These insights attempt to share with the community the lights and shadows of one emerging and exciting topic,
Food Microfluidics
, defined as microfluidic technology for food analysis and diagnosis ...in important areas such as food safety and quality. The reader is invited to question non-easy interrogations such as why
Food Microfluidics
, what is the next step and what could we do with the available technology. This article invites food analysts to be seduced by this technology and then to take an interesting trip departing from the main gained achievements, having a look at the crossing bridges over
Food Microfluidic
challenges or having a look at available technology to start. Finally, this trip arrives at a privileged place to gaze the horizons. A wonderful landscape - full of inspiration - for
Food Microfluidics
is anticipated. These insights have also been written wishing to give improved conceptual and realistic solutions for food analysis, with the additional hope to attract the community with exciting technology, in order to get novel and unexpected achievements in this field.
Food Microfluidics
: science, technology and creativity making food analysis safer, faster and easier.
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► Visual detection based gold and silver nanoparticles aggregation. ► Functionalized and non-functionalized nanoparticles. ► High selectivity and sensitivity. ► No complex ...instrumentation is required/chemical creativity for analyte detection.
Localized surface plasmon resonance (LSPR) is one of the most remarkable features of gold nanoparticles (Au NPs) and silver nanoparticles (Ag NPs). Due to these inherent optical properties, colloidal solutions of Au and Ag NPs have high extinction coefficients and different colour in the visible region of the spectrum when they are well-spaced in comparison with when they are aggregated. Therefore, a well-designed chemical interaction between the analyte and NPs surroundings leads to a change of colour (red to blue for Au NPs and yellow to brown for Ag NPs from well-spaced to aggregated ones, respectively) allowing the visual detection of the target analyte.
These approaches have exhibited an excellent analytical performance with high sensitivities due to the strong LSPR and excellent selectivity strategically driven by the interaction analyte-NPs surroundings involving mainly electrostatic and hydrogen bond interactions as well as donor–acceptor chemical reactions, among others. In addition, this kind of colorimetric assays has received considerable attention in the analytical field because of their simplicity and low cost since they do not require any expensive or complex instrumentation. As a consequence of this, detection of molecules with a high significance in the bio-medical, clinical, food safety and environmental fields including DNA, proteins and a wide spectrum of organic molecules as well as inorganic ions have been impressively reported in the most relevant literature using these assays.
This timely review offers a rational vision of the main achievements yielded in the relevant literature according to this exciting and creative analytical field.
Magnetocatalytic hybrid Janus micromotors encapsulating phenylboronic acid (PABA) modified graphene quantum dots (GQDs) are described herein as ultrafast sensors for the detection of deadly bacteria ...endotoxins. A bottom‐up approach was adopted to synthesize an oil‐in‐water emulsion containing the GQDs along with a high loading of platinum and iron oxide nanoparticles on one side of the Janus micromotor body. The two different “active regions” enable highly efficient propulsion in the presence of hydrogen peroxide or magnetic actuation without the addition of a chemical fuel. Fluorescence quenching was observed upon the interaction of GQDs with the target endotoxin (LPS), whereby the PABA tags acted as highly specific recognition receptors of the LPS core polysaccharide region. Such adaptive hybrid operation and highly specific detection hold considerable promise for diverse clinical, agrofood, and biological applications and integration in future lab‐on‐chip technology.
In the fast lane: Magnetocatalytic hybrid Janus micromotors encapsulating graphene quantum dots (GQDs) were developed as powerful mobile sensors for the detection of bacterial endotoxins. Two different active regions in the particles enabled bubble propulsion in the presence of hydrogen peroxide (see picture) or magnetic actuation without a chemical fuel. Fluorescence was quenched upon the interaction of the GQDs with the target endotoxin LPS.
Wearable sensors for noninvasive monitoring of physiological parameters is a growing technology in the clinical field. Especially in neonates, the development of portable and nonharmful monitoring ...devices is urgently needed because they cannot provide any feedback about discomfort or health complaints. However, in infant monitoring, only wearable sensors measuring physical parameters for vital signs have been developed. Here, we describe the first chemical wearable sensor for newborn monitoring. This fully integrated pacifier operates as a portable wireless device toward noninvasive chemical monitoring in the infant’s saliva. The infant’s mouth movements on the pacifier result in efficient saliva pumping and promote unidirectional flow from the mouth to the electrochemical chamber. The integrated electrochemical detection chamber, containing the enzymatic biosensor, is located outside of the oral cavity. The capabilities of the platform were studied for glucose detection in diabetic adults and compared to their blood levels with good correlation, demonstrating the sensor’s good performance. This baby-friendly device integrates saliva sampling with electrochemical sensing, along with miniaturized wireless electronics on a single pacifier platform. Such integration simplifies the infant′s health monitoring in a real-time and selective fashion, representing the first wearable sensor focusing on chemical saliva sensing in newborns. This initial demonstration of glucose monitoring introduces new possibilities for metabolites monitoring in infants and neonates using saliva as a noninvasive sample.
Janus micromotors encapsulating transition metal dichalcogenides (TMDs) and modified with a rhodamine (RhO)-labeled affinity peptide (RhO-NFMESLPRLGMH) are used here for
Salmonella enterica
endotoxin ...detection. The
OFF–ON
strategy relies on the specific binding of the peptide with the TMDs to induce fluorescence quenching (
OFF state
); which is next recovered due to selectively binding to the endotoxin (
ON state
). The increase in the fluorescence of the micromotors can be quantified as a function of the concentration of endotoxin in the sample. The developed strategy was applied to the determination of
Salmonella enterica
serovar Typhimurium endotoxin with high sensitivity (limits of detection (LODs) of 2.0 µg/mL using MoS
2
, and 1.2 µg/mL using WS
2
), with quantitative recoveries (ranging from 93.7 ± 4.6 % to 94.3 ± 6.6%) in bacteria cultures in just 5 min. No fluorescence recovery is observed in the presence of endotoxins with a similar structure, illustrating the high selectivity of the protocol, even against endotoxins of
Salmonella enterica
serovar Enteritidis with great similarity in its structure, demonstrating the high bacterial specificity of the developed method. These results revealed the analytical potential of the reported strategy in multiplexed assays using different receptors or in the design of portable detection devices.
Graphical abstract
Tubular micromotors composed of a hybrid single-wall carbon nanotube (SW)–Fe2O3 outer layer and powered by a MnO2 catalyst are used for phenylenediamines isomers detection and discrimination. ...Catalytic decomposition of H2O2 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 Fe2O3 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 o-phenylenediamine and p-phenylenediamine, respectively. The magnetic properties of the outer SW–Fe2O3 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.
Surface-enhanced Raman scattering (SERS) is a very promising tool for the direct detection of biomarkers for the diagnosis of i.e., cancer and pathogens. Yet, current SERS strategies are hampered by ...non-specific interactions with co-existing substances in the biological matrices and the difficulties of obtaining molecular fingerprint information from the complex vibrational spectrum. Raman signal enhancement is necessary, along with convenient surface modification and machine-based learning to address the former issues. This review aims to describe recent advances and prospects in SERS-based approaches for cancer and pathogens diagnosis. First, direct SERS strategies for key biomarker sensing, including the use of substrates such as plasmonic, semiconductor structures, and 3D order nanostructures for signal enhancement will be discussed. Secondly, we will illustrate recent advances for indirect diagnosis using active nanomaterials, Raman reporters, and specific capture elements as SERS tags. Thirdly, critical challenges for translating the potential of the SERS sensing techniques into clinical applications via machine learning and portable instrumentation will be described. The unique nature and integrated sensing capabilities of SERS provide great promise for early cancer diagnosis or fast pathogens detection, reducing sanitary costs but most importantly allowing disease prevention and decreasing mortality rates.
