This proof-of-concept study proposes a novel sensing mechanism for selective and label-free detection of 2,4,6-trinitrotoluene (TNT). It is realized by surface chemistry functionalization of silica nanoparticles (NPs) with 3-aminopropyl-triethoxysilane (APTES). The primary amine anchored to the surface of the silica nanoparticles (SiO2-NH2) acts as a capturing probe for TNT target binding to form Meisenheimer amine–TNT complexes. A colorimetric change of the self-assembled (SAM) NP samples from the initial green of a SiO2-NH2 nanoparticle film towards red was observed after successful attachment of TNT, which was confirmed as a result of the increased separation between the nanoparticles. The shift in the peak wavelength of the reflected light normal to the film surface and the associated change of the peak width were measured, and a merit function taking into account their combined effect was proposed for the detection of TNT concentrations from 10−12 to 10−4 molar. The selectivity of our sensing approach is confirmed by using TNT-bound nanoparticles incubated in AptamerX, with 2,4-dinitrotoluene (DNT) and toluene used as control and baseline, respectively. Our results show the repeatable systematic color change with the TNT concentration and the possibility to develop a robust, easy-to-use, and low-cost TNT detection method for performing a sensitive, reliable, and semi-quantitative detection in a wide detection range.
This work focuses on the development of optical sensors based on the LSPR phenomenon in nano-structured gold films suitable for detection of mycotoxins. A simple technology of annealing thin gold films was utilized for the formation of gold nano-islands exhibiting the LSPR effect. The morphology of gold nano-structures produced was studied with SEM and AFM while their optical properties were analysed with UV-vis absorption spectroscopy and spectroscopic ellipsometry (SE). A blue spectral shift of LSPR band caused by changes in the refractive index of medium constitutes the main principle of LSPR sensing. Bio-sensing tests were attempted using SE in total internal reflection mode (TIRE); a noticeable spectral shift was recorded on course of immune binding of aflatoxin B1 to specific antibodies immobilized on the surface of gold.
Detection of tiny quantities of nucleic acids, protein biomarkers and small organic molecules directly in complex matrices is of key relevance both in biomedical and in environmental fields. Moreover direct quantification of clinically relevant molecules (such as miRNA, DNA or proteins) in plasma is difficult due to its heterogeneous composition and the low amounts of target molecules. As for environmental pollutants (i.e. Aflatoxins), the direct detection is also hampered by the complexity of liquid samples (milk, wine, waste waters) lowering the sensitivities and requiring several steps of targets isolation and purification. Here we present our material platform based on microgels and hydrogel microparticles featuring high flexibility in performing detection and harvesting of different kind of targets in complex solutions.
This paper presents an LOC system combining microfluidic DEP channel with a CMOS image sensor for label and lens free detection and real-time counting of MCF-7 cells under continuous flow. Trapped and then released MCF-7 cells are accurately detected and counted under flow with a CMOS image sensor integrated underneath the DEP channel, for the first time in the literature. CMOS image sensor can capture 391 frames per second (fps) that allows detection of the released cells flowing through the channel with a flow rate up to 130 μl/min (0.468 m/s). Therefore, the proposed system is able to detect the cells under high flow where conventional techniques for cell quantification such as fluorescent tagging become unusable. Detected cells are automatically counted with a computer program and the counting accuracy of the whole system is 95%.
Okadaic acid (OA) is a representative diarrhetic shellfish poisoning toxin which is highly toxic and carcinogenic to human, and rich in polluted shellfish. In this work, a novel and high sensitive fluorescence immunosensor based on magnetic beads (MBs) and quantum dots (QDs) had been developed for OA detection. Carboxylic acid modified MBs were used as supporter to immobilize the OA-BSA, competed with the OA in the sample solution to bind with the anti-OA monoclonal antibody (OA-MAb). The CdTe QDs (EX600 nm) labeled IgG was served as secondary antibody to perform fluorescence detection. A portable flow cytometry, Moxi Flow was applied for OA on-site quantification. The results showed that the OA concentration was inversely proportional to the QDs fluorescence intensity. The limit of detection (LOD) was 0.05 μg/L with a linear range of 0.2–20 μg/L for OA detection, which was far lower than traditional id-ELISA strategy. Moreover, OA detection for the real sample could be completed within 1 hour. The matrix effect and the recovery rate were also assessed during real sample measurement, showing a high recovery.
The need for new, easy-to-use, home and decentralised diagnostics is now greater than ever and it is rapidly becoming apparent that biosensors can contribute substantially to reducing healthcare costs. New thinking is crucial to finding effective solutions that deliver the high quality of life rightly demanded by our ever ageing population while leveraging technology to deliver this in a cost-effective manner. Several key drivers are catalysing change. Personalised medicine recognises that every individual is different and needs a tailor-made health package; these differences can only be identified with an appropriate suite of diagnostics. Individuals are increasing recognising that data about their bodies should be owned by them and that they should have the choice to use and supplement this information. This generates consumer choice and drives evidence-based payment, where the success of outcomes needs to be measured. Focus on the individual and their needs drives decentralisation and the possible radical restructuring of how we deliver health management. We already see “health rooms” in pharmacies, but the next step will be health rooms in your home, in your pocket or on your wrist. These advances are underpinned by technologies facilitating mobility and data processing, but at the core are rapid, convenient and easy ways to measure our body chemistries at the genomic, proteomic and metabolomic levels. This presentation will focus on meeting these challenges using paper-based electronics, polymers and integrated electrochemical systems to deliver inexpensive instruments for a wide range of bioanalytical applications. Approaches will be illustrated by multi-parametric monitoring for the management of diabetes, chronic kidney disease and stress, reversible and label-free affinity sensors for cancer markers and heart disease, aptasensors for pathogens and cancer cells, and robust microbial-differentiation arrays. Further development will result in cost reduction and a diversity of formats such as point-of-care tests, smart packaging, telemetric strips and print-on-demand analytical devices.
A novel sandwich-type electrochemical aptasensor has been fabricated and applied for sensitive and selective detection of antibiotic oxytetracycline (OTC). This sensor was based on graphene-three dimensional nanostructure gold nanocomposite (GR-3D Au) and aptamer-AuNPs-horseradish peroxidase (HRP) nanoprobes as signal amplification. The aptamer and HRP modified Au nanoparticles provide high affinity and ultrasensitive electrochemical probe with excellent specificity for OTC.
Surface acoustic wave mediated transductions have been widely used in the sensors and actuators applications. In this study, a shear horizontal surface acoustic wave (SHSAW) was used for the detection of food pathogenic Escherichia coli O157:H7 (E.coli O157:H7), a dangerous strain among 225 E. coli unique serotypes. A few cells of this bacterium are able to cause young children to be most vulnerable to serious complications. Presence of higher than 1cfu E.coli O157:H7 in 25g of food has been considered as a dangerous level. The SHSAW biosensor was fabricated on 64° YX LiNbO3 substrate. Its sensitivity was enhanced by depositing 130.5nm thin layer of SiO2 nanostructures with particle size lesser than 70nm. The nanostructures act both as a waveguide as well as a physical surface modification of the sensor prior to biomolecular immobilization. A specific DNA sequence from E. coli O157:H7 having 22 mers as an amine-terminated probe ssDNA was immobilized on the thin film sensing area through chemical functionalization [(CHO-(CH2)3-CHO) and APTES; NH2-(CH2)3-Si(OC2H5)3]. The high-performance of sensor was shown with the specific oligonucleotide target and attained the sensitivity of 0.6439nM/0.1kHz and detection limit was down to 1.8femto-molar (1.8×10-15M). Further evidence was provided by specificity analysis using single mismatched and complementary oligonucleotide sequences.
Resistive pulse sensors, RPS, are allowing the transport mechanism of molecules, proteins and even nanoparticles to be characterized as they traverse small channels. Here we present our recent advancement of the technique identifying key experimental designs for potential POC assays. The first assay utilized superparamagnetic beads, if the surfaces of the beads are modified with an aptamer, the frequency of beads (translocations/minute) through the pore can be related to the concentration of specific proteins in the solution. Herein, we have demonstrated the successful use of TRPS to observe the binding of two proteins, to their specific aptamers simultaneously. We then adapt the measurement strategy and demonstrate that the translocation times of particles can be used to infer the zeta potential to measure the change in zeta potential of DNA modified particles. By measuring the translocation times of DNA modified nanoparticles as a function of packing density, length, structure, and hybridisation time, we observe a clear difference in zeta potential using both mean values, and population distributions as a function of the DNA structure. Finally we present the first comparison between assays that use resistive pulses or rectification ratios on a tunable pore platform.
This paper presents a preliminary investigation towards rapid prototyping of a low-cost biosensor based on reduced graphene oxide (rGO). The devices are fabricated via a laser scribing process and their functionality is demonstrated by their functionalization and subsequent immobilization of 7% bovine serum albumin (BSA). Non-faradaic electrochemical impedance spectroscopy (EIS) indicated a 33-42% decrease in impedance upon immobilization. An electroless nickel deposition process is demonstrated to enable electrical contacts to the device, with optimized plating conditions (pH, temperature) leading to a rGO-nickel contact resistance of 19 Ω/mm2.
We have developed a lithographically patterned flexible paper-based microfluidic device using photo polydimethylsiloxane (PDMS). Normal PDMS is converted into photosensitive PDMS with the desired photoinitiator. Further paper is lithographically patterned by photo PDMS to form hydrophobic region, where the flow of aqueous solution are restricted and a hydrophilic region, where fluids can flow by capillary action without any need of an external pump. The fabricated device can attain three-dimensional structured network flow on a single paper by repeated crease, without stacking multiple layers of individual paper.
Surface acoustic wave (SAW) devices are well-known for gravimetric sensor applications. In biosensing applications, chemical-and biochemically evoked adsorption processes at surfaces are detected in liquid environments using delay-line or resonator sensor configurations, preferably in combination with appropriate microfluidic devices. In this paper, a novel SAW-based impedance sensor type is introduced which uses only one interdigital electrode transducer (IDT) simultaneously as SAW generator and sensor element. It is shown that the amplitude of the reflected S-11 signal directly depends on the input impedance of the SAW device. The input impedance is strongly influenced by mass adsorption which causes a characteristic and measurable impedance mismatch.
Flight vehicles can soar around Earth via ejecting the combusted gases in the space and bio-molecular motor proteins possess the ability to walk along the tracts through hydrolyzing adenosine triphosphate (ATP) in cells. Inspired by flight vehicles and naturally occurring bio-molecular protein motors, miniaturized disk-like nanoswimmers are proposed, which are composed of three different metals: gold (Au), nickel (Ni), and platinum (Pt). The proposed nanoswimmers are fabricated via a layer-by-layer deposition method base on nano-electro-mechanical systems (NEMS) technology, whereby Pt functions as the chemical catalyst for the decomposition of hydrogen peroxide (H2O2) to produce oxygen (O2) bubbles detaching from its surface, which in turn generate recoil force to thrust nanoswimmers propelling forward. Herein, bubble propulsion mechanism originating from momentum change of a Au-Ni-Pt nanoswimmer-O2 bubble integral system is proposed to investigate the propulsion of nanoswimmers. Experiments are mainly focused on characterizing the propulsion of nanoswimmers in diluted H2O2 by changing the temperature of the solution. Results show that Au-Ni-Pt nanoswimmers are able to propel forward while the generated O2 bubbles are detached from the Pt-surface. The speeds of nanoswimmers are increased with the increment of temperature varying from 7°C to 57°C. It is concluded that the propulsion of nanoswimmers is temperature-dependent.
The use of ICT in the health care system is aimed to increase efficacy and decrease costs. We have designed a system and services for mobile monitoring of vital physiological parameters and environmental context. The system is based on a small multi-functional wireless body sensor for simultaneous measurement of ECG, temperature, heart rate, respiration rate, and movement. The sensor is wirelessly connected through Bluetooth Smart to a Smartphone. When necessary, the measurements are transferred to a server and can be accessed by authorized personnel. The contribution of the system to improved quality and efficiency of medical care is validated and estimated through several pilot studies.
Polymers are common housing materials in biosensor chips, but are often chemically less resistant than the biosensor components. Hence, modification procedures optimized for biosensor surfaces may affect potential chip materials. Still, it might be more economic to re-adapt a surface modification procedure than to re-establish a chip fabrication process with a chemically more stable polymer. In the following, potential means to deal with chemically less stable polymers are shown.
In this study, a new biosensor was developed based on a bacterial laccase immobilizing on Escherichia coli surface and direct glassy-carbon electrode adsorption of live cells. Expression and surface localization of laccases in target cells were confirmed by assays of Western blot, immunofluorescence microscopy and flow cytometry. The engineered cells served as a highly active whole cell laccase-catalytic system with an enzyme activity of 32.7 U/mL cells. Under optimized pH condition, electrochemical response of the biosensor was linear within concentration ranges of 5.0 μM to 500.0 μM for several phenolics (catechol, caffeic acid, dopamine, gallic acid, and 2-amino phenol) with a detection limit of 1.0 μM to 5.0 μM, which was comparable to those based on chemically-modified purified laccases. The system exhibited good stability and reproducibility. It also offered considerable level of accuracy for determination of the phenolic compound contents of wed wine, pharmaceutical and wastewater samples.
The influence of surface structuring on surface acoustic wave (SAW) biosensor signals has been investigated. Polymer structures on the sensor surfaces were applied by lithography or by self-assembling of polystyrene microparticles. In first experiments, structured and unstructured sensors led to similar results in a model affinity assay using streptavidin and biotinylated protein. On the other hand, structuring had a strong effect on SAW sensor signals obtained by protein adsorption on parylene C coated sensors. Depending on the protein, both decreased (albumin, streptavidin) and increased (fibrinogen) signals were observed with structured SAW sensors. Particularly the latter could contribute to facilitated blood analysis in the future.
The miniaturization of processes in Analytical Chemistry is a basic trend that has become quite relevant during the last years as well as low-cost methodologies. They offer advantageous characteristics for both, developed and developing countries, with special application to remote sensing, where untrained personnel and power facilities are scarce. Paper-devices have demonstrated their potentiality for this aim with disposable and inexpensive platforms. However, selectivity and sensitivity have to be ensured. In this context, a separation technique (electrophoresis) and a sensitive principle of detection (electrochemistry) are combined. Here we develop a folded paper-based device with integrated electrophoretic separation and electrochemical detection. The platform has different layers with hydrophobic wax barriers that delimit channels for performing both functions. Detection and separation has been demonstrated with epinephrine and hydroquinone analytes.
Analytical Chemistry is nowadays one of the branches of Chemistry that has changed enormously due to the advances in technology and the trends it follows. Currently, the development of low-cost devices that are, at the same time, easy-to use and dispose, and produce fast and reliable responses is of eminent significance. Electrochemical biosensors fit perfectly with these requirements, as do paper-based devices. Here we present an enzymatic biosensor using a simple single-use paper-based device in which carbon ink is deposited in a hydrophilic area delimited by wax printing for acting as working electrode. Low-cost gold-plated connector headers are employed as reference and auxiliary electrodes as well as connections to the potentiostat. Glucose oxidase (GOx), horseradish peroxidase (HRP) and potassium ferrocyanide used as mediator of the electron transfer are adsorbed in the ink.
In this work, a poly (methyl methacrylate) membrane containing micro-holes (MHs) as a prototype of a simple sensing platform of a lab-on-a-chip device has been developed for a potential analysis of clinical fluidic samples. A four probe electrochemical impedance spectroscopy (EIS) setup, with two electrodes placed on each side of the membrane, was adopted for monitoring the MH impedance (Fig. 1a). The setup was used to investigate, if EIS is suitable to sense the trapping of an analyte inside the MHs. Latex micro-beads with a diameter of 10 μm were used to test clogging of the MHs. Additionally, finite element model simulations were performed using Comsol Multiphysics software to theoretically evaluate the sensitivity field of the EIS measurement along the MHs.
