Magnetic particles–based biosensor for biogenic amines using an optical oxygen sensor as a transducer

Gold-Nanoparticle-Coated Magnetic Beads for ALP-Enzyme-Based Electrochemical Immunosensing in Human Plasma

A simple and sensitive AuNP-coated magnetic beads (AMB)-based electrochemical biosensor platform was fabricated for bioassay. In this study, AuNP-conjugated magnetic particles were successfully prepared using biotin-streptavidin conjugation. The morphology and structure of the nanocomplex were characterized by scanning electron microscopy (SEM) with energy-dispersive X-ray analysis (EDX) and UV-visible spectroscopy. Moreover, cyclic voltammetry (CV) was used to investigate the effect of AuNP-MB on alkaline phosphatase (ALP) for electrochemical signal enhancement. An ALP-based electrochemical (EC) immunoassay was performed on the developed AuNP-MB complex with indium tin oxide (ITO) electrodes. Subsequently, the concentration of capture antibodies was well-optimized on the AMB complex via biotin-avidin conjugation. Lastly, the developed AuNP-MB immunoassay platform was verified with extracellular vesicle (EV) detection via immune response by showing the existence of EGFR proteins on glioblastoma multiforme (GBM)-derived EVs (10⁸ particle/mL) spiked in human plasma. Therefore, the signal-enhanced ALP-based EC biosensor on AuNP-MB was favorably utilized as an immunoassay platform, revealing the potential application of biosensors in immunoassays in biological environments.

Biosensors for Biogenic Amines: A Review

Biogenic amines (BAs) are well-known biomolecules, mostly for their toxic and carcinogenic effects. Commonly, they are used as an indicator of quality preservation in food and beverages since their presence in higher concentrations is associated with poor quality. With respect to BA’s metabolic pathways, time plays a crucial factor in their formation. They are mainly formed by microbial decarboxylation of amino acids, which is closely related to food deterioration, therefore, making them unfit for human consumption. Pathogenic microorganisms grow in food without any noticeable change in odor, appearance, or taste, thus, they can reach toxic concentrations. The present review provides an overview of the most recent literature on BAs with special emphasis on food matrixes, including a description of the typical BA assay formats, along with its general structure, according to the biorecognition elements used (enzymes, nucleic acids, whole cells, and antibodies). The extensive and significant amount of research that has been done to the investigation of biorecognition elements, transducers, and their integration in biosensors, over the years has been reviewed.

Fluorescent nanoprobe array based on carbon nanodots for qualitative and quantitative determination of biogenic polyamine

A nanoprobe array based on fluorescent nitrogen-rich carbon dots (N-CDs) and Ag⁺ was constructed for simultaneous qualitative and quantitative determination of seven kinds of biogenic polyamines (BAs), including tryptamine (Try), histamine (His), putrescine (Put), cadaverine (Cad), spermine (Spm), spermidine (Spd), and agmatine (Agm). Ag⁺ can specifically bind to the N-CDs and quench the fluorescence of the N-CDs through a static mechanism. BAs further statically quench the fluorescence of the N-CD@Ag⁺ composite by bridging two Ag⁺ centers of the N-CD@Ag⁺. The nanoprobe array was constructed based on the differential fluorescence response arising from the differential binding affinity of various BAs. BAs can be differentiated and analyzed by the nanoprobe array within the concentration range 0.5-500 μM. The preliminary diluted and artificially spiked commercial human serum was utilized to simulate the serum environment for assessing the performance of the nanoprobe array in real samples. The N-CD@Ag⁺ system can recognize BAs with 100% accuracy in simulated human serum samples. The quantitative determination of BAs - no matter in a one-component system or a three-component system - was also realized by using the N-CD@Ag⁺ system even in the simulated serum environment. The recovery rates from spiked serum samples were higher 99%, and the relative standard deviation (RSD) was less than 3%. Based on the excellent multi-BA determination performance, a BA-related disease model about cerebral ischemia was constructed. Healthy cases as well as mild, moderate, and severe cerebral ischemia cases can be well identified from the disease model based on the N-CD@Ag⁺ nanoprobe array. Schematic representation of fluorescent nanoprobe array constructed by carbon nanodots (N-CDs) and Ag⁺ for qualitative and quantitative analyses of biogenic polyamines (BAs) and diagnosis of cerebral ischemia (CI) through linear discriminant analysis (LDA) and support vector machine (SVM).

Optical sensors for determination of biogenic amines in food

This review presents the state-of-the-art of optical sensors for determination of biogenic amines (BAs) in food by publications covering about the last 10 years. Interest in the development of rapid and preferably on-site methods for quantification of BAs is based on their important role in implementation and regulation of various physiological processes. At the same time, BAs can develop in different kinds of food by fermentation processes or microbial activity or arise due to contamination, which induces toxicological risks and food poisoning and causes serious health issues. Therefore, various optical chemosensor systems have been devised that are easy to assemble and fast responding and low-cost analytical tools. If amenable to on-site analysis, they are an attractive alternative to existing instrumental analytical methods used for BA determination in food. Hence, also portable sensor systems or dipstick sensors are described based on various probes that typically enable signal readouts such as photometry, reflectometry, luminescence, surface-enhanced Raman spectroscopy, or ellipsometry. The quantification of BAs in real food samples and the design of the sensors are highlighted and the analytical figures of merit are compared. Future instrumental trends for BA sensing point to the use of cell phone-based fully automated optical evaluation and devices that could even comprise microfluidic micro total analysis systems.

Zinc(II) salphen complex-based fluorescence optical sensor for biogenic amine detection

Biogenic amines have attracted interest among researchers because of their importance as biomarkers in determining the quality of food freshness in the food industry. A rapid and simple technique that is able to detect biogenic amines is needed. In this work, a new optical sensing material for one of the biogenic amines, histamine, based on a new zinc(II) salphen complex was developed. The binding of zinc(II) complexes without an electron-withdrawing group (complex 1) and with electron-withdrawing groups (F, complex 2; Cl, complex 3) to histamine resulted in enhancement of fluorescence. All complexes exhibited high affinity for histamine [binding constant of (7.14 ± 0.80) × 10⁴, (3.33 ± 0.03) × 10⁵, and (2.35 ± 0.14) × 10⁵ M^-1, respectively]. Complex 2 was chosen as the sensing material for further development of an optical sensor for biogenic amines in the following step since it displayed enhanced optical properties in comparison with complexes 1 and 3. The optical sensor for biogenic amines used silica microparticles as the immobilisation support and histamine as the analyte. The optical sensor had a limit of detection for histamine of 4.4 × 10^-12 M, with a linear working range between 1.0 × 10^-11 and 1.0 × 10^-6 M (R² = 0.9844). The sensor showed good reproducibility, with a low relative standard deviation (5.5 %). In addition, the sensor exhibited good selectivity towards histamine and cadaverine over other amines, such as 1,2-phenylenediamine, triethylamine, and trimethylamine. Recovery and real sample studies suggested that complex 2 could be a promising biogenic amine optical sensing material that can be applied in the food industry, especially in controlling the safety of food for it to remain fresh and healthy for consumption.

A Brief Overview of Medical Fiber Optic Biosensors and Techniques in the Modification for Enhanced Sensing Ability

In this paper, we provide a brief overview of fiber optic biosensors for use in MedTech, specifically to aid in the diagnoses and treatment of those with chronic medical conditions. Fiber optic cables as components of biological sensors make them especially effective in biological systems that may require ultra-sensitive detection of low-frequency signals in hard to reach areas. This systematic review focuses on the differentiating factors of fiber-optic biosensors, which are tailored to apply the sensor to specific health needs. The main components of FOBS (fiber optic biosensors) such as biosensing elements, fiber optic cables, optical element enhancements, transducers, sensing strategies, photodetectors, and signal processing are covered in detail by showcasing the recent developments in modifications to these components. This paper pays particular attention to the alterations made in biosensing elements including pH elements, enzymatic elements, as well as those sensors utilizing antibodies and whole-cell bacteria. This paper reviews and discusses several published examples in the research stage of development to give the reader an overall scope of the field. The need for research on biosensing equipment is increasing, as the number of individuals with chronic diseases and the geriatric population require more effective, accurate, and mobile sensing ability and reduced invasiveness. FOBS offer a sensing solution that is accurate, tailorable to almost any clinical need, has abundant and relatively cheap material requirements, and a well-established technological base in fiber optic technology. This small price tag and large market potential make FOBS a desirable research area.

Simultaneous determination of steroid drugs in the ointment via magnetic solid phase extraction followed by HPLC-UV

The copper-coated iron oxide nanoparticles with core-shell were produced by deposition of a Cu shell on Fe₃O₄ NPs through reduction of Cu²⁺ ions in solution using NaBH₄. Subsequently, the organosulfur compound, bis-(2,4,4-trimethylpentyl)-dithiophosphinic acid (b-TMP-DTPA), was used to form self-assembled monolayer in order to modify sorbent's surface via covalent bonding between Cu and thiol (–SH) terminal groups. The prepared magnetic nanoparticles were characterized by using Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscope (TEM), vibrating sample magnetometer (VSM) and thermo gravimetric analysis (TGA). Then, the application of this new sorbent was investigated to extract the steroid drugs in ointment samples with the aid of ultrasound. An external magnetic field was applied to collect the magnetic nanoparticles (MNPs). The extracted analytes were desorbed using acetonitrile. The obtained extraction solution was analyzed by HPLC-UV. The main affecting factors on the extraction efficiency including pH, sonication time, amount of sorbent, salt concentration, and desorption conditions were optimized in detail. Under the optimum conditions, good linearity was obtained in the range of 2.5–250.0 µg/ L with reasonable linearity (R² > 0.99) and the limits of detection (LODs) ranged between 0.5 and 1.0 µg/L (based on S/N = 3). Repeatability (intra-day precision) based on five replicates and preconcentration factors were calculated to be 3.6%–4.7% and 87–116, respectively. Relative recoveries in ointment samples at two spiked levels of the target analytes were obtained in the range of 90.0%–103.2%. The results illustrated that the Fe₃O₄@Cu@ b-TMP-DTPA NPs have the capability of extraction of steroid drugs from ointment samples.

Developing a sensor layer for the optical detection of amines during food spoilage

A colourimetric sensor layer has been developed for ammonia and biogenic amines. Amine exposure induces a traffic light colour change from green to red. Recognition is performed by a pH indicator dye, covalently immobilised onto cellulose microparticles. The sensor microparticles are embedded into food-grade silicone. Selectivity of the pH indicator dye towards gaseous amine is obtained by complete embedding of the sensor particles within the ion-impermeable silicone. A response time of 1.5h has been achieved, with a reverse response occurring after 20h. This time frame is considered sufficient for spoilage processes. Cytotoxicity studies confirm the layers are non-toxic.

Fluorescence based fiber optic and planar waveguide biosensors. A review

The application of optical biosensors, specifically those that use optical fibers and planar waveguides, has escalated throughout the years in many fields, including environmental analysis, food safety and clinical diagnosis. Fluorescence is, without doubt, the most popular transducer signal used in these devices because of its higher selectivity and sensitivity, but most of all due to its wide versatility. This paper focuses on the working principles and configurations of fluorescence-based fiber optic and planar waveguide biosensors and will review biological recognition elements, sensing schemes, as well as some major and recent applications, published in the last ten years. The main goal is to provide the reader a general overview of a field that requires the joint collaboration of researchers of many different areas, including chemistry, physics, biology, engineering, and material science.

Synthesis, Characterization and in Vitro Evaluation of Manganese Ferrite (MnFe2O4) Nanoparticles for Their Biocompatibility with Murine Breast Cancer Cells (4T1)

Manganese ferrite (MnFe₂O₄) magnetic nanoparticles were successfully prepared by a sol-gel self-combustion technique using iron nitrate and manganese nitrate, followed by calcination at 150 °C for 24 h. Calcined sample was systematically characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and vibrational sample magnetometry (VSM) in order to identify the crystalline phase, functional group, morphology, particle size, shape and magnetic behavior. It was observed that the resultant spinal ferrites obtained at low temperature exhibit single phase, nanoparticle size and good magnetic behavior. The study results have revealed the existence of a potent dose dependent cytotoxic effect of MnFe₂O₄ nanoparticles against 4T1 cell lines at varying concentrations with IC₅₀ values of 210, 198 and 171 μg/mL after 24 h, 48 h and 72 h of incubation, respectively. Cells exposed to higher concentrations of nanoparticles showed a progressive increase of apoptotic and necrotic activity. Below 125 μg/mL concentration the nanoparticles were biocompatible with 4T1 cells.

Effect of spermidine and its metabolites on the activity of pea seedlings diamine oxidase and the problems of biosensing of biogenic amines with this enzyme

Spermidine is one of the several biogenic amines, produced during the microbial decarboxylation of proteins. Individual biogenic amines in the formed mixtures are frequently analyzed with oxygen sensor based biosensors, as their content serves as a good biomarker for the determination of food quality. In these biosensors, diamine oxidase from pea seedlings (PSAO), catalyzing the oxidation of various biogenic amines by dissolved oxygen is commonly used for the bio-recognition of amines. However, in the presence of spermidine and/or its metabolite 1,3-diaminopropane, the activity of PSAO and the sensitivity of PSAO-based biosensors decrease due to inhibition. The inhibition constant of soluble spermidine, acting as an inhibiting substrate toward PSAO, was found to be (40±15) mM in freshly prepared solution and (0.28±0.05) mM in solution, incubated 30 days at room temperature. The inhibition constant of 1,3-diaminopropane, acting as a competitive inhibitor, was (0.43±0.12) mM as determined through the oxidation reaction of cadaverine. The metabolic half-life of soluble spermidine was 7 days at room temperature and 186 days at 4 °C. The kinetic measurements were carried out with an oxygen sensor; the composition of the solution of degraded spermidine was analyzed with MS.

Fiber-Optic Chemical Sensors and Fiber-Optic Bio-Sensors

This review summarizes principles and current stage of development of fiber-optic chemical sensors (FOCS) and biosensors (FOBS). Fiber optic sensor (FOS) systems use the ability of optical fibers (OF) to guide the light in the spectral range from ultraviolet (UV) (180 nm) up to middle infrared (IR) (10 μm) and modulation of guided light by the parameters of the surrounding environment of the OF core. The introduction of OF in the sensor systems has brought advantages such as measurement in flammable and explosive environments, immunity to electrical noises, miniaturization, geometrical flexibility, measurement of small sample volumes, remote sensing in inaccessible sites or harsh environments and multi-sensing. The review comprises briefly the theory of OF elaborated for sensors, techniques of fabrications and analytical results reached with fiber-optic chemical and biological sensors.

Smart packaging systems for food applications: a review

Changes in consumer preference for safe food have led to innovations in packaging technologies. This article reviews about different smart packaging systems and their applications in food packaging, packaging research with latest innovations. Active and intelligent packing are such packaging technologies which offer to deliver safer and quality products. Active packaging refers to the incorporation of additives into the package with the aim of maintaining or extending the product quality and shelf life. The intelligent systems are those that monitor the condition of packaged food to give information regarding the quality of the packaged food during transportation and storage. These technologies are designed to the increasing demand for safer foods with better shelf life. The market for active and intelligent packaging systems is expected to have a promising future by their integration into packaging materials or systems.

Aluminium hydroxide stabilised MnFe2O4 and Fe3O4 nanoparticles as dual-modality contrasts agent for MRI and PET imaging

Magnetic nanoparticles (NPs) MnFe2O4 and Fe3O4 were stabilised by depositing an Al(OH)3 layer via a hydrolysis process. The particles displayed excellent colloidal stability in water and a high affinity to [(18)F]-fluoride and bisphosphonate groups. A high radiolabeling efficiency, 97% for (18)F-fluoride and 100% for (64)Cu-bisphosphonate conjugate, was achieved by simply incubating NPs with radioactivity solution at room temperature for 5 min. The properties of particles were strongly dependant on the thickness and hardness of the Al(OH)3 layer which could in turn be controlled by the hydrolysis method. The application of these Al(OH)3 coated magnetic NPs in molecular imaging has been further explored. The results demonstrated that these NPs are potential candidates as dual modal probes for MR and PET. In vivo PET imaging showed a slow release of (18)F from NPs, but no sign of efflux of (64)Cu.

Optical methods for sensing and imaging oxygen: materials, spectroscopies and applications

We review the current state of optical methods for sensing oxygen. These have become powerful alternatives to electrochemical detection and in the process of replacing the Clark electrode in many fields. The article (with 694 references) is divided into main sections on direct spectroscopic sensing of oxygen, on absorptiometric and luminescent probes, on polymeric matrices and supports, on additives and related materials, on spectroscopic schemes for read-out and imaging, and on sensing formats (such as waveguide sensing, sensor arrays, multiple sensors and nanosensors). We finally discuss future trends and applications and summarize the properties of the most often used indicator probes and polymers. The ESI† (with 385 references) gives a selection of specific applications of such sensors in medicine, biology, marine and geosciences, intracellular sensing, aerodynamics, industry and biotechnology, among others.