24 research outputs found
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
Tuning Liposome Membrane Permeability by Competitive Coiled Coil Heterodimerization and Heterodimer Exchange
Membrane-active
peptides that enable the triggered release of liposomal
cargo are of great interest for the development of liposome-based
drug delivery systems but require peptide–lipid membrane interactions
that are highly defined and tunable. To this end, we have explored
the possibility to use the competing interactions between membrane
partitioning and heterodimerization and the folding of a set of four
different de novo designed coiled coil peptides. Covalent conjugation
of the cationic peptides triggered rapid destabilization of membrane
integrity and the release of encapsulated species. The release was
inhibited when introducing complementary peptides as a result of heterodimerization
and folding into coiled coils. The degree of inhibition was shown
to be dictated by the coiled coil peptide heterodimer dissociation
constants, and liposomal release could be reactivated by a heterodimer
exchange to render the membrane bound peptide free and thus membrane-active.
The possibility to tune the permeability of lipid membranes using
highly specific peptide-folding-dependent interactions delineates
a new possible approach for the further development of responsive
liposome-based drug delivery systems
Peptide Functionalized Gold Nanoparticles as a Stimuli Responsive Contrast Medium in Multiphoton Microscopy
There
is a need for biochemical contrast mediators with high signal-to-noise
ratios enabling noninvasive biomedical sensing, for example, for neural
sensing and protein–protein interactions, in addition to cancer
diagnostics. The translational challenge is to develop a biocompatible
approach ensuring high biochemical contrast while avoiding a raise
of the background signal. We here present a concept where gold nanoparticles
(AuNPs) can be utilized as a stimuli responsive contrast medium by
chemically triggering their ability to exhibit multiphoton-induced
luminescence (MIL) when performing multiphoton laser scanning microscopy
(MPM). Proof-of-principle is demonstrated using peptide-functionalized
AuNPs sensitive to zinc ions (Zn<sup>2+</sup>). Dispersed particles
are invisible in the MPM until addition of millimolar concentrations
of Zn<sup>2+</sup> upon which MIL is enabled through particle aggregation
caused by specific peptide interactions and folding. The process can
be reversed by removal of the Zn<sup>2+</sup> using a chelator, thereby
resuspending the AuNPs. In addition, the concept was demonstrated
by exposing the particles to matrix metalloproteinase-7 (MMP-7) causing
peptide digestion resulting in AuNP aggregation, significantly elevating
the MIL signal from the background. The approach is based on the principle
that aggregation shifts the plasmon resonance, elevating the absorption
cross section in the near-infrared wavelength region enabling onset
of MIL. This Letter demonstrates how biochemical sensing can be obtained
in far-field MPM and should be further exploited as a future tool
for noninvasive optical biosensing
Peptide Functionalized Gold Nanoparticles as a Stimuli Responsive Contrast Medium in Multiphoton Microscopy
There
is a need for biochemical contrast mediators with high signal-to-noise
ratios enabling noninvasive biomedical sensing, for example, for neural
sensing and protein–protein interactions, in addition to cancer
diagnostics. The translational challenge is to develop a biocompatible
approach ensuring high biochemical contrast while avoiding a raise
of the background signal. We here present a concept where gold nanoparticles
(AuNPs) can be utilized as a stimuli responsive contrast medium by
chemically triggering their ability to exhibit multiphoton-induced
luminescence (MIL) when performing multiphoton laser scanning microscopy
(MPM). Proof-of-principle is demonstrated using peptide-functionalized
AuNPs sensitive to zinc ions (Zn<sup>2+</sup>). Dispersed particles
are invisible in the MPM until addition of millimolar concentrations
of Zn<sup>2+</sup> upon which MIL is enabled through particle aggregation
caused by specific peptide interactions and folding. The process can
be reversed by removal of the Zn<sup>2+</sup> using a chelator, thereby
resuspending the AuNPs. In addition, the concept was demonstrated
by exposing the particles to matrix metalloproteinase-7 (MMP-7) causing
peptide digestion resulting in AuNP aggregation, significantly elevating
the MIL signal from the background. The approach is based on the principle
that aggregation shifts the plasmon resonance, elevating the absorption
cross section in the near-infrared wavelength region enabling onset
of MIL. This Letter demonstrates how biochemical sensing can be obtained
in far-field MPM and should be further exploited as a future tool
for noninvasive optical biosensing
Derivatization of a Bioorthogonal Protected Trisaccharide Linkerî—¸Toward Multimodal Tools for Chemical Biology
When cross-linking biomolecules to surfaces or to other
biomolecules,
the use of appropriate spacer molecules is of great importance. Mimicking
the naturally occurring spacer molecules will give further insight
into their role and function, possibly unveil important issues regarding
the importance of the specificity of carbohydrate-based anchor moieties,
in e.g., glycoproteins and glycosylphosphatidylinositols. Herein,
we present the synthesis of a lactoside-based trisaccharide, potentially
suitable as a heterobifunctional bioorthogonal linker molecule whereon
valuable chemical handles have been conjugated. An amino-derivative
having thiol functionality shows promise as novel SPR-surfaces. Furthermore,
the trisaccharide has been conjugated to a cholesterol moiety in combination
with a fluorophore which successfully assemble on the cell surface
in lipid microdomains, possibly lipid-rafts. Finally, a Cu<sup>I</sup>-catalyzed azide–alkyne cycloaddition reaction (CuAAC) confirms
the potential use of oligosaccharides as bioorthogonal linkers in
chemical biology
Local Refractive Index Sensing Based on Edge Gold-Coated Silver Nanoprisms
Bulk
and surface refractive index sensitivity for localized surface
plasmon resonance (LSPR) sensing based on edge gold-coated silver
nanoprisms (GSNPs) and gold nanospheres was investigated and compared
with conventional surface plasmon resonance (SPR) sensing based on
propagating surface plasmons. The hybrid GSNPs benefit from an improved
stability since the gold frame protecting the unstable silver facets
located at the silver nanoprisms (SNPs) edges and tips prevents truncation
or rounding of their sharp tips or edges, maintaining a high refractive
index sensitivity even under harsh conditions. By using layer-by-layer
deposition of polyelectrolytes and protein adsorption, we found that
GSNPs exhibit 4-fold higher local refractive index sensitivity in
close proximity (<10 nm) to the surface compared to a flat gold
film in the conventional SPR setup. Moreover, the sensitivity was
8-fold higher with GSNPs than with gold nanospheres. This shows that
relatively simple plasmonic nanostructures for LSPR-based sensing
can be engineered to outperform conventional SPR, which is particularly
interesting in the context of detecting low molecular weight compounds
where a small sensing volume, reducing bulk signals, is desired
Biofunctionalized Gold Nanoparticles for Colorimetric Sensing of Botulinum Neurotoxin A Light Chain
Botulinum
neurotoxin is considered as one of the most toxic food-borne
substances and is a potential bioweapon accessible to terrorists.
The development of an accurate, convenient, and rapid assay for botulinum
neurotoxins is therefore highly desirable for addressing biosafety
concerns. Herein, novel biotinylated peptide substrates designed to
mimic synaptosomal-associated protein 25 (SNAP-25) are utilized in
gold nanoparticle-based assays for colorimetric detection of botulinum
neurotoxin serotype A light chain (BoLcA). In these proteolytic assays,
biotinylated peptides serve as triggers for the aggregation of gold
nanoparticles, while the cleavage of these peptides by BoLcA prevents
nanoparticle aggregation. Two different assay strategies are described,
demonstrating limits of detection ranging from 5 to 0.1 nM of BoLcA
with an overall assay time of 4 h. These hybrid enzyme-responsive
nanomaterials provide rapid and sensitive detection for one of the
most toxic substances known to man
Additional file 1: Figure S1. of Antibacterial effects of Lactobacillus and bacteriocin PLNC8 αβ on the periodontal pathogen Porphyromonas gingivalis
Hydropathy scores of PLNC8 α and β. The amino acid sequence of PLNC8 α (A) and PLNC8 β (B) and their corresponding hydropathy score [46]. (TIF 369 kb
Histogram showing the effects of increasing the immobilisation levels by increasing the contact time during immobilisation (1–3 representing 1, 5, and 10 minutes) (Friedman p 0
<p><b>Copyright information:</b></p><p>Taken from "Hepatocyte growth factor (HGF) in fecal samples: rapid detection by surface plasmon resonance"</p><p>BMC Gastroenterology 2005;5():13-13.</p><p>Published online 12 Apr 2005</p><p>PMCID:PMC1090571.</p><p>Copyright © 2005 Nayeri et al; licensee BioMed Central Ltd.</p>01, Wilcoxon signed ranks test between 1 and 5 minutes p = 0.058, between 5 and 10 minutes p = 0.003, and between 1 and 10 minutes p = 0.003). The monoclonal anti-HGF (500 μg/ml) was diluted 1:10 in 10 mM acetate buffer pH 4.5. The activation time was 7 min, followed by a 1,5 and 10 min ligand injection respectively. Deactivation of remaining active esters was performed by a 7 min injection of ethanolamine/hydrochloride at pH 8.5. A flow rate of 5 μl/min was used during immobilisation
Nanoplasmonic Sensing from the Human Vision Perspective
Localized
surface plasmon resonance (LSPR) constitutes a versatile
technique for biodetection, exploiting the sensitivity of plasmonic
nanostructures to small changes in refractive index. The optical shift
in the LSPR band caused by molecular interactions in the vicinity
of the nanostructures are typically <5 nm and can readily be detected
by a spectrophotometer. Widespread use of LSPR-based sensors require
cost-effective devices and would benefit from sensing schemes that
enables use of very simple spectrophotometers or even naked-eye detection.
This paper describes a new strategy facilitating visualization of
minute optical responses in nanoplasmonic bioassays by taking into
account the physiology of human color vision. We demonstrate, using
a set of nine different plasmonic nanoparticles, that the cyan to
green transition zone at ∼500 nm is optimal for naked-eye detection
of color changes. In this wavelength range, it is possible to detect
a color change corresponding to a wavelength shift of ∼2–3
nm induced by refractive index changes in the medium or by molecular
binding to the surface of the nanoparticles. This strategy also can
be utilized to improve the performance of aggregation-based nanoplasmonic
colorimetric assays, which enables semiquantitative naked-eye detection
of matrix metalloproteinase 7 (MMP7) activity at concentrations that
are at least 5 times lower than previously reported assays using spherical
gold nanoparticles. We foresee significant potential of this strategy
in medical diagnostic and environmental monitoring, especially in
situations where basic laboratory infrastructure is sparse or even
nonexistent. Finally, we demonstrate that the developed concept can
be used in combination with cell phone technology and red–green–blue
(RGB) analysis for sensitive and quantitative detection of MMP7