Development of a real-time capacitive biosensor for cyclic cyanotoxic peptides based on Adda-specific antibodies

Environmental monitoring tools and strategies in salmon net-pen aquaculture

As global salmon production accelerates in response to higher consumer demand for seafood, so does the need for sophisticated monitoring strategies to enable and maintain ethically sound, productive, and environmentally friendly production of fish. Innovative technologies are needed to ensure proper water quality, react to unfavorable hydrodynamic conditions, monitor for changes in fish health, and minimize ecological interactions with indigenous aquatic life, including fish escapes. Automated sensors connected wirelessly to data stations, visualization aids, and acoustic and physical tagging technologies are emerging tools capable of detecting environmental stress and its associated behavioral changes in farmed fish. Computer modeling of the monitoring data collected from a single salmon farm or collection of farms sharing a data network can be used to spot environmental trends vital for anticipating some of the consequences of climate change. Environmental regulations governing salmon farming in coastal areas are becoming more stringent in response to public pressures to protect coastal and ocean resources and to provide for multipurpose use of marine resources. As net-pen salmon aquaculture expands globally, new technologies will be essential to collect and interpret the anticipated larger volumes of data needed to meet these stringent regulatory requirements and to safeguard the high investment costs inherent in salmon farming. Integr Environ Assess Manag 2022;18:950-963. © SETAC.

Biosensing of microcystins in water samples; recent advances

Safety and quality of water are significant matters for agriculture, animals and human health. Microcystins, as secondary metabolite of cyanobacteria (blue-green algae) and cyclic heptapeptide cyanotoxin, are one of the main marine toxins in continental aquatic ecosystems. More than 100 microcystins have been identified, of which MC-LR is the most important type due to its high toxicity and common detection in the environment. Climate change is an impressive factor with effects on cyanobacterial blooms as source of microcystins. The presence of this cyanotoxin in freshwater, drinking water, water reservoir supplies and food (vegetable, fish and shellfish) has created a common phenomenon in eutrophic freshwater ecosystems worldwide. International public health organizations have categorized microcystins as a kind of neurotoxin and carcinogen. There are several conventional methods for detection of microcystins. The limitations of traditional methods have encouraged the development of innovative methods for detection of microcystins. In recent years, the developed sensor techniques, with advantages, such as accuracy, reproducibility, portability and low cost, have attracted considerable attention. This review compares the well-known of biosensor types for detection of microcystins with a summary of their analytical performance.

Sensors, Biosensors, and Analytical Technologies for Aquaculture Water Quality

In aquaculture industry, fish, shellfish, and aquatic plants are cultivated in fresh, salt, or brackish waters. The increasing demand of aquatic products has stimulated the rapid growth of aquaculture industries. How to effectively monitor and control water quality is one of the key concerns for aquaculture industry to ensure high productivity and high quality. There are four major categories of water quality concerns that affect aquaculture cultivations, namely, (1) physical parameters, e.g., pH, temperature, dissolved oxygen, and salinity, (2) organic contaminants, (3) biochemical hazards, e.g., cyanotoxins, and (4) biological contaminants, i.e., pathogens. While the physical parameters are affected by climate changes, the latter three are considered as environmental factors. In this review, we provide a comprehensive summary of sensors, biosensors, and analytical technologies available for monitoring aquaculture water quality. They include low-cost commercial sensors and sensor network setups for physical parameters. They also include chromatography, mass spectrometry, biochemistry, and molecular methods (e.g., immunoassays and polymerase chain reaction assays), culture-based method, and biophysical technologies (e.g., biosensors and nanosensors) for environmental contamination factors. According to the different levels of sophistication of various analytical techniques and the information they can provide (either fine fingerprint, highly accurate quantification, semiquantification, qualitative detection, or fast screening), we will comment on how they may be used as complementary tools, as well as their potential and gaps toward current demand of real-time, online, and/or onsite detection.

Capacitive Sensor to Monitor Enzyme Activity by Following Degradation of Macromolecules in Real Time

A capacitive sensor was developed to analyze the presence and enzymatic activity of a model protease from standard solutions by following the degradation of the substrate in real time. The enzyme was chosen based on its specific digestion of the hinge region of immunoglobulin G (IgG). Real-time enzyme activity was monitored by measuring the change in capacitance (∆C) based on the release of IgG fragments after enzymatic digestion by the enzyme. The results indicated that the developed capacitive system might be used successfully for label-free and real-time monitoring of enzymatic activity of different enzymes in a sensitive, rapid, and inexpensive manner in biotechnological, environmental, and clinical applications.

The end user sensor tree: An end-user friendly sensor database

Detailed knowledge regarding sensor based technologies for the detection of food contamination often remains concealed within scientific journals or divided between numerous commercial kits which prevents optimal connectivity between companies and end-users. To overcome this barrier The End user Sensor Tree (TEST) has been developed. TEST is a comprehensive, interactive platform including over 900 sensor based methods, retrieved from the scientific literature and commercial market, for aquatic-toxins, mycotoxins, pesticides and microorganism detection. Key analytical parameters are recorded in excel files while a novel classification system is used which provides, tailor-made, experts' feedback using an online decision tree and database introduced here. Additionally, a critical comparison of reviewed sensors is presented alongside a global perspective on research pioneers and commercially available products. The lack of commercial uptake of the academically popular electrochemical and nanomaterial based sensors, as well as multiplexing platforms became very apparent and reasons for this anomaly are discussed.

Highly sensitive detection and quantification of the secreted bacterial benevolence factor RoxP using a capacitive biosensor: A possible early detection system for oxidative skin diseases

The impact of the microbiota on our health is rapidly gaining interest. While several bacteria have been associated with disease, and others being indicated as having a probiotic effect, the individual biomolecules behind these alterations are often not known. A major problem in the study of these factors in vivo is their low abundance in complex environments. We recently identified the first secreted bacterial antioxidant protein, RoxP, from the skin commensal Propionibacterium acnes, suggesting its relevance for maintaining the redox homeostasis on the skin. In order to study the effect, and prevalence, of RoxP in vivo, a capacitive biosensor with a recognition surface based on molecular imprinting was used to detect RoxP on skin in vivo. In vitro analyses demonstrated the ability to detect and quantify RoxP in a concentration range of 1 x 10⁻¹³ M to 1 x 10⁻⁸ M from human skin swabs; with a limit of detection of 2.5 x 10⁻¹⁹ M in buffer systems. Further, the biosensor was highly selective, not responding to any other secreted protein from P. acnes. Thus, it was possible to demonstrate the presence, and quantity, of RoxP on human skin. Therefore, the developed biosensor is a very promising tool for the detection of RoxP from clinical samples, offering a rapid, cost-effective and sensitive means of detecting low-abundant bacterial proteins in vivo in complex milieus.

Electrochemical Flow-ELISA for Rapid and Sensitive Determination of Microcystin-LR Using Automated Sequential Injection System

An amperometric immunoanalysis system based on monoclonal antibodies immobilized on Sepharose beads and packed into a micro-immunocolumn was developed for the quantification of microcystin-LR. Microcystin-LR (MCLR) was used as a reference microcystin variant. Inside the immunocolumn, free microcystins and microcystin-horseradish peroxidase (tracer) were sequentially captured by the immobilized antibodies, and the detection was performed electrochemically using Super AquaBlue ELISA substrate 2,2'-azinobis(3-ethylbenzothiazoline-sulfonic acid) (ABTS). The ABTS^●+ generated by enzymatic oxidation of ABTS was electrochemically determined at a carbon working electrode by applying a reduction potential set at 0.4 V versus Ag/AgCl reference electrode. The peak current intensity was inversely proportional to the amount of analyte bound to the immunocolumn. The amperometric flow-ELISA system, which was automatically controlled through the CapSenze^TM (Lund, Sweden) computer software, enabled determination of MCLR as low as 0.01 µg/L. The assay time was very short (20 min for one assay cycle). In addition, the electrochemical signals were not significantly affected by possible interferences which could be present in the real samples. Along with the simplicity of automation, this makes the developed method a promising tool for use in water quality assessment.

Capacitive Biosensors and Molecularly Imprinted Electrodes

Capacitive biosensors belong to the group of affinity biosensors that operate by registering direct binding between the sensor surface and the target molecule. This type of biosensors measures the changes in dielectric properties and/or thickness of the dielectric layer at the electrolyte/electrode interface. Capacitive biosensors have so far been successfully used for detection of proteins, nucleotides, heavy metals, saccharides, small organic molecules and microbial cells. In recent years, the microcontact imprinting method has been used to create very sensitive and selective biorecognition cavities on surfaces of capacitive electrodes. This chapter summarizes the principle and different applications of capacitive biosensors with an emphasis on microcontact imprinting method with its recent capacitive biosensor applications.

Screening of self-assembled monolayer for aflatoxin B1 detection using immune-capacitive sensor

A capacitive biosensor was used for detection of aflatoxin B1. Two different methods for cleaning gold electrodes were evaluated using cyclic voltammetry in the presence of ferricyanide as redox couple. The methods involve use of a sequence of cleaning steps avoiding the use of Piranha solution and plasma cleaner. Anti-aflatoxin B1 was immobilized on self-assembled monolayers (SAM). The immune-capacitive biosensor is able to detect aflatoxin B1 concentrations in a linear range of 3.2 × 10⁻¹² M to 3.2 × 10⁻⁹ M when thiourea was used to form the SAM; 3.2 × 10⁻⁹ M to 3.2 × 10⁻⁷ M when thioctic acid was used. When the gold surface was isolated with tyramine-electropolymerization linear ranges of 3.2 × 10⁻¹³ M to 3.2 × 10⁻⁷ M and 3.2 × 10⁻⁹ M to 3.2 × 10⁻⁷ M where obtained, respectively. The results obtained show the difference in linear range, limit of detection, and limit of quantification when different self-assembled monolayers are used for aflatoxin B1 detection.