9 research outputs found
A review on electronic bio-sensing approaches based on non-antibody recognition elements
In this review, recent advances in the development of electronic detection methodologies based on non-antibody recognition elements such as functional liposomes, aptamers and synthetic peptides are discussed. Particularly, we highlight the progress of field effect transistor (FET) sensing platforms where possible as the number of publications on FET-based platforms has increased rapidly. Biosensors involving antibody-antigen interactions have been widely applied in diagnostics and healthcare in virtue of their superior selectivity and sensitivity, which can be attributed to their high binding affinity and extraordinary specificity, respectively. However, antibodies typically suffer from fragile and complicated functional structures, large molecular size and sophisticated preparation approaches (resource-intensive and time-consuming), resulting in limitations such as short shelf-life, insufficient stability and poor reproducibility. Recently, bio-sensing approaches based on synthetic elements have been intensively explored. In contrast to existing reports, this review provides a comprehensive overview of recent advances in the development of biosensors utilizing synthetic recognition elements and a detailed comparison of their assay performances. Therefore, this review would serve as a good summary of the efforts for the development of electronic bio-sensing approaches involving synthetic recognition elements
Detection of matrilysin (MMP-7) activity using polypeptide functionalized reduced graphene oxide field-effect transistor sensor.
A novel approach for rapid and sensitive detection of matrilysin (MMP-7, a biomarker involved in the degradation of vari-ous macromolecules) based on polypeptide (JR2EC) functionalized reduced graphene oxide (rGO) field effect transistor (FET) is reported. MMP-7 specifically digests negatively charged JR2EC immobilized on rGO, thereby modulating the con-ductance of rGO-FET. The proposed assay enabled detection of MMP-7 at clinically relevant concentrations with a limit of detection (LOD) of 10 ng/mL (400 pM), attributed to the significant reduction of the net charge of JR2EC upon digestion by MMP-7. Quantitative detection of MMP-7 in human plasma was further demonstrated with a LOD of 40 ng/mL, illustrating the potential for the proposed methodology for tumor detection and carcinoma diagnostic (e.g. lung cancer and salivary gland cancer). Additionally, excellent specificity of the proposed assay was demonstrated using matrix metallopeptidase 1 (MMP-1), a protease of the same family. With appropriate selection and modification of polypeptides, the proposed assay could be extended for detections of other enzymes with polypeptide digestion capability
Luminescent Device for the Detection of Oxidative Stress Biomarkers in Artificial Urine
A luminescent paper-based
device for the visual detection of oxidative stress biomarkers is
reported. The device consists of a polyvinylidene fluoride membrane
impregnated with poly(3-alkoxy-4-methylthiophene) (PT) for colorimetric
detection. 8-hydroxy-2′-deoxyguanosine (8-OHdG), a biomarker
associated with oxidative stress, is used as a model system for validating
the proposed methodology. The detection strategy is based on monitoring
the changes in optical properties of PT associated with its conformational
changes upon interaction with an aptamer in the presence and in the
absence of 8-OHdG. Fluorometric and colorimetric monitoring revealed
linear responses for 8-OHdG concentrations between 50 pM and 500 nM
(∼14 pg/mL to 140 ng/mL), with limits of detection of ∼300
pM and ∼350 pM, respectively for (<i>n</i> = 3). Colorimetric responses in artificial urine ascertained rapid,
sensitive, and selective detection of 8-OHdG at clinically relevant
(pM to nM) concentration levels. Furthermore, the proposed methodology
enables point-of-care diagnostics for oxidative stress without requiring
sophisticated instrumentation
Tailoring Conformation-Induced Chromism of Polythiophene Copolymers for Nucleic Acid Assay at Resource Limited Settings
Here we report on the design and
synthesis of cationic water-soluble
thiophene copolymers as reporters for colorimetric detection of microRNA
(miRNA) in human plasma. Poly(3-alkoxythiophene) (PT) polyelectrolytes
with controlled ratios of pendant groups such as triethylamine/1-methyl
imidazole were synthesized for optimizing interaction with target
miRNA sequence (Tseq). Incorporation of specific peptide nucleic acid
(PNA) sequences with the cationic polythiophenes yielded distinguishable
responses upon formation of fluorescent PT–PNA–Tseq
triplex and weakly fluorescent PT–Tseq duplex, thereby enabling
selective detection of target miRNA. Unlike homopolymers of PT (hPT),
experimental results indicate the possibility of utilizing copolymers
of PT (cPT) with appropriate ratios of pendant groups for miRNA assay
in complex matrices such as plasma. As an illustration, colorimetric
responses were obtained for lung cancer associated miRNA sequence
(mir21) in human plasma, with a detection limit of 10 nM, illustrating
the feasibility of proposed methodology for clinical applications
without involving sophisticated instrumentation. The described methodology
therefore possesses high potential for low-cost nucleic acid assays
in resource-limited settings
Peptide Functionalized Gold Nanoparticles with Optimized Particle Size and Concentration for Colorimetric Assay Development: Detection of Cardiac Troponin I
Peptide-functionalized
gold nanoparticles (AuNPs) are extensively
utilized in colorimetric assays for rapid and sensitive detection
of various biomedical and environmental targets. Although extensively
used as colorimetric reporting systems, the role of the size and concentration
of the AuNPs has not been thoroughly investigated. In this study,
a 12-mer cardiac troponin I (cTnI)-specific peptide CALNN-Peg<sub>4</sub>-FYSHSFHENWPS was immobilized on AuNPs of
different size and concentration via the CALNN anchoring sequence.
A relationship was established between the total surface area of the
AuNPs (binding availability) and response (centroid shift). Moreover,
a colorimetric assay for cTnI operating under optimized conditions
(36 nm AuNPs) yielded a limit of detection of 0.2 ng/mL (8.4 pM) when
tested in diluted serum samples with an assay time of 10 min. This
encouraging result opens up for further development of AuNP assays
in early diagnosis of cardiac injury
Label-free electronic detection of interleukin-6 using horizontally aligned carbon nanotubes
A facile, sensitive, and label-free assay for detection of interleukin-6 (IL-6) using liquid-gated field-effect transistor (FET) sensors based on horizontally aligned single-walled carbon nanotubes (SWCNT) is proposed. This approach relies on the drain current (Id) responses of the transistor upon interactions of IL-6 with its corresponding antibody (IL-6R) immobilized on SWCNT. The proposed immunosensor exhibits superior sensitivity (limit-of-detection = 1.37 pg/mL) in virtue of the reduced tube-to-tube contact resistance, good selectivity (no responses to bovine serum albumin and cysteine were observed and detection of target molecules in serum was achieved) as a result of the highly specific interaction between IL-6 and IL-6R, and excellent stability (no significant degradation in the electronic performance after storage under ambient conditions for up to 3 months) in virtue of the strong adhesion of CNT to the quartz substrate and good horizontal alignment of these tubes. Therefore, the proposed immunosensor is a promising platform for early diagnosis of various diseases (including some cancers) that can be indicated by the circulating level of IL-6
Hand-Held Volatilome Analyzer Based on Elastically Deformable Nanofibers
This
study reports on a hand-held volatilome analyzer for selective
determination of clinically relevant biomarkers in exhaled breath.
The sensing platform is based on electrospun polymer nanofiber-multiwalled
carbon nanotube (MWCNT) sensing microchannels. Polymer nanofibers
of poly(vinylidene fluoride) (PVDF), polystyrene (PS), and poly(methyl
methacrylate) (PMMA) incorporated with MWCNT exhibits a stable response
to interferences of humidity and CO<sub>2</sub> and provides selective
deformations upon exposure of exhaled breath target volatilomes acetone
and toluene, exhibiting correlation to diabetes and lung cancer, respectively.
The sensing microchannels “P1” (PVDF-MWCNT), “P2”
(PS-MWCNT), and “P3” (PMMA-MWCNT) are integrated with
a microfluidic cartridge (μ-card) that facilitates collection
and concentration of exhaled breath. The volatilome analyzer consists
of a conductivity monitoring unit, signal conditioning circuitries
and a low energy display module. A combinatorial operation algorithm
was developed for analyzing normalized resistivity changes of the
sensing microchannels upon exposure to breath in the concentration
ranges between 35 ppb and 3.0 ppm for acetone and 1 ppb and 10 ppm
for toluene. Subsequently, responses of volatilomes from individuals
in the different risk groups of diabetes were evaluated for validation
of the proposed methodology. We foresee that proposed methodology
provides an avenue for rapid detection of volatilomes thereby enabling
point of care diagnosis in high-risk group individuals
Detection of Matrilysin Activity Using Polypeptide Functionalized Reduced Graphene Oxide Field-Effect Transistor Sensor
A novel
approach for rapid and sensitive detection of matrilysin (MMP-7, a
biomarker involved in the degradation of various macromolecules) based
on a polypeptide (JR2EC) functionalized reduced graphene oxide (rGO)
field effect transistor (FET) is reported. MMP-7 specifically digests
negatively charged JR2EC immobilized on rGO, thereby modulating the
conductance of rGO-FET. The proposed assay enabled detection of MMP-7
at clinically relevant concentrations with a limit of detection (LOD)
of 10 ng/mL (400 pM), attributed to the significant reduction of the
net charge of JR2EC upon digestion by MMP-7. Quantitative detection
of MMP-7 in human plasma was further demonstrated with a LOD of 40
ng/mL, illustrating the potential for the proposed methodology for
tumor detection and carcinoma diagnostic (e.g., lung cancer and salivary
gland cancer). Additionally, excellent specificity of the proposed
assay was demonstrated using matrix metallopeptidase 1 (MMP-1), a
protease of the same family. With appropriate selection and modification
of polypeptides, the proposed assay could be extended for detection
of other enzymes with polypeptide digestion capability
Functionalization of the Polymeric Surface with Bioceramic Nanoparticles via a Novel, Nonthermal Dip Coating Method
The only nonthermal method of depositing
a bioceramic-based coating on polymeric substrates
is by incubation in liquid, e.g., simulated body fluid to form an
apatite-like layer. The drawbacks of this method include the long
processing time, the production of low scratch resistant coating,
and an end product that does not resemble the intended bioceramic
composition. Techniques, such as plasma spraying and magnetron sputtering,
involving high processing temperature are unsuitable for polymers,
e.g., PMMA. Here, we introduce a nonthermal coating method to immobilize
hydroxyapatite (HAp) and TiO<sub>2</sub> nanoparticles on PMMA via
a simple and fast dip coating method.
Cavities that formed on the PMMA, induced by chloroform, appeared
to trap the nanoparticles which accumulated to form layers of bioceramic
coating only after 60 s. The resulting coating was hydrophilic and
highly resistant to delamination.
In the context of our research and to address the current clinical
need, we demonstrate that the HAp-coated PMMA, which is intended to
be used as a visual optic of a corneal prosthetic device, improves
its bonding and biointegration with collagen, the main component of
a corneal stroma. The HAp-coated PMMA resulted in better adhesion
with the collagen than untreated PMMA in artificial tear fluid over
28 days. Human corneal stromal fibroblasts showed better attachment,
viability, and proliferation rate on the HAp-coated PMMA than on untreated
PMMA. This coating method is an innovative solution to immobilize
various bioceramic nanoparticles on polymers and may be used in other
biomedical implants