4 research outputs found
Aptamer-Controlled Reversible Inhibition of Gold Nanozyme Activity for Pesticide Sensing
This study addresses the need for
rapid pesticide (acetamiprid)
detection by reporting a new colorimetric biosensing assay. Our approach
combines the inherent peroxidase-like nanozyme activity of gold nanoparticles
(GNPs) with high affinity and specificity of an acetamiprid-specific
S-18 aptamer to detect this neurotoxic pesticide in a highly rapid,
specific, and sensitive manner. It is shown that the nanozyme activity
of GNPs can be inhibited by its surface passivation with target-specific
aptamer molecules. Similar to an enzymatic competitive inhibition
process, in the presence of a cognate target, these aptamer molecules
leave the GNP surface in a target concentration-dependent manner,
reactivating GNP nanozyme activity. This reversible inhibition of
the GNP nanozyme activity can either be directly visualized in the
form of color change of the peroxidase reaction product or can be
quantified using UV–visible absorbance spectroscopy. This approach
allowed detection of 0.1 ppm acetamiprid within an assay time of 10
min. This reversible nanozyme activation/inhibition strategy may in
principle be universally applicable for the detection of a range of
environmental or biomedical molecules of interest
Competitive Inhibition of the Enzyme-Mimic Activity of Gd-Based Nanorods toward Highly Specific Colorimetric Sensing of l‑Cysteine
Gd-based
nanomaterials offer interesting magnetic properties and have been heavily investigated
for magnetic resonance imaging. The applicability of these materials
beyond biomedical imaging remains limited. The current study explores
the applicability of these rare-earth nanomaterials as nanozyme-mediated
catalysts for colorimetric sensing of l-cysteine, an amino
acid of high biomedical relevance. We show a facile solution-based
strategy to synthesize two Gd-based nanomaterials viz. GdÂ(OH)<sub>3</sub> and Gd<sub>2</sub>O<sub>3</sub> nanorods. We further establish
the catalytic peroxidase-mimic nanozyme activity of these GdÂ(OH)<sub>3</sub> and Gd<sub>2</sub>O<sub>3</sub> nanorods. This catalytic
activity was suppressed specifically in the presence of l-cysteine that allowed us to develop a colorimetric sensor to detect
this biologically relevant molecule among various other contaminants.
This suppression, which could either be caused due to catalyst poisoning
or enzyme inhibition, prompted extensive investigation of the kinetics
of this catalytic inhibition in the presence of cysteine. This revealed
a competitive inhibition process, a mechanism akin to those observed
in natural enzymes, bringing nanozymes a step closer to the biological
systems
Ultrasensitive Colorimetric Detection of Murine Norovirus Using NanoZyme Aptasensor
Human
norovirus (NoV) remains the most common cause of viral gastroenteritis
and the leading cause of viral foodborne outbreaks globally. NoV is
highly pathogenic with an estimated median viral infective dose (ID<sub>50</sub>) ranging from 18 to 1015 genome copies. For NoV detection,
the only reliable and sensitive method available for detection and
quantification is reverse transcription quantitative polymerase chain
reaction (RTqPCR). NoV detection in food is particularly challenging,
requiring matrix specific concentration of the virus and removal of
inhibitory compounds to detection assays. Hence, the RTqPCR method
poses some challenges for rapid in-field or point-of-care diagnostic
applications. We propose a new colorimetric NanoZyme aptasensor strategy
for rapid (10 min) and ultrasensitive (calculated Limit of Detection
(LoD) of 3 viruses per assay equivalent to 30 viruses/mL of sample
and experimentally demonstrated LoD of 20 viruses per assay equivalent
to 200 viruses/mL) detection of the infective murine norovirus (MNV),
a readily cultivable surrogate for NoV. Our approach combines the
enzyme-mimic catalytic activity of gold nanoparticles with high target
specificity of an MNV aptamer to create sensor probes that produce
a blue color in the presence of this norovirus, such that the color
intensity provides the virus concentrations. Overall, our strategy
offers the most sensitive detection of norovirus or a norovirus surrogate
achieved to date using a biosensor approach, enabling for the first
time, the detection of MNV virion corresponding to the lower end of
the ID<sub>50</sub> for NoV. We further demonstrate the robustness
of the norovirus NanoZyme aptasensor by testing its performance in
the presence of other nontarget microorganisms, human serum and shellfish
homogenate, supporting the potential of detecting norovirus in complex
matrices. This new assay format can, therefore, be of significant
importance as it allows ultrasensitive norovirus detection rapidly
within minutes, while also offering the simplicity of use and need
for nonspecialized laboratory infrastructure
Visible-Light-Triggered Reactive-Oxygen-Species-Mediated Antibacterial Activity of Peroxidase-Mimic CuO Nanorods
The
rapid emergence of antibiotic-resistant bacterial strains warrants
new strategies for infection control. NanoZymes are emerging as a
new class of catalytic nanomaterials that mimic the biological action
of natural enzymes. The development of photoactive NanoZymes offers
a promising avenue to use light as a “trigger” to modulate
the bacterial activity. Visible light activity is particularly desirable
because it contributes to 44% of the total solar energy. Here we show
that the favorable band structure of a CuO-nanorod-based NanoZyme
catalyst (band gap of 1.44 eV) allows visible light to control the
antibacterial activity. Photomodulation of the peroxidase-mimic activity
of CuO nanorods enhances its affinity to H<sub>2</sub>O<sub>2</sub>, thereby remarkably accelerating the production of reactive oxygen
species (ROS) by 20 times. This photoinduced NanoZyme-mediated ROS
production catalyzes physical damage to the bacterial cells, thereby
enhancing the antibacterial performance against Gram-negative-indicator
bacteria <i>Escherichia coli</i>