Ultrasensitive detection of streptomycin using flow injection analysis-electrochemical quartz crystal nanobalance (FIA-EQCN) biosensor

Photoelectrochemical sensing of isoniazid and streptomycin based on metal Bi-doped BiOI microspheres grown on book-shape layers of Ti3C2 heterostructures

Isoniazid and streptomycin are vital drugs for treating tuberculosis, which are utilized as efficient anti-tuberculosis agents. This paper presents a novel visible-light-driven composite photocatalyst Ti3C2/Bi/BiOI, which was built from Ti3C2 nanosheets and Bi/BiOI microspheres. Photoelectrochemical (PEC) sensors based on Ti3C2/Bi/BiOI were synthesized for isoniazid identification, which showed a linear concentration range of 0.1-125 μM with a detection limit of 0.05 μM (S/N = 3). Moreover, we designed a PEC aptasensors based on aptamer/Ti3C2/Bi/BiOI to detect streptomycin in 0.1 M PBS covering the electron donor isoniazid, because the isoniazid consumes photogenerated holes thus increasing the photocurrent effectively and preventing photogenerated electron-hole pairs from being recombined. Furthermore, PEC aptasensors based on aptamer/Ti3C2/Bi/BiOI were synthesized for streptomycin identification, which exhibited a linear concentration range of 0.01-1000 nM with a detection limit of 2.3 × 10-3 nM (S/N = 3), and are well stable in streptomycin sensing.

Affinity-Based Analysis Methods for the Detection of Aminoglycoside Antibiotic Residues in Animal-Derived Foods: A Review

With the increasingly serious problem of aminoglycoside antibiotic residues, it is imperative to develop rapid, sensitive and efficient detection methods. This article reviews the detection methods of aminoglycoside antibiotics in animal-derived foods, including enzyme-linked immunosorbent assay, fluorescent immunoassay, chemical immunoassay, affinity sensing assay, lateral flow immunochromatography and molecular imprinted immunoassay. After evaluating the performance of these methods, the advantages and disadvantages were analyzed and compared. Furthermore, development prospects and research trends were proposed and summarized. This review can serve as a basis for further research and provide helpful references and new insights for the analysis of aminoglycoside residues. Accordingly, the in-depth investigation and analysis will certainly make great contributions to food safety, public hygiene and human health.

An electrochemical aptasensor for detection of streptomycin based on signal amplification assisted by functionalized gold nanoparticles and hybridization chain reaction

A ratiometric electrochemical aptasensor based on gold nanoparticles (AuNPs) functionalization and hybridization chain reaction (HCR) assisted signal amplification has been for the first time designed for the detection of streptomycin (STR). The double-stranded DNA (dsDNA) formed by the hybridization of ferrocene (Fc)-labeled STR aptamer (Apt) and capture probe (CP) is first immobilized on the gold electrode (GE) surface via Au-S reaction. The specific binding of the target and Apt results in numerous Fc detachment from the sensing interface. Then, the remaining single-stranded CP is combined with AuNPs modified with initiator DNA (iDNA) by auxiliary DNA (aDNA). Among them, the iDNA triggers HCR between two hairpin probes (H1/H2), thus capturing a large number of methylene blue (MB) electrochemical probe, which generates a strong electrochemical signal of MB and a weak electrochemical signal of Fc. Signals are collected by square wave voltammetry (the potential window ranging from -0.5 V to 0.6 V, vs. Ag/AgCl ), and the oxidation peak currents at -0.200 V (MB) and 0.416 V (Fc) are recorded. The use of the ratiometric method has effectively improved the accuracy and reliability of the analysis. The successful application of AuNPs and HCR greatly improves the sensitivity of the sensor, and the detection limit is as low as 0.08 pM. It can sensitively determine STR in the range 0.1 pM to 10 nM. In addition, the designed aptasensor has been successfully applied to the detection of STR in milk and honey samples.

Antibody-receptor bioengineering and its implications in designing bioelectronic devices

Antibodies play a crucial role in the defense mechanism countering pathogens or foreign antigens in eukaryotes. Its potential as an analytical and diagnostic tool has been exploited for over a century. It forms immunocomplexes with a specific antigen, which is the basis of immunoassays and aids in developing potent biosensors. Antibody-based sensors allow for the quick and accurate detection of various analytes. Though classical antibodies have prolonged been used as bioreceptors in biosensors fabrication due to their increased fragility, they have been engineered into more stable fragments with increased exposure of their antigen-binding sites in the recent era. In biosensing, the formats constructed by antibody engineering can enhance the signal since the resistance offered by a conventional antibody is much more than these fragments. Hence, signal amplification can be observed when antibody fragments are utilized as bioreceptors instead of full-length antibodies. We present the first systematic review on engineered antibodies as bioreceptors with the description of their engineering methods. The detection of various target analytes, including small molecules, macromolecules, and cells using antibody-based biosensors, has been discussed. A comparison of the classical polyclonal, monoclonal, and engineered antibodies as bioreceptors to construct highly accurate, sensitive, and specific sensors is also discussed.

Cytochrome c/Multi-walled Carbon Nanotubes Modified Glassy Carbon Electrode for the Detection of Streptomycin in Pharmaceutical Samples

A novel electrochemical glassy carbon electrode modified with a multi-walled carbon nanotube, cytochrome c (Cyt c) and zinc oxide nanoparticles (ZnONPs) was fabricated to increase the sensitivity of electrode for the detection of streptomycin (STN) in certain pharmaceutical samples. Cyclic voltammetry (CV) and differential pulse voltammetry techniques were used for an electrochemical characterization of the electrode. Furthermore, the electrochemical biosensor construction phases were examined by using X-ray diffraction (XRD), transmission electron microscopy (TEM) and Fourier-transform infrared spectroscopy (FTIR). Under the optimal experimental conditions, the electrode offers a high selectivity and sensitivity signaling in the co-existence method of STN with the linear concentration ranging from 0.02 to 2.2 μM. The detection limits (LOD) and limit of quantification (LOQ) were found to be 0.0028 and 0.0562 μM, respectively. The fabricated sensing electrode has good stability, reproducibility and sensitivity towards STN in the pharmaceutical samples. Preliminary determinations of binding sites within the specified grid box size, which covers both Cyt c and STN, were done by molecular docking analysis. Moreover, density functional theory (DFT) computations were performed to provide insightful information into the optimized geometry of STN.

Technological Advancements for the Detection of Antibiotics in Food Products

Antibiotics, nowadays, are not only used for the treatment of human diseases but also used in animal and poultry farming to increase production. Overuse of antibiotics leads to their circulation in the food chain due to unmanaged discharge. These circulating antibiotics and their residues are a major cause of antimicrobial resistance (AMR), so comprehensive and multifaceted measures aligning with the One Health approach are crucial to curb the emergence and dissemination of antibiotic resistance through the food chain. Different chromatographic techniques and capillary electrophoresis (CE) are being widely used for the separation and detection of antibiotics and their residues from food samples. However, the matrix present in food samples interferes with the proper detection of the antibiotics, which are present in trace concentrations. This review is focused on the scientific literature published in the last decade devoted to the detection of antibiotics in food products. Various extraction methods are employed for the enrichment of antibiotics from a wide variety of food samples; however, solid-phase extraction (SPE) techniques are often used for the extraction of antibiotics from food products and biological samples. In addition, this review has scrutinized how changing instrumental composition, organization, and working parameters in the chromatography and CE can greatly impact the identification and quantification of antibiotic residues. This review also summarized recent advancements in other detection methods such as immunological assays, surface-enhanced Raman spectroscopy (SERS)-based assays, and biosensors which have emerged as rapid, sensitive, and selective tools for accurate detection and quantification of traces of antibiotics.

Recent advances in biosensors for antibiotic detection: Selectivity and signal amplification with nanomaterials

Antibiotics are widely used in the prevention and treatment of infectious diseases in animals due to its bactericidal or bacteriostatic action. Residual antibiotics and their metabolites pose great threats to human and animal health, such as potential carcinogenic and mutagenic effects, and bacterial resistances. Therefore, it is necessary and urgent to accurately monitor trace amounts of antibiotics in food samples. Up to now, many analytical methods have been reported for the determination of antibiotics. Biosensors with the advantages of high sensitivity, rapid response, easy miniaturization, and low price have been widely applied to the detection of antibiotics residues in past decades. This review offered an in-depth evaluation of recognition elements for antibiotic residues in diverse food matrices. In addition, it presented a systematical and critical review on signal amplification via various materials, focusing on recently developed nanomaterials. Finally, the review provided an outlook on the future concepts to help upgrade the sensing techniques for antibiotics in food.

Recent Biosensors for Detection of Antibiotics in Animal Derived Food

Antibiotics are extensively employed as bacteriostatic agents for fighting against microbial infection in animals. However, inappropriate doses of antibiotic drugs may result in antibiotic residues in food of animal origin and may cause various side effects on human health. Moreover, the transferor of antibiotic-resistant bacteria to humans through the food chain may induce serious health hazards. Hence, it is vital to develop sensitive and selective methods for rapid screening and regular monitoring of antibiotic residues in animal-derived foods. The conventional different chromatographic and spectroscopic techniques are time-consuming, expensive and require skilled personnel. To overcome such limitations, biosensors have emerged as an innovative approach recently and integrated with nanotechnologies for sensitive, rapid and on-site monitoring of different antibiotic residues in animal origin foods. This mini-review aims to give an overview of the currently available biosensing techniques to detect antibiotic residue in foods.

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2): a global pandemic and treatment strategies

The emergence and rapid spread of coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), a potentially fatal disease, is swiftly leading to public health crises worldwide. The origin of SARS-CoV-2 infection was first reported in people exposed to a seafood market in Wuhan City, China in December 2019. It has been suggested that the infection is likely to be of zoonotic origin and transmitted to humans through a not-yet-known intermediary. As of 22 May 2020, the World Health Organization reported that there were approximately 4,995,996 confirmed cases and 327,821 deaths. SARS-CoV-2 is transmitted via inhalation or direct contact with droplets from infected people. It has an incubation period ranging from 2 to ≥14 days. The rate of spread of SARS-CoV-2 is greater than that for severe acute respiratory syndrome coronavirus and Middle East respiratory coronavirus. The symptoms are similar to influenza (i.e. breathlessness, sore throat and fatigue) and infected cases are isolated and treated. Infection is mild in most cases, but in elderly (>50 years) patients and those with cardiac and respiratory disorders, it may progress to pneumonia, acute respiratory distress syndrome and multi-organ failure. People with strong immunity or those who have developed herd immunity are asymptomatic. The fatality rate ranges from 3% to 4%. Recommended methods for diagnosis of COVID-19 are molecular tests (e.g. polymerase chain reaction) on respiratory secretions, chest scan and common laboratory diagnosis. Currently, treatment is essentially supportive, and the role of antiviral agents is yet to be established as a vaccine is not yet available. This review will focus on epidemiology, symptoms, transmission, pathogenesis, ongoing available treatments and future perspectives of SARS-CoV-2.

Amplified oxygen reduction signal at a Pt-Sn-modified TiO2 nanocomposite on an electrochemical aptasensor

In this work, a metallic composite with strong electrocatalytic property was designed by uniformly decorating Pt and Sn nanoparticles on the surface of TiO₂ nanorods (Pt-Sn@TiO₂). A detection scheme was then developed based on a dual signal amplification strategy involving the Pt-Sn@TiO₂ composite and exonuclease assisted target recycling. The Pt-Sn@TiO₂ composite exhibited an enhanced oxygen reduction current owing to the synergistic effect between Pt and Sn, as well as high exposure of Pt (111) crystal face. Initially, a Pt-Sn@TiO₂ modified glassy carbon electrode produced an amplified electrochemical signal for the reduction of dissolved oxygen in the analyte solution. Next, a DNA with a complementary sequence to a streptomycin aptamer (cDNA) was immobilised on the Pt-Sn@TiO₂ modified electrode, followed by the streptomycin aptamer that hybridised with cDNA. The corresponding oxygen reduction current was diminished by 51% attributable to the hindrance from the biomolecules. After a mixture of streptomycin and RecJ_f exonuclease was introduced, both the streptomycin-aptamer complex and the cDNA were cleaved from the electrode, making the Pt-Sn and Pt (111) surface available for oxygen reduction. RecJ_f would also release streptomycin from the streptomycin-aptamer complex, allowing it to complex again with aptamers on the electrode. This has then promoted a cyclic amplification of the oxygen reduction current by 85%, which is quantitatively related to streptomycin. Under optimal conditions, the aptasensor exhibited a linear range of 0.05-1500 nM and a limit of detection of 0.02±0.0045 nM streptomycin. The sensor was then used in the real-life sample detection of streptomycin to demonstrate its potential applications to bioanalysis.

Antibiotic residues in milk: Past, present, and future

Now-a-days, various types of antibiotics are being used worldwide in veterinary sector indiscriminately for promotion of growth and treatment of the livestock. Significant portions of antibiotics are released through milk of dairy animals unaltered and exert serious harmful effects on human health. This review evaluates and compare researches on antibiotic residues in milk in published literatures from Pubmed, CrossRef, CAB direct, DOAJ, JournalTOCs, AGRICOLA, ScientificGate, Electronic Journals Library, CAB abstracts, Global Health Databases, Global Impact Factor, Google Scholar, Park Directory of Open Access Journals, BanglaJOL and ISC E-Journals. Antibiotics residue in milk was first detected in 60s and then with an increasing trend with highest after 2,000 (188). The highest no. of works, 49 (21.87%) were accomplished in China, followed by Spain, 30 (13.39%); Germany, 11 (4.91%); and USA, 10 (4.46%). Continent-wise highest researches are published from Europe, 105 (46.88%), followed by Asia, 77 (34.38%); South America, 18 (8.04%); North America, 16 (7.14%); and Africa, 8 (3.57%). For detection, Bovine milk sample is mostly used, 193 (86.16%), followed by ovine, 19 (8.48%); and caprine, 14 (6.25%). Acetonitrile was used in maximum cases (77) for processing the samples. Chromatographic technique was the highest, 115 (51.34%) for detection. Residue of β-lactam group have been detected mostly 133 (36.54%), followed by tetracyclines, 51 (14.01%); fluoroquinolones, 49 (13.46%); sulfonamides, 46 (12.64%); and aminoglycosides, 38 (10.44%). This review observe that antibiotics residues are more common in milk samples that are being manifested in increasing researches on antibiotic detection and measures should adopt to cease this residue.

Self-Assembled Microgels for Sensitive and Low-Fouling Detection of Streptomycin in Complex Media

In terms of detection of antibiotics within complex media, the nonspecific adsorption is an enormous challenge and antifouling sensing interfaces capable of reducing the nonspecific adsorption from complex biological samples are highly desirable. In this work, a novel antifouling electrochemical immunosensor was explored based on the self-assembly of two kinds of poly( N-isopropylacrylamide) microgels on the surface of graphene oxide for sensitive detection of streptomycin (STR). The microgels modified with glycidyl methacrylate (GMA) and zwitterionic liquid 1-propyl-3-vinylimidazole sulfonate (PVIS) were prepared. The microgels with GMA were used by combining specific recognition of anti-STR. The rapid specific binding of antigen and anti-STR resulted in a decrease of current density to generate electrochemical responsive signals. Zwitterionic liquid-modified microgels were used for antifouling, which can form stronger hydration and show excellent antifouling ability. As a result, we achieved efficient and sensitive detection of STR in the complex sample with evidently resisted nonspecific adsorption effect, the wide linear range toward STR was from 0.05 to 100 ng mL^-1, with a detection limit down to 1.7 pg mL^-1. The immunosensor based on the surface functionalization of microgels showed promising applications for the detection of antibiotics in complex media.

Selection of DNA aptamers and establishment of an effective aptasensor for highly sensitive detection of cefquinome residues in milk

Cefquinome (CFQ), which is a fourth-generation cephalosporin approved for veterinary use only, has been widely used for treating porcine or bovine respiratory infection, bovine mastitis and other diseases. However, the antibacterial effect of CFQ is based on the duration of drug concentration remaining in excess of the minimum inhibitory concentration in serum or tissues, thereby inevitably leading to CFQ residues with high levels in animal-sourced food. In this paper, four CFQ-specific ssDNA aptamers were selected via a magnetic bead-based systematic evolution of ligands by the exponential enrichment (SELEX) method. Aptamer W1 with the lowest dissociation constant (Kd) value of 40.13 ± 22.11 nM was chosen for establishing a fluorescence aptasensor based on magnetic separation and release of molecular beacons for detection of CFQ residues. This aptasensor exhibited a high sensitivity toward CFQ with a limit of detection (LOD) of 0.09 ng mL-1 (linear range from 0.5 to 150 ng mL-1). Moreover, the present aptasensor also showed high selectivity against ampicillin and CFQ's structural analogs (i.e., cefpirome sulfate and cefixime). Finally, this aptasensor was used to detect CFQ in real spiked milk. The recovery rate of CFQ from spiked milk samples ranged from 96.6% to 103.2%. These results indicated that the developed aptasensor is a promising, highly sensitive and specific method for CFQ residue detection in animal-sourced food.

An electrochemical aptasensor for streptomycin based on covalent attachment of the aptamer onto a mesoporous silica thin film-coated gold electrode

An electrochemical method is described for the determination of streptomycin (STR). It is making use of a gold electrode coated with a thin mesoporous silica film (MSF). In addition, silver nanoparticles were coated on the MSF to increase the surface area, to bind a large amount of aptamer (Apt), and to improve the electrical conductivity. In the presence of STR, it will bind to the Apt and hinder the diffusion of the redox probe hexacyanoferrate through the nanochannels of the mesoporous film. The aptasensor, best operated at a working potential of 0.22 V (vs. Ag/AgCl) has a linear response in the 1 fg.mL^-1 to 6.2 ng.mL^-1 STR concentration range. The detection limit is 0.33 fg.mL^-1. The assay was successfully validated by analyzing spiked samples of milk and blood serum. Graphical abstract Voltammetric assay of streptomycin (STR) by using a Fe(CN)₆^3-/4- probe. The aptamer was immobilized on a gold electrode modified with a mesoporous silica thin film (MSF) that was functionalized with (3-aminopropyl) triethoxysilane (APTES) and silver nanoparticles (AgNP). Incubation with STR leads to a decrease of the current.

Recent progress on cell-based biosensors for analysis of food safety and quality control

Food quality and safety has become a subject of major concern for authorities and professionals in the food supply chain. Rapid methods, particularly biosensors, have exceptional specificity and sensitivity, rapid response times, low cost, relatively compact size, and are user friendly to operate. Cell-based biosensors are portable, and provide the biological activity of the analyte suitable for an initial screening of food. In this overview, the utilization of cell-based biosensors for food safety and quality analyses, such as detecting toxins, foodborne pathogens, allergens, and evaluating toxicity and function are summarized. Our results will promote the future development of cell-based biosensors in the food field.

Multiplexed aptasensor based on metal ions labels for simultaneous detection of multiple antibiotic residues in milk

A dual-target electrochemical aptasensor was developed for the simultaneous detection of multiple antibiotics based on metal ions as signal tracers and nanocomposites as signal amplification strategy. Metal ions such as Cd²⁺ and Pb²⁺ could generate distinct differential pulse voltammetry (DPV) peaks. When targets were present, kanamycin (KAN) and streptomycin (STR) as models, the KAN aptamer (KAP) and STR aptamer (STP) were released from their complementary strands, with more change of Cd²⁺ and Pb²⁺ corresponding to peak currents. At the same time, complementary strand of KAP (cKAP) and STP (cSTP) were linked with the poly (A) structure (cSTP-PolyA-cKAP) to increase their conformational freedom. Graphitized multi-walled carbon nanotubes (MWCNT_Gr) and carbon nanofibers-gold nanoparticles (CNFs-AuNPs) as a biosensor platform enhanced the surface area to capture a large amount of cSTP-PolyA-cKAP, thus amplifying the detection response. Under the optimal conditions, the aptasensor could detect KAN and STR as low as 74.50 pM and 36.45 pM respectively with the range from 0.1 to 100 nM and exhibited excellent selectively. Moreover, this aptasensor showed promising applications for the detection of other analytes by changing corresponding aptamers.

Electrochemical Aptasensors for Food and Environmental Safeguarding: A Review

Food and environmental monitoring is one of the most important aspects of dealing with recent threats to human well-being and ecosystems. In this framework, electrochemical aptamer-based sensors are resilient due to their ability to resolve food and environmental contamination. An aptamer-based sensor is a compact analytical device combining an aptamer as the bio-sensing element integrated on the transducer surface. Aptamers display many advantages as biorecognition elements in sensor development when compared to affinity-based (antibodies) sensors. Aptasensors are small, chemically unchanging, and inexpensive. Moreover, they offer extraordinary elasticity and expediency in the design of their assemblies, which has led to innovative sensors that show tremendous sensitivity and selectivity. This review will emphasize recent food and environmental safeguarding using aptasensors; there are good prospects for their performance as a supplement to classical techniques.

Amplified detection of streptomycin using aptamer-conjugated palladium nanoparticles decorated on chitosan-carbon nanotube

A streptomycin-specific aptamer was used as a receptor molecule for ultrasensitive quantitation of streptomycin. The glassy carbon (GC) electrode was modified with palladium nanoparticles decorated on chitosan-carbon nanotube (PdNPs/CNT/Chi) and aminated aptamer against streptomycin. Modification of the sensing interface was characterized by scanning electron microscopy (SEM), energy-dispersive X-ray (EDS), wavelength-dispersive X-ray spectroscopy (WDX), cyclic voltammetry (CVs), and electrochemical impedance spectroscopy (EIS). The methodologies applied for designing the proposed biosensor are based on target-induced conformational changes of streptomycin-specific aptamer, leading to detectable signal change. Sensing experiments were performed in the streptomycin concentration range from 0.1 to 1500 nM in order to evaluate the sensor response as a function of streptomycin concentration. Based on the results, the charge transfer resistance (R_ct) values increased proportionally to enhanced streptomycin content. The limit of detection was found to be as low as 18 pM. The superior selectivity and affinity of aptamer/PdNPs/CNT/Chi modified electrode for streptomycin recognition made it favorable for versatile applications such as streptomycin analysis in real samples.

A novel electrochemical aptasensor for highly sensitive and quantitative detection of the streptomycin antibiotic

In the present study, we report a facile approach to employ gold nanoparticle (AuNPs) and thiol graphene quantum dots (GQD-SH) as the nanomaterial for ultrasensitive detection of streptomycin (STR). Based on this strategy, a GQD-SH was immobilized onto the surface of a glassy carbon electrode (GCE). AuNPs have been immobilized on SH groups of GQDs through bonding formation of AuS and Apt have been loaded on the electrode surface through the interaction between thiol group of aptamer. By incubating STR as a target onto the surface of the prepared Apt/AuNPs/GQD-SH/GCE as a proposed nanoaptasensor, the Apt/STR complex was formed and the changes of the electrochemical signal were evaluated with the EIS technique. The proposed nanoaptasensor showed wide linear range from 0.1 to 700pgml^-1. Finally, the proposed nanoaptasensor was successfully applied for the determination of STR in real samples and satisfactory results were obtained.

Point-of-care testing for streptomycin based on aptamer recognizing and digital image colorimetry by smartphone

The rapid detection of antibiotic residual in everyday life is very important for food safety. In order to realize the on-site and visual detection of antibiotic, a POCT method was established by using digital image colorimetry based on smartphone. Streptomycin was taken as the analyte model of antibiotics, streptomycin aptamer preferentially recognized analyte, and the excess aptamer hybridized with the complementary DNA to form the dsDNA. SYBR Green I combined with the dsDNA and then emitted obvious green fluorescence, thus the fluorescence intensity decreased with the increasing of streptomycin concentration. Then a smartphone-based device was constructed as the fluorescence readout. The smartphone camera acquired the images of the fluorescence derived from the samples, and the Touch Color APP installed in smartphone read out the RGB values of the images. There was a linear relationship between the G values and the streptomycin concentrations in the range of 0.1-100µM. The detection limit was 94nM, which was lower than the maximum residue limit defined by World Health Organization. The POCT method was applied for determining streptomycin in chicken and milk samples with recoveries in 94.1-110%. This method had the advantages of good selectivity, simple operation and on-site visualization.

New methodologies in screening of antibiotic residues in animal-derived foods: Biosensors

Antibiotics are leading medicine asset for fighting against microbial infection, but also one of the important causes of death worldwide. Many antibiotics used as therapeutics and growth promotion agents in animals can lead to antibiotic residues in animal-derived food which harm the health of people. Hence, it is vital to screen antibiotic residues in animal derived foods. Typical methods for screening antibiotic residues are based on microbiological growth inhibition and immunological analyses. However these two methods have some disadvantages, such as poor sensitive, lack of specificity and etc. Therefore, it is necessary to develop simple, more efficient and high sensitive screening methods of antibiotic residues. These assays have been introduced for the screening of numerous food samples. Biosensors are emerging methods, applied in screening antibiotic residues in animal-derived foods. Two types of biosensors, whole-cell based biosensors and surface plasmon resonance-based sensors have been extensively used. Their advantages include portability, small sample requirement, high sensitivity and good specificity over the traditional screening methods.

Electrochemical Quartz Crystal Nanobalance (EQCN) Based Biosensor for Sensitive Detection of Antibiotic Residues in Milk

An electrochemical quartz crystal nanobalance (EQCN), which provides real-time analysis of dynamic surface events, is a valuable tool for analyzing biomolecular interactions. EQCN biosensors are based on mass-sensitive measurements that can detect small mass changes caused by chemical binding to small piezoelectric crystals. Among the various biosensors, the piezoelectric biosensor is considered one of the most sensitive analytical techniques, capable of detecting antigens at picogram levels. EQCN is an effective monitoring technique for regulation of the antibiotics below the maximum residual limit (MRL). The analysis of antibiotic residues requires high sensitivity, rapidity, reliability and cost effectiveness. For analytical purposes the general approach is to take advantage of the piezoelectric effect by immobilizing a biosensing layer on top of the piezoelectric crystal. The sensing layer usually comprises a biological material such as an antibody, enzymes, or aptamers having high specificity and selectivity for the target molecule to be detected. The biosensing layer is usually functionalized using surface chemistry modifications. When these bio-functionalized quartz crystals are exposed to a particular substance of interest (e.g., a substrate, inhibitor, antigen or protein), binding interaction occurs. This causes a frequency or mass change that can be used to determine the amount of material interacted or bound. EQCN biosensors can easily be automated by using a flow injection analysis (FIA) setup coupled through automated pumps and injection valves. Such FIA-EQCN biosensors have great potential for the detection of different analytes such as antibiotic residues in various matrices such as water, waste water, and milk.

Development of a Nafion/MWCNT-SPCE-Based Portable Sensor for the Voltammetric Analysis of the Anti-Tuberculosis Drug Ethambutol

Herein we describe the development, characterization and application of an electrochemical sensor based on the use of Nafion/MWCNT-modified screen-printed carbon electrodes (SPCEs) for the voltammetric detection of the anti-tuberculosis (anti-TB) drug ethambutol (ETB). The electrochemical behaviour of the drug at the surface of the developed Nafion/MWCNT-SPCEs was studied through cyclic voltammetry (CV) and square wave voltammetry (SWV) techniques. Electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) were employed to characterize the modified surface of the electrodes. Results showed that, compared to both unmodified and MWCNTs-modified SPCEs, negatively charged Nafion/MWCNT-SPCEs remarkably enhanced the electrochemical sensitivity and selectivity for ETB due to the synergistic effect of the electrostatic interaction between cationic ETB molecules and negatively charged Nafion polymer and the inherent electrocatalytic properties of both MWCNTs and Nafion. Nafion/MWCNT-SPCEs provided excellent biocompatibility, good electrical conductivity, low electrochemical interferences and a high signal-to-noise ratio, providing excellent performance towards ETB quantification in microvolumes of human urine and human blood serum samples. The outcomes of this paper confirm that the Nafion/MWCNT-SPCE-based device could be a potential candidate for the development of a low-cost, yet reliable and efficient electrochemical portable sensor for the low-level detection of this antimycobacterial drug in biological samples.

Recent advances in flow injection analysis

A dynamic development of methodologies of analytical flow injection measurements during four decades since their invention has reinforced the solid position of flow analysis in the arsenal of techniques and instrumentation of contemporary chemical analysis.

A regular “signal attenuation” electrochemical aptasensor for highly sensitive detection of streptomycin

A novel aptasensor based on PCNRs and MWCNTs–CuO–AuNPs as the nanomatrix was constructed for the highly sensitive detection of streptomycin.