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Abstract

Microbial screening is a primary concern for many products. Traditional techniques based on standard plate count (SPC) are accurate, but time consuming. Furthermore, they require a laboratory environment and qualified personnel. The impedance technique (IT) looking for changes in the electrical characteristics of the sample under test (SUT) induced by bacterial metabolism represents an interesting alternative to SPC since it is faster (3-12h vs. 24-72 h for SPC) and can be easily implemented in automatic form. With this approach, the essential parameter is the time for bacteria concentration to reach a critical threshold value (about 10(7) cfu mL(-1)) capable of inducing significant variations in the SUT impedance, measured by applying a 100 mV peak-to-peak 200 Hz sinusoidal test signal at time intervals of 5 min. The results of this work show good correlation between data obtained with the SPC approach and with impedance measurements lasting only 3h, in the case of highly contaminated samples (10(6) cfu mL(-1)). Furthermore, this work introduces a portable system for impedance measurements composed of an incubation chamber containing the SUT, a thermoregulation board to control the target temperature and an impedance measurement board. The mix of cheap electronics and fast detection time provides a useful tool for microbial screening in industrial and commercial environments.

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... Several studies have reported that cellular detection, quantification, and monitoring can be accurately monitored by means of its biological electrical impedance (BioZ) [1][2][3][4][5][6][7][8][9][10] in different environments, in vivo or ex vivo experiences. One example of such work is the paper presented by Pop et al. (2013) [2], where blood hematocrit (HCT) was continuously in vivo monitored in the human right atrium by a dedicated central venous catheter equipped with an impedance measuring device. ...
... Dweik et al. (2012) [9] demonstrated the detection of E. coli where bacterial presence was rapidly detected by measuring the antibody-antigen bonding by impedance analysis between 100 Hz and 10 MHz. Also, in the work developed by Grossi et al. (2010) [10], the quantity of bacteria during a culture process was detected by impedance measured at 200 Hz sinusoidal with a 100 mV peak-topeak signal. Furthermore, other studies have reported the detection of cell-derived microparticles [11] and insulin in blood serum [12] based on an IS technique. ...
... Dweik et al. (2012) [9] demonstrated the detection of E. coli where bacterial presence was rapidly detected by measuring the antibody-antigen bonding by impedance analysis between 100 Hz and 10 MHz. Also, in the work developed by Grossi et al. (2010) [10], the quantity of bacteria during a culture process was detected by impedance measured at 200 Hz sinusoidal with a 100 mV peak-topeak signal. Furthermore, other studies have reported the detection of cell-derived microparticles [11] and insulin in blood serum [12] based on an IS technique. ...
Chapter
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In this chapter, the development of a point-of-care device for bio-medical applications has been discussed. Our main objective is to research new electronic solutions for the detection, quantification, and monitoring of important biological agents in medical environments. The proposed systems and technologies rely on label-free disposable sensors, with portable electronics for user-friendly, low-cost solutions for medical disease diagnosis, monitoring, and treatment. In this chapter, we will focus on a specific point-of-care device for cellular analysis, applied to the case of anemia detection and monitoring. The methodology used for anemia monitoring is based on hematocrit measurement directly from whole blood samples by means of impedance analysis. The designed device is based on straightforward electronic standards for low power consumption and low-cost disposable sensor for low volume samples, resulting in a robust and low power consumption device for portable monitoring purposes of anemia. The device has been validated through different whole blood samples to prove the response, effectiveness, and robustness to detect anemia.
... Different commercial instruments exist that are based on the impedance technique: Bactometer by Vitek Systems Ltd (Basingstoke, UK), Malthus by Malthus Instruments Ltd (Bury, UK), Bac Trac by Sy-Lab (Purkensdorf, Austria) and RABIT by Don Whitley Scientific (Shipley, UK). Recently, an embedded portable biosensor system based on the impedance technique [13] has been proposed that is particularly suited for in-situ bacterial screening. All the presented instruments feature stainless steel or platinum as the electrodes material, the inter-electrodes distance is in the mm range and a capacity of 3 to 10 ml for the sample under test (SUT) is used. ...
... In this work we test a microfabricated sensor, featuring small (1 mm 2 ) gold electrodes separated by 100 ìm, and compare its performance with those of the aforementioned instruments. The results indicate that, even if response time is comparable with that obtained in [13] , the microfabricated sensor features a broader working frequency range, thus allowing for more realible measurements. ...
... The results show how the proposed microfabricated sensor can broaden the working frequency range. In fact, all the benchtop instruments discussed in the introduction as well as the portable biosensor system in [13] are characterized by a maximum working frequency not higher than 10 kHz, while the proposed sensor broadens this limit to over 1 MHz, with benefits in terms of higher signal-to-noise ratio, more stable baseline and more accurate DT calcu- lation. ...
Conference Paper
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Control of water microbial content is of great importance to guarantee the absence of pathogens. The bacterial concentration is traditionally measured by standard plate count, a technique that is reliable but characterized by long response time and must be performed in microbiology laboratory with the aid of trained personnel. The impedance technique, that measures the bacterial concentration by analyzing the sample electrical characteristics, is competitive with the standard technique since features shorter detection times (3 – 12 hours vs. 24 – 72 hours of plate count) and can be easily realized in automatic form. The present work shows a microfabricated sensor featuring gold electrodes (1mm2 area separated by 100μm) used to measure the concentration of a wild type coliform strain (isolated in river water). The presented sensor is capable to detect high microbial concentration (106 cfu/ml) in relatively short time (225 minutes) and, compared to other impedance biosensors, has the advantage to properly work at higher frequencies (extending the working frequency range to over 1 MHz) with benefits for measure reliability.
... Thus the requirement to correctly choose the incubation temperature needed in order to minimize differences in generation times of different microbial species possibly present in the sample under test. Another paper [13] describes a portable biosensor system for bacterial concentration detection based on the IT, that is fully automated and requires no particular knowledge of microbiological techniques, thus making it particularly suitable for microbial screening in industrial or commercial environments. Moreover, the use of low-cost electronics makes it highly competitive in terms of cost (few hundreds US Dollars). ...
... The biosensor system based on impedance measurement created by Carpigiani [13][14][15], was used to determine the bacterial load in the icecream mix. At first the ice-cream mix without inoculum, then samples inoculated with known bacterial loads of E. coli ATC11229 ranging from 10 1 to 10 10 cfu/ml, were analyzed with the portable biosensor in order to find the electric response of the sample. ...
... The use of "Φ" angle as parameter related to bacterial load allowed analysis of ice cream mix samples within a wide range of E. coli bacterial concentrations. Previous studies reported two different DT values calculated for the capacity curve and for the resistance curve, respectively, and only in a second time these values were compared to each other [13][14][15]. The possibility to work with a single curve resulting from the two variables considered in the system allows to have a reliable response and facilitates the final measurement operations. ...
Article
Full-text available
One of the primary focuses of the food industry is providing products compliant with safety standards. The microbiological analysis helps in the identification of the presence of pathogen microorganisms in the food. The analysis with Agar Plate is the classic method. This approach guarantees a high accuracy, but it needs a long detection time (twenty-four to forty-eight hours), beyond high costs and skilled technician. In recent times have been proposed many different methods to have a faster response, and between them there is the impedance method. One of its features is that it is fast, in fact it requires between three to fourteen hours to obtain a reliable measurement. The system is accurate, and suitable to be executed automatically. To test this method has been used UHT Ice Cream Mix. A known volume of mix has been inoculated with increasing percentage of cultures of E. coli. The measurement of the impedance of the inoculated mix has been done by an electronic board designed for the application, and by applying a sinusoidal voltage to the test tube. The signal was digitally generated by the microprocessor, and supplied externally through a D.A. converter. The signal was then filtered to delete from its spectrum the high frequency components typical of the digitally generated signals. The data obtained from impedance instrument showed a reliable correspondence with those from the plate count. By working in less time compared to traditional methods, this tool is well suited for in-situ preliminary analysis in commercial and professional foodservice environment.
... Research in environmental monitoring has developed many types of sensors for the screening of microorganisms [9], [10], [11] as well as for the detection of toxic pollutants in water [12], [13]. Recently, the authors have proposed an embedded system that is highly competitive with SPC in terms of measuring time (3–12 h depending on the sample contamination) and features user-friendly procedures, with no need of a laboratory environment, that allow its application for in-situ determination of bacterial concentration [14]. This system detects bacterial concentration in liquid and semi-liquid samples by using the impedance technique [15]. ...
... An improved version of the portable system discussed in [14] has been used to monitor bacterial concentration of water samples taken from rivers, waste waters and watercourses in the surroundings of Bologna (Italy). ...
... The system is composed of two electronic boards: one for measuring the SUT electrical parameters (also suited for DT evaluation), while the other is a thermoregulation board controlling the SUT temperature with oscillations lower than 0.15 °C. As discussed in [14] and [17], sample temperature must be maintained as stable as possible to avoid fluctuations of the electrical parameters that affect the measurement reliability. ...
Article
Full-text available
Bacterial screening is very important in water environmental monitoring, because the presence of dangerous pathogens can seriously endanger human health. Microbial concentration detection is performed by standard plate count technique, which is reliable but is characterized by long response time and is not suitable to be implemented in automatic form. Based on impedance measurements, this paper presents a portable sensor implemented as an electronic embedded system featuring disposable measurement cells, which is suitable of measuring bacterial concentration in water samples. The system provides a much faster response than standard technique (3-12 h depending on the contamination level versus 24-72 h of the standard technique) and can be used for an in situ microbial test rather than taking samples to a laboratory for analysis. Water samples from different sources (such as rivers, wastewaters, watercourses) are tested using the presented system. Enriched medium is added to the sample to favor bacterial growth. Three different media are tested (Lauria Bertani, Mc Conkey Broth, and Lactose Broth) and data are compared with microbial growth rate and selectivity toward bacterial group (e.g., coliforms). The obtained experimental data show good correlation with the plate count technique.
... In this context, food characterization by means of electrical measurements easily implementable in automatic form plays a crucial role and a number of significant examples can be mentioned: detection of water and lipid content in meat [1], dilution factor in apple puree [2], determination of pH, acidity and hardness in yogurt [3], quality control of vegetable oils [4]. In particular, as far as dairy products are considered, techniques have been proposed for the characterization of milk content [5] [6] [7], detection of mastitis in raw milk samples [8] [9], measurement of microbial concentration in milk [10] and icecream [11] [12] [13]. A different, though related, application is automatic product recognition to optimize machine setting when dealing with different versions of the same basic product needing specific processing parameters. ...
... Measures have been carried out at two different temperatures (4 °C and 35 °C). The two temperatures have been chosen according to the following rules: 4 °C is the standard temperature the icecream mixes are stored while 35 °C is the temperature used in a microbial biosensor system recently developed by the authors [13]. Thus, the choice has been made with the idea of a future implementation in industrial environment as a sensor integrated in the tank of the storing machine (4 °C) or in a separate chamber controlled with the embedded biosensor system (35 °C). ...
Article
Electrical characterization of products is gaining increasing interest in the food industry for quality monitoring and control. In particular, this is the case in the ice-cream industry, where machines dedicated to store ice-cream mixes are programmed “ad hoc” for different groups of products. To this purpose, the present work shows that essential product classification (discrimination between milk based and fruit based ice-cream mixes) can be done by means of a technique based on the measurements of non-linear response in the electrical behavior of the electrode-electrolyte interface. The addition of pH measurements allows to further reach the three parts classification occasionally required for advanced applications. The proposed idea is validated by means of measurements on 21 ice-cream mixes, different for producers and composition.
... Impedentiometric methods offer another strategy for bacterial pathogen detection [11,12]. A portable sensor implemented as an electronic embedded system featuring disposable measurement cells already described by Grossi et al. was used with the aim of evaluating the suitability and the sensitivity of this device in the detection of E. coli contamination in transitional waters [11,12]. ...
... Impedentiometric methods offer another strategy for bacterial pathogen detection [11,12]. A portable sensor implemented as an electronic embedded system featuring disposable measurement cells already described by Grossi et al. was used with the aim of evaluating the suitability and the sensitivity of this device in the detection of E. coli contamination in transitional waters [11,12]. ...
Article
Full-text available
Monitoring of bacterial pathogens is important for marine environmental protection, because the presence of these microorganisms can be a serious risk for human health. For this reason, a portable sensor implemented as an electronic embedded system featuring disposable measurement cells was used to evaluate the ability and sensitivity of detection of Escherichia coli(E. coli) as an indicator of fecal pollution in transitional environments and a water sample added with E. coli(10^2 CFU/mL) was assayed. The first result obtained from the laboratory experiment seems promising for the determination of E. coliin environmental samples, though further improvements will be needed for the field application of this sensor in marine and brackish waters.
... Under a microscope, bacteria cells are amazingly alive and perform a whole host of physiological functions, namely, multiplication through cell division, searching for resources by chemotaxis (5)(6)(7)(8)(9), controlling water pressure by exchange of ions (through the osmoregulatory system) (10)(11)(12), etc. However, since the introduction of the plate counting method almost 130 y ago, traditional viability assays, such as impedance microbiology, rely on cell multiplication to differentiate between dead and live cells (13)(14)(15)(16)(17)(18)(19). Cell division time can vary from hours to weeks depending on the bacteria type (e.g., 10-20 min for Escherichia coli vs. 15-16 h for Mycobacterium tuberculosis), which makes fast, real time detection of cells challenging, especially at low concentration. ...
... These techniques can be broadly divided into growth-based vs. nongrowth-based assays. Growth-based techniques [such as colony counting (14), impedance microbiology (16)(17)(18)(19), monitoring the resonance frequency (32), etc.] rely on cell division to reach a threshold level so that the signal becomes detectable. The typical incubation time can vary from hours to days depending on the cell type and initial cell concentration. ...
Article
Significance Conventional bacterial viability assays rely on cell multiplication until they are detectable by optical, electrical, or other sensors. Consequently, the assay time of classical growth-based techniques ranges from hours to weeks depending on bacteria type. In contrast, we present a fundamentally different paradigm based on bacterial osmoregulation to identify viable cells in minutes. Our label-free platform relies on two key advances: ( i ) the fact that osmoregulation is as universal as cell division and ( ii ) the ability to create a microliter-sized environment on a specially designed multifunctional structure. Our contribution advances the field with a collage of ideas from diverse disciplines (e.g., biology, microfluidics, surface energetics, and impedance spectroscopy) and therefore, will attract a broad audience of physicists, material scientists, biologists, and engineers.
... Biosensors allowing a real-time and label-free monitoring are proposed in the literature. They are based on optical devices, impedance spectroscopy, dielectric characterization or surface acoustic waves [6][7][8][9]. Among them, Electrical Impedance Spectroscopy (EIS) is a well-established method which operates from 10 mHz to 100 kHz to analyse interfacial properties between metallic electrodes and biological matter [10][11][12]. ...
Article
Full-text available
Bacterial biofilms have a significant economic and health impact in many different domains. In such films, the extracellular matrix prevents the diffusion of biocides, so antibiotic treatments require a concentration 500 to 1000 times higher than that used to eliminate the same bacteria when present as planktonic stage. Early detection of biofilms is therefore essential for effective eradication. In this paper, we present the development of a real-time and label-free radiofrequency biosensor dedicated to the monitoring of bacteria and biofilm growth. Its principle relies on an open-ended coaxial probe sensitive to the variation of the electrical conductivity of the probed medium in the microwave range. As shown, between 0.3 and 1 GHz, the high sensitivity of the method (2.3 × 10⁴ CFU/mL) highlights the biofilm growing at the early stage of its formation. To demonstrate experimentally such effects, two model bacteria, Vibrio natriegens and P. aeruginosa, are considered. The proposed method should therefore be considered as a promising technique for biofilm monitoring in batch bioreactors or flow cells experiments.
... More importantly, the output voltage, also from a custom-made system, was DC biased which is often incompatible with biomolecular detection. There are also customdesigned impedance detection systems using integrated chips (ICs) (Chuang et al., 2014;Grossi et al., 2010), but few of them reported how to remove the phase lead or lag introduced by components connected in the signal path of their devices. In another work, a dual lock-in amplifier-based POC impedance acquisition system was used to test blood coagulation. ...
Article
Specific detection of protein biomarkers has a wide range of applications in areas such as medical science, diagnostics, and pharmacology. Quantitative detection of protein biomarkers in biological media, such as serum, is critically important in detecting disease or physiological malfunction, or tracking disease progression. Among various detection methods, electrical detection is particularly well suited for point-of-care (POC) specific protein detection, being of low cost, light weight and small form factor. A portable system for sensitive and quantitative detection of protein biomarkers will be highly valuable in controlling and preventing diseases outbreaks. Recently, an alternating current electrokinetic (ACEK) capacitive sensing method has been reported to demonstrate very promising performance on rapid and sensitive detection of specific protein from serum. In this work, a low cost and portable analyzer with good accuracy is developed to use with ACEK capacitive sensing to produce a true POC technology. The development of a board-level capacitance readout system is presented, as well as the adaption of the protocol for use with ACEK capacitive sensing. Results showed that the developed system could achieve a limit of detection of 10 ng/mL, comparable to a sophisticated benchtop instrument. With its small size and light-weight comparable to a smart phone, the developed system is ready to be applicable as POC diagnostics. Further, the readout system can be readily expanded for multichannel monitoring and telecommunication capabilities.
... Recently, our research group has developed an embedded portable biosensor system [10] based on the impedance technique that is particularly suited for insitu microbial measurements of liquid and semi-liquid samples. The system has been successfully tested with different types of samples such as ice-cream [11,12], raw milk [13], beer [14] and water [15]. In this paper we present a data transformation algorithm for the measured data that allows an easy and efficient calculation of DT and can be implemented in any sensor system that performs measures of bacterial concentration based on the impedance technique. ...
Article
Bacterial contamination is a very important issue in different fields such as food quality control and environmental monitoring. High values of bacterial concentration and/or the presence of pathogenic bacterial strains can seriously endanger human health, thus microbial concentration must be regularly screened to meet national and international regulations. Bacterial concentration is measured by Standard Plate Count technique, a reliable and accurate method that is however characterized by long time response (24–72 hours) and the need to be performed in a laboratory environment by skilled personnel. Our research group has recently developed an embedded portable biosensor system that is competitive with the standard technique in terms of response time and can be easily used for in-situ measurements by users with no microbiology knowledge. In this paper we discuss an algorithm for the transformation of the biosensor measured data that proves to be accurate and easy to be implemented. The algorithm is based on the calculation of the first and second time derivatives of the measured electrical parameters and the results show good correlation (R 2 = 0.829) between the bacterial concentration estimated with the biosensor and that measured by the standard technique.
... Biosensor technologies have been developed with amperometry, piezoelectricity, and optical waveguide, Scognamiglio, et al. have designed and developed one miniaturized multifunction biosensor array system for the detection of endocrine disrupting chemicals which equipped with optical excitation and detection, current measurement and flow control systems [13]. Grossi et al. have developed an embedded portable biosensor system for bacterial concentration [14]. Schöning et al. have fabricated a flow-injection system with dual amperometric and potentiometric organophosphorus pesticides (OP) biosensors for the simultaneous and rapid measurements of OP compounds was described [15]. ...
Article
Full-text available
In this paper, a design of portable pesticide residues detection instrument was presented based on an impedance immunosensor. The immunosensor exploited the novel multilayer films based on Au nanoparticles (AuNPs) and polyaniline/carboxylated multiwall carbon nanotubes-chitosan nanocomposite (PANI/MWCNTs/CS). The detection principle of the instrument was based on the electrochemical characteristic of antigen-specific antibody immune response. With a stronger signal generated from the antigen-specific antibody immune response, the signal detection circuit was designed more easily. We integrated immunosensor and signal detection circuit to fabricate pesticide residues detection instrument. This proposed instrument could realize the rapid detection of pesticide residues in fruits and vegetables with automatic data processing and presented the result on the spot. The impedance test error was less than 5 %. The results showed that the proposed instrument had a good consistence compared with the traditional analytical methods. Thus, it would be a promising rapid detection instrument for pesticide residues in agricultural products.
... The medium capacitance could indicate the antibiotic susceptibility and primary effect (bacteriostatic and bactericidal) of the tested E. coli in 4 hours. Grossi et al. (2010) designed a portable impedance detection system for detecting the resistance and capacitance of bacterial suspensions in PoC settings [100]. They were able to detect bacterial concentrations of >10 6 CFU/mL within 3 hours. ...
Thesis
Pathogenic bacteria are biological cells that can cause infectious diseases. Antimicrobial resistance (AMR) is a phenomenon whereby pathogenic bacteria can survive even after exposure to previous effective antibiotics. If necessary action is not taken, AMR is predicted to be the leading cause of mortality. Antibiotic efficiency against bacteria is determined by antimicrobial susceptibility testing (AST). Conventional AST methods are time-consuming because they determine growth after many doubling times and each doubling time is at least 20 minutes. The lack of time efficient diagnostic tools accelerates AMR because antibiotics are usually prescribed without the susceptibility test results. This research describes the development of three miniaturised AST systems that are fast-test, low-cost and high-sensitivity. The first detection system is a dielectrophoresis (DEP) enhanced optical system that can detect the presence of β-lactamases from a minimum of 103 colony-forming unit (CFU)/mL bacterial sample in 1 hour. The bacteria in a test sample were first enriched by filtering followed by DEP concentration. Then, the presence of β-lactamases was determined through a colour change using the dye nitrocefin, a β-lactam analogue, in an optical chip. The sensitivity of the DEPenhanced optical system is four orders of magnitude better than conventional plate-based assays and the clinical selectivity is 100%. The second detection system is a miniature pH system that can detect the presence of βlactamases from a low concentration sample of 105 CFU/mL bacterial sample in 1 hour. An iridium oxide pH sensor is used to detect the pH reduction due to β-lactam antibiotic hydrolysis. This pH system is robust, simple and suitable for application in point-of-care situations. The sensitivity of the pH system is two orders of magnitude better than conventional plate-based assays and the clinical selectivity is 75%. The third detection system measures the impedance of a suspension of bacteria exposed to antibiotics to infer growth rate and susceptibility, which can indicate the minimum inhibitory concentration (MIC) of β-lactam antibiotics, ciprofloxacin, gentamicin, ceftazidime, colistin and doxycycline for various species of bacteria. The MIC detected by the impedance system can be done in 1 hour and shows >90% concordance with conventional broth dilution method that takes over 20 hours. In summary, this thesis describes three miniaturized, AST systems aimed at rapid diagnosis of the presence of β-lactamases or broadband antibiotic susceptibility within 1 hour with low cost and high sensitivity.
... The capacitive component of the impedance is also a suitable indicator to reliably detect products featuring a bacteria concentration that exceeds the limits allowed by the law (Grossi et al., 2008, 2009). This method has recently been developed as an fast, cheap, and embedded portable biosensor system composed of an incubation chamber, including the sample under test, and two electronic boards: one dedicated to measuring the sample electrical characteristics, the other controlling the sample temperature, fixed at a value suitable to enhance bacterial growth (Grossi et al., 2010). Electrical impedance has also been used for automatic ice cream characterization, which is of special industrial importance, where machines dedicated to store ice-cream mixes are programmed ''ad hoc'' for different groups of products. ...
Article
There is an increasing demand of the food industries and research institutes to have means of measurement allowing the characterization of foods. Ice cream, as a complex food system, consists of a frozen matrix containing air bubbles, fat globules, ice crystals, and an unfrozen serum phase. Some deficiencies in conventional methods for testing this product encourage the use of alternative techniques such as rheometry, spectroscopy, X-ray, electro-analytical techniques, ultrasound, and laser. Despite the development of novel instrumental applications in food science, use of some of them in ice cream testing is few, but has shown promising results. Developing the novel methods should increase our understanding of characteristics of ice cream and may allow online testing of the product. This review article discusses the potential of destructive and non-destructive methodologies in determining the quality and characteristics of ice cream and similar products. Copyright © 2015. Published by Elsevier Ltd.
... Single cell IA also resulted in an effective method for cell counting, discrimination, behaviour analysis and growth of bacteria [35,86,87]. Impedance microbiology measures the variations in electrical impedance of a culture medium or a reactive solution that results from the bacterial growth [55,88]. Previous studies have reported the use of this technique to detect and quantify different species of bacteria [14,89,90] such as Salmonella [91][92][93], E. coli [94,95], Listeria innocua and Listeria monocytogenes [96], Staphylococcus aureus [97], Enterococcus faeccalis [98], coliforms, Listeria spp., and L. monocytogenes [55]. ...
Article
Full-text available
Bacteria concentration and detection is time-consuming in regular microbiology procedures aimed to facilitate the detection and analysis of these cells at very low concentrations. Traditional methods are effective but often require several days to complete. This scenario results in low bioanalytical and diagnostic methodologies with associated increased costs and complexity. In recent years, the exploitation of the intrinsic electrical properties of cells has emerged as an appealing alternative approach for concentrating and detecting bacteria. The combination of dielectrophoresis (DEP) and impedance analysis (IA) in microfluidic on-chip platforms could be key to develop rapid, accurate, portable, simple-to-use and cost-effective microfluidic devices with a promising impact in medicine, public health, agricultural, food control and environmental areas. The present document reviews recent DEP and IA combined approaches and the latest relevant improvements focusing on bacteria concentration and detection, including selectivity, sensitivity, detection time, and conductivity variation enhancements. Furthermore, this review analyses future trends and challenges which need to be addressed in order to successfully commercialize these platforms resulting in an adequate social return of public-funded investments.
... First, the experimental set-up shown in Fig. 1(a) has been used to test the feasibility of oil concentration measurement using the conductivity-based titration of interest for this work. A 50 ml polypropylene vial featuring a couple of cap-shaped stainless steel electrodes is used to host the SUT and its characterization during the titration procedure by means of Electrical Impedance Spectroscopy (EIS), a powerful technique used in different applications, such as bacterial concentration measurements in different types of samples [24][25][26][27][28][29][30][31]; analysis of human body composition [32][33][34][35]; quality analysis of food products [36][37][38][39]; corrosion monitoring of metallic surfaces in contact with acid electrolytes [40][41][42][43]. ...
Article
Most Metalworking Fluids (MWFs), widely used for cooling and lubrication, consist of oils diluted in water in concentration ranging from 1% to 10%. To guarantee good performance and reliability of both machines and processes, oil concentration should be maintained (approximately) constant, hence also measured at regular intervals to compensate for significant deviations from the optimal value. The official technique to measure oil concentration in MWFs is titration with 0.5M HCl solution and endpoint detection obtained measuring the sample pH. Such a method is accurate and substantially insensitive to sample contamination, but must be carried out in a laboratory, while fast, inexpensive and in-situ measurements would be desirable for effective process and machine control. This paper presents a system to measure oil concentration in MWFs that is new in that: a) titration is made automatic using a stepper motor; b) the end-point is detected by means of electrical conductance measurements. Experimental results show a very good correlation (R² = 0.9793) between the oil concentrations of prepared solutions and those measured with the proposed technique, while the presented system is suitable for in-situ operation within working environment.
... Recently, research in IM was mainly aimed at reducing instrument dimensions (to allow automatic and in situ measurements) and improving measurement performance (in particular, lowering the response time). Grossi et al. (2010Grossi et al. ( , 2013a) designed a portable biosensor to measure bacterial concentration in liquid and semiliquid media that includes an incubation chamber (featuring stainless steel electrodes, heating resistances and a temperature sensor for thermoregulation) and two electronic boards, connected to a PC via RS-232 for data analysis and filing. A Telit GT 863-PY module integrated into the system allows wireless data transmission to remote hosts. ...
Article
Full-text available
Electrical impedance spectroscopy (EIS), in which a sinusoidal test voltage or current is applied to the sample under test to measure its impedance over a suitable frequency range, is a powerful technique to investigate the electrical properties of a large variety of materials. In practice, the measured impedance spectra, usually fitted with an equivalent electrical model, represent an electrical fingerprint of the sample providing an insight into its properties and behavior. EIS is used in a broad range of applications as a quick and easily automated technique to characterize solid, liquid, semiliquid, organic as well as inorganic materials. This paper presents an updated review of EIS main implementations and applications.
... The official procedure for bacterial concentration measurement is the Standard Plate Count (SPC) technique, which is reliable and accurate but requires long time (from 24 to 72 hours) and is a laboratory based method that must be carried out by trained personnel. As an alternative, the Impedance Technique (ImpTech) is highly competitive with SPC since it features faster response time (from 2 to 14 hours depending on the type of Sample Under Test – SUT) and is suitable to be performed with electronic systems, to be " embedded " in industrial machineries or implemented as portable instruments for in-situ measurements (Grossi et al., 2010). ImpTech essentially works as follows (Eden and Eden, 1984): the SUT is stored at a temperature suitable for bacterial growth and its electrical characteristics are measured at regular time intervals. ...
Article
Full-text available
Metal Working Fluids (MWFs) are commonly used in manufacturing to cool and lubricate mechanical machines. However, it is well known that MWFs represent a suitable environment for the proliferation of bacteria as well as molds and yeasts. This, in turn, represents a problem, since microbial contamination can seriously degrade MWFs’ properties, with adverse effects on lubrication efficiency and, under particular circumstances, even on the health of exposed workers. Bacterial growth is often counteracted by adding biocide to MWFs. This, however, poses the problem of the appropriate choice of biocide concentration and frequency of use, and to this purpose the microbial concentration needs to be measured. In general, bacterial concentration is determined by Standard Plate Count technique, a reliable method that, however, requires long response time (24-72 hours) and must be performed in a laboratory environment by trained personnel. As a viable alternative, the Impedance Technique (ImpTech) detects bacterial concentration by analyzing the electrical characteristics of the sample under test, with the advantages of shorter response time and in-situ measurements. In this context, we have investigated the possible use of the ImpTech to measure the bacterial concentration in MWFs’ samples taken from different metalworking plants. The application of such a technique to this kind of fluids is new and the obtained results show that high bacterial concentrations can be reliably measured with time response in 4-6 hours. Since it can be implemented by means of low-cost electronic embedded systems, the ImpTech can be used to automatically and periodically test the state of MWFs in production environments, with important advantages, such as, in particular: minimum and optimal use of biocides, hence lower costs and longer MWF lifetime; optimal performance of MWFs; minimal disposure of worn-out MWFs, with beneficial effects on the ambient.
... However, these measurement systems are not suitable for on-the-spot applications, so many efforts have been made to minimize the instruments [3]. Grossi et al. [49] developed an embedded portable biosensor system for the determination of bacterial concentration. This system is composed of an incubation chamber, containing the sample under test, and two electronic boards: one dedicated to measuring the sample electrical characteristics, and the other to controlling the sample temperature, fixed at a value suitable to enhance bacterial growth. ...
Chapter
Electrochemical and electrical impedance has been shown as powerful techniques to be applied in the food industry and have been used for monitoring and detecting pathogens and drug residues in foodstuffs. Electrochemical impedance spectroscopy (EIS) has demonstrated its usefulness to investigate the fouling of these materials. It is a powerful electrochemical technique capable of detecting small changes occurring at the solution-electrode interface. A number of authors have exploited EIS for pathogen detection, by monitoring either the changes in the medium conductivity caused by bacterial growth/metabolism, or the changes in the solution-electrode interface due to microorganism nonspecific adsorption or specific capture onto the sensor surface. This chapter presents examples to show that impedance sensors and biosensors constitute an excellent tool for food analysis due to their inherent characteristics of low cost, ease of miniaturization, and label-free operation. To date, instrumentation is lacking for sensor arrays and for hand-held on-site applications.
... This paper presents a technique, based on Electrical Impedance Spectroscopy (EIS) (Grossi et al., 2017A), for on-line monitoring of MWFs degradation. EIS is a technique used in different fields such as: measurement of microbial concentration (Choi et al., 2009;Grossi et al., 2008;Grossi et al., 2009;Grossi et al., 2010;Grossi et al., 2011A;Grossi et al., 2012A;Grossi et al., 2013A;Grossi et al., 2013B;Grossi et al. 2014A;Grossi et al., 2017B;Hardy et al., 1977;Johnson et al., 2014 ;Mancuso et al., 2016 ;Pompei et al., 2012 ;Puttaswamy et al., 2010;Settu et al., 2015;Uria et al., 2016Wang et al., 2012 analysis of human body composition (Gudivaka et al., 1999 ;Ibrahim et al., 2005;Kyle et al., 2001;Rush et al., 2006); quality analysis in the food industry Ferrero et al., 2014;Grossi et al., 2011B ;Grossi et al., 2012B;Grossi et al., 2013C;Grossi et al., 2014B;Grossi et al., 2014C;Jackson et al., 2000;Yang et al., 2016;Valli et al., 2016) corrosion investigation of organic coatings of metal surfaces (Bonora et al., 1995;Loveday et al., 2004); measurement of oil concentration in MWFs (Grossi et al., 2017C). ...
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Metalworking fluids (MWFs) are currently used in the metal cutting industry for lubrication and to lower the temperature of both machine tools and worked pieces. Most MWFs are emulsions obtained by mixing an oil product with tap water in proper concentration (usually in the range 1% to 10%). In addition MWFs usually contain also other compounds, such as anti-microbial agents, emulsifiers and anti-corrosion products. MWFs degrade over time due to microorganism growth and contamination by processing by-products (such as tramp oil). Once worn-out the fluid must be properly disposed according to regulations using techniques such as chemical waste treatment, membrane filtration, evaporation or biological treatment. Since MWFs disposal and replacement represent a cost and have an impact on the environment, the product life-cycle must be extended as long as possible. Thus, assessment of the MWF degradation must be carried out at regular times. This work presents a technique, based on Electrical Impedance Spectroscopy, to assess MWF degradation and estimate the fluid pH value, a parameter playing an important role in the degradation process. The proposed method is based on the measurement of fluid impedance spectrum between 20 Hz and 2 MHz at four different temperatures (15, 25, 35 and 45 °C). The data are analysed by means of Principal Component Analysis (PCA) and the results show the feasibility of fluids clustering according to the contamination level with good accuracy.
... IM can be easily implemented in automatic form and provides results in a shorter time compared to the PCT. IM has been successfully tested for bacterial concentration measurements in various types of samples, such as ice cream (Grossi et al., 2008(Grossi et al., , 2010, meat (Firstenberg-Eden, 1983), vegetables (Hardy et al., 1977), raw milk (Grossi et al., 2011a), fresh water (Grossi et al., 2013), beer (Pompei et al., 2012), and human urine samples (Settu et al., 2015), and to test the efficiency of various antibiotics and chemical preservatives (Zhou and King, 1995). ...
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The detection of bacterial concentrations in metalworking fluids (MWFs), oil-in-water emulsions used in the cutting industries for cooling and lubrication, is important in order to extend the product life-cycle and plan its disposal according to regulations and legislations. The standard method of measuring culturable bacterial concentration is the plate count technique (PCT) that, however, has long response times and is not suitable for automatic implementation outside a laboratory. In this paper a portable sensor system that measures the bacterial concentration in liquid and semi-liquid media exploiting impedance microbiology is presented and tested for the application of MWF microbial monitoring. A set of MWF samples, taken from metalworking plants, have been tested and good agreement has been found between the system response and that of the PCT. The proposed system allows automated bacterial concentration measurements with shorter response times than the PCT (4 to 24 h vs. 24 to 72 h) and is suitable for in-the-field MWF monitoring.
... IM can be easily implemented in automatic form and provides results in a shorter time compared to the PCT. IM has been successfully tested for bacterial concentration measurements in various types of samples, such as ice cream (Grossi et al., 2008(Grossi et al., , 2010, meat (Firstenberg-Eden, 1983), vegetables (Hardy et al., 1977), raw milk (Grossi et al., 2011a), fresh water (Grossi et al., 2013), beer (Pompei et al., 2012), and human urine samples (Settu et al., 2015), and to test the efficiency of various antibiotics and chemical preservatives (Zhou and King, 1995). ...
... Electrical Impedance Spectroscopy (EIS) is a technique used in a wide range of applications [1]: from detection of bacterial concentration [2][3][4][5][6][7][8] to the analysis of human body composition [9][10][11][12], the characterization and quality assessment of different foods [13][14][15][16][17][18] as well as the investigation of corrosion of metals [19][20][21] and coated metal surfaces [22][23][24]. Other applications of EIS include the characterization of state-of-charge and state-of-health of batteries and fuel cells [25][26][27][28], the automated titration for different compounds [29] and the detection of cancer cells [30][31][32][33][34]. ...
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Electrical Impedance Spectroscopy (EIS), a powerful technique used for wide range of applications, is usually carried out by means of benchtop instrumentation (LCR meters and ìmpedance analyzers), not suited for in-the-field measurements performed outside a laboratory. In this paper a new portable electronic system for EIS on liquid and semi-liquid media is presented that is capable to produce an electrical fingerprint of the sample under investigation. The proposed system was used for the characterization of four different saline solutions (NaCl, Na2CO3, K2HPO4 and CuSO4). A multi-frequency approach, based on the measurement of maximum value of the impedance imaginary component and its corresponding frequency, was tested for the first time to discriminate different saline solutions. The results show that the proposed method is capable to discriminate the different solutions and to measure the concentration (R² = 0.9965) independently of the type of saline solution.
... In either case, the biosensor ought not to be inclined to fouling or proteolysis [131]. The complete biosensor ought to be cheap, small, portable, compact and fit for being utilized semi-skilled operators [132]. ...
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Prognosis of early cancer detection becomes one of the tremendous issues in the medical health system. Medical debates among specialist doctor and researcher in therapeutic approaches became a hot concern for cervix cancer deficiencies early screening, risk factors cross-reaction, portability device, rapid and free labeling system. The electrical biosensing based system showed credibility in higher specificity and selectivity due to hybridization of DNA duplex between analyte target and DNA probes. Electrical DNA sensor for cervix cancer has attracted too many attentions to researcher notification based on high performance, easy to handle, rapid system and possible to miniaturize. This review explores the current progression and future insignificant for HPV E6 genobiosensing for early Detection Strategies of Cervical Cancer.
... The sensing technique based on classic impedance microbiology [8], on the other hand, is attractive since it can detect bacterial concentration in less time than SPC (3-12 hours depending on the sample contamination) and can be easily implemented in automatic form. The authors have recently developed an embedded portable biosensor system [12], suitable for in situ measurements, that is characterized by ease of use and can be used also by non skilled operators, thus avoiding the need to ship the samples to laboratory for analysis. The impedance technique works as follows [8]: the sample under test is stored at a temperature favoring bacterial growth (generally in the range 30 °C to 42 °C) and its electrical parameters, i.e. the resistive and reactive components of the impedance Z, are measured at time intervals of 5 minutes. ...
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Sine wave signals are widely used in electronic applications such as digital oscilloscopes calibration, speech analysis and electrochemical sensors. In particular, impedance based microbial biosensors detect bacterial concentration by stimulating the sample with a sinusoidal test signal and measuring its electrical characteristics. Thus, for reliable microbial biosensing, fast and accurate sine wave analysis is mandatory. Many algorithms for the estimation of sinusoidal parameters exist that provide accurate estimate but are based on time consuming iterative procedures and/or need good starting values for the sine parameters. In this paper a linear non iterative algorithm based on the least squares method is presented that allows sinusoidal voltages analysis in a fast and efficient manner. The algorithm has been tested either with simulation analysis either with real impedances and the results proved to be accurate enough for reliable bacterial concentration measurement.
... Moreover, these measurements can be performed with electronic circuits with stable power supply not influenced by motor type and power line fluctuation. Recently, electrochemical impedance spectroscopy has been used for nondestructive monitoring in different areas of food processing and analysis, such as, for instance: determination of water and lipid content in meat (Chanet et al., 1999); determination of pH acidity and hardness in yogurt (Kitamura et al., 2000 ); detection of mastitis in raw milk samples (Norberg et al., 2004; Ferrero et al., 2002); measurement of microbial concentration in milk (Felice et al., 1999; Piton and Dasen, 1988; Piton and RongvauxGaida, 1990), yogurt (Pirovano et al., 1995) and ice cream (Grossi et al., 2008Grossi et al., , 2009Grossi et al., , 2010); detection of protein concentration in label free immunosensors (Lin et al., 2010). Electrochemical impedance spectroscopy (EIS) essentially works as follows (Barsoukov and MacDonald, 2005): the analyzed sample is stimulated with a sinusoidal test signal of fixed amplitude (usually ranging from 10 mV to few hundreds mV) and the sample impedance Z is measured in a definite range of frequencies. ...
... However, these measurement systems are not suitable for on-the-spot applications, so many efforts have been made to minimize the instruments. Grossi et al. [64] developed an embedded portable biosensor system for the determination of bacterial concentration. This system is composed of an incubation chamber, containing the sample under test, and two electronic boards: one dedicated to measuring the sample electrical characteristics, the other controlling the sample temperature, fixed at a value suitable to enhance bacterial growth. ...
Article
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The development of a rapid, sensitive, specific method for the foodborne pathogenic bacteria detection is of great importance to ensure food safety and security. In recent years impedimetric biosensors which integrate biological recognition technology and impedance have gained widespread application in the field of bacteria detection. This paper presents an overview on the progress and application of impedimetric biosensors for detection of foodborne pathogenic bacteria, particularly the new trends in the past few years, including the new specific bio-recognition elements such as bacteriophage and lectin, the use of nanomaterials and microfluidics techniques. The applications of these new materials or techniques have provided unprecedented opportunities for the development of high-performance impedance bacteria biosensors. The significant developments of impedimetric biosensors for bacteria detection in the last five years have been reviewed according to the classification of with or without specific bio-recognition element. In addition, some microfluidics systems, which were used in the construction of impedimetric biosensors to improve analytical performance, are introduced in this review.
... Recently, our research group has developed an embedded portable biosensor system [10] based on the impedance technique that is particularly suited for insitu microbial measurements of liquid and semi-liquid samples. The system has been successfully tested with different types of samples such as ice-cream [11,12], raw milk [13], beer [14] and water [15]. In this paper we present a data transformation algorithm for the measured data that allows an easy and efficient calculation of DT and can be implemented in any sensor system that performs measures of bacterial concentration based on the impedance technique. ...
Article
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Bacterial contamination is a very important issue in different fields such as food quality control and environmental monitoring. High values of bacterial concentration and/or the presence of pathogenic bacterial strains can seriously endanger human health, thus microbial concentration must be regularly screened to meet national and international regulations. Bacterial concentration is measured by Standard Plate Count technique, a reliable and accurate method that is however characterized by long time response (24–72 hours) and the need to be performed in a laboratory environment by skilled personnel. Our research group has recently developed an embedded portable biosensor system that is competitive with the standard technique in terms of response time and can be easily used for in-situ measurements by users with no microbiology knowledge. In this paper we discuss an algorithm for the transformation of the biosensor measured data that proves to be accurate and easy to be implemented. The algorithm is based on the calculation of the first and second time derivatives of the measured electrical parameters and the results show good correlation (R2= 0.829) between the bacterial concentration estimated with the biosensor and that measured by the standard technique.
Article
The present paper reports a bacteria autonomous controlled concentrator prototype with a user-friendly interface for bench-top applications. It is based on a micro-fluidic lab-on-a-chip and its associated custom instrumentation, which consists in a dielectrophoretic actuator, to pre-concentrate the sample, and an impedance analyser, to measure concentrated bacteria levels. The system is composed by a single micro-fluidic chamber with interdigitated electrodes and a instrumentation with custom electronics. The prototype is supported by a real-time platform connected to a remote computer, which automatically controls the system and displays impedance data used to monitor the status of bacteria accumulation on-chip. The system automates the whole concentrating operation. Performance has been studied for controlled volumes of Escherichia coli (E. coli) samples injected into the micro-fluidic chip at constant flow rate of 10 μL/min. A media conductivity correcting protocol has been developed, as the preliminary results showed distortion of the impedance analyser measurement produced by bacterial media conductivity variations through time. With the correcting protocol, the measured impedance values were related to the quantity of bacteria concentrated with a correlation of 0.988 and a coefficient of variation of 3.1%. Feasibility of E. coli on-chip automated concentration, using the miniaturized system, has been demonstrated. Furthermore, the impedance monitoring protocol had been adjusted and optimized, to handle changes in the electrical properties of the bacteria media over time. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
Conference Paper
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Bacterial detection is of primary importance in many fields, such as food and environmental monitoring. Measurements of bacterial concentration are traditionally carried out by means of the Standard Plate Count technique, a reliable method for microbial screening that, however, features long response time and is carried out by qualified personnel in microbiology laboratories. The impedance technique for bacterial concentration detection represents a method very competitive with Standard Plate Count in terms of response time (3-12 hours vs. 24-72 hours) as well as for the possibility to be realized in automatic form. This paper presents an embedded portable biosensor system for the measurement of bacterial concentration in cow’s raw milk. The possibility to perform measurements “on the field”, hence without the need to ship samples to distant laboratories, and to transmit the data on wireless communication systems or on the Internet represents a substantial advantage in terms of time and cost, thus making the presented system an important tool for in-situ bacterial screening.
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Chapter
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Detection of bacterial colonies in water is a pressing issue in recent times owing to its implications on human health, leading to an urgent need for low cost, disposable sensors. In this work, we report a disposable impedimetric sensor for detection of total bacterial colonies present in water samples. The sensor consists of a polyaniline coated filter paper functionalized with a homo-bi functional crosslinker, glutaraldehyde. Prior to the functionalization step, two Ag electrodes are deposited on the filter paper using conductive silver paste. The aldehyde groups of glutaraldehyde bind with the amine functional groups present on bacterial cell wall resulting in a change in dielectric constant, and consequently, the capacitive effect between the two Ag electrodes. Also, bacterial metabolism affects the medium conductivity and in turn, the medium resistance changes. The combined effect of changes in capacitive effect as well as resistance is reflected as a change in AC impedance measured using a frequency response analyzer (FRA). E. coli and Pseudomonas aeruginosa bacteria are detected in PBS buffer up to ~ 500 cfu/mL. Testing is also carried out by spiking tap water and grey water with known concentrations of bacteria samples. The detection limits obtained are 500 – 1000 cfu/mL with a response time of ~ 20 minutes. The developed sensor provides rapid, moderately sensitive, cost-effective solution for detecting total bacterial load in water samples.
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Rapid, specific, and sensitive detection of pathogenic bacteria is very important within areas like food safety, medical diagnostics, hospital infection and biological warfare. Optical evanescent wave sensors are evolving to meet these challenges. Evanescent wave biosensors generate an electromagnetic wave at the sensor surface that penetrates 100-200 nm into the surrounding medium, which have proven to be a highly sensitive tool to monitor interactions in the close vicinity of the sensor surface. However, the use of such waveguides for bacterial detection is problematic for several reasons. These include the short penetration depth of the evanescent field of these waveguides (100-250 nm) compared to a typical size of a bacterium (1-5 mum), which places the majority of the bound cell outside the evanescent field. In addition, the low refractive index contrast between the bacterium cytoplasm and aqueous environments in which detection is usually performed, and availability and accessibility of antigens on the bacterium surface binding to the biorecognition elements. Finally, the sensor performance can for example be limited due to (i) mass transport of large analytes like bacteria which limits the binding to the immobilized recognition receptors, (ii) non-specific binding, and (iii) long analysis time. This article will focus on the development of deep-probe optical evanescent wave sensor such as metal clad leaky waveguide sensor for bacterial detection. In addition, two complete detection systems integrated with physical force fields to overcome these problems will be presented. These sensor systems are based on MCLW sensors and integrated with respectively an electric field and ultrasound standing waves as physical force to concentrate and enhance capturing of bacteria spores into immobilized antibodies on the sensor surface. The integration improves the detection limit by a few orders of magnitude and shortens the analysis time significantly.
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An amperometric culture-based method was developed for rapid detection of viable Escherichiacoli in water. The bacteria were recovered by filtration and incubated in a selective medium, lauryl sulphate broth (LSB) supplemented with the substrate 4-aminophenyl-β-d-galactopyranoside (4-APGal) at 44.5°C. The electrochemically active molecule 4-aminophenol (4-AP) was produced after hydrolysis of 4-APGal by the enzyme β-galactosidase. 4-AP was measured by amperometry and was detected at a due concentration of E.coli. The time necessary for reaching that concentration was inversely related to the initial E.coli concentration of the sample. Environmental samples and suspensions of Ecoli IT1 were assayed. 4-AP was detected after 7.3 and 2.0h in samples containing initial concentrations of E.coli IT1 of 4.5 and 4.5×106cfuml−1, respectively. For environmental samples with initial E.coli concentrations of 1.0 and 2.0×103cfuml−1, 4-AP were detected after 10 and 6.6h, respectively.
Article
The bacteriological load of bulk tank raw milk samples was determined using the Bactoscan (BSN) 8000S and three cultural methods: standard plate count (SPC), spiral plate count (SPC) and plate loop count (PLC). A total of 3640 milk samples (2918 natural and 722 spiked) were analyzed. The repeatability of each system was assessed at critical cut-off counts of log10 4.0 and Iog10 5.0. In descending order, kappa values of within-system-agreement (repeatability) at Iog10 4.0 were: SPC = 0.87, SPC = 0.70, BSN = 0.67 and PLC = 0.42. Descending kappa values at log10 5.0 were: BSN = 0.96, SPC = 0.95, PLC = 0.84 and SPC = 0.78. BSN results demonstrated good correlation with the three methods: SPC (r = 0.79), PLC (r = 0.72) and SPC (r = 0.73). These results suggest that the rapid and automated Bactoscan 8000S could provide a reasonable alternative to the three cultural methods for enumeration of bacteria in bulk tank raw milk when counts fall within the instruments specified applicable range of log10 4.0-log10 5.477.
Article
This paper describes a selective detection technique of viable bacteria based on dielectrophoresis and electrical impedance measurements. The authors have previously proposed a detection technique of biological particles called dielectrophoretic impedance measurement (DEPIM) method using positive dielectrophoretic force to capture biological cells in suspension onto an interdigitated microelectrode array. By combining antigen-antibody reaction with the DEPIM, selective detection of a particular species of bacteria was demonstrated. In this present work, the authors demonstrated another selective DEPIM method utilizing cell viability dependency of dielectrophoretic force without introducing the antigen-antibody reaction. It was found that dielectrophoresis of heat-treated Escherichia coli showed strong dependency on viability when applied field frequency was as high as 1 MHz. As a result, viable bacteria could be exclusively collected by positive dielectrophoresis and selectively detected by the DEPIM technique from a suspension also containing heat-treated nonviable cells. On the other hand, nonviable bacteria obtained by UV irradiation showed little dielectrophoresis dependency on viability. According to a theoretical analysis of the dielectrophoretic force, it is suggested that heat treatment alters the dielectric properties of treated cells. In particular, a decrease in cytoplasmic conductivity, which might be caused by heat-induced perforation of cell membrane, was expected to considerably affect dielectrophoresis characteristics. Proposed selective DEPIM method was also applied to evaluation of heat sterilization effect on a real time basis. It was experimentally proved that DEPIM could evaluate viable cell number variation with heat treatment time in a considerably shorter time than conventional microbiological method based on cell incubation.
Article
Bacterial activity and growth were monitored by following the changes of electrical impedance of cultures in liquid media. The signal is expressed automatically as a curve similar to grwoth curves produced by other methods. The technique offers a new, rapid and sensitive means of detecting active micro-organisms and is potentially the basis of rapid automated systems in this field. The impedance changes indicate that the micro-organisms metabolise substrates of low conductivity into products of high conductivity and that the changes are due to the activity of the micro-organisms rather than increase in their numbers. The activity of strains of Escherichia coli, Klebsiella aerogenes, Pseudo-monas aeruginosa, Staphyloccus aureus, and Streptococcus faecalis was detected within 2 h with inocula of 10-3 minus 10-5 organisms per ml. Different reactions of bacteria in various media suggest that the method may be applied to the rapid identification of micro-organisms. The inhibitory effect of antibiotics on bacteria was demonstrated within 2 h, indicating that the method may be useful for the rapid determination of bacterial sensitivity to antibiotics and the rapid assay of antibiotics in serum. Correlation of response time to initial inoculum allows estimatin of numbers of viable organisms. The sensitivity of the method allowed detection of activity due to Myoplasma argininii within 3 h; this suggests that the method might be applicable to the rapid detection of other slowly growing organisms, such as mycobacteria.
Article
A conceptually simple and east-to-use technique is described that uses continuous impedance measurements for automated monitoring of microbial growth and metabolism. The method has been applied to a wide range of microorganisms. Optical clarity is not required. The sensitivity and reproducibility of the method are demonstrated. The mechanism whereby microbial growth alters the impedance of the medium is discussed, as well as potential applications of the method to clinical microbiology.
Article
A piezoelectric crystal immunosensor has been developed for the detection of enterobacteria in drinking water using antibodies against the enterobacterial common antigen. Applying an anti-enterobacterial antibody layer via protein A immobilization onto a 10-MHz crystal, a response is observed for 10(6) to 10(9) cells ml-1 of Escherichia coli K12, and for various other antigens of the Enterobacteriaceae family.
Article
Use of firefly luciferase to assay adenosine triphosphate (ATP) extracted from microorganisms provides an easy means to enumerate microbes within minutes. The small amount of light produced is proportional to ATP and thus microbial number. The average bacterium contains around 10−15 g ATP per cell. Present reagents permit detection of 103 cells per tube. Luminometers currently on the market detect about 10−12 g ATP. Proper extraction of ATP from the microbes is an essential part of any protocol, as is the removal of non-microbial ATP from, for example, somatic cells also present in samples. The technique may be applied to a wide range of samples, for example food and beverages and clinical samples such as urine. The ATP assay gives a global measure of microbial numbers, i.e. it is not species specific unless a species separation step is included in the protocol.
Article
Progress in the development of rapid methods and the automation of microbiological techniques would benefit from exploitation of parameters which are affected by minimal concentrations of micro organisms. One such parameter is the effect of metabolic activity of micro organisms on the electrical conductivity of a nutrient medium. Complex nutrients, such as carbohydrates, are metabolized into products such as lactates and carbonates and this replacement of relatively large, electrically inert molecules by a large number of electrically active molecules and ions increases the electrical conductivity of the medium. Thus, by monitoring changes in electrical impedance the activity of a growing bacterial culture can be detected. A method using this principle would have the advantages of the high sensitivity offered by impedance measurements and simplicity of apparatus.
Article
This paper is presented as an overview of the pathogen detection industry. The review includes pathogen detection markets and their prospects for the future. Potential markets include the medical, military, food, and environmental industries. Those industries combined have a market size of $563 million for pathogen detecting biosensors and are expected to grow at a compounded annual growth rate of 4.5%. The food market is further segmented into different food product industries. The overall food-pathogen testing market is expected to grow to $192 million and 34 million tests by 2005. The trend in pathogen testing emphasizes the need to commercialize biosensors for the food safety industry as legislation creates new standards for microbial monitoring. With quicker detection time and reusable features, biosensors will be important to those interested in real time diagnostics of disease causing pathogens. As the world becomes more concerned with safe food and water supply, the demand for rapid detecting biosensors will only increase.
Article
Silver, platinum, gold, stainless-steel, and copper electrodes were used with low currents (0.02 to 20 μA/mm2) to explore their electrochemical effects on the growth of four bacterial species. In the higher current ranges, all electrodes inhibited growth at both poles, usually in conjunction with electrolytic break-down of the medium and severe corrosion of the metal. Silver, however, was extremely bacteriostatic, even at the lowest current, when used as the anode. Quantitative studies showed that most of this inhibition takes place in a few hours and is not accompanied by changes in pH. Electrochemically injected silver from the anode is probably the instrumental agent, being effective in concentrations of about 5 μg/ml. This is the equivalent concentration of silver sulfadiazine that has been shown to give complete inhibition of bacteria, but without the sulfonamide moiety.
Article
The detection of microbial concentration, essential for safe and high quality food products, is traditionally made with the plate count technique, that is reliable, but also slow and not easily realized in the automatic form, as required for direct use in industrial machines. To this purpose, the method based on impedance measurements represents an attractive alternative since it can produce results in about 10h, instead of the 24-48h needed by standard plate counts and can be easily realized in automatic form. In this paper such a method has been experimentally studied in the case of ice-cream products. In particular, all main ice-cream compositions of real interest have been considered and no nutrient media has been used to dilute the samples. A measurement set-up has been realized using benchtop instruments for impedance measurements on samples whose bacteria concentration was independently measured by means of standard plate counts. The obtained results clearly indicate that impedance measurement represents a feasible and reliable technique to detect total microbial concentration in ice-cream, suitable to be implemented as an embedded system for industrial machines.
  • J Suehiro
  • R Hamada
  • D Noutomi
  • M Shutou
  • M Hara
Suehiro, J., Hamada, R., Noutomi, D., Shutou, M., Hara, M., 2003. J. Electrostat. 57, 157–168.
  • P E Stanley
Stanley, P.E., 2005. J. Biolumin. Chemilumin. 4, 375–380.
  • P S Mead
  • L Slutsker
  • V Dietz
  • L F Mccaig
  • J S Bresce
  • C Shapiro
  • P M Griffin
  • R V Tauxe
Mead, P.S., Slutsker, L., Dietz, V., McCaig, L.F., Bresce, J.S., Shapiro, C., Griffin, P.M., Tauxe, R.V., 2000. J. Environ. Health, 62.
  • M Plomer
  • G G Guilbault
  • B Hock
Plomer, M., Guilbault, G.G., Hock, B., 1992. Enzyme Microb. Technol. 14, 230– 235.
  • S Sengupta
  • D A Battigelli
  • H C Chang
Sengupta, S., Battigelli, D.A., Chang, H.C., 2006. Lab Chip 6, 1–11.
  • F Perez
  • I Tryland
  • M Mascini
  • L Fiksdal
Perez, F., Tryland, I., Mascini, M., Fiksdal, L., 2001. Anal. Chim. Acta 427, 149–154.
  • C J Felice
  • R E Madrid
  • M E Valentinuzzi
  • R Firstemberg-Eden
  • G Eden
Felice, C.J., Madrid, R.E., Valentinuzzi, M.E., 2005. Biomed. Eng. Online 4, 22. Firstemberg-Eden, R., Eden, G., 1984. Impedance Microbiology, 3. Wiley, New York, pp. 154–196.
  • M Grossi
  • A Pompei
  • M Lanzoni
  • R Lazzarini
  • D Matteuzzi
  • B Riccò
Grossi, M., Pompei, A., Lanzoni, M., Lazzarini, R., Matteuzzi, D., Riccò, B., 2009. IEEE Sens. J. 9 (10), 1270–1276.
  • E C Alocilja
  • S M Radke
Alocilja, E.C., Radke, S.M., 2003. Biosens. Bioelectron. 18, 841–846.
  • A Ur
  • D F J Brown
Ur, A., Brown, D.F.J., 1973. ICRS J. Int. Res. Commun. 1, 37.
  • J A Spadaro
  • T J Berger
  • S D Barranco
  • S E Chapin
  • R O Becker
Spadaro, J.A., Berger, T.J., Barranco, S.D., Chapin, S.E., Becker, R.O., 1974. Antimicrob. Agents Chemother. 6 (5), 637–642.
  • M Zourob
  • S Mohr
  • N J Goddard
Zourob, M., Mohr, S., Goddard, N.J., 2007. ISSSE, 49–52.