4 research outputs found
Ultrasensitive Photoelectrochemical Biosensing of Multiple Biomarkers on a Single Electrode by a Light Addressing Strategy
Ultrasensitive
multiplexed detection of biomarkers on a single
electrode is usually a great challenge for electrochemical sensors.
Here, a light addressable photoelectrochemical sensor (LAPECS) for
the sensitive detection of multiple DNA biomarkers on a single electrode
was reported. The sensor was constructed through four steps: (1) immobilization
of capture DNA (C-DNA) of different targets on different areas of
a single large-sized gold film electrode, (2) recognition of each
target DNA (T-DNA) and the corresponding biotin-labeled probe DNA
(P-DNA) through hybridization, (3) reaction of the biotin-labeled
probe DNA with a streptavidin-labeled all-carbon PEC bioprobe, and
(4) PEC detection of multiple DNA targets one by one via a light addressing
strategy. Through this principle, the LAPECS can achieve ultrasensitive
detection of three DNA sequences related to hepatitis B (HBV), hepatitis
C (HCV) and human immunodeficiency (HIV) viruses with a similar wide
calibration range of 1.0 pM ∼ 0.01 μM and a low detection
limit of 0.7 pM by using one kind of PEC bioprobe. Moreover, the detection
throughput of LAPECS may be conveniently expanded by simply enlarging
the size of the substrate electrode or reducing the size of the sensing
arrays and the light beam. The present work thus demonstrates the
promising applications of LAPECS in developing portable, sensitive,
high-throughput, and cost-effective biosensing systems
Inkjet Printing of Nanoporous Gold Electrode Arrays on Cellulose Membranes for High-Sensitive Paper-Like Electrochemical Oxygen Sensors Using Ionic Liquid Electrolytes
A simple approach to the mass production of nanoporous
gold electrode
arrays on cellulose membranes for electrochemical sensing of oxygen
using ionic liquid (IL) electrolytes was established. The approach,
combining the inkjet printing of gold nanoparticle (GNP) patterns
with the self-catalytic growth of these patterns into conducting layers,
can fabricate hundreds of self-designed gold arrays on cellulose membranes
within several hours using an inexpensive inkjet printer. The resulting
paper-based gold electrode arrays (PGEAs) had several unique properties
as thin-film sensor platforms, including good conductivity, excellent
flexibility, high integration, and low cost. The porous nature of
PGEAs also allowed the addition of electrolytes from the back cellulose
membrane side and controllably produced large three-phase electrolyte/electrode/gas
interfaces at the front electrode side. A novel paper-based solid-state
electrochemical oxygen (O<sub>2</sub>) sensor was therefore developed
using an IL electrolyte, 1-butyl-3-methylimidazolium hexafluorophosphate
(BMIMPF<sub>6</sub>). The sensor looked like a piece of paper but
possessed high sensitivity for O<sub>2</sub> in a linear range from
0.054 to 0.177 v/v %, along with a low detection limit of 0.0075%
and a short response time of less than 10 s, foreseeing its promising
applications in developing cost-effective and environment-friendly
paper-based electrochemical gas sensors
Ultrasensitive All-Carbon Photoelectrochemical Bioprobes for Zeptomole Immunosensing of Tumor Markers by an Inexpensive Visible Laser Light
A novel
enzyme-free and all-carbon photoelectrochemical (PEC) bioprobe,
based on carboxylated multiwalled carbon nanotube–Congo red–fullerene
nanohybrids (MWNTCOOH–CR–C<sub>60</sub>), for the ultrasensitive
immunosensing of carcinoembryonic antigen (CEA) was reported. The
MWNTCOOH–CR–C<sub>60</sub> nanohybrids, prepared by
mechanically grinding a mixture of MWNTCOOH, C<sub>60</sub>, and CR
at a certain mass ratio, had good water dispersibility and high PEC
conversion efficiency in visible light ranges. Covalent binding of
the detection antibody of CEA on the MWNTCOOH–CR–C<sub>60</sub> nanohybrids produced a sensitive PEC bioprobe for detection
of CEA by sandwich immunosensing. The corresponding immunosensor,
employing an inexpensive and portable green laser light, possessed
a wide calibration range of 1.0 pg/mL∼100.0 ng/mL and a low
detection limit of 0.1 pg/mL (calculated 5 zmol for a 10.0 μL
sample solution) (S/N = 3), which was successfully applied to the
detection of CEA in serum samples from both healthy people and cancer
patients. The present work thus demonstrated the promising application
of fullerene-based nanocomposites in developing highly sensitive,
environmentally friendly, and cost-effective PEC biosensors
Fully Converting Graphite into Graphene Oxide Hydrogels by Preoxidation with Impure Manganese Dioxide
Potassium
permanganate (KMnO<sub>4</sub>) has been proved to be an efficient
oxidant for converting graphite into graphite oxide, but its slow
diffusion in the interlayer of graphite seriously restricts the production
of graphene oxide (GO). Here, we demonstrate that the preoxidation
of graphite by impure manganese dioxide (MnO<sub>2</sub>) in a mixture
of concentrated sulfuric acid (H<sub>2</sub>SO<sub>4</sub>) and phosphorus
pentoxide (P<sub>2</sub>O<sub>5</sub>) can efficiently improve the
synthesis of GO when KMnO<sub>4</sub> is employed as the oxidant.
The prepared honey-like GO hydrogels possess a high yield of single-layer
sheets, large sizes (average lateral size up to 20 μm), wide
ranges of stable dispersion concentrations (from dilute solutions,
viscous hydrogels, to dry films), and good conductivity after reduction
(∼2.9 × 10<sup>4</sup> S/m). The mechanism for the improved
synthesis of GO by impure MnO<sub>2</sub> was explored. The enhanced
exfoliation and oxidation of graphite by oxidative Mn ions (mainly
Mn<sup>3+</sup>), which are synergistically produced by the reaction
of impure MnO<sub>2</sub> with H<sub>2</sub>SO<sub>4</sub> and P<sub>2</sub>O<sub>5</sub>, are found to be responsible for the improved
synthesis of such GO hydrogels. Particularly, preoxidized graphite
(POG) can be partially dispersed in water with sonication, which allows
the facile construction of flexible and highly conductive graphene
nanosheet film electrodes with excellent electrochemical sensing properties