Detection method for low molecular weight heparin complete degradation products using hydrophilic interaction chromatography and multiple reaction monitoring tandem mass spectrometry

Information

  • Patent Grant
  • 10416132
  • Patent Number
    10,416,132
  • Date Filed
    Monday, February 27, 2017
    7 years ago
  • Date Issued
    Tuesday, September 17, 2019
    5 years ago
Abstract
A detection method for low molecular weight heparin complete degradation products using hydrophilic interaction chromatography and multiple reaction monitoring tandem mass spectrometry. Identifying the original reducing end and non-reducing end of enoxaparin sodium by means of reducing the reducing end of enoxaparin sodium, and performing hydrolysis using hydrogen peroxide. Performing quantitative analysis on all component units utilizing hydrophilic interaction chromatography and multiple reaction monitoring tandem mass spectrometry, in particular quantifying low-content special structures and characterizing low molecular weight heparin.
Description

This application is the U.S. national phase of International Application No. PCT/CN2017/074966 filed on 27 Feb. 2017 which designated the U.S. and claims priority to Chinese Application No. CN2016103301584 filed on 18 May 2016, the entire contents of each of which are hereby incorporated by reference.


TECHNICAL AREA

This invention involves a novel analytical method for complete degradation products of low molecular weight heparin using hydrophilic interaction chromatography tandem multiple reaction monitoring mass spectrometry, which belongs to the technical areas of pharmaceutical, active pharmaceutical ingredients (API) and the detection technic of API.


BACKGROUND TECHNOLOGY

Heparin and its derivatives, low molecular weight heparins (LMWHs) belong to one category of glycosaminoglycan (GAG). They are important anticoagulant drugs resulting from their anticoagulation functions. In order to reduce the risk of side effects, such as bleeding, osteoporosis, thrombocytopenia, and promote the bioavailability, LMWHs are widely utilized as new anticoagulant instead of heparin. LMWHs are manufactured by either enzymatical or chemical degradations making each kind of LMWH possessing its own special structures. Enoxaparin is a LMWH manufactured via alkaline depolymerization of benzyl ester of heparin. Its major non-reducing ends (NREs) are unsaturated uronic acid residues after chemical modification, while saturated uronic acid and amino sugar residues from the parent heparin are also existed. The major reducing ends (RE) are amino sugars which containing 15-25% of 1,6-anhydro structure, also there are a small amount of uronic acid residues and linkage region at the RE. Dalteparin is a kind of LMWH manufactured via nitrous acid degradation. Its major NREs are saturated uronic acid residues, while major REs is mannitol and a small amount of linkage region. In addition to these special ending structures, the backbone also varies during the manufacturing. All above make the analysis of complete degradation products of LMWHs a big challenge. Usually, there are two strategies for heparin analysis, top-down and bottom-up. Bottom-up analysis is the first choice for degradation product analysis. Heparin products generally enzymatically degraded to complete degradation products, and then are analyzed by capillary electrophoresis, high performance liquid chromatography (HPLC) and HPLC tandem mass spectrometry. These conventional methods were mainly focus on the 8 natural disaccharides and only a part of the special structures, not one can perform a comprehensive identification and quantitation analysis on complete degradation products derived from LMWHs. Take enoxaparin for instance, the original ending structures are not able to identified as the newly generated ending structures of building blocks during enzymatic digestion are identical to the original ones. However, these special structures with extremely low content usually contain important structural information related to the quality and safety of drugs. In other words, the characterization of these building blocks are essential.


In addition to the 8 natural disaccharides, the complete degradation products consist of 3-O-sulfated tetrasaccharides which related to the anticoagulation function, trisaccharides generated by peeling reaction, saturated NREs from parent heparin, N-unsubstituted disaccharides and galacturonic acid disaccharides from chemical modification and C-sulfated disaccharide and epoxide structures from molecular rearrangement. Moreover, there are some characteristic structures for different LMWHs, for example, 1,6-anhydro structures in enoxaparin and its original NRE and RE structures, 2,5-anhydro mannitol. No reported methods are able to cover all these building blocks, nevertheless, the analysis of these ending structures and special structures are indispensable for development of LMWH generic drugs, production control and safety control. Moreover, as some of the original ending structures, like enoxaparin, are identical to that of newly generated ending structures after enzymatical digestion, conventional samples preparation strategies are not capable for comprehensive characterization of enoxaparin.


CONTENTS OF THE INVENTION

Aiming at the shortcomings of current analytical techniques for LMWHs, this invention provides a comprehensive identification and quantitation analysis on complete degradation products derived from LMWHs using hydrophilic interaction chromatography (HILIC) tandem multiple reaction monitoring (MRM) mass spectrometry (MS).


This invention is able to distinguish the original NRE and RE structures of LMWH via performing a reduction reaction of the REs of LMWH and degrading the LMWH using hydrogen peroxide. The quantification of all building blocks is achieved by the separation on a HILIC and detected by a MRM tandem MS, especially for the special structures with extremely low relative contents. This new method is applicable to comprehensive characterization of LMWHs.


TECHNICAL PROTOCOLS OF THIS INVENTION

The procedure of this novel analytical method for complete degradation products of low molecular weight heparin using hydrophilic interaction chromatography tandem multiple reaction monitoring mass spectrometry is as follows:


1. Mobile phase A (MPA) is 3 to 10 mM of ammonium acetate in DI water.


2. Mobile phase B (MPB) is 3 to 10 mM of ammonium acetate in 90 to 98% acetonitrile.


3. For the LMWH that needs to distinguish the original ending structures, 10 to 50 μg LMWH sample with internal standard needs to be reducted with sodium borohydride first and hydrolysis using hydrogen peroxide. The dried hydrolysis product is prepared into solutions with the concentration of 1 to 10 μg/μL and go straight to step 4. For those LMWHs do not need to distinguish the original ending structures, 10 to 50 μg dried heparinase digested LMWH sample with internal standard are prepared into solutions with the concentration of 1 to 10 μg/μL for step 4.


4. Solutions prepared in step 3 are centrifuged prior to separation on HILIC column and detection on MRM tandem MS. The flow rate is 0.1 to 0.5 mL/min, and elution gradient are as follows, 0-5 min, 5% MPA, 95% MPB; 5-107 min, 5-23% MPA, 95-77% MPB; 107-112 min, 23-50% MPA, 77-50% MPB; 112-125 min, 50% MPA, 50% MPB;


5. The MRM tandem MS is performed under positive or negative ionization mode on a triple quadrupole MS. The parameters are set as follows, spry voltage under positive ionization mode is +4.0 kV, spry voltage under negative ionization mode is −3.2 kV, the sheath gas flow is 20-30 arb, tube lens voltage is ±50-150 V, collision energy is 20-50.


According to the present invention, heparinase digested LMWH sample with internal standard is dried under vacuum decompression dry for 1 to 3 hours at 30 to 60° C. in step 3.


According to the present invention, the centrifugation condition in step 4 is 10,000 to 15,000 rpm for 5 to 15 min at room temperature. Then further optimized to be 12,000 rpm for 15 min at room temperature.


BENEFICIAL EFFECT OF THIS INVENTION

This invention is capable to comprehensively identify all basic building blocks, not only including the 8 natural heparin disaccharides, but also all reported structures and some new structures. The usage of internal standard helps to relatively quantify all building blocks identified, successfully settled the drawbacks of conventional method. This invention possesses great practical value in LMWH generic drug development, production control and safety control.





FIGURE LEGENDS


FIG. 1. Extracted ion chromatography of enzymatical digested and chemical degraded enoxaparin reference standard in example 1.



FIG. 2. MS/MS spectra of component 30, 31 of enzymatical digested and RE component 5 of chemical degraded enoxaparin reference standard in example 1. a: MS/MS spectra of component 30 of enzymatical digested enoxaparin reference standard in example 1; b: MS/MS spectra of component 31 of enzymatical digested enoxaparin reference standard in example 1; c: MS/MS spectra of RE component 5 of chemical degraded enoxaparin reference standard in example 1



FIG. 3. Extracted ion chromatography of enzymatical digested dalteparin reference standard in example 2





SPECIFIC IMPLEMENTATION METHOD

Further restrictions will be defined by the figures attached combining with the examples below, but not limited as these.


The examples were performed on an Agilent 1100 series HPLC with a ChemStation workstation online coupling to a Thermo TSQ Quantum Ultra triple quadrupole MS with a Xcalibur workstation.


EXAMPLE 1

The procedure of this novel analytical method for complete degradation products of low molecular weight heparin using hydrophilic interaction chromatography tandem multiple reaction monitoring mass spectrometry is as follows:


1. Mobile phase A (MPA) is 5 mM of ammonium acetate in DI water.


2. Mobile phase B (MPB) is 5 mM of ammonium acetate in 95% acetonitrile.


3. Enoxaparin reference standard was enzymatically digested by heparinase I, II and III at 25° C. for 48 h, and internal standard was added before ultrafiltration using a 30 KDa molecular weight cut off membrane. The digests were vacuum decompression dried. The dried digests is prepared into solutions with the concentration of 10 μg/μL and go to step 5.


4. 50 μg enoxaparin sample with internal standard was reducted with sodium borohydride for 12 h first and hydrolysis using hydrogen peroxide. The dried hydrolysis product is prepared into solutions with the concentration of 10 μg/μL and go to step 5.


5. Solutions prepared in step 3 are centrifuged prior to separation on HILIC column with a particle size of 200 Å (2.0 mm×150 mm) and detection on MRM tandem MS. The flow rate is 0.1 to 0.5 mL/min, and elution gradient are as follows, 0-5 min, 5% MPA, 95% MPB; 5-107 min, 5-23% MPA, 95-77% MPB; 107-112 min, 23-50% MPA, 77-50% MPB; 112-125 min, 50% MPA, 50% MPB;


6. The MRM is performed on a Thermo TSQ Quantum Ultra triple quadrupole MS under negative ionization mode on a triple quadrupole MS. The parameters are set as follows, spry voltage under negative ionization mode is −3.2 kV, the sheath gas flow is 20-30 arb, tube lens voltage is ±75 V, collision energy is 35.


7. The concentration (c) of each component can be calculated according to the formula below, c=cIP×(A/AIP), cIP is the concentration of internal standard, A is the area of internal standard and the AIP is the area of this component.


8. The composition analysis of all identified building blocks were performed, the results for building blocks derived via enzymatic digestion are listed in table 1, the results for building blocks derived via chemical degradation are listed in table 2.
















TABLE 1









Theoretical
Precursor

Daughter



Identity
Structure
WM
ions
Charge
ions






















1
ΔIS
ΔUA2S-GlcNS6S
576.9713
287.5
−2
138


2
ΔIIS
ΔUA-GlcNS6S
497.0145
247.5
−2
138


3
ΔIIIS
ΔUA2S-GlcNS
497.0145
247.5
−2
138


4
ΔIVS
ΔUA-GlcNS
417.0577
416.0
−1
138, 175


5
ΔIA
ΔUA2S-GlcNAc6S
539.0251
268.5
−2
300


6
ΔIIA
ΔUA-GlcNAc6S
459.0683
458.0
−1
157, 175


7
ΔIIIA
ΔUA2S-GlcNAc
459.0683
458.0
−1
157, 175


8
ΔIVA
ΔUA-GlcNAc
379.1115
378.0
−1
115, 175


9
1,6-anhydro
ΔUA-GlcNS-1,6-
399.0471
398.0
−1
175



ΔIIS
anhydro



1,6-anhydro
ΔUA-ManNS-1,6-



ΔIISepi
anhydro


10
1,6-anhydro
ΔUA2-GlcNS-1,6-
479.0040
478.0
−1
398



ΔIS
anhydro


11
1,6-anhydro
ΔUA2S-GlcNS6S-
1055.9753
527.0
−2
  406.5



ΔIS-ISepi
IdoA2S-ManNS-1,6-




anhydro


12
ΔI-H
ΔUA2S-GlcN6S
497.0145
496.0
−1
258, 416


13
ΔII-H
ΔUA2S-GlcN
417.0577
416.0
−1
157, 175


14
ΔIII-H
ΔUA-GlcN6S


15
ΔIV-H
ΔUA-GlcN
337.1009
336.0
−1
115


16
ΔIIA-IISglu
ΔUA-GlcNAc6S-GlcA-
1036.0396
517.0
−2
175, 458, 616




GlcNS3S6S


17
ΔIIS-IISglu
ΔUA-GlcNS6S-GlcA-
1073.9859
536.0
−2
416, 458




GlcNS3S6S


18
NRE dp2 (2S)
IdoA2S-GlcNS
515.0251
256.5
−2
138, 258


19
NRE dp2 (3S)
IdoA2S-GlcNS6S
594.9819
296.5
−2
138


20
Linkage
ΔUA-Gal-Gal-Xyl-O-
719.2120
358.6
−2
218, 337




Ser


21
Linkageox
ΔUA-Gal-Gal-Xyl-O-
690.1855
344.0
−2
189




Serox


22
Δdp3 (2S)
ΔUA-GlcNS6S-HexA
673.0466
335.5
−2
157, 339


23
Δdp3 (2S, 1Ac)
ΔUA-GlcNAc6S-
715.0572
356.0
−2
 97, 157




HexA2S


24
Δdp3 (3S)
ΔUA2S-GlcNS6S-
753.0034
375.5
−2
193, 314




HexA


25
Δdp3 (4S)
ΔUA2S-GlcNS6S-
832.9602
415.5
−2
 97, 157




HexA2S


26
ΔIVSgal
ΔGalA-GlcNS
417.0577
416.0
−1
138, 175


27
ΔIISgal
ΔGalA-GlcNS6S
497.0145
247.5
−2
138


28
Δdp2 (C—S)
ΔUA2CS-GlcNS6S
560.9764
279.5
−2
138


29
Epoxide
ΔUA2S-GlcNS6S-
976.0185
478.0
−2
258




GlcA-2,3-anhydro-GlcNS


30
NRE dp3
GlcNS6S-HexA2S-
915.9643
457.0
−2
240, 258




GlcNS6S


31
Δdp4
ΔUA-GlcNS-
994.0290
496.0
−2
258, 416



(HexA2S3S)
HexA2S3S-GlcNS























TABLE 2









Theoretical
Precursor





Identity
Structure
WM
ions
Charge
Daughter ions
















NREs













1
NRE ΔIS
ΔUA2S-GlcNS6S
576.9713
287.5
−2
138


2
NRE ΔIIS
ΔUA-GlcNS6S
497.0145
247.5
−2
138


3
NRE ΔIIIS
ΔUA2S-GlcNS


−2


4
NRE dp3 (4S)
ΔUA2S-GlcNS6S-
832.9602
415.5
−2
157, 193, 273




HexA2S


5
NRE dp4 (6S)
ΔUA2S-GlcNS6S-
1153.9427
576.0
−2
  415.5




HexA2S-GlcNS6S


6
NRE dp4 (5S)
ΔUA2S-GlcNS6S-
1073.9859
536.0
−2
415.5, 375.5




HexA2S-GlcNS







REs













1
RE dp2 (3S)
HexA2S-GlcNS6S-
596.9976
297.5
−2
242, 260




ol


2
RE dp2 (2S)
HexA-GlcNS6S-ol
517.0407
257.5
−2
242




HexA2S-GlcNS-ol


3
RE dp3 (5S)
GlcNS6S-HexA2S-
917.9800
458.0
−2
242, 260




GlcNS6S-ol


4
RE dp3 (4S)
GlcNS-HexA2S-
838.0232
418.0
−2
260




GlcNS6S-ol


5
RE dp3 (4S,
HexA2S-GlcNS6S-
852.9865
425.5
−2
257



HexA-ol)
HexA2S-ol


6
RE dp3 (3S,
GlcNAc6S-
800.0769
399.0
−2
260



1Ac)
HexA2S-GlclNS-ol





Note:


ΔUA represents unsaturated uronic acid, Hex represents uronic acid, GlcA represents glucuronic acid, IdoA represents iduronic acid, GlcN represents glucosamine, Ac represents acetyl group, S represents sulfo group, -ol represents alditol.






The extracted ion chromatography of building blocks derived via enzymatic digestion are shown in FIG. 1, The extracted ion chromatography of building blocks derived via chemical degradation are shown in FIG. 2. This method successfully identified and quantified all possible complete degradation products in enoxaparin.


EXAMPLE 2

The procedure of this novel analytical method for complete degradation products of low molecular weight heparin using hydrophilic interaction chromatography tandem multiple reaction monitoring mass spectrometry is as follows:


1. Mobile phase A (MPA) is 5 mM of ammonium acetate in DI water.


2. Mobile phase B (MPB) is 5 mM of ammonium acetate in 95% acetonitrile.


3. Dalteparin reference standard was enzymatically digested by heparinase I, II and III at 25° C. for 48 h, and internal standard was added before ultrafiltration using a 30 KDa molecular weight cut off membrane. The digests were vacuum decompression dried.


4. The dried digests is prepared into solutions with the concentration of 10 μg/μL and go to step 5.


5. Solutions prepared in step 3 are centrifuged prior to separation on HILIC column with a particle size of 200 Å (2.0 mm×150 mm) and detection on MRM tandem MS. The flow rate is 0.1 to 0.5 mL/min, and elution gradient are as follows, 0-5 min, 5% MPA, 95% MPB; 5-107 min, 5-23% MPA, 95-77% MPB; 107-112 min, 23-50% MPA, 77-50% MPB; 112-125 min, 50% MPA, 50% MPB;


6. The MRM is performed on a Thermo TSQ Quantum Ultra triple quadrupole MS under negative ionization mode on a triple quadrupole MS. The parameters are set as follows, spry voltage under negative ionization mode is −3.2 kV, the sheath gas flow is 20-30 arb, tube lens voltage is ±75 V, collision energy is 35.


7. The concentration (c) of each component can be calculated according to the formula below, c=cIP×(A/AIP), cIP is the concentration of internal standard, A is the area of internal standard and the AIP is the area of this component.


8. The composition analysis of all identified building blocks were performed, the results for building blocks derived via enzymatic digestion are listed in table 3.
















TABLE 3









Theoretical
Precursor

Daughter



Identity
Structure
WM
ions
Charge
ions






















1
ΔIS
ΔUA2S-GlcNS6S
576.9713
287.5
−2
138


2
ΔIIS
ΔUA-GlcNS6S
497.0145
247.5
−2
138


3
ΔIIIS
ΔUA2S-GlcNS
497.0145
247.5
−2
138


4
ΔIVS
ΔUA-GlcNS
417.0577
416.0
−1
138, 175


5
ΔIA
ΔUA2S-GlcNAc6S
539.0251
268.5
−2
300


6
ΔIIA
ΔUA-GlcNAc6S
459.0683
458.0
−1
157, 175


7
ΔIIIA
ΔUA2S-GlcNAc
459.0683
458.0
−1
157, 175


8
ΔIVA
ΔUA-GlcNAc
379.1115
378.0
−1
115, 175


9
Δdp2 (1S) RE
ΔUA-Mnt6S
402.0468
401
−1
243, 285


10
Δdp2 (2S) RE
ΔUA2S-Mnt6S
482.0036
481
−1
243


11
Δdp4 (3S) RE
ΔUA2S-GlcNS-UA-
899.0613
448.5
−2
243, 255, 339




Mnt6S


12
Δdp4 (4S) RE
ΔUA2S-GlcNS-UA2S-
979.0182
488.5
−2
243, 339




Mnt6S


13
Δdp4 (5S) RE
ΔUA2S-GlcNS6S-
1058.9750
528.5
−2
157, 409




UA2S-Mnt6S


14
ΔI-H
ΔUA2S-GlcN6S
497.0145
496.0
−1
258, 416


15
ΔII-H
ΔUA2S-GlcN
417.0577
416.0
−1
157, 175


16
ΔIII-H
ΔUA-GlcN6S
417.0577
416.0
−1
157, 175


17
ΔIIA-IISglu
ΔUA-GlcNAc6S-GlcA-
1036.0396
517.0
−2
175, 458, 616




GlcNS3S6S


18
ΔIIS-IISglu
ΔUA-GlcNS6S-GlcA-
1073.9859
536.0
−2
416, 458




GlcNS3S6S


19
NRE dp2 (2S)
IdoA2S-GlcNS
515.0251
256.5
−2
138, 258


20
NRE dp2 (3S)
IdoA2S-GlcNS6S
594.9819
296.5
−2
138


21
Linkage
ΔUA-Gal-Gal-Xyl-O-
719.2120
358.6
−2
218, 337




Ser


22
Linkageox
ΔUA-Gal-Gal-Xyl-O-
690.1855
344.0
−2
189




Serox


23
Δdp3 (2S)
ΔUA-GlcNS6S-HexA
673.0466
335.5
−2
157, 339


24
Δdp3 (3S)
ΔUA2S-GlcNS6S-HexA
753.0034
375.5
−2
193, 314


25
Δdp3 (4S)
ΔUA2S-GlcNS6S-
832.9602
415.5
−2
 97, 157




HexA2S


26
ΔIVSgal
ΔGalA-GlcNS
417.0577
416.0
−1
138, 175


27
ΔIISgal
ΔGalA-GlcNS6S
497.0145
247.5
−2
138


28
Δdp2 (C—S)
ΔUA2CS-GlcNS6S
560.9764
279.5
−2
138


29
Epoxide
ΔUA2S-GlcNS6S-
976.0185
478.0
−2
258




GlcA-2,3-anhydro-GlcNS


30
NRE dp3
GlcNS6S-HexA2S-
915.9643
457.0
−2
240, 258




GlcNS6S


31
Δdp4
ΔUA-GlcNS-
994.0290
496.0
−2
258, 416



(HexA2S3S)
HexA2S3S-GlcNS





Note:


ΔUA represents unsaturated uronic acid, Hex represents uronic acid, GlcA represents glucuronic acid, IdoA represents iduronic acid, GlcN represents glucosamine, Ac represents acetyl group, S represents sulfo group, -ol represents alditol.






The extracted ion chromatography of building blocks derived via enzymatic digestion are shown in FIG. 3. This method successfully identified and quantified all possible complete degradation products in dalteparin.

Claims
  • 1. A method for testing completely degraded products from low-molecular-weight heparins using a hydrophilic interaction chromatography combined a multiple reaction monitoring mass spectrometry, comprising: (1) dissolving ammonium acetate in deionized water up to 3 to 10 mM as mobile phase A (MPA);(2) dissolving ammonium acetate in deionized water and adding acetonitrile resulted in mobile phase B (MPB) wherein concentration of ammonium acetate is between 3 and 10 mM and acetonitrile is 90 to 98% by volume;(3) reducing 10 to 50 μg of hydrolyzate products, which contains internal standard, of the low-molecular-weight heparins by sodium borohydride for 10 to 12 hours, and hydrolyzing by hydrogen peroxide, then preparing the degraded products from the low-molecular-weight heparins at the concentration between 1 and 10 μg/μL as a test solution for step (4), if end structures of the low-molecular-weight heparins are desired for further identification;or preparing the hydrolyzate products, which contains the internal standard, at the concentration between 1 and 10 μg/μL as the test solution for step (4) if the end structures of the low-molecular-weight heparins are not desired for further identification;(4) centrifuging the test solution obtained from step (3), loading the supernatant onto a hydrophilic interaction chromatography column for separation: wherein the flow rate is 0.1 to 0.5 mL/min, and elution gradient are as follows: 0-5 min, 5% MPA, 95% MPB; 5-107 min, 5-23% MPA, 95-77% MPB; 107-112 min, 23-50% MPA, 77-50% MPB; 112-125 min, 50% MPA, 50% MPB;(5) the multiple reaction monitoring mass spectrometry is performed under positive or negative ionization mode on a triple quadrupole mass spectrometry: wherein the parameters are set as follows, spry voltage under positive ionization mode is +4.0 kV, spry voltage under negative ionization mode is −3.2 kV, the sheath gas flow is 20-30 arb, tube lens voltage is ±50-150 V, collision energy is 20-50.
  • 2. The method according to claim 1, wherein the hydrolyzate products with the internal standard of the low-molecular-weight heparins in step (3) are dried under vacuum decompression dry for 1 to 3 hours at 30 to 60° C.
  • 3. The method according to claim 1, wherein the centrifugation condition in step (4) is 10,000 to 15,000 rpm for 5 to 15 min at room temperature.
  • 4. The method according to claim 3, wherein the centrifugation condition in step (4) is 12,000 rpm for 15 min at room temperature.
Priority Claims (1)
Number Date Country Kind
2016 1 0330158 May 2016 CN national
PCT Information
Filing Document Filing Date Country Kind
PCT/CN2017/074966 2/27/2017 WO 00
Publishing Document Publishing Date Country Kind
WO2017/197950 11/23/2017 WO A
Non-Patent Literature Citations (1)
Entry
Wang, Zhangjie et al. “Liquid chromatography-diode array detection-mass spectrometry for compositional analysis of low molecular weight heparins” Analytical Biochemistry 451 (2014) 35-41. (Year: 2014).
Related Publications (1)
Number Date Country
20180149626 A1 May 2018 US