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Agricultural and Environmental Chemistry

Preparation and Characterization of Size-Controlled Nanoparticles for HighLoading Lambda-Cyhalothrin Delivery through Flash Nanoprecipitation Kai Chen, Zhinan Fu, Mingwei Wang, Yin Lv, Chunxin Wang, Yue Shen, Yan Wang, Haixin Cui, and Xuhong Guo J. Agric. Food Chem., Just Accepted Manuscript • DOI: 10.1021/acs.jafc.8b02851 • Publication Date (Web): 17 Jul 2018 Downloaded from http://pubs.acs.org on July 18, 2018

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Journal of Agricultural and Food Chemistry

Preparation and Characterization of Size-Controlled Nanoparticles for High-Loading Lambda-Cyhalothrin Delivery through Flash Nanoprecipitation

Kai Chen1,2, Zhinan Fu1, Mingwei Wang1, Yin Lv2, Chunxin, Wang3, Yue Shen3, Yan Wang3*, Haixin Cui3*, Xuhong Guo1,2*

1

State Key Laboratory of Chemical Engineering, East China University of Science and Technology, Shanghai 200237, P. R. China

2

School of Chemistry and Chemical Engineering/ Engineering Research Center of Materials Chemical Engineering of Xinjiang Bingtuan, Shihezi University, Shihezi 832000, P. R. China

3

Institute of Environment and Sustainable Development in Agriculture, Chinese Academy of Agricultural Sciences, Beijing 100081, China

*

To whom correspondence should be addressed. E-mail: [email protected] (Yan

Wang), [email protected] (Haixin Cui), or [email protected] (Xuhong Guo)

ACS Paragon Plus Environment


1

ABSTRACT: Environmental concerns and low efficacy pose a challenge for

2

application of traditional insecticide formulations. In this study, a series of

3

lambda-cyhalothrin (LC) loaded nanoparticles (NPs) were produced by flash

4

nanoprecipitation (FNP), and the parameters that influence the nanoparticle size

5

were systematically studied. The narrow distribution and size-controllable NPs

6

formed stable suspensions in aqueous solution without organic solvents.

7

Amphiphilic block polymer PEG-PDLLA played an important role as a drug carrier,

8

and the encapsulation content was as high as 99%. The obtained NPs with high

9

loading of LC exhibited comparable toxicity with two commercial formulations at

10

low doses. It confirms that FNP technology is a promising and scalable method for

11

agrochemical delivery.

12 13

KEYWORDS: Flash nanoprecipitation, Nanosuspension, Lambda-cyhalothrin,

14

Block polymer

15 16


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17

INTRODUCTION

18

Conventional pesticide formulations are responsible for low efficiency,

19

continued use of harmful organic solvents and indiscriminate applications causing

20

environmental pollution.1-2 Nanotechnology can create pesticide formulations with

21

large surface area, easy attachment and fast mass transfer, showing significant

22

potential for developing efficacious and environmentally friendly pesticide

23

formulations. A series of smart nano delivery systems, such as pesticide delivery,

24

controllable release and response to environmental triggers have been developed for

25

agrochemicals in recent years.3-5 However, the complex preparation of nanoparticles

26

(NPs) has plagued many fabrication processes and developing scalable technology

27

from the lab to the industrial level while maintaining precise control of the final

28

product remains a significant challenge for the field of agrochemical formulation

29

development.

30

The “flash nanoprecipitation (FNP)” process has been proven as a rapid,

31

scalable,

and continuous bottom-up approach to produce monodispersed

32

nanoparticles (NPs) with tunable particle size.6-7 FNP involves a molecularly

33

dissolved hydrophobic active ingredient and amphiphilic block copolymer in

34

water-miscible organic solvent being impinged against two aqueous anti-solvent

35

streams rapidly in a confined four-jet multi-inlet vortex mixer (MIVM), producing

36

high levels of supersaturation on a millisecond time scale.8 Using this process, both

37

the drug and hydrophobic part of the diblock polymer are precipitated with a tunable,



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38

narrow size distribution. Meanwhile, the hydrophilic block, typically poly(ethylene

39

glycol) (PEG), protects the particle surface against growth and aggregation.9 The

40

active ingredients were thus encapsulated in the core under the hydrophobic

41

interactions

42

poly(ε-caprolactone) (PCL) and poly(D,L-lactide) (PDLLA), using the block

43

polymer’s self-assembling ability. These amphiphilic block polymers are widely

44

used as environmentally beneficial surfactants, because of their attractive properties:

45

it is biodegradable and environmentally friendly; it protects the drug from premature

46

degradation and evaporation; and it has the possibility to provide better interaction

47

with leaves by surface modification.10-13

with

the

hydrophobic

block,

such

as

polystyrene

(PS),

48

In recent years, the demands of lambda-cyhalothrin (LC), a widely used broad

49

spectrum hydrophobic pyrethroid insecticide, have increased rapidly due to its high

50

biological activity at low application dose.14 Although LC is considered safer than

51

other insecticides, potential hazards for non-target organisms and health risks for

52

humans are still possible.15 To reduce the environmental pollution and public health

53

risks associated with LC use, it is necessary to develop environmentally friendly and

54

highly efficient pesticide formulations. Among various formulation types,

55

water-based nanosuspensions have received the most attention for crop protection,

56

which provide uniform dispersion of hydrophobic active ingredients in aqueous

57

solutions and reduce the use of organic solvents, thus they are potentially useful for

58

diminishing environmental pollution.


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59

Inspired by these features of FNP and challenges of developing stable

60

water-based pesticide formulations, here we employed an FNP platform as a new

61

scalable process to produce nanosuspensions with narrow distributions for pesticide

62

delivery. In this study, we choose PEG-PDLLA as the drug carrier and prepared a

63

series LC-loaded nanosuspensions using FNP. A key objective of this work was

64

screening for suitable parameters of the LC-loaded NP formulations manufactured

65

by FNP. The particle size, distribution and stability of the nanosuspension were

66

investigated by dynamic light scattering (DLS). The morphology of NPs was

67

characterized by Transmission Electron Microscopy (TEM). An assessment of the

68

potency of the NPs is provided by the bioassay studies which determined the LC50 of

69

LC-loaded suspension versus two commercial LC formulations against Aphis

70

craccivora.

71 72 73

EXPERIMENTS

74

Materials

75

Lambda–cyhalothrin (LC) was provided by Yangnong Chemical Co., Ltd.

76

(Yangzhou,

China).

mPoly(ethyleneglycol)-b-poly(D,L-lactide)

77

PEG-PDLLA), was purchased from Daigang Biomaterial Co., Ltd (Shandong,

78

China). Tetrahydrofuran (THF) was purchased from Tianlian Fine Chemical Co., Ltd

79

(Shanghai, China). The water used in all experiments was obtained using a Milli-Q


(5k-b-10k,


80

water purification system. Other reagents and solvents were purchased from Beijing

81

Chemical Works (Beijing, China) and used as received.

82 83

Preparation of the LC-loaded nanoparticles

84

In the present study, LC-loaded NPs were prepared by FNP technology (Figure

85

1). A representative preparation of LC-loaded NPs via FNP is as follows. LC and

86

PEG-PDLLA were dissolved in THF and loaded into two syringes. The

87

concentration of PEG-PDLLA was fixed at 1 wt% (stream 1), and LC was dissolved

88

in THF (stream 2) with the mass ratio of LC to PEG-PDLLA at 0.5:1, 1:1, 3:1 and

89

5:1. The organic solution (fixed at 12 mL/min, stream 1 and stream 2) was fed,

90

along with Milli-Q water (stream 3 and stream 4), into a four inlet MIVM using two

91

digitally controlled syringe pumps (Harvard Apparatus, PHD2000). Samples were

92

further dialyzed against Milli-Q water (1 L milli-Q water per 10 ml NP suspension)

93

for 24 h to remove remaining organic solvent and free LC using a dialysis bag with

94

MWCO of 10 kDa membrane (Viskase) and stored at room temperature.

95 96

(INSERT Figure 1)

97 98

The flow pattern of fluids was described using the Reynolds number (Re).

99

Overall Re of the FNP system is expressed as the sum of four individual streams as

100

follows:


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101 102

= ∑ = ∑

(1)

103 104

where d is the stream inlet diameter of the mixer (1.1×10-3 m), s the cross sectional

105

areal of inlet (1.65×10-3 m2) and the four inlet have the same d and s. is the fluid

106

density (kg/m3), the fluid viscosity (kg/m s), and the steam flow rate

107

(m3/s).16 At 20 °C, is 1.0×103 kg/m3 and is 8.89×102 kg/m3. is 5.5×

108

10-4 Pa s for THF and 1.0×10-3 Pa s for water.

109 110

Characterization of the LC-loaded nanoparticles

111

The average diameter and polydispersity index (PDI) of the NPs were

112

measured with a Zetasizer Nano ZS90 (Malvern instruments, UK) at a scattering

113

angle of 90°. Samples were measured without further dilution at room temperature.

114

Nanoparticle morphologies of NPs were observed on a Hitachi HT7700

115

transmission electron microscope (Japan) at an acceleration voltage of 80 kV. One

116

drop of the NP suspension was deposited onto a standard copper grid and dried at

117

room temperature before observation.

118 119

Encapsulation efficiency and pesticide loading content

120

To study the encapsulation efficiency and drug loading content of the

121

encapsulated LC from the NPs, the concentration of LC in NPs was calculated based



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122

on the absorption at 278 nm using a UV-vis spectrophotometer (UV-2550). The

123

unknown concentration of encapsulated LC in NPs was determined from the linear

124

regression fit of absorbance versus concentration for LC standard solutions.

125

The encapsulation efficiency was determined as the difference between the

126

amount of pesticide in the nanoparticle suspension and the total amount of added LC

127

(eq. 2).

128 129

!"#$% &&$$'(%* =

+,-. -/ 01 .2 34 -2 ,-. -/ 34

× 100% (2)

130 131 132

The pesticide loading (PL) % was defined as the ratio of encapsulated LC in NPs to the total mass of the NPs (eq.3).

133 134

8 #$$9 "%9$:(%* =

-2 ,-. -/ 01 .2 34 -2 ,-. -/ -102

× 100% (3)

135 136

Stability test

137

To assess the stability of PEG-PDLLA/LC nanoparticles in the formulation, the

138

particle size and PDI of dialyzed suspensions were monitored at 0 °C and 25 °C for

139

14 days. LC loading content in nanoparticles was also studied by analyzing the

140

remaining LC with a UV-vis spectrophotometer.

141 142

Contact angle measurement on cucumber leaf


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143

The contact angles (CA) of nanosuspension droplets on hydrophilic foliage

144

surface were studied using live cucumber leaves. Two aqueous commercial LC

145

formulations (wettable powder (WP) and capsule suspension (CS)) were set as

146

control. Droplets (5 µL) were injected onto the target cucumber leaves and the

147

contact images were taken immediately using a contact angle tester (JC2000D2M,

148

Zhongchen Digital Technology Apparatus, Shanghai, China).

149 150

Biological assay

151

The toxicity of high concentration LC-loaded nanosuspension against Aphis

152

craccivora was evaluated using the leaf-dip method. The nanosuspensions were

153

diluted in Milli-Q water containing 0.1% Triton X-100 and the respective treatment

154

concentrations were prepared (5.00, 2.50, 1.25, 0.62, 0.31, 0.15 and 0.08 ppm). An

155

empty control check sample was also set according to statistical requirements. Discs

156

6 cm in diameter were punched from fresh soybean leaves and immersed in the

157

dilutions for 10 s, air-dried, and then placed upside down on the agar bed in Petri

158

dishes (6 cm diameter) with filter paper. The target insects could be exposed to lethal

159

LC concentrations when feeding on treated soybean leaf. Twenty apterous adults of

160

A. craccivora were assigned to the treated leaves in each Petri dish to determine

161

mortalities after 48 h. Aphis craccivora were cultured in a closed incubator at

162

25±1 °C with a photoperiod of 16L:8D and a relative humidity of 60±10%. Four

163

replicate batches of aphids were used. Two commercial LC formulations (emulsion



164

in water (EW) and microemulsion (ME)) were used as control samples following the

165

same procedure described above to test their toxicity. The toxicity regression

166

equations, LC50 and confidence limits were calculated using SPSS software (version

167

22.0, IBM).

168 169 170

RESULTS AND DISCUSSION

171

Effects of Reynolds numbers on nanoparticle size

172

In FNP, adequate and rapid turbulent mixing of solvent and antisolvent is a

173

prerequisite for the formation of nanoparticles. Effect of Reynolds numbers (Re) on

174

particle size was shown in Figure 2. Holding the water/THF ratio at 2:1, the

175

corresponding Re number increased from 856 to 1369 according to eq. 1 by

176

changing the flow rates of two syringe pumps.

177 178

(INSERT Figure 2)

179 180

For abbreviation, the PEG-PDLLA1/LC0.5 represents the initial mass

181

concentration of PEG-PDLLA and LC is 1 wt% and 0.5 wt%, respectively.

182

Nanoparticle sizes of both PEG-PDLLA1/LC0.5 and PEG-PDLLA1/LC1 decreased

183

with the increase of Re (Table S1). The competitive kinetics of PEG-PDLLA

184

aggregation and LC nucleation controlled particle size and distribution.17 A higher


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185

Re number represents more homogenous and effective mixing. Therefore, the

186

homogenous dispersion of sufficient PEG-PDLLA around higher Re number

187

terminated the growth of LC more rapidly and resulted in smaller particle size. The

188

influence of dialysis of NPs was also explored for constructing a successful

189

water-based formulation. As shown in Figure 3, we also noticed that the average

190

diameter of NPs decreased while PDI increased slightly after dialysis for 24 h.

191 192

(INSERT Figure 3)

193 194

Effect of water to THF ratio and mass ratio on nanoparticle size

195

The volume of antisolvent-to-solvent ratio is another key factor for forming and

196

controlling nanoparticles. In this section, the velocity of stream 1 (PEG-PDLLA

197

dissolved in THF) and stream 2 (LC dissolved in THF) were fixed at 12 mL/min.

198

The velocity of stream 3 and stream 4 (Milli-Q water) ranged from 12 to 96 mL/min,

199

and the corresponding final ratio of water to THF in the mixed solvents were

200

increased from 2:1 to 8:1 v/v.

201

Figure 4 shows the effect of different antisolvent-to-solvent ratios on particle

202

size and PDI (Table S2). As shown in Figure 4a and b, the size of NPs yielding

203

under different flow rate ratios followed a bell-shaped trend as flow rate ratios

204

increased. At low volume ratio of water to THF, the particle size increased first from

205

123 nm to 411 nm. This phenomenon could be explained by the fact that with an



206

increased volume of antisolvent, the dissolved LC may be more likely to participate

207

and aggregate to form larger particles.11 When the water/THF ratio further increased

208

to more than 4:1, the particle size showed a continuous decline to 258 nm. The

209

increased water/THF ratio represents a significant increase in flow rates. At a higher

210

water/THF ratio, the solvent streams were condensed and mixed more intensely,

211

thus the mass transfer of polymer stabilizer was more rapid in the confined chamber.

212

Therefore, the growth of particles was arrested in a shorter time and resulted in

213

decreased particle size. In addition, the formation of particles with low PDI is

214

because the mixing time (10-100 ms) is shorter than the particle formation time.18

215 216

(INSERT Figure 4)

217 218

The mass concentration ratio of PEG-PDLLA to LC will directly influence the

219

size and stability of the drug loading particle. In the case of forming uniform and

220

stable nanoparticles, lower mass ratio of PEG-PDLLA/LC means lower cost, which

221

is also an important factor studied in this experiment. The concentration of

222

PEG-PDLLA was held at 1 wt% (10 mg/ml) and the concentrations of LC were set

223

at 0.5, 1, 3 and 5 wt%. When the mass ratio of LC to PEG-PDLLA increased from

224

0.5:1 to 1:1, all samples exhibited a narrow distribution from 0.05 to 0.1 and the

225

particle size could be tuned in a large range by simply changing the

226

antisolvent-to-solvent ratio.


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227

When the mass ratio of LC to PEG-PDLLA increased above 3:1, the NPs with

228

a narrow distribution were only produced under higher speed flow rates (Figure 4c

229

and d). We hypothesized that when mixing under the relatively low speed condition

230

in MIVM, only a portion of LC cores were able to interact with stabilizers due to the

231

insufficient amount of PEG-PDLLA and less uniform flow with slow mass transfer.

232

As the flow rate increased significantly (water: THF=8:1, stream 1, 12 ml/min;

233

stream 2, 12 ml/min; stream 3, 96 ml/min; and stream 4, 96 ml/min), for higher Re

234

values and shorter mixing times, flow became more chaotic, ensuring enhanced

235

local mixing over the volume of the chamber. As a result, the rapid and intensive

236

turbulent-like mixing pattern assured homogeneous dispersion of the amphiphilic

237

polymer, and even the growth of excessive amounts of LC nuclei was arrested by the

238

absorption of PEG-PDLLA. However, the grafting density of PEG may decrease

239

from brush regime to mushroom regime with the increased mass concentration of

240

LC.19-20 The precipitate was observed on the bottom of the PEG-PDLLA1/LC5

241

nanosuspension after a few hours, which means the amphiphilic stabilizer failed to

242

prevent leakage of the encapsulated compound. With insufficient stabilizer, though it

243

arrested the growth of NPs, the tenuous corona of the hydrophilic stabilizing layer

244

could not maintain the stability of NPs from aggregating by providing steric

245

stabilization.21

246

High loading contents are preferred to reduce the cost of insecticide

247

formulations. Meanwhile, small particles were expected to embed between the veins



248

of target leaves for reduced rolling and improving the utilization rate of active

249

ingredients. Thus, the optimal formulation, 1 wt% (10 mg/ml) LC-loaded

250

nanosuspension with 1 wt% (10 mg/ml) PEG-PDLLA, was prepared by the FNP

251

method and used after dialysis in all remaining experiments.

252 253

Morphology of the nanosuspension

254

The appearance of the nanosuspension, shown in Figure 5a, was mainly related

255

to the concentration of LC. At a low concentration of LC, the appearance was clear

256

and colorless. As LC concentration increased, the system became a white, milky

257

liquid.

258

Transmission electron microscopy (TEM) was performed to investigate the

259

morphology of LC-loaded NPs. The optimized LC-loaded NP was prepared via FNP

260

using flow rates of 12, 12, 24, and 24 ml/min (mass ratio of LC: PEG-PDLLA= 1: 1).

261

The gibbous moon-like shape of particles (Figure 5b) observed without dialysis after

262

FNP proved that the residue THF in the solvent swelling the NPs and magnifying the

263

irregular morphology of core. According to previous studies, organic solvent should

264

be removed as rapidly as possible because its presence either has toxicological

265

consequences or may reduce particle stability.22 The dialyzed sample (Figure 5d)

266

exhibited more regular in shape and dispersed uniformly with a clear background.

267

The average sizes of LC-loaded nanoparticles (Figure 5c) measured from DLS were

268

generally consistent with those revealed on TEM images.


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269 270

(INSERT Figure 5)

271 272

Encapsulation efficiency and drug loading content

273

LC encapsulation efficiency (EE) of PEG-PDLLA protected NPs is estimated

274

about 99% on the basis of UV calibration at 278nm (Figure S1). This indicates that

275

almost all LC was encapsulated by PEG-PDLLA upon precipitation at the

276

millisecond scale. The high encapsulation efficiency (EE) could be attributed to the

277

extremely low solubility (5 × 10−6 g/L at 25 °C) of hydrophobic LC in water. When

278

mixed with the antisolvents, all solute precipitated and the trace amount of LC

279

dissolved in water could be disregarded. After all organic solvents were removed

280

from the system by dialysis, the surrounding water further restricted the highly

281

hydrophobic LC in the core of the NPs. Meanwhile the corresponding pesticide

282

loading (49.7%) was calculated using eq. 2. Results indicated that FNP was indeed

283

an effective method for encapsulating hydrophobic active ingredients and

284

PEG-PDLLA served as a proper vehicle.

285 286

Stability of nanosuspension

287

Temperature was the key parameter for the stability of PEG-PDLLA

288

encapsulated LC nanosuspension. Therefore, to evaluate the stability of NPs, the

289

changes of particle size, PDI and drug loading were monitored via DLS and UV-vis



290

in 14 days at 0 °C and 25 °C.

291 292

(INSERT Figure 6)

293 294

As shown in Figure 6a, the average size of NPs remained almost unchanged at

295

both 0 °C and 25 °C for up to half a mouth, with no aggregation. During storage, the

296

limited variation of PDI around 0.2 also demonstrated the robust storage stability of

297

LC-loaded NPs at room temperature in suspension form. The superior stability of

298

NPs in aqueous could be attributed to the tight binding between the highly

299

hydrophobic LC core and amphiphilic polymer. For lipophilic drugs with a log P

300

value above 6, FNP works well for forming highly stable NPs as an antisolvent

301

precipitation technique.23 Figure 6b shows that LC content in the nanosuspension

302

remained almost unchanged at 0 °C and decreased with very limited mass loss at

303

25 °C over 14 days. These results show that the nanosuspension exhibits a stable

304

state during storage, and relatively low temperature storage is more favorable for

305

maintaining stability.

306 307

Contact angle of NP suspension on cucumber leaf

308

The contact angle (CA) reflects the wettability of the solution on the target

309

surface, which is the key factor affecting the use of pesticide formulations. As shown

310

in Figure 7, the CA of NP suspension on cucumber leaf was 45.6°, smaller than the


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311

other two aqueous formulation (54.7° for commercial capsule suspension and 95.4°

312

for commercial wettable powder). With smaller CA, the NP suspension had better

313

infiltration on the hydrophilic leaf interface and was more likely to have better

314

adhesion and distribution performance on the target surface, which is highly

315

desirable to minimize the proportion of pesticides lost to the environment.

316 317

(INSERT Figure 7)

318 319

Biological efficacy evaluation

320

To further verify the feasibility of the PEG-PDLLA/LC nanosuspension via

321

FNP, bioactivity of PEG-PDLLA/LC was tested against Aphis craccivora using

322

dose-mortality bioassays (Figure 8). LC-loaded NPs with average size of 150 nm

323

(PDI=0.18) were prepared via FNP (PEG-PDLLA: 1 wt%, LC: 1 wt%, velocity of

324

four streams: 12, 12, 24, and 24 ml/min).

325 326

(INSERT Figure 8)

327 328

The bioassay results, summarized in Table 1, indicated that all three LC

329

formulations exhibited high activity against A. craccivora. There was no significant

330

difference in the susceptibility level between the commercial emulsion in water (EW)

331

(LC50=0.2664 ppm) and PEG-PDLLA/LC (LC50=0.2602 ppm); the LC50 value of



332

commercial microemulsion (ME) was slightly lower at 0.1924 ppm. The equivalent

333

of LC50 values in the same order of magnitude itself is interesting, since the values

334

of LC50 were always reduced in encapsulated systems due to containment of active

335

ingredients inside the NPs. In addition, a common critique of ME and EW

336

formulation is that acute toxicity and high rate of penetration cause potential risk to

337

non-target organisms and human health.24 Even with protective measures, organic

338

solvents can easily penetrate through the skin.25-26 Thus, workers who handle

339

pesticides are exposed to potentially acute chemical damage. In contrast, the solid

340

LC cores are protected by PEG-PDLLA in LC-loaded nanosuspension. The

341

hydrophilic block of PEG-PDLLA imparts uniform dispersion in aqueous

342

environments without organic solvents and prevents penetration of LC into the skin,

343

effectively reducing the exposure risk for farmers.

344

This paper demonstrated that FNP, a rapid and scalable method of assembling

345

solid-core block copolymer nanoparticles, can be used to develop water-based

346

formulations with hydrophobic active ingredients. Our results suggest that matching

347

the mass ratio of LC to PEG-PDLLA with turbulent mixing conditions during FNP

348

could produce stable and monodispersed LC nanosuspensions. We have also found

349

that FNP can effectively load hydrophobic LC, and the bioassay demonstrated that

350

PEG-PDLLA/LC exhibited the same toxicity level as commercial ME and EW

351

formulations.

352

The controllable particle size, high biological activity, and stability of NPs over


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353

time demonstrate the attractiveness of FNP to produce LC formulations, which

354

would both be efficacious and environmentally friendly. These findings significantly

355

expand the capabilities of FNP and provide new routes for the development of

356

agrochemical formulations.

357 358

Supporting Information

359

UV-vis absorbance spectra and calibration curve of LC at 278 nm.

360

Particle size and PDI at different Re.

361

Particle size and PDI at different water/THF ratio and PEG-PDLLA/LC mass ratio.

362 363

Notes

364

The authors declare no competing financial interests.

365 366

Acknowledgement

367

We are grateful for financial support from the National Natural Science

368

Foundation of China (21476143, 51773061, 31701825 and 5171101370), the Major

369

National Scientific Research Program of China (2014CB932200), the National Key

370

Research and Development Program of China (2016YFD0200500) and the Open

371

Project of Key Laboratory of Materials-Oriented Chemical Engineering of Xinjiang

372

Uygur Autonomous Region (No. 2016BTRC006).

373



374

ABBREVIATIONS USED

375

LC, Lambda-Cyhalothrin; FNP, flash nanoprecipitation; NPs, nanoparticles; MIVM,

376

multi-inlet vortex mixer; PEG-PDLLA, mPoly(ethyleneglycol)-b-Poly(D,L-lactide);

377

DLS, dynamic light scattering; TEM, transmission electron microscopy; THF,

378

tetrahydrofuran; Re, Reynolds number; PDI, polydispersity index; CA, contact angle;

379

WP, wettable powder; CS, capsule suspension; EW, Emulsion in Water; ME,

380

Microemulsion

381 382 383

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oral delivery of insulin. Biomaterials 2017, 130, 28-41.

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Figure captions

462

Figure 1. Schematic illustrating the FNP process for preparing PEG-PDLLA/LC

463

nanosuspension and bioassay.

464

Figure 2. Effect of Re on the average particle sizes and PDI of LC-loaded

465

nanoparticles for (a) PEG-PDLLA1/LC0.5 and (b) PEG-PDLLA1/LC1.

466

Figure 3. Effect of dialysis on the average particle sizes and PDI of LC-loaded

467

nanoparticles PEG-PDLLA1/LC1 obtained before (black curve) and after (red curve)

468

dialysis.

469

Figure 4. Effect of water/THF ratio and mass ratio on the average particle sizes and

470

PDI of LC-loaded nanoparticles; water/THF ratio ranged from 2:1 to 8:1;

471

concentration of PEG-PDLLA was fixed at 1 wt%, mass ratio of PEG-PDLLA/LC is

472

(a) 1:0.5, (b) 1:1, (c) 1:3 and (d) 1:5.

473

Figure 5. (a) Appearance of LC-loaded NPs with 1 wt% (left) and 0.1 wt% (right)

474

initial LC concentration. (b)TEM images of LC-loaded NPs without dialysis, (c) size

475

distribution and (d) morphology of PEG-PDLLA1/LC1 after dialysis.

476

Figure 6. The stability of LC-loaded NPs over 14 days. (a) Average particle size and

477

PDI variation and (b) LC contents in nanoparticles before and after 0 °C and 25 °C

478

for 14 days.

479

Figure 7. Contact angle of (a) commercial capsule suspension, (b) commercial

480

wettable powder and (c) NP suspension on cucumber leaf.

481

Figure 8. Mortality rate of A. craccivora as a function of selected concentration of



482

LC loaded nanoparticles and two commercial formulations.

483


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484

Table 1. Bioassay results of LC-loaded nanosuspension and two commercial

485

formulations against Aphis craccivora. Toxicity Regression

Correlation

LC50a

Confidence Limit 95%

Equation

Coefficient

(ppm)

(ppm)

PEG-PDLLA/LC

y=5.4869+0.8337x

0.9471

0.2606

0.1598-0.3750

Commercial EW

y=5.4702+0.8184x

0.9822

0.2664

0.1628-0.3848

Commercial ME

y=5.6188+0.8646x

0.9354

0.1924

0.1082-0.2871

Formulation

486

a

LC50 = Lethal concentration cause 50% mortality

487



488

Figure 1. Schematic illustrating the FNP process for preparing PEG-PDLLA/LC

489

nanosuspension and bioassay.

490 491


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492

Figure 2. Effect of Re on the average particle sizes and PDI of LC-loaded

493

nanoparticles for (a) PEG-PDLLA1/LC0.5 and (b) PEG-PDLLA1/LC1.

494

495 496



497

Figure 3. Effect of dialysis on the average particle sizes and PDI of LC-loaded

498

nanoparticles PEG-PDLLA1/LC1 obtained before (black curve) and after (red curve)

499

dialysis.

500

501 502


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503

Figure 4. Effect of water/THF ratio and mass ratio on the average particle sizes and

504

PDI of LC-loaded nanoparticles; water/THF ratio ranged from 2:1 to 8:1;

505

concentration of PEG-PDLLA was fixed at 1 wt%, mass ratio of PEG-PDLLA/LC is

506

(a) 1:0.5, (b) 1:1, (c) 1:3 and (d) 1:5.

507

508 509



510

Figure 5. (a) Appearance of LC-loaded NPs with 1 wt% (left) and 0.1 wt% (right)

511

initial LC concentration. (b)TEM images of LC-loaded NPs without dialysis, (c) size

512

distribution and (d) morphology of PEG-PDLLA1/LC1 after dialysis.

513

514 515


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516

Figure 6. The stability of LC-loaded NPs over 14 days. (a) Average particle size and

517

PDI variation and (b) LC contents in nanoparticles before and after 0 °C and 25 °C

518

for 14 days.

519

520 521



522

Figure 7. Contact angle of (a) commercial capsule suspension, (b) commercial

523

wettable powder and (c) NP suspension on cucumber leaf.

524

525 526


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527

Figure 8. Mortality rate of A. craccivora as a function of selected concentration of

528

LC loaded nanoparticles and two commercial formulations.

529

530 531 532 533



534 535

Table of Contents Graphic:

536

537 538 539


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Preparation and Characterization of Size ... - ACS Publications

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