Users Online: 444
Home Print this page Email this page
Home About us Editorial board Search Browse articles Submit article Ahead of Print Instructions Subscribe Contacts Login 


 
Previous article Browse articles Next article 
ORIGINAL ARTICLE
Adv Biomed Res 2012,  1:34

Expression, purification, and characterization of a diabody against the most important angiogenesis cell receptor: Vascular endothelial growth factor receptor 2


1 Department of Molecular Medicine, Pasteur Institute of Iran, Tehran, Iran
2 Department of Molecular Medicine, Pasteur Institute of Iran; Department of Anatomical Sciences, Division of Genetics and Molecular Biology, Faculty of Medicine, Isfahan University of Medical Sciences, Iran
3 Department of Animal Breeding and Genetics, Animal Science Research Institute of Iran, Tehran, Iran
4 Department of Virology, Pasteur Institute of Iran, Tehran, Iran

Date of Submission13-Dec-2011
Date of Acceptance18-Feb-2012
Date of Web Publication28-Aug-2012

Correspondence Address:
Hossein Khanahmad
Department of Anatomical Sciences, Division of Genetics and Molecular Biology, Faculty of Medicine, Isfahan University of Medical Sciences, Isfahan
Iran
Login to access the Email id

Source of Support: None, Conflict of Interest: None


DOI: 10.4103/2277-9175.100126

Rights and Permissions
  Abstract 

Antibodies and their derivative fragments have long been used as tools in a variety of applications, in fundamental research work, biotechnology, diagnosis, and therapy. Camels produce single heavy-chain antibodies (VHH) in addition to usual antibodies. These minimal-sized binders are very robust and bind the antigen with high affinity in a monomeric state. Vascular endothelial growth factor recepror-2 (VEGFR2) is an important tumor-associated receptor that blockade of its signaling can lead to the inhibition of neovascularization and tumor metastasis. Here, we describe the construction, expression, and purification VEGFR2-specific Diabody. Two variable fragments of a same camel anti-VEGFR2 antibody were linked together by the upper hinge segment of antibody to make a diabody. We showed the ability of diabody to recognition of VEGFR2 on the cell surface by FACS. Diabodies can be produced in the low-cost prokaryotic expression system, so they are suitable molecules for diagnostic and therapeutic issues.

Keywords: Diabody, Nanobody, vascular endothelial growth factor recepror-2


How to cite this article:
Behdani M, Zeinali S, Karimipour M, Khanahmad H, Asadzadeh N, Azadmanesh K, Seyed N, Baniahmad SF, Anbouhi MH. Expression, purification, and characterization of a diabody against the most important angiogenesis cell receptor: Vascular endothelial growth factor receptor 2. Adv Biomed Res 2012;1:34

How to cite this URL:
Behdani M, Zeinali S, Karimipour M, Khanahmad H, Asadzadeh N, Azadmanesh K, Seyed N, Baniahmad SF, Anbouhi MH. Expression, purification, and characterization of a diabody against the most important angiogenesis cell receptor: Vascular endothelial growth factor receptor 2. Adv Biomed Res [serial online] 2012 [cited 2019 May 27];1:34. Available from: http://www.advbiores.net/text.asp?2012/1/1/34/100126


  Introduction Top


Antibodies and their products have been used as versatile tools in many areas. Their applications in fundamental research work and also in diagnosis and therapy have been reported many times. For instance, utilization of antibodies as drug delivery vehicles, or in cancer therapy as triggers for immune response can be mentioned as some successful achievements. [1] High-yield production, solubility, stability, and small size are critical factors. Regarding this, many attempts to reduce the size of the conventional heterotetrameric IgG molecule (MW; 160 kDa), while retaining its antigen-binding properties, have been conducted. This resulted in a series of antibody fragment constructs, such as Fabs, Fvs, scFvs, dsFvs, and even single-domain VHs, which can be expressed in  Escherichia More Details coli, yeast or myeloma cells. [2]

Camelids generate antibodies that formed by two heavy chains, but no light chains. These immunoglobulins (MW; 95 kDa), referred to heavy-chain antibodies, constitute a major fraction of the functional antibodies in camels (up to 50% in camels). Refined structural changes in the variable domain of the naturally occurring heavy-chain antibodies (named as VHH or Nanobody) compensate for the absence of light chain variable domain. [3],[4]

Vascular endothelial growth factor (VEGF) and its receptors; VEGFR-1, 2, 3, especially VEGFR2, play particularly an important role in angiogenesis under both physiological and pathological conditions. [5],[6] VEGFR2 seems to be the major transducer of VEGF signals in endothelial cells that result in cell proliferation, migration, differentiation, tube formation, increasing vascular permeability, and maintenance of the vessels. [7] Thus, some therapies based on antibody could be one of the possible and also effective therapeutic strategies for inhibition of tumor growth and metastasis by blocking angiogenesis pathways in affected tissues through inhibition of VEGF or its receptor signaling system. [8]

Our research group has previously characterized a high affinity VEGFR2-specific Nanobody, and in vitro studies demonstrated the ability of this Nanobody, termed 3VGR19, to bind VEGFR2 on the cell surface. [9] In this study, we show that the affinity of binding to antigen does not change by constructing the diabody. This study is an introduction to in vivo tests to evaluate the performance of this antibody.


  Materials and Methods Top


Diabody gene construction

The VEGFR2-specific Nanobody gene [9] was amplified from pHEN-4 plasmid, which contains VEGFR2-specific Nanobody (3VGR19) gene by using forward, A6E (5΄-GAT GTG CAG CTG CAG GAG TCT GGR GGA GG-3΄), and reverse 38 (5΄-GGA CTA GTG CGG CCG CTG GAG ACG GTG ACC TGG GT-3΄) primers and subcloned into the pHEN6C vector in PstI and BstEII restriction sites. For diabody construction, the 3VGR19 gene amplified again with BiNb-Sense (5΄-GCC CAG CCG GCC ATG GCC CAG KTG CAG CTA CAG GAG TCN GGN GG-3΄) and BiNb-Llama-IgG2C-hinge (5΄-GCC TGA TTC CTG CAG CTG CAC CTG TGC CAT TGG AGC TTT GGG AGC TTT GGA GCT GGG GTC TTC GCT GTG GTG CGC TGA GGA GAC GGT GAC CTG GGT-3΄) primers. The PCR product was purified and digested with PstI and NcoI and ligated with pHEN6C vector that contains the first Nanobody. [9] Furthermore, the linker sequence of hinge region of Llama IgG2 was added to the respected construct with BiNb-Llama-IgG2C-hinge primer. The resulting plasmid was confirmed by sequencing and named as pHEN6c-3VGR19-Dia.

Expression and purification

The recombinant plasmid pHEN6C-3VGR19-Dia was transformed in competent WK-6 E. coli cells and the cells were plated on Luria-Bertani (LB) agar plates supplemented with 1% glucose and 100 μg/mL ampicillin. After an overnight incubation, fresh colonies inoculated in 5 mL terrific broth (TB) medium with additional 20% glucose and 2 mM MgCl2, then scaled up bacterial culture from 5 mL to 5 L in shaker incubator at 37°C until the OD 600 reached to 0.6 and then induced with 1 mM isopropyl-D-1-thiogalactopyranoside (IPTG). After induction, cells were allowed to grow and express for 12-16 h before harvesting the cell pellet. The cells were harvested by 8 min centrifugation at about 6500×g. After pelleting the cells, the periplasmic proteins were extracted by the osmotic shock. [10] This periplasmic extract was loaded on a His-Select column (Sigma-Aldrich). After washing with PBS, the bonded proteins were eluted with 500 mM imidazole and loaded on Sephadex S75 columns (Pharmacia Biotech) and concentrated on Vivaspin concentrators (Sartorius Stedim Biotech) with a molecular mass cut off of 5 kDa.

SDS-PAGE and western blotting

SDS-PAGE was performed in a 12% (w/v) NuPAGE TM in accordance with the method described by supplier (Invitrogen-USA). The purified protein samples mixed with the same volume of loading buffer were boiled at 100°C for 10 min and subsequently subjected to SDS-PAGE. The gel was stained with Coomassie Brilliant Blue G-250 and destained with the destain solution (2.5% methanol and 10% acetic acid) for 3-5 h. For western blotting, SDS-PAGE separated proteins were blotted onto a nitrocellulose membrane. After blocking with 2% skim milk in PBS, the separated proteins were detected with the anti-His tag mouse antibody (Sigma-Aldrich) and the goat antimouse IgG-HRP conjugate antibody (Sigma-Aldrich) using the color development (18 mg 4-chloro-1-naphtol, 18 μl H2O2, 6 ml methanol and 30 ml PBS) for detecting peroxidase. The purified 3VGR19 Nanobody was used as control. A broad range protein marker (Fermentas) was used as a molecular weight marker.

Flowcytometry analysis

The VEGFR2 expressing cell 293KDR (Sibtech-USA) and the VEGFR2 negative cell HEK293 (Ncbi-Iran) were used for diabody evaluation in FACS. The cell lines were cultured in DMEM medium supplemented with 10% FBS. After washing three times with PBS-BSA 1%, approximately 3×10 5 of cells diluted in a total volume of 100 μL. One microgram of VEGFR2-specific and control diabody (anti-scorpion diabody) was added, and cells incubated for 1 h on ice. Following three times washing with PBS-BSA1%, cells incubated with 1 μg mouse anti-His-tag antibody (Sigma-Aldrich) for 1 h on ice. Detection of bounded nanobodies performed by staining with 0.2 μg rat antimouse antibody PE-conjugated (BD Biosciences). Excess fluorescein-labeled antibody was removed by two times washing with PBS-BSA1% and cells analyzed on a BD FACS Canto II (BD Biosciences).


  Results Top


Expression and purification of VEGFR2-diabody

The VEGFR2-specific Nanobody sequence required for construction of diabody was amplified by PCR from previous characterized pHEN4-3VGR19 plasmid. [9] The fusion gene constructed in the pHEN6c vector, resulting in a three-fragment protein (3VGR19-Linker-3VGR19) as shown in [Figure 1]. The sequence of the construct and surrounding expression region was confirmed by DNA sequencing. The recombinant protein 3VGR19-Dia was expressed as His-tag fusions and purified by affinity chromatography and gel filtration. The gel-filtration profile of diabody showed a longer retention time as compared with the Nanobody [Figure 2]. One liter of the culture typically yielded about 5 mg of purified diabody.
Figure 1: Construction of pHEN6C-3VGR19-Dia bacterial expression plasmid. The pHEN6C-3VGR19 is a plasmid with one copy of VEGFR2- specific Nanobody cloned between the BstEII and PstI sites. A PCR reaction was performed with the BiNb-Sense and BiNb-Llama-IgG2C-hinge primers and subcloned in the pHEN6C-3VGR19 vector, restricted with PstI and NcoI and ligated to each other. The final construct was named pHEN6c-3VGR19-Dia

Click here to view
Figure 2: Size-exclusion chromatography profile of the IMAC-purified VEGFR2-Nanobody and VEGFR2-Diabody (as indicated), loaded onto a superdex S75 column in PBS buffer

Click here to view


SDS-PAGE and western blotting

After gel filtration chromatography, the purity of the protein was more than 95%. The purification was confirmed using SDS-PAGE. The VEGFR2 diabody is present as a single band of about 35 kDa [Figure 3]a. The western blot analysis was done with anti-His tag antibody and revealed that the purified proteins were transferred to the nitrocellulose membrane successfully and migrated at approximately 35 kDa [Figure 3]b.
Figure 3: SDS-PAGE (a) and western-blotting (b) analysis of purified VEGFR2-Diabody (Lane 1) and 3VGR19 Nanobody (Lane 2). The MW of the marker lanes was from top to bottom 160,110, 90, 70, 55, 40, 35, 25, 15 and 10 kDa

Click here to view


Flowcytometry analysis with purified VEGFR2-specific diabody

The ability of VEGFR2 diabody on recognition of receptor on the cell surface analyzed by flowcytometry. FACS analysis was performed with (a) 293KDR cell which is a stably transfected cell line expressing about 2.5×10 6 VEGFR2 per cell [11] and (b) HEK293, VEGFR2 negative cell. [9] Anti-scorpion venom diabody was used as control. In the 293KDR cell line, VEGFR2-diabody showed strong binding signals, as compared with signals obtained with the HEK293 cell line and the control diabody [Figure 4].
Figure 4: Flowcytometry analysis of VEGFR2-specific and control Diabody. a, b show the staining of 293KDR (a) and HEK293 (b) with VEGFR2- specific Diabody. c, d show the staining of 293KDR (c) and HEK293 (d) with control diabody (Anti-scorpion diabody)

Click here to view



  Discussion Top


Antibodies have different potential usages, especially as anticancer agents. However, they need still some improvements in many features to be completely applicable. Stability, affinity, specificity and their size along with pharmacokinetic properties are some of these challengeable and limiting problems. [12] One of the possible solutions for these limits, specifically their size can be solved by reducing the size of the conventional antibody to a Fab or scFv with cloning the corresponding gene fragments and expression in bacteria. [13] However, the unsatisfactory yield of functional, monomeric products in heterologous expression systems remains a barrier in the development of scFv derivatives for therapeutic purposes. [14] Alternatively, single-domain compounds with proper antigen binding specificity can be generated naive libraries of VH antibody fragments or synthetic libraries of various monomeric proteins serve as sources to retrieve antigen-specific molecules; unfortunately the low affinity of these kinds of antibodies is the major problem. [15] The discovery of functional heavy-chain antibodies in camelids generates a new opportunity to obtain soluble antigen-binding fragments of minimal size. These antibodies can be affinity-matured in vivo to yield molecules that interact via one variable domain (Nanobody) with the antigen with adequate affinity and specificity. [16] It shares a large sequence identical to human VH of family 3, but with four amino acid substitutions in framework 2 that render the surface more hydrophilic, thus explaining the soluble behavior and accompanying higher functional expression levels of nanobodies. [17] The beneficial advantage of these recombinant VHH proteins is their stability under different storage conditions. It can be frozen and thawed without significant loss of biological activity indicating their greater stability compared with conventional antigen binders. These significant abilities have also been demonstrated by other scientists. [18],[19] There is a limit in the efficiency of nanobodies because of the short serum half-life due to a rapid renal clearance. The mentioned problem can be eliminated with targeting the VHHs by some serum proteins such as albumin or immunoglobulin. [20],[21],[22] Resulted VHH has a half-life equal the half-life of the serum protein (albumin 2 days in mice and immunoglobulin 9 days). Another well-known alternative in this approach to increase serum half-life of proteins is the genetically addition of proteins together to generate dia, thria, tetrabody.

Previous studies in VEGFR2 antibodies showed these antibodies can inhibit the angiogenesis in vitro and in vivo models. [23],[24],[25] We also in our previous study selected a high affinity VEGFR2-specific Nanobody that was able to inhibit the tube formation. [9] In this study, we describe the successful construction, expression, and characterization of VEGR2-Diabody. The diabody molecule was extracted as soluble proteins from the periplasmic of E. coli in yields that are comparable with those of the monomeric VHHs. We, therefore expect that the high quantities require for treatment and diagnosis will be obtained easily. The recombinant diabody constructs obtained by linking two single-domain fragments can recognize the VEGFR2 on the cell surface of 293KDR cells as same as the VEGFR2-specific Nanobody. [9] Some reports of the construction of diabody have shown that diabody can act like the normal antibody for antigen recognition. [20],[26]

As a conclusion, the easy production steps of Nanobody and diabody constructs based on camel single-domain antibody fragments makes them particularly attractive for use in therapeutic or diagnostic programs.

 
  References Top

1.Chames P, Van Regenmortel M, Weiss E, Baty D. Therapeutic antibodies: Successes, limitations and hopes for the future. Br J Pharmacol 2009;157:220-33.  Back to cited text no. 1
[PUBMED]    
2.Weisser NE, Hall JC. Applications of single-chain variable fragment antibodies in therapeutics and diagnostics. Biotechnol Adv 2009;27:502-20.  Back to cited text no. 2
    
3.Rahbarizadeh F, Ahmadvand D, Sharifzadeh Z. Nanobody; An old concept and new vehicle for immunotargeting. Immunol Invest 2011;40:299-338.  Back to cited text no. 3
[PUBMED]    
4.Muyldermans S, Baral TN, Retamozzo VC, De Baetselier P, De Genst E, Kinne J, et al. Camelid immunoglobulins and Nanobody technology. Vet Immunol Immunopathol 2009;128:178-83.  Back to cited text no. 4
[PUBMED]    
5.Folkman J. Is angiogenesis an organizing principle in biology and medicine? J Pediatr Surg 2007;42:1-11.  Back to cited text no. 5
[PUBMED]    
6.Folkman J. Angiogenesis: An organizing principle for drug discovery? Nat Rev Drug Discov 2007;6:273-86.  Back to cited text no. 6
[PUBMED]    
7.Holmes K, Roberts OL, Thomas AM, Cross MJ. Vascular endothelial growth factor receptor-2: Structure, function, intracellular signalling and therapeutic inhibition. Cell Signal 2007;19:2003-12.  Back to cited text no. 7
[PUBMED]    
8.Ellis LM, Hicklin DJ. VEGF-targeted therapy: Mechanisms of anti-tumour activity. Nat Rev Cancer 2008;8:579-91.  Back to cited text no. 8
[PUBMED]    
9.Behdani M, Zeinali S, Khanahmad H, Karimipour M, Asadzadeh N, Azadmanesh K, et al. Generation and characterization of a functional Nanobody against the vascular endothelial growth factor receptor-2; angiogenesis cell receptor. Mol Immunol 2012;50:35-41.  Back to cited text no. 9
[PUBMED]    
10.Conrath KE, Lauwereys M, Galleni M, Matagne A, Frère JM, Kinne J, et al. Beta-lactamase inhibitors derived from single-domain antibody fragments elicited in the camelidae. Antimicrob Agents Chemother 2001;45:2807-12.  Back to cited text no. 10
    
11.Backer MV, Backer JM. Targeting endothelial cells overexpressing VEGFR-2: Selective toxicity of Shiga-like toxin-VEGF fusion proteins. Bioconjug Chem 2001;12:1066-73.  Back to cited text no. 11
[PUBMED]    
12.Cortez-Retamozo V, Backmann N, Senter PD, Wernery U, De Baetselier P, Muyldermans S, et al. Efficient cancer therapy with a Nanobody-based conjugate. Cancer Res 2004;64:2853-7.  Back to cited text no. 12
[PUBMED]    
13.Skerra A, Pluckthun A. Assembly of a functional immunoglobulin Fv fragment in Escherichia coli. Science 1988;240:1038-41.  Back to cited text no. 13
    
14.Fernandez LA. Prokaryotic expression of antibodies and affibodies. Curr Opin Biotechnol 2004;15:364-73.  Back to cited text no. 14
    
15.Wang X, Campoli M, Ko E, Luo W, Ferrone S. Enhancement of scFv fragment reactivity with target antigens in binding assays following mixing with anti-tag monoclonal antibodies. J Immunol Methods 2004;294:23-35.  Back to cited text no. 15
[PUBMED]    
16.Saerens D, Ghassabeh GH, Muyldermans S. Single-domain antibodies as building blocks for novel therapeutics. Curr Opin Pharmacol 2008;8:600-8.  Back to cited text no. 16
[PUBMED]    
17.Vu KB, Ghahroudi MA, Wyns L, Muyldermans S. Comparison of llama VH sequences from conventional and heavy chain antibodies. Mol Immunol 1997;34:1121-31.  Back to cited text no. 17
[PUBMED]    
18.Bond CJ, Marsters JC, Sidhu SS. Contributions of CDR3 to V H H domain stability and the design of monobody scaffolds for naive antibody libraries. J Mol Biol 2003;332:643-55.  Back to cited text no. 18
[PUBMED]    
19.Dumoulin M, Conrath K, Van Meirhaeghe A, Meersman F, Heremans K, Frenken LG, et al. Single-domain antibody fragments with high conformational stability. Protein Sci 2002;11:500-15.  Back to cited text no. 19
[PUBMED]    
20.Coppieters K, Dreier T, Silence K, de Haard H, Lauwereys M, Casteels P, et al. Formatted anti-tumor necrosis factor alpha VHH proteins derived from camelids show superior potency and targeting to inflamed joints in a murine model of collagen-induced arthritis. Arthritis Rheum 2006;54:1856-66.  Back to cited text no. 20
[PUBMED]    
21.Roovers RC, Laeremans T, Huang L, De Taeye S, Verkleij AJ, Revets H, et al. Efficient inhibition of EGFR signaling and of tumour growth by antagonistic anti-EFGR Nanobodies. Cancer Immunol Immunother 2007;56:303-17.  Back to cited text no. 21
[PUBMED]    
22.Harmsen MM, Van Solt CB, Fijten HP, Van Setten MC. Prolonged in vivo residence times of llama single-domain antibody fragments in pigs by binding to porcine immunoglobulins. Vaccine 2005;23:4926-34.  Back to cited text no. 22
[PUBMED]    
23.Kendrew J, Eberlein C, Hedberg B, McDaid K, Smith NR, Weir HM, et al. An antibody targeted to VEGFR-2 Ig domains 4-7 inhibits VEGFR-2 activation and VEGFR-2-dependent angiogenesis without affecting ligand binding. Mol Cancer Ther 2011;10:770-83.  Back to cited text no. 23
[PUBMED]    
24.Lee SH. Tanibirumab (TTAC-0001): A fully human monoclonal antibody targets vascular endothelial growth factor receptor 2 (VEGFR-2). Arch Pharm Res 2011;34:1223-6.  Back to cited text no. 24
[PUBMED]    
25.Spratlin J. Ramucirumab (IMC-1121B): Monoclonal antibody inhibition of vascular endothelial growth factor receptor-2. Curr Oncol Rep 2011;13:97-102.  Back to cited text no. 25
[PUBMED]    
26.Els Conrath K, Lauwereys M, Wyns L, Muyldermans S. Camel single-domain antibodies as modular building units in bispecific and bivalent antibody constructs. J Biol Chem 2001;276:7346-50.  Back to cited text no. 26
[PUBMED]    


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4]


This article has been cited by
1 Nanobodies as therapeutics: big opportunities for small antibodies
Sophie Steeland,Roosmarijn E. Vandenbroucke,Claude Libert
Drug Discovery Today. 2016;
[Pubmed] | [DOI]
2 Intrabody targeting vascular endothelial growth factor receptor-2 mediates downregulation of surface localization
E Alirahimi,A Ashkiyan,F Kazemi-Lomedasht,K Azadmanesh,M Hosseininejad-chafi,M Habibi-Anbouhi,R Moazami,M Behdani
Cancer Gene Therapy. 2016;
[Pubmed] | [DOI]
3 Development of a recombinant camelid specific diabody against the heminecrolysin fraction of Hemiscorpius lepturus scorpion
Maryam Bagheri,Esmaeil Babaei,Delavar Shahbazzadeh,Mahdi Habibi-Anbouhi,Ehsan Alirahimi,Fatemeh Kazemi-Lomedasht,Mahdi Behdani
Toxin Reviews. 2016; : 1
[Pubmed] | [DOI]
4 A novel method for endothelial cell isolation
QIQI MAO,XIANING HUANG,JIAN HE,WEI LIANG,YI PENG,JING SU,YINGYING HUANG,ZIXI HU,XIAOLING LU,YONGXIANG ZHAO
Oncology Reports. 2016; 35(3): 1652
[Pubmed] | [DOI]
5 Development of a novelin vitroassay for the evaluation of integron DNA integrase activity
Fatemeh Tohidi,Ramazan Rajabnia,Ali Taravati,Mahdi Behdani,Narjes Shokrollahi,Hamid Reza Sadeghnia,Khadijeh Jamialahmadi
Biotechnology & Biotechnological Equipment. 2016; : 1
[Pubmed] | [DOI]
6 Update on implications and mechanisms of angiogenesis in liver fibrosis
Zili Zhang,Feng Zhang,Yin Lu,Shizhong Zheng
Hepatology Research. 2014; : n/a
[Pubmed] | [DOI]
7 Development of a highly-potent anti-angiogenic VEGF8-109heterodimer by directed blocking of its VEGFR-2 binding site
Fahimeh Ghavamipour,S. Shirin Shahangian,Reza H. Sajedi,S. Shahriar Arab,Kamran Mansouri,Mahmoud Reza Aghamaali
FEBS Journal. 2014; : n/a
[Pubmed] | [DOI]



 

Top
Previous article  Next article
 
  Search
 
Similar in PUBMED
   Search Pubmed for
   Search in Google Scholar for
 Related articles
Access Statistics
Email Alert *
Add to My List *
* Registration required (free)

 
  In this article
Abstract
Introduction
Materials and Me...
Results
Discussion
References
Article Figures

 Article Access Statistics
    Viewed3243    
    Printed106    
    Emailed0    
    PDF Downloaded633    
    Comments [Add]    
    Cited by others 7    

Recommend this journal