Biosensors

10 pages, 2354 KiB

Open AccessCommunication

Spectroscopic and Structural Analysis of Cu²⁺-Induced Fluorescence Quenching of ZsYellow

by In Jung Kim, Yongbin Xu and Ki Hyun Nam

Biosensors 2020, 10(3), 29; https://doi.org/10.3390/bios10030029 - 23 Mar 2020

Cited by 7 | Viewed by 5029

Fluorescent proteins exhibit fluorescence quenching by specific transition metals, suggesting their potential as fluorescent protein-based metal biosensors. Each fluorescent protein exhibits unique spectroscopic properties and mechanisms for fluorescence quenching by metals. Therefore, the metal-induced fluorescence quenching analysis of various new fluorescent proteins would [...] Read more.

Fluorescent proteins exhibit fluorescence quenching by specific transition metals, suggesting their potential as fluorescent protein-based metal biosensors. Each fluorescent protein exhibits unique spectroscopic properties and mechanisms for fluorescence quenching by metals. Therefore, the metal-induced fluorescence quenching analysis of various new fluorescent proteins would be important step towards the development of such fluorescent protein-based metal biosensors. Here, we first report the spectroscopic and structural analysis of the yellow fluorescent protein ZsYellow, following its metal-induced quenching. Spectroscopic analysis showed that ZsYellow exhibited a high degree of fluorescence quenching by Cu²⁺. During Cu²⁺-induced ZsYellow quenching, fluorescence emission was recovered by adding EDTA. The crystal structure of ZsYellow soaked in Cu²⁺ solution was determined at a 2.6 Å resolution. The electron density map did not indicate the presence of Cu²⁺ around the chromophore or the β-barrel surface, which resulted in fluorescence quenching without Cu²⁺ binding to specific site in ZsYellow. Based on these results, we propose the fluorescence quenching to occur in a distance-dependent manner between the metal and the fluorescent protein, when these components get to a closer vicinity at higher metal concentrations. Our results provide useful insights for future development of fluorescent protein-based metal biosensors. Full article

► Show Figures

Figure 1

23 pages, 6096 KiB

Open AccessArticle

AC and DC Differential Bridge Structure Suitable for Electrochemical Interfacial Capacitance Biosensing Applications

by Sara Neshani, Charles K. A. Nyamekye, Scott Melvin, Emily A. Smith, Degang J. Chen and Nathan M. Neihart

Biosensors 2020, 10(3), 28; https://doi.org/10.3390/bios10030028 - 22 Mar 2020

Cited by 3 | Viewed by 4622

Abstract

This paper presents a capacitive differential bridge structure with both AC and DC excitation and balancing capability for low cost electrode-solution interfacial capacitance biosensing applications. The proposed series RC balancing structure offers higher sensitivity, lower susceptibility to common-mode interferences, and drift control. To [...] Read more.

This paper presents a capacitive differential bridge structure with both AC and DC excitation and balancing capability for low cost electrode-solution interfacial capacitance biosensing applications. The proposed series RC balancing structure offers higher sensitivity, lower susceptibility to common-mode interferences, and drift control. To evaluate the bridge performance in practice, possible effects of initial bridge imbalance due to component mismatches are investigated considering the required resolution of the balancing networks, sensitivity, and linearity. This evaluation is also a guideline to designing the balancing networks, balancing algorithm and the proceeding readout interface circuitry. The proposed series RC bridge structure is implemented along with a custom single frequency real-time amplification/filtering readout board with real-time data acquisition and sine fitting. The main specifications for the implemented structure are 8-bit detection resolution if the total expected fractional capacitance change at the interface is roughly 1%. The characterization and measurement results show the effectiveness of the proposed structure in achieving the design target. The implemented structure successfully achieves distinct detection levels for tiny total capacitance change at the electrode-solution interface, utilizing Microcystin-(Leucine-Arginine) toxin dilutions as a proof of concept. Full article

► Show Figures

Figure 1

9 pages, 1709 KiB

Open AccessArticle

Graphene Oxide Bulk-Modified Screen-Printed Electrodes Provide Beneficial Electroanalytical Sensing Capabilities

by Samuel J. Rowley-Neale, Dale A. C. Brownson, Graham Smith and Craig E. Banks

Biosensors 2020, 10(3), 27; https://doi.org/10.3390/bios10030027 - 19 Mar 2020

Cited by 21 | Viewed by 4667

Abstract

We demonstrate a facile methodology for the mass production of graphene oxide (GO) bulk-modified screen-printed electrodes (GO-SPEs) that are economical, highly reproducible and provide analytically useful outputs. Through fabricating GO-SPEs with varying percentage mass incorporations (2.5%, 5%, 7.5% and 10%) of GO, an [...] Read more.

We demonstrate a facile methodology for the mass production of graphene oxide (GO) bulk-modified screen-printed electrodes (GO-SPEs) that are economical, highly reproducible and provide analytically useful outputs. Through fabricating GO-SPEs with varying percentage mass incorporations (2.5%, 5%, 7.5% and 10%) of GO, an electrocatalytic effect towards the chosen electroanalytical probes is observed, which increases with greater GO incorporated compared to bare/graphite SPEs. The optimum mass ratio of 10% GO to 90% carbon ink produces an electroanalytical signal towards dopamine (DA) and uric acid (UA) which is ca. ×10 greater in magnitude than that achievable at a bare/unmodified graphite SPE. Furthermore, 10% GO-SPEs exhibit a competitively low limit of detection (3σ) towards DA at ca. 81 nM, which is superior to that of a bare/unmodified graphite SPE at ca. 780 nM. The improved analytical response is attributed to the large number of oxygenated species inhabiting the edge and defect sites of the GO nanosheets, which are able to exhibit electrocatalytic responses towards inner-sphere electrochemical analytes. Our reported methodology is simple, scalable, and cost effective for the fabrication of GO-SPEs that display highly competitive LODs and are of significant interest for use in commercial and medicinal applications. Full article

(This article belongs to the Special Issue Dedication to Professor Agustín Costa-García: Screen-Printed Electrodes-Based (Bio)sensors: Development and New Challenges of the 21st Century)

► Show Figures

Figure 1

22 pages, 2721 KiB

Open AccessReview

The Emergence of Insect Odorant Receptor-Based Biosensors

by Jonathan D. Bohbot and Sefi Vernick

Biosensors 2020, 10(3), 26; https://doi.org/10.3390/bios10030026 - 17 Mar 2020

Cited by 36 | Viewed by 8079

Abstract

The olfactory receptor neurons of insects and vertebrates are gated by odorant receptor (OR) proteins of which several members have been shown to exhibit remarkable sensitivity and selectivity towards volatile organic compounds of significant importance in the fields of medicine, agriculture and public [...] Read more.

The olfactory receptor neurons of insects and vertebrates are gated by odorant receptor (OR) proteins of which several members have been shown to exhibit remarkable sensitivity and selectivity towards volatile organic compounds of significant importance in the fields of medicine, agriculture and public health. Insect ORs offer intrinsic amplification where a single binding event is transduced into a measurable ionic current. Consequently, insect ORs have great potential as biorecognition elements in many sensor configurations. However, integrating these sensing components onto electronic transducers for the development of biosensors has been marginal due to several drawbacks, including their lipophilic nature, signal transduction mechanism and the limited number of known cognate receptor-ligand pairs. We review the current state of research in this emerging field and highlight the use of a group of indole-sensitive ORs (indolORs) from unexpected sources for the development of biosensors. Full article

► Show Figures

Graphical abstract

15 pages, 16985 KiB

Open AccessArticle

Recyclable SERS-Based Immunoassay Guided by Photocatalytic Performance of Fe₃O₄@TiO₂@Au Nanocomposites

by Yuanyuan Du, Hongmei Liu, Yiran Tian, Chenjie Gu, Ziqi Zhao, Shuwen Zeng and Tao Jiang

Biosensors 2020, 10(3), 25; https://doi.org/10.3390/bios10030025 - 16 Mar 2020

Cited by 24 | Viewed by 5135

Abstract

A novel recyclable surface-enhanced Raman scattering (SERS)-based immunoassay was demonstrated and exhibited extremely high sensitivity toward prostate specific antigen (PSA). The immunoassay, which possessed a sandwich structure, was constructed of multifunctional Fe₃O₄@TiO₂@Au nanocomposites as immune probe and [...] Read more.

A novel recyclable surface-enhanced Raman scattering (SERS)-based immunoassay was demonstrated and exhibited extremely high sensitivity toward prostate specific antigen (PSA). The immunoassay, which possessed a sandwich structure, was constructed of multifunctional Fe₃O₄@TiO₂@Au nanocomposites as immune probe and Ag-coated sandpaper as immune substrate. First, by adjusting the density of outside Au seeds on Fe₃O₄@TiO₂ core-shell nanoparticles (NPs), the structure-dependent SERS and photocatalytic performance of the samples was explored by monitoring and degradating 4-mercaptobenzonic acid (4MBA). Afterwards, the SERS enhancement capability of Ag-coated sandpaper with different meshes was investigated, and a limit of detection (LOD), as low as 0.014 mM, was achieved by utilizing the substrate. Subsequently, the recyclable feasibility of PSA detection was approved by zeta potential measurement, absorption spectra, and SEM images and, particularly, more than 80% of SERS intensity still existed after even six cycles of immunoassay. The ultralow LOD of the recyclable immunoassay was finally calculated to be 1.871 pg/mL. Therefore, the recyclable SERS-based immunoassay exhibits good application prospects for diagnosis of cancer in clinical measurements. Full article

► Show Figures

Figure 1

12 pages, 3105 KiB

Open AccessArticle

A Label-Free Immunosensor Based on Graphene Oxide/Fe₃O₄/Prussian Blue Nanocomposites for the Electrochemical Determination of HBsAg

by Shanshan Wei, Haolin Xiao, Liangli Cao and Zhencheng Chen

Biosensors 2020, 10(3), 24; https://doi.org/10.3390/bios10030024 - 14 Mar 2020

Cited by 28 | Viewed by 5062

Abstract

In this article, a highly sensitive label-free immunosensor based on a graphene oxide (GO)/Fe₃O₄/Prussian blue (PB) nanocomposite modified electrode was developed for the determination of human hepatitis B surface antigen (HBsAg). In this electrochemical immunoassay system, PB was used [...] Read more.

In this article, a highly sensitive label-free immunosensor based on a graphene oxide (GO)/Fe₃O₄/Prussian blue (PB) nanocomposite modified electrode was developed for the determination of human hepatitis B surface antigen (HBsAg). In this electrochemical immunoassay system, PB was used as a redox probe, while GO/Fe₃O₄/PB nanocomposites and AuNPs were prepared and coated on screen-printed electrodes to enhance the detection sensitivity and to immobilize the hepatitis B surface antibody (HBsAb). The immunosensor was fabricated based on the principle that the decrease in peak currents of PB is proportional to the concentration of HBsAg captured on the modified immunosensor. The experimental results revealed that the immunosensor exhibited a sensitive response to HBsAg in the range of 0.5 pg·mL⁻¹ to 200 ng·mL⁻¹, and with a low detection limit of 0.166 pg·mL⁻¹ (S/N = 3). Furthermore, the proposed immunosensor was used to detect several clinical serum samples with acceptable results, and it also showed good reproducibility, selectivity and stability, which may have a promising potential application in clinical immunoassays. Full article

► Show Figures

Figure 1

16 pages, 4748 KiB

Open AccessArticle

Simultaneous Determination of Streptomycin and Oxytetracycline Using a Oracet-Blue/Silver-Nanoparticle/Graphene-Oxide/Modified Screen-Printed Electrode

by Sanaz Akbarzadeh, Habibollah Khajesharifi and Michael Thompson

Biosensors 2020, 10(3), 23; https://doi.org/10.3390/bios10030023 - 11 Mar 2020

Cited by 13 | Viewed by 4547

Abstract

In this paper, an electrochemical technique is introduced for the determination of streptomycin (STR) in the presence of oxytetracycline (OTC) in milk samples. A novel bifunctional modified screen-printed electrode (SPE) modified with oracet blue, silver nanoparticles, and graphene oxide (OB/SNPs/GO/SPE) was fabricated. The [...] Read more.

In this paper, an electrochemical technique is introduced for the determination of streptomycin (STR) in the presence of oxytetracycline (OTC) in milk samples. A novel bifunctional modified screen-printed electrode (SPE) modified with oracet blue, silver nanoparticles, and graphene oxide (OB/SNPs/GO/SPE) was fabricated. The modified electrode plays a catalyzer role for electrooxidation of STR at pH = 7.0 and reveals a facile a separation between the oxidation peaks of STR and OTC. Calculation of kinetic parameters such as the electron transfer coefficient α and the heterogeneous rate constant k´ of STR at the OB/SNPs/GO/SPE as 8.1 ± 0.07 cm s⁻¹ and 0.32 have been obtained based on the theoretical model of Andrieux and Saveant. A differential pulse voltammetric measurement demonstrates two linear dynamic ranges, 0.4 to 240.0 nM and 240.0 to 720.0 nM and a detection limit of 0.17 nM for STR. The sensitivities of the OB/SNPs/GO/SPE towards the oxidation of STR in the absence and presence of OTC were 2.625 × 10⁻¹ and 2.633 × 10⁻¹ µA/µM, respectively. Full article

► Show Figures

Graphical abstract

13 pages, 2006 KiB

Open AccessArticle

Molecularly Imprinted Nanoparticles Based Sensor for Cocaine Detection

by Roberta D’Aurelio, Iva Chianella, Jack A. Goode and Ibtisam E. Tothill

Biosensors 2020, 10(3), 22; https://doi.org/10.3390/bios10030022 - 04 Mar 2020

Cited by 28 | Viewed by 7856

Abstract

The development of a sensor based on molecularly imprinted polymer nanoparticles (nanoMIPs) and electrochemical impedance spectroscopy (EIS) for the detection of trace levels of cocaine is described in this paper. NanoMIPs for cocaine detection, synthesized using a solid phase, were applied as the [...] Read more.

The development of a sensor based on molecularly imprinted polymer nanoparticles (nanoMIPs) and electrochemical impedance spectroscopy (EIS) for the detection of trace levels of cocaine is described in this paper. NanoMIPs for cocaine detection, synthesized using a solid phase, were applied as the sensing element. The nanoMIPs were first characterized by Transmission Electron Microscopy (TEM) and Dynamic Light Scattering and found to be ~148.35 ± 24.69 nm in size, using TEM. The nanoMIPs were then covalently attached to gold screen-printed electrodes and a cocaine direct binding assay was developed and optimized, using EIS as the sensing principle. EIS was recorded at a potential of 0.12 V over the frequency range from 0.1 Hz to 50 kHz, with a modulation voltage of 10 mV. The nanoMIPs sensor was able to detect cocaine in a linear range between 100 pg mL⁻¹ and 50 ng mL⁻¹ (R² = 0.984; p-value = 0.00001) and with a limit of detection of 0.24 ng mL⁻¹ (0.70 nM). The sensor showed no cross-reactivity toward morphine and a negligible response toward levamisole after optimizing the sensor surface blocking and assay conditions. The developed sensor has the potential to offer a highly sensitive, portable and cost-effective method for cocaine detection. Full article

(This article belongs to the Special Issue Molecularly Imprinted Polymers (MIPs) Biosensors)

► Show Figures

Graphical abstract

38 pages, 24603 KiB

Open AccessReview

The Growing Interest in Development of Innovative Optical Aptasensors for the Detection of Antimicrobial Residues in Food Products

by Valérie Gaudin

Biosensors 2020, 10(3), 21; https://doi.org/10.3390/bios10030021 - 03 Mar 2020

Cited by 15 | Viewed by 5405

Abstract

The presence of antimicrobial residues in food-producing animals can lead to harmful effects on the consumer (e.g., allergies, antimicrobial resistance, toxicological effects) and cause issues in food transformation (i.e., cheese, yogurts production). Therefore, to control antimicrobial residues in food products of animal origin, [...] Read more.

The presence of antimicrobial residues in food-producing animals can lead to harmful effects on the consumer (e.g., allergies, antimicrobial resistance, toxicological effects) and cause issues in food transformation (i.e., cheese, yogurts production). Therefore, to control antimicrobial residues in food products of animal origin, screening methods are of utmost importance. Microbiological and immunological methods (e.g., ELISA, dipsticks) are conventional screening methods. Biosensors are an innovative solution for the development of more performant screening methods. Among the different kinds of biosensing elements (e.g., antibodies, aptamers, molecularly imprinted polymers (MIP), enzymes), aptamers for targeting antimicrobial residues are in continuous development since 2000. Therefore, this review has highlighted recent advances in the development of aptasensors, which present multiple advantages over immunosensors. Most of the aptasensors described in the literature for the detection of antimicrobial residues in animal-derived food products are either optical or electrochemical sensors. In this review, I have focused on optical aptasensors and showed how nanotechnologies (nanomaterials, micro/nanofluidics, and signal amplification techniques) largely contribute to the improvement of their performance (sensitivity, specificity, miniaturization, portability). Finally, I have explored different techniques to develop multiplex screening methods. Multiplex screening methods are necessary for the wide spectrum detection of antimicrobials authorized for animal treatment (i.e., having maximum residue limits). Full article

(This article belongs to the Special Issue Biosensors Applications for the Detection of Food Contaminants and Adulterants)

► Show Figures

Figure 1

9 pages, 2772 KiB

Open AccessArticle

Surface Probe Linker with Tandem Anti-Fouling Properties for Application in Biosensor Technology

by Sandro Spagnolo, Brian De La Franier, Tibor Hianik and Michael Thompson

Biosensors 2020, 10(3), 20; https://doi.org/10.3390/bios10030020 - 03 Mar 2020

Cited by 8 | Viewed by 4189

Abstract

This paper describes the anti-fouling capability of the novel monolayer-forming surface linker 3-(3-(trichlorosilylpropyloxy) propanoyl chloride (MEG-Cl). This compound was successfully attached to quartz crystal surfaces which are employed in an electromagnetic piezoelectric acoustic sensor (EMPAS) configuration. The MEG-Cl coated surface was both employed [...] Read more.

This paper describes the anti-fouling capability of the novel monolayer-forming surface linker 3-(3-(trichlorosilylpropyloxy) propanoyl chloride (MEG-Cl). This compound was successfully attached to quartz crystal surfaces which are employed in an electromagnetic piezoelectric acoustic sensor (EMPAS) configuration. The MEG-Cl coated surface was both employed with Ni-NTA for the binding of recombinant proteins and for the tandem property of the avoidance of fouling from serum and milk. The MEG-Cl coated surfaces were found to provide a large degree of anti-fouling on the EMPAS device, and were comparable to previously studied MEG-OH surfaces. Importantly, the monolayer continued to provide anti-fouling capability to the biosensor following extension with Ni-NTA in place. Accordingly, this surface linker provides an attractive system for use in biosensor technology in terms of both its anti-fouling and linking properties. Full article

► Show Figures

Graphical abstract

9 pages, 826 KiB

Open AccessArticle

The Detection of Wound Infection by Ion Mobility Chemical Analysis

by Emma Daulton, Alfian Wicaksono, Janak Bechar, James A. Covington and Joseph Hardwicke

Biosensors 2020, 10(3), 19; https://doi.org/10.3390/bios10030019 - 29 Feb 2020

Cited by 14 | Viewed by 5709

Abstract

Surgical site infection represents a large burden of care in the National Health Service. Current methods for diagnosis include a subjective clinical assessment and wound swab culture that may take several days to return a result. Both techniques are potentially unreliable and result [...] Read more.

Surgical site infection represents a large burden of care in the National Health Service. Current methods for diagnosis include a subjective clinical assessment and wound swab culture that may take several days to return a result. Both techniques are potentially unreliable and result in delays in using targeted antibiotics. Volatile organic compounds (VOCs) are produced by micro-organisms such as those present in an infected wound. This study describes the use of a device to differentiate VOCs produced by an infected wound vs. colonised wound. Malodourous wound dressings were collected from patients, these were a mix of post-operative wounds and vascular leg ulcers. Wound microbiology swabs were taken and antibiotics commenced as clinically appropriate. A control group of soiled, but not malodorous wound dressings were collected from patients who had a split skin graft (SSG) donor site. The analyser used was a G.A.S. GC-IMS. The results from the samples had a sensitivity of 100% and a specificity of 88%, with a positive predictive value of 90%. An area under the curve (AUC) of 91% demonstrates an excellent ability to discriminate those with an infected wound from those without. VOC detection using GC-IMS has the potential to serve as a diagnostic tool for the differentiation of infected and non-infected wounds and facilitate the treatment of wound infections that is cost effective, non-invasive, acceptable to patients, portable, and reliable. Full article

(This article belongs to the Special Issue Noninvasive Early Disease Diagnosis)

► Show Figures

Figure 1

14 pages, 2754 KiB

Open AccessArticle

A Disposable Passive Microfluidic Device for Cell Culturing

by Francesco Guzzi, Patrizio Candeloro, Maria Laura Coluccio, Costanza Maria Cristiani, Elvira Immacolata Parrotta, Luana Scaramuzzino, Stefania Scalise, Elisabetta Dattola, Maria Antonia D’Attimo, Giovanni Cuda, Ernesto Lamanna, Lucia Carmela Passacatini, Ennio Carbone, Ulrich Krühne, Enzo Di Fabrizio and Gerardo Perozziello

Biosensors 2020, 10(3), 18; https://doi.org/10.3390/bios10030018 - 29 Feb 2020

Cited by 12 | Viewed by 5070

Abstract

In this work, a disposable passive microfluidic device for cell culturing that does not require any additional/external pressure sources is introduced. By regulating the height of fluidic columns and the aperture and closure of the source wells, the device can provide different media [...] Read more.

In this work, a disposable passive microfluidic device for cell culturing that does not require any additional/external pressure sources is introduced. By regulating the height of fluidic columns and the aperture and closure of the source wells, the device can provide different media and/or drug flows, thereby allowing different flow patterns with respect to time. The device is made of two Polymethylmethacrylate (PMMA) layers fabricated by micro-milling and solvent assisted bonding and allows us to ensure a flow rate of 18.6 μL/h - 7%/day, due to a decrease of the fluid height while the liquid is driven from the reservoirs into the channels. Simulations and experiments were conducted to characterize flows and diffusion in the culture chamber. Melanoma tumor cells were used to test the device and carry out cell culturing experiments for 48 h. Moreover, HeLa, Jurkat, A549 and HEK293T cell lines were cultivated successfully inside the microfluidic device for 72 h. Full article

► Show Figures

Figure 1

10 pages, 1132 KiB

Open AccessArticle

Design of Multiplex Lateral Flow Tests: A Case Study for Simultaneous Detection of Three Antibiotics

by Anastasiya V. Bartosh, Dmitriy V. Sotnikov, Olga D. Hendrickson, Anatoly V. Zherdev and Boris B. Dzantiev

Biosensors 2020, 10(3), 17; https://doi.org/10.3390/bios10030017 - 27 Feb 2020

Cited by 19 | Viewed by 7453

Abstract

The presented study is focused on the impact of binding zone location on immunochromatographic test strips on the analytical parameters of multiplex lateral flow assays. Due to non-equilibrium conditions for such assays the duration of immune reactions influences significantly the analytical parameters, and [...] Read more.

The presented study is focused on the impact of binding zone location on immunochromatographic test strips on the analytical parameters of multiplex lateral flow assays. Due to non-equilibrium conditions for such assays the duration of immune reactions influences significantly the analytical parameters, and the integration of several analytes into one multiplex strip may cause an essential decrease of sensitivity. To choose the best location for binding zones, we have tested reactants for immunochromatographic assays of lincomycin, chloramphenicol, and tetracycline. The influence of the distance to the binding zones on the intensity of coloration and limit of detection (LOD) was rather different. Basing on the data obtained, the best order of binding zones was chosen. In comparison with non-optimal location the LODs were 5–10 fold improved. The final assay provides LODs 0.4, 0.4 and 1.0 ng/mL for lincomycin, chloramphenicol, and tetracycline, respectively. The proposed approach can be applied for multiplexed assays of other analytes. Full article

► Show Figures

Graphical abstract

11 pages, 5651 KiB

Open AccessArticle

Self-assembly Synthesis of Molecularly Imprinted Polymers for the Ultrasensitive Electrochemical Determination of Testosterone

by Kai-Hsi Liu, Danny O’Hare, James L. Thomas, Han-Zhang Guo, Chien-Hsin Yang and Mei-Hwa Lee

Biosensors 2020, 10(3), 16; https://doi.org/10.3390/bios10030016 - 27 Feb 2020

Cited by 18 | Viewed by 5072

Abstract

Molecularly imprinted polymers (MIPs) can often bind target molecules with high selectivity and specificity. When used as MIPs, conductive polymers may have unique binding capabilities; they often contain aromatic rings and functional groups, which can undergo π-π and hydrogen bonding interactions with similarly [...] Read more.

Molecularly imprinted polymers (MIPs) can often bind target molecules with high selectivity and specificity. When used as MIPs, conductive polymers may have unique binding capabilities; they often contain aromatic rings and functional groups, which can undergo π-π and hydrogen bonding interactions with similarly structured target (or template) molecules. In this work, an electrochemical method was used to optimize the synthetic self-assembly of poly(aniline-co-metanilic acid) and testosterone, forming testosterone-imprinted electronically conductive polymers (TIECPs) on sensing electrodes. The linear sensing range for testosterone was from 0.1 to 100 pg/mL, and the limit of detection was as low as ~pM. Random urine samples were collected and diluted 1000-fold to measure testosterone concentration using the above TIECP sensors; results were compared with a commercial ARCHITECT ci 8200 system. The testosterone concentrations in the tested samples were in the range of 0.33 ± 0.09 to 9.13 ± 1.33 ng/mL. The mean accuracy of the TIECP-coated sensors was 90.3 ± 7.0%. Full article

► Show Figures

Figure 1

16 pages, 1408 KiB

Open AccessReview

Food Sensing: Detection of Bacillus cereus Spores in Dairy Products

by Jasmina Vidic, Carole Chaix, Marisa Manzano and Marc Heyndrickx

Biosensors 2020, 10(3), 15; https://doi.org/10.3390/bios10030015 - 25 Feb 2020

Cited by 69 | Viewed by 15325

Abstract

Milk is a source of essential nutrients for infants and adults, and its production has increased worldwide over the past years. Despite developments in the dairy industry, premature spoilage of milk due to the contamination by Bacillus cereus continues to be a problem [...] Read more.

Milk is a source of essential nutrients for infants and adults, and its production has increased worldwide over the past years. Despite developments in the dairy industry, premature spoilage of milk due to the contamination by Bacillus cereus continues to be a problem and causes considerable economic losses. B. cereus is ubiquitously present in nature and can contaminate milk through a variety of means from the farm to the processing plant, during transport or distribution. There is a need to detect and quantify spores directly in food samples, because B. cereus might be present in food only in the sporulated form. Traditional microbiological detection methods used in dairy industries to detect spores show limits of time (they are time consuming), efficiency and sensitivity. The low level of B. cereus spores in milk implies that highly sensitive detection methods should be applied for dairy products screening for spore contamination. This review describes the advantages and disadvantages of classical microbiological methods used to detect B. cereus spores in milk and milk products, related to novel methods based on molecular biology, biosensors and nanotechnology. Full article

► Show Figures

Figure 1

Journal Menu

Journal Browser

Biosensors, Volume 10, Issue 3 (March 2020) – 15 articles

Further Information

Guidelines

MDPI Initiatives

Follow MDPI