8 research outputs found
Self-Propelled Micromotors for Naked-Eye Detection of Phenylenediamines Isomers
Tubular
micromotors composed of a hybrid single-wall carbon nanotube
(SW)–Fe<sub>2</sub>O<sub>3</sub> outer layer and powered by
a MnO<sub>2</sub> catalyst are used for phenylenediamines isomers
detection and discrimination. Catalytic decomposition of H<sub>2</sub>O<sub>2</sub> as fuel results in the production of oxygen bubbles
and hydroxyl radicals for phenylenediamines dimerization to produce
colorful solutions in colorimetric assays. The combination of Fe<sub>2</sub>O<sub>3</sub> nanoparticles along with the irregular SW backbone
results in a rough catalytic layer for enhanced hydroxyl radical production
rate and improved analytical sensitivity. Such self-propelled micromotors
act as peroxidase-like mobile platforms that offer efficient phenylenediamines
detection and discrimination in just 15 min. Factors influencing the
colorimetric assay protocol, such as the navigation time and number
of motors, have been investigated. Low limits of detection (5 and
6 μM) and quantification (17 and 20 μM) were obtained
for <i>o</i>-phenylenediamine and <i>p</i>-phenylenediamine,
respectively. The magnetic properties of the outer SW–Fe<sub>2</sub>O<sub>3</sub> hybrid layer allow the reusability of the micromotors
in the colorimetric assay. Such attractive performance holds considerable
promise for its application in sensing systems in a myriad of environmental,
industrial, and health applications
Self-Propelled Enzyme-Based Motors for Smart Mobile Electrochemical and Optical Biosensing
A millimeter-sized
tubular motor for mobile biosensing of H<sub>2</sub>O<sub>2</sub> in
environmental and relevant clinical samples
is reported. The concept relies on the self-propelled motion by the
Marangoni effect, where the asymmetric release of SDS surfactant induces
fluid convection and rapid dispersion of horseradish peroxidase (HRP)
enzyme into the sample solution. This efficient movement together
with the continuous release of fresh enzyme leads to greatly accelerated
enzymatic reaction processes without the need of external stirring
or chemical and physical attachment of the enzyme as in common classical
biosensing approaches. In this strategy, the use of a single millimeter-sized
tubular motor during 120 s allows the reliable and accurate quantification
of hydrogen peroxide in a set of different matrices such as tap and
mineral waters, urine, plasma, and tumor cell cultures treated with
antineoplasic Cisplatin without any previous sample preparation. Furthermore,
detection can be performed electrochemically, optically, and via visual
detection, which makes this approach a clear candidate as a point-of-care
analytical tool
Self-Propelled Enzyme-Based Motors for Smart Mobile Electrochemical and Optical Biosensing
A millimeter-sized
tubular motor for mobile biosensing of H<sub>2</sub>O<sub>2</sub> in
environmental and relevant clinical samples
is reported. The concept relies on the self-propelled motion by the
Marangoni effect, where the asymmetric release of SDS surfactant induces
fluid convection and rapid dispersion of horseradish peroxidase (HRP)
enzyme into the sample solution. This efficient movement together
with the continuous release of fresh enzyme leads to greatly accelerated
enzymatic reaction processes without the need of external stirring
or chemical and physical attachment of the enzyme as in common classical
biosensing approaches. In this strategy, the use of a single millimeter-sized
tubular motor during 120 s allows the reliable and accurate quantification
of hydrogen peroxide in a set of different matrices such as tap and
mineral waters, urine, plasma, and tumor cell cultures treated with
antineoplasic Cisplatin without any previous sample preparation. Furthermore,
detection can be performed electrochemically, optically, and via visual
detection, which makes this approach a clear candidate as a point-of-care
analytical tool
Biosensing Strategy for Simultaneous and Accurate Quantitative Analysis of Mycotoxins in Food Samples Using Unmodified Graphene Micromotors
A high-performance
graphene-based micromotor strategy for simultaneous,
fast, and reliable assessment of two highly concerning mycotoxins
(fumonisin B1 (FB1) and ocratoxin A (OTA)) has successfully been developed.
The assay principle is based on the selective recognition from aptamers
to the target mycotoxins and further “on-the-move” fluorescence <i>quenching</i> of the free aptamer in the outer layer of unmodified
reduced graphene (rGO; sensing layer) micromotors. Template-prepared
rGO/platinum nanoparticles (PtNPs) tubular micromotors were synthesized
rapidly and inexpensively by the direct electrodeposition within the
conical pores of a polycarbonate template membrane. The new wash-free
approach offers using just 1 μL of sample, a simultaneous and
rapid “on-the-fly” detection (2 min) with high sensitivity
(limits of detection of 7 and 0.4 ng/mL for OTA and FB1, respectively),
and high selectivity. Remarkable accuracy (<i>E</i><sub>r</sub> < 5%) during the mycotoxin determination in certified
reference material as well as excellent quantitative recoveries (96–98%)
during the analysis of food samples were also obtained. The excellent
results obtained allow envisioning an exciting future for the development
of novel applications of catalytic micromotors in unexplored fields
such as food safety diagnosis
Biosensing Strategy for Simultaneous and Accurate Quantitative Analysis of Mycotoxins in Food Samples Using Unmodified Graphene Micromotors
A high-performance
graphene-based micromotor strategy for simultaneous,
fast, and reliable assessment of two highly concerning mycotoxins
(fumonisin B1 (FB1) and ocratoxin A (OTA)) has successfully been developed.
The assay principle is based on the selective recognition from aptamers
to the target mycotoxins and further “on-the-move” fluorescence <i>quenching</i> of the free aptamer in the outer layer of unmodified
reduced graphene (rGO; sensing layer) micromotors. Template-prepared
rGO/platinum nanoparticles (PtNPs) tubular micromotors were synthesized
rapidly and inexpensively by the direct electrodeposition within the
conical pores of a polycarbonate template membrane. The new wash-free
approach offers using just 1 μL of sample, a simultaneous and
rapid “on-the-fly” detection (2 min) with high sensitivity
(limits of detection of 7 and 0.4 ng/mL for OTA and FB1, respectively),
and high selectivity. Remarkable accuracy (<i>E</i><sub>r</sub> < 5%) during the mycotoxin determination in certified
reference material as well as excellent quantitative recoveries (96–98%)
during the analysis of food samples were also obtained. The excellent
results obtained allow envisioning an exciting future for the development
of novel applications of catalytic micromotors in unexplored fields
such as food safety diagnosis
Enzyme-Based Microfluidic Chip Coupled to Graphene Electrodes for the Detection of D‑Amino Acid Enantiomer-Biomarkers
An electrochemical microfluidic strategy
for the separation and
enantiomeric detection of d-methionine (d-Met) and d-leucine (d-Leu) is presented. These D-amino acids
(D-AAs) act as biomarkers involved in relevant diseases caused by <i>Vibrio cholerae</i>. On a single layout microfluidic chip (MC),
highly compatible with extremely low biological sample consumption,
the strategy allowed the controlled microfluidic D-AA separation and
the specific reaction between D-amino acid oxidase (DAAO) and each
D-AA biomarker avoiding the use of additives (i.e., cyclodextrins)
for enantiomeric separation as well as any covalent immobilization
of the enzyme into the wall channels or on the electrode surface such
as in the biosensor-based approaches. Hybrid polymer/graphene-based
electrodes were end-channel coupled to the microfluidic system to
improve the analytical performance. d-Met and d-Leu
were successfully detected becoming this proof-of-the-concept a promising
principle for the development of point-of-care (POC) devices for <i>in situ</i> screening of <i>V. cholerae</i> related
diseases
Superhydrophobic Alkanethiol-Coated Microsubmarines for Effective Removal of Oil
We demonstrate the use of artificial nanomachines for effective interaction, capture, transport, and removal of oil droplets. The simple nanomachine-enabled oil collection method is based on modifying microtube engines with a superhydrophobic layer able to adsorb oil by means of its strong adhesion to a long chain of self-assembled monolayers (SAMs) of alkanethiols created on the rough gold outer surface of the device. The resultant SAM-coated Au/Ni/PEDOT/Pt microsubmarine displays continuous interaction with large oil droplets and is capable of loading and transporting multiple small oil droplets. The influence of the alkanethiol chain length, polarity, and head functional group and hence of the surface hydrophobicity upon the oil–nanomotor interaction and the propulsion is examined. No such oil–motor interactions were observed in control experiments involving both unmodified microengines and microengines coated with SAM layers containing a polar terminal group. These results demonstrate that such SAM-Au/Ni/PEDOT/Pt micromachines can be useful for a facile, rapid, and efficient collection of oils in water samples, which can be potentially exploited for other water–oil separation systems. The integration of oil-sorption properties into self-propelled microengines holds great promise for the remediation of oil-contaminated water samples and for the isolation of other hydrophobic targets, such as drugs
Acoustic Microcannons: Toward Advanced Microballistics
Acoustically
triggered microcannons, capable of loading and firing
nanobullets (Nbs), are presented as powerful microballistic tools.
Hollow conically shaped microcannon structures have been synthesized
electrochemically and fully loaded with nanobullets made of silica
or fluorescent microspheres, and perfluorocarbon emulsions, embedded
in a gel matrix stabilizer. Application of a focused ultrasound pulse
leads to the spontaneous vaporization of the perfluorocarbon emulsions
within the microcannon and results in the rapid ejection of the nanobullets.
Such Nbs “firing” at remarkably high speeds (on the
magnitude of meters per second) has been modeled theoretically and
demonstrated experimentally. Arrays of microcannons anchored in a
template membrane were used to demonstrate the efficient Nbs loading
and the high penetration capabilities of the ejected Nbs in a tissue
phantom gel. This acoustic-microcannon approach could be translated
into advanced microscale ballistic tools, capable of efficient loading
and firing of multiple cargoes, and offer improved accessibility to
target locations and enhanced tissue penetration properties