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Majumdar T, Bazin T, Massahud Carvalho Ribeiro E, Frith JE, Birbilis N. Understanding the effects of PBF process parameter interplay on Ti-6Al-4V surface properties. PLoS One 2019; 14:e0221198. [PMID: 31465449 PMCID: PMC6715245 DOI: 10.1371/journal.pone.0221198] [Citation(s) in RCA: 21] [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] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2018] [Accepted: 08/02/2019] [Indexed: 11/19/2022] Open
Abstract
Ti-6Al-4V is commonly used in orthopaedic implants, and fabrication techniques such as Powder Bed Fusion (PBF) are becoming increasingly popular for the net-shape production of such implants, as PBF allows for complex customisation and minimal material wastage. Present research into PBF fabricated Ti-6Al-4V focuses on new design strategies (e.g. designing pores, struts or lattices) or mechanical property optimisation through process parameter control-however, it is pertinent to examine the effects of altering PBF process parameters on properties relating to bioactivity. Herein, changes in Ti-6Al-4V microstructure, mechanical properties and surface characteristics were examined as a result of varying PBF process parameters, with a view to understanding how to tune Ti-6Al-4V bio-activity during the fabrication stage itself. The interplay between various PBF laser scan speeds and laser powers influenced Ti-6Al-4V hardness, porosity, roughness and corrosion resistance, in a manner not clearly described by the commonly used volumetric energy density (VED) design variable. Key findings indicate that the relationships between PBF process parameters and ultimate Ti-6Al-4V properties are not straightforward as expected, and that wide ranges of porosity (0.03 ± 0.01% to 32.59 ± 2.72%) and corrosion resistance can be achieved through relatively minor changes in process parameters used-indicating volumetric energy density is a poor predictor of PBF Ti-6Al-4V properties. While variations in electrochemical behaviour with respect to the process parameters used in the PBF fabrication of Ti-6Al-4V have previously been reported, this study presents data regarding important surface characteristics over a large process window, reflecting the full capabilities of current PBF machinery.
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Affiliation(s)
- Trina Majumdar
- Department of Materials Science and Engineering, Monash University, Clayton, Victoria, Australia
- Monash Institute of Medical Engineering (MIME), Monash University, Clayton, Victoria, Australia
| | - Tiphaine Bazin
- Department of Materials Science and Engineering, Monash University, Clayton, Victoria, Australia
- Ecole Nationale Supérieure de Chimie de Rennes, Rennes, France
| | - Emily Massahud Carvalho Ribeiro
- Department of Materials Science and Engineering, Monash University, Clayton, Victoria, Australia
- Centro Federal de Educação Tecnológica de Minas Gerais, Belo Horizonte, Brazil
| | - Jessica Ellen Frith
- Department of Materials Science and Engineering, Monash University, Clayton, Victoria, Australia
- Monash Institute of Medical Engineering (MIME), Monash University, Clayton, Victoria, Australia
| | - Nick Birbilis
- Department of Materials Science and Engineering, Monash University, Clayton, Victoria, Australia
- Monash Institute of Medical Engineering (MIME), Monash University, Clayton, Victoria, Australia
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Majumdar T, Cooke ME, Lawless BM, Bellier F, Hughes EAB, Grover LM, Jones SW, Cox SC. Formulation and viscoelasticity of mineralised hydrogels for use in bone-cartilage interfacial reconstruction. J Mech Behav Biomed Mater 2018; 80:33-41. [PMID: 29414473 DOI: 10.1016/j.jmbbm.2018.01.016] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Revised: 01/14/2018] [Accepted: 01/16/2018] [Indexed: 12/14/2022]
Abstract
Articular cartilage is a viscoelastic tissue whose structural integrity is important in maintaining joint health. To restore the functionality of osteoarthritic joints it is vital that regenerative strategies mimic the dynamic loading response of cartilage and bone. Here, a rotating simplex model was employed to optimise the composition of agarose and gellan hydrogel constructs structured with hydroxyapatite (HA) with the aim of obtaining composites mechanically comparable to human cartilage in terms of their ability to dissipate energy. Addition of ceramic particles was found to reinforce both matrices up to a critical concentration (< 3w/v%). Beyond this, larger agglomerates were formed, as evidenced by micro computed tomography data, which acted as stress risers and reduced the ability of composites to dissipate energy demonstrated by a reduction in tan δ values. A maximum compressive modulus of 450.7±24.9 kPa was achieved with a composition of 5.8w/v% agarose and 0.5w/v% HA. Interestingly, when loaded dynamically (1-20Hz) this optimised formulation did not exhibit the highest complex modulus instead a sample with a higher concentration of mineral was identified (5.8w/v% agarose and 25w/v% HA). Thus, demonstrating the importance of examining the mechanical behaviour of biomaterials under conditions representative of physiological environments. While the complex moduli of the optimised gellan (1.0 ± 0.2MPa at 1Hz) and agarose (1.7 ± 0.2MPa at 1Hz) constructs did not match the complex moduli of healthy human cartilage samples (26.3 ± 6.5MPa at 1Hz), similar tan δ values were observed between 1 and 5Hz. This is promising since these frequencies represent the typical heel strike time of the general population. In summary, this study demonstrates the importance of considering more than just the strength of biomaterials since tissues like cartilage play a more complex role.
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Affiliation(s)
- Trina Majumdar
- Materials Science and Engineering Department, Monash University, Australia
| | - Megan E Cooke
- Institute of Inflammation and Ageing, MRC-ARUK Centre for Musculoskeletal Ageing Research, Queen Elizabeth Hospital, University of Birmingham, Birmingham B15 2WB, United Kingdom; School of Chemical Engineering, University of Birmingham, United Kingdom
| | - Bernard M Lawless
- Department of Mechanical Engineering, University of Birmingham, United Kingdom
| | - Francis Bellier
- Materials Engineering, Toulouse National Polytechnic Institute, France
| | - Erik A B Hughes
- School of Chemical Engineering, University of Birmingham, United Kingdom
| | - Liam M Grover
- School of Chemical Engineering, University of Birmingham, United Kingdom
| | - Simon W Jones
- Institute of Inflammation and Ageing, MRC-ARUK Centre for Musculoskeletal Ageing Research, Queen Elizabeth Hospital, University of Birmingham, Birmingham B15 2WB, United Kingdom
| | - Sophie C Cox
- School of Chemical Engineering, University of Birmingham, United Kingdom.
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Wang JL, Liu R, Majumdar T, Mantri S, Ravi V, Banerjee R, Birbilis N. A closer look at the in vitro electrochemical characterisation of titanium alloys for biomedical applications using in-situ methods. Acta Biomater 2017; 54:469-478. [PMID: 28315814 DOI: 10.1016/j.actbio.2017.03.022] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2016] [Revised: 02/08/2017] [Accepted: 03/14/2017] [Indexed: 10/20/2022]
Abstract
Titanium (Ti) and its alloys are widely used in several biomedical applications, particularly as permanent orthopaedic implants. Electrochemical testing provides a means to perform accelerated corrosion testing, however whilst results from polarisation testing for Ti and its alloys to date have been generally useful, they are also rather limited on the basis of several reasons. One reason is that the polarisation curves for Ti and its alloys in simulated body fluids all appear rather similar, and they do not present a classical 'breakdown' or pitting potential, making discrimination between alloys difficult. Of practical relevance however, are two key issues; (1) how do Ti alloys respond to a breakdown event? (i.e. do they readily 'repassivate'?), and, (2) what is that actual rate of Ti ion loss from exposure to physiological conditions? The answers to these questions are probed herein. Several Ti alloys of either unique composition or different fabrication method were studied, including commercially pure Ti (cp-Ti), Ti-6Al-4V, Ti-29Nb-13Ta-4.5Zr (TNTZ), selective laser melted Ti-6Al-4V, direct laser deposited cp-Ti, Ti-35Nb-15Zr, and Ti-25Nb-8Zr. Results reveal that both fabrication method and alloying influence 'repassivation' behaviour. Furthermore, atomic emission spectroelectrochemistry as applied to cp-Ti indicated actual dissolution currents of ∼2-3μA/cm-2 (i.e. ∼9μm/yr) in the range of the corrosion potential, also revealing such dissolution is persistent, even with cathodic polarisation, and definitively revealing that the presence of hydrogen peroxide and albumin activate anodic dissolution of Ti. STATEMENT OF SIGNIFICANCE We believe the paper makes a significant and important contribution to the field of permanent implant biomaterials. Whilst we concede that the paper does not include any in vivo work, the timeliness of the work, and the completely new nature of the findings, we believe carries the impact required for Acta Biomaterialia. Key highlights include:All of the above combine to produce a manuscript that we believe has wide appeal, and can be used as both a port of reference to those working with Ti biomaterials, and also those wishing to apply useful characterisation techniques to their own work (with two very novel methods demonstrated herein, along with the unique information they provide).
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Siddiqui A, Zahiruddin F, Kumar G, Goodarzi A, Yousseff J, Majumdar T, Sinha N, Kaleekal T. Association of Methacholine Challenge Test with Diagnosis of Bronchiolitis Obliterans Syndrome in Lung Transplant Patients. J Heart Lung Transplant 2017. [DOI: 10.1016/j.healun.2017.01.1499] [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: 10/19/2022] Open
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Majumdar T, Bhattacharya S, Barman D, Bhoumik P, Bir R. Detection of multidrug-resistant tuberculosis using MGIT™(TM) and MAS-PCR in Tripura, India. Int J Tuberc Lung Dis 2017; 20:166-9. [PMID: 26792467 DOI: 10.5588/ijtld.14.0986] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Multidrug-resistant tuberculosis (MDR-TB) poses a global threat that is further compounded by the human immunodeficiency virus (HIV) epidemic. OBJECTIVE To detect MDR-TB among pulmonary TB (PTB) patients with or without HIV coinfection by isolating and identifying Mycobacterium tuberculosis from clinical samples and performing drug susceptibility testing (DST). METHODS Sputum was collected from presumed PTB cases. Microscopic examination was performed following Ziehl-Neelsen (ZN) staining and cultured in Löwenstein-Jensen (LJ) medium. First-line anti-tuberculosis DST of the isolates was performed using MGIT™ (Mycobacterial Growth Indicator Tube) and multiplex allele-specific polymerase chain reaction (MAS-PCR). RESULTS Of 172 study subjects, 59.3% (102/172) were smear-positive and 40.7% (70/172) were smear-negative. In the smear-positive and -negative groups, respectively 62.7% (64/102) and 8.6% (6/70) were culture-positive. DST on MGIT showed a cumulative resistance of 7.1% (5/70) to isoniazid (INH) and rifampicin. More ethambutol (EMB) and combined INH+EMB resistance was detected using MAS-PCR. CONCLUSION MDR-TB is a problem in Tripura, and culture and phenotypic DST are required for diagnosis. MAS-PCR may provide an alternative rapid screening tool.
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Affiliation(s)
- T Majumdar
- Department of Microbiology, Agartala Government Medical College, Agartala, India
| | - S Bhattacharya
- Department of Microbiology, Agartala Government Medical College, Agartala, India
| | - D Barman
- Department of Microbiology, Agartala Government Medical College, Agartala, India
| | - P Bhoumik
- Department of Medicine, Agartala Government Medical College, Agartala, India
| | - R Bir
- Department of Microbiology, Agartala Government Medical College, Agartala, India
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Ding Y, Li RW, Nakai M, Majumdar T, Zhang D, Niinomi M, Birbilis N, Smith PN, Chen X. Osteoanabolic Implants: Osteoanabolic Implant Materials for Orthopedic Treatment (Adv. Healthcare Mater. 14/2016). Adv Healthc Mater 2016. [DOI: 10.1002/adhm.201670071] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Yun‐Fei Ding
- Department of Materials Science and Engineering Monash University 20 Research Way Clayton VIC 3800 Australia
| | - Rachel W. Li
- The Medical School The Australian National University Acton ACT 0200 Australia
- The John Curtin School of Medical Research The Australian National University Acton ACT 0200 Australia
| | - Masaaki Nakai
- Department of Biomaterials Science Institute for Materials Research Tohoku University Aoba‐ku Sendai 980‐8577 Japan
| | - Trina Majumdar
- Department of Materials Science and Engineering Monash University 20 Research Way Clayton VIC 3800 Australia
| | - Dong‐Hai Zhang
- The Medical School The Australian National University Acton ACT 0200 Australia
| | - Mitsuo Niinomi
- Department of Biomaterials Science Institute for Materials Research Tohoku University Aoba‐ku Sendai 980‐8577 Japan
| | - Nick Birbilis
- Department of Materials Science and Engineering Monash University 20 Research Way Clayton VIC 3800 Australia
| | - Paul N. Smith
- The Medical School The Australian National University Acton ACT 0200 Australia
- The John Curtin School of Medical Research The Australian National University Acton ACT 0200 Australia
| | - Xiao‐Bo Chen
- Department of Materials Science and Engineering Monash University 20 Research Way Clayton VIC 3800 Australia
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Ding Y, Li RW, Nakai M, Majumdar T, Zhang D, Niinomi M, Birbilis N, Smith PN, Chen X. Osteoanabolic Implant Materials for Orthopedic Treatment. Adv Healthc Mater 2016; 5:1740-52. [PMID: 27113724 DOI: 10.1002/adhm.201600074] [Citation(s) in RCA: 24] [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] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2016] [Revised: 03/15/2016] [Indexed: 01/20/2023]
Abstract
Osteoporosis is becoming more prevalent due to the aging demographics of many populations. Osteoporotic bone is more prone to fracture than normal bone, and current orthopedic implant materials are not ideal for the osteoporotic cases. A newly developed strontium phosphate (SrPO4 ) coating is reported herein, and applied to Ti-29Nb-13Ta-4.6Zr (wt%), TNTZ, an implant material with a comparative Young's modulus to that of natural bone. The SrPO4 coating is anticipated to modulate the activity of osteoblast (OB) and osteoclast (OC) cells, in order to promote bone formation. TNTZ, a material with excellent biocompatibility and high bioinertness is pretreated in a concentrated alkaline solution under hydrothermal conditions, followed by a hydrothermal coating growth process to achieve complete SrPO4 surface coverage with high bonding strength. Owing to the release of Sr ions from the SrPO4 coating and its unique surface topography, OB cells demonstrate increased proliferation and differentiation, while the cellular responses of OC are suppressed, compared to the control case, i.e., bare TNTZ. This TNTZ implant with a near physiologic Young's modulus and a functional SrPO4 coating provides a new direction in the design and manufacture of implantable devices used in the management of orthopedic conditions in osteoporotic individuals.
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Affiliation(s)
- Yun‐Fei Ding
- Department of Materials Science and Engineering Monash University 20 Research Way Clayton VIC 3800 Australia
| | - Rachel W. Li
- The Medical School The Australian National University Acton ACT 0200 Australia
- The John Curtin School of Medical Research The Australian National University Acton ACT 0200 Australia
| | - Masaaki Nakai
- Department of Biomaterials Science Institute for Materials Research Tohoku University Aoba‐ku Sendai 980‐8577 Japan
| | - Trina Majumdar
- Department of Materials Science and Engineering Monash University 20 Research Way Clayton VIC 3800 Australia
| | - Dong‐Hai Zhang
- The Medical School The Australian National University Acton ACT 0200 Australia
| | - Mitsuo Niinomi
- Department of Biomaterials Science Institute for Materials Research Tohoku University Aoba‐ku Sendai 980‐8577 Japan
| | - Nick Birbilis
- Department of Materials Science and Engineering Monash University 20 Research Way Clayton VIC 3800 Australia
| | - Paul N. Smith
- The Medical School The Australian National University Acton ACT 0200 Australia
- The John Curtin School of Medical Research The Australian National University Acton ACT 0200 Australia
| | - Xiao‐Bo Chen
- Department of Materials Science and Engineering Monash University 20 Research Way Clayton VIC 3800 Australia
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Mallick I, Lingampally N, Majumdar T, Achari R, Chatterjee S. EP-1309 IMAGE GUIDANCE FOR ADJUVANT RADIOTHERAPY IN GASTRIC CANCER EXPLORING UNCERTAINTIES AND SOLUTIONS. Radiother Oncol 2012. [DOI: 10.1016/s0167-8140(12)71642-0] [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: 10/28/2022]
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Majumdar T, Bhattacharya S, Barman D, Begum R. Laboratory confirmed outbreak of meningococcal infections in Tripura. Indian J Med Microbiol 2011; 29:74-6. [PMID: 21304204 DOI: 10.4103/0255-0857.76533] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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Majumdar T, Datta S, Ghosh D, Dutta S, Chakraborty A, Goswami R, Mazumder S. Role of virulence plasmid of Aeromonas hydrophila in the pathogenesis of ulcerative disease syndrome in Clarias batrachus. Indian J Biochem Biophys 2007; 44:401-406. [PMID: 18341217] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Pathogenic Aeromonas hydrophila (strain VB21), a multiple-drug resistance strain contains a plasmid of about 21 kb. After curing of plasmid, the isolates became sensitive to antimicrobials, to which they were earlier resistant. The cured bacteria exhibited significant alterations in their surface structure, growth profile and virulence properties, and failed to cause ulcerative disease syndrome (UDS) when injected into the Indian catfish Clarias batrachus. Routine biochemical studies revealed that the plasmid curing did not alter the biochemical properties of the bacteria. After transformation of the plasmid into cured A. hydrophila the bacterium regained its virulence properties and induced all the characteristic symptoms of UDS when injected into fish. Thus, the plasmid plays a pivotal role in the phenotype, growth and virulence of A. hydrophila and pathogenesis of aeromonad UDS.
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Affiliation(s)
- T Majumdar
- Immunobiology Laboratory, School of Life Sciences, Visva-Bharati University, Santiniketan 731 235, India
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Abstract
The menace of cryptococcosis has assumed global proportions over the years. The tropical climate of the Indian subcontinent offers a suitable environment for Cryptococcus neoformans, and the onslaught of the acquired immune deficiency syndrome (AIDS) pandemic since the early 1990s has substantially influenced the situation. Coupled with that are the advances in laboratory diagnostic techniques that have made accurate diagnosis increasingly available. These factors together have led to a sharp increase in the number of reported cases of cryptococcosis. This review attempts to present an overview of the status of cryptococcosis in India from its first description to the most recent times. The disease has been reported from almost all parts of the country. C. neoformans var. neoformans is predominantly found in clinical samples, while C. n. var. gattii infection has also been reported. An organ commonly involved is the central nervous system, among others. Both immunocompromised and apparently immunocompetent patients have been affected. Laboratory diagnosis is mostly by conventional methods, while effective therapeutic options are limited. Early diagnosis followed by institution of specific therapy, where possible, has effectively reduced mortality. Awareness of the disease and maintenance of a high index of clinical suspicion is required. An integrated approach to patient management with active interaction between the clinicians and the laboratory personnel would be highly beneficial. The wide variety of presentations of the disease seen in India suggests the possibility of occurrence of strain variation which needs to be investigated fully. Introduction of routine testing of antifungal susceptibility of clinical isolates is also important in order to obtain baseline data on susceptibility patterns and to predict in advance any shift in those patterns in the population. To maintain a high standard in all such endeavours, the establishment of an external quality control system is desirable.
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Affiliation(s)
- U Banerjee
- Department of Microbiology, All India Institute of Medical Sciences, New Delhi.
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Brignol N, Bakhtiar R, Dou L, Majumdar T, Tse FL. Quantitative analysis of terbinafine (Lamisil) in human and minipig plasma by liquid chromatography tandem mass spectrometry. Rapid Commun Mass Spectrom 2000; 14:141-149. [PMID: 10637419 DOI: 10.1002/(sici)1097-0231(20000215)14:3<141::aid-rcm856>3.0.co;2-i] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
A method using liquid chromatography/tandem mass spectrometry (LC/MS/MS) for the determination of terbinafine in human and minipig plasma has been developed and validated. The method used positive-ion mode for monitoring terbinafine, and used a stable isotope labelled terbinafine as the internal standard. Subsequent to acetonitrile protein precipitation, the supernatant was directly (unfiltered) injected onto the LC column (retention time approximately 4.3 min) for analysis. Interday and intraday accuracy and precision were assessed from the relative recoveries (observed concentration in percent of the nominal value) of spiked samples analyzed on three different days. The lower limit of quantitation (LLOQ) was 0.0679 ng/mL in human and minipig using a plasma sample volume of 0.08 mL. The method was fast, specific, and exhibited ruggedness. Furthermore, the use of turbulent flow chromatography (TurboFlow LC/MS/MS) coupled to mass spectrometry for direct analysis of terbinafine in plasma is discussed. The technique allowed direct introduction of plasma with satisfactory chromatographic peak shape and increased throughput.
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Affiliation(s)
- N Brignol
- Department of Drug Metabolism & Pharmacokinetics, Novartis Institute for Biomedical Research, East Hanover, NJ 07936, USA
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Ramos L, Bakhtiar R, Majumdar T, Hayes M, Tse F. Liquid chromatography/atmospheric pressure chemical ionization tandem mass spectrometry enantiomeric separation of dl-threo-methylphenidate, (Ritalin) using a macrocyclic antibiotic as the chiral selector. Rapid Commun Mass Spectrom 1999; 13:2054-2062. [PMID: 10510420 DOI: 10.1002/(sici)1097-0231(19991030)13:20<2054::aid-rcm749>3.0.co;2-5] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Vancomycin, a macrocyclic antibiotic, is an amphoteric glycopeptide produced by Streptomyces orientalis which has proven to be a viable chiral selector for high performance liquid chromatograph (HPLC) (D. W. Armstrong, Y. Tang, S. Chen, Y. Zhou, C. Bagwill and J-R. Chen, Anal. Chem. (1994; 66: 1473). While it is related to other glycopeptide antibiotics, vancomycin has a number of unique structural features, including 18 stereogenic centers, five aromatic rings, and two side chains one of which is a carbohydrate dimer. Therefore, a vancomycin-based stationary phase appears to be multimodal in that it can be utilized in both normal-phase and reversed-phase liquid chromatography. Consequently, the enantiomeric separation may be operative via several mechanisms, including pi-pi complexation, dipole stacking, inclusion, hydrogen bonding, or combinations of these interactions. LC/MS/MS is a powerful tool for quantitative analysis when evaluated on the basis of speed, specificity, reliability and sensitivity. For these reasons, the present paper explored the feasibility of bonded macrocyclic glycopeptide phases for chiral LC/MS/MS quantitative analysis. Methylphenidate was used as a model compound. A rapid chiral bioanalytical method (<7.5 min) for the determination of the enantiomers of methylphenidate was developed. A lower limit of quantification (LLOQ) of 87 pg/mL was attained for the human plasma assay. This is to our knowledge the first example of enantioselective reversed-phase LC/MS/MS for methylphenidate. The chiral column was relatively cost effective and exhibited excellent performance with no separation deterioration observed after approximately 2500 injections.
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Affiliation(s)
- L Ramos
- Drug Metabolism and Pharmacokinetics Department, Novartis Institute for Biomedical Research, East Hanover, New Jersey 07936, USA
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Abstract
A unique case of disseminated candidosis in premature twins is presented where twin A developed disease soon after birth and died prior to the administration of antifungal therapy. On the other hand, twin B developed infection on the 26th day of birth but survived, though with sequelae (hydrocephalus), since he was promptly and accurately diagnosed and treated.
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Affiliation(s)
- S Sood
- Department of Microbiology, All India Institute of Medical Science, New Delhi, India
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Abstract
The exact projective symmetry manifested in photographs is broken if the object is not flat. It has been found that front view perspectives of the human face, photographed with limited variations in camera angle (within 30 degrees) show a breaking projective symmetry sufficiently small to be considered for accurate comparison. As a practical implementation of this new approach, a computer-controlled video camera superimposition technique has been developed and demonstrated in the identification of a disguised human face.
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Majumdar T, Surolia A. A general method for isolation of galactopyranosyl-specific lectins. Indian J Biochem Biophys 1979; 16:200-3. [PMID: 575352] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Majumdar T, Surolia A. Cross-linked arabinogalactan: a new affinity matrix for the purification of Ricinus communis lectins. Experientia 1978; 34:979-80. [PMID: 700046 DOI: 10.1007/bf01915297] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Arabinogalactan has been cross-linked to give a new high capacity affinity matrix for the purification of Ricinus communis lectins. It shows a capacity which is 50 times greater than that of the conventional affinity matrices.
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Abstract
A simple and rapid method for the purification of Peanut Agglutinin by affinity chromatography on cross-linked arabinogalactan is described. Cross-linked arabinogalactan shows a high capacity for PNA. The lectin has been obtained to electrophoretic purity and has a high hemagglutinating specific activity.
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