DNA probe. Although GO is known to preferentially interact with ssDNA, we found that dsDNA can also be adsorbed on GO, albeit with lower affinity. Furthermore, the status of ssDNA or dsDNA previously adsorbed on the GO surface was investigated by adding complementary or noncomplementary DNA (cDNA or non-cDNA) to the adsorption complex. We observed that hybridization occurred between the cDNA and the probe DNA on the GO surface. On the basis of the kinetics driven by the incoming additional DNA, we propose a mechanism for the desorption of the preadsorbed probe DNA from the GO surface: the desorption of the GO-adsorbed DNA was facilitated following its hybridization with cDNA on the GO surface; when the GO surface was almost saturated with the adsorbed DNA, nonspecific desorption dominated the process through a simple displacement of the GO-adsorbed DNA molecules by the incoming DNA molecules because of the law of mass action. Our results can be applied to design appropriate DNA probes and to choose proper GO concentrations for experimental setups to improve specific signaling in many biosensor systems based on the GO platform.

Interactions of DNA with graphene and sensing applications of graphene field-effect transistor devices: a review

Graphene field-effect transistors (GFET) have emerged as powerful detection platforms enabled by the advent of chemical vapor deposition (CVD) production of the unique atomically thin 2D material on a large scale. DNA aptamers, short target-specific oligonucleotides, are excellent sensor moieties for GFETs due to their strong affinity to graphene, relatively short chain-length, selectivity, and a high degree of analyte variability. However, the interaction between DNA and graphene is not fully understood, leading to questions about the structure of surface-bound DNA, including the morphology of DNA nanostructures and the nature of the electronic response seen from analyte binding. This review critically evaluates recent insights into the nature of the DNA graphene interaction and its affect on sensor viability for DNA, small molecules, and proteins with respect to previously established sensing methods. We first discuss the sorption of DNA to graphene to introduce the interactions and forces acting in DNA based GFET devices and how these forces can potentially affect the performance of increasingly popular DNA aptamers and even future DNA nanostructures as sensor substrates. Next, we discuss the novel use of GFETs to detect DNA and the underlying electronic phenomena that are typically used as benchmarks for characterizing the analyte response of these devices. Finally, we address the use of DNA aptamers to increase the selectivity of GFET sensors for small molecules and proteins and compare them with other, state of the art, detection methods.

Paper-based electrochemiluminescence origami cyto-device for multiple cancer cells detection using porous AuPd alloy as catalytically promoted nanolabels

The detection of cancer cells is important and fundamental for cancer diagnosis and therapy, which has attracted considerable interest recently. Although traditional cyto-sensors have been widely explored due to their high sensitivity and selectivity, it is still a challenge to develop a low-cost, portable, disposable, fast, and easy-to-use cancer cell detection method for applying in the field of cancer diagnosis and therapy. Herein, to address these challenges, we developed a microfluidic paper-based electrochemiluminescence origami cyto-device (μ-PECLOC), in which aptamers modified 3D macroporous Au-paper electrodes were employed as the working electrodes and efficient platforms for the specific cancer cells capture. Owing to the effective disproportionation of hydrogen peroxide and specific recognition of mannose on cell surface, concanavalin-A conjugated porous AuPd alloy nanoparticles were introduced into this μ-PECLOC as the catalytically promoted nanolabels for peroxydisulfate ECL system. Under the optimal conditions, the proposed μ-PECLOC exhibited excellent analytical performance with good stability, reproducibility, and accuracy, towards the cyto-sensing of four types of cancer cells indicating the potential applications to facilitate effective and multiple early cancer diagnosis and clinical treatment.