Synthesis of dual models multivalent activatable aptamers based on HCR and RCA for ultrasensitive detection of Salmonella typhimurium

Aptamers have superior structural properties and have been widely used in bacterial detection methods. However, the problem of low affinity still exists in complex sample detection. In contrast, hybridization chain reaction (HCR)-based model I and rolling circle amplification (RCA)-based model II multivalent activatable aptamers (multi-Apts) can fulfill the need for low-cost, rapid, highly sensitive and high affinity detection of S. typhimurium. In our research, two models of multi-Apts were designed. First, a monovalent activatable aptamer (mono-Apt) was constructed by fluorescence resonance energy transfer (FRET) with an S. typhimurium aptamer and its complementary chain of BHQ1. Next, the DNA scaffold was obtained by HCR and RCA, and the multi-Apts were obtained by self-assembly of the mono-Apt with a DNA scaffold. In model I, when target was presented, the complementary chain BHQ1 was released due to the binding of multi-Apts to the target and was subsequently adsorbed by UIO66. Finally, a FRET-based fluorescence detection signal was obtained. In mode II, the multi-Apts bound to the target, and the complementary chain BHQ1 was released to become the trigger chain for the next round of amplification of HCR with a fluorescence detection signal. HCR and RCA based multi-Apts were able to detect S. typhimurium as low as 2 CFU mL-1 and 1 CFU mL-1 respectively. Multi-Apts amplification strategy provides a new method for early diagnosis of pathogenic microorganisms in foods.

A novel electrochemical aptasensor based on core-shell nanomaterial labeling for simultaneous detection of acetamiprid and malathion

At present, due to the coexistence of multiple pesticides in vegetables and the enhanced toxicity, a simultaneous detection method for multiple pesticides is urgently needed. In this work, two types of core-shell nanomaterials, Ag-Au core-shell nanoparticles (Ag@Au NPs) and Cu2O-Au core-shell nanoparticles (Cu2O@Au NPs), were synthesized and labeled with acetamiprid aptamer and malathion aptamer to prepare two novel electroactive signal probes, respectively. The two probes were hybridized on the surface of the electrode by the principle of base complementary pairing between the aptamers and the thiolated DNA oligonucleotide sequences, and a dual-signal electrochemical aptasensor for the simultaneous detection of acetamiprid and malathion was established by modified glassy carbon electrode (GCE). The limits of detection (LOD) were calculated to be 43.7 pg mL-1 for acetamiprid and 63.4 pg mL-1 for malathion. The aptasensor determined acetamiprid and malathion in spinach and rape with the recovery rates of 88.9%-112.5% and 98.0%-114.1%, respectively.

Trends and prospects of 2-D tungsten disulphide (WS2) hybrid nanosystems for environmental and biomedical applications

Recently, 2D layered transition metal dichalcogenides (TMDCs) with their ultrathin sheet nanostructure and diversified electronic structure have drawn attention for various advanced applications to achieve high-performance parameters. Unique 2D TMDCs mainly comprise transition metal and chalcogen element where chalcogen element layers sandwich the transition metal element layer. In such a case, various properties can be enhanced and controlled depending on the targeted application. Among manipulative 2D TMDCs, tungsten disulphide (WS2) is one of the emerging nano-system due to its fascinating properties in terms of direct band gap, higher mobility, strong photoluminescence, good thermal stability, and strong magnetic field interaction. The advancement in characterization techniques, especially scattering techniques, can help in study of opto-electronic properties of 2D TMDCs along with determination of layer variations and investigation of defect. In this review, the fabrication and applications are well summarized to optimize an appropriate WS2-TMDCs assembly according to focused field of research. Here, the scientific investigations on 2D WS2 are studied in terms of its structure, role of scattering techniques to study its properties, and synthesis routes followed by its potential applications for environmental remediation (e.g., photocatalytic degradation of pollutants, gas sensing, and wastewater treatment) and biomedical domain (e.g., drug delivery, photothermal therapy, biomedical imaging, and biosensing). Further, a special emphasis is given to the significance of 2D WS2 as a substrate for surface-enhanced Raman scattering (SERS). The discussion is further extended to commercial and industrial aspects, keeping in view major research gaps in existing research studies.

Portable multichannel detection instrument based on time-resolved fluorescence immunochromatographic test strip for on-site detecting pesticide residues in vegetables

In this work, a portable multichannel detection instrument based on time-resolved fluorescence immunochromatographic test strip (TRFIS) was proposed for on-site detecting pesticide residues in vegetables. Its hardware consisted of a silicon photodiode and excitation light source array, a mainboard of the lower machine with STMicroelectronics 32 (STM32) and a linear stepping motor. While detecting, cardboard with 6-channel TRFIS was pulled into the cassette by the stepping motor. The peak area of the test (T) line and control (C) line of each TRFIS was sampled and calculated by software, then the concentration of the detected pesticide was obtained according to the ratio of the T to C value. This instrument could sample 6-channel TRFIS within 30 s simultaneously, and it exhibited excellent accuracy with a 2.5% average coefficient of variation for each channel (n = 12). In addition, the TRFIS was constructed by using europium oxide time-resolved fluorescent microspheres to label the monoclonal antibody against acetamiprid and form a fluorescent probe, which was fixed on the binding pad. The TRFIS was used for the detection of acetamiprid in celery cabbage, cauliflower and baby cabbage. This instrument was used to complete the qualitative and quantitative analysis of the TRFIS, so as to enhance the practical application of the detection method. This TRFIS possessed excellent linearity ranging from 0.25 mg kg-1 to 1.75 mg kg-1 for the detection of acetamiprid, and the limit of detection were 0.056-0.074 mg kg-1 in the different vegetable matrix. The platform combines the accuracy and portability of traditional test strips with the highly sensitive and efficient fluorescence intensity recognition function of detection equipment, which shows a great application prospect of multi-channel rapid detection of small molecule pollutants in the field.

Impact of nanotechnology on conventional and artificial intelligence-based biosensing strategies for the detection of viruses

Recent years have witnessed the emergence of several viruses and other pathogens. Some of these infectious diseases have spread globally, resulting in pandemics. Although biosensors of various types have been utilized for virus detection, their limited sensitivity remains an issue. Therefore, the development of better diagnostic tools that facilitate the more efficient detection of viruses and other pathogens has become important. Nanotechnology has been recognized as a powerful tool for the detection of viruses, and it is expected to change the landscape of virus detection and analysis. Recently, nanomaterials have gained enormous attention for their value in improving biosensor performance owing to their high surface-to-volume ratio and quantum size effects. This article reviews the impact of nanotechnology on the design, development, and performance of sensors for the detection of viruses. Special attention has been paid to nanoscale materials, various types of nanobiosensors, the internet of medical things, and artificial intelligence-based viral diagnostic techniques.

Biosensors in 2022

Sixty years have passed since Clark and Lyons proposed the concept of using glucose enzyme electrodes to monitor the oxygen that is consumed during an enzyme-catalyzed reaction [...].

On spot detection of nickel and cobalt from exhausted batteries by a smart electrochemical sensor

This work presents the realization and the application of an user-friendly electrochemical platform based on screen-printed electrodes for the simultaneous determination of nickel and cobalt ions in real samples by means of square wave adsorptive stripping voltammetry (SWAdSV). The sensor was realized by electrodepositing in situ a bismuth film onto graphite screen-printed electrodes (GSPEs). The sensor surface was fully characterized by scanning electron microscopy (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The experimental conditions for the determination of nickel and cobalt in the form of dimethylglyoximate complexes were studied and optimized. Linear calibration curves for Ni(II) and Co(II), determined individually and together, in the range 10-40 μg/L for nickel and 10-60 μg/L for cobalt, respectively, were obtained. The limits of detection for nickel and cobalt determination were 2.5 μg/L and 2.4 μg/L, respectively. The performance of the sensor in terms of reproducibility and selectivity was also studied. The applicability of the developed platform was assessed by determining nickel and cobalt in samples deriving from an industrial process of recycling exhausted batteries and in soil samples.

Interconversion between [2Fe-2S] and [4Fe-4S] cluster glutathione complexes

We present here how different iron-sulfide-glutathione ratios, applied in in vitro conditions comparable to those present in the mitochondrial matrix, affect the speciation of iron-sulfur cluster glutathione complexes. An excess of sulfide with respect to iron ions promotes the formation of a tetranuclear [Fe^II₂Fe^III₂S₄(GS)₄]^2- complex, while an excess of iron ions favors the formation of a dinuclear [Fe^IIFe^IIIS₂(GS)₄]^3- complex. These two complexes establish an interconversion equilibrium. The latter might play a role in the composition of the mitochondrial labile iron pool potentially contributing to the regulation of cellular iron homeostasis.

Aptasensors for lysozyme detection: Recent advances

Lysozyme is an enzyme existing in multiple organisms where it plays various vital roles. The most important role is its antibacterial activity in the human body; in fact, it is also called "the body's own antibiotic". Despite its proven utility, lysozyme can potentially trigger allergic reactions in sensitive individuals, even in trace amounts. Therefore, lysozyme determination in foods is becoming of paramount importance. Traditional detection methods are expensive, time-consuming and they cannot be applied for fast in-situ quantification. Electrochemical and optical sensors have attracted an increasing attention due to their versatility and ability to reduce the disadvantages of traditional methods. Using an aptamer as the bioreceptor, the sensor selectivity is amplified due to the specific recognition of the analyte. This review is presenting the progresses made in lysozyme determination by means of electrochemical and optical aptasensors in the last five years. A critical overview on the methodologies employed for aptamer immobilization and on the strategies for signal amplification of the assays will be described. Different optical and electrochemical aptasensors will be discussed and compared in terms of analytical performances, versatility and real samples applications.

Emerging nanobiotechnology in agriculture for the management of pesticide residues

Utilization of pesticides is often necessary for meeting commercial requirements for crop quality and yield. However, incessant global pesticide use poses potential risks to human and ecosystem health. This situation increases the urgency of developing nano-biotechnology-assisted pesticide formulations that have high efficacy and low risk of side effects. The risks associated with both conventional and nanopesticides are summarized in this review. Moreover, the management of residual pesticides is still a global challenge. The contamination of soil and water resources with pesticides has adverse impact over agricultural productivity and food security; ultimately posing threats to living organisms. Pesticide residues in the eco-system may be treated via several biological and physicochemical processes, such as microbe-based degradation and advanced oxidation processes. With these issues in mind, we present a review that explores both existing and emerging techniques for management of pesticide residues and environmental risks. These techniques can offer a sustainable solution to revitalize the tarnished water/soil resources. Further, state-of-the-art research approaches to investigate biotechnological alternatives to conventional pesticides are discussed along with future prospects and mitigation techniques are recommended.

Mycotoxins aptasensing: From molecular docking to electrochemical detection of deoxynivalenol

This work proposes a voltammetric aptasensor to detect deoxynivalenol (DON) mycotoxin. The development steps of the aptasensor were partnered for the first time to a computational study to gain insights onto the molecular mechanisms involved into the interaction between a thiol-tethered DNA aptamer (80mer-SH) and DON. The exploited docking study allowed to find the binding region of the oligonucleotide sequence and to determine DON preferred orientation. A biotinylated oligonucleotide sequence (20mer-BIO) complementary to the aptamer was chosen to carry out a competitive format. Graphite screen-printed electrodes (GSPEs) were electrochemically modified with polyaniline and gold nanoparticles (AuNPs@PANI) by means of cyclic voltammetry (CV) and worked as a scaffold for the immobilization of the DNA aptamer. Solutions containing increasing concentrations of DON and a fixed amount of 20mer-BIO were dropped onto the aptasensor surface: the resulting hybrids were labeled with an alkaline phosphatase (ALP) conjugate to hydrolyze 1-naphthyl phosphate (1-NPP) substrate into 1-naphthol product, detected by differential pulse voltammetry (DPV). According to its competitive format, the aptasensor response was signal-off in the range 5.0-30.0 ng·mL^-1 DON. A detection limit of 3.2 ng·mL^-1 was achieved within a 1-hour detection time. Preliminary experiments on maize flour samples spiked with DON yielded good recovery values.

Folding-Based Electrochemical Aptasensor for the Determination of β-Lactoglobulin on Poly-L-Lysine Modified Graphite Electrodes

Nowadays, food allergy is a very important health issue, causing adverse reactions of the immune system when exposed to different allergens present in food. Because of this, the development of point-of-use devices using miniaturized, user-friendly, and low-cost instrumentation has become of outstanding importance. According to this, electrochemical aptasensors have been demonstrated as useful tools to quantify a broad variety of targets. In this work, we develop a simple methodology for the determination of β-lactoglobulin (β-LG) in food samples using a folding-based electrochemical aptasensor built on poly-L-lysine modified graphite screen-printed electrodes (GSPEs) and an anti-β-lactoglobulin aptamer tagged with methylene blue (MB). This aptamer changes its conformation when the sample contains β-LG, and due to this, the spacing between MB and the electrode surface (and therefore the electron transfer efficiency) also changes. The response of this biosensor was linear for concentrations of β-LG within the range 0.1-10 ng·mL-1, with a limit of detection of 0.09 ng·mL-1. The biosensor was satisfactorily employed for the determination of spiked β-LG in real food samples.

Nanovehicles for Plant Modifications towards Pest- and Disease-Resistance Traits

In agriculture, plant transformation is a versatile platform for crop improvement with the aim of increased pest resistance and an improved nutrient profile. Nanotechnology can overcome several challenges that face conventional methods of gene delivery. Specifically, nanomaterials offer an optimal platform for biomolecule delivery with unique physiochemical properties as well as the ability to traverse the challenging barrier of the plant cell wall. We review the potential of diverse nanovehicles for biomolecule delivery in plant systems to obtain desired genetic traits. The efficacy of nanoparticles against pests or pathogens is also explored, as well as the interaction of nanovehicles with plant organelles, with due consideration of the effects and toxic profile of nanoparticles.

Nano-Biosensing Platforms for Detection of Cow's Milk Allergens: An Overview

Among prevalent food allergies, cow milk allergy (CMA) is most common and may persist throughout the life. The allergic individuals are exposed to a constant threat due to milk proteins' presence in uncounted food products like yogurt, cheese, and bakery items. The problem can be more severe due to cross-reactivity of the milk allergens in the food products due to homologous milk proteins of diverse species. This problem can be overcome by proper and reliable food labeling in order to ensure the life quality of allergic persons. Therefore, highly sensitive and accurate analytical techniques should be developed to detect the food allergens. Here, significant research advances in biosensors (specifically immunosensors and aptasensors) are reviewed for detection of the milk allergens. Different allergic proteins of cow milk are described here along with the analytical standard methods for their detection. Additionally, the commercial status of biosensors is also discussed in comparison to conventional techniques like enzyme-linked immunosorbent assay (ELISA). The development of novel biosensing mechanisms/kits for milk allergens detection is imperative from the perspective of enforcement of labeling regulations and directives keeping in view the sensitive individuals.

NanoMIP-based approach for the suppression of interference signals in electrochemical sensors

Herein, we describe the use of molecularly imprinted nanoparticles (nanoMIPs) as sequestering (masking) agents, to suppress the signal coming from interfering molecules and facilitate the detection of the target analyte. In this work, ascorbic acid was used as a model interfering molecule in dopamine electrochemical detection. NanoMIPs selective for ascorbic acid demonstrated to be capable of binding and suppressing electrochemical signal from ascorbic acid, enabling the detection of dopamine in the range 100-500 nM, without any need for sample pre-treatment. Tests in real samples (spiked human serum) were also carried out successfully. Due to the generic nature of the imprinting process, the proposed approach can be tailored to suppress potentially any interfering species, by simply varying the type of nanoMIPs used.

Point-of-Care Strategies for Detection of Waterborne Pathogens

Waterborne diseases that originated due to pathogen microorganisms are emerging as a serious global health concern. Therefore, rapid, accurate, and specific detection of these microorganisms (i.e., bacteria, viruses, protozoa, and parasitic pathogens) in water resources has become a requirement of water quality assessment. Significant research has been conducted to develop rapid, efficient, scalable, and affordable sensing techniques to detect biological contaminants. State-of-the-art technology-assisted smart sensors have improved features (high sensitivity and very low detection limit) and can perform in a real-time manner. However, there is still a need to promote this area of research, keeping global aspects and demand in mind. Keeping this view, this article was designed carefully and critically to explore sensing technologies developed for the detection of biological contaminants. Advancements using paper-based assays, microfluidic platforms, and lateral flow devices are discussed in this report. The emerging recent trends, mainly point-of-care (POC) technologies, of water safety analysis are also discussed here, along with challenges and future prospective applications of these smart sensing technologies for water health diagnostics.

Electrochemical Nanocomposite Single-Use Sensor for Dopamine Detection

In this work, we report the development of a simple and sensitive sensor based on graphite screen-printed electrodes (GSPEs) modified by a nanocomposite film for dopamine (DA) detection. The sensor was realized by electrodepositing polyaniline (PANI) and gold nanoparticles (AuNPs) onto the graphite working electrode. The sensor surface was fully characterized by means of the cyclic voltammetry (CV) technique using [Fe(CN)6]4-/3- and [Ru(NH3)6]2+/3+ as redox probes. The electrochemical behavior of the nanocomposite sensor towards DA oxidation was assessed by differential pulse voltammetry (DPV) in phosphate buffer saline at physiological pH. The sensor response was found to be linearly related to DA concentration in the range 1-100 μM DA, with a limit of detection of 0.86 μM. The performance of the sensor in terms of reproducibility and selectivity was also studied. Finally, the sensor was successfully applied for a preliminary DA determination in human serum samples.

Electrochemical enzyme-linked oligonucleotide array for aflatoxin B1 detection

In this work, an electrochemical enzyme-linked oligonucleotide array to achieve simple and rapid multidetection of aflatoxin B₁ (AFB₁) is presented. The assay is based on a competitive format and disposable screen-printed cells (SPCs). Firstly, the electrodeposition of poly(aniline-anthranilic acid) copolymer (PANI-PAA) on graphite screen-printed working electrodes was performed by means of cyclic voltammetry (CV). Aflatoxin B₁ conjugated with bovine serum albumin (AFB₁-BSA) was then immobilized by covalent binding on PANI-PAA copolymer. After performing the affinity reaction between AFB₁ and the biotinylated DNA-aptamer (apt-BIO), the solution was dropped on the modified SPCs and the competition was carried out. The biotinylated complexes formed onto the sensor surface were coupled with a streptavidin-alkaline phosphatase conjugate. 1-naphthyl phosphate was used as enzymatic substrate; the electroactive product was detected by differential pulse voltammetry (DPV). The response of the enzyme-linked oligonucleotide assay was signal-off, according to the competitive format. A dose-response curve was obtained between 0.1 ng mL^-1 and 10 ng mL^-1 and a limit of detection of 0.086 ng mL^-1 was achieved. Finally, preliminary experiments in maize flour samples spiked with AFB₁ were also performed.

Latest Trends in Electrochemical Sensors for Neurotransmitters: A Review

Neurotransmitters are endogenous chemical messengers which play an important role in many of the brain functions, abnormal levels being correlated with physical, psychotic and neurodegenerative diseases such as Alzheimer's, Parkinson's, and Huntington's disease. Therefore, their sensitive and robust detection is of great clinical significance. Electrochemical methods have been intensively used in the last decades for neurotransmitter detection, outclassing more complicated analytical techniques such as conventional spectrophotometry, chromatography, fluorescence, flow injection, and capillary electrophoresis. In this manuscript, the most successful and promising electrochemical enzyme-free and enzymatic sensors for neurotransmitter detection are reviewed. Focusing on the activity of worldwide researchers mainly during the last ten years (2010-2019), without pretending to be exhaustive, we present an overview of the progress made in sensing strategies during this time. Particular emphasis is placed on nanostructured-based sensors, which show a substantial improvement of the analytical performances. This review also examines the progress made in biosensors for neurotransmitter measurements in vitro, in vivo and ex vivo.

Nano-based smart pesticide formulations: Emerging opportunities for agriculture

The incorporation of nanotechnology as a means for nanopesticides is in the early stage of development. The main idea behind this incorporation is to lower the indiscriminate use of conventional pesticides to be in line with safe environmental applications. Nanoencapsulated pesticides can provide controlled release kinetics, while efficiently enhancing permeability, stability, and solubility. Nanoencapsulation can enhance the pest-control efficiency over extended durations by preventing the premature degradation of active ingredients (AIs) under harsh environmental conditions. This review is thus organized to critically assess the significant role of nanotechnology for encapsulation of AIs for pesticides. The smart delivery of pesticides is essential to reduce the dosage of AIs with enhanced efficacy and to overcome pesticide loss (e.g., due to leaching and evaporation). The future trends of pesticide nanoformulations including nanomaterials as AIs and nanoemulsions of biopesticides are also explored. This review should thus offer a valuable guide for establishing regulatory frameworks related to field applications of these nano-based pesticides in the near future.

Electrochemical Immunosensors for Disease Detection and Diagnosis

Background:

The detection of biological molecules referred as biomarkers in biological fluids is fundamental in clinical analysis because it permits to discriminate between healthy and ill individuals and to evaluate the progress of a disease. The development of immunosensors for the detection and monitoring of biomarkers is currently a major area of research and, as more markers are discovered and their role in disease becomes better understood, this will continue to grow.

Methods:

We report the research progresses of electrochemical immunosensor applied in clinical analysis that have been published in the last three years.

Results:

The emphasis of this review is on the advances of the electrochemical immunosensors for detection and monitoring of cancerous, cardiovascular and neurological diseases. An immunosensor overview was presented as well as the biomarkers and biosensing systems currently used to detect the onset and monitor the progression of the mentioned diseases.

Conclusions:

Electrochemical biosensors focusing on a vast repertoire of analytes are now becoming one of the most widely explored scientific fields. This is due to their enormous potential in clinical diagnosis and biological process monitoring.

DNA-Based Sensor for the Detection of an Organophosphorus Pesticide: Profenofos

In this work, we propose an electrochemical DNA aptasensor for the detection of profenofos, an organophosphorus pesticide, based on a competitive format and disposable graphite screen-printed electrodes (GSPEs). A thiol-tethered DNA capture probe, which results to be complementary to the chosen aptamer sequence, was immobilised on gold nanoparticles/polyaniline composite film-modified electrodes (AuNPs/PANI/GSPE). Different profenofos solutions containing a fixed amount of the biotinylated DNA aptamer were dropped onto the realized aptasensors. The hybridisation reaction was measured using a streptavidin-alkaline phosphatase enzyme conjugate, which catalyses the hydrolysis of 1-naphthyl -phosphate. The 1-naphtol enzymatic product was detected by means of differential pulse voltammetry (DPV). The aptasensor showed itself to work as a signal off sensor, according to the competitive format used. A dose response curve was obtained between 0.10 μM and 10 μM with a detection limit of 0.27 μM.

MIP-Based Sensors: Promising New Tools for Cancer Biomarker Determination

Detecting cancer disease at an early stage is one of the most important issues for increasing the survival rate of patients. Cancer biomarker detection helps to provide a diagnosis before the disease becomes incurable in later stages. Biomarkers can also be used to evaluate the progression of therapies and surgery treatments. In recent years, molecularly imprinted polymer (MIP) based sensors have been intensely investigated as promising analytical devices in several fields, including clinical analysis, offering desired portability, fast response, specificity, and low cost. The aim of this review is to provide readers with an overview on recent important achievements in MIP-based sensors coupled to various transducers (e.g., electrochemical, optical, and piezoelectric) for the determination of cancer biomarkers by selected publications from 2012 to 2016.

Aptamer Sensors

In the last years, great progress has been accomplished in the development of aptamer sensors with different transducers. In order to improve the sensitivity of these biosensors, several methodologies have been employed. In this Special Issue, the state of art and the future trends in the field of aptamer sensors have been explored.

Measurement of volatile organic compounds (VOCs) in libraries and archives in Florence (Italy)

Indoor air samples from libraries and archives in Florence, Italy, were collected and analysed for a variety of volatile organic compounds. The aim was to perform a characterisation of the indoor air quality, and try to elucidate if there are VOCs that may cause or result from the determination of the cultural heritage institutions. All compounds of interest were regularly detected, with BTEXs (Benzene, Toluene, Ethylbenzene, Xylenes) being the most abundant and followed by cyclic volatile methylsiloxanes, aldehydes, terpenes and organic acids. The prevalence and qualitative characteristics, such as concentrations, profiles and indoor/outdoor ratios of BTEXs underline the important influence of the outdoor air infiltrations on the indoor air concentrations. Acetic acid that is a substance that can oxidise books and other exposed objects was detected at concentrations ranging between 1.04 and 18.9μgm^-3, while furfural, that is a known marker of paper degradation, was constantly present at concentrations that ranged between 5.26 and 32.6μgm^-3. This work shows the importance that indoor air quality monitoring campaigns can have in order to give early warning to cultural heritage institution managers about the impact that indoor air quality can have on exposed and/or preserved objects.

Binding affinity of amyloid oligomers to cellular membranes is a generic indicator of cellular dysfunction in protein misfolding diseases

The conversion of peptides or proteins from their soluble native states into intractable amyloid deposits is associated with a wide range of human disorders. Misfolded protein oligomers formed during the process of aggregation have been identified as the primary pathogenic agents in many such conditions. Here, we show the existence of a quantitative relationship between the degree of binding to neuronal cells of different types of oligomers formed from a model protein, HypF-N, and the GM1 content of the plasma membranes. In addition, remarkably similar behavior is observed for oligomers of the Aβ₄₂ peptide associated with Alzheimer’s disease. Further analysis has revealed the existence of a linear correlation between the level of the influx of Ca²⁺ across neuronal membranes that triggers cellular damage, and the fraction of oligomeric species bound to the membrane. Our findings indicate that the susceptibility of neuronal cells to different types of misfolded oligomeric assemblies is directly related to the extent of binding of such oligomers to the cellular membrane.

Acetamiprid multidetection by disposable electrochemical DNA aptasensor

In this work, we propose an electrochemical DNA aptasensor for sensitive multidetection of acetamiprid based on a competitive format and disposable screen-printed arrays. To improve the sensitivity of the aptasensor, polyaniline film and gold nanoparticles were progressively electrodeposited on the graphite screen-printed electrode surface by cyclic voltammetry. Gold nanoparticles were then employed as platform for thiol-tethered DNA aptamer immobilization. Different acetamiprid solutions containing a fixed amount of biotinylated complementary oligonucleotide sequence by DNA aptasensor arrays were analyzed. Streptavidin-alkaline phosphatase conjugate was then added to trace the affinity reaction. The enzyme catalyzed the hydrolysis of 1-naphthyl phosphate to 1-naphthol. The enzymatic product was detected by differential pulse voltammetry. A decrease of the signal was obtained when the pesticide concentration was increased, making the sensor work as signal off sensor. Under optimized conditions by testing key experimental parameters, a dose-response curve was constructed between 0.25 and 2.0µM acetamiprid concentration range and a limit of detection of 0.086µM was calculated. The selectivity of the aptasensor was also confirmed by the analysis of atrazine pesticide. Finally, preliminary experiments in fruit juice samples spiked with acetamiprid were also performed.

Electrochemical, Electrochemiluminescence, and Photoelectrochemical Aptamer-Based Nanostructured Sensors for Biomarker Analysis

Aptamer-based sensors have been intensively investigated as potential analytical tools in clinical analysis providing the desired portability, fast response, sensitivity, and specificity, in addition to lower cost and simplicity versus conventional methods. The aim of this review, without pretending to be exhaustive, is to give the readers an overview of recent important achievements about electrochemical, electrochemiluminescence, and photoelectrochemical aptasensors for the protein biomarker determination, mainly cancer related biomarkers, by selected recent publications. Special emphasis is placed on nanostructured-based aptasensors, which show a substantial improvement of the analytical performances.

Gold and Magnetic Nanoparticles-Based Electrochemical Biosensors for Cancer Biomarker Determination

Detecting cancer at early stage is one of the most important factors associated with the increase of the survival rate of the patients. Cancer biomarkers are able to detect a specific disease early and help to provide treatments before it becomes incurable in later stages. Biomarkers can also be used to determine the recurrence of the disease and to evaluate the follow-up of the patients after a chemio- or radio-therapy and surgery treatments. Electrochemical biosensors are successfully applied for the detection of cancer biomarkers due to their high sensibility, rapid response and low cost. In recent years, the advance in nanotechnology has led to the discovery and the employment of a great number of new materials in nanoscale dimensions. Due to their particular properties, the development of nanostructured biosensors (in particular using gold and magnetic nanoparticles) with high analytical performances increases constantly. In this review recent different strategies for the development of gold and magnetic nanoparticles-based electrochemical biosensors for cancer biomarkers detection were presented.

A DNA Aptasensor for Electrochemical Detection of Vascular Endothelial Growth Factor

Electrochemical aptasensors can detect different cancer biomarkers to provide point-of-care diagnosis that is low cost, rapid, specific and sensitive. In this work, we described the development of an electrochemical single-use aptasensor for detection and analysis of vascular endothelial growth factor (VEGF). Gold nanostructured graphite screen-printed electrodes were firstly modified with a mixed monolayer of a primary thiolated DNA aptamer and a spacer thiol, 6-mercapto-1-hexanol. VEGF protein was then incubated with the aptasensor. An enzyme-amplified detection scheme, based on the coupling of a streptavidin-alkaline phosphatase conjugate and secondary biotinylated aptamer was then applied. The enzyme catalyzed the hydrolysis of the electroinactive 1 -naphthyl-phosphate to 1 -naphthol; this product is electroactive and has been detected by means of differential pulse voltammetry (DPV). The aptasensor response was found to be linearly related to the target concentration between 0 and 250 nmol L(-1); the detection limit was 30 nmol L(-1). The performance of the immunoassay in terms of reproducibility and selectivity has been also studied.

In vitro assessment of antibody-conjugated gold nanorods for systemic injections

BACKGROUND

The interest for gold nanorods in biomedical optics is driven by their intense absorbance of near infrared light, their biocompatibility and their potential to reach tumors after systemic administration. Examples of applications include the photoacoustic imaging and the photothermal ablation of cancer. In spite of great current efforts, the selective delivery of gold nanorods to tumors through the bloodstream remains a formidable challenge. Their bio-conjugation with targeting units, and in particular with antibodies, is perceived as a hopeful solution, but the complexity of living organisms complicates the identification of possible obstacles along the way to tumors.

RESULTS

Here, we present a new model of gold nanorods conjugated with anti-cancer antigen 125 (CA125) antibodies, which exhibit high specificity for ovarian cancer cells. We implement a battery of tests in vitro, in order to simulate major nuisances and predict the feasibility of these particles for intravenous injections. We show that parameters like the competition of free CA125 in the bloodstream, which could saturate the probe before arriving at the tumors, the matrix effect and the interference with erythrocytes and phagocytes are uncritical.

CONCLUSIONS

Although some deterioration is detectable, anti-CA125-conjugated gold nanorods retain their functional features after interaction with blood tissue and so represent a powerful candidate to hit ovarian cancer cells.

Electrochemical detection of miRNA-222 by use of a magnetic bead-based bioassay

MicroRNAs (miRNAs, miRs) are naturally occurring small RNAs (approximately 22 nucleotides in length) that have critical functions in a variety of biological processes, including tumorigenesis. They are an important target for detection technology for future medical diagnostics. In this paper we report an electrochemical method for miRNA detection based on paramagnetic beads and enzyme amplification. In particular, miR 222 was chosen as model sequence, because of its involvement in brain, lung, and liver cancers. The proposed bioassay is based on biotinylated DNA capture probes immobilized on streptavidin-coated paramagnetic beads. Total RNA was extracted from the cell sample, enriched for small RNA, biotinylated, and then hybridized with the capture probe on the beads. The beads were then incubated with streptavidin-alkaline phosphatase and exposed to the appropriate enzymatic substrate. The product of the enzymatic reaction was electrochemically monitored. The assay was finally tested with a compact microfluidic device which enables multiplexed analysis of eight different samples with a detection limit of 7 pmol L(-1) and RSD = 15 %. RNA samples from non-small-cell lung cancer and glioblastoma cell lines were also analyzed.