Fufeng Yan

DNA Immobilization/Hybridization on Plasma-Polymerized Pyrrole

The present work describes the fabrication and characterization of the conducting polymer coatings prepared by the continuous wave plasma polymerization and the applications as adhesion layers for studying DNA immobilization/hybridization. The stability of plasma polymerized pyrrole (ppPY) in the aqueous solution was characterized by ellipsometry. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy were used to investigate polymer matrix properties and oligonucleotide/DNA binding interaction. The successful DNA immobilization on ppPY surfaces was found to depend on the macromolecular architecture of plasma polymerized films. The plasma polymers with similar thickness deposited at different input powers showed various comparable immobilization properties. The plasma-polymerized films prepared at the low input power showed a lower sensitivity toward DNA binding than those films deposited at the high input power. This result will be important to study plasma polymerized films as potential DNA biosensors in the future.

Label-free aptamer biosensor for thrombin detection on a nanocomposite of graphene and plasma polymerized allylamine

A label-free and effective aptasensor based on an amino-functionalized nanocomposite of graphene and plasma-polymerized allylamine (G-PPAA) was developed for thrombin detection. Graphene was assembled on the substrate, followed by the self-assembly of octadecylamine (OTA) to protect the graphene from etching by subsequent plasma irradiation. Afterward, PPAA was deposited onto the graphene surface with the self-assembled OTA, and the nanocomposite with amino groups was fabricated. The label-free thrombin aptamer was immobilized onto the amino-functionalized nanocomposite matrix via electrostatic interaction between the phosphate groups of the aptamer and the amino groups in PPAA. The process was investigated using impedimetric detection and a quartz crystal microbalance (QCM). The chemical compositions, surface morphology, and electrochemical properties were found to be dependent on the plasma conditions used in the polymer deposition. The amounts and kinetics of aptamer immobilization and thrombin detection were determined using QCM measurements. A relatively high affinity constant of aptamer immobilization and low detection limit for thrombin were achieved by using the G-PPAA film as the biosensor matrix. Results suggest that G-PPAA films can be applied in gene therapy and protein detection.

One-step synthesis of porous cuprous oxide microspheres on reduced graphene oxide for selective detection of mercury ions

In this paper, we report on the facile one-step synthesis of porous cuprous oxide microspheres on reduced graphene oxide (Cu2OMS–rGO) by synchronously reducing Cu2+ ions and GO with ascorbic acid sodium, followed by their application as electrochemical biosensors for the detection of mercury ions in water. After detailed characterization of the basic chemical components, crystal structure, surface morphology, and electrochemical properties of the Cu2OMS–rGO composites, single-stranded and thymine (T)-rich oligonucleotides were successively immobilized onto the surface of the composite electrode modified by Cu2OMS–rGO. Upon introduction of the target analyte, Hg2+ ions were intercalated into the DNA polyion complex membrane based on T–Hg2+–T coordination chemistry. The results show that the Cu2OMS–rGO composite has high sensitivity for the detection of Hg2+, with a detection limit of 8.62 pM within the range of 0.05 nM to 40 nM. Therefore, the Cu2OMS–rGO composite could be utilized as a novel biosensor for the detection of heavy metal ions in water or in the environment. The strategy yielded excellent selectivity of Hg2+ against other interfering metal ions. In addition, the developed DNA sensor for the determination of Hg2+ ions could be reproduced up to 10 cycles, and the recovery was approximately 95%.

An electrochemical sensor based on rhodamine B hydrazide-immobilized graphene oxide for highly sensitive and selective detection of Cu(II)

A novel strategy for fabricating a Cu2+ sensor based on rhodamine B hydrazide (RBH)-immobilized graphene oxide (GO) was reported. The thiol-modified Au electrode was functionalized by carboxyl functionalized GO through intermolecular interactions, followed by chemical bonding with RBH. The developed nanocomposite was used as an electrochemical sensor for detecting Cu2+ in aqueous solution using electrochemical impedance spectroscopy analysis with a detection limit of 0.061 nM within the range from 0.1 to 50 nM. Furthermore, the interference from potentially interfering ions such as Hg2+, Ag+, Cr2+, Fe2+, Pb2+, Ba2+, Mn2+, Co2+, and Ni2+ associated with Cu2+ analysis could be effectively inhibited. In addition, the developed Cu2+ sensor could be reproduced up to 10 cycles. In this approach, the fluorescent probe RBH can be replaced by other fluorescein derivatives which could identify the corresponding ions, which makes the approach a widely applicable strategy for metal ion detection.

Feasible electrochemical biosensor based on plasma polymerization-assisted composite of polyacrylic acid and hollow TiO2 spheres for sensitively detecting lysozyme

A composite made of polyacrylic acid and hollow TiO2 spheres (TiO2@PPAA) was prepared by the plasma polymerization method and subsequently used as an electrode material for detecting lysozyme. The chemical structure, surface morphology, and electrochemical performance of the TiO2@PPAA composite were mainly affected by the plasma input power used during plasma polymerization. After optimizing plasma conditions, aptamer strands exhibited high adsorption affinity toward the surface of TiO2@PPAA composite via synergistic effects between TiO2 and PPAA. Electrochemical impedance spectroscopy results showed that the developed TiO2@PPAA aptasensor presents highly sensitive detection ability toward lysozyme; the limit of detection of the proposed aptasensor is 0.015 ng mL(-1) (1.04 pM) within the range of 0.05-100 ng mL(-1) in terms of 3σ value. The film further showed excellent selectivity toward lysozyme in the presence of interfering proteins, such as thrombin, bovine serum albumin, and immunoglobulin E. Thus, this aptasensing strategy might broaden the applications of plasma polymerized nanomaterials in the field of biomedical research and early clinical diagnosis.

Protein-templated cobaltous phosphate nanocomposites for the highly sensitive and selective detection of platelet-derived growth factor-BB.

We synthesized novel Co3(PO4)2-based nanocomposites with 3D porous architectures via self-assembly; here, bovine serum albumin (BSA) and aptamer were used as organic phases to produce Co3(PO4)2@BSA and Co3(PO4)2@Apt nanocomposites, respectively. The formation mechanism of Co3(PO4)2-based nanocomposites was described based on characterizations of their physio-chemical performance, and the developed nanocomposites were applied as scaffold materials to construct a novel electrochemical aptasensor and detect platelet-derived growth factor-BB (PDGF-BB). The PDGF-BB targeting aptamer must be immobilized onto the Co3(PO4)2@BSA-modified electrode to detect PDGF-BB, whereas Co3(PO4)2@Apt-based aptasensor may be directly used to determine the target protein. Electrochemical impedance spectroscopy results showed that the developed Co3(PO4)2@BSA- and Co3(PO4)2@Apt-based aptasensors present highly sensitive detection ability toward PDGF-BB. Due to the special nanoflower structure, the Co3(PO4)2@BSA-based aptasensor features a detection limit of 3.7 pg mL(-1); while the limit of detection of the Co3(PO4)2@Apt-based aptasensor is 61.5 pg mL(-1), which is the possible bioactivity loss of the aptamer in Co3(PO4)2@Apt nanocomposite. The two detection limits obtained are still much lower than or comparable with those of previously reported aptasensors. The Co3(PO4)2@BSA- and Co3(PO4)2@Apt-based aptasensors showed high selectivity, stability, and applicability for detecting the desired protein. This finding indicates that the Co3(PO4)2-based nanocomposites could be used as an electrochemical biosensor for various detection procedures in the biomedical field.

Graphene nanostructures with plasma-polymerized pyrrole as an adsorbent layer for biosensors

AbstractWe report on a novel nanoarchitecture for use in highly bioactive electrochemical biosensors. It consists of multilayers of nanostructured plasma-polymerized pyrrole (ppPY) and nanosheets of electrically conductive graphene. The ppPY films were deposited by plasma-enhanced chemical vapor deposition on a graphene surface to form nanostructured composites (G-ppPY). The G-ppPY films were then coated with protein (BSA as a model) by adsorption, and then with DNA. The adsorption of protein and DNA on the nanocomposite was studied by electrochemical impedance spectroscopy and with a quartz crystal microbalance. Results demonstrated that the adsorption of biomolecules on G-ppPY films causes a higher variation in its electrochemical properties and adsorbed amount than that on a plain ppPY surface. This indicates that the presence of graphene can enhance the electrochemical activity of ppPY without reducing the sensitivity of biomolecular adsorption. FigureA novel nanoarchitecture is developed for use in highly bioactive electrochemical biosensors, which is composed of multilayers of nanostructured plasma-polymerized pyrrole and electrically conductive graphene nanosheets. The presence of graphene can enhance the electrochemical activity of ppPY without reducing the sensitivity of biomolecular adsorption.

Protein adsorption materials of the soluble conducting polymer poly(acryloyl chloride)-g-polypyrrole

In order to fabricate a soluble conducting polypyrrole matrix, applied as a biomaterial to anchor proteins, the preparation of a poly(acryoyl pyrrole)-g-polypyrrole (PAP-g-PPy) copolymer and the adsorption of bovine serum albumin (BSA) onto this conducting copolymer were studied. Polypyrrole (PPy) was synthesized by electrochemical polymerization on an Au surface, which had been spin-coated with a poly(acryloyl chloride) precursor containing a pyrrole moiety in its side chain. The chemical properties of PPy depend on the polymerization conditions, i.e., the concentration of pyrrole and the polymerization time. Subsequently, the adsorption behavior of BSA on PAP-g-PPy was investigated by surface plasmon resonance spectroscopy, suggesting that the copolymer thickness, the concentration of pyrrole monomer used in the preparation of the polymer, the BSA concentration and the pH value of buffer solutions can affect the adsorption behavior of BSA onto the polymer surface. It is therefore predicted that the conducting copolymer PAP-g-PPy could be used as an adsorbed matrix for protein adsorption.

Towards understanding of protein adsorption behavior on plasma polymerized pyrrole film

AbstractPlasma polymerized pyrrole-like (PPpy) films exhibit good environmental stability and offer high reactivity with biomolecules. The present paper follows on from previous work on PPpy films applied as DNA immobilization/hybridization and describes the adsorption kinetics of bovine serum albumin (BSA) on PPpy films. Atom force microscopy was used to detect the surface roughness of PPpy surfaces obtained at different input powers or for different polymerization time, including the surface roughness before and after BSA adsorption. The influence of experimental conditions (i.e., the plasma input power, the polymerization time, the concentration of BSA, and the pH values of buffer solutions) on protein adsorption was investigated in situ by Surface plasmon resonance spectroscopy (SPR). SPR analysis confirmed the differently dynamic adsorption behavior of BSA on PPpy films under various experimental conditions. The adsorption constant, Ka, was deduced from Langmuir isotherm equations, which were simulated using experimental data collected by SPR and electrochemical impedance spectroscopy (EIS). Analysis of the combination data of SPR and EIS indicates that PPpy films under various conditions show completely different adsorption behaviors and could be applied as biomaterials for electrochemical protein sensing or as protein-resistant.