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Ryder J, Smith RF, Neary JM. Postpartum longissimus dorsi muscle loss, but not back fat, is associated with resumption of postpartum ovarian activity in dairy cattle. J Dairy Sci 2023; 106:8087-8097. [PMID: 37562647 DOI: 10.3168/jds.2023-23253] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2023] [Accepted: 05/01/2023] [Indexed: 08/12/2023]
Abstract
The objectives of this observational cohort study were to assess the effect of body condition score change, back fat depth change, and muscle diameter change on the time to commencement of luteal activity and first estrus in commercial pedigree Holstein cows. A total of 140 of 200 commercial pedigree Holstein cows were enrolled in one dairy herd in Somerset, UK, over 52 wk in 2021 to 2022. The herd used 4 automatic milking machines with in-line progesterone measurement capability to determine commencement of luteal activity and time to first estrus. Cows were followed until at least 60 d postpartum, and milk progesterone was measured daily starting from 10 DIM. Body condition scoring and ultrasound measurements of back fat depth and longissimus dorsi muscle diameter were performed on cows twice, within 7 d of both calving and 60 DIM. Other explanatory variables assessed included parity, 60-d and 305-d milk yield, and subclinical ketosis (β-hydroxybutryate ≥1.2 mmol/L). Occurrence of clinical disease <60 DIM was forced into all models as a binary variable. Data were analyzed using multivariable Cox proportionate survival analyses. Muscle loss was associated with commencement of luteal activity and time to first estrus. A reduction in muscle diameter by 1.5 to 5 mm was associated with the shortest time to the start of luteal activity and first estrus. A reduction in muscle diameter >8 mm was associated with the longest times to luteal activity and first estrus. In addition to being affected by muscle loss, commencement of luteal activity was delayed by subclinical ketosis, clinical disease, and failure to gain body condition to 60 DIM. Cows that had a BCS loss of 0.25 or more between calving and 60 DIM were at least 52 ± 22% less likely to have commenced luteal activity compared with those that gained BCS. Interestingly, cows that had no change in body condition score commenced luteal activity later than those that gained body condition score. Muscle loss was associated with time to first estrus irrespective of clinical disease status. Cows that lost >8 mm of muscle diameter showed estrus behavior later than cows that lost 1.5 to 5 mm. In conclusion, our findings indicate that extensive muscle loss postpartum was associated with a delayed start to luteal activity and first estrus, irrespective of body condition change, clinical disease, and subclinical ketosis. Marginal muscle loss and a gain in body condition, however, were associated with an earlier start to luteal activity and first estrus.
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Affiliation(s)
- J Ryder
- Garston Veterinary Group, Garston House, Portway, Frome, BA11 1PZ, UK
| | - R F Smith
- Department of Livestock and One Health, Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, Neston, CH64 7TE, UK
| | - J M Neary
- Department of Livestock and One Health, Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, Neston, CH64 7TE, UK.
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2
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Chen C, La M, Yi X, Huang M, Xia N, Zhou Y. Progress in Electrochemical Immunosensors with Alkaline Phosphatase as the Signal Label. BIOSENSORS 2023; 13:855. [PMID: 37754089 PMCID: PMC10526794 DOI: 10.3390/bios13090855] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2023] [Revised: 08/18/2023] [Accepted: 08/22/2023] [Indexed: 09/28/2023]
Abstract
Electrochemical immunosensors have shown great potential in clinical diagnosis, food safety, environmental protection, and other fields. The feasible and innovative combination of enzyme catalysis and other signal-amplified elements has yielded exciting progress in the development of electrochemical immunosensors. Alkaline phosphatase (ALP) is one of the most popularly used enzyme reporters in bioassays. It has been widely utilized to design electrochemical immunosensors owing to its significant advantages (e.g., high catalytic activity, high turnover number, and excellent substrate specificity). In this work, we summarized the achievements of electrochemical immunosensors with ALP as the signal reporter. We mainly focused on detection principles and signal amplification strategies and briefly discussed the challenges regarding how to further improve the performance of ALP-based immunoassays.
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Affiliation(s)
- Changdong Chen
- College of Chemical and Environmental Engineering, Pingdingshan University, Pingdingshan 476000, China
| | - Ming La
- College of Chemical and Environmental Engineering, Pingdingshan University, Pingdingshan 476000, China
| | - Xinyao Yi
- College of Chemistry and Chemical Engineering, Central South University, Changsha 410083, China
| | - Mengjie Huang
- College of Chemistry and Chemical Engineering, Anyang Normal University, Anyang 455000, China
| | - Ning Xia
- College of Chemistry and Chemical Engineering, Anyang Normal University, Anyang 455000, China
| | - Yanbiao Zhou
- College of Chemical and Environmental Engineering, Pingdingshan University, Pingdingshan 476000, China
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Evaluating automated infrared thermography and vulva exposure tracking as components of an estrus detection platform in a commercial dairy herd. Animal 2022; 16:100585. [PMID: 35901655 DOI: 10.1016/j.animal.2022.100585] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2021] [Revised: 06/08/2022] [Accepted: 06/09/2022] [Indexed: 11/22/2022] Open
Abstract
The primary objective of this study was to develop an automated infrared thermography platform (Estrus BenchMark) capable of measuring skin temperature and tail movements as a means of identifying cows in estrus. The secondary objective was to evaluate the accuracy of Estrus BenchMark to detect estrus compared to in-line milk progesterone (P4) analysis (Herd Navigator System) in a commercial dairy herd managed under a robotic milking system. Data were collected on forty-six cows from 45 to 120 d after calving. Cows were flagged in estrus when milk P4 fell below 5 ng/mL. The Estrus BenchMark true positive estrus alerts (Sensitivity; Se%) were compared to Herd Navigator System estrus alerts at different time-windows (±12 h, ±24 h, ±48 h, and ±72 h) relative to the Estrus BenchMark estrus alerts for all the estrus alerts (AE) and confidence-quality estrus (CQE; >80% quality) alerts identified by Herd Navigator System. The Estrus BenchMark captured skin temperature and tail movements resulting in vulva exposure (left tail movements, LTail; right tail movements, RTail; and pooled tail movements, PTail) for each milking event. Skin temperature tended to increase when the milk P4 concentration (Least-Squares Means ± SE) dropped for AE (estrus day [d 0]; P4; 3.51 ± 0.05 ng/mL, Skin temperature; 33.31 ± 2.38 °C) compared with d -7 (P4; 20.22 ± 0.73 ng/mL; Skin temperature: 32.05 ± 3.77 °C). The increase in skin temperature, however, was significant in cows with CQE > 80% at d 0 (32.75 ± 0.29 °C) compared to d -7 (31.80 ± 0.28 °C). The prevalence of tail movements to expose vulva was greater (P = 0.01) in AE at d 0 (LTail: 62.50%; PTail; 68.75%; and RTail: 56.25%) compared with d -7 (LTail: 18.75%; PTail: 9.37%: and RTail: 9.37%), and d +4 (LTail: 9.37%; PTail: 9.37%; and RTail: 12.5%). Moreover, the higher prevalence of tail movements at d 0 was observed in cows with CQE > 80% (LTail; 65%, PTail; 80%, and RTail; 70%) compared to those with CQE < 80%. The highest Estrus BenchMark Youden index (YJ; 0.45), diagnostic odds ratio (DOR; 9.04), and Efficiency (0.77) were achieved for AE in a ±48 h window and at ±72 h window for CQE (YJ; 0.66, DOR; 25.29, and Efficiency 0.76) relative to Herd Navigator System estrus alerts. The highest Estrus BenchMark resulted in 58% estrus detection rates for AE and 80% for cows with CQE compared to the Herd Navigator System.
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An electrocatalytic active AuNPs/5-Amino-2-mercaptobenzimidazole/rGO/SPCE composite electrode for ultrasensitive detection of progesterone. J Electroanal Chem (Lausanne) 2021. [DOI: 10.1016/j.jelechem.2021.115023] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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5
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Samie HA, Arvand M. Label-free electrochemical aptasensor for progesterone detection in biological fluids. Bioelectrochemistry 2020; 133:107489. [PMID: 32097878 DOI: 10.1016/j.bioelechem.2020.107489] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2019] [Revised: 02/16/2020] [Accepted: 02/16/2020] [Indexed: 02/06/2023]
Abstract
A label-free electrochemical progesterone (P4) aptasensor was successfully developed by covalently immobilizing NH2-functionalized P4-specific aptamer on the electrode surface. The NiO-Au hybrid nanofibers were synthesized by the electrospinning technique. GQDs-NiO-AuNFs nanocomposite was prepared by dispersing of electrospun NiO-AuNFs in the as-synthesized graphene quantum dots (GQDs) solution and stirring for 24 h. Novel GQDs-NiO-AuNFs nano-architecture in combination with functionalized multiwalled carbon nanotubes (f-MWCNTs) were further utilized to modify screen printed carbon electrode (SPCE) in order to construct an effective immobilization matrix with plenty of carboxylic functional groups. The stepwise assembly process of the designed aptasensor was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The aptamer-progesterone complex formation led to a hindered electron transfer reaction on the sensing interface, which decreased the redox probe peak current. Based on of this, progesterone could be quantitatively detected by monitoring the decrease of differential pulse voltammetric (DPV) responses of [Fe(CN)6]3-/4- peak current with increasing the progesterone concentration. Under optimized experimental parameters, the aptasensor exhibited a dynamic concentration range from 0.01 to 1000 nM and a detection limit of 1.86 pM. The proposed aptasensor was successfully employed for the determination of progesterone in human serum samples and pharmaceutical formulations.
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Affiliation(s)
- Hedieh Asadi Samie
- Electroanalytical Chemistry Laboratory, Faculty of Chemistry, University of Guilan, Namjoo Street, P.O. Box: 1914, Rasht, Iran
| | - Majid Arvand
- Electroanalytical Chemistry Laboratory, Faculty of Chemistry, University of Guilan, Namjoo Street, P.O. Box: 1914, Rasht, Iran.
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Mintah Churcher NK, Upasham S, Rice P, Bhadsavle S, Prasad S. Development of a flexible, sweat-based neuropeptide Y detection platform. RSC Adv 2020; 10:23173-23186. [PMID: 35520310 PMCID: PMC9054693 DOI: 10.1039/d0ra03729j] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2020] [Accepted: 06/05/2020] [Indexed: 12/14/2022] Open
Abstract
Neuropeptide Y (NPY) biomarker levels have a close association with the diagnosis of Major Depression Disorder (MDD) and anxiety disorders. Quantifying NPY in correlation to self-reported symptoms will be an important measure to ensure a relatively uniform diagnosis and help with disease prognosis of these disorders. The work presented is a novel, passive eccrine sweat based, electrochemical detection platform for quantification of NPY biomarker levels. The paper offers a comparison between non-porous and porous sensor platforms using various electrochemical detection techniques. This work uses a novel strategy towards designing an optimal nanobioelectronic interface to measure NPY. The portability aspect of this detection platform is discussed by the demonstration a novel, portable EmStat Pico based electronic platform. The detection limit of the sensor is 10 pg mL−1 and its range is 20–500 pg mL−1. The NPY detection platform is envisioned to be a wearable point-of need monitoring system for management of chronic anxiety disorders and MDD. Novel wearable NPY biomarker tracking system, envisioned to be a chronic anxiety and MDD management platform via self-monitoring.![]()
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Affiliation(s)
| | - Sayali Upasham
- Department of Bioengineering
- University of Texas at Dallas
- Richardson
- USA
| | - Paul Rice
- Department of Bioengineering
- University of Texas at Dallas
- Richardson
- USA
| | - Serena Bhadsavle
- Department of Bioengineering
- University of Texas at Dallas
- Richardson
- USA
| | - Shalini Prasad
- Department of Bioengineering
- University of Texas at Dallas
- Richardson
- USA
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7
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Wang Y, Partridge A, Wu Y. Improving nanoparticle-enhanced surface plasmon resonance detection of small molecules by reducing steric hindrance via molecular linkers. Talanta 2019; 198:350-357. [DOI: 10.1016/j.talanta.2019.02.035] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2018] [Revised: 02/03/2019] [Accepted: 02/05/2019] [Indexed: 10/27/2022]
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8
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Bruinjé TC, Gobikrushanth M, Colazo MG, Ambrose DJ. Dynamics of pre- and post-insemination progesterone profiles and insemination outcomes determined by an in-line milk analysis system in primiparous and multiparous Canadian Holstein cows. Theriogenology 2017; 102:147-153. [DOI: 10.1016/j.theriogenology.2017.05.024] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Accepted: 05/25/2017] [Indexed: 10/19/2022]
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9
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Bruinjé TC, Colazo MG, Gobikrushanth M, Ambrose DJ. Relationships among early postpartum luteal activity, parity, and insemination outcomes based on in-line milk progesterone profiles in Canadian Holstein cows. Theriogenology 2017; 100:32-41. [DOI: 10.1016/j.theriogenology.2017.05.021] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2017] [Revised: 05/14/2017] [Accepted: 05/24/2017] [Indexed: 10/19/2022]
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10
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Animal board invited review: precision livestock farming for dairy cows with a focus on oestrus detection. Animal 2015; 10:1575-84. [PMID: 26608699 DOI: 10.1017/s1751731115002517] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Dairy cows are high value farm animals requiring careful management to achieve the best results. Since the advent of robotic and high throughput milking, the traditional few minutes available for individual human attention daily has disappeared and new automated technologies have been applied to improve monitoring of dairy cow production, nutrition, fertility, health and welfare. Cows milked by robots must meet legal requirements to detect healthy milk. This review focuses on emerging technical approaches in those areas of high cost to the farmer (fertility, metabolic disorders, mastitis, lameness and calving). The availability of low cost tri-axial accelerometers and wireless telemetry has allowed accurate models of behaviour to be developed and sometimes combined with rumination activity detected by acoustic sensors to detect oestrus; other measures (milk and skin temperature, electronic noses, milk yield) have been abandoned. In-line biosensors have been developed to detect markers for ovulation, pregnancy, lactose, mastitis and metabolic changes. Wireless telemetry has been applied to develop boluses for monitoring the rumen pH and temperature to detect metabolic disorders. Udder health requires a multisensing approach due to the varying inflammatory responses collectively described as mastitis. Lameness can be detected by walk over weigh cells, but also by various types of video image analysis and speed measurement. Prediction and detection of calving time is an area of active research mostly focused on behavioural change.
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11
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Mistry KK, Layek K, Mahapatra A, RoyChaudhuri C, Saha H. A review on amperometric-type immunosensors based on screen-printed electrodes. Analyst 2015; 139:2289-311. [PMID: 24678518 DOI: 10.1039/c3an02050a] [Citation(s) in RCA: 66] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In this brief review, we summarize the recent research activities involved in the development of amperometric-type immunosensors based on screen-printed electrodes (SPEs). We focus on the underlying principle involved in these types of sensors, their fabrication and electrode surface modification. We also discuss the various factors involved in the designing of such immunosensors and how they affect their performances. Finally we provide an insight into the drawbacks associated with these SPEs.
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Affiliation(s)
- Kalyan Kumar Mistry
- CSIR-Central Mechanical Engineering Research Institute, M. G. Avenue, Durgapur-713209, India.
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12
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Xia N, Ma F, Zhao F, He Q, Du J, Li S, Chen J, Liu L. Comparing the performances of electrochemical sensors using p-aminophenol redox cycling by different reductants on gold electrodes modified with self-assembled monolayers. Electrochim Acta 2013. [DOI: 10.1016/j.electacta.2013.07.118] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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13
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Zhang HY, Du XY, Liu Q, Xia C, Sun LW. Detection of progesterone in bovine milk using an electrochemical immunosensor. INT J DAIRY TECHNOL 2013. [DOI: 10.1111/1471-0307.12076] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Hong You Zhang
- College of Animal Science and Veterinary Medicine; Heilongjiang Bayi Agricultural University; Daqing; 163319; China
| | - Xia Yan Du
- School of Public Health; Harbin Medical University; Harbin; 150081; China
| | - Qian Liu
- College of Animal Science and Veterinary Medicine; Heilongjiang Bayi Agricultural University; Daqing; 163319; China
| | - Cheng Xia
- College of Animal Science and Veterinary Medicine; Heilongjiang Bayi Agricultural University; Daqing; 163319; China
| | - Ling Wei Sun
- College of Animal Science and Veterinary Medicine; Heilongjiang Bayi Agricultural University; Daqing; 163319; China
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14
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Tien CY, Jou AFJ, Fan NC, Chuang MC, Ho JAA. Preparation of Liposomal Progesterone and Its Application on the Measurement of Progesterone Interpreted via Electrochemical and Colorimetric Sensing Platforms. ELECTROANAL 2013. [DOI: 10.1002/elan.201200563] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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15
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Arévalo FJ, Molina PG, Zón MA, Fernández H. Studies about the adsorption of progesterone (P4) at glassy carbon electrodes in aqueous buffer solution by square wave voltammetry. J Electroanal Chem (Lausanne) 2009. [DOI: 10.1016/j.jelechem.2009.02.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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16
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Electrochemical sensors and biosensors based on heterogeneous carbon materials. MONATSHEFTE FUR CHEMIE 2009. [DOI: 10.1007/s00706-009-0131-9] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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17
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Escamilla-Gómez V, Campuzano S, Pedrero M, Pingarrón JM. Immunosensor for the determination of Staphylococcus aureus using a tyrosinase–mercaptopropionic acid modified electrode as an amperometric transducer. Anal Bioanal Chem 2008; 391:837-45. [DOI: 10.1007/s00216-007-1810-1] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2007] [Revised: 11/27/2007] [Accepted: 12/12/2007] [Indexed: 11/24/2022]
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18
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Renedo OD, Alonso-Lomillo M, Martínez MA. Recent developments in the field of screen-printed electrodes and their related applications. Talanta 2007; 73:202-19. [DOI: 10.1016/j.talanta.2007.03.050] [Citation(s) in RCA: 442] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2007] [Revised: 03/14/2007] [Accepted: 03/23/2007] [Indexed: 11/29/2022]
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Kreuzer MP, McCarthy R, Pravda M, Guilbault GG. Development of Electrochemical Immunosensor for Progesterone Analysis in Milk. ANAL LETT 2007. [DOI: 10.1081/al-120030289] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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20
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Hart JP, Crew A, Crouch E, Honeychurch KC, Pemberton RM. Some Recent Designs and Developments of Screen‐Printed Carbon Electrochemical Sensors/Biosensors for Biomedical, Environmental, and Industrial Analyses. ANAL LETT 2007. [DOI: 10.1081/al-120030682] [Citation(s) in RCA: 182] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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21
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Zhang Y, Heller A. Reduction of the nonspecific binding of a target antibody and of its enzyme-labeled detection probe enabling electrochemical immunoassay of an antibody through the 7 pg/ml-100 ng/mL (40 fM-400 pM) range. Anal Chem 2007; 77:7758-62. [PMID: 16316186 DOI: 10.1021/ac051218c] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We describe a simple, potentially low-cost, amperometric, enzyme-amplified, sandwich-type immunoassay, monitoring IgG at a concentration as low as approximately 7 pg/mL with a dynamic range of 10(4). The assay utilizes a screen-printed carbon electrode on which a redox hydrogel and avidin are co-electrodeposited. To neutralize nonspecifically binding positively charged microdomains of the avidin, two polyanions, poly(acrylic acid-co-maleic acid) and poly(acrylic acid), are applied. These polyanions bind to the film not only electrostatically but also by Michael addition reaction to cysteine, lysine, or arginine functions of the avidin. The electrode is then made specific for the analyte, for which rabbit IgG was chosen, by conjugating the film-bound avidin to biotin-labeled anti-rabbit IgG. After exposure to the tested solution and capture of rabbit IgG, the sandwich is completed by conjugation of horseradish-peroxidase (HRP)-labeled anti-rabbit IgG. Electrical contact between the HRP and the electrode-bound hydrogel results in the formation of an electrocatalyst for the electroreduction of H2O2 to water. The application of the poly(acrylic acid-co-maleic acid) and the poly(acrylic acid) reduces the nonspecific adsorption-associated noise, lowers the detection limit from 3 ng/mL (approximately 20 pM analyte antibody concentration) to approximately 7 pg/mL (approximately 40 fM analyte antibody concentration), and also expands the dynamic range to 10(4).
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Affiliation(s)
- Yongchao Zhang
- Department of Chemical Engineering, The University of Texas at Austin, 78712, USA
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Carralero V, González-Cortés A, Yáñez-Sedeño P, Pingarrón J. Development of a Progesterone Immunosensor Based on a Colloidal Gold-Graphite-Teflon Composite Electrode. ELECTROANAL 2007. [DOI: 10.1002/elan.200603794] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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23
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Pravda M, O'Halloran MP, Kreuzer MP, Guilbault GG. COMPOSITE GLUCOSE BIOSENSOR BASED ON SCREEN-PRINTED ELECTRODES BULK MODIFIED WITH PRUSSIAN BLUE AND GLUCOSE OXIDASE. ANAL LETT 2007. [DOI: 10.1081/al-120004548] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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24
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Hart JP, Crew A, Crouch E, Honeychurch KC, Pemberton RM. Chapter 23 Screen-printed electrochemical (bio)sensors in biomedical, environmental and industrial applications. ELECTROCHEMICAL SENSOR ANALYSIS 2007. [DOI: 10.1016/s0166-526x(06)49023-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
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25
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Chikae M, Kerman K, Nagatani N, Takamura Y, Tamiya E. An electrochemical on-field sensor system for the detection of compost maturity. Anal Chim Acta 2007; 581:364-9. [PMID: 17386464 DOI: 10.1016/j.aca.2006.08.030] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2006] [Revised: 08/05/2006] [Accepted: 08/10/2006] [Indexed: 11/24/2022]
Abstract
A maturity sensor system was developed, based on the combination of three electrically measured parameters, pH, NH(4)(+) concentration, and phosphatase activity in the water extracts of compost samples. One of these parameters, the apparent phosphatase activity in crude test solutions was determined using screen-printed carbon strips (SPCSs) coated with alpha-naphthyl phosphate (alpha-NP) in Nafion film. The phosphatase activity was monitored in connection with differential pulse voltammetry (DPV) with an aliquot (30 microL) of the test solution on SPCS. The phosphatase activity sensor was validated using alkaline phosphatase (ALP) in Tris-HCl buffer (pH 8.0) and acid phosphatase (ACP) in citric acid buffer (pH 5.0). The activity of the spiked enzymes in the water extract of the compost sample could be confirmed with the change of corresponding oxidation peak current signal of the product, alpha-naphthol. The water extracts of compost samples (n=24) collected in various composting days were applied to our compost maturity sensor system, and the conventional germination tests. Using multiple regression analysis, the germination index (GI) was expressed by the multi-linear regression equation consisting of pH, NH(4)(+) concentration, and the phosphatase activity. The calculated GI from the regression equation had a good correlation with the measured GI of the corresponding composts (r=0.873). As a result, we have determined an equation for the determination of the compost stability using our portable sensor system rapidly at the composting site.
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Affiliation(s)
- Miyuki Chikae
- School of Materials Science, Japan Advanced Institute of Science and Technology (JAIST), 1-1 Asahidai, Nomi City, Ishikawa 923-1292, Japan
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Lu H, Conneely G, Pravda M, Guilbault GG. Screening of boldenone and methylboldenone in bovine urine using disposable electrochemical immunosensors. Steroids 2006; 71:760-7. [PMID: 16781744 DOI: 10.1016/j.steroids.2006.05.001] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/01/2005] [Revised: 05/02/2006] [Accepted: 05/03/2006] [Indexed: 11/29/2022]
Abstract
Electrochemical based immunosensors for the detection of boldenone and methylboldenone in bovine urine were described in this paper. The immunosensors were fabricated by immobilizing boldenone-bovine serum albumin conjugate on the surface of screen-printed electrodes (SPEs), and followed by the competition between the free analyte and coating conjugate with corresponding antibodies. The use of anti-species IgG-horseradish peroxidase conjugate determined the degree of competition. The electrochemical technique chosen was chronoamperometry, performed at a potential of +100 mV whereby the product of the catalysis of 3,3',5,5'-tetramethylbenzidine undergoes reduction produced by the enzyme label. The limits of detection of assay were 30.9+/-4.3 pg ml(-1) for boldenone and 120.2+/-8.2 pg ml(-1) for methylboldenone, respectively. Results of repeated analysis of each androgen carried out using three different batches of electrodes indicate suitable repeatability (EC(50)=1.0+/-0.3 ng ml(-1)(n=3, N=3), R(2)=0.969, R.S.D.=9.6% for boldenone and 1.5+/-0.3 ng ml(-1), 0.971, 10.5% for methylboldenone, respectively). Urine samples were determined directly after a single dilution step, omitting extraction and hydrolysis. This method offers the advantage to pick up both boldenone and its major metabolites in an efficient manner due to the high cross-reactivity pattern of alpha-boldenone with this antibody. The concentration of methylboldenone in urine detected by developed methods does indicate methylboldenone administration to heifers. Gas chromatography coupled to mass spectrometry analysis was performed to quantitate the individual metabolites present in urine samples, and results were validated with both ELISA and immunosensor data.
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Affiliation(s)
- Huihui Lu
- Sensor Development Group, Analytical & Biological Chemistry Research Facility, National University of Ireland, Cork, Ireland
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González-Martínez MA, Penalva J, Rodríguez-Urbis JC, Brunet E, Maquieira A, Puchades R. Immunosensors for pollutants working in organic media. Study of performances of different tracers with luminescent detection. Anal Bioanal Chem 2006; 384:1540-7. [PMID: 16501955 DOI: 10.1007/s00216-006-0306-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2005] [Revised: 12/20/2005] [Accepted: 01/05/2006] [Indexed: 10/25/2022]
Abstract
A comparative study of enzymatic and non-enzymatic labels combined with luminescence detection, developed for immunosensing of pesticide residues (carbaryl, 1-naphthol, irgarol 1051) in organic media, is presented. Peroxidase and alkaline phosphatase enzymes with fluorogenic (3-p-hydroxyphenylpropanoic acid) and luminogenic (AMPPD derivative) substrates, respectively, were assessed as enzymatic markers. As an alternative, terbium(III) chelate, with time-resolved fluorescence detection, was evaluated as a non-enzymatic label. The best sensitivity was achieved by use of alkaline phosphatase in an immunocomplex capture assay format (I (50) values 0.06, 0.27, and 7.45 microg L(-1) in buffer, 1:1 methanol-buffer, and methanol, respectively). Results were also good (I (50) 1.00 and 6.30 microg L(-1) for water and aqueous-organic mixture, respectively) for Tb(III) chelate in an immobilized conjugate assay format. Use of alkaline phosphatase label to measure carbaryl (100 ng L(-1)) in different spiked river water samples, after solid-phase extraction and analyte elution with an ethyl acetate-methanol mixture, resulted in recoveries ranging from 81 to 98%, with acceptable precision (CV 4-14%, n=4).
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Pemberton RM, Mottram TT, Hart JP. Development of a screen-printed carbon electrochemical immunosensor for picomolar concentrations of estradiol in human serum extracts. ACTA ACUST UNITED AC 2005; 63:201-12. [PMID: 15975659 DOI: 10.1016/j.jbbm.2005.05.002] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2004] [Revised: 04/30/2005] [Accepted: 05/02/2005] [Indexed: 11/28/2022]
Abstract
Investigations into the development of a prototype electrochemical immunosensor for estradiol (E(2)) are described. After optimising reagent loadings in a 96-well enzyme-linked immunosorbent assay (ELISA), antibodies (rabbit anti-mouse IgG and monoclonal mouse anti-E(2)) were immobilised by passive adsorption onto the surface of screen-printed carbon electrodes (SPCEs). A competitive immunoassay was then performed using an alkaline-phosphatase (ALP)-labelled E(2) conjugate. Calibration plots for E(2) buffer standards, performed colorimetrically on the SPCEs using a para-nitrophenyl phosphate substrate solution, were in good agreement with ELISA calibration plots. Electrochemical measurements were then performed using differential pulse voltammetry (DPV) following the production of 1-naphthol from 1-naphthyl phosphate. The calibration plot of DPV peak current versus E(2) concentration showed a measurable range of 25-500 pg/ml with a detection limit of 50 pg/ml. A coefficient of variation of between 13.0 and 15.6% was obtained for repeat measurements. The immunosensor was applied to the determination of E(2) in spiked serum, following an extraction step with diethyl ether. A mean recovery for the method of 102.5% was obtained with a CV of 19.1%. The options available for further development of the sensor regarding precision, limit of detection and direct sample analysis are discussed.
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Affiliation(s)
- R M Pemberton
- Centre for Analytical, Materials and Sensors Science, University of the West of England, Bristol BS16 1QY, UK
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Wilson MS, Rauh RD. Hydroquinone diphosphate: an alkaline phosphatase substrate that does not produce electrode fouling in electrochemical immunoassays. Biosens Bioelectron 2005; 20:276-83. [PMID: 15308232 DOI: 10.1016/j.bios.2004.01.013] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2003] [Revised: 01/19/2004] [Accepted: 01/22/2004] [Indexed: 10/26/2022]
Abstract
Hydroquinone diphosphate (HQDP) was synthesized and compared to phenyl phosphate (PP) and 1-naphthyl phosphate (NP) as a substrate for alkaline phosphatase (AP) under electrochemical immunoassay (EIA) conditions. Voltammetric and amperometric experiments showed that electrochemical oxidation of hydroquinone (HQ), which is the AP hydrolysis product of HQDP, did not produce electrode passivation, even with repeated biosensor use. In contrast, phenol and 1-naphthol, the hydrolysis products of PP and NP, respectively, were shown to be irreversibly oxidized on the electrode surfaces, and produced rapid electrode passivation, resulting in complete loss of electrode signal. When employed as AP substrate in an iridium oxide based EIA, HQDP produced significantly larger amperometric responses (117 microA/cm2) compared to PP (31 microA/cm2) and NP (27 microA/cm2). The results presented in this paper show that HQDP is an attractive alternative to commonly used AP substrates such as NP and PP. The substrate shows excellent hydrolytic stability, produces larger amperometric responses (than PP or NP), and does not produce sensor passivation.
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Affiliation(s)
- Michael S Wilson
- EIC Laboratories, Inc., 111 Downey Street, Norwood, MA 02062, USA.
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Caplen G, Mottram TT, Pickard AR, Milligan SR. A Biosensor‐Based Method for Non‐invasively Monitoring Wildlife Reproduction—The Field Vole (Microtus agrestis) as a Potential Biomarker of Environmental Disruption. ANAL LETT 2004. [DOI: 10.1081/al-120037598] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Nistor C, Christensen J, Ocio N, Nørgaard L, Emnéus J. Multivariate analysis to separate the signal given by cross-reactants in immunoassay with sample matrix dilution. Anal Bioanal Chem 2004; 380:898-907. [PMID: 15568136 DOI: 10.1007/s00216-004-2865-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2003] [Revised: 08/12/2004] [Accepted: 09/23/2004] [Indexed: 10/26/2022]
Abstract
This paper describes a new approach to achieve selectivity in an immunoassay by separating the signals given by two cross-reactive compounds present simultaneously in a complex sample matrix. The method is based on the sequential dilution of the sample containing a mixture of the two analytes, spiking each diluted sample with a reference compound, and the detection by enzyme-linked immunosorbent assay (ELISA). The obtained multivariate response was used for the individual calibrations of the assay for each of the two cross-reactants simultaneously by using principal component analysis (PCA) and partial least squares regression (PLSR) data modeling. The calibration models showed that the signal separation due the analytes 2,4-dinitrophenol (2,4-DNP) and 4-nitrophenol (4-NP) was possible with a prediction concentration error of 1.4 microM and 72 microM, respectively.
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Affiliation(s)
- Catalin Nistor
- Department of Analytical Chemistry, Lund University, P.O. Box 124, 221 00 Lund, Sweden
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Zhou YM, Hu SQ, Shen GL, Yu RQ. An amperometric immunosensor based on an electrochemically pretreated carbon-paraffin electrode for complement III (C3) assay. Biosens Bioelectron 2003; 18:473-81. [PMID: 12604265 DOI: 10.1016/s0956-5663(02)00146-x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
An electrochemical immunosensor based on the adsorption of anti-complement III antibody onto an electrochemical pretreated carbon-paraffin electrode has been proposed for the detection of complement III (C(3)). The competitive immunoassay format was adopted with horseradish peroxide-C(3) (HRP-C(3)) as a tracer, 3,3'5,5'-tetramethylbenzidine (TMB) and hydrogen peroxide as the enzyme substrates. In order to measure the amount of HRP-C(3) binding onto the electrode surface, the product of the enzyme catalytic reaction was detected at 100 mV (vs. Ag/AgCl reference electrode). The system was optimized to realize a reliable determination of C(3) in the range of 0.06-10 microg/ml. It exhibits some advantages, such as simplicity of fabrication, rapidity of measurement, and satisfactory sensitivity and reproducibility.
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Affiliation(s)
- Ya-Min Zhou
- State Key Laboratory for Chemo/Biosensing Technology and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, PR China
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Laschi S, Mascini M, Scortichini G, Fránek M, Mascini M. Polychlorinated biphenyls (PCBs) detection in food samples using an electrochemical immunosensor. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2003; 51:1816-1822. [PMID: 12643636 DOI: 10.1021/jf0208637] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
In this work, a disposable electrochemical immunosensor, based on a competitive assay scheme, was applied to detect polychlorinated biphenyls (PCBs) in food. For this purpose, antibodies against PCBs were directly immobilized onto the carbon surface of a disposable screen-printed electrode. A competition between the PCBs present in the sample and a fixed concentration of an enzyme-labeled PCB was realized and evaluated by electrochemical detection. Alkaline phosphatase was used as the enzyme label, coupled with differential pulse voltammetry (DPV) as the electrochemical technique. The immunosensor was tested on aroclor mixture detection (1242 and 1248) and then on some typologies of food samples to evaluate the possible application for real sample analysis. Samples analyzed were from different matrixes, such as sheep milk, bovine adipose tissue, and bovine muscle. Results obtained were compared with the accredited results according to ISO 17025 methods for PCB detection (HRGC-LRMS) as a confirmatory analysis. Preliminary results show the possibility to use this device as a screening method in food sample analysis. The negligible matrix effect observed may lead to a simplified extraction procedure, and considerable time and consumable savings are the immediate benefits given by the proposed method.
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Affiliation(s)
- Serena Laschi
- Dipartimento di Chimica, Università degli Studi di Firenze, Via della Lastruccia 3, 50019, Sesto Fiorentino, Firenze, Italy
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Gillis EH, Gosling JP, Sreenan JM, Kane M. Development and validation of a biosensor-based immunoassay for progesterone in bovine milk. J Immunol Methods 2002; 267:131-8. [PMID: 12165434 DOI: 10.1016/s0022-1759(02)00166-7] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
We have developed a rapid automated immunoassay, using the BIACORE surface plasmon resonance (SPR) biosensor, to measure progesterone in bovine milk. The assay was designed as an inhibition assay with progesterone covalently immobilised to the carboxymethyl dextran matrix of a CM5 sensor chip. A fixed amount of monoclonal anti-progesterone antibody 39C5H7 was mixed 9:1 with the sample and the amount of free antibody was then determined using biomolecular interaction analysis (BIA) by injection of the mixture over the immobilised progesterone sensor surface. The assay was designed to cover the concentration range 0.5 to 50 ng/ml. The limit of detection (LOD) was 3.56 ng/ml. Reproducibility of the assay was very good with both intra-assay and inter-assay coefficients of variation <5%. As results become available within minutes of injection and the procedure involves fully automated instrumentation, we believe that this BIA assay for progesterone in milk could be used in-line in the milking parlour and, thus, provide an important tool for reproductive management of dairy cattle to detect heat and predict pregnancy.
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Affiliation(s)
- Els H Gillis
- National Diagnostic Centre, National University of Ireland, Galway, Ireland
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Zhou YM, Liu GD, Wu ZY, Shen GL, Yu RQ. An amperometric immunosensor based on a conducting immunocomposite electrode for the determination of Schistosoma japonicum antigen. ANAL SCI 2002; 18:155-9. [PMID: 11874118 DOI: 10.2116/analsci.18.155] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
A renewable amperometric immunosensor based on a graphite-paraffin-Schistosoma japonicum antibody (SjAb) biocomposite electrode has been prepared for the detection of Schistosoma japonicum antigen (SjAg). Competitive ELISA was employed involving HRP-SjAg as a tracer and 3,3',5,5'-tetramethylbenzidine (TMB) as a substrate. The product of an enzyme catalytic reaction was detected at +0.1 V (vs. Ag/AgCl reference electrode) for measuring the amount of HRP-labeled SjAg binding to the electrode surface. The assay conditions were optimized, including the amount of SjAb loading in the electrode and HRP-SjAg in the incubation solution, the pH of the measuring solution and the incubation time. The measuring range was 0.5-30 microg/ml under the optimum conditions. Rabbit serum samples of different infection degree were measured, which demonstrated that the immunosensor meets the demands of clinical analysis. It exhibits some advantages, such as simplicity of fabrication, rapidity of measurement, and satisfactory sensitivity and reproducibility.
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Affiliation(s)
- Ya-Min Zhou
- State Key Laboratory for Chemo/Biosensing Technology and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha, PR China
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Pemberton RM, Hart JP, Mottram TT. An electrochemical immunosensor for milk progesterone using a continuous flow system. Biosens Bioelectron 2001; 16:715-23. [PMID: 11679249 DOI: 10.1016/s0956-5663(01)00212-3] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
An electrochemical biosensor for cow's milk progesterone has been developed and used in a competitive immunoassay under thin-layer, continuous-flow conditions. Single-use biosensors were fabricated by depositing anti-progesterone monoclonal antibody (mAb) onto screen-printed carbon electrodes (SPCEs). Three operational steps could be identified: (1) Competitive binding of sample/conjugate (alkaline-phosphatase-labelled progesterone, AP-prog) mixture, (2) establishment of a steady-state amperometric baseline current and (3), measurement of an amperometric signal in the presence of enzyme substrate (1-naphthyl phosphate, 1-NP). In the thin-layer cell, the enzyme product, 1-naphthol, showed electrochemical behaviour consistent with bulk conditions and gave a linear amperometric response under continuous-flow conditions (E(app)=+0.3 V vs. Ag/AgCl) over the range 0.1-1.0 microg/ml. After pre-incubating biosensors with progesterone standards, signal generation within the cell (substrate concentration=5 mM) was recorded amperometrically as rate (nA/s) or maximum current (i(max), nA). Response values for milk standards were approximately 50% of those prepared in buffer. In both cases, calibration plots over the range 0-50 ng/ml progesterone were obtained. By conducting sample binding under flowing conditions, only 7% of the previous response was obtained, even at a substrate concentration of 50 mM, resulting in low signal:noise ratio. Using a stop-flow arrangement (i.e. quiescent sample binding, followed by continuous flow), low-noise amperograms were obtained at [1-NP]=5 mM. Calibration plots were obtained over the range 0-25 ng/ml, with a coefficient of variation of 12.5% for five replicate real milk samples.
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Affiliation(s)
- R M Pemberton
- Faculty of Applied Sciences, University of the West of England, Bristol BS16 1QY, UK
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Velasco-Garcia MN, Mottram T. Biosensors in the livestock industry: an automated ovulation prediction system for dairy cows. Trends Biotechnol 2001; 19:433-4. [PMID: 11602290 DOI: 10.1016/s0167-7799(01)01841-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Biosensor technology can offer the livestock industry new types of monitoring and measuring devices of which the specificity, sensitivity, reproducibility, speed and ease of use exceed the current technology. Biosensors can be applied to the detection and identification of infectious diseases in livestock, contaminants and toxins in feed, therapeutic drug residues in animal husbandry and oestrus detection. Our team is applying biosensor technology to the livestock industry by developing a fully automated ovulation prediction system for dairy cows. The results from field-tests show that the progesterone biosensor can characterize the ovulation cycles of cows and detect pregnancy.
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Affiliation(s)
- J Wang
- Department of Chemistry and Biochemistry, New Mexico State University, Las Cruces 88003, USA
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Pemberton RM, Hart JP, Stoddard P, Foulkes JA. A comparison of 1-naphthyl phosphate and 4 aminophenyl phosphate as enzyme substrates for use with a screen-printed amperometric immunosensor for progesterone in cows' milk. Biosens Bioelectron 1999; 14:495-503. [PMID: 10451917 DOI: 10.1016/s0956-5663(99)00019-6] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
4-Aminophenyl phosphate (4-APP) and 1-naphthyl phosphate (1-NP) were compared as enzyme substrates for an amperometric milk progesterone biosensor utilising progesterone-conjugated alkaline phosphatase in a competitive immunoassay format. Cyclic voltammetry of the corresponding hydrolysis products, 4-aminophenol and 1-naphthol, at the surface of screen-printed carbon base transducers, uncoated or coated with anti-progesterone monoclonal antibody (mAb) showed well-defined anodic responses for both species, with the more sensitive being 4-aminophenol. Scan rate studies produced evidence that surface mAb could impede the diffusion of 4-aminophenol, but not 1-naphthol, toward the electrode surface. This was supported by computer simulation for the electrochemical rate constant (khet) using 4-aminophenol, which gave values at uncoated and mAb-coated electrodes of 6.5 x 10(-4) and 3.0 x 10(-4) cm s-1, respectively. The applied potential for oxidation of 4-aminophenol was 230 mV lower than for 1-naphthol. Nevertheless, by operating below +400 mV versus a saturated calomel reference electrode, it was possible to obtain a chronoamperometric signal for 1-naphthol in the absence of electrochemical interference from milk. Using mAb-coated SPCEs, calibration curves were obtained for progesterone in oestrus whole cow's milk spiked with standard concentrations over the range 0-50 ng/ml, using either 4-APP or 1NP as enzyme substrate. Precision values for triplicate sensors were 5.3-18.3% for 4-APP and 4.1-12.4% for 1-NP. An assay of real whole milk samples from different cows at various stages of the oestrus cycle produced correlations against a commercial EIA of r = 0.840 and 0.946 for 4-APP and 1-NP, respectively, 1-NP possesses the advantages over 4-APP of being inexpensive, easy to obtain and soluble (1-naphthol cf. 4-aminophenol) at high pH. From these observations, it is concluded that 1-NP is the preferred substrate for use with our proposed milk progesterone biosensor.
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Affiliation(s)
- R M Pemberton
- Faculty of Applied Sciences, University of the West of England, Bristol, UK
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