Detection of Circulating Cancer Cells Using Electrocatalytic Gold Nanoparticles

A rapid cancer cell detection and quantification assay, based on the electrocatalytic properties of gold nanoparticles towards the hydrogen evolution reaction, is described. The selective labeling of cancer cells is performed in suspension, allowing a fast interaction between the gold nanoparticle labels and the target proteins expressed at the cell membrane. The subsequent electrochemical detection is accomplished with small volumes of sample and user‐friendly equipment through a simple electrochemical method that generates a fast electrochemical response used for the quantification of nanoparticle‐labeled cancer cells. The system establishes a selective cell‐detection assay capable of detecting 4 × 10³ cancer cells in suspension that can be extended to several other cells detection scenarios.     

Bioluminescent nanopaper for rapid screening of toxic substances

Environmental pollution is threatening human health and ecosystems as a result of modern agricultural techniques and industrial progress. A simple nanopaper-based platform coupled with luminescent bacteria Aliivibrio fischeri (A. fischeri) as a bio-indicator is presented here, for rapid and sensitive evaluation of contaminant toxicity. When exposed to toxicants, the luminescence inhibition of A. fischeri-decorated bioluminescent nanopaper (BLN) can be quantified and analyzed to classify the toxicity level of a pollutant. The BLN composite was characterized in terms of morphology and functionality. Given the outstanding biocompatibility of nanocellulose for bacterial proliferation, BLN achieved high sensitivity with a low cost and simplified procedure compared to conventional instruments for laboratory use only. The broad applicability of BLN devices to environmental samples was studied in spiked real matrices (lake and sea water), and their potential for direct and in situ toxicity screening was demonstrated. The BLN architecture not only survives but also maintains its function during freezing and recycling processes, endowing the BLN system with competitive advantages as a deliverable, ready-to-use device for large-scale manufacturing. The novel luminescent bacteria-immobilized, nanocelullose-based device shows outstanding abilities for toxicity bioassays of hazardous compounds, bringing new possibilities for cheap and efficient environmental monitoring of potential contamination.

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Architecting Graphene Oxide Rolled‐Up Micromotors: A Simple Paper‐Based Manufacturing Technology

A graphene oxide rolled‐up tube production process is reported using wax‐printed membranes for the fabrication of on‐demand engineered micromotors at different levels of oxidation, thickness, and lateral dimensions. The resultant graphene oxide rolled‐up tubes can show magnetic and catalytic movement within the addition of magnetic nanoparticles or sputtered platinum in the surface of graphene‐oxide‐modified wax‐printed membranes prior to the scrolling process. As a proof of concept, the as‐prepared catalytic graphene oxide rolled‐up micromotors are successfully exploited for oil removal from water. This micromotor production technology relies on an easy, operator‐friendly, fast, and cost‐efficient wax‐printed paper‐based method and may offer a myriad of hybrid devices and applications.     

Bacterial isolation by lectin-modified microengines

New template-based self-propelled gold/nickel/polyaniline/platinum (Au/Ni/PANI/Pt) microtubular engines, functionalized with the Concanavalin A (ConA) lectin bioreceptor, are shown to be extremely useful for the rapid, real-time isolation of Escherichia coli (E. coli) bacteria from fuel-enhanced environmental, food, and clinical samples. These multifunctional microtube engines combine the selective capture of E. coli with the uptake of polymeric drug-carrier particles to provide an attractive motion-based theranostics strategy. Triggered release of the captured bacteria is demonstrated by movement through a low-pH glycine-based dissociation solution. The smaller size of the new polymer-metal microengines offers convenient, direct, and label-free optical visualization of the captured bacteria and discrimination against nontarget cells.     

Crystal and electrochemical properties of water dispersed CdS nanocrystals obtained via reverse micelles and arrested precipitation

Different methods of synthesis for the production of electroactive nanocrystals (NCs) for use as labels in DNA sensing systems are presented. They are based on two general ways of controlling the formation and growth of the nanoparticles: (a) physical restriction of the volume available for the growth of the individual nanoparticles by using templates such as reverse micelles; (b) arrested precipitation that depends on exhaustion of one of the reactants. The water dispersed nanocrystals thus obtained are then characterized by optical or electrochemical techniques so as to evaluate the quality of the prepared NCs. A novel direct electrochemical stripping detection protocol that involves the use of a bismuth modified graphite epoxy composite electrode is developed and applied so as to quantify the CdS NCs. The electrochemical study revealed a linear dependency of the stripping current upon the concentration of CdS NCs with a detection limit of around 10(15) CdS NCs cm(-3). The obtained NCs are of great interest for future applications in electrochemical genosensors.     

Trading quantization precision for update rates for systems with limited communication in the uplink channel

In many situations, control applications have to exchange information through limited bandwidth communication channels, which affect their behavior. For that reason, there is a strong need for methods that maximize the relevancy of the exchanged control signals. In general, increasing control signals’ update frequency improves the disturbance rejection abilities whereas increasing their quantization precision improves the steady state performance. However, when the bandwidth is limited, increasing the update frequency necessitates the reduction of the quantization precision and vice versa. Motivated by these observations, and focusing on the uplink bandwidth limitations, an approach for the dynamical online state feedback assignment of control inputs’ quantization precision and update rate is proposed. This approach, which is based on the model predictive control technique, enables us to choose the update rate and the quantization levels of control signals from a predefined set, in order to optimize the control performance. Practical stability properties of the approach are then studied. Finally, the effectiveness of the proposed method is illustrated on a simulation example.     

A nanochannel/nanoparticle-based filtering and sensing platform for direct detection of a cancer biomarker in blood

A rapid nanochannel-based immunoassay capable of the filtering and subsequent detection of proteins in whole blood without any sample preparation is described. This is accomplished by using a nanoporous/nanochannel membrane modified with antibodies, the conductivity of which toward a redox indicator is tuned by primary and secondary immunoreactions with proteins and gold nanoparticles. This interesting nanopore blockage by gold nanoparticles is enhanced by silver deposition that further decreases the diffusion of the signaling indicator through the nanochannel. The efficiency of the nanochannels to act as immunoreaction platforms including the use of nanoparticles is also monitored by microscopic techniques. Successful detection of immunoglobulins including a cancer biomarker is achieved in buffer as well as in whole blood. This system constitutes an efficient immunoassay capable of detecting up to 52 U mL(-1) of CA15-3. The developed nanochannel/nanoparticle-based device can be used for several other proteins and extended also to DNA detection with interest not only for diagnostics but also environmental monitoring, food analysis, safety, and security applications.     

Magnetic Nanoparticles Modified with Carbon Nanotubes for Electrocatalytic Magnetoswitchable Biosensing Applications

A novel biosensor based on magnetic nanoparticles (MNPs) functionalized with tyrosinase in an operational synergy with a multiwalled carbon nanotube (MWCNT) network is developed. An on–off external magnetic field is applied to a screen‐printed electrode (SPE), which is used as a transducing platform. This enables an interesting on‐demand biosensing performance. The effect of each component on the response of the developed device is carefully evaluated; particularly interesting results are presented for the contributions of MNPs and carbon nanotubes. A tyrosinase‐based model biosensing approach is used, while a potential of ?0.15 V versus Ag/AgCl for the electrochemical reduction of the enzyme products (quinone forms) onto the magnetoswitchable SPE/MNP/Tyr/MWCNT system is applied. The response of the biosensor to catechol is also evaluated; a limit of detection (signal to noise ratio (S/N) = 3) for catechol is found to be around 7.61 μM (S/N = 3) with a relative standard deviation (RSD) of 4.91% (n = 3). The developed device could open the door to a wide range of novel electrocatalytic and bioelectrocatalytic applications of magnetocontrolled redox enzymes. Furthermore, it could be used in miniaturized and portable biosensing systems, such as lab‐on‐a‐chip devices, in medical and environmental applications that have a restricted quantity of sample. Further applications could be envisaged for many other fields, such as external control of catalytic transformations in bioreactors, tailoring of reversible amperometric immunosensors, regeneration of enzyme‐biosensor electrodes, and external triggering of biofuel cells.     

Invariance properties for a class of quasipolynomials

When a time-delay system involves multiple imaginary roots (MIRs), the stability analysis will become much more complicated than that in the case with only simple imaginary roots (SIRs). An MIR may exhibit different splitting behaviors and, to the best of the authors’ knowledge, their properties have not been fully investigated. In this paper, we focus on characterizing the invariance properties for MIRs with any multiplicity. Furthermore, the proposed methodology makes it possible to also cover some degenerate cases already encountered and discussed in the literature. In addition, we propose an easily implemented frequency-sweeping method, making it possible to derive the asymptotic behavior without invoking the Puiseux series.     

Integrated Devices for Non-Invasive Diagnostics

“Sample-in-answer-out” type integrated diagnostic devices have been widely recognized as the ultimate solution to simplify testing across healthcare systems. Such systems are equipped with advanced fluidic, mechanical, chemical, biological, and electronic components to handle patient samples without any manual steps therefore have the potential to accelerate intervention and improve patient outcomes. In this regard, the combination of integrated devices and non-invasive sampling has gained a substantial interest to further improve the comfort and safety of patients. In this Review, the pioneering developments in integrated diagnostics are covered and their potential in non-invasive sampling is discussed. The key properties of possible sample types are highlighted by addressing their relevance for the clinical practice. Last, the factors affecting the transition of integrated devices from academia to the market are identified by analyzing the technology readiness levels of selected examples and alternative remedies are explored to increase the rate of survival during this transition.