Search

Enzyme-based electrochemical biosensors have been widely deployed for the detection of a range of contaminants in different food products due to their significant advantages over other (bio)sensing techniques. Nevertheless, their performance is greatly affected by the sample matrix itself or by the matrix they are presented with in pretreated samples, both of which can impact the accuracy as well as the sensitivity of the measurements. Therefore, and in order to acquire reliable and accurate measurements, matrix effects and their influence on sensor performance should be taken into consideration. Herein, acetylcholinesterase (AChE)-modified electrochemical sensors were employed for the detection of pesticides in vegetable oils. Sensor interrogation with pretreated oil samples, spiked with carbofuran, revealed the inhibitory potential of the extracted matrix varies between different types of vegetable oil and their fatty acid content. In addition, synergies between the extracted matrix from different types of vegetable oils and the carbamate pesticide, carbofuran, were observed, which led to significant deviations of the sensor’s performance from its anticipated behavior in buffered solution. Taking the aforementioned into consideration, appropriate calibration curves for each type of vegetable oil were drafted, which allowed for the highly reproducible determination of different pesticide concentrations in pretreated real samples. Collectively, a better understanding of AChE inhibition by single or multiple contaminants present in vegetable oils was gained, which can find many applications in numerous fields, ranging from sensor development to the design of new pesticides and medicinal products.

The emergence of the novel coronavirus, SARS-CoV-2, has highlighted the need for rapid, accurate, and point-of-care diagnostic testing. Lab-on-a-Chip (LoC) devices offer the possibility to run such tests at a low cost, while at the same time permitting the multiplexed detection of several viruses when coupled with microarray detection of the amplified products. Herein, we report the development of a protocol for the qualitative detection of SARS-CoV-2, through the design of appropriate primers that target the evolutionary conserved regions of the virus. The proposed protocol relies on an improved version of asymmetric RT-PCR, the linear-after-the-exponential (LATE)-PCR that uses primers that are deliberately designed for use at unequal concentrations. As a result, LATE-PCR exhibits similar efficiency to symmetric PCR, while promoting accumulation of single-stranded products that can subsequently hybridize to a single-strand DNA probe-spotted microarray. The performance of the developed LATE-PCR protocol was compared to that of symmetric RT-PCR, and validated with the use of artificial viral RNA and nasopharyngeal swab samples from real patients. Furthermore, and in order to illustrate its potential for integration into a biosensor platform, the amplicons were allowed to hybridize with probes that were covalently immobilized onto commercially available functionalized glass, without the need for heat denaturation.

Electrochemical biosensors are increasingly used for the detection of various analytes (pesticides, mycotoxins etc.) in food, due to the rapid and reliable detection that can be achieved without the need for expensive instrumentation equipment, skilled personnel and long time-to–result that is required by conventional analytical techniques. Laser Induced Forward Transfer (LIFT) bio-printing in combination with an all- in- one enzyme solution (a solution that includes the enzyme mixed with signal-enhancing carbon-based materials suspended in a polymer matrix) provides new possibilities for biosensor pesticide detection in olive oil as it delivers direct and accurate immobilization of enzyme solution with high special resolution and the ability to print in significantly smaller electrode surfaces for less material waste. Here, we report the use of LIFT technique, utilizing a 355 nanosecond laser for the highly precise, direct deposition and immobilization of Acetylcholinesterase (AChE) on screen printed electrode (SPE) surfaces. Due to the high impact pressure of the transferred droplets at the receiver substrate, the physical adsorption of the enzyme mixture onto the surface is enhanced, improving the electrochemical communication with the SPE. The inhibitory effect of the analytes on the AChE biosensor was evaluated amperometrically by determining the decrease in the current obtained for the oxidation of the thiocholine produced by the enzyme upon incubation with pesticide solutions, and a LoD below the legislation limit (10 ppb) was achieved. Furthermore, the biosensor’s performance was assessed in olive oil samples spiked with carbofuran and chlorpyrifos, following an optimized pretreatment protocol, with very satisfactory recovery values.

Despite the fact that a considerable amount of effort has been invested in the development of biosensors for the detection of pesticides, there is still a lack of a simple and low-cost platform that can reliably and sensitively detect their presence in real samples. Herein, an enzyme-based biosensor for the determination of both carbamate and organophosphorus pesticides is presented that is based on acetylcholinesterase (AChE) immobilized on commercially available screen-printed carbon electrodes (SPEs) modified with carbon black (CB), as a means to enhance their conductivity. Most interestingly, two different methodologies to deposit the enzyme onto the sensor surfaces were followed, strikingly different results were obtained depending on the family of pesticides under investigation. Furthermore, and towards the uniform application of the functionalization layer onto the SPEs&rsquo, surfaces, the laser induced forward transfer (LIFT) technique was employed in conjunction with CB functionalization, which allowed a considerable improvement of the sensor&rsquo, s performance. Under the optimized conditions, the fabricated sensors can effectively detect carbofuran in a linear range from 1.1 &times, 10&minus, 9 to 2.3 &times, 8 mol/L, with a limit of detection equal to 0.6 &times, 9 mol/L and chlorpyrifos in a linear range from 0.7 &times, 9 up to 1.4 &times, 8 mol/L and a limit of detection 0.4 &times, 9 mol/L in buffer. The developed biosensor was also interrogated with olive oil samples, and was able to detect both pesticides at concentrations below 10 ppb, which is the maximum residue limit permitted by the European Food Safety Authority.

Laser Induced Forward Transfer (LIFT) process has been utilized as a novel microfabrication tool for the printing of a plurality of organic and inorganic materials, both in liquid and in solid phase, with dimensions down to a few microns, on substrates such as glass, silicon and flexible polymers. LIFT is a direct-write method that can print viable bioinks including living cells in predefined 2D or 3D patterns. It offers many advantages over other direct-write techniques: It is contact-less, offers high spatial control (10-100μm) and is able to print a great variety of materials in terms of viscosity.

An impedimetric label-free aptasensor for the simultaneous and highly selective detection of two pesticides is presented. The sensor is based on the combination of self-assembled platinum nanoparticle two-dimensional films (produced in room temperature via the magnetron sputtering technique) and target specific nucleic acids (a.k.a. aptamers). The platinum nanoparticle films have been deposited on top of SiO 2 substrates previously patterned with interdigitated electrodes. The surface of the device has been chemically modified in order to enhance the subsequent aptamer deposition and immobilization. Two distinctive aptamer configurations have been employed in order to facilitate capturing and detection of two pesticides, namely acetamiprid and atrazine. Successful binding events between aptamer and target induce a shift in the impedance of the aptasensor which can be attributed in charge transport hindrance through the nanoparticle film. The incorporation of the nanoparticle film in the fabrication of the aptasensor significantly improves the performance of the device if compared to “naked” interdigitated based aptasensors, allowing the highly sensitive and selective detection of acetamiprid and atrazine down to 0.6 × 10 − 11 M and 0.4 × 10 − 10 M respectively.

Immunosensor sensitivity and stability depend on a number of parameters such as the orientation, the surface density, and the antigen-binding efficiency of antibodies following their immobilization onto functionalized surfaces. A number of techniques have been developed to improve the performance of an immunosensor that targets one or both of the parameters mentioned above. Herein, two widely employed techniques are compared for the first time, which do not require any complex engineering of neither the antibodies nor the surfaces onto which the former get immobilized. To optimize the different surface functionalization protocols and compare their efficiency, a model antibody-antigen system was employed that resembles the complex matrices immunosensors are frequently faced with in real conditions. The obtained results reveal that protein A/G is much more efficient in increasing antibody loading onto the surfaces in comparison to boronate ester chemistry. Despite the fact, therefore, that both contribute towards the orientation-specific immobilization of antibodies and hence enhance their antigen-binding efficiency, it is the increased antibody surface density attained with the use of protein A/G that plays a critical role in achieving maximal antigen recognition.

In this paper, we present the development of a photonic biosensor device for cancer treatment monitoring as a complementary diagnostics tool. The proposed device combines multidisciplinary concepts from the photonic, nano-biochemical, micro-fluidic and reader/packaging platforms aiming to overcome limitations related to detection reliability, sensitivity, specificity, compactness and cost issues. The photonic sensor is based on an array of six asymmetric Mach Zender Interferometer (aMZI) waveguides on silicon nitride substrates and the sensing is performed by measuring the phase shift of the output signal, caused by the binding of the analyte on the functionalized aMZI surface. According to the morphological design of the waveguides, an improved sensitivity is achieved in comparison to the current technologies (

BIOFOS aims to further develop and validate a reusable and high-added value Lab-on-Chip (LoC) based, micro-biophotonic sensor platform for in situ monitoring of food contaminants. The Lab-on-Chip was tested on milk (aflatoxin M1, antibiotics and lactose), olive oil (pesticides and metals), nuts (aflatoxin B1) and dehydrated fruits (ochratoxin A). BIOFOS combines the most promising concepts from the photonic, biological, nanochemical and fluidic parts of Lab-on-Chip systems, aiming to achieve low sensitivity and high specificity, excellent reliability and compactness. Current methodologies for detection of food contamination based on heavy analytical tools cannot guarantee a safe and stable food supply. The reasons are the complexity, the long time-to-result (2-3 days) and the cost of these tools, which limit the number of samples that can be practically analyzed at food processing and storage sites. Preliminary results for almonds spiked with aflatoxin B1 are presented. First results suggest that BIOFOS has sensitivity enough for AFB1, even that the concentration is at ppb level. More data are still required, and many analyses are ongoing in the laboratory. Results are not enough to conclude about any characteristics of the device performance, even then repeatability seems very good (variation less than 3% at 25 ppb) and recovery is acceptable (78.4%), while decision limit and detection capability are still uncertain.

Considering both cancer's serious impact on public health and the side effects of cancer treatments, strategies towards targeted cancer therapy have lately gained considerable interest. Employment of gold nanoparticles (GNPs), in combination with ionizing and non-ionizing radiations, has been shown to improve the effect of radiation treatment significantly. GNPs, as high-Z particles, possess the ability to absorb ionizing radiation and enhance the deposited dose within the targeted tumors. Furthermore, they can convert non-ionizing radiation into heat, due to plasmon resonance, leading to hyperthermic damage to cancer cells. These observations, also supported by experimental evidence both in vitro and in vivo systems, reveal the capacity of GNPs to act as radiosensitizers for different types of radiation. In addition, they can be chemically modified to selectively target tumors, which renders them suitable for future cancer treatment therapies. Herein, a current review of the latest data on the physical properties of GNPs and their effects on GNP circulation time, biodistribution and clearance, as well as their interactions with plasma proteins and the immune system, is presented. Emphasis is also given with an in depth discussion on the underlying physical and biological mechanisms of radiosensitization. Furthermore, simulation data are provided on the use of GNPs in photothermal therapy upon non-ionizing laser irradiation treatment. Finally, the results obtained from the application of GNPs at clinical trials and pre-clinical experiments in vivo are reported. (C) 2017 Elsevier Inc. All rights reserved.

In this paper, we present the immobilization of thiol-modified aptamers on alkyne- or alkene-terminated silicon nitride surfaces by laser-induced click chemistry reactions. The aptamers are printed onto the surface by laser-induced forward transfer (LIFT), which also induces the covalent bonding of the aptamers by thiol-ene or thiol-yne reactions that occur upon UV irradiation of the thiol-modified aptamers with ns laser pulses. This combination of LIFT and laser-induced click chemistry allows the creation of high-resolution patterns without the need for masks. Whereas the click chemistry already takes place during the printing process (single-step process) by the laser pulse used for the printing process, further irradiation of the LIFT-printed aptamers by laser pulses (two-step process) leads to a further increase in the immobilization efficiency. (Figure Presented).

We extend our previous simulation study and we present experimental results regarding our Fast Fourier Transform method for the calculation of the resonance shifts in biosensors based on micro-ring resonators (MRRs). For the simulation study, we use a system model with a tunable laser at 850 nm, an MRR with 1.5∙10sup4/supquality factor, and a detection system with 50 dB maximum signal-to-noise ratio, and investigate the impact on the system performance of factors like the number of the resonance peaks inside the scanning window, the wavelength dependence of the laser power, and the asymmetry of the transfer functions of the MRRs. We find that the performance is improved by a factor of 2 when we go from single- to four-peak transfer functions, and that the impact of the wavelength dependence of the laser power is very low. We also find that the presence of asymmetries can lead to strong discontinuities of the transfer functions at the edges of the scanning window and can significantly increase the measurement errors, making necessary the use of techniques for their elimination. Using these conclusions, we build a system with sensing MRRs on TriPleX platform, and we experimentally validate our method using sucrose solutions with different concentrations. Involving techniques in order to exclude the noise originating from the microfluidic system, we achieve a wavelength resolution close to 0.08 pm, when the system operates with 0.5 pm scanning step. In combination with the sensitivity of the MRRs, which is measured to be equal to 93.7 nm/RIU, this wavelength resolution indicates the possibility for a limit of detection close to 8.5·10sup-7/supRIU, which represents to the best of our knowledge a record performance for this type of optical sensors and this level of scanning steps.