Competitive Coadsorption Dynamics of Viruses ... - ACS Publications

Subscriber access provided by GAZI UNIV

Article

Competitive co-adsorption dynamics of viruses and dissolved organic matter to positively charged sorbent surfaces Antonius Armanious, Melanie Münch, Tamar Kohn, and Michael Sander Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.5b05726 • Publication Date (Web): 22 Feb 2016 Downloaded from http://pubs.acs.org on February 23, 2016

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

Environmental Science & Technology is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 34

Environmental Science & Technology

1

Manuscript

2

Competitive co-adsorption dynamics of viruses and dissolved organic

3

matter to positively charged sorbent surfaces

4 5

ANTONIUS ARMANIOUS1,2, MELANIE MÜNCH1, TAMAR KOHN2, MICHAEL SANDER1,*

6 7

1: Institute of Biogeochemistry and Pollutant Dynamics (IBP)

8

Department of Environmental Systems Science, ETH Zurich, Switzerland

9

2: Laboratory of Environmental Chemistry, School of Architecture, Civil and

10

Environmental Engineering (ENAC), École Polytechnique Fédérale de Lausanne

11

(EPFL), Lausanne, Switzerland

12

Submitted as manuscript to Environmental Science & Technology

13 14 15

* Corresponding author:

Michael Sander

16

email:

[email protected]

17

Phone:

+41 (0)44 632-8314

18

Fax:

+41 (0)44 633-1122

20

Number of Figures:

3

21

Number of Tables:

1

19

1

ACS Paragon Plus Environment


22

Abstract

23

Adsorption onto solid-water interfaces is a key process governing the fate and

24

transport of waterborne viruses. While negatively charged viruses are known to

25

extensively adsorb onto positively-charged adsorbent surfaces, virus adsorption in

26

such systems in the presence of negatively charged dissolved organic matter (DOM)

27

as co-adsorbate remains poorly studied and understood. This work provides a

28

systematic assessment of the adsorption dynamics of negatively charged viruses (i.e.,

29

bacteriophages MS2, fr, GA, and Qβ) and polystyrene nanospheres onto a positively

30

charged model sorbent surface in the presence of varying DOM concentrations. In all

31

systems studied, DOM competitively suppressed the adsorption of the viruses and

32

nanospheres onto the model surface. Electrostatic repulsion of the highly negatively

33

charged MS2, fr, and the nanospheres impaired their adsorption onto DOM adlayers

34

that formed during the co-adsorption process. In contrast, the effect of competition on

35

overall adsorption was attenuated for less-negatively charged GA and Qβ because

36

these viruses also adsorbed onto DOM adlayer surfaces. Competition in MS2-DOM

37

co-adsorbate systems were accurately described by a random sequential adsorption

38

model that explicitly accounts for unfolding of adsorbed DOM. Consistent findings

39

for viruses and nanospheres suggest that the co-adsorbate effects described herein

40

generally apply to systems containing negatively charged nanoparticles and DOM.

41

42

2


Page 2 of 34

Page 3 of 34


43

Introduction

44

Waterborne viruses cause a number of human diseases including meningitis,

45

myocarditis, hepatitis, and gastroenteritis.1 A concise understanding of the fate and

46

transport of these viruses is therefore critical for identifying, predicting, and possibly

47

interrupting environmental transmission pathways of these viruses. In both natural

48

and engineered systems, transport and infectivity of viruses are largely affected by

49

their adsorption onto solid-water interfaces.2-10 This process thus has received

50

considerable research attention. Adsorption has several energetic contributions

51

including virus-surface electrostatic interactions,11-21 the hydrophobic effect,21-24 van

52

der Waals interactions,11,12,14,25 and repulsive steric interactions.16,18,21,26 Electrostatics

53

play a major role for adsorption onto charged sorbents and are attractive or repulsive

54

if the viruses and the sorbents carry the opposite or the same net surface charges,

55

respectively.11-21 A large number of waterborne viruses are net negatively charged at

56

circumneutral pH27 and are therefore expected to strongly adsorb onto positively

57

charged surfaces, including those of iron (oxyhydr-)oxides and aluminum

58

oxides.11,14,19,20

59

Virus adsorption onto sorbent surfaces in laboratory experiments is commonly

60

investigated from solutions that contain only the virus and no other macromolecular

61

co-adsorbates. While allowing to selectively studying virus-surface interactions, this

62

experimental setup does not account for potential effects of co-adsorbates on virus

63

adsorption. Arguably the most abundant and ubiquitous macromolecular co-adsorbate

64

in natural and engineered systems is dissolved organic matter (DOM).28-31 DOM 3



65

contains nanometer-sized ‘macromolecular’ constituents that are conceptualized both

66

as supramolecular associations of smaller organic molecules32,33 and as longer-

67

chained polyelectrolytes.34 DOM has a pH-dependent net negative charge reflecting

68

the deprotonation of carboxylic and phenolic moieties in the DOM structure.35 As a

69

consequence, DOM strongly adsorbs onto positively charged sorbent surfaces.36-40 It

70

is thus reasonable to expect competitive adsorption between DOM and negatively

71

charged viruses for these sorbent surfaces.

72

Two scenarios are plausible for the effect of DOM as a co-adsorbate on virus

73

adsorption. In the first, the viruses and DOM directly compete for positively charged

74

adsorption sites and, at the same time, the virus does not adsorb onto DOM adlayers

75

(i.e., DOM structures that form on the adsorbent surface during the co-adsorption

76

process) due to unfavorable virus-DOM interactions. This scenario predicts

77

competitive suppression of virus adsorption by DOM and, as a consequence,

78

increasing virus transport and mobility. In the second scenario, the viruses and DOM

79

still directly compete for adsorption sites but the virus experiences net attractive

80

interactions with the DOM adlayers forming on the adsorbent surface. This scenario

81

predicts that virus adsorption onto the DOM adlayers attenuates the effect of virus-

82

DOM competitive adsorption. While indirect support for both scenarios can be found

83

in the literature,3,41-43 a systematic study of virus-DOM competition on positively

84

charged sorbents is missing from the literature. A fundamental understanding of

85

competition is, however, required to accurately predict the fate and transport of

86

waterborne viruses in DOM-containing systems.

4


Page 4 of 34

Page 5 of 34


87

The objective of this work was to provide a systematic assessment of virus

88

adsorption dynamics onto positively charged adsorbent surfaces in systems containing

89

DOM as co-adsorbates. To this end, we systematically studied the adsorption of four

90

bacteriophages (i.e., MS2, fr, GA and Qβ) onto positively charged amine-terminated

91

self-assembled monolayers (SAM-NH3+) in the presence of varying concentrations of

92

DOM (i.e., either Suwannee River humic acid (SRHA) or Suwannee River natural

93

organic matter (SRNOM)). The four viruses were selected because they have

94

spherical capsids with icosahedral symmetry and very similar diameters (Table 1) but

95

different capsid surface charge and polarity characteristics. These viruses are

96

considered surrogates for non-enveloped water-borne human viruses. MS2 and fr

97

have comparatively high negative surface charges, resulting in strong electrostatic

98

repulsion from DOM adlayers.21 Conversely, GA and Qβ carry smaller net negative

99

charges and have net favorable interactions with DOM adlayers.21 These differences

100

in virus-DOM adlayer interactions allow assessing the two scenarios outlined above.

101

The SAM-NH3+ surface is chemically well defined and served as model for positively

102

charged adsorbents in natural and engineered systems. Virus-DOM experiments were

103

complemented by co-adsorbate experiments containing monodisperse, negatively

104

charged polystyrene nanospheres (n-PS) and DOM to assess whether the results

105

obtained with viruses universally apply to co-adsorbate systems containing negatively

106

charged nanoparticles. All experiments were conducted under environmentally

107

relevant solution chemistries (i.e., pH 6 and I= 10 mM). The effect of increasing I on

108

co-adsorption dynamics was assessed in separate experiments. DOM concentrations

109

covered a wide range of environmentally relevant values (0.25 and 50 µgDOM·mL-1). 5



Page 6 of 34

110

The virus/DOM and n-PS/DOM ratios were selected to result in different extents of

111

competitive co-adsorption that were required to study this process on a mechanistic

112

level. To obtain molecular level insights into the spatiotemporal dynamics of viruses

113

and DOM on the sorbent surface, a random sequential adsorption (RSA) model was

114

developed and used to simulate adsorption in the MS2-SRHA co-adsorbate system.

115

Materials & Methods

116

DOM samples and chemicals

117

SRHA and SRNOM were obtained from the International Humic Substances

118

Society (St. Paul, MN, USA) and were used as received. These materials are

119

commonly used as models for DOM in aquatic systems. All chemicals were of

120

analytical grade and used as received. A complete list is provided in the Supporting

121

Information (SI).

122

Viruses and nanospheres

123

The bacteriophages MS2, fr, GA, and Qβ were propagated and purified as

124

detailed in the SI. Suspensions of polystyrene nanospheres (n-PS; Fluoresbrite YO

125

Carboxylate Microspheres, nominal diameter of 50 nm) were obtained from

126

Polysciences, Inc. and used as received. Table 1 summarizes adsorption-relevant

127

physicochemical properties of the viruses and n-PS.

128 129

Table 1. Physicochemical properties of the viruses and polystyrene nanospheres (nPS) relevant to adsorption. Diameter [nm]

MS2

fr

GA

Qβ β

n-PS

28.8a

28.6a

28.8a

29.4a

30.6b

6


Page 7 of 34


3.9b/3.9c Isoelectric point (IEP) Surface charge [C·m-2]d -3.2·102 45.6e Hydrophobic score

3.5b/4.5c -2.5·102 230.4e

4.1b/5.0c -0.7·102 176.0e

4.3b/4.9c -1.3·102 592.8e

< 3.0b n.d. n.d.

130 131 132 133 134 135 136 137 138 139 140 141 142

Values taken from the Viperdb2 website (accessed May 2015).44 These values were calculated from the X-ray crystallographic structures of MS2 (2MS2)45, fr (1FRS)46, GA (1GAV)47, and Qβ (1QBE)48. b. The hydrodynamic diameter of n-PS and the isoelectric points (IEP) of viruses and n-PS were determined by dynamic light scattering and electrophoretic mobility measurements, respectively, all conducted at pH 6 and I = 10 mM (adjusted with NaCl). The experimental data for n-PS is provided in Figure S1 in the SI. The mean diameter of n-PS is reported here. c,d. Estimated from the calculated surface charges of the four viruses considering only the ionizable amino-acids and the C- and N-termini that are located on the outer surfaces of the virus capsids; the surface charges were calculated for a solution with pH 6.21 e. Estimated from the areas and numbers of apolar patches on the outer surfaces of the virus capsids and by applying a hydrophobic scoring system that increases exponentially with the area of each identified apolar patch.21,49 The physicochemical properties of MS2, fr, GA, and Qβ were taken from Armanious et al (2015).21 n.d.= not determined.

143

Solutions

144

a.

All solutions were prepared in MilliQ water (resistivity ≈ 18.2 MΩ·cm;

145

Barnstead

NANOpure

Diamond)

and

buffered

to

pH

6

using

bis(2-

146

hydroxyethyl)amino-tris(hydroxymethyl)-methane. The solution pH and ionic

147

strength (I) were adjusted using 1 M HCl/NaOH and NaCl, respectively.

148

SRHA and SRNOM stock solutions (500 µgDOM·mL-1) were prepared by

149

dissolving the respective DOM in MilliQ water, followed by pH adjustment and

150

sterile filtration, as detailed in the SI. Directly before the adsorption experiments,

151

aliquots of the respective DOM stock solution were ten-fold diluted in pH 6 solutions

152

to final DOM concentrations of 50 µgDOM·mL-1. These solutions were used to prepare

153

experimental DOM solutions that contained either only DOM as single-adsorbate or

154

DOM as co-adsorbate to either one of the viruses or n-PS. The tested DOM

155

concentrations varied between 0.25 and 50 µgSRHA·mL-1.

7



156

Solutions containing one of the viruses or n-PS were prepared by diluting virus

157

and n-PS stock solutions into pH 6 solutions to final concentration of ≈5·1011

158

virion·mL-1 and ≈1.5·1011 nanospheres·mL-1, respectively. Virus/DOM and n-

159

PS/DOM co-adsorption experiments were started immediately after adding viruses or

160

n-PS to DOM-containing solutions.

161

Formation of positively charged model adsorbent surface

162

Amine-terminated self-assembled monolayers (SAM-NH3+) were prepared on

163

the surfaces of gold-coated sensors (QSX 301, Q-Sense AB) by placing them in 0.5–

164

2.0 mM ethanolic cysteamine solutions at room temperature for at least eight hours.

165

Details on the formation and verification of proper SAM formation are provided in

166

the SI.

167

Adsorption experiments

168

All adsorption experiments were conducted using a quartz crystal microbalance

169

with dissipation monitoring (QCM-D) equipped with four flow-through cells (Q-

170

Sense E4 system; Q-Sense AB). QCM-D monitors the changes in resonance

171

frequencies (∆fn) and energy dissipation values (∆Dn) of the fundamental oscillation

172

(n = 1) and several overtones (n = 3–13) of a piezo-quartz crystal that is embedded

173

into each sensor upon adsorption to and desorption from the sensor surface. The

174

measured frequency changes can be converted to changes in adsorbed mass using the

175

Sauerbrey equation (Equation 1):

8


Page 8 of 34

Page 9 of 34


176

∆ = − ×

∆

Eq. 1

177

where ∆ [ng·cm-2] is the areal mass density of the wet adlayer on the sensor

178

and C (= 17.7 [ng·cm-2·Hz-1]) is a sensor-specific proportionality constant. The

179

Sauerbrey equation was applicable in this study because the formed adlayers were

180

weakly dissipative, as evidenced from overlaying ∆fn/n traces for the different

181

overtones and ∆Dn·(∆fn/n)-1 2000 ng·cm-2 in the absence of SRHA to approximately 400

359

ng·cm-2 at 2.50 µgSRHA·mL-1 (Figures 2a,b). The observed effects of SRHA on

360

overall adsorption were fully consistent with competitive adsorption between the

361

viruses and SRHA for SAM-NH3+ surfaces and, at the same time, repulsion of MS2

362

and fr from formed SRHA adlayers: the sharp transitions from initially fast to

363

plateauing adsorption suggests that at the times when the transitions occurred the

364

SAM-NH3+ surfaces had become jammed by the viruses and SRHA, thereby

365

preventing additional adsorption. Some systems showed pronounced maxima in the

366

adsorbed masses during the transitions, suggesting that a fraction of the adsorbed

367

viruses were competitively displaced from the SAM-NH3+ surfaces by SRHA and,

368

hence, that some of the viruses were weakly adsorbed. Weaker adsorption may have

369

resulted from incomplete contact between the virus capsid and the SAM-NH3+

370

surfaces (e.g., due to partial blocking by SRHA) or to orientations of the adsorbed

371

viruses that resulted in a larger number of hydrophilic loops between the capsids and

372

the SAM-NH3+ surfaces and hence steric repulsion.16,21

18


Page 18 of 34

Page 19 of 34


373

The effects of SRHA on the adsorption profiles of GA and Qβ were distinctly

374

different from the effects for MS2 and fr (Figures 2c,d). First, for a given SRHA

375

concentration, the transitions from initial phases with high adsorption rates to the

376

subsequent phases of lower adsorption rates were much more gradual and occurred at

377

much larger adsorbed masses in the GA and Qβ than in the MS2 and fr co-adsorbate

378

systems. Adsorption in the GA and Qβ co-adsorbate systems also leveled off at much

379

larger final adsorbed masses. The observed effects are consistent with net attractive

380

interactions of GA and Qβ with SRHA adlayers: while directly competing with

381

SRHA for the SAM-NH3+ surface, Qβ and GA also adsorbed onto the surface of

382

SRHA patches that formed on the SAM-NH3+ surface during the co-adsorption

383

process. Adsorption onto SRHA adlayer patches is directly supported by the good

384

agreements between the final adsorbed masses in the co-adsorbate systems with the

385

highest SRHA concentration and in the systems in which GA and Qβ were adsorbed

386

onto SRHA adlayers pre-adsorbed onto the SAM-NH3+ surfaces (Figure 1d and open

387

symbols in Figure 2c,d). We note that adsorption of the viruses onto SRHA adlayers

388

in the co-adsorbate systems was also apparent from changes in the viscoelastic

389

properties of the adlayers, as detailed in the SI (Figure S2). The more pronounced

390

decrease in final adsorbed masses of GA than Qβ with increasing SRHA

391

concentrations (Figures 2c,d) is consistent with the lower affinity of GA than Qβ to

392

the SRHA adlayer surfaces (Figure 1d).

393

The changes in the adsorption profiles in the n-PS-SRHA co-adsorbate

394

systems with increasing SRHA concentrations were comparable to those measured for 19



395

MS2 and fr, consistent with direct competition of n-PS and SRHA for the SAM-NH3+

396

surfaces without adsorption of n-PS onto the SRHA adlayer patches formed during

397

co-adsorption. The similar co-adsorbate effects of SRHA on MS2/fr and n-PS

398

adsorption strongly suggest that the co-adsorbate dynamics described herein broadly

399

apply to negatively charged nanoparticles of both natural and anthropogenic origin.

400

The broader applicability of the results was further supported by two sets of

401

complementary experiments in which MS2 was co-adsorbed with (i) SRNOM, a

402

second DOM, under the same solution conditions and (ii) SRHA at a higher ionic

403

strength of I= 250 mM. As shown in Figures S3 and S4 in the SI, the effects of DOM

404

on the adsorption profiles in the MS2-SRNOM systems and the MS2-SRHA systems

405

at elevated I were similar to those described above in the MS2-SRHA system. Slightly

406

higher final adsorbed masses in the MS2-SRHA co-adsorbate systems at I= 250 mM

407

than 10 mM likely resulted from attenuation of virus-virus and virus-DOM

408

electrostatic repulsion at the higher I and, as a consequence, higher surface jamming

409

limits as well as slightly increased MS2 adsorption onto the SRHA adlayers. These

410

results are in agreement with the slightly increased MS2 adsorption onto the SRHA

411

adlayers in single-adsorbate experiments (Figure S4b).21 While not explicitly studied

412

here, the competitive suppression of DOM on virus adsorption are generally expected

413

to increase with increasing solution pH due to increasing net negative surface charges

414

of the DOM adlayers and the viruses and hence increased virus-DOM electrostatic

415

repulsion.21

20


Page 20 of 34

Page 21 of 34


416

Competitive adsorption of negatively charged nanoparticles and DOM on

417

positively charged sorbent surfaces also occurs in systems in which the adsorbates are

418

sequentially adsorbed. To illustrate this, we pre-adsorbed different amounts of SRHA

419

onto SAM-NH3+ surfaces, followed by rinsing and subsequent delivery of MS2 or n-

420

PS containing solutions to the sensors. As expected, the final masses at which

421

adsorption of MS2 and n-PS plateaued decreased with increasing SRHA pre-

422

adsorption (Figures S5 and S6, SI).

423

Modeling of competitive adsorption dynamics in MS2-SRHA co-adsorbate

424

systems. In a first simplistic modeling approach, we linearly combined the single-

425

adsorbate MS2 and SRHA adsorption profiles to estimate the times at which the

426

jamming limits for both adsorbates on the SAM-NH3+ surfaces were attained in the

427

MS2-SRHA co-adsorbate systems. Based on the assumptions that the final adsorbed

428

masses in the co-adsorbate systems were dominated by MS2, we used the estimated

429

times and the single-adsorbate MS2 adsorption profiles to estimate final adsorbed

430

masses of MS2 in the co-adsorbate systems (Figure S7). This modeling approach

431

resulted in overall good agreement between the predicted and experimental final

432

adsorbed masses in the co-adsorbate systems with the lower two SRHA

433

concentrations (i.e., 0.25 and 0.50 µgSRHA·mL-1) but underestimated the final adsorbed

434

masses in the co-adsorbate systems with the highest SRHA concentration (i.e., 2.50

435

µgSRHA·mL-1) (Figure S7). A more rigorous modeling approach was thus needed to

436

predict competition dynamics in all co-adsorbate systems.

21



Page 22 of 34

437

In a second step, we developed a model based on random sequential

438

adsorption (RSA) of a binary mixture of co-adsorbing spheres to obtain a concise

439

picture of the spatiotemporal dynamics of SRHA and MS2 arrangements on the SAM-

440

NH3+ surfaces in the co-adsorbate systems. MS2 was modeled as a rigid ‘sphere’ with

441

a diameter of d = 28.8 nm (Table 1; Figure 3a). The model had two input

442

variables for MS2: the circular footprint area of each MS2 virion on the sorbent

443

surface, parameterized by the footprint diameter, d

444

located below adsorbed virion and defines the area over which the virion interacts

445

with the SAM-NH3+ surface) and the maximum number of SRHA assemblies,

446

N , that may be pre-adsorbed on the SAM-NH3+ surface in the footprint area of

447

a virion without impairing its adsorption (Figure 3a). We varied d

448

and 10 nm and N between 0 and 2.

(the footprint is centrally

between 4

449

SRHA assemblies were modeled based on two conceptual approaches (Figure

450

3a). The first approach assumed spherical SRHA assemblies in solution that

451

maintained their shape upon adsorption onto the SAM-NH3+ surfaces (i.e., the SRHA

452

! spheres are ‘rigid’ and have the same diameters in solution as on the surface; d

453

!" = d ). While also assuming spherical SRHA assemblies in solution, the second

454

approach assumed that the assemblies partially unfolded on the SAM-NH3+ surfaces

455

! !" upon adsorption (i.e., d ≠ d ). The final thicknesses of SRHA adlayers

456

were 1 nm for both approaches corresponding to the experimentally determined

457

SRHA adlayer thickness at pH 6 and I= 10 mM, as detailed in the SI. For the first

22


Page 23 of 34


458

! !" approach, this meant that d = d = 1 nm. For the second approach,

459

! d = 2.7 nm was estimated from experimentally measured thicknesses of

460

SRHA adlayers formed on the SAM-NH3+ surfaces in separate experiments run under

461

conditions that disfavor SRHA unfolding (i.e., high I of 500 mM and high SRHA

462

concentration). The SRHA spheres were assumed to unfold on the sorbent while

463

conserving their volumes into disc-shaped circular assemblies with diameters of

464

!" d = 3.6 nm and heights of 1 nm (Figure 3a). While the second approach makes

465

several assumptions, SRHA unfolding is supported experimentally by systematic

466

changes in single-adsorbate SRHA adsorption profiles as a function of solution I and

467

SRHA concentrations, as detailed in the SI (Figure S8). Sorbent-inducted unfolding

468

is generally well-established for polyelectrolytes and proteins on sorbent surfaces.52-57

469

We note that the two approaches to model SRHA did not only differ in the footprint

470

area of adsorbed SRHA assembly, but also in the estimated number of SRHA

471

assemblies that adsorbed per MS2 virion onto the SAM-NH3+ surface, as detailed

472

below.

473

In the model calculations, a single adsorption attempt of a MS2 sphere was

474

alternated with a defined number of adsorption attempts of SRHA spheres. The ratios

475

of attempts of MS2 to SRHA spheres for the different co-adsorbate systems were

476

estimated from the initial adsorption rates in the MS2 and SRHA single-adsorbate

477

systems using a solvation model proposed by Bingen et al (2008; Figure S9)58, as

478

detailed in the SI. Allowing for SRHA unfolding on the SAM-NH3+ surfaces largely

479

decreased the total number of SRHA spheres that co-adsorbed per MS2 virion. For 23



480

example, the MS2:SRHA number ratios at the lowest experimental SRHA

481

! concentration of 0.25 µgSRHA·mL-1 decreased from 1:1000 to 1:55 for d = 1.0

482

and 2.7 nm, respectively. The positions at which individual spheres approached the

483

sorbent surface were randomly generated over a square area with side lengths of 1000

484

nm. For simplicity, we assumed purely vertical approach trajectories of the spheres to

485

the surface with no lateral movement. Adsorption attempts were unsuccessful if pre-

486

adsorbed molecules blocked the sorbent surface in the footprint area of an

487

approaching sphere (i.e., either SRHA or MS2 for approaching SRHA spheres or

488

SRHA, at numbers larger than N , or MS2 for approaching MS2).

24


Page 24 of 34

Page 25 of 34


489 490 491 492 493 494 495 496 497 498

Figure 3. Predictions of surface adsorption dynamics in the co-adsorbate systems containing MS2 and Suwannee River humic acid (SRHA) using a random sequential adsorption (RSA) model for a binary mixture of spheres. (a) Model input parameters for RSA model. MS2 virions were modeled as spheres with a fixed diameter, d . Simulations were run for different diameters of the circular footprint areas of MS2 virions on the sorbent surface, d , and for different maximum numbers of #$$%&'( SRHA assemblies, N , that were allowed in the circular footprint area between adsorbed virions and the adsorbent surface. Two diameters of adsorbed SRHA, !" d , were used as input parameters for the calculations, representing two 25



Page 26 of 34

516 517

conceptual models in which SRHA assemblies either maintained their solution conformation in adsorbed states or unfolded on the surface upon adsorption. (b) Snapshots of the spatial arrangements of MS2 and SRHA on the adsorbent surfaces at the ends of selected simulation runs. The simulations were run with the specified input parameters for a total of 1000 loops (snapshots I & II) and 10000 loops (snapshots III) of sequential one MS2 and 1000 (snapshots I & II) or 55 (snapshots III) SRHA adsorption attempts. (c) Changes in the simulated fractional coverages of #$$%&'( MS2, θ , on the adsorbent surface as a function of d and N and for !" the two conceptual models assuming conformational stability (i.e., d = 1.0 nm) !" and unfolding (i.e., d = 3.6 nm) of SRHA on the adsorbent surface. The shaded colored bar corresponds to the experimentally estimated θ for the simulated coadsorbate system with a concentration of SRHA of 0.25 µgSRHA·mL-1. (d) Changes in the simulated θ values on the adsorbent surface as a function of d for the conceptual model assuming unfolding of SRHA on the adsorbent surface (i.e., !" d = 3.6 nm) and for the three experimental SRHA concentrations (i.e., 0.25, 0.5, and 2.5 µgSRHA·mL-1). The corresponding experimental θ values are shown as colored shaded bars. Good agreement between simulated and experimental θ values was obtained for * of ≈ 7 to 8 nm, at all tested SRHA concentrations.

518

Figure 3b shows three snapshots I to III of a 200*200 nm area of the sorbent

499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515

519

surfaces at the end of selected simulations that were run with d

520

for the lowest experimental SRHA concentration of 0.25 µgSRHA·mL-1. Snapshots I

521

!" and II were run with d = 1.0 nm (i.e., no SRHA unfolding). Increasing N

522

from 0 (snapshot I) to 2 (snapshot II) increased the predicted fractional surface

523

coverages by MS2 from θ = 0.010 to 0.031. This increase mirrors expectations of

524

decreasing SRHA-MS2 competition as the number of pre-adsorbed SRHA assemblies

525

allowed within the footprint area of adsorbing virions increases. Snapshot III was

526

!" simulated with d = 3.6 nm (i.e., unfolding of SRHA on the sorbent) and

527

N = 0. The predicted θ values were almost tenfold higher than for snapshot

528

I (i.e., θ values of 0.094 and 0.010, respectively), reflecting decreased competition

529

in the simulations in which SRHA unfolded due to the smaller number of SRHA 26


= 8.0 nm and

Page 27 of 34


530

spheres that were delivered to the sorbent surface per virion. Consistently, SRHA

531

unfolding also resulted in a much lower number of adsorbed SRHA assemblies in

532

snapshot III as compared to snapshots I and II.

533

The effect of d

on predicted θ values is shown in Figure 3c for

534

!" simulations run with d = 1.0 nm (no SRHA unfolding; open symbols) and 3.6

535

nm (with SRHA unfolding; closed symbols). These simulations were run for the

536

lowest tested SRHA concentration of 0.25 µgSRHA·mL-1. The shaded bar at θ =

537

0.115±0.005 corresponds to the measured θ value determined in the respective co-

538

adsorbate experiment, as detailed in the SI. Simulated θ values decreased with

539

increasing d

540

increasing footprint areas on the sorbent surface required for MS2 adsorption.

541

!" Simulations with d = 1.0 nm resulted in much smaller predicted than

542

experimental θ values, even at the lowest d

543

N from 0 to 2 increased the predicted θ values, they remained smaller than

544

the experimental θ values. Conversely, the experimental θ values were

545

!" predicted with d = 3.7 nm and with reasonable input parameters of d

546

7.0 nm and N = 0. In fact, the experimental θ values at all three SRHA

547

concentrations (shaded bars in Figure 3d) were accurately predicted by simulations

548

!" with d = 3.7 nm, d

549

agreement between predicted and experimental θ at all SRHA concentrations with

550

a single set of MS2 and SRHA footprint parameters suggests that the main processes

, reflecting increasing competition between MS2 and SRHA with

of 4 nm. While increasing

=

between ≈ 7 and 8 nm and N = 0. The good

27



551

and dynamics of MS2-SRHA competition were accurately captured. While the

552

simulations results strongly support unfolding of SRHA upon adsorption as a key

553

process, it is important to note that other factors that are not explicitly accounted for

554

in the developed model could also affect competition dynamics. These factors include

555

the poly-dispersity of SRHA and lateral movement of the MS2 and SRHA above and

556

on the sorbent surface during the adsorption process.

557

Implications

558

This work provides direct evidence for and a mechanistic understanding of

559

competitive adsorption between negatively charged viruses and DOM onto positively

560

charged sorbent surface by combined experimental and modeling approaches.

561

Positively-charged sorbents are present both in natural systems (i.e., the surfaces of

562

iron (oxyhydr-)oxide and aluminum oxides in soils, sediments and lakes) and in

563

engineered systems (i.e., filter materials, ceramics and membranes). Based on the

564

results obtained herein, we predict that viruses that experience net repulsive

565

interactions with DOM adlayers will show largely decreased adsorption and removal

566

from solution and, thus, increased mobility in such systems in the presence of DOM

567

as co-adsorbate. These effects are expected to increase with decreasing virus/DOM

568

ratios and are thus expected to occur in most natural systems with much higher DOM

569

than virus concentrations. Conversely, we predict that the effects of competition by

570

DOM on adsorption are attenuated for viruses that experience net attractive

571

interactions with DOM adlayers and thus adsorb onto DOM adlayer surfaces that

572

form during the co-adsorption process. Predictions of virus fate and transport in

28


Page 28 of 34

Page 29 of 34


573

systems with positively charged sorbents and DOM thus require a detailed

574

understanding of the energetics of virus-DOM interactions.

575

The RSA model developed herein accurately predicted competition in the

576

MS2-SRHA co-adsorbate systems. The modeling results suggest that unfolding of

577

DOM upon adsorption needs to be accounted for to accurately predict virus-DOM

578

surface competition. We postulate that unfolding dynamics are generally important in

579

systems that contain structurally unstable polyelectrolytes. Future studies may extend

580

on the work presented herein by experimental investigations on DOM unfolding and

581

by increasing the complexity of the proposed model, for instance by explicitly

582

accounting for DOM polydispersity and DOM unfolding dynamics, by parameterizing

583

virus-DOM interactions, and by allowing for lateral movement of the adsorbates

584

before and after adsorption.

585

Based on coherent results from co-adsorbate systems containing negatively

586

charged nanospheres and DOM, we postulate that the competitive effects described

587

herein universally apply to systems containing negatively charged nanoparticles and

588

DOM as co-adsorbates on positively charged sorbents. The nanoparticles may be both

589

natural (e.g., enzymes and proteins) and anthropogenic (e.g., quantum dots, metallic

590

nanoparticles, fullerenes, and carbon nanotubes). From a methodological perspective,

591

this work demonstrates the capabilities of in situ surface techniques to directly assess

592

competition dynamics in such systems at the molecular level.

593

Supporting Information

29



594

Additional information and data on the preparation of solutions, virus

595

purification, tailoring of sensors, measuring electrophoretic mobilities and the

596

hydrodynamic diameter of n-PS, single-adsorbate and co-adsorbate experiments of

597

viruses and n-PS, and modeling of competitive adsorption of MS2/SRHA co-

598

adsorbate system. This material is available free of charge via the Internet at

599

http://pubs.acs.org/.

600

Acknowledgments We thank the Swiss National Science Foundation, SINERGIA Project

601 602

CRSI22_127568, for funding.

603

References

604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625

(1) (2) (3) (4) (5)

(6)

(7) (8) (9)

(10)

Bosch, A. Human enteric viruses in the water environment: a minireview. Int. Microbiol. 1998, 1 (3), 191–196. Bitton, G.; Mitchell, R. Effect of colloids on the survival of bacteriophages in seawater. Water Res. 1974, 8 (4), 227–229. Bitton, G. Adsorption of viruses onto surfaces in soil and water. Water Res. 1975, 9 (5-6), 473–484. Ward, C. H.; Ashley, C. S.; Moseley, R. H. Heat inactivation of poliovirus in wastewater-sludge. Appl. Environ. Microb. 1976, 32 (3), 339–346. Stagg, C. H.; Wallis, C.; Ward, C. H. Inactivation of clay-associated bacteriophage MS-2 by chlorine. Appl. Environ. Microb. 1977, 33 (2), 385– 391. Schaub, S. A.; Sagik, B. P. Association of enteroviruses with natural and artificially introduced colloidal solids in water and infectivity of solidsassociated virions. Appl. Microbiol. 1975, 30 (2), 212–222. Murray, J. P.; Laband, S. J. Degradation of poliovirus by adsorption on inorganic surfaces. Appl. Environ. Microb. 1979, 37 (3), 480. Belkin, S.; Colwell, R. R., Eds. Oceans and health: pathogens in the marine environment, 1st ed.; Springer: New York, 2006. Smith, E. M.; Gerba, C. P.; Melnick, J. L. Role of sediment in the persistence of enteroviruses in the estuarine environment. Appl. Environ. Microb. 1978, 35 (4), 685–689. Sakoda, A.; Sakai, Y.; Hayakawa, K.; Suzuki, M. Adsorption of viruses in 30


Page 30 of 34

Page 31 of 34


626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670

(11)

(12) (13)

(14)

(15)

(16) (17)

(18)

(19) (20)

(21)

(22)

(23)

(24)

(25)

water environment onto solid surfaces. Water Science and technology 1997, 35 (7), 107–114. Lipson, S. M.; Stotzky, G. Adsorption of reovirus to clay minerals: effects of cation-exchange capacity, cation saturation, and surface area. Appl. Environ. Microb. 1983, 46 (3), 673–682. Moore, R. S.; Taylor, D. H.; Reddy, M. M.; Sturman, L. S. Adsorption of reovirus by minerals and soils. Appl. Environ. Microb. 1982, 44 (4), 852–859. Taylor, D. H.; Moore, R. S.; Sturman, L. S. Influence of pH and electrolyte composition on adsorption of poliovirus by soils and minerals. Appl. Environ. Microb. 1981, 42 (6), 976–984. Fuhs, G. W.; Chen, M.; Sturman, L. S.; Moore, R. S. Virus adsorption to mineral surfaces is reduced by microbial overgrowth and organic coatings. Microb. Ecol. 1985, 11 (1), 25–39. Schijven, J. F.; Hassanizadeh, S. M.; de Bruin, R. H. Two-site kinetic modeling of bacteriophages transport through columns of saturated dune sand. J. Contam. Hydrol. 2002, 57 (3), 259–279. Penrod, S. L.; Olson, T. M.; Grant, S. B. Deposition kinetics of two viruses in packed beds of quartz granular media. Langmuir 1996, 12 (23), 5576–5587. Dowd, S. E.; Pillai, S. D.; Wang, S.; Corapcioglu, M. Y. Delineating the specific influence of virus isoelectric point and size on virus adsorption and transport through sandy soils. Appl. Environ. Microb. 1998, 64 (2), 405–410. Yuan, B.; Pham, M.; Nguyen, T. H. Deposition kinetics of bacteriophage MS2 on a silica surface coated with natural organic matter in a radial stagnation point flow cell. Environ. Sci. Technol. 2008, 42 (20), 7628–7633. Schiffenbauer, M.; Stotzky, G. Adsorption of coliphages T1 and T7 to clay minerals. Appl. Environ. Microb. 1982, 43 (3), 590–596. Zhuang, J.; Jin, Y. Virus retention and transport through Al-oxide coated sand columns: effects of ionic strength and composition. J. Contam. Hydrol. 2003, 60 (3-4), 193–209. Armanious, A.; Aeppli, M.; Jacak, R.; Refardt, D.; Kohn, T.; Sander, M. Viruses at solid-water interfaces: A systematic assessment of interactions driving adsorption. Environ. Sci. Technol. 2016, 50 (2), 732–743. Shields, P. A.; Farrah, S. R. Influence of salts on electrostatic interactions between poliovirus and membrane filters. Appl. Environ. Microb. 1983, 45 (2), 526–531. Bales, R. C.; Hinkle, S. R.; Kroeger, T. W.; Stocking, K.; Gerba, C. P. Bacteriophage adsorption during transport through porous media: chemical perturbations and reversibility. Environ. Sci. Technol. 1991, 25 (12), 2088– 2095. Britt, D. W.; Buijs, J.; Hlady, V. Tobacco mosaic virus adsorption on selfassembled and Langmuir-Blodgett monolayers studied by TIRF and SFM. Thin Solid Films 1998, 327, 824–828. Moore, R. S.; Taylor, D. H.; Sturman, L. S.; Reddy, M. M.; Fuhs, G. W. Poliovirus adsorption by 34 minerals and soils. Appl. Environ. Microb. 1981, 42 (6), 963–975. 31



671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715

(26)

(27) (28) (29) (30)

(31) (32) (33)

(34) (35)

(36) (37)

(38)

(39)

(40)

(41) (42) (43) (44)

Pham, M.; Mintz, E. A.; Nguyen, T. H. Deposition kinetics of bacteriophage MS2 to natural organic matter: role of divalent cations. J. Colloid. Interf. Sci. 2009, 338 (1), 1–9. Michen, B.; Graule, T. Isoelectric points of viruses. J. Appl. Microbiol. 2010, 109 (2), 388–397. Perdue, E. M.; Ritchie, J. D. Dissolved organic matter in freshwaters. Treatise on geochemistry 2003, 5, 273–318. Guo, L.; Santschi, P. H. Composition and cycling of colloids in marine environments. Reviews of Geophysics 1997, 35 (1), 17–40. Kalbitz, K.; Solinger, S.; Park, J. H.; Michalzik, B. Controls on the dynamics of dissolved organic matter in soils: a review. Soil science 2000, 165 (4), 277–304. Leenheer, J. A.; Croue, J. P. Characterizing aquatic dissolved organic matter. Environ. Sci. Technol. 2003, 37 (1), 18A–26A. Sutton, R.; Sposito, G. Molecular Structure in Soil Humic Substances: The New View. Environ. Sci. Technol. 2005, 39 (23), 9009–9015. Piccolo, A. The supramolecular structure of humic substances: a novel understanding of humus chemistry and implications in soil science. Adv. Agron. 2002, 75, 57–134. Swift, R. S. Macromolecular properties of soil humic substances: Fact, fiction, and opinion. Soil Science 1999, 164 (11), 790–802. Ritchie, J. D.; Perdue, E. M. Proton-binding study of standard and reference fulvic acids, humic acids, and natural organic matter. Geochim. Cosmochim. Acta 2003, 67 (1), 85–96. Davis, J. A. Adsorption of Natural Dissolved Organic-Matter at the Oxide Water Interface. Geochim. Cosmochim. Acta 1982, 46 (11), 2381–2393. Jardine, P. M.; McCarthy, J. F.; Weber, N. L. Mechanisms of dissolved organic carbon adsorption on soil. Soil Sci. Soc. Am. J. 1989, 53 (5), 1378– 1385. Gu, B.; Schmitt, J.; Chen, Z.; Liang, L.; McCarthy, J. F. Adsorption and desorption of natural organic matter on iron oxide: mechanisms and models. Environ. Sci. Technol. 1994, 28 (1), 38–46. Gu, B.; Schmitt, J.; Chen, Z.; Liang, L.; McCarthy, J. F. Adsorption and desorption of different organic matter fractions on iron oxide. Geochim. Cosmochim. Acta 1995, 59 (2), 219–229. Kaiser, K.; Guggenberger, G. The role of DOM sorption to mineral surfaces in the preservation of organic matter in soils. Org. Geochem. 2000, 31 (7), 711–725. Gerba, C. P.; Wallis, C.; Melnick, J. Fate of wastewater bacteria and viruses in soil. J. Irr. Drain. Div-ASCE 1975, 101 (3), 157–174. Lo, S. H.; Sproul, O. J. Polio-virus adsorption from water onto silicate minerals. Water Res. 1977, 11 (8), 653–658. Zhuang, J.; Jin, Y. Virus retention and transport as influenced by different forms of soil organic matter. J. Environ. Qual. 2003, 32 (3), 816–823. Carrillo-Tripp, M.; Shepherd, C. M.; Borelli, I. A.; Venkataraman, S.; 32


Page 32 of 34

Page 33 of 34


716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760

(45)

(46)

(47)

(48)

(49)

(50)

(51)

(52)

(53)

(54) (55) (56)

(57)

(58)

Lander, G.; Natarajan, P.; Johnson, J. E.; Brooks, C. L.; Reddy, V. S. VIPERdb2: an enhanced and web API enabled relational database for structural virology. Nucleic Acids Res. 2009, 37 (Database), D436–D442. Golmohammadi, R.; Valegard, K.; Fridborg, K.; Liljas, L. The refined structure of bacteriophage MS2 at 2.8 Å resolution. J. Mol. Biol. 1993, 234 (3), 620–639. Liljas, L.; Fridborg, K.; Valegard, K.; Bundule, M.; Pumpens, P. Crystal structure of bacteriophage fr capsids at 3.5 Å resolution. J. Mol. Biol. 1994, 244 (3), 279–290. Tars, K.; Bundule, M.; Fridborg, K.; Liljas, L. The crystal structure of bacteriophage GA and a comparison of bacteriophages belonging to the major groups of Escherichia coli leviviruses. J. Mol. Biol. 1997, 271 (5), 759–773. Golmohammadi, R.; Fridborg, K.; Bundule, M.; Valegard, K.; Liljas, L. The crystal structure of bacteriophage Qβ at 3.5 angstrom resolution. Structure 1996, 4 (5), 543–554. Jacak, R.; Leaver-Fay, A.; Kuhlman, B. Computational protein design with explicit consideration of surface hydrophobic patches. Proteins 2011, 80 (3), 825–838. Reviakine, I.; Johannsmann, D.; Richter, R. P. Hearing what you cannot see and visualizing what you hear: interpreting quartz crystal microbalance data from solvated interfaces. Anal. Chem. 2011, 83 (23), 8838–8848. Armanious, A.; Aeppli, M.; Sander, M. Dissolved organic matter adsorption to model surfaces: adlayer formation, properties and dynamics at the nanoscale. Environ. Sci. Technol. 2014, 48 (16), 9420–9429. Maroni, P.; Montes Ruiz-Cabello, F. J.; Cardoso, C.; Tiraferri, A. Adsorbed Mass of Polymers on Self-Assembled Monolayers: Effect of Surface Chemistry and Polymer Charge. Langmuir 2015, 31 (22), 6045–6054. Vermöhlen, K.; Lewandowski, H.; Narres, H. D. Adsorption of polyelectrolytes onto oxides—the influence of ionic strength, molar mass, and Ca2+ ions. Colloids Surf., A 2000, 163 (1), 45–53. Norde, W. My voyage of discovery to proteins in flatland . . .and beyond. Colloids Surf., B 2008, 61 (1), 1–9. Haynes, C. A.; Norde, W. Globular proteins at solid/liquid interfaces. Colloids Surf., B 1994, 2 (6), 517–566. van der Veen, M.; Stuart, M. C.; Norde, W. Spreading of proteins and its effect on adsorption and desorption kinetics. Colloids Surf., B 2007, 54 (2), 136–142. Wertz, C. F.; Santore, M. M. Effect of Surface Hydrophobicity on Adsorption and Relaxation Kinetics of Albumin and Fibrinogen: Single-Species and Competitive Behavior. Langmuir 2001, 17 (10), 3006–3016. Bingen, P.; Wang, G.; Steinmetz, N. F.; Rodahl, M.; Richter, R. P. Solvation effects in the quartz crystal microbalance with dissipation monitoring response to biomolecular adsorption. A phenomenological approach. Anal. Chem. 2008, 80 (23), 8880–8890.

33



TOC art 84x47mm (300 x 300 DPI)


Page 34 of 34

Competitive Coadsorption Dynamics of Viruses ... - ACS Publications

Recommend Documents