Electrochemical Stimulated Pickering Emulsion for Recycling of

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Electrochemical Stimulated Pickering Emulsion for Recycle of Enzyme in Biocatalysis Liao Peng, Anchao Feng, Senyang Liu, Meng Huo, Tommy Fang, Ke Wang, Yen Wei, Xiaosong Wang, and Jinying Yuan ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.6b09920 • Publication Date (Web): 14 Oct 2016 Downloaded from http://pubs.acs.org on October 21, 2016

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ACS Applied Materials & Interfaces

Electrochemical Stimulated Pickering Emulsion for Recycle of Enzyme in Biocatalysis Liao Peng,1 Anchao Feng,1 Senyang Liu,1 Meng Huo,1 Tommy Fang1, Ke Wang1, Yen Wei1, Xiaosong Wang2,*, and Jinying Yuan1,3,* 1 Key Lab of Organic Optoelectronics & Molecular Engineering, Department of Chemistry, Tsinghua University, Beijing 100084, P. R. China 2 Department of Chemistry, Waterloo Institute of Nanotechnology (WIN), University of Waterloo, Waterloo, Canada, N2L 3G1 3 Beijing Key Laboratory for Emerging Organic Contaminants Control, Tsinghua University, Beijing 100084, P. R. China

ABSTRACT. Potential-stimulated Pickering emulsions, using electrochemical responsive microgels as particle stabilizers, are prepared and used for biocatalysis. The microgels are constructed from the cyclodextrin functionalized 8-arm poly(ethylene glycol) (8A PEG-CD) and ferrocene modified counterparts (8A PEG-Fc) via a CD-Fc host-guest chemistry. Taking advantage of the redox reaction of Fc, the formation and deformation of the microgels and corresponding Pickering emulsions can be reversibly stimulated by external potential, and have been used for the hydrolysis of triacetin and kinetic resolution reaction of (R,S)-1-phenylethanol

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catalyzed by lipases. Potential stimulated destabilization of the emulsion realizes an effective separation of the products and enzymes recycling.

Keywords: Biocatalysis; Host-guest chemistry; Electrochemical responsiveness; Pickering emulsion; Polymer self-assembly

Emulsion systems are crucial in various commercial products and industrial processes.1-15 Conventional emulsions are generally stabilized by molecular surfactants or amphiphilic polymers, while Pickering emulsion, described by Ramsden and Pickering, is stabilized by particles absorbing at the liquid-liquid interface.1-15 Compared to conventional emulsions, Pickering emulsions offer many advantages, such as enhanced stability, improved biocompatibility, and environmental friendliness. Stimuli responsive Pickering emulsions have been developed as smart materials for a range of advanced applications, including heterogeneous catalysis, oil separation, and emulsion polymerization.4-15 Regulated by external stimuli, the particle emulsifiers in the stimulated systems can be activated and deactivated, so remote control of the emulsion properties as well as the recycle of the particle emulsifiers can be achieved. One of such applications lies in biocatalysis, which is usually performed in biphasic aqueous-organic systems to allow watersoluble enzyme to access hydrophobic substrates.12-14 Stimuli responsive Pickering emulsions can not only increase the area between the organic and aqueous phase, but also allows a simple product separation. The biocatalysts and emulsifiers can also be recovered easily for subsequent reaction cycles.


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A number of stimuli modes, including the change of pH, temperature and light, have been applied to regulate the Pickering emulsifiers in biocatalysis.12-14 For example, the Pickering emulsions, prepared using poly(N-isopropylacrylamide)-based microgels as stabilizers, are temperature stimulated and have been used for the reduction of acetophenone to (R)phenylethanol catalyzed by alcohol dehydrogenase.12 In another work, silica nanoparticles have been used to prepare a pH-sensitive emulsion for a reversible control of the kinetic resolution of (R,S)-1-phenylethanol.14 However, both pH and temperature stimuli have limitations. pHresponsive systems will cause the accumulation of salts and may be harmful to ionic strengthsensitive systems. Thermo-responsive systems are non-accumulative, but energy-demanding. In addition, the change of pH or temperature may have harmful or irreversible effects on the activity of many enzymes. Electrochemical responsive Pickering emulsions are nonaccumulative and can be stimulated at room temperature, it is therefore desirable to develop such biocatalytic systems. Synthesis of electrochemical responsive microgels for the emulsion, however, remains to be challenging and has not been realized. The supramolecular host-guest linker between β-cyclodextrin (β-CD) and guest molecules have been widely studied in stimuli responsive polymers,16-24 especially those based on ferrocene (Fc) with electrochemical sensitivity for redox activity of Fc.18-22 Block copolymers with this host-guest linker has been utilized for the construction of potential stimulated vesicles, micelles and nanofibers. The core-shell structures of these nanoparticles are not suitable for the construction of the potential stimulated Pickering emulsion. Electrochemical responsive hydrogels based on the CD/Fc host-guest chemistry have also been created, such as bulk gels formed from polymers or quantum dots.19-20, 22 If micro-size hydrogels can be created, they may


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be useful as stabilizers for the Pickering emulsions. However, there is almost no theory available on how to design building blocks for micro-size hydrogels.25-27 We hypothesize that the gelation can be confined within micro-size, if the building blocks have long water-soluble spacers between the host-guest linkers. As expected, 8A PEG-CD and 8A PEG-Fc (CD and Fc functionalized 8-arm poly(ethylene glycol) star polymers, 8A PEG) are able to self-assemble into potential stimulated microgels (Scheme 1) that have been used as stabilizer for Pickering emulsion for biocatalytic reactions. The potential stimulated reaction is mild and can be easily operated,18-22 which opens up new possibilities for many biocatalysis systems that are sensitive to high temperature and acid base reagents.28

SCHEME 1 The molecular structures of 8A PEG-CD and 8A PEG-Fc, and schematic of the potential-responsive controlled assembly and disassembly of the microgels.


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SCHEME 2 Schematic of the potential-responsive controlled assembly and disassembly of the microgels and its applications in biocatalytic reactions. The host polymer 8A PEG-CD was obtained from the click reaction of 8A PEG with alkyl end groups and β-CD modified with azide groups (Scheme S1), while the guest polymer 8A PEG-Fc was synthesized by the esterification between 8A PEG and ferrocenecarboxylic acid (Scheme S2). Their structures were characterized by 1H NMR and FT-IR (Fig. S1-S2). When the host and guest polymers with the equivalent amount of Fc and CD groups were mixed in water, and sonicated for 30 min, the viscosity of the solution increased, but no bulk gels were observed (Fig. S3). The existence of the host-guest interactions of these two components is confirmed by 1H NMR (Fig. S4-S6) and cyclic voltammetry (CV, Fig. S7). Rheological behaviour of the solution was measured. As shown in Figure 1a, the storage moduli (G’) significantly exceed the loss moduli (G’’) over the measured frequencies, suggesting the


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Figure 1. (a) The frequency sweep curve and the calculated absolute complex viscosity of 8A PEG-Fc/8A PEG-CD microgel (10 wt. %). (b)The DLS curve of 8A PEG-CD solution, 8A PEGFc/8A PEG-CD microgel (10 wt. %) before and after stimuli. TEM images of the 8A PEG-Fc/8A PEG-CD microgel (10 wt. %) before stimuli (c), after +0.80 V as oxidation potential stimuli (d), and after +0.20 V as reduction potential stimuli for 8 h (e). formation of microgels.10 The hydrodynamic diameters (Dh) of the gels are ca. 340 nm as measured using dynamic light scattering (DLS, Z-average diameter) (Figure 1b). TEM analysis reveals spherical morphology with diameters of ca. 200 nm (Figure 1c). 8A PEG-Fc is redox active due to the presence of Fc that is oxidized at the potential of +0.80 V (vs saturated calomel electrode, SCE) and reduced at +0.20 V (Fig. S7). This electrochemical response allows the reversible formation and deformation of the microgels. As shown in Figure 1b, when a potential (+0.80 V) is applied, the Dh of the microgel decreases from 340 nm to 10 nm, suggesting the disassembly of the particle. TEM images (Figure 1c and 1d) verify this result. When the applied potential switches to +0.20 V to the same solution, the microgel particles are


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recovered. As shown in Figure 1c and 1e, there is no obvious change in the morphology of the particles after a cycle of redox reaction of Fc. So it is proved that 8A PEG-Fc/8A PEG-CD microgel has reversible potential-responsive ability and can be used as a stabilizer for potential stimulated Pickering emulsion. A Pickering emulsion was prepared by mixing hexane and aqueous solution (v:v=1:1) in the presence of microgel particles (10 % wt.). The solution was mechanically sheared for 30 s using an Ultra Turrax (T18 Digital) homogenizer at 8000 rpm. Figure 2a and 2b show a photograph and an optical micrograph of the emulsion, respectively. As shown in Figure 2b, the size of the emulsion droplets is in the range of 10-40 μm. Methylene blue is used to stain the water phase, suggesting that the solution is an O/W emulsion (Figure 2c). The emulsions exhibit remarkable stability against extensive coalescence and no phase separation was observed after 12 h. Considering the easy trigger mode of the electrochemical stimuli and the biocompatibility of the 8A PEG-based microgel (Fig. S8), we investigated the enzyme catalysed biocatalytic reaction in the Pickering emulsion. Lipase from Pseudomonas cepacia (PCL) catalyzed hydrolysis of triacetin and kinetic resolution of (R,S)-1-phenylethanol were chosen as model reactions to evaluate the catalytic efficiency and recyclability of the enzyme. The specific activities of PCL are determined for the hydrolysis of triacetin in the emulsion system and compared with those performed in control solutions, including 0.1 M phosphate saline buffer (PBS, pH=8.0), aqueous solution of the microgels and water/hexane biphasic solution (ESI). As shown in Figure 3a, the Pickering emulsion obviously improves the specific activity of PCL as compared with the reactions in the other systems. Figure 3b compares the kinetic resolution of (R,S)-1-phenylethanol (Fig. S9a) in the Pickering emulsion and hexane/water biphasic medium. The reaction is catalysed by PCL via a


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transesterfication using vinyl acetate as the acyl donor. 1H NMR analysis (Fig. S9b) and a high performance liquid chromatography (HPLC, Fig. S10) with a chiral separation column are used for the kinetic evaluation. As shown in Figure 3b, one can see that PCL has a higher initial reaction rate and results in a higher conversion in the emulsion system as compared to the conventional biphasic system (Table S1). This enhancement in the activity of the lipase is attributed to the dramatic enlargement in the area of the oil-water interface in the Pickering

Figure 2. (a) Photograph of emulsions formed from hexane and aqueous solution (v:v=1:1) containing microgel particles (10 % wt.). Optical microscope image of the microgel (b) and with methylene blue staining (c) emulsion.12,

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In addition, the biocatalytic reaction in the emulsion achieves a very high

enantiomeric excess (Table S1) to yield (R)-1- phenylethyl acetate, suggesting the emulsion does not change the reaction mechanism. 12, 14 As we stated before, the formation and deformation of the microgel can be regulated by external potential, thus endowing the Pickering emulsion with electrochemical controlled reversibility. As shown in Figure 3c, the +0.80 V applied potential induces the phase separation. On one hand, the product is soluble in organic phase, thus can be easily separated. On the other


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Figure 3. (a) Specific activities of free PCL, in the presence of microgel in hexane, in biphasic system and in emulsion system, in hydrolysis of triacetin. (b) The kinetic plots of PCL in kinetic resolution of (R,S)-1-phenylethanol with vinyl acetate as the acyl donor.(c) Breaking and recovery of the emulsion by making the microgel disassemble or re-assemble using potential stimuli. (d) The specific activities of PCL in emulsion system in different cycles. hand, the enzyme is remained in the water phase, and the next cycle of reaction can be catalysed after adding organic phase containing substrate. As shown in Scheme 2, we performed three cycles of the kinetic resolution using the same batch of enzyme. The specific activities for these three reactions are compared in Figure 3d. As shown in Figure 3d, one can see that the activities after the three cycles of the reaction is still higher than that performed in the biphasic systems. The observed decline in the activity after each reaction cycle is due to the shearing sensitivity of the lipase (Fig. S11-S12).12, 14


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In summary, a novel supramolecular microgel with potential responsiveness is designed and developed using biocompatible 8A PEG modified with β-CD and Fc groups. The specific redoxactive β-CD/Fc host-guest interaction endows the microgel with electrochemical responsiveness, which can be applied to break and restore the emulsions in biocatalytic systems. Hydrolysis of triacetin and kinetic resolution of (R,S)-1-phenylethanol are studied to evaluate the activity of PCL in the Pickering emulsions. Potential stimuli are applied to realize the easy separation of the product and the recycle of the enzymes. Considering the significance of redox reaction in biological system 29 and the applications of electrical stimulation in cell differentiation and tissue engineering 30, this type of stimuli mode and microgel offer new possibilities for biocatalytic reactions.

ASSOCIATED CONTENT Supporting Information. Supporting information, including the detailed synthesis procedure and characterization, is provided. This material is available free of charge via the Internet at http://pubs.acs.org. AUTHOR INFORMATION Corresponding Author *[email protected] (J. Y.). *[email protected] (X. W.). Author Contributions The manuscript was written through contributions of all authors. All authors have given approval.


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ACKNOWLEDGMENT We gratefully acknowledge the financial support of the National Natural Science Foundation of China (51574086, 21374053), and the support of the opening project of Beijing Key Laboratory for Emerging Organic Contaminants Control. REFERENCES [1]

Li, Z.; Ngai, T. Microgel Particles at the Fluid–fluid Interfaces. Nanoscale 2013, 5, 1399-

1410. [2]

Tan, H.; Sun, G. Q.; Lin, W.; Mu, C. D.; Ngai, T. Gelatin Particle-Stabilized High

Internal Phase Emulsions as Nutraceutical Containers, ACS. Appl. Mater. Interfaces 2014, 6, 13977-13984. [3]

Li, Z. F.; Harbottle, D.; Pensini, E.; Ngai, T.; Richtering, W.; Xu, Z. H. Fundamental

Study of Emulsions Stabilized by Soft and Rigid Particles. Langmuir 2015, 31, 6282-6288. [4]

Tang, J. T.; Quinlan, J. P.; Tam, K. C. Stimuli-responsive Pickering Emulsions: Recent

Advances and Potential Applications. Soft Matter 2015, 11, 3512-3529. [5]

Geisel, K.; Isa, L; Richtering, W. The Compressibility of pH-Sensitive Microgels at the

Oil–Water Interface: Higher Charge Leads to Less Repulsion. Angew. Chem. Int. Ed. 2014, 53, 4905-4909. [6]

Fujii, S.; Read, E. S.; Binks, B. P.; Armes, S. P. Stimulus-Responsive Emulsifiers Based

on Nanocomposite Microgel Particles. Adv. Mater. 2005, 17, 1014-1018.


11


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

[7]

Page 12 of 16

Williams, M.; Warren, N. J.; Fielding, L. A.; Armes, S. P.; Verstraete, P.; Smets, J.

Preparation of Double Emulsions using Hybrid Polymer/Silica Particles: New Pickering Emulsifiers with Adjustable Surface Wettability. ACS. Appl. Mater. Interfaces 2014, 6, 2091920927. [8]

Ngai, T.; Behrens, S. H.; Auweter, H. Novel Emulsions Stabilized by pH and

Temperature Sensitive Microgels. Chem. Commun. 2005, 331-333. [9]

Chen, Z. W.; Zhou, L.; Bing, W.; Zhang, Z. J.; Li, Z. H.; Ren, J. S.; Qu, X. G. Light

Controlled Reversible Inversion of Nanophosphor-Stabilized Pickering Emulsions for Biphasic Enantioselective Biocatalysis. J. Am. Chem. Soc. 2014, 136, 7498-7504. [10]

Monti, F.; Fu, S. Y.; Iliopoulos, I.; Cloitre, M. Doubly Responsive Polymer-Microgel

Composites: Rheology and Structure. Langmuir 2008, 24, 11474-11482. [11]

Tang, J. T.; Lee, M. F. X.; Zhang, W.; Zhao, B. X.; Berry, R. M.; Tam, K. C. Dual

Responsive Pickering Emulsion Stabilized by Poly[2-(dimethylamino)ethyl methacrylate] Grafted Cellulose Nanocrystals. Biomacromolecules 2014, 15, 3052-3060. [12]

Wiese, S.; Spiess, A. C.; Richtering, W. Microgel-Stabilized Smart Emulsions for

Biocatalysis. Angew. Chem. Int. Ed. 2013, 52, 576-579. [13]

Wang, Z., van Oers, M. C. M., Rutjes, F. P. J. T. and van Hest, J. C. M. Polymersome

Colloidosomes for Enzyme Catalysis in a Biphasic System. Angew. Chem. Int. Ed. 2012, 51, 10746-10750.


12

Page 13 of 16

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


[14]

Liu, J.; G. J. Lan,; Peng, J.; Li, Y.; Li, C.; Yang, Q. H. Enzyme Confined in Silica-based

Nanocages for Biocatalysis in a Pickering Emulsion. Chem. Commun. 2013, 49, 9558-9560. [15]

Qu, Y. N.; Huang, R. L.; Qi, W.; Su, R. X.; He, Z. M. Interfacial Polymerization of

Dopamine in a Pickering Emulsion: Synthesis of Cross-Linkable Colloidosomes and Enzyme Immobilization at Oil/Water Interfaces. ACS. Appl. Mater. Interfaces 2015, 7, 14954-14964. [16]

Yu, G. C.; Jie, K. C.; Huang, F. H. Supramolecular Amphiphiles Based on Host–Guest

Molecular Recognition Motifs. Chem. Rev. 2015, 115, 7240-7303. [17]

Xue, M.; Yang, Y.; Chi, X. D.; Yan, X. Z.; Huang, F. H. Development of

Pseudorotaxanes and Rotaxanes: From Synthesis to Stimuli-Responsive Motions to Applications. Chem. Rev. 2015, 115, 7398-7501. [18]

Yan, Q.; Yuan, J. Y.; Cai, Z. N.; Xin, Y.; Kang, Y.; Yin, Y. W. Voltage-Responsive

Vesicles Based on Orthogonal Assembly of Two Homopolymers. J. Am. Chem. Soc. 2010, 132, 9268-9270. [19]

Peng, L.; Feng, A. C.; Wang, H.; Zhang, H. J.; Yuan, J. Y. Electrochemical Redox

Responsive Supramolecular Self-healing hydrogels Based on Host–guest Interaction. Polym. Chem. 2015, 6, 3652-3659. [20]

Nakahata, M.; Takashima, Y.; Yamaguchi, H.; Harada, A. Redox-responsive Self-healing

Materials Formed from Host−guest Polymers. Nat. Commun. 2011, 2, 511-516.


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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

[21]

Page 14 of 16

Miyamae, K.; Nakahata, M.; Takashima, Y.; Harada, A. Self-Healing, Expansion–

Contraction, and Shape-Memory Properties of a Preorganized Supramolecular Hydrogel through Host–Guest Interactions. Angew. Chem. Int. Ed. 2015, 54, 8984-8987. [22]

Du, P.; Liu, J. H.; Chen, G. S.; Jiang, M. Dual Responsive Supramolecular Hydrogel with

Electrochemical Activity. Langmuir, 2011, 27, 9602-9608. [23]

Zhang, Z.; Liu, K.; Li, J. A Thermoresponsive Hydrogel Formed from a Star–Star

Supramolecular Architecture. Angew. Chem. Int. Ed. 2013, 52, 6180-6184. [24]

Chen, G. S.; Jiang, M. Cyclodextrin-based Inclusion Complexation Bridging

Supramolecular Chemistry and Macromolecular Self-assembly. Chem Soc. Rev. 2011, 40, 22542266. [25]

Chen, B.; Liu, K. L.; Zhang, Z. X.; Ni, X. P.; Goh, S. H.; Li, J. Supramolecular

Hydrogels Formed by Pyrene-terminated Poly(ethylene glycol) Star Polymers through Inclusion Complexation of Pyrene Dimers with r-cyclodextrin. Chem. Commun. 2012, 48, 5638-5640. [26]

Yin, Y. Z.; Jiao, S. F.; Zhang, R. R.; Hu, X. X.; Shi, Z. F.; Huang, Z. Q. Construction of a

Smart Microgel Glutathione Peroxidase mimic Based on Supramolecular Self-assembly. Soft Matter 2015, 11, 5301-5312. [27]

Liu, Y. Y.; Fan, X. F.; Kang, T.; Sun, L. A Cyclodextrin Microgel for Controlled Release

Driven by Inclusion Effects. Macromol. Rapid Commun. 2004, 25, 1912-1916.


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Page 15 of 16

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


[28]

Chesters, C.; Wilding, M.; Goodall, M.; Micklefield, J. Thermal Bifunctionality of

Bacterial Phenylalanine Aminomutase and Ammonia Lyase Enzymes. Angew. Chem. Int. Ed. 2012, 51, 4344-4348. [29]

Huo, M.; Yuan, J. Y.; Tao, L.; Wei, Y. Redox-responsive Polymers for Drug Delivery:

from Molecular Design to Applications. Polym. Chem. 2014, 5, 1519-1528. [30]

Zhu, B.; Luo, S. C.; Zhao, H.; Lin, H. A.; Sekine, J.; Nakao, A.; Chen, C.; Yamashita, Y.;

Yu, H. H. Large Enhancement in Neurite Outgrowth on a Cell Membrane-mimicking Conducting Polymer. Nat. Commun. 2014, 5, 4523-4531.


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Electrochemical Stimulated Pickering Emulsion for Recycling of

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