Rapid, sensitive and label-free detection of pathogenic bacteria using a bacteria-imprinted conducting polymer film-based electrochemical sensor

Surface-Imprinted Polysiloxane with Recognition Ability Based on an ITO Layer for Rapid Detection of Fusarium oxysporum f. sp. cubense by the Naked Eye

Direct observation by the naked eye of fluorescence-stained microbes adsorbed on surface imprinted polymers (SIPs) is highly challenging and limited by speed, accuracy and the semiquantitative nature of the method. In this study, we tested for the presence of spores of Fusarium oxysporum f. sp. cubense race 4 (Foc4), which cause severe banana Fusarium wilt disease and reduces the area of banana plants. This kind of spore can become dormant in soil, which means that the detection of secreted molecules (molecular imprinting) in soil may be inaccurate; detection methods such as polymerase chain reaction (PCR) and Raman spectroscopy are more accurate but time-consuming and inconvenient. Therefore, a semiquantitative and rapid SIP detection method for Foc4 was proposed. Based on the ITO conductive layer, a reusable and naked-eye-detectable Foc4-PDMS SIP film was prepared with a site density of approximately 9000 mm-2. Adsorption experiments showed that when the Foc4 spore concentration was between 104 to 107 CFU/mL, the number of Foc4 spores adsorbed and the fluorescence intensity were strongly correlated with the concentration and could be fully distinguished by the naked eye after fluorescence staining. Adsorption tests on other microbes showed that the SIP film completely recognized only the Foc series. All the results were highly consistent with the naked-eye observations after fluorescence staining, and the results of the Foc4-infected soil experiment were also close to the ideal situation. Taken together, these results showed that Foc4-PDMS SIPs have the ability to rapidly and semiquantitatively detect the concentration of Foc in soil, which can provide good support for banana cultivation. This method also has potential applications in the detection of other fungal diseases.

Portable Saliva Sensor Based on Dual Recognition Elements for Detection of Caries Pathogenic Bacteria

Dental caries is one of the most common diseases affecting more than 2 billion people's health worldwide. In a clinical setting, it is challenging to predict and proactively guard against dental cavities prior to receiving a confirmed diagnosis. Streptococcus mutans (S. mutans) in saliva has been recognized as the main causative bacterial agent that causes dental caries. High sensitivity, good selectivity, and a wide detection range are incredibly important factors to affect S. mutans detection in practical applications. In this study, we present a portable saliva biosensor designed for the early detection of S. mutans with the potential to predict the occurrence of dental cavities. The biosensor was fabricated using a S. mutans-specific DNA aptamer and S. mutans-imprinted polymers. Methylene blue was utilized as a redox probe in the sensor to generate current signals for analysis. When S. mutans enters complementarily S. mutans cavities, it blocks electron transfer between methylene blue and the electrode, resulting in decreases in the reduction current signal. The signal variations are associated with S. mutans concentrations that are useful for quantitative analysis. The linear detection range of S. mutans is 102-109 cfu mL-1, which covers the critical concentration of high caries risk. The biosensor exhibited excellent selectivity toward S. mutans in the presence of other common oral bacteria. The biosensor's wide detection range, excellent selectivity, and low limit of detection (2.6 cfu mL-1) are attributed to the synergistic effect of aptamer and S. mutans-imprinted polymers. The sensor demonstrates the potential to prevent dental caries.

Disposable electrochemical biosensors for the detection of bacteria in the light of antimicrobial resistance

Persistent and inappropriate use of antibiotics is causing rife antimicrobial resistance (AMR) worldwide. Common bacterial infections are thus becoming increasingly difficult to treat without the use of last resort antibiotics. This has necessitated a situation where it is imperative to confirm the infection to be bacterial, before treating it with antimicrobial speculatively. Conventional methods of bacteria detection are either culture based which take anywhere between 24 and 96 hor require sophisticated molecular analysis equipment with libraries and trained operators. These are difficult propositions for resource limited community healthcare setups of developing or less developed countries. Customized, inexpensive, point-of-care (PoC) biosensors are thus being researched and developed for rapid detection of bacterial pathogens. The development and optimization of disposable sensor substrates is the first and crucial step in development of such PoC systems. The substrates should facilitate easy charge transfer, a high surface to volume ratio, be tailorable by the various bio-conjugation chemistries, preserve the integrity of the biorecognition element, yet be inexpensive. Such sensor substrates thus need to be thoroughly investigated. Further, if such systems were made disposable, they would attain immunity to biofouling. This article discusses a few potential disposable electrochemical sensor substrates deployed for detection of bacteria for environmental and healthcare applications. The technologies have significant potential in helping reduce bacterial infections and checking AMR. This could help save lives of people succumbing to bacterial infections, as well as improve the overall quality of lives of people in low- and middle-income countries.

Ultrasensitive and Highly Selective Detection of Staphylococcus aureus at the Single-Cell Level Using Bacteria-Imprinted Polymer and Vancomycin-Conjugated MnO2 Nanozyme

Pathogenic bacterial infections, even at extremely low concentrations, pose significant threats to human health. However, the challenge persists in achieving high-sensitivity bacterial detection, particularly in complex samples. Herein, we present a novel sandwich-type electrochemical sensor utilizing bacteria-imprinted polymer (BIP) coupled with vancomycin-conjugated MnO2 nanozyme (Van@BSA-MnO2) for the ultrasensitive detection of pathogenic bacteria, exemplified by Staphylococcus aureus (S. aureus). The BIP, in situ prepared on the electrode surface, acts as a highly specific capture probe by replicating the surface features of S. aureus. Vancomycin (Van), known for its affinity to bacterial cell walls, is conjugated with a Bovine serum albumin (BSA)-templated MnO2 nanozyme through EDC/NHS chemistry. The resulting Van@BSA-MnO2 complex, serving as a detection probe, provides an efficient catalytic platform for signal amplification. Upon binding with the captured S. aureus, the Van@BSA-MnO2 complex catalyzes a substrate reaction, generating a current signal proportional to the target bacterial concentration. The sensor displays remarkable sensitivity, capable of detecting a single bacterial cell in a phosphate buffer solution. Even in complex milk matrices, it maintains outstanding performance, identifying S. aureus at concentrations as low as 10 CFU mL-1 without requiring intricate sample pretreatment. Moreover, the sensor demonstrates excellent selectivity, particularly in distinguishing target S. aureus from interfering bacteria of the same genus at concentrations 100-fold higher. This innovative method, employing entirely synthetic materials, provides a versatile and low-cost detection platform for Gram-positive bacteria. In comparison to existing nanozyme-based bacterial sensors with biological recognition materials, our assay offers distinct advantages, including enhanced sensitivity, ease of preparation, and cost-effectiveness, thereby holding significant promise for applications in food safety and environmental monitoring.

An electrochemical biosensor for Staphylococcus aureus detection based on a multilevel surface 3D micro/nanostructure

Detection of pathogens is one of the key concerns for hospitals, the food industry, water suppliers, or other environmental engineering practices because pathogens can cause a wide range of infectious risks. Staphylococcus aureus (S. aureus) is one of the most common pathogens that are hazardous to human health and its existence is an important index to the safety of food, environmental sanitation, or medical products. In this study, we prepared an electrode with designed surface multilevel 3D micro/nano protrusions for facile and efficient S. aureus detection. The existence of these multilevel protrusions enhanced the adsorption of S. aureus. Hence, the detection limit could be as low as 10 CFU mL-1. Furthermore, the electrode was also successfully used to detect S. aureus in actual samples, such as milk and artificial human tissue fluid. It was found that the recovery of the reported approach showed no significant difference from that of the traditional plate count method. However, compared with the plate count method, the detection process of our approach is much more time-saving and easy-operating. These advantages of the approach we report, such as high sensitivity, reliability, quickness, and user-friendliness, make it a potential platform for detecting S. aureus in relation to the food industry and clinical diagnosis.

Advances in the Use of Conducting Polymers for Healthcare Monitoring

Conducting polymers (CPs) are an innovative class of materials recognized for their high flexibility and biocompatibility, making them an ideal choice for health monitoring applications that require flexibility. They are active in their design. Advances in fabrication technology allow the incorporation of CPs at various levels, by combining diverse CPs monomers with metal particles, 2D materials, carbon nanomaterials, and copolymers through the process of polymerization and mixing. This method produces materials with unique physicochemical properties and is highly customizable. In particular, the development of CPs with expanded surface area and high conductivity has significantly improved the performance of the sensors, providing high sensitivity and flexibility and expanding the range of available options. However, due to the morphological diversity of new materials and thus the variety of characteristics that can be synthesized by combining CPs and other types of functionalities, choosing the right combination for a sensor application is difficult but becomes important. This review focuses on classifying the role of CP and highlights recent advances in sensor design, especially in the field of healthcare monitoring. It also synthesizes the sensing mechanisms and evaluates the performance of CPs on electrochemical surfaces and in the sensor design. Furthermore, the applications that can be revolutionized by CPs will be discussed in detail.

Bacteria-imprinted impedimetric sensor based on doping-induced nanostructured polypyrrole for determination of Escherichia coli

A simple and label-free bacteria-imprinted impedimetric (BIP) sensor for the sensitive measurement of Escherichia coli has been developed. The BIP sensor is fabricated by one-step electropolymerization of pyrrole (functional monomer), copper phthalocyanine-3, 4', 4'', 4'''-tetrasulfonic acid tetrasodium salt (CuPcTs, dopant), and target bacteria (E. coli O157:H7) on a glassy carbon electrode. After the removal of the bacterial template, the established imprinted sites on the CuPcTs-doped polypyrrole film (PPy/CuPcTs) enable the highly selective rebinding of target bacteria and the resulting impedance change of the sensing interface is used to detect the target bacteria. We found that during the electropolymerization process, CuPcTs induced pyrrole to form granular-like nanostructured PPy/CuPcTs with excellent conductivity compared with the PPy film, substantially improving the sensitivity of the proposed sensor. The sensor presented a wide detection range (102 ~ 107 CFU⋅mL-1, RSD 1.1% ~ 3.5%) with a limit of detection of 21 CFU⋅mL-1. Furthermore, the proposed sensor effectively distinguished E. coli O157:H7 from other non-target bacteria and exhibited good practicality with recoveries from 91 to 103% in spiked real samples, indicating the potential utility of the sensor in food safety and environmental monitoring.

Rising to the surface: capturing and detecting bacteria by rationally-designed surfaces

Analytical microbiology has made substantial progress since its conception, starting from potato slices, through selective agar media, to engineered surfaces modified with capture probes. While the latter represents the dominant approach in designing sensors for bacteria detection, the importance of sensor surface properties is frequently ignored. Herein, we highlight their significant role in the complex process of bacterial transition from planktonic to sessile, representing the first and critical step in bacteria detection. We present the main surface features and discuss their effect on the bio-solid interface and the resulting sensing capabilities for both flat and particulate systems. The concepts of rationally-designed surfaces for enhanced bacterial detection are presented with recent examples of sensors (capture probe-free) relying solely on surface cues.

D-tartaric acid doping improves the performance of whole-cell bacteria imprinted polymer for sensing Vibrio parahaemolyticus

Whole-cell bacteria imprinted polymer-based sensors still face challenges in the form of the difficulty of removing the template entirely, low affinity, and poor sensitivity. To further improve their performance, it is pivotal to modulate the morphology and chemical properties of imprintied polymer by taking advantage of doping engineering. Here we introduced D-tartaric acid (D-TA) as a dopant and employed pyrrole as a functional monomer to construct D-TA/polypyrrole (PPy)-based bacteria imprinted polymer (DPBIP) sensor for Vibrio parahaemolyticus (VP) detection. It is demonstrated that D-TA doping can synergistically accelerate the removal of template bacteria from imprinted polymers (1.5 h), improve bacteria affinity of imprinted sites (the recognition time of 30 min), and enhance the sensitivity of DPBIP sensor (a detection limit of 19 CFU mL-1). The DPBIP sensor had a linear range of 102∼106 CFU mL-1 and exhibited high selectivity and good repeatability. Moreover, a recovery of 94.8%-105.3% was achieved in drinking water and oyster samples. Therefore, small functional molecules doping opens a new avenue to engineering BIP-based sensors with high performance, holding potential applications in securing food safety.

Imprinting of nanoparticles in thin films: Quo Vadis?

Nanomaterials, and especially nanoparticles, have been introduced to almost any aspect of our lives. This has caused increasing concern as to their toxicity and adverse effects on the environment and human health. The activity of nanoparticles, including their nanotoxicity, is not only a function of the material they are made of but also their size, shape, and surface properties. It is evident that there is an unmet need for simple approaches to the speciation of nanoparticles, namely to monitor and detect them based on their properties. An appealing method for such speciation involves the imprinting of nanoparticles in soft matrices. The principles of imprinting nanoparticles originate from the molecularly imprinted polymer (MIP) approach. This review summarizes the current status of this emerging field, which bridges between the traditional MIP approach and the imprinting of larger entities such as viruses and bacteria. The concepts of nanoparticle imprinting and the requirement of both physical and chemical matching between the nanoparticles and the matrix are discussed and demonstrated.

Recent Advances in Electrochemical Biosensors for Food Control

The rapid and sensitive detection of food contaminants is becoming increasingly important for timely prevention and treatment of foodborne disease. In this review, we discuss recent developments of electrochemical biosensors as facile, rapid, sensitive, and user-friendly analytical devices and their applications in food safety analysis, owing to the analytical characteristics of electrochemical detection and to advances in the design and production of bioreceptors (antibodies, DNA, aptamers, peptides, molecular imprinted polymers, enzymes, bacteriophages, etc.). They can offer a low limit of detection required for food contaminants such as allergens, pesticides, antibiotic traces, toxins, bacteria, etc. We provide an overview of a broad range of electrochemical biosensing designs and consider future opportunities for this technology in food control.

Label-Free Electrochemical Methods for Disease Detection

Label-free electrochemical biosensing leverages the advantages of label-free techniques, low cost, and fewer user steps, with the sensitivity and portability of electrochemical analysis. In this review, we identify four label-free electrochemical biosensing mechanisms: (a) blocking the electrode surface, (b) allowing greater access to the electrode surface, (c) changing the intercalation or electrostatic affinity of a redox probe to a biorecognition unit, and (d) modulating ion or electron transport properties due to conformational and surface charge changes. Each mechanism is described, recent advancements are summarized, and relative advantages and disadvantages of the techniques are discussed. Furthermore, two avenues for gaining further diagnostic information from label-free electrochemical biosensors, through multiplex analysis and incorporating machine learning, are examined.

An ultrasensitive bacterial imprinted electrochemical sensor for the determination of Lactobacillus rhamnosus GG

An ultrasensitive label-free electrochemical sensor based on a homemade imprinted polypyrrole (PPy) polymer film was prepared to achieve quantitative determination of Lactobacillus rhamnosus GG (LGG). The LGG-imprinted polymer (LIP) film was deposited on a portable screen-printed electrode (SPE) via electropolymerization, which constituted an independent integrated system. The main preparation parameters of the LIP sensor were investigated to obtain optimal performance. Under optimized conditions, the peak current response of the LIP sensor showed a linear relationship with the logarithmic value of LGG concentration in the range from 10¹ to 10⁹ CFU mL^-1 and a detection limit of 5 CFU mL^-1. The proposed LIP sensor has achieved efficient, ultrasensitive, highly selective, and cost-effective detection of LGG and can be further developed for practical applications in the quality inspection and development of probiotic products.

Dual DNA recycling amplifications coupled with Au NPs@ZIF-MOF accelerator for enhanced electrochemical ratiometric sensing of pathogenic bacteria

Sensitive and accurate quantification of pathogenic bacteria is vastly significant to the related food safety. Herein, a sensitive ratiometric electrochemical biosensor was developed for the detection of Staphylococcus aureus (S. aureus) based on dual DNA recycling amplifications and Au NPs@ZIF-MOF accelerator. Gold nanoparticles-loaded Zeolitic imidazolate metal-organic framework (Au NPs@ZIF-MOF) as electrode substrate possessed a large specific surface area for nucleic acid adsorption, and as an accelerator promoted the transfer of electrons. The strong recognition of aptamer to target S. aureus could initiate the padlock probe-based exponential rolling circle amplification (P-ERCA, as the first DNA recycling amplification), generating large numbers of trigger DNA strands. The released trigger DNA further activated the catalytic hairpin assembly (CHA, as the second DNA recycling amplification) on electrode surface. Consequently, P-ERCA and CHA continuously brought about one target to many signal transduction, leading to an exponential amplification. To achieve the accuracy of detection, the signal ratio of methylene blue (MB) and ferrocene (Fc) (I_MB/I_Fc) was applied for intrinsic self-calibrating. Taking advantages of dual DNA recycling amplifications and Au NPs@ZIF-MOF, the proposed sensing system displayed high sensitivity for S. aureus quantification with a linear range of 5-10⁸ CFU/mL, and the limit of detection was 1 CFU/mL. Moreover, this system represented excellent reproducibility, selectivity, and practicability for S. aureus analysis in foods.

Dual Synthetic Receptor-Based Sandwich Electrochemical Sensor for Highly Selective and Ultrasensitive Detection of Pathogenic Bacteria at the Single-Cell Level

Sensitive and rapid detection of pathogenic bacteria is essential for effective source control and prevention of microbial infectious diseases. However, it remains a substantial challenge to rapidly detect bacteria at the single-cell level. Herein, we present an electrochemical sandwich sensor for highly selective and ultrasensitive detection of a single bacterial cell based on dual recognition by the bacteria-imprinted polymer film (BIF) and aptamer. The BIF was used as the capture probe, which was in situ fabricated on the electrode surface within 15 min via electropolymerization. The aptamer and electroactive 6-(Ferrocenyl)hexanethiol cofunctionalized gold nanoparticles (Au@Fc-Apt) were employed as the signal probe. Once the target bacteria were anchored on the BIF-modified electrode, the Au@Fc-Apt was further specifically bound to the bacteria, generating enhanced current signals for ultrasensitive detection of Staphylococcus aureus down to a single cell in phosphate buffer solution. Even in the complex milk samples, the sensor could detect as low as 10 CFU mL^-1 of S. aureus without any complicated pretreatment except for 10-fold dilution. Moreover, the current response to the target bacteria was hardly affected by the coexisting multiple interfering bacteria, whose number is 30 times higher than the target, demonstrating the excellent selectivity of the sensor. Compared with most reported sandwich-type electrochemical sensors, this assay is more sensitive and more rapid, requiring less time (1.5 h) for the sensing interface construction. By virtue of its sensitivity, rapidity, selectivity, and cost-effectiveness, the sensor can serve as a universal detection platform for monitoring pathogenic bacteria in fields of food/public safety.

Advances, applications, and limitations of portable and rapid detection technologies for routinely encountered foodborne pathogens

Traditional foodborne pathogen detection methods are highly dependent on pre-treatment of samples and selective microbiological plating to reliably screen target microorganisms. Inherent limitations of conventional methods include longer turnaround time and high costs, use of bulky equipment, and the need for trained staff in centralized laboratory settings. Researchers have developed stable, reliable, sensitive, and selective, rapid foodborne pathogens detection assays to work around these limitations. Recent advances in rapid diagnostic technologies have shifted to on-site testing, which offers flexibility and ease-of-use, a significant improvement from traditional methods' rigid and cumbersome steps. This comprehensive review aims to thoroughly discuss the recent advances, applications, and limitations of portable and rapid biosensors for routinely encountered foodborne pathogens. It discusses the major differences between biosensing systems based on the molecular interactions of target analytes and biorecognition agents. Though detection limits and costs still need further improvement, reviewed technologies have high potential to assist the food industry in the on-site detection of biological hazards such as foodborne pathogens and toxins to maintain safe and healthy foods. Finally, this review offers targeted recommendations for future development and commercialization of diagnostic technologies specifically for emerging and re-emerging foodborne pathogens.

Research progress on detection techniques for point-of-care testing of foodborne pathogens

The global burden of foodborne disease is enormous and foodborne pathogens are the leading cause of human illnesses. The detection of foodborne pathogenic bacteria has become a research hotspot in recent years. Rapid detection methods based on immunoassay, molecular biology, microfluidic chip, metabolism, biosensor, and mass spectrometry have developed rapidly and become the main methods for the detection of foodborne pathogens. This study reviewed a variety of rapid detection methods in recent years. The research advances are introduced based on the above technical methods for the rapid detection of foodborne pathogenic bacteria. The study also discusses the limitations of existing methods and their advantages and future development direction, to form an overall understanding of the detection methods, and for point-of-care testing (POCT) applications to accurately and rapidly diagnose and control diseases.

Bulk and Surface Acoustic Wave Biosensors for Milk Analysis

Milk and dairy products are common foods and, therefore, are subject to regular controls. Such controls cover both the identification and quantification of specific components and the determination of physical parameters. Components include the usual milk ingredients, mainly carbohydrates, proteins, and fat, and any impurities that may be present. The latter range from small molecules, such as drug residues, to large molecules, e.g., protein-based toxins, to pathogenic microorganisms. Physical parameters of interest include viscosity as an indicator of milk gelation. Bulk and surface acoustic wave sensors, such as quartz crystal microbalance (QCM) and surface acoustic wave (SAW) devices, can principally be used for both types of analysis, with the actual application mainly depending on the device coating and the test format. This review summarizes the achievements of acoustic sensor devices used for milk analysis applications, including the determination of physical liquid parameters and the detection of low- and high-molecular-weight analytes and microorganisms. It is shown how the various requirements resulting from the respective analytes and the complex sample matrix are addressed, and to what extent the analytical demands, e.g., with regard to legal limits, are met.

When smartphone enters food safety: A review in on-site analysis for foodborne pathogens using smartphone-assisted biosensors

Pathogens are one of the supreme threats for the public health around the world in food supply chain. The on-site monitoring is an emerging trend for screening pathogens during the food processing and preserving. Traditional analytical tools have been unable to satisfy the current demands. Smartphones have enormous potentials for achieving on-site detection of foodborne pathogens, with intrinsic advantages such as small size, high accessibility, fast processing speed, and powerful imaging capacity. This review aims to synthesize the current advances in smartphone-assisted biosensors (SABs) for sensing foodborne pathogens, and briefly put forward the problem that consist in the research. We present the role of nanotechnology and recognition modes targeting foodborne pathogens in SABs, and discuss the signal conversion platforms coupling with smartphone. The challenges and perspectives in SABs are also proposed. The smartphone analytics area is moving forward, and it much be subject to careful quality standards and validation.

Imprinted Polydimethylsiloxane-Graphene Oxide Composite Receptor for the Biomimetic Thermal Sensing of Escherichia coli

This work presents an imprinted polymer-based thermal biomimetic sensor for the detection of Escherichia coli. A novel and facile bacteria imprinting protocol for polydimethylsiloxane (PDMS) films was investigated, and these receptor layers were functionalized with graphene oxide (GO) in order to improve the overall sensitivity of the sensor. Upon the recognition and binding of the target to the densely imprinted polymers, a concentration-dependent measurable change in temperature was observed. The limit of detection attained for the sensor employing PDMS-GO imprints was 80 ± 10 CFU/mL, a full order lower than neat PDMS imprints (670 ± 140 CFU/mL), illustrating the beneficial effect of the dopant on the thermo-dynamical properties of the interfacial layer. A parallel benchmarking of the thermal sensor with a commercial impedance analyzer was performed in order to prove the possibility of using the developed PDMS-GO receptors with multiple readout platforms. Moreover, S. aureus, C. sakazakii and an additional E. coli strain were employed as analogue species for the assessment of the selectivity of the device. Finally, because of the potential that this biomimetic platform possesses as a low-cost, rapid, and on-site tool for monitoring E. coli contamination in food safety applications, spiked fruit juice was analyzed as a real sample. Reproducible and sensitive results fulfill the limit requirements of the applicable European microbiological regulation.

Rapid photothermal detection of foodborne pathogens based on the aggregation of MPBA-AuNPs induced by MPBA using a thermometer as a readout

Rapid and portable detection of foodborne pathogens is of great significance for food safety and public health. The colorimetric methods based on naked-eye have been demonstrated to be a suitable qualitative method for point-of-care testing (POCT). However, analytical instruments like a microplate reader must be needed for the quantitative assay. To overcome its limitation, we herein report a novel photothermal method for foodborne pathogens based on the photothermal effect of aggregated mercaptophenylboronic acid-functionalized AuNPs (MPBA-AuNPs) induced by MPBA to translate the colorimetric detection into a simple temperature measurement using thermometers as the readout. The aggregated AuNPs show higher photothermal conversion efficiency than well-separated AuNPs under 660 nm laser irradiation. In the presence of bacteria, MPBA-AuNPs will attach to the surface of bacteria and keep separated from aggregation induced by excess MPBA, resulting in a lower temperature increase under 660 nm laser irradiation. Using E. coli O157:H7 as a model target, a good linear relationship is observed between temperature increase and bacteria concentration from 1.00 × 10⁵-1.00 × 10⁹ cfu mL^-1 (R² = 0.9877) with a detection limit of 1.97 × 10⁴ cfu mL^-1, which is three orders of magnitude lower than of the MPBA-AuNPs-based colorimetric assays. The proposed photothermal method provided a universal platform for rapid and portable detection of broad-spectrum bacteria strains in real samples.

Recent Advances in Quartz Crystal Microbalance Biosensors Based on the Molecular Imprinting Technique for Disease-Related Biomarkers

The molecular imprinting technique is a quickly developing field of interest regarding the synthesis of artificial recognition elements that enable the specific determination of target molecule/analyte from a matrix. Recently, these smart materials can be successfully applied to biomolecule detection in biomimetic biosensors. These biosensors contain a biorecognition element (a bioreceptor) and a transducer, like their biosensor analogs. Here, the basic difference is that molecular imprinting-based biosensors use a synthetic recognition element. Molecular imprinting polymers used as the artificial recognition elements in biosensor platforms are complementary in shape, size, specific binding sites, and functionality to their template analytes. Recent progress in biomolecular recognition has supplied extra diagnostic and treatment methods for various diseases. Cost-effective, more robust, and high-throughput assays are needed for monitoring biomarkers in clinical settings. Quartz crystal microbalance (QCM) biosensors are promising tools for the real-time and quick detection of biomolecules in the past two decades A quick, simple-to-use, and cheap biomarkers detection technology based on biosensors has been developed. This critical review presents current applications in molecular imprinting-based quartz crystal microbalance biosensors for the quantification of biomarkers for disease monitoring and diagnostic results.

Highly sensitive multiplex detection of foodborne pathogens using a SERS immunosensor combined with novel covalent organic frameworks based biologic interference-free Raman tags

Rapid and reliable multiplex detection of foodborne pathogens is in great demand for ensuring food safety and preventing foodborne diseases. In this study, we developed a highly sensitive SERS immunosensor for the simultaneous detection of multiple foodborne pathogens. Novel biologic interference-free Raman tags synthesized by using the covalent organic frameworks (COF) TBDP as nanocontainer to load biologic interference-free Raman reporters and specific antibodies for interested targets were used to convert and amplify signals of foodborne pathogens. In addition, lectin functionalized magnetic nanoparticles (MNPs@Con A) which could efficiently bind to the carbohydrate constituents on the surface of pathogens were prepared to capture and isolate multiple pathogens simultaneously. The recognition of the target foodborne pathogen impels the generation of sandwich-like composites of MNPs@Con A/pathogen/TBDP@Raman tags, and these composites could be quickly separated from the sample matrix with the assistance of an external magnet. Besides, a mass of Raman reporters was released by eluting the collected MNPs@Con A/pathogen/TBDP@Raman tags composites. Combined with a portable Raman system, characteristic Raman signals (2271 and 2113 cm^-1) of the occupied reporters located at the biologic interference-free region were observed and used for the simultaneous detection of two different foodborne pathogenic strains. And an equal limit of detection of 10¹ CFU/mL was achieved for each strain. This strategy provides new insight into the application of SERS in the detection of pathogenic bacteria.

Recent advances in the biosensors application for the detection of bacteria and viruses in wastewater

The presence of disease-causing pathogens in wastewater can provide an excellent diagnostic tool for infectious diseases. Biosensors are far superior to conventional methods used for regular infection screening and surveillance testing. They are rapid, sensitive, inexpensive portable and carry no risk of exposure in their detection schemes. In this context, this review summarizes the most recently developed biosensors for the detection of bacteria and viruses in wastewater. The review also provides information on the new detection methods aimed at screening for SARS-CoV-2, which has now caused more than 4 million deaths. In addition, the review highlights the potential behind on-line and real-time detection of pathogens in wastewater pipelines. Most of the biosensors reported were not targeted to wastewater samples due to the complexity of the matrix. However, this review highlights on the performance factors of recently developed biosensors and discusses the importance of nanotechnology in amplifying the output signals, which in turn increases the accuracy and reliability of biosensors. Current research on the applicability of biosensors in wastewater promises a dramatic change to the conventional approach in the field of medical screening.

Reusable and universal impedimetric sensing platform for the rapid and sensitive detection of pathogenic bacteria based on bacteria-imprinted polythiophene film

A bacteria-imprinted polythiophene film (BIF)-based impedimetric sensor was proposed for the rapid and sensitive detection of S. aureus. A significant improvement is the reduced time for both BIF fabrication (15 min) and bacterial capturing (10 min).

Molecularly Imprinted Polymers in Diagnostics: Accessing Analytes in Biofluids

Bio-applied molecularly imprinted polymers (MIPs) are biomimetic materials with tailor-made synthetic recognition sites, mimicking biological counterparts known for their sensitive and selective analyte detection. MIPs, specifically designed for biomarker analysis...

Simple electrochemical detection of Listeria monocytogenes based on a surface-imprinted polymer-modified electrode

Listeria monocytogenes (LM) is a foodborne pathogen, and it can pose a risk of serious diseases to the human health. Hence, the development of an effective method for the detection of LM is very important. In this study, by selecting LM as the template and 3-thiopheneacetic acid as the functional monomer, an LM-imprinted polymer (LIP)-based sensor was proposed for the first time to detect LM by electropolymerizing TPA on the glassy carbon electrode (GCE) surface in the presence of LM. After the removal of the LM template from the electrode surface, the obtained sensor was denoted as LIP/GCE, which could effectively recognize and capture LM cells. By using [Fe(CN)₆]^4-/3- as the probe, its peak current at LIP/GCE could be restricted when the LM cells were captured into the imprinted cavity of LIP/GCE, and the current value decreased with an increase in the LM concentration. Serious conditions were optimized for achieving highly sensitive detection, and a low detection limit (6 CFU mL^-1) coupled with a wide linear range (10 to 10⁶ CFU mL^-1) was obtained for LM. Finally, the inter-electrode reproducibility, stability, selectivity, and applicability of LIP/GCE were also investigated, and the obtained results were acceptable.

Electrochemical Biosensors in Food Safety: Challenges and Perspectives

Safety and quality are key issues for the food industry. Consequently, there is growing demand to preserve the food chain and products against substances toxic, harmful to human health, such as contaminants, allergens, toxins, or pathogens. For this reason, it is mandatory to develop highly sensitive, reliable, rapid, and cost-effective sensing systems/devices, such as electrochemical sensors/biosensors. Generally, conventional techniques are limited by long analyses, expensive and complex procedures, and skilled personnel. Therefore, developing performant electrochemical biosensors can significantly support the screening of food chains and products. Here, we report some of the recent developments in this area and analyze the contributions produced by electrochemical biosensors in food screening and their challenges.

Molecularly imprinted polymers - towards electrochemical sensors and electronic tongues

Molecularly imprinted polymers (MIPs) are artificially synthesized materials to mimic the molecular recognition process of biological macromolecules such as substrate-enzyme or antigen-antibody. The combination of these biomimetic materials with electrochemical techniques has allowed the development of advanced sensing devices, which significantly improve the performance of bare or catalyst-modified sensors, being able to unleash new applications. However, despite the high selectivity that MIPs exhibit, those can still show some cross-response towards other compounds, especially with chemically analogous (bio)molecules. Thus, the combination of MIPs with chemometric methods opens the room for the development of what could be considered a new type of electronic tongues, i.e. sensor array systems,  based on its usage. In this direction, this review provides an overview of the more common synthetic approaches, as well as the strategies that can be used to achieve the integration of MIPs and electrochemical sensors, followed by some recent examples over different areas in order to illustrate the potential of such combination in very diverse applications.