Facile fabrication of biomimetic chitosan membrane with honeycomb

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Facile fabrication of biomimetic chitosan membrane with honeycomb-like structure for enrichment of glycosylated peptides Luwei Zhang, Shujuan Ma, Yao Chen, Yan Wang, Junjie Ou, Hiroshi Uyama, and Mingliang Ye Anal. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.analchem.8b05215 • Publication Date (Web): 23 Jan 2019 Downloaded from http://pubs.acs.org on January 29, 2019

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Analytical Chemistry

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Analytical Chemistry 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

1

Facile fabrication of biomimetic chitosan membrane with

2

honeycomb-like structure for enrichment of glycosylated peptides

3

Luwei Zhanga,b, Shujuan Maa,b, Yao Chenb, c, Yan Wanga,b, Junjie Oub,*,

4

Hiroshi Uyamaa,d,*, Mingliang Yeb

5

a

6

Education, College of Chemistry and Materials Science, National Demonstration Center for

7

Experimental Chemistry Education, Northwest University, Xi’an, Shaanxi 710127, China

8

b

9

Chemical Physics, Chinese Academy of Sciences, Dalian, 116023, China

Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of Ministry of

CAS Key Laboratory of Separation Science for Analytical Chemistry, Dalian Institute of

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c University

11

d

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565-0871, Japan

of Chinese Academy of Sciences, Beijing, 100049, China

Department of Applied Chemistry, Graduate School of Engineering, Osaka University, Suita

13 14

*

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Prof. Junjie Ou

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Tel: +86-411-84379576

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Fax: +86-411-84379620

18

E-mail: [email protected]

19

Prof. Hiroshi Uyama

20

Tel: +86-29-88302635

21

Fax: +86-29-88302635

22

E-mail: [email protected]

To whom correspondence should be addressed:

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Abstract

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In the study of glycoproteomics with mass spectrometry, certain pretreatments of

29

samples are required for eliminating the interference of non-glycopeptides and

30

improving the efficiency of glycopeptides detection. Although hydrophilic interaction

31

chromatography (HILIC) has been developed for enrichment of glycosylated peptides,

32

a plethora of hydrophilic materials always suffered from large steric hindrance, great

33

cost and difficulty with modifications of high-density hydrophilic groups. In this work,

34

a

35

honeycomb-like accessible macropores was directly prepared by the freeze-casting

36

method as an adsorbent for HILIC. The N-glycopeptides from trypsin digests of

37

immunoglobulin G (IgG), mixture of IgG and bovine serum albumin (BSA), and

38

serum proteins were enriched using this material, and compared with a commercial

39

material ZIC®-HILIC. The biomimetic membrane could identify as many as 32

40

N-glycopeptides from the IgG digest, exhibiting high sensitivity (about 50 fmol), and

41

wide scope for glycopeptide enrichment. A molar ratio of IgG trypsin digest to bovine

42

serum albumin trypsin digest as low as 1/500 verified the outstanding specificity and

43

efficiency for glycopeptide enrichment. In addition, 270 unique N-glycosylation sites

44

of 400 unique glycopeptides from 146 glycosylated proteins were identified from the

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triplicate analysis of 2 μL human serum. Furthermore, 48 unique O-glycosylation

46

sites of 278 unique O-glycopeptides were identified from the triplicate analysis of 30

47

μg deglycosylated fetuin digest. These results indicated that the chitosan-based

48

membrane prepared in this work had great potential for pretreatment of samples in

49

glycoproteomics.

1-mm-thick

biomimetic

honeycomb

chitosan

50 51 52 53 54 55 2


membrane

(BHCM)

with


56

1. Introduction

57

Glycosylation is regarded as one of the most important post-translational

58

modifications (PTMs) among over 300 known protein modifications, and it has been

59

reported that more than 50% of proteins are glycosylated.1-4 Glycosylation of proteins

60

greatly enhances the diversity and complexity of proteins and confers diverse

61

biological functions to proteins, such as protein localization, enzymatic activity and

62

binding specificity.5-7 In particular, abnormal glycosylation is widely considered to be

63

associated with diseases including immunodeficiency, Alzheimer's disease,

64

neurological diseases and cancers.8-11 To date, increasing numbers of glycoproteins

65

have become clinical biomarkers and drug targets. As a result, how to efficiently and

66

highly selectively enrich glycopeptides from complex biological samples has long

67

been an important and urgent topic in the fields of proteomics and pharmacology.

68

There have been many in-depth studies on the glycoproteome based on mass

69

spectrometry (MS) methods.12-14 However, as glycosylated proteins are of low

70

abundance in biological samples and are difficult to be ionized, studies of

71

glycoproteome still encounter great challenges.15-17 In order to solve these problems,

72

the currently widely adopted method is to enzymatically digest glycosylated proteins

73

into peptides, which are then analyzed by MS.18,19 Since the glycosylated peptides are

74

of low abundance (2-5%) in the total peptide mixture, and the signal intensity of

75

glycosylated peptides is generally lower than that of non-glycosylated peptides, the

76

signals of glycosylated peptides are severely suppressed by the signals of

77

non-glycosylated peptides during direct MS analysis. Therefore, high selectivity

78

enrichment of glycosylated peptides is indispensable for research of proteomics.

79

To date, several methods for enrichment of glycosylated peptides have been

80

developed, including lectin affinity chromatography, hydrazine chemistry, boric acid

81

chemistry and hydrophilic interaction chromatography (HILIC).20-23 Lectin affinity

82

chromatography is current one of the most widely used enrichment methods for

83

glycosylated peptides, but suffers from limited scope and high cost. The hydrazine

84

chemistry method is also widely used for enrichment of glycosylated peptides, but has 3


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85

limitations including inability to analyze the glycoforms of enriched glycosylated

86

peptides, lengthy reaction processes, and low selectivity and sensitivity. In the past

87

decade, boric acid-functionized materials have shown great potential. However, due

88

to facile adsorption of non-glycosylated peptides when processing complex biological

89

samples, the selectivity and sensitivity of boric acid-functionized materials should be

90

improved. HILIC has been developed by utilizing the hydrophilicity of glycosylated

91

peptides.24-28 This method is capable of enriching various glycosylated peptides and

92

retaining intact oligosaccharide chain information. A variety of materials based on

93

HILIC have been reported, such as silicon dioxide, magnetic nanoparticles, graphene

94

oxide and metal organic frameworks.29-36 However, these materials suffer from large

95

steric hindrance, great cost and difficulty with modifications of high-density

96

hydrophilic groups.37

97

In consideration of these drawbacks, a biomimetic honeycomb chitosan

98

membrane (BHCM) was synthesized for the first time by a freeze-casting method in

99

this work. Using chitosan as a precursor, the membrane could be simultaneously

100

crosslinked via ring-opening polymerization reaction. The fabrication of BHCM was

101

particularly simple and inexpensive. A large number of amino groups and hydroxyl

102

groups in chitosan provided high-density hydrophilic groups, exhibiting satisfactory

103

enrichment of glycosylated peptides in complex biological samples in MS-based

104

glycoproteomics research.

105 106

2. Experimental

107

2.1 Chemicals and reagents

108

Chitosan was purchased from Shanghai Macklin Biochemical Co. Ltd (Shanghai,

109

China). Poly(ethylene glycol) diglycidyl ether (PEGDGE, Mn=500) was gotten from

110

Aladdin (Shanghai, China). ZIC®-HILIC was purchased from Merck (Darmstadt,

111

Germany). Bovine serum albumin (BSA), human serum immunoglobulin G (IgG),

112

formic acid (FA, 98%), fetuin, trypsin, elastase, iodoacetamide (IAA) and

113

dithiothreitol (DTT, 99%) were bought from Sigma-Aldrich (St Louis, Mo, USA). 4



114

The human serum was obtained from the Second Affiliated Hospital of Dalian

115

Medical University (Dalian, China). These human serum samples were supplied by 10

116

volunteers and pooled together with equal-volume, and the utilization of human serum

117

obeyed with the guideline of Ethics Committee of the Hospital. Hydrochloric acid

118

(HCl) and formaldehyde was acquired from Tianjin Kermel Chemical Reagent Co.

119

Ltd. (Tianjin, China). Ethanol was purchased from Shanghai chemical Plant

120

(Shanghai, China). Acetonitrile (ACN) was purchased from Merck (Darmstadt,

121

Germany). Deionized water was doubly distilled and purified by Milli-Q system

122

(Millipore Inc., Milford, MA, USA). Other chemical reagents were of analytical

123

grade.

124

2.2 Preparation of chitosan-based membrane

125

The preparation process of chitosan-based membrane was shown in Scheme 1.

126

All chitosan membranes were prepared according to the following steps. A certain

127

amount of chitosan was added to 1% acetic acid solution and sonicated for 30 min

128

until a homogeneous solution was obtained. Crosslinking reagent (PEGDGE) was

129

dissolved in water to prepare another aqueous solution with a mass ratio of 1/9. A

130

certain amount of PEGDGE solution was added into the solution of chitosan and

131

sonicated for 15 min. The detailed compositions are listed in Table 1. The resulting

132

solution was centrifuged at 10,000 rpm for 20 min to remove air bubbles, and then

133

carefully transferred to a copper plate as a mold. The bottom of the mold was quickly

134

immersed in liquid nitrogen to allow rapid freezing of the solution. After the solution

135

was completely frozen, the mold was transferred from liquid nitrogen to a vacuum

136

freeze dryer and lyophilized for 24 h to remove the solvent. Then, the mold was

137

placed in an oven at 60 °C for 6 h to allow complete curing chitosan with PEGDGE.

138

The obtained membrane was washed three times with water and ethanol, successively,

139

and then vacuum dried at 60 °C for 12 h prior to use.

5


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140 141

Scheme 1. The preparation processes of chitosan-based biomimetic honeycomb

142

membrane.

143 144

2.3 Instruments and methods

145

The attenuated total reflection-Flourier transformed infrared spectroscopy

146

(ATR-FTIR) was obtained from Thermo Nicolet 380 spectrometer (Nicolet,

147

Wisconsin, USA). The pore structure and morphology of the materials were

148

investigated with scanning electron microscopy (SEM, JEOL JSM-5600, Tokyo,

149

Japan). Thermogravimetric analysis curve was collected on SDT Q600 (TA

150

Instrument Corp., USA). Water contact angle was obtained on a JC2000C machine

151

with 5 μL of water drop (Powereach, Shanghai, China). Elemental analysis was

152

measured on EMIA-8100H (Horiba, Japan).

153

2.4 Denaturation and enzymatic digestion of protein solutions

154

Two milligrams of BSA/IgG /serum proteins/fetuin were dissolved in 1 mL of

155

denaturing solution (8.0 mol·L-1 urea and 0.1 mol·L-1 ammonium bicarbonate)

156

followed by addition of 20 μL DTT (20 mmol·L-1) solution. The mixture was

157

incubated at 60 °C for 1 h. The 7.4 mg of IAA was added, and the mixture was

158

incubated for 30 min in the dark at room temperature. Then, the mixture was diluted 8

159

times with 0.1 mol/L ammonium bicarbonate solution, followed by addition of 80 μg

160

trypsin for BSA/IgG /serum proteins or elastase for fetuin and incubation at 37 °C for

161

16 h. Next, the pH of the mixture was adjusted to 2-3 with 10% TFA aqueous solution.

162

Solid phase extraction (SPE) was performed using a custom C18 column. The eluted

163

peptide solution was dried under vacuum and dissolved in 2.0 mL of 0.1% FA

164

aqueous solution. Finally, the obtained peptide solution was dispensed and dried 6



165

under vacuum, followed by storage in a freezer at -20 °C.

166

2.5 Enrichment of glycopeptides

167

The enrichment of glycopeptides generally includes 3 steps (loading, washing

168

and elution) in HILIC, as illustrated in Scheme 2. One milligram of BHCM was

169

washed with 200 μL of enrichment solution (ACN/H2O/TFA = 83/16/1, v/v/v) for 3

170

times, and then 200 μL of loading solution (ACN/H2O/TFA = 83/16/1, v/v/v)

171

containing 1 μg of IgG tryptic digest was added. The mixture was gently incubated on

172

a platform shaker at room temperature for 30 min. Next, the solution was discarded

173

after centrifugation at 1500 g for 2 min, and then washed for 15 min 3 times with 200

174

μL of washing solution (ACN/H2O/TFA = 83/16/1, v/v/v). Then, the captured

175

glycopeptides were eluted twice with 100 μL of elution solution (ACN/H2O/TFA =

176

30/69/1, v/v/v) for 10 min at room temperature. Finally, the eluted solution was

177

analyzed by MALDI-TOF MS.

178 179

Scheme 2. Schematic processes of enrichment of glycopeptides from the tryptic

180

digest proteins via HILIC.

181 182

In order to enrich the N-glycopeptides from human serum, the above-mentioned

183

lyophilized tryptic digest (120 μg) was dissolved in 500 μL of loading solution

184

(ACN/H2O/TFA=83/16/1, v/v/v), and then 5 mg of BHCM were added to the solution. 7


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185

The mixture was incubated on a platform shaker for 30 min at room temperature.

186

Subsequently, the BHCM was isolated from the mixture by centrifugation at 1500 g

187

for 2 min, and washed with 500 μL washing solution (ACN/H2O/TFA = 83/16/1,

188

v/v/v). Then, the captured glycopeptides were eluted with 3 × 250 μL of elution

189

solution (ACN/H2O/TFA = 30/69/1, v/v/v) for 10 min at room temperature. Finally,

190

the

191

deglycosylated and analyzed by LC-MS/MS.37 The detailed LC-MS experiments were

192

given in Supporting Information (SI).

glycopeptide

solutions

from

three

elutions

were

mixed,

lyophilized,

193

To further investigate the enrichment performance for O-linked glycopeptides,

194

the deglycosylated fetuin digest (30 μg) was dissolved in 200 μL of loading solution

195

(ACN/H2O/TFA=83/16/1, v/v/v). The HILIC enrichment was the same as the

196

above-described procedures.

197 198

3. Results and discussion

199

3.1 Design and Preparation of BHCM

200

Both plants and animals possess analogous tissues containing networks of pores,

201

to deal with mass transport and rates of reactions.38 There were many in-depth studies

202

on preparation and application of biomimetic materials in recent years. Yu et al. made

203

a novel bioinspired polymeric wood by freeze-casting method, which had same

204

structure as honeycomb.39 In addition, Han et al. created a ceramic/polymer

205

composite with honeycomb-like structure through a simple freeze-casting method.40

206

In this case, chitosan was selected as precursor to form a hydrophilic macroporous

207

biomimetic honeycomb membrane with freeze-casting method. In order to prevent

208

chitason from redissolving in HILIC, a little PEGDGE was added into chitosan

209

solution, in which epoxy-amine ring-opening polymerization occurred during the

210

formation of membrane. The influence of chitosan concentration in prepolymerization

211

solution on the formation of membranes was primarily investigated in detail. As

212

shown in Table 1, 4 membranes (BHCMs) were synthesized using various

213

concentrations of chitosan. It could be found that BHCM-1 was extremely flexible

214

when the concentration of chitosan was kept at 1.0 mg mL-1, even if gently touching 8



Page 10 of 25

215

could leave a fingerprint on its surface, and just exhaling to BHCM-1 would cause its

216

serious deformation. Hence, the concentration of chitosan was raised to 10 mg mL-1,

217

and the resulting BHCM-2 showed certain inflexibility. With further increasing of

218

concentration of chitosan from 30 to 50 mg mL-1, it could be found that the resulting

219

materials became more and more hard (BHCM-3 and BHCM-4 as shown in Table 1).

220

These results demonstrated that higher matrix density endowed greater rigidity of

221

BHCM.

222 223

Table 1. Detailed composition for fabrication of BHCM. Membrane

Chitosan concentration (mg mL-1)

PEGDGE/chitosan (w/w)

BHCM-1

1.0

1/10

BHCM-2

10.0

1/10

BHCM-3

30.0

1/10

BHCM-4

50.0

1/10

224 225

3.2 Physical properties of BHCM

226

In order to distinctly observe pore morphology, BHCMs were characterized by

227

SEM. As described in previous report, the morphology of materials prepared with the

228

freeze-casting method could be modified by changing concentrations of the solution.40

229

The SEM images of BHCM-1, BHCM-2, BHCM-3 and BHCM-4, which were

230

fabricated by using different chitosan concentrations at 1.0, 10.0, 30.0 and 50.0 mg

231

mL-1, respectively, are shown in Fig. 1 and Fig. S1 (SI). As shown in Fig. S1A and B,

232

the BHCM-1 exhibited wrinkled skeleton, tunnel structures and pore wall with a

233

thickness of about 200 nm, and its porous structure was irregular. The microstructures

234

of BHCM-2 (Fig. 1A and B) and BHCM-3 (Fig. S1C and D) were still irregular, and

235

the wrinkled skeleton looked like bovine stomach surface, but tunnel structures

236

obviously became narrower. When chitosan concentration was kept at 50 mg mL-1, a

237

honeycomb-like porous structure of BHCM-4 was observed in Fig. 1C. It can be seen

238

that BHCM-4 exhibited highly homogeneous and orderly porous structure with a pore

239

wall thickness of about 100 nm (Fig. 1D). The reason for these results was owing to 9


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240

that the materials of BHCM-1, BHCM-2 and BHCM-3 were too soft, resulting in their

241

structures underwent deformation during the preparation of the samples for SEM.

242

Actually, 4 kinds of BHCMs exhibited honeycomb-like orderly homogeneous tunnel

243

structure, but possessed different rigidity.

244 245

Fig. 1. SEM images of (A, B) BHCM-2 and (C, D) BHCM-4. (A, C) × 400

246

magnification, (B, D) × 10000 magnification.

247 248

Moreover, in order to evaluate the stability of BHCM during the enrichment

249

process. The BHCM-2 was characterized by SEM after being immersed in

250

ACN/H2O/TFA (83/16/1, v/v/v) and ACN/H2O/TFA (30/69/1, v/v/v) for 12 h,

251

respectively. As shown in Fig. S2 (SI), it could be found that there were no obviously

252

differences in structure of the BHCM-2 between before being immersed and after

253

being immersed.

254

Water contact angle was tested to reflect the hydrophilicity of BHCMs. As 10



255

shown in Fig. 2A, the water contact angle of BHCM-2 was 40.6°, and the water

256

contact angles of other three BHCMs were also about 40° (data not shown). This

257

result indicated that the hydrophilicity of these materials was not relevant to chitason

258

concentration, and they could be used for enrichment of glycosylated peptides. The

259

resulting BHCM was subjected to thermogravimetric analysis (TGA) under an air

260

atmosphere from 25 to 800 °C with a heating rate of 10 °C min-1. As shown in Fig. 2B,

261

there was slight weight loss before 100 °C, likely because the BHCM was hydrophilic

262

and easily tended to absorption of moisture even after dried at 60 °C. With the

263

increasing of furnace temperature, no significant weight loss was observed before 260

264

°C. Subsequently, the thermogravimetric curve illustrated notable mass loss of

265

approximate 95% corresponding to the range of 230–580 °C (Fig. 2B). The above

266

result suggested that the BHCM had good thermal stability.

267

In this case, PEGDGE was chosen as a crosslinking reagent and copolymerized

268

with chitosan via epoxy-amine ring-opening polymerization. To research this

269

polymerization, ATR-FTIR was employed to characterize 2 precursors (PEGDGE and

270

chitosan) and BHCM. It could be seen from Fig. 2C that basic characteristic peaks at

271

3354 cm−1 (overlapped stretching vibrations between -OH and -NH groups), 2940 and

272

2870 cm−1 (-CH stretch), 1648 and 1593 cm−1 (amide II band due to C-O and N-H

273

stretching, respectively), 1058 cm-1 (skeletal vibrations involving C-O stretch) existed

274

in both chitosan and BHCM. The signal of epoxy group in PEGDGE was 910 cm−1,

275

while the peak at 910 cm−1 (assigned to epoxy group) disappeared in BHCM. It was

276

suggested that the nucleophilic additional reaction was carried out between the amino

277

group of chitosan and the epoxy group of PEGDGE which produced extra amino and

278

hydroxyl groups.

11


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279 280

Fig. 2. (A) Water contact angle of BHCM-2, (B) thermogravimetric curve of

281

BHCM-2 at a heating rate of 10 oC min-1 with air atmosphere and (C) ATR-FTIR

282

spectra of chitosan, PEGDGE and BHCM-2.

283 284

The chitosan and BHCM-2 were selected for elemental analysis, and the results

285

were shown in Table 2. Comparing with the nitrogen content of chitosan, the nitrogen

286

content of BHCM-2 obviously decreased due to the introduction of crosslinking agent

287

PEGDGE whose molecular formula does not contain nitrogen atom. Moreover, there

288

were no significant differences between theoretical value and measured value of each

289

element in BHCM-2. These results further indicated that the crosslinking agent

290

PEGDGE was successfully copolymerized with chitosan.

291 292 293 294 295 12



296

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Table 2. The results of elemental analysis for chitosan and BHCM-2. Column

N%

C%

H%

O%

Chitosan

7.48

40.18

7.02

43.99

BHCM-2

6.31

40.39

6.97

46.09

297 298

3.3 Applications of BHCM for enrichment of glycosylated peptides

299

Owing to different hydrophilic interaction, the glycopeptides were retained on

300

the surface of BHCM, while the non-glycopeptides were washed off by the elution

301

solution. The tryptic digest of standard protein (IgG) was employed to preliminarily

302

evaluate the enrichment performance of 4 BHCMs at the same experimental

303

conditions (ACN/H2O/TFA, 83/16/1, v/v/v). It could be found that there were no

304

significant differences on enrichment performance among 4 BHCMs (as shown in Fig.

305

S3). Considering that the rigidity of BHCMs was elevated with the increasing

306

concentration of chitosan in prepolymerization solution from 1 to 50 mg mL-1, the

307

BHCM-2 was ultimately chosen to perform the enrichment of glycosylated peptides

308

in the following experiments as a compromised choice.

309

The proportion of organic phase in loading solution is one of the most significant

310

factors for enrichment, which affects the retention behavior of hydrophilic peptides on

311

hydrophilic materials. Therefore, 4 kinds of loading solutions for glycopeptides

312

enrichment were investigated, as shown in Fig. S4 (SI) and Fig. 3B. When

313

ACN/H2O/TFA (87/12/1, v/v/v) was selected as the loading solution, a large amount

314

of non-glycopeptides with high signal intensity were observed in Fig. S4A. When

315

ACN/H2O/TFA (85/14/1, v/v/v) was chosen as the loading solution, the signals of

316

non-glycopeptides were still obviously observed in Fig. S4B, but the signal intensity

317

reduced, comparing with Fig. S4A. Using ACN/H2O/TFA (83/16/1, v/v/v) as the

318

loading solution, the signal intensity of glycopeptides was relatively stronger than that

319

of non-glycopeptides (Fig. 3B), indicating that the non-glycopeptides were efficiently

320

removed, and the glycosylated peptides were well retained. However, the signals of

321

glycopeptides were significantly weakened in Fig. S4C and only 12 glycopeptides 13


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322

(shown in Table. S1) were detectable when the loading solution was set at

323

ACN/H2O/TFA (81/18/1, v/v/v). After comprehensive consideration, the content of

324

ACN was eventually set at 83% as loading solution in the subsequent enrichment of

325

glycosylated peptides experiments.

14



326 327

Fig. 3. MALDI-TOF mass spectra of tryptic digest of IgG. (A) Direct analysis,

328

analysis after enrichment with (B) BHCM-2, (C) ZIC®-HILIC and (D) analysis of the

329

deglycosylated peptides enriched by BHCM-2 with 83% ACN + 1% TFA as loading 15


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330

solution and 30% ACN + 1% TFA as elution solution. Glycopeptide peaks identified

331

are marked with the symbol “*”.

332 333

The concentration of TFA in loading solution also had effect on the retention

334

behavior of hydrophilic peptides in HILIC. To further optimize enrichment conditions,

335

the ability of enrichment of glycosylated peptides with BHCM-2 was investigated

336

using different contents of TFA (0.1%, 1% and 5%, w/v). When the concentration of

337

TFA in both loading and elution solutions were kept at 0.1%, the signals of

338

non-glycosylated peptides emerged weakly in Fig. S5A (SI), indicating that the

339

enrichment of glycosylated peptides was unsatisfactory in this condition.

340

Subsequently, 1% and 5% TFA in both loading and elution solution were utilized in

341

enrichment of glycosylated peptides, and the results (shown in Fig. 3B and S5B) were

342

desirable. Considering solubility of chitosan in acid, ACN/H2O/TFA (83/16/1, v/v/v)

343

and ACN/H2O/TFA (30/69/1, v/v/v) were finally determined as loading and elution

344

solution in the subsequent experiments, respectively.

345

The addition of TFA to loading solution and elution solution has been widely

346

used to increase the difference in hydrophilicity between glycopeptides and

347

non-glycosylated peptides via ion pairing. As previously described, TFA in elution

348

solution could be displaced by NH4HCO3.41 Based on above-mentioned work, the

349

influence of 2 kinds of ion pairings (TFA and NH4HCO3) were investigated for

350

enrichment of glycosylated peptides using BHCM-2. There were no obviously

351

differences on enrichment performance (as shown in Fig. 3B and Fig. S6 (SI)) when

352

loading solution was ACN/H2O/TFA (83/16/1, v/v/v), and elution solution was

353

ACN/H2O/NH4HCO3 (30/69/1, v/v/v). However, there was strong suppression of the

354

MS signals of glycopeptides in the presence of NH4HCO3. Therefore, TFA was

355

chosen as ion pairing in elution solution for enriching glycosylated peptides.

356

As shown in Fig. 3A, 8 glycosylated peptides were directly detected in the

357

unenriched tryptic digest of IgG, because the signals of highly abundant

358

non-glycopeptides suppressed the signals of glycopeptides. After enrichment by the

359

BHCM-2, 32 glycopeptides could be detected, while the interference from 16



360

non-glycopeptides was almost completely eliminated (Fig. 3B and Table S2). In

361

comparison, only 22 glycopeptides were detectable when the glycopeptides were

362

captured from tryptic digest of IgG using a commercial ZIC®-HILIC material (Fig. 3C

363

and Table S3). It could be found that the BHCM-2 exhibited higher enrichment

364

efficiency for glycopeptides than commercial material. All glycopeptides, which were

365

enriched by BHCM-2, were further deglycosylated with PNGase F and analyzed by

366

MALDI. Four deglycosylated peptides were detected in Fig. 3D, further confirming

367

that these peptides were all glycosylated. These results illustrated that the BHCM-2

368

had excellent performance for enrichment of glycopeptides.

369

In addition, the adsorption capacity of BHCM-2 for glycopeptides was

370

investigated. Different amount of BHCM-2 were respectively incubated with an

371

identical amount of the tryptic digest of IgG (25 μg). When using 2 mg BHCM-2,

372

signal intensities of the 6 selected glycopeptides reached maximum after enrichment

373

(Fig. 4). The capacity of BHCM-2 for glycopeptides was calculated as 12.5 μg mg-1. 3500

m/z=2602 m/z=2634 m/z=2764 m/z=2796 m/z=2926 m/z=2958

3000 2500

Intensity

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 18 of 25

2000 1500 1000 500 0

0.5

1

2 3 Amount(mg)

4

5

374 375

Fig. 4. The signal intensities of 6 selected glycopeptides from 25 μg of IgG digests

376

after enrichment by different amounts of BHCM-2.

377 378

In consideration of the low abundance of glycoproteins in biological samples, the

379

sensitivity of detection was also assessed for enrichment of glycopeptides using 17


Page 19 of 25 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


380

BHCM-2 in this work, as shown in Fig. S7 (SI). Six glycopeptides could be detected

381

in 500 fmol of the tryptic digest of IgG (Fig. S7A). When the amount of tryptic digest

382

of IgG was 50 fmol, 5 glycopeptides were still detectable (Fig. S7B). As a comparison,

383

the commercial ZIC®-HILIC material was also used to enrich glycopeptides under the

384

same conditions. Unfortunately, only 5 and 1 glycopeptides could be detected with

385

commercial ZIC®-HILIC material under the same conditions (Fig. S7C and D). It

386

could be further demonstrated that the BHCM-2 exhibited high sensitivity for

387

enrichment of glycopeptides.

388

In order to evaluate the selectivity of BHCM-2 in enrichment of glycopeptides, a

389

mixture of tryptic digests of IgG and BSA was incubated with BHCM-2 for

390

enrichment. As shown in Fig. S8A and Table S4, 21 glycopeptides could be detected

391

when the molar ratio of tryptic digests of IgG and BSA was kept as 1/100 after

392

enrichment by the BHCM-2. Furthermore, when the molar ratio was 1/200, 17

393

glycopeptides were still detectable (Fig. S8B and Table S5). Even when the molar

394

ratio of tryptic digests of IgG and BSA decreased to 1/500, 14 glycopeptides

395

continued to be observed with high signal intensity (Fig. S8C and Table S6). For

396

comparison, the commercial ZIC®-HILIC material was also employed to capture

397

glycopeptides under the same conditions. When the molar ratios were 1/100 (Fig. S8D

398

and Table S7) and 1/200 (Fig. S8E and Table S8), 11 glycopeptides and 7

399

glycopeptides were detectable, respectively. Moreover, when the molar ratio was kept

400

as 1/500, only 4 glycopeptides could be observed (Fig. S8F and Table S9). The results

401

of interference experiments demonstrated that the BHCM-2 had higher selectivity in

402

enrichment of glycopeptides than the commercial ZIC®-HILIC material.

403

Moreover, in order to achieve an accurate quantitative result, through using the

404

stable isotope dimethyl labeling technique according to the literature,42,43 the parallel

405

reaction monitoring (PRM) mass spectrometry method was utilized to quantify the

406

recovery of glycopeptide enrichment by BHCM-2. As shown in Table 3, the recovery

407

of glycopeptide enrichment was 93.2% ± 7%. The results indicated that BHCM had

408

outstanding recovery for the selective enrichment of glycopeptides. Meanwhile, the

409

above results were superior to those previously reported with GO-PEI-Au-L-Cys 18



Page 20 of 25

410

(79.4%)44, cysteine-functionalized MOFs (80%)45 and CS@PGMA@IDA−Ti4+

411

(75.4%)46.

412 413

Table 3. Enrichment recoveries of N-linked glycopeptides from an IgG tryptic digest

414

(9 μg) using BHCM-2 by LC-PRM mass spectrometry. Amino acid sequence(m/z)

Recover ± S.D(%,n=3)

EEQFN#STFR(1158.5)

93.4 ± 4.2

EEQYN#STYR(1190.5)

93.3 ± 1.3

Average ± S.D 93.3% ± 3.1%

415 416

In order to further investigate application of the BHCM, human serum was

417

selected as an actual biological sample to evaluate the ability of BHCM. According to

418

the above procedures to deal with serum samples and deglycosylation with PNGaseF,

419

the resulting products were analyzed by LC-MS/MS. Through performing three

420

paralleled enrichment experiments with BHCM-2 and the database search for

421

experimental results, 270 unique N-glycosylation sites of 400 unique N-glycopeptides

422

from 146 N-glycosylated proteins were identified when 2 μL serum sample were used

423

(as shown in Table S10 (SI) and Fig. 5). A chitosan-based microsphere (CSMS) was

424

recently reported by Feng et al.,47 which exhibited high selectivity (HRP/BSA=1/100)

425

and good sensitivity (45 fmol of HRP) in glycopeptides enrichment, and identified

426

194 unique N-glycosylation sites from 2 μL of human serum. In our work, the BHCM

427

showed higher selectivity (IgG/BSA=1/500) and similar sensitivity (50 fmol) in

428

glycopeptides enrichment, and could identify two-fold unique N-glycosylation sites as

429

many as the CSMS. Compared with the CSMS, BHCM was synthesized with a simple

430

and convenient method and exhibited better application effect through a bionic

431

strategy. These results demonstrated that the material BHCM-2 possessed excellent

432

selectivity and efficiency in enrichment of glycopeptides, and could be widely applied

433

to analysis of complex biological samples.

19


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434 435

Fig. 5. (A) Separation chromatogram of tryptic digest of serum after enrichment by

436

BHCM-2 on C18 column by LC-MS/MS and Venn diagrams of (B) N-glycopeptides,

437

(C) N-glycosylation sites and (D) N-glycoproteins after enriched by BHCM-2.

438 439

Furthermore, O-linked glycopeptides was another major glycosylation on protein.

440

However, compared with N-glycopeptides, O-glycopeptides had lower hydrophilicity,

441

which made it hard to be enriched by HILIC and analyzed by MALDI-TOF MS. As a

442

result, the enrichment performance for O-linked glycopeptides was never considered

443

in most of previously reports. In this work, 48 unique O-glycosylation sites of 278

444

unique O-glycopeptides were identified when 30 μg deglycosylated fetuin digest were

445

used (as shown in Table S11, Table S12 and Fig. S9). These results further indicated

446

that BHCM-2 had extensive applicability to different types of glycopeptides.

447 448

Conclusions

449

In this study, a novel membrane material with accessible macropores has been

450

facilely prepared using chitosan and PEGDGE as precursors via freeze-casting

451

method. Its preparation process was very simple, and starting materials were

452

inexpensive. The resulting material BHCM possessed good biocompatibility, decent 20



453

hydrophilicity, good specificity, high sensitivity of detection and outstanding recovery.

454

The honeycomb-like structure could effectively cut down the existence of steric

455

hindrance between the material and glycopeptides. Moreover, the material BHCM

456

possessed extensive applicability and high selectivity in different types of

457

glycopeptides, which exhibited great potential of the BHCM in enrichment of

458

glycopeptides from complex biological samples. Compared with other HILIC

459

materials, BHCM features low cost, simple preparation process, as well as excellent

460

enrichment capability for glycopeptides.

461 462

Supporting Information

463

Fig. S1, SEM images of BHCM-1 and BHCM-3; Fig. S2, SEM images of BHCM-2 after being

464

immersed in loading solution and elution solution; Fig. S3, MALDI spectra of N-glycopeptides

465

from IgG tryptic digest after enrichment by 4 different BHCMs; Fig. S4, MALDI spectra of

466

N-glycopeptides from IgG digest after enrichment by BHCM-2 with different ACN content in

467

loading solution; Fig. S5, MALDI spectra of N-glycopeptides enriched from IgG digest with

468

different TFA content; Fig. S6, MALDI spectra of N-glycopeptides enriched from IgG digest

469

using BHCM-2 with 30% ACN + 1% NH4HCO3 as elution solution; Fig. S7, MALDI spectra of

470

500 and 50 fmol of IgG tryptic digest after enrichment by BHCM-2 and ZIC®-HILIC; Fig. S8,

471

MALDI spectra of N-glycopeptides from IgG and BSA tryptic digest with different molar ratios

472

after enrichment by BHCM-2 and ZIC®-HILIC; Fig. S9, Venn diagrams of O-glycopeptides and

473

O-glycosylation sites identified from fetuin digest after enrichment by BHCM-2; Table S1,

474

identified N-glycopeptides in IgG by BHCM-2 with 81% ACN + 1% TFA as loading solution;

475

Table S2, identified N-glycopeptides in IgG by BHCM-2; Table S3, identified N-glycopeptides in

476

IgG by ZIC®-HILIC; Table S4-S6, identified N-glycopeptides in IgG and BSA with different

477

molar ratio by BHCM-2; Table S7-S9, identified N-glycopeptides in IgG and BSA with different

478

molar ratio by ZIC®-HILIC; Table S10, identified N-glycopeptidesin human serum by BHCM-2;

479

Table S11, identified O-glycopeptides in fetuin by BHCM-2; Table S12, identified

480

O-glycosylation sites in fetuin by BHCM-2

481 482 21


Page 22 of 25

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483


Acknowledgements

484

Financial support is gratefully acknowledged from the China State Key Basic

485

Research Program Grant (2016YFA0501402) and the National Science Fund for

486

Distinguished Young Scholars (21525524), as well as the National Natural Sciences

487

Foundation of China (No. 21575141, 21675125 and 21606181) and CAS-Weigao

488

Research & Development Program ([2017]-009). And we are very grateful for the

489

financial support from the Amygdalus pedunculata Engineering Technology Research

490

Center of the State Forestry Administration and Key Laboratory of Yulin Desert Plant

491

Resources.

492 493

References

494

(1) An, H. J.; Froehlich, J. W.; Lebrilla, C. B. Curr. Opin. Chem. Biol. 2009, 13, 421-426.

495

(2) Jia, X. G.; Demchenko, A. V. Beilstein J. Org. Chem. 2017, 13, 2028-2048.

496

(3) Song, E.; Mechref, Y. Biomarkers Med. 2015, 9, 835-844.

497

(4) Palaniappan, K. K.; Bertozzi, C. R. Chem. Rev. 2016, 116, 14277-14306.

498

(5) Cummings, R. D.; Pierce, J. M. Chem. Biol. 2014, 21, 1-15.

499

(6) Hart, G. W.; Copeland, R. J. Cell 2010, 143, 672-676.

500

(7) Russo, L.; Cipolla, L. Chem.-Eur. J. 2016, 22, 13380-13388.

501

(8) Hakomori, S. Cancer Res. 1985, 45, 2405-2414.

502

(9) Freeze, H. H. J. Biol. Chem. 2013, 288, 6936-6945.

503

(10) Reis, C. A.; Osorio, H.; Silva, L.; Gomes, C.; David, L. J. Clin. Pathol. 2010, 63, 322-329.

504

(11) Pinho, S. S.; Reis, C. A. Nat. Rev. Cancer 2015, 15, 540-555.

505

(12) Pan, S.; Chen, R.; Aebersold, R.; Brentnall, T. A. Mol. Cell. Proteomics 2011, 10, R110.003251.

506

(13) Sun, B.; Ranish, J.; Utleg, A. G.; White, J. T.; Yan, X. W.; Lin, B. Y.; Hood, L. Mol. Cell.

507

Proteomics 2007, 6, 141-149.

508

(14) Morris, H. R.; Thompson, M. R.; Osuga, D. T.; Ahmed, A. I.; Chan, S. M.; Vandenheede, J. R.;

509

Feeney, R. E. J. Biol. Chem. 1978, 253, 5155-5162.

510

(15) Kolli, V.; Schumacher, K. N.; Dodds, E. D. Bioanalysis 2015, 7, 113-131.

511

(16) Olsen, J. V.; Mann, M. Mol. Cell. Proteomics 2013, 12, 3444-3452.

512

(17) Dell, A.; Morris, H. R. Science 2001, 291, 2351-2356.

513

(18) Novotny, M. V.; Alley, W. R., Jr. Curr. Opin. Chem. Biol. 2013, 17, 832-840.

514

(19) Domon, B.; Aebersold, R. Science 2006, 312, 212-217.

515

(20) Zhang, H.; Li, X. J.; Martin, D. B.; Aebersold, R. Nat. Biotechnol. 2003, 21, 660-666.

516

(21) Mysling, S.; Palmisano, G.; Hojrup, P.; Thaysen-Andersen, M. Anal. Chem. 2010, 82, 5598-5609.

517

(22) Mechref, Y.; Madera, M.; Novotny, M. V. Methods Mol. Biol. 2008, 424, 373-396.

518

(23) Wuhrer, M.; Catalina, M. I.; Deelder, A. M.; Hokke, C. H. J. Chromatogr. B 2007, 849, 115-128.

519

(24) Zhang, Y.; Jing, H.; Wen, T.; Wang, Y.; Zhao, Y.; Wang, X.; Qian, X.; Ying, W. Talanta 2019,

520

191, 509-518.

521

(25) Takegawa, Y.; Deguchi, K.; Keira, T.; Ito, H.; Nakagawa, H.; Nishimura, S. J. Chromatogr. A 22



522

2006, 1113, 177-181.

523

(26) Wuhrer, M.; Koeleman, C. A. M.; Hokke, C. H.; Deelder, A. M. Anal. Chem. 2005, 77, 886-894.

524

(27) Wuhrer, M.; de Boer, A. R.; Deelder, A. M. Mass Spectrom. Rev. 2009, 28, 192-206.

525

(28) Hagglund, P.; Bunkenborg, J.; Elortza, F.; Jensen, O. N.; Roepstorff, P. J. Proteome Res. 2004, 3,

526

556-566.

527

(29) Li, Y.; Wang, J.; Sun, N.; Deng, C. H. Anal. Chem. 2017, 89, 11151-11158.

528

(30) Yan, J.; Li, X.; Yu, L.; Jin, Y.; Zhang, X.; Xue, X.; Ke, Y.; Liang, X. Chem. Commun. 2010, 46,

529

5488-5490.

530

(31) Sun, N.; Wang, J.; Yao, J.; Deng, C. Anal. Chem. 2017, 89, 1764-1771.

531

(32) Li, J.; Wang, F.; Wan, H.; Liu, J.; Liu, Z.; Cheng, K.; Zou, H. J. Chromatogr. A 2015, 1425,

532

213-220.

533

(33) Ma, R.; Hu, J.; Cai, Z.; Ju, H. Nanoscale 2014, 6, 3150-3156.

534

(34) Bibi, A.; Ju, H. Talanta 2016, 161, 681-685.

535

(35) Wang, J.; Li, J.; Gao, M.; Zhang, X. Nanoscale 2017, 9, 10750-10756.

536

(36) Wang, Z.; Wu, R.; Chen, H.; Sun, N.; Deng, C. Nanoscale 2018, 10, 5335-5341.

537

(37) Xia, C.; Jiao, F.; Gao, F.; Wang, H.; Lv, Y.; Shen, Y.; Zhang, Y.; Qian, X. Anal. Chem. 2018, 90,

538

6651-6659.

539

(38) Zheng, X.; Shen, G.; Wang, C.; Li, Y.; Dunphy, D.; Hasan, T.; Brinker, C. J.; Su, B. L. Nat.

540

Commun. 2017, 8, ncomms14921.

541

(39) Yu, Z.-L.; Yang, N.; Zhou, L.-C. Sci. Adv. 2018, 4, sciadv.aat7223.

542

(40) Zhao, H.; Yue, Y.; Guo, L.; Wu, J.; Zhang, Y.; Li, X.; Mao, S.; Han, X. Adv. Mater. 2016, 28,

543

5099-5105.

544

(41) Dong, X.; Qin, H.; Mao, J.; Yu, D.; Li, X.; Shen, A.; Yan, J.; Yu, L.; Guo, Z.; Ye, M.; Zou, H.;

545

Liang, X. Anal. Chem. 2017, 89, 3966-3972.

546

(42) Boersema, P. J.; Raijmakers, R.; Lemeer, S.; Mohammed, S.; Heck, A. J. Nat. Protoc. 2009, 4,

547

484-494.

548

(43) Hsu, J.-L.; Huang, S.-Y.; Chow, N.-H.; Chen, S.-H. Anal. Chem. 2003, 75, 6843-6852.

549

(44) Jiang, B.; Liang, Y.; Wu, Q.; Jiang, H.; Yang, K.; Zhang, L.; Liang, Z.; Peng, X.; Zhang, Y.

550

Nanoscale 2014, 6, 5616-5619.

551

(45) Ma, W.; Xu, L.; Li, X.; Shen, S.; Wu, M.; Bai, Y.; Liu, H. ACS Appl. Mater. Interfaces 2017, 9,

552

19562-19568.

553

(46) Zou, X.; Jie, J.; Yang, B. Anal. Chem. 2017, 89, 7520-7526.

554

(47) He, X. M.; Liang, X. C.; Chen, X.; Yuan, B. F.; Zhou, P.; Zhang, L. N.; Feng, Y. Q. Anal. Chem.

555

2017, 89, 9712-9721.

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For Table of Contents Only

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Facile fabrication of biomimetic chitosan membrane with honeycomb

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