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Harris AR, McGivern P, Gilbert F, Van Bergen N. Defining Biomarkers in Stem Cell-Derived Tissue Constructs for Drug and Disease Screening. Adv Healthc Mater 2024:e2401433. [PMID: 38741544 DOI: 10.1002/adhm.202401433] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2024] [Revised: 04/24/2024] [Indexed: 05/16/2024]
Abstract
The development of stem cell-derived tissue constructs (SCTCs) for clinical applications, including regenerative medicine, drug and disease screening offers significant hope for detecting and treating intractable disorders. SCTCs display a variety of biomarkers that can be used to understand biological mechanisms, assess drug interactions, and predict disease. Although SCTCs can be derived from patients and share the same genetic make-up, they are nevertheless distinct from human patients in many significant ways, which can undermine the clinical significance of measurements in SCTCs. This study defines biomarkers, how they apply to SCTCs, and clarifies specific ethical issues associated with the use of SCTCs for drug and disease screening.
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Affiliation(s)
- Alexander R Harris
- Department of Biomedical Engineering, University of Melbourne, Melbourne, VIC, 3010, Australia
| | - Patrick McGivern
- School of Humanities and Social Inquiry, University of Wollongong, Wollongong, NSW, 2522, Australia
| | - Frederic Gilbert
- School of Humanities, University of Tasmania, Hobart, Tasmania, Australia
| | - Nicole Van Bergen
- Brain and Mitochondrial Research Group, Murdoch Children's Research Institute, Royal Children's Hospital, Melbourne, VIC, 3002, Australia
- Department of Paediatrics, University of Melbourne, Melbourne, VIC, 3002, Australia
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2
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Harris AR. Limitations in the electrochemical analysis of voltage transients. J Neural Eng 2024; 21:013003. [PMID: 38215494 DOI: 10.1088/1741-2552/ad1e23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2023] [Accepted: 01/12/2024] [Indexed: 01/14/2024]
Abstract
Objective. Chronopotentiometric voltage transients (VTs) are used to assess the performance of bionic electrodes. The data obtained from VTs are used to define the safe operating conditions of clinical devices. Various approaches to analysing VTs have been reported, and a number of limitations in the accuracy of the measurements in relation to electrode size have been noted previously.Approach. The impact of electronic hardware and electrode configuration on VTs is discussed.Main results. The slew rate, rise time, sample time, minimum pulse length and waveform averaging characteristics of the electronic hardware, and electrode configuration will impact on VT measurement accuracy. Subsequently, activation and polarisation voltage measurements, and the definition of safe stimulation levels can be affected by the electronic hardware and electrode configuration.Significance. This article has identified some limitations in the previous literature related to the measurement and reporting of VTs and subsequent analysis of access and polarisation voltages. Furthermore, the commonly used Shannon plot used to define safe stimulation protocols does not correct for uncompensated resistance, account for electrode roughness or changes in electrode configuration. The creation of a safe stimulation plot which has been corrected for uncompensated resistance would generate more widely applicable stimulation guidelines for clinical devices used in different anatomical locations such as endovascular neural interfaces.
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Affiliation(s)
- Alexander R Harris
- Department of Biomedical Engineering, University of Melbourne, Melbourne 3010, Australia
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Gilbert F, Harris AR, Viana JN. Addressing the nuances of racial disparities in deep brain stimulation. Lancet Reg Health Am 2023; 27:100614. [PMID: 37860750 PMCID: PMC10582734 DOI: 10.1016/j.lana.2023.100614] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 09/16/2023] [Revised: 09/25/2023] [Accepted: 09/26/2023] [Indexed: 10/21/2023]
Affiliation(s)
- Frederic Gilbert
- Philosophy Program, University of Tasmania, Hobart 7001, Australia
| | - Alexander R. Harris
- Department of Biomedical Engineering, University of Melbourne, Melbourne 3010, Australia
| | - John Noel Viana
- Australian National Centre for the Public Awareness of Science, ANU College of Science, The Australian National University, Australia
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Harris AR, Grayden DB, John SE. Electrochemistry in a Two- or Three-Electrode Configuration to Understand Monopolar or Bipolar Configurations of Platinum Bionic Implants. Micromachines (Basel) 2023; 14:722. [PMID: 37420955 DOI: 10.3390/mi14040722] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2023] [Revised: 03/21/2023] [Accepted: 03/22/2023] [Indexed: 07/09/2023]
Abstract
Electrodes are used in vivo for chemical sensing, electrophysiological recording, and stimulation of tissue. The electrode configuration used in vivo is often optimised for a specific anatomy and biological or clinical outcomes, not electrochemical performance. Electrode materials and geometries are constrained by biostability and biocompatibility issues and may be required to function clinically for decades. We performed benchtop electrochemistry, with changes in reference electrode, smaller counter-electrode sizes, and three- or two-electrode configurations. We detail the effects different electrode configurations have on typical electroanalytical techniques used on implanted electrodes. Changes in reference electrode required correction by application of an offset potential. In a two-electrode configuration with similar working and reference/counter-electrode sizes, the electrochemical response was dictated by the rate-limiting charge transfer step at either electrode. This could invalidate calibration curves, standard analytical methods, and equations, and prevent use of commercial simulation software. We provide methods for determining if an electrode configuration is affecting the in vivo electrochemical response. We recommend sufficient details be provided in experimental sections on electronics, electrode configuration, and their calibration to justify results and discussion. In conclusion, the experimental limitations of performing in vivo electrochemistry may dictate what types of measurements and analyses are possible, such as obtaining relative rather than absolute measurements.
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Affiliation(s)
- Alexander R Harris
- Department of Biomedical Engineering, University of Melbourne, Melbourne 3010, Australia
| | - David B Grayden
- Department of Biomedical Engineering, University of Melbourne, Melbourne 3010, Australia
- Graeme Clark Institute, University of Melbourne, Melbourne 3010, Australia
| | - Sam E John
- Department of Biomedical Engineering, University of Melbourne, Melbourne 3010, Australia
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Harris AR, Walker MJ, Gilbert F. Ethical and regulatory issues of stem cell-derived 3-dimensional organoid and tissue therapy for personalised regenerative medicine. BMC Med 2022; 20:499. [PMID: 36575403 PMCID: PMC9795739 DOI: 10.1186/s12916-022-02710-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/17/2022] [Accepted: 12/14/2022] [Indexed: 12/29/2022] Open
Abstract
BACKGROUND Regenerative medicine has the potential to treat genetic disorders and replace damaged or missing tissue. The use of donor or animal tissue raises many well-known issues, including limited tissue availability, the possibility of rejection and patient infection. Stem cell therapy raised hope of overcoming these issues, but created new risks including tumour formation and limited benefit if the desired target tissue does not form. The recent development of 3-dimensional tissues, including organoids, allows the creation of more complex tissues for personalised regenerative medicine. METHODS This article details the potential health risks of 3-dimensional organoid and tissue therapy versus dissociated stem cell therapy. The current ethical and regulatory issues surrounding 3-dimensional organoid and tissue therapy are presented with a focus on the highly influential FDA and International Society of Stem Cell Research (ISSCR) guidelines. CONCLUSIONS The potential use of 3-dimensional organoid and tissue therapy may deliver greater patient benefits than other regenerative medicine approaches, but raises new health and ethical risks. Preclinical testing of these therapies will not mitigate some of their risks; they may only be understood after first-in-human trials. The potential irreversibility and high risk of these therapies affects how clinical trials should be structured, including post-trial care for participants.
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Affiliation(s)
- Alexander R Harris
- Department of Biomedical Engineering, University of Melbourne, Melbourne, 3010, Australia.
| | - Mary Jean Walker
- Department of Politics, Media, and Philosophy, La Trobe University, Bundoora, Victoria, 3086, Australia
| | - Frederic Gilbert
- Ethics Lab, School of Humanities, University of Tasmania, Hobart, Tasmania, Australia
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Gilbert F, Tubig P, Harris AR. Not-So-Straightforward Decisions to Keep or Explant a Device: When Does Neural Device Removal Become Patient Coercion? AJOB Neurosci 2022; 13:230-232. [PMID: 36272162 DOI: 10.1080/21507740.2022.2126544] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Harris AR, Walker MJ, Gilbert F, McGivern P. Investigating the feasibility and ethical implications of phenotypic screening using stem cell-derived tissue models to detect and manage disease. Stem Cell Reports 2022; 17:1023-1032. [PMID: 35487211 PMCID: PMC9133639 DOI: 10.1016/j.stemcr.2022.04.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2021] [Revised: 04/01/2022] [Accepted: 04/04/2022] [Indexed: 12/19/2022] Open
Abstract
Stem-cell-derived tissue models generated from sick people are being used to understand human development and disease, drug development, and drug screening. However, it is possible to detect disease phenotypes before a patient displays symptoms, allowing for their use as a disease screening tool. This raises numerous issues, some of which can be addressed using similar approaches from genetic screenings, while others are unique. One issue is the relationship between disease disposition, biomarker detection, and patient symptoms and how tissue models could be used to define disease. Other issues include decisions of when to screen, what diseases to screen for, and what treatment options should be offered.
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Affiliation(s)
- Alexander R Harris
- Aikenhead Centre for Medical Discovery, Faculty of Medicine, Dentistry and Health Sciences, University of Melbourne, Melbourne, VIC 3010, Australia.
| | - Mary Jean Walker
- Department of Politics, Media, and Philosophy, La Trobe University, Bundoora, VIC 3086, Australia
| | - Frederic Gilbert
- School of Humanities, University of Tasmania, Hobart, TAS, Australia
| | - Patrick McGivern
- School of Humanities and Social Inquiry, University of Wollongong, Wollongong, NSW 2522, Australia
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Hage F, Harris AR, Clerc O, Altibi A, Hage A, Hamaya R, Papatheodorou S. Transfemoral versus transapical approach for transcatheter aortic valve implantation: a systematic review and meta-analysis of adjusted studies. Eur Heart J 2021. [DOI: 10.1093/eurheartj/ehab724.1624] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Abstract
Background
In selected patients with severe aortic stenosis, transcatheter aortic valve implantation (TAVI), via either transfemoral (TF) or transapical (TA) access, offers a less invasive alternative to standard surgical replacement. Comparison of TF- vs. TA-TAVI is usually confounded by the higher comorbidities of patients undergoing TA-TAVI, rendering the observed comparison of the TF- vs. TA-approach unclear. The present meta-analysis provides updated evidence of this comparison by focusing on studies reporting adjusted outcomes.
Methods
A systematic review of the literature was performed in MEDLINE, EMBASE, Web of Science, clinicaltrials.gov, and Cochrane database. We only included studies in which the comparison between TF- and TA-TAVI was adjusted for potential confounders. Primary outcomes were early and mid-term mortality. Secondary outcomes included cardiovascular events, bleeding, pacemaker, and acute kidney injury. Survival data was either obtained directly from reported outcomes or estimated from Kaplan-Meier curves. Meta-regression was used to adjust for follow-up duration. Meta-analyses were performed using random effects models on odds ratios (OR) and hazard ratios (HR). The protocol was registered on PROSPERO (ID: CRD42020218163).
Results
A total of 24 studies with 36,158 patients were included in the present analyses. Of these studies, 7 used propensity score adjustment techniques and 17 used multivariable regression. TA-TAVI was associated with significantly higher postoperative mortality at 30 days (OR=1.67; 95% CI, 1.34 to 2.09; p<0.001) and 1 year (HR, 1.36; 95% CI, 1.21 to 1.53; p<0.001). However, meta-analysis of studies censoring patients who died in the first 30 days showed no significant difference in 1 year mortality by access route (HR, 1.20; 95% CI, 0.95 to 1.52; p=0.13). TA-approach was associated with increased perioperative surgical complications, such as bleeding (OR, 1.46, 95% CI, 1.09 to 1.96; p=0.012), acute kidney injury (OR, 2.31, 95% CI 1.60 to 3.33; p=0.001), and myocardial infarction (OR, 1.83, 95% CI 1.06 to 3.16; p=0.029). TA-TAVI was associated with reduced vascular complications (OR, 0.32, 95% CI 0.18–0.56; p<0.001), late postoperative aortic regurgitation (OR, 0.48, 95% CI 0.30 to 0.75; p=0.001), and a trend towards less pacemaker requirement (OR, 0.80, 95% CI 0.60–1.08, p=0.15).
Conclusions
Based on this meta-analysis of adjusted studies, a TA approach is associated with higher early and mid-term mortality compared to TF-TAVI. Excess mortality is likely driven by higher perioperative bleeding, renal complications and myocardial infarction. TA-TAVI did confer some benefits, such as reduced vascular complications, late postoperative aortic regurgitation, and a trend towards less pacemaker requirement. The optimal TAVI route should be based on individualized assessment by a multidisciplinary team. Longer follow-up and randomized studies are needed to ascertain long-term outcomes.
Funding Acknowledgement
Type of funding sources: None. Figure 1Figure 2
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Affiliation(s)
- F Hage
- London Health Sciences Centre, Cardiac surgery, London, Canada
| | - A R Harris
- Harvard T. H. Chan School of Public Health, Epidemiology, Boston, United States of America
| | - O Clerc
- University Hospital Basel, Basel, Switzerland
| | - A Altibi
- Harvard T. H. Chan School of Public Health, Epidemiology, Boston, United States of America
| | - A Hage
- London Health Sciences Centre, Cardiac surgery, London, Canada
| | - R Hamaya
- Harvard T. H. Chan School of Public Health, Epidemiology, Boston, United States of America
| | - S Papatheodorou
- Harvard T. H. Chan School of Public Health, Epidemiology, Boston, United States of America
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Harris AR, Carter P, Cowan R, Wallace GG. Impact of Protein Fouling on the Charge Injection Capacity, Impedance, and Effective Electrode Area of Platinum Electrodes for Bionic Devices. ChemElectroChem 2021. [DOI: 10.1002/celc.202001574] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Affiliation(s)
- Alexander R. Harris
- Aikenhead Centre for Medical Discovery ARC Centre of Excellence for Electromaterials Science Faculty of Medicine, Dentistry and Health Sciences University of Melbourne Melbourne Vic 3010 Australia
- The HEARing CRC University of Melbourne 550 Swanston St Melbourne 3010 Australia
| | - Paul Carter
- Cochlear Ltd Macquarie University 1 University Ave Sydney NSW 2109 Australia
| | - Robert Cowan
- The HEARing CRC University of Melbourne 550 Swanston St Melbourne 3010 Australia
- Department of Audiology & Speech Pathology University of Melbourne 550 Swanston St Melbourne 3010 Australia
| | - Gordon G. Wallace
- ARC Centre of Excellence for Electromaterials Science Intelligent Polymer Research Institute University of Wollongong Wollongong, NSW 2522 Australia
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Abstract
This review details some peripheral nervous system (PNS) targets and electrode designs used for electrical stimulation. It investigates limitations in current knowledge of safe electrical stimulation and possible future electrode developments. Current PNS targets are large, leading to poor resolution and off-target side-effects. Most clinical devices are platinum or platinum/iridium embedded in an insulation material. Their safety is usually guided by the Shannon plot, which is not valid for the PNS. New electrode designs are needed to target smaller nerve fibers, enabling higher resolution electrical therapies with fewer off-target side-effects. Damage can occur through biological and electrochemical mechanisms. Greater mechanistic understanding is required to ensure safe and efficacious, long-term electrical stimulation with new electrode materials, geometries and stimulation waveforms.
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Affiliation(s)
- Alexander R Harris
- ARC Centre of Excellence for Electromaterials Science, Intelligent Polymer Research Institute, University of Wollongong, NSW 2522, Australia
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Farajikhah S, Innis PC, Paull B, Wallace GG, Harris AR. Facile Development of a Fiber-Based Electrode for Highly Selective and Sensitive Detection of Dopamine. ACS Sens 2019; 4:2599-2604. [PMID: 31564101 DOI: 10.1021/acssensors.9b01583] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A facile one-step method was used to create a selective and sensitive electrode for dopamine (DA) detection based upon a stainless steel (SS) filament substrate and reduced graphene oxide (rGO). The electrode successfully and selectively detects DA in the presence of uric acid and ascorbic acid without the need for a Nafion coating. The proposed electrode is easy to fabricate, low-cost, flexible, and strong. The rGO-SS electrode could also be incorporated into a three-dimensional braided structure enabling DA detection in a two-electrode fiber system. The sensor is an excellent candidate for production of an affordable, robust, and flexible wearable and portable sensor and expands the application of textiles in point of care diagnostic devices.
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Affiliation(s)
- Syamak Farajikhah
- Institute of Photonics and Optical Sciences (IPOS), School of Physics, The University of Sydney, Sydney, New South Wales, 2006, Australia
| | | | - Brett Paull
- Australian Centre for Research on Separation Science (ACROSS) and ARC Centre of Excellence for Electromaterials Science (ACES), School of Natural Sciences, University of Tasmania, Hobart, Tasmania, 7005, Australia
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Abstract
Here we describe emergent properties of the brain and the key challenges associated with modelling them in vitro. Modeling emergent properties of the brain will provide insights into brain function, development, and disease.
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Affiliation(s)
- Alexander R Harris
- ARC Centre of Excellence for Electromaterials Science, Intelligent Polymer Research Institute, University of Wollongong, Wollongong, New South Wales, Australia
| | - Patrick McGivern
- School of Humanities and Social Inquiry, University of Wollongong, Wollongong, New South Wales, Australia
| | - Lezanne Ooi
- Illawarra Health and Medical Research Institute, Wollongong, Wollongong, New South Wales, Australia.,School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, New South Wales, Australia
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Abstract
Recordings of neural activity can be used to aid communication, control prosthetic devices or alleviate disease symptoms. Chronic recordings require a high signal-to-noise ratio that is stable for years. Current cortical devices generally fail within months to years after implantation. Development of novel devices to increase lifetime requires valid testing protocols and a knowledge of the critical parameters controlling electrophysiological performance. Here we present electrochemical and electrophysiological protocols for assessing implantable electrodes. Biological noise from neural recording has significant impact on signal-to-noise ratio. A recently developed surgical approach was utilised to reduce biological noise. This allowed correlation of electrochemical and electrophysiological behaviour. The impedance versus frequency of modified electrodes was non-linear. It was found that impedance at low frequencies was a stronger predictor of electrophysiological performance than the typically reported impedance at 1 kHz. Low frequency impedance is a function of electrode area, and a strong correlation of electrode area with electrophysiological response was also seen. Use of these standardised testing protocols will allow future devices to be compared before transfer to preclinical and clinical trials.
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Affiliation(s)
- Alexander R Harris
- ARC Centre of Excellence for Electromaterials Science, Intelligent Polymer Research Institute, University of Wollongong, NSW 2522, Australia.
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Harris AR, Newbold C, Carter P, Cowan R, Wallace GG. Using Chronopotentiometry to Better Characterize the Charge Injection Mechanisms of Platinum Electrodes Used in Bionic Devices. Front Neurosci 2019; 13:380. [PMID: 31118879 PMCID: PMC6508053 DOI: 10.3389/fnins.2019.00380] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2018] [Accepted: 04/02/2019] [Indexed: 11/13/2022] Open
Abstract
The safe charge injection capacity and charge density of neural stimulating electrodes is based on empirical evidence obtained from stimulating feline cortices. Stimulation induced tissue damage may be caused by electrochemical or biological mechanisms. Separating these mechanisms requires greater understanding of charge transfer at the electrode-tissue interface. Clinical devices typically use a biphasic waveform with controlled current. Therefore, the charge injection mechanism and charge injection capacity of platinum was assessed on a commercial potentiostat by chronopotentiometry (controlled current stimulation). Platinum is a non-ideal electrode, charge injection by chronopotentiometry can be passed via capacitive and Faradaic mechanisms. Electrodes were tested under a variety of conditions to assess the impact on charge injection capacity. The change in electrode potential (charge injection capacity) was affected by applied charge density, pulse length, pulse polarity, electrode size, polishing method, electrolyte composition, and oxygen concentration. The safe charge injection capacity and charge density could be increased by changing the electrode-solution composition and stimulation parameters. However, certain conditions (e.g., acid polished electrodes) allowed the electrode to exceed the water electrolysis potential despite the stimulation protocol being deemed safe according to the Shannon plot. Multiple current pulses led to a shift or ratcheting in electrode potential due to changes in the electrode-solution composition. An accurate measure of safe charge injection capacity and charge density of an implantable electrode can only be obtained from suitable conditions (an appropriately degassed electrolyte and clinically relevant electrode structure). Cyclic voltammetric measurement of charge storage capacity can be performed on implantable electrodes, but will not provide information on electrode stability to multiple chronopotentiometric pulses. In contrast, chronopotentiometry will provide details on electrode stability, but the minimum time resolution of typical commercial potentiostats (ms range) is greater than used in a clinical stimulator (μs range) so that extrapolation to short stimulation pulses is required. Finally, an impedance test is typically used to assess clinical electrode performance. The impedance test is also based on a biphasic chronopotentiometic waveform where the measured potential is used to calculate an impedance value. Here it is shown that the measured potential is a function of many parameters (solution composition, electrode area, and surface composition). Subsequently, impedance test results allow electrode comparison and to indicate electrode failure, but use of Ohm's law to calculate an impedance value is not valid.
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Affiliation(s)
- Alexander R. Harris
- ARC Centre of Excellence for Electromaterials Science, Intelligent Polymer Research Institute, University of Wollongong, Wollongong, NSW, Australia
- The HEARing CRC, University of Melbourne, Melbourne, VIC, Australia
| | - Carrie Newbold
- The HEARing CRC, University of Melbourne, Melbourne, VIC, Australia
- Department of Audiology and Speech Pathology, University of Melbourne, Melbourne, VIC, Australia
| | - Paul Carter
- Cochlear, Ltd., Macquarie University, Sydney, NSW, Australia
| | - Robert Cowan
- The HEARing CRC, University of Melbourne, Melbourne, VIC, Australia
- Department of Audiology and Speech Pathology, University of Melbourne, Melbourne, VIC, Australia
| | - Gordon G. Wallace
- ARC Centre of Excellence for Electromaterials Science, Intelligent Polymer Research Institute, University of Wollongong, Wollongong, NSW, Australia
- The HEARing CRC, University of Melbourne, Melbourne, VIC, Australia
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Harris AR, Newbold C, Carter P, Cowan R, Wallace GG. Measuring the effective area and charge density of platinum electrodes for bionic devices. J Neural Eng 2018; 15:046015. [DOI: 10.1088/1741-2552/aaba8b] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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Abstract
Iridium oxide is routinely used for bionic applications owing to its high charge injection capacity. The electrode impedance at 1 kHz is typically reported to predict neural recording performance. In this article, the impedance of activated iridium oxide films (AIROFs) has been examined. The impedance of unactivated iridium electrodes was half that of platinum electrodes of similar geometry, indicating some iridium oxide was present on the electrode surface. A two time constant equivalent circuit was used to model the impedance of activated iridium. The impedance at low and intermediate frequencies decreased with increasing number of activation pulses and total activation charge. The impedance at 12 Hz correlated with the steady-state diffusion electroactive area. The impedance at 12 Hz also correlated with the charge density of the electrode. The high charge density and low impedance of AIROFs may provide improved neural stimulation and recording properties compared with typically used platinum electrodes.
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Harris AR, Molino PJ, Paolini AG, Wallace GG. Effective Area and Charge Density of Chondroitin Sulphate Doped PEDOT Modified Electrodes. Electrochim Acta 2016. [DOI: 10.1016/j.electacta.2016.03.038] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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Zhang B, Molino PJ, Harris AR, Yue Z, Moulton SE, Wallace GG. Conductive and protein resistant polypyrrole films for dexamethasone delivery. J Mater Chem B 2016; 4:2570-2577. [PMID: 32263280 DOI: 10.1039/c5tb00574d] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The development of inherently conducting polymers as controllable/programmable drug delivery systems has attracted significant interest in medical bionics, and the interfacial properties of the polymers, in particular, protein adsorption characteristics, is integral to the stability of the overall performance. Herein we report a hybrid conducting system based on polypyrrole doped with an anti-inflammatory prodrug, dexamethasone phosphate (DexP), upon which post-surface modification was conducted to render the polymer more biostable. We firstly investigated the influence of the current density and DexP concentration on the physiochemical properties and surface characteristics of the resulting polymer films. Films were then surface modified with thiolated poly(ethylene glycol). The influence of surface modification on inhibition of nonspecific protein adsorption to the polymer surfaces was evaluated using electrochemistry and quartz crystal microbalance. Furthermore, studies were undertaken to examine the effect of surface coatings on the drug release behaviour triggered by electrical stimulation. Our results demonstrated that both the physiochemical and interfacial properties of conducting polymers can be modulated to enhance the performance of the materials as biocompatible drug delivery systems. This provides important insight into molecular engineering of conducting polymers to facilitate their applications in medical bionics.
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Affiliation(s)
- B Zhang
- ARC Centre of Excellence for Electromaterials Science, Intelligent Polymer Research Institute, AIIM Faculty, Innovation Campus, University of Wollongong, NSW 2500, Australia.
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Harris AR, Molino PJ, Kapsa RMI, Clark GM, Paolini AG, Wallace GG. Correction to Optical and Electrochemical Methods for Determining the Effective Area and Charge Density of Conducting Polymer Modified Electrodes for Neural Stimulation. Anal Chem 2015; 87:11600. [DOI: 10.1021/acs.analchem.5b03915] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Harris AR, Molino PJ, Kapsa RMI, Clark GM, Paolini AG, Wallace GG. Correlation of the impedance and effective electrode area of doped PEDOT modified electrodes for brain–machine interfaces. Analyst 2015; 140:3164-74. [DOI: 10.1039/c4an02362e] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
An analytical solution to impedance allows correlation of an effective electrode area with the impedance and phase angle at low frequencies.
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Affiliation(s)
| | - Paul J. Molino
- Intelligent Polymer Research Institute
- University of Wollongong
- Wollongong
- Australia
| | - Robert M. I. Kapsa
- Intelligent Polymer Research Institute
- University of Wollongong
- Wollongong
- Australia
- Department of Neurosciences
| | - Graeme M. Clark
- School of Engineering
- University of Melbourne
- Parkville
- Australia
| | - Antonio G. Paolini
- Health Innovations Research Institute
- College of Science
- Engineering and Health
- RMIT University
- Bundoora
| | - Gordon G. Wallace
- Intelligent Polymer Research Institute
- University of Wollongong
- Wollongong
- Australia
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Harris AR, Molino PJ, Kapsa RMI, Clark GM, Paolini AG, Wallace GG. Optical and Electrochemical Methods for Determining the Effective Area and Charge Density of Conducting Polymer Modified Electrodes for Neural Stimulation. Anal Chem 2014; 87:738-46. [DOI: 10.1021/ac503733s] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Alexander R. Harris
- School of Psychological
Science, La Trobe University, Bundoora, Melbourne, Victoria 3086, Australia
| | - Paul J. Molino
- Intelligent Polymer
Research Institute, University of Wollongong, Wollongong, NSW 2522, Australia
| | - Robert M. I. Kapsa
- Intelligent Polymer
Research Institute, University of Wollongong, Wollongong, NSW 2522, Australia
- Department
of Neurosciences, St. Vincents Hospital, Melbourne, Victoria 3065, Australia
- Department of Medicine, University of Melbourne, Fitzroy, Victoria 3065, Australia
| | - Graeme M. Clark
- School of Engineering, University of Melbourne, Parkville, Victoria 3010, Australia
| | - Antonio G. Paolini
- Health Innovations Research
Institute, College of Science, Engineering and Health, RMIT University, Bundoora, Victoria 3083, Australia
| | - Gordon G. Wallace
- Intelligent Polymer
Research Institute, University of Wollongong, Wollongong, NSW 2522, Australia
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Harris AR, Morgan SJ, Wallace GG, Paolini AG. A method for systematic electrochemical and electrophysiological evaluation of neural recording electrodes. J Vis Exp 2014. [PMID: 24637902 DOI: 10.3791/51084] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
New materials and designs for neural implants are typically tested separately, with a demonstration of performance but without reference to other implant characteristics. This precludes a rational selection of a particular implant as optimal for a particular application and the development of new materials based on the most critical performance parameters. This article develops a protocol for in vitro and in vivo testing of neural recording electrodes. Recommended parameters for electrochemical and electrophysiological testing are documented with the key steps and potential issues discussed. This method eliminates or reduces the impact of many systematic errors present in simpler in vivo testing paradigms, especially variations in electrode/neuron distance and between animal models. The result is a strong correlation between the critical in vitro and in vivo responses, such as impedance and signal-to-noise ratio. This protocol can easily be adapted to test other electrode materials and designs. The in vitro techniques can be expanded to any other nondestructive method to determine further important performance indicators. The principles used for the surgical approach in the auditory pathway can also be modified to other neural regions or tissue.
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Affiliation(s)
- Alexander R Harris
- School of Psychological Science, La Trobe University; ARC Centre of Excellence for Electromaterials Science;
| | - Simeon J Morgan
- School of Psychological Science, La Trobe University; ARC Centre of Excellence for Electromaterials Science
| | | | - Antonio G Paolini
- School of Psychological Science, La Trobe University; ARC Centre of Excellence for Electromaterials Science; Health Innovations Research Institute, College of Science, Engineering, and Health, RMIT University
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Bayley PJ, Isaac L, Kong JY, Adamson MM, Ashford JW, Mahoney LA, Beltran M, Brown-Elhillali A, Held A, Ajayi A, Belcher H, Bond A, Mason H, Lemaster C, Shaw S, Mullin C, Holick E, Saper R, Braun TD, Riley KE, Park CL, Trehern AE, Davis MB, Mastronardi EL, Butzer B, Khalsa SBS, Shorter SM, Reinhardt KM, Cope S, Cheung C, Justice C, Wyman J, Cook-Cottone CP, Daly LA, Haden SC, Hagins M, Danhauer SC, Griffin LP, Avis NE, Sohl SJ, Lawrence J, Jesse MT, Addington EL, Messino MJ, Giguere JK, Lucas SL, Wiliford SK, Shaw E, de Manincor M, Bensoussan A, Smith C, Fahey P, Bourchier S, Desrochers DIM, Viswanathan S, Partharasathy BR, Doherty K, Moye J, Walsh C, Pokaski-Azar J, Gosian J, Chapman J, King K, Sohl S, Danhauer S, Dunbar E, Gabriel MG, Huebner M, Hofmann SG, Khalsa SBS, Gaskins RB, Jennings E, Thind H, Fava JL, Hartman S, Bock BC, Gramann P, Haaz S, Bingham CO, Bartlett SJ, Hagins M, States R, Selfe T, Innes K, Harris AR, Jennings PA, Abenavoli RM, Katz DA, Hudecek KM, Greenberg MT, Jeter PE, Nkodo AF, Haaz S, Dagnelie G, Keosaian JE, Lemaster CM, Chao M, Saper RB, King KD, Gosian J, Doherty K, Walsh C, Pokaski Azar J, Chapman J, Danhauer SC, Moye J, Kinser P, Bourguignon C, Taylor A, Mahoney LA, Bayley PJ, Collery LM, Menzies-Toman D, Nilsson M, Frykman V, Noggle JJ, Braun T, Khalsa SBS, Nosaka M, Okamura H, Fukatu N, Potts A, Weidknecht K, Coulombe S, Davies B, Ryan C, Day D, Reale J, Staples JK, Knoefel J, Herman C, Riley KE, Park CL, Bedesin EY, Stewart VM, Riley KE, Braun TD, Park CL, Pescatello LS, Davis MB, Trehern AE, Mastronardi EL, Rioux J, Rosen RK, Thind H, Gaskins R, Jennings E, Morrow K, Williams D, Bock B, Rousseau D, Jackson E, Schmid AA, Miller KK, Van Puymbroeck M, Debaun EL, Schalk N, Dierks TD, Altenburger P, Damush T, Williams LS, Selman L, Citron T, Howie-Esquivel J, McDermott K, Milic M, Donesky D, Shook A, Ruzic R, Galloway F, Van Puymbroeck M, Miller KK, Schalk N, Schmid AA, Ward LJ, Stebbings S, Sherman K, Cherkin D, Baxter GD, West JI, Duffy N, Liang B. 2013 SYR Accepted Poster Abstracts. Int J Yoga Therap 2013; 23:32-53. [PMID: 24016822] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
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Zhang J, Harris AR, Cattrall RW, Bond AM. Voltammetric ion-selective electrodes for the selective determination of cations and anions. Anal Chem 2010; 82:1624-33. [PMID: 20121252 DOI: 10.1021/ac902296r] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
A general theory has been developed for voltammetric ion sensing of cations and anions based on the use of an electrode coated with a membrane containing an electroactive species, an ionophore, and a supporting electrolyte dissolved in a plasticizer. In experimental studies, a membrane coated electrode is fabricated by the drop coating method. In one configuration, a glassy carbon electrode is coated with a poly(vinyl chloride) based membrane, which contains the electroactive species, ionophore, plasticizer and supporting electrolyte. In the case of a cation sensor, ionophore facilitated transfer of the target cation from the aqueous solution to the membrane phase occurs during the course of the reduction of the electroactive species present in the membrane in order to maintain charge neutrality. The formal potential is calculated from the cyclic voltammogram as the average of the reduction and oxidation peak potentials and depends on the identity and concentration of the ion present in the aqueous solution phase. A plot of the formal potential versus the logarithm of the concentration exhibits a close to Nernstian slope of RT/F millivolts per decade change in concentration when the concentration of K(+) and Na(+) is varied over the concentration range of 0.1 mM to 1 M when K(+) or Na(+) ionophores are used in the membrane. The slope is close to RT/2F millivolts for a Ca(2+) voltammetric ion-selective electrode fabricated using a Ca(2+) ionophore. The sensor measurement time is only a few seconds. Voltammetric sensors for K(+), Na(+), and Ca(2+) constructed in this manner exhibit the sensitivity and selectivity required for determination of these ions in environmentally and biologically important matrixes. Analogous principles apply to the fabrication of anion voltammetric sensors.
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Affiliation(s)
- Jie Zhang
- School of Chemistry and ARC Centre for Green Chemistry, Monash University, Clayton, Victoria, 3800, Australia
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Notara M, Alatza A, Gilfillan J, Harris AR, Levis HJ, Schrader S, Vernon A, Daniels JT. In sickness and in health: Corneal epithelial stem cell biology, pathology and therapy. Exp Eye Res 2010; 90:188-95. [PMID: 19840786 DOI: 10.1016/j.exer.2009.09.023] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2009] [Accepted: 09/30/2009] [Indexed: 12/12/2022]
Affiliation(s)
- M Notara
- Department of Ocular Biology and Therapeutics, UCL Institute of Ophthalmology, Cells for Sight Transplantation & Research Programme, 11-43 Bath Street, London EC1V 9EL, UK.
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Harris AR, Bowley DM, Stannard A, Kurrimboccus S, Geh JI, Karandikar S. Socioeconomic deprivation adversely affects survival of patients with rectal cancer. Br J Surg 2009; 96:763-8. [DOI: 10.1002/bjs.6621] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Abstract
Background
The aim was to examine the influence of socioeconomic deprivation on stage at presentation, perioperative mortality, permanent stoma rates and overall survival in patients with rectal cancer.
Methods
Data on patient demographics, mode and stage of presentation, and short- and longer-term outcomes were extracted from a database of patients with rectal cancer. Comparisons were made after stratification into quintiles of socioeconomic deprivation.
Results
In total 486 patients were identified. Fewer patients from the most deprived group than from the least deprived group underwent resectional surgery (79·2 versus 93 per cent; P = 0·005). Permanent stoma rates among patients who had surgery were 40·8 and 30 per cent respectively (P = 0·110). The overall 5-year survival rate was 32·8 per cent for the most deprived compared with 64·0 per cent for the least deprived patients (P < 0·001). Respective rates for those who underwent resectional surgery were 49·9 and 72 per cent (P = 0·030).
Conclusion
In rectal cancer, socioeconomic deprivation appears to be associated with poorer outcomes and survival. This has important implications for healthcare planning.
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Affiliation(s)
- A R Harris
- Department of General Surgery, Birmingham Heartlands Hospital, Heart of England NHS Foundation Trust, Bordesley Green East, Birmingham B9 5SS, UK
| | - D M Bowley
- Department of General Surgery, Birmingham Heartlands Hospital, Heart of England NHS Foundation Trust, Bordesley Green East, Birmingham B9 5SS, UK
| | - A Stannard
- Department of General Surgery, Birmingham Heartlands Hospital, Heart of England NHS Foundation Trust, Bordesley Green East, Birmingham B9 5SS, UK
| | - S Kurrimboccus
- Department of General Surgery, Birmingham Heartlands Hospital, Heart of England NHS Foundation Trust, Bordesley Green East, Birmingham B9 5SS, UK
| | - J I Geh
- Oncology, Birmingham Heartlands Hospital, Heart of England NHS Foundation Trust, Bordesley Green East, Birmingham B9 5SS, UK
| | - S Karandikar
- Department of General Surgery, Birmingham Heartlands Hospital, Heart of England NHS Foundation Trust, Bordesley Green East, Birmingham B9 5SS, UK
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Konash A, Harris AR, Zhang J, Elton D, Hyland M, Kennedy G, Bond AM. Theoretical and experimental evaluation of screen-printed tubular carbon ink disposable sensor well electrodes by dc and Fourier transformed ac voltammetry. J Solid State Electrochem 2008. [DOI: 10.1007/s10008-008-0751-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Harris AR, Zhang J, Konash A, Elton D, Hyland M, Bond AM. Efficient strategy for quality control of screen-printed carbon ink disposable sensor electrodes based on simultaneous evaluation of resistance, capacitance and Faradaic current by Fourier transform AC voltammetry. J Solid State Electrochem 2008. [DOI: 10.1007/s10008-008-0524-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Qu X, Nafady A, Mechler A, Zhang J, Harris AR, O’Mullane AP, Martin LL, Bond AM. AFM study of morphological changes associated with electrochemical solid–solid transformation of three-dimensional crystals of TCNQ to metal derivatives (metal = Cu, Co, Ni; TCNQ = tetracyanoquinodimethane). J Solid State Electrochem 2007. [DOI: 10.1007/s10008-007-0423-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Nafady A, Bond AM, Bilyk A, Harris AR, Bhatt AI, O'Mullane AP, De Marco R. Tuning the Electrocrystallization Parameters of Semiconducting Co[TCNQ]2-Based Materials To Yield either Single Nanowires or Crystalline Thin Films. J Am Chem Soc 2007; 129:2369-82. [PMID: 17263534 DOI: 10.1021/ja067219j] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Electrocrystallization of single nanowires and/or crystalline thin films of the semiconducting and magnetic Co[TCNQ]2(H2O)2 (TCNQ=tetracyanoquinodimethane) charge-transfer complex onto glassy carbon, indium tin oxide, or metallic electrodes occurs when TCNQ is reduced in acetonitrile (0.1 M [NBu4][ClO4]) in the presence of hydrated cobalt(II) salts. The morphology of the deposited solid is potential dependent. Other factors influencing the electrocrystallization process include deposition time, concentration, and identity of the Co2+(MeCN) counteranion. Mechanistic details have been elucidated by use of cyclic voltammetry, chronoamperometry, electrochemical quartz crystal microbalance, and galvanostatic methods together with spectroscopic and microscopic techniques. The results provide direct evidence that electrocrystallization takes place through two distinctly different, potential-dependent mechanisms, with progressive nucleation and 3-D growth being controlled by the generation of [TCNQ]*- at the electrode and the diffusion of Co2+(MeCN) from the bulk solution. Images obtained by scanning electron microscopy reveal that electrocrystallization of Co[TCNQ]2(H2O)2 at potentials in the range of 0.1-0 V vs Ag/AgCl, corresponding to the [TCNQ]0/*- diffusion-controlled regime, gives rise to arrays of well-separated, needle-shaped nanowires via the overall reaction 2[TCNQ]*-(MeCN)+Co2+(MeCN)+2H2O right harpoon over left harpoon {Co[TCNQ]2(H2O)2}(s). In this potential region, nucleation and growth occur at randomly separated defect sites on the electrode surface. In contrast, at more negative potentials, a compact film of densely packed, uniformly oriented, hexagonal-shaped nanorods is formed. This is achieved at a substantially increased number of nucleation sites created by direct reduction of a thin film of what is proposed to be cobalt-stabilized {(Co2+)([TCNQ2]*-)2} dimeric anion. Despite the potential-dependent morphology of the electrocrystallized Co[TCNQ]2(H2O)2 and the markedly different nucleation-growth mechanisms, IR, Raman, elemental, and thermogravimetric analyses, together with X-ray diffraction, all confirmed the formation of a highly pure and crystalline phase of Co[TCNQ]2(H2O)2 on the electrode surface. Thus, differences in the electrodeposited material are confined to morphology and not to phase or composition differences. This study highlights the importance of the electrocrystallization approach in constructing and precisely controlling the morphology and stoichiometry of Co[TCNQ]2-based materials.
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Affiliation(s)
- Ayman Nafady
- School of Chemistry, Monash University, P.O. Box 23, Victoria 3800, Australia
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O'Mullane AP, Neufeld AK, Harris AR, Bond AM. Electrocrystallization of Phase I, CuTCNQ (TCNQ = 7,7,8,8-Tetracyanoquinodimethane), on indium tin oxide and boron-doped diamond electrodes. Langmuir 2006; 22:10499-505. [PMID: 17129021 DOI: 10.1021/la060408v] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
The electrochemical reduction of TCNQ to TCNQ*- in acetonitrile in the presence of [Cu(MeCN)4]+ has been undertaken at boron-doped diamond (BDD) and indium tin oxide (ITO) electrodes. The nucleation and growth process at BDD is similar to that reported previously at metal electrodes. At an ITO electrode, the electrocrystallization of more strongly adhered, larger, branched, needle-shaped phase I CuTCNQ crystals is detected under potential step conditions and also when the potential is cycled over the potential range of 0.7 to -0.1 V versus Ag/AgCl (3 M KCl). Video imaging can be used at optically transparent ITO electrodes to monitor the growth stage of the very large branched crystals formed during the course of electrochemical experiments. Both in situ video imaging and ex situ X-ray diffraction and scanning electron microscopy (SEM) data are consistent with the nucleation of CuTCNQ taking place at a discrete number of preferred sites on the ITO surface. At BDD electrodes, ex situ optical images show that the preferential growth of CuTCNQ occurs at the more highly conducting boron-rich areas of the electrode, within which there are preferred sites for CuTCNQ formation.
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Affiliation(s)
- Anthony P O'Mullane
- School of Chemistry, Monash University, P.O. Box 23, Victoria, 3800, Australia
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Abstract
The electrochemical properties of porphyrin-appended dendrimers containing 2-, 4-, 8-, 16-, 32- and 64-porphyrin macrocycles in their free-base and zinc(II) forms have been investigated. Both series gave diffusional based voltammetric responses in dichloromethane. There was minimal effect of dendrimer generation on the redox potentials. Multiple pi-cation and anion radicals as well as dications and dianions were formed on the surface of the dendrimers on oxidation or reduction as appropriate, with each cyclic voltammetric wave representing electron transfer to or from multiple non-interacting porphyrin sites. Electrostatic interactions in the higher generation dendrimers result in kinetic effects being observed for the highly charged species generated when each porphyrin unit is doubly or triply oxidised. The number of electrons transferred on reduction or oxidation of the dendrimers was evaluated using steady-state microelectrode voltammetry. For the lower generations of species a good correlation was observed between numbers of electrons transferred and number of porphyrin entities per molecule; for the dendrimers containing 32 and 64 units, however, slight negative deviations were observed, possibly due to electrostatic interactions as the porphyrins become closer packed.
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Affiliation(s)
- Conor F Hogan
- Department of Chemistry, La Trobe University, Bundoora, Victoria, 3086, Australia
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Harris AR, Neufeld AK, O'Mullane AP, Bond AM. Characterisation of two distinctly different processes associated with the electrocrystallization of microcrystals of phase I CuTCNQ (TCNQ = 7,7,8,8-tetracyanoquinodimethane). ACTA ACUST UNITED AC 2006. [DOI: 10.1039/b607290a] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Abstract
In infants, sweet taste and sucking on a pacifier both have analgesic effects. Animal studies suggest that sweet taste may involve opioids, while rhythmic oral movements, as with a pacifier, increase the release of serotonin, which is involved in the gating of nociceptive afferents. The present study was designed to see if these effects produce an analgesic effect in children. Two studies were performed, during blood draws in a pediatric test center in 7- to 12-year-old children, and during vaccination at school in 9- to 11-year-old children. Using unsweetened or sweetened chewing gum, there were four groups: control, sweet, chew, and sweet plus chew. Overall, there was no effect of either sweet taste or chewing on pain responses. However, in boys sweet taste tended to increase pain ratings, but only in conjunction with chewing, while in girls sweet taste tended to decrease pain ratings in conjunction with chewing and increased them in the absence of chewing. Ratings of pain intensity and affective state were correlated. Affective state before the painful stimulus was related to pain response in the girls and in the boys in the test center, but not in the schools. In the schools, the presence of peers may have influenced the ratings.
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Affiliation(s)
- M D Lewkowski
- Department of Psychiatry, McGill University, 1033 Pine Avenue West, Montreal, Quebec, Canada H3A 1A1.
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Kutasi AM, Batten SR, Harris AR, Moubaraki B, Murray KS. Structure and magnetism of the ladder-like coordination polymer Co3(dca)2(nic)4(H2O)8·2H2O [dca = dicyanamide anion, N(CN)2−; nic = nicotinate anion]. CrystEngComm 2002. [DOI: 10.1039/b204645h] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Liu S, Edwards DS, Ziegler MC, Harris AR, Hemingway SJ, Barrett JA. 99mTc-labeling of a hydrazinonicotinamide-conjugated vitronectin receptor antagonist useful for imaging tumors. Bioconjug Chem 2001; 12:624-9. [PMID: 11459468 DOI: 10.1021/bc010012p] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
This report describes the (99m)Tc labeling of a HYNIC-conjugated vitronectin receptor antagonist (SQ168 = [2-[[[5-[carboonyl]-2-pyridinyl]hydrazono]methyl]benzenesulfonic acid]-Glu(cyclo[Lys-Arg-Gly-Asp-D-Phe])-cyclo[Lys-Arg-Gly-Asp-D-Phe]). The ternary ligand complex [(99m)Tc(SQ168)(tricine)(TPPTS)] (RP593) was prepared using a non-SnCl(2)-containing formulation. The corresponding (99)Tc analogue, [(99)Tc]RP593, was also prepared and characterized by HPLC and LC-MS. A HPLC concordance experiment using RP593 and [(99)Tc]RP593 showed that the same technetium complex was prepared at both the tracer and macroscopic levels. The LC-MS data is completely consistent with the 1:1:1:1 composition for Tc:SQ168:tricine:TPPTS and provides direct evidence that the two radiometric peaks in the radio-HPLC chromatogram of RP593 are indeed due to the resolution of diastereomers. In an in vitro receptor binding assay, [(99)Tc]RP593 was shown to have comparable binding affinity for the vitronectin receptor to that of SQ168 itself.
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Affiliation(s)
- S Liu
- Medical Imaging Division, DuPont Pharmaceuticals Company,331 Treble Cove Road, North Billerica, Massachusetts 01862, USA.
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Liu S, Edwards DS, Harris AR, Ziegler MC, Poirier MJ, Ewels BA, Diluzio WR, Hui P. Towards developing a non-SnCl2 formulation for RP444, a new radiopharmaceutical for thrombus imaging. J Pharm Sci 2001; 90:114-23. [PMID: 11169528 DOI: 10.1002/1520-6017(200102)90:2<114::aid-jps2>3.0.co;2-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
There are many factors influencing the yield and radiochemical purity (RCP) of the radiopharmaceutical RP444. These include heating temperature, heating time, pH, the use of a buffering agent and a bulking agent, as well as the component (XV066, tricine, TPPTS, and Na99mTcO4) concentration. Through a series of radiolabeling experiments, we found that a formulation comprised of 20 microg of XV066, 6.5 mg of tricine, 40 mg of mannitol, 5 mg of TPPTS, and 0.1 mg of Pluronic acid dissolved in 1.0 mL of 250 mM succinate buffer (pH 5.0) gives the best RCP for RP444. The formulation can be lyophilized to form a stable crystal "cake". The radiolabeling is achieved by adding 1.5 mL generator eluant (33-133 mCi of Na99mTcO4) to a lyophilized vial and heating the reaction mixture at 100 degrees C for 10 min. Using this formulation, RP444 is prepared consistently in high yield with RCP > or = 90%. Formation of [99mTc]colloid is minimal (< 0.5%).
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Affiliation(s)
- S Liu
- DuPont Pharmaceuticals Company, Medical Imaging Division, 331 Treble Cove Road, North Billerica, Massachusetts 01862, USA.
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Batten SR, Harris AR, Murray KS. Phase change in tetraphenylphosphonium perchlorate. Acta Crystallogr C 2000; 56 Pt 11:1394-5. [PMID: 11077311 DOI: 10.1107/s0108270100011562] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2000] [Accepted: 08/22/2000] [Indexed: 11/10/2022] Open
Abstract
The title compound, C(24)H(20)P(+).ClO(4)(-), undergoes a sudden reversible phase change in the region of 173-180 K which involves ordering of three quarters of the perchlorate anions.
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Affiliation(s)
- S R Batten
- Department of Chemistry, PO Box 23, Monash University 3800, Australia.
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Abstract
Two isolates of binucleate Rhizoctonia spp., previously selected for efficacy in suppression of Rhizoctonia solani and Pythium spp., as well as plant growth promotion, were incorporated into various solid substrate formulations. These formulated products were assayed at three doses in three glass-house experiments for biocontrol of damping-off diseases in Capsicum annuum. R. solani anastomosis group 4 or Pythium ultimum var. sporangiiferum were incorporated into pasteurized potting medium with each formulated binucleate Rhizoctonia product. All formulations were effective against both pathogens in at least two experiments, but some formulations of one isolate of binucleate Rhizoctonia did not give consistent control of R. solani in one experiment. The most consistent formulation, which provided control of both pathogens at all doses of binucleate Rhizoctonia, was the simple substrate of rice hulls. The implications for commercialization of a biocontrol product are discussed.
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Affiliation(s)
- A R Harris
- CSIRO Division of Soils, and Cooperative Research Centre for Soil and Land Management, Glen Osmond, SA, Australia
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Batten SR, Harris AR, Jensen P, Murray KS, Ziebell A. Copper(I) dicyanamide coordination polymers: ladders, sheets, layers, diamond-like networks and unusual interpenetration †. ACTA ACUST UNITED AC 2000. [DOI: 10.1039/b003527k] [Citation(s) in RCA: 132] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Abstract
Eight HYNICtide hydrazones (three with aliphatic substituents and five with aromatic groups) were studied for their potential use as the final intermediate for preparation of RP444, a new radiopharmaceutical under development for imaging thrombosis. The goal of this study is to screen various hydrazones through stability testing and radiolabeling and find those which are able to remain stable without significant degradation in the manufacturing process and at the same time are reactive to produce enough free hydrazine in situ for successful (99m)Tc-labeling. In an initial screening study, only hydrazones 6 and 8, which contain aliphatic substituents, gave satisfactory (>/=90%) yields of RP444 using 50 degrees C and 30 min of heating. However, their solution instability excludes them from being used as commercial reagents. Hydrazones 1 and 4 gave >/=90% yields when the reaction mixtures were heated at 80 degrees C for 30 min. Both hydrazone 1 and hydrazone 4 can be used as the final intermediate for preparation of RP444. The combination of 40 mg of tricine, 1-10 mg of TPPTS, 20-40 microg of hydrazone 1 or 4 for 50 mCi of [(99m)Tc]pertechnetate, 20-50 microg of stannous chloride, pH 4.5 +/- 0.5, and heating at 80 degrees C for 30 min gives the best yield for RP444. It is surprising that hydrazones 1 and 4 have both the solution stability with respect to decomposition and to reaction with aldehydes and ketones and yet are able to hydrolyze in situ to produce enough free HYNICtide for the (99m)Tc-labeling.
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Affiliation(s)
- D S Edwards
- DuPont Pharmaceuticals Company, Medical Imaging Division, 331 Treble Cove Road, North Billerica, Massachusetts 01862, USA
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47
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Abstract
Two isolates of Trichoderma koningii were evaluated for efficacy in control of damping-off diseases in seedlings of Capsicum annuum grown in pasteurized potting medium in a glasshouse. A selected isolate of binucleate Rhizoctonia and two fungicides were also included as standards for control of Rhizoctonia solani and Pythium ultimum var. sporangiiferum. Both isolates of T. koningii reduced seedling death caused by R. solani in one of two experiments, and by P. u. sporangii-ferum in two of three experiments. Neither isolate of T. koningii suppressed damping-off caused by either pathogen as consistently as the binucleate Rhizoctonia or fungicides. The implications of these results for commercial disease management are discussed.
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Affiliation(s)
- A R Harris
- CSIRO Division of Soils, Glen Osmond, Australia.
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48
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Edwards DS, Liu S, Ziegler MC, Harris AR, Crocker AC, Heminway SJ, Barrett JA, Bridger GJ, Abrams MJ, Higgins JD. RP463: a stabilized technetium-99m complex of a hydrazino nicotinamide derivatized chemotactic peptide for infection imaging. Bioconjug Chem 1999; 10:884-91. [PMID: 10502357 DOI: 10.1021/bc990049y] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A HYNIC-conjugated chemotactic peptide (fMLFK-HYNIC) was labeled with (99m)Tc using tricine and TPPTS as coligands. The combination of fMLFK-HYNIC, tricine, and TPPTS with (99m)Tc produced a ternary ligand complex [(99m)Tc(fMLFK-HYNIC)(tricine)(TPPTS)] (RP463). RP463 was synthesized either in two steps, in which the binary ligand complex [(99m)Tc(fMLFK-HYNIC)(tricine)(2)] (RP469) was formed first and then reacted with TPPTS, or in one step by direct reduction of [(99m)Tc]pertechnetate with stannous chloride in the presence of fMLFK-HYNIC, tricine, and TPPTS. The radiolabeling yield for RP463 was usually >/=90% using 10 microg of fMLFK-HYNIC and 100 mCi of [(99m)Tc]pertechnetate. Unlike RP469, which decomposed rapidly in the absence of excess tricine coligand, RP463 was stable in solution for at least 6 h. [(99)Tc]RP463 was prepared and characterized by HPLC and electrospray mass spectrometry. In an in vitro assay, [(99)Tc]RP463 showed an IC(50) of 2 nM against binding of [(3)H]fMLF to receptors on PMNs. [(99)Tc]RP463 also induces effectively the superoxide release of polymorphonuclear leukocytes (PMNs) with an EC(50) value of 0.2 +/- 0.2 nM. The localization of RP463 in the infection foci was assessed in a rabbit infection model. RP463 was cleared from the blood faster than RP469 and was excreted mainly through the renal system. As a result of rapid blood clearance and increased uptake, the target-to-background ratios continuously increased from 1.5 +/- 0.2 at 15 min postinjection to 7.5 +/- 0.4 at 4 h postinjection. Visualization of the infected area could be as early as 2 h. A transient decrease in white blood cell count of 35% was observed during the first 30 min after injection of the HPLC-purified RP463 in the infected rabbit. This suggests that future research in this area should focus on developing highly potent antagonists for chemotactic peptide receptor or other receptors on PMNs and monocytes.
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Affiliation(s)
- D S Edwards
- McNeil Consumers Products, 7050 Camp Hill Road, Fort Washington, Pennsylvania 19034, USA
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49
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Abstract
OBJECTIVE (1) To determine what advice, if any, would be given by accident and emergency (A&E) doctors to women who were taking the combined oral contraceptive pill (OCP) if they had been issued with broad spectrum antibiotics and (2) after an audit programme had been instigated, whether appropriate advice was given to such women. METHODS A questionnaire was circulated to 12 doctors working in the Exeter A&E department to assess their level of knowledge in prescribing antibiotics to women taking the OCP. Notes of women aged 15-50 who had been prescribed broad spectrum antibiotics were examined to see if a contraceptive history had been taken. If the patient was found to be taking the combined OCP it was noted whether documented advice had been given about using an additional form of contraception. Six months later after two education sessions had been held, prescriptions and notes were examined. A patient education leaflet was produced to be given to these women, indicating what additional precautions should be taken after having been prescribed antibiotics. SETTING The A&E department of a busy district general hospital. SUBJECTS Women aged 15-50 who had been issued with broad spectrum antibiotics. RESULTS The level of knowledge in regard to contraceptive advice given to women taking the OCP among doctors working in an A&E department was poor. However, after educational sessions and the production of a patient information leaflet, there was an improvement in women receiving correct advice. CONCLUSIONS The clinical significance of drug interactions between oral contraceptives and antibiotics indicates the importance of asking a full contraceptive drug history of any woman of childbearing age and documenting this in the notes. Regular audit of this topic is needed to keep it at the front of doctors' minds.
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Affiliation(s)
- M H Mullan
- Department of Accident and Emergency Medicine, Royal Devon and Exeter Hospital
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50
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Liu S, Edwards DS, Harris AR. A novel ternary ligand system for 99mTc-labeling of hydrazino nicotinamide-modified biologically active molecules using imine-N-containing heterocycles as coligands. Bioconjug Chem 1998; 9:583-95. [PMID: 9736492 DOI: 10.1021/bc9800116] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
A hydrazinonicotinamide-functionalized cyclic platelet glycoprotein IIb/IIIa (GPIIb/IIIa) receptor antagonist [HYNICtide, cyclo(D-Val-NMeArg-Gly-Asp-Mamb(5-(6-(6-hydrazinonicotina mido)hexanamide)))] was labeled with 99mTc using tricine and a series of imine-N-containing heterocycles as coligands. The imine-N-containing heterocycles include N-omega-Acetylhistamine (HIS-AC), N-(2-hydroxyethyl)isonicotinamide (ISONIC-HE), isonicotinic acid (ISONIC), isonicotinoyl-L-aspartic acid dimethyl ester (ISONIC-L-Asp-OMe2), 4-methyl-5-thiazoleethanol (MTE), nicotinic acid (NIC), 3-nitro-1,2,4-triazole (NTZ), 4-pyridylacetic acid (PA), 4-pyridineethanesulfonic acid (PES), and 3-pyridinesulfonic acid (PSA). The synthesis of these new ternary ligand [99mTc]HYNICtide complexes can be performed in one or two steps in high yield and high specific activity (>/=10 000 Ci/mmol HYNICtide). For example, the reaction of HYNICtide, [99mTc]pertechnetate, nicotinic acid, stannous chloride, and tricine at pH approximately 5 and 100 degreesC for 20 min results in the complex [99mTc(HYNICtide)(tricine)(NIC)] in >/=90% yield as determined by radio-HPLC. It was found that ternary ligand technetium complexes, [99mTc(HYNICtide)(tricine)(L)] (L = ISONIC, ISONIC-L-Asp-OMe2, ISONIC-HE, MTE, PA, PES, and PSA) are formed as equal mixtures of two isomeric forms. Complex [99mTc(HYNICtide)(tricine)(L)] (L = HIS-AC and NTZ) showed more than two well-resolved radiometric peaks at the retention times of interest, suggesting that they may have more than two forms in solution due to different bonding modalities of HIS-AC and NTZ. By a chirality experiment, it was found that the presence of two radiometric peaks is a result of the resolution of the two diastereomers which are formed by the combination of the chiral HYNICtide and the chiral technetium chelate. The formation of two diastereomers was also observed when a chiral imine-N-containing coligand was used for the radiolabeling of HYNIC-BA. The new ternary ligand [99mTc]HYNICtide complexes were found to be stable for up to 6 h in the reaction mixture. The high solution stability is attributed to their kinetic inertness. The composition of these complexes was determined to be 1:1:1:1 for Tc:HYNICtide:L:tricine (L = imine-N-containing heterocycles) through a series of mixed ligand experiments on the tracer (99mTc) level. The lipophilicity of the ternary ligand [99mTc]HYNICtide complexes can be systematically varied by the choice of polyaminocarboxylate and imine-N-containing coligands. Using the combination of tricine and an imine-N-containing coligand, HYNIC-derivatized peptides or other small molecules can be labeled with 99mTc in high specific activity and high stability for potential use as radiopharmaceuticals.
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Affiliation(s)
- S Liu
- The DuPont Merck Pharmaceutical Company, Radiopharmaceuticals Division 331 Treble Cove Road, North Billerica, Massachusetts 01862, USA
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