Bioinspired Microfluidic Device by Integrating a Porous Membrane

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Bioinspired Microfluidic Device by Integrating a Porous Membrane and Heterostructured Nanoporous Particles for Biomolecule Cleaning Jun-Bing Fan,†,# Jing Luo,†,‡,# Zhen Luo,†,‡,# Yongyang Song,†,‡ Zhao Wang,†,‡ Jingxin Meng,† Binshuai Wang,§ Shudong Zhang,§ Zijian Zheng,∥ Xiaodong Chen,⊥ and Shutao Wang*,†,‡ †

CAS Key Laboratory of Bio-inspired Materials and Interfacial Science, CAS Center for Excellence in Nanoscience, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, People’s Republic of China ‡ University of Chinese Academy of Sciences, Beijing 100049, People’s Republic of China § Department of Urology, Peking University Third Hospital, Beijing 100191, People’s Republic of China ∥ Laboratory for Advanced Interfacial Materials and Devices, Institute of Textiles and Clothing, The Hong Kong Polytechnic University, Hong Kong, SAR, People’s Republic of China ⊥ Innovative Center for Flexible Devices, School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore S Supporting Information *

ABSTRACT: Mimicking the structures and functions of biological systems is considered as a promising approach to construct artificial materials, which have great potential in energy, the environment, and health. Here, we demonstrate a conceptually distinct design by synergistically combining a kidney-inspired porous membrane and natural sponge-inspired heterostructured nanoporous particles to fabricate a bioinspired biomolecule cleaning device, achieving highly efficient biomolecule cleaning spanning from small molecules to macromolecules. The bioinspired biomolecule cleaning device is a two-layer microfluidic device that integrates a polyamide porous membrane and heterostructured nanoporous poly(acrylic acid)−poly(styrene divinylbenzene) particles. The former as a filtration membrane isolates the upper sample liquid and the latter fixed onto the bottom of the underlying channel acts as an active sorbent, particularly enhancing the clearance of macromolecules. As a proof-of-concept, we demonstrate that typical molecules, including urea, creatinine, lysozyme, and β2-microglobulin, can be efficiently cleaned from simulant liquid and even whole blood. This study provides a method to fabricate a bioinspired biomolecule cleaning device for highly efficient biomolecule cleaning. We believe that our bioinspired synergistic design may expand to other fields for the fabrication of integrated functional devices, creating opportunities in a wide variety of applications. KEYWORDS: bioinspired device, synergistic design, biomolecule cleaning, heterostructured nanoporous particles, porous membrane, filtration and adsorption acetate membranes,15 polyamid (PAM) membranes,16 and others, have been widely developed and used on hemodialyzers for clinical kidney replacement treatment. However, unlike the natural kidney, those artificial porous membranes are more effective at clearing small molecules but are limited in clearing macromolecules.17 The insufficient clearance of macromole-

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n nature, biological systems have evolved to create almost perfect structures and functions for maintaining life activities after billions of years of evolution.1−3 Learning from nature, scientists have aimed to develop man-made interfacial materials for their great potential in fog and water collection,4−6 oil−water separation,7,8 energy harvesting,9,10 cancer diagnosis,11 immunotherapy,12 and so on.13 For example, inspired by the filtration function of the glomerulus in the kidney, a large variety of artificial porous membrane materials, such as polyethersulfone membranes,14 cellulose © XXXX American Chemical Society

Received: May 21, 2019 Accepted: July 8, 2019 Published: July 8, 2019 A

DOI: 10.1021/acsnano.9b03918 ACS Nano XXXX, XXX, XXX−XXX

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Figure 1. Overview of our bioinspired approach. The porous membrane structure of a molecule-filtrating glomerulus inspired the rational design of a bioinspired biomolecule cleaning device that can filter biomolecules. We further designed the bioinspired biomolecule cleaning device by introducing porous adsorption materials analogous to that of a natural porous sponge for highly efficient molecule adsorption. Thus, a conceptually distinct design by synergistically combining a kidney-inspired porous membrane and natural sponge-inspired heterostructured nanoporous particles can be harnessed to design a bioinspired molecule clearance system for highly efficient molecule clearance.

wide range of biomolecules, including the small molecules (urea and creatinine) and macromolecules (lysozyme and β2microglobulin), can be effectively cleaned from simulant liquid and even whole blood, with high efficiency.

cules often causes long-term risks, such as dialysis-related amyloidosis, cardiovascular disease, and so on.18 Thus, bioinspired materials that mimic the structure or function of biological system in certain aspects often meet constraints in practical applications. Recently, a synergistic design approach has been developed to fabricate artificial materials by combining two or more principles derived from different biological systems, resulting in superior functions compared to those materials designed by traditional bioinspired single mimicking.19−23 For example, a man-made interfacial material was fabricated by synergistically combining the water-harvesting of desert beetles, the asymmetric slope of cactus spines, and lubricant surface of pitcher plants, achieving 6-fold higher water droplet growth and transport far beyond other synthetic surfaces.19 This progress demonstrates that combining several functions from different biological systems enables successful creation of one supermaterial. So we examine whether we can combine a few functional materials to achieve one system or device with ideal functions. Herein, we demonstrate a bioinspired biomolecule cleaning device that synergistically combines two distinct materials (a kidney-inspired porous membrane and natural sponge-inspired heterostructured nanoporous particles), achieving highly efficient clearance of molecules spanning from small molecules to macromolecules. In our bioinspired device, the porous membrane as a filter allows effective biomolecule diffusion and the amphiphilic poly(acrylic acid)−poly(styrene divinylbenzene) (PAA−PSDVB) heterostructured nanoporous particles can facilitate the clearance of macromolecules. In this device, a

RESULTS AND DISCUSSION Synergistic Design of Bioinspired Biomolecule Cleaning System. The bioinspired synergistic design is derived from a combination of strategies used by two different materials inspired from biological examples: kidney and natural sponge. The porous membrane structure of the glomerulus in the kidney allows for efficient filtration of metabolic biomolecules, while the natural sponge, with a dense pore structure, can also effectively adsorb molecules. Thus, synergistically combining these two distinct materials, a bioinspired system could be designed for highly efficient biomolecule cleaning (Figure 1). As a proof-of-concept for one potential application of our bioinspired biomolecule cleaning device in blood purification, when bloodstream and dialysate enter the channel convectively, biomolecules (including small molecules and macromolecules) in the bloodstream and electrolyte ions in the dialysate would diffuse across the porous membrane. Simultaneously, those heterostructured nanoporous particles fixed into the dialysate channel would adsorb these molecules that diffused through the porous membrane, allowing highly effective molecular transport (Figure 2a, Movie S1). As shown in Figure 2b, the bioinspired biomolecule cleaning device consists of two-layered serpentine channel chips, the superhydrophilic PAM porous membrane B

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Figure 2. Design and fabrication of bioinspired biomolecule cleaning device. (a) Schematic of the design principle of the bioinspired biomolecule cleaning device. The bioinspired biomolecule cleaning device was designed by synergistically combining a kidney-inspired porous membrane and natural sponge-inspired heterostructured nanoporous particles for highly efficient molecule clearance. As a proof-ofconcept for one application of our bioinspired biomolecule cleaning device in blood purification, metabolic molecules could be efficiently cleaned by the cooperation effect of membrane filtration and particle adsorption. (b) Schematic of the bioinspired biomolecule cleaning device. The bioinspired biomolecule cleaning device consisted of two-layered chips with a serpentine microchannel, the polyamide (PAM) porous membrane, and poly(acrylic acid)−poly(styrene divinylbenzene) (PAA−PSDVB) heterostructured nanoporous particles. In the device, these PAA−PSDVB particles were fixed into the dialysate channel and separated from the bloodstream by the PAM membrane. (c, d) Photograph of the serpentine microchannels of the bioinspired biomolecule cleaning device. (e) Photograph of the integrated bioinspired biomolecule cleaning device. (f) Photograph of the simulated fluid convectively entering into the serpentine microchannels of the bioinspired biomolecule cleaning device. (g) Photograph of the integrated bioinspired biomolecule cleaning device fixed on the arm for wearable healthcare.

was stained blue. In addition, the bioinspired biomolecule cleaning device could be fixed on the arm for wearable healthcare (Figure 2g). These results demonstrated that a bioinspired biomolecule cleaning device can be fabricated by integrating a porous membrane and heterostructured nanoporous particles into microfluidic channels. Emulsion Interfacial Polymerization for the Synthesis of Heterostructured Nanoporous Particles and Their Fixing into a Microfluidic Channel. Recently, we have demonstrated that the heterostructured nanoporous particles have significant abilities to separate various biomacromolecules through the synergistic effect of multiple interactions (hydrophilic/hydrophobic and electrostatic interactions) in comparison with their homogeneous particles. Therefore, in this study, these heterostructured nanoporous particles that were designed to be fixed in our bioinspired device would be beneficial for cleaning those macromolecules. The heterostructured nanoporous particles were synthesized by emulsion interfacial polymerization, in which hydrophobic styrene (St) and divinylbenzene (DVB) in a hydrophilic acrylic acid (AA) aqueous emulsion were constructed to perform an interfacial

and amphiphilic PAA−PSDVB heterostructured nanoporous particles. The commercially available PAM porous membrane was used to construct the membrane filtration module. The PAM-based porous membrane as a classic hemodialysis membrane has been widely used in clinical hemodialysis systems because of its good blood compatibility (Figures S1− S4).24−26 In the device, PAA−PSDVB heterostructured nanoporous particles were fixed onto the bottom of a microfluidic channel and separated from the bloodstream by a PAM porous membrane. The microfluidic channel in the device was designed with a serpentine shape to facilitate the molecular exchange. The serpentine channel with a 100 μm depth and 1 mm width was fabricated by a two-step PDMS replication on a Si wafer mask (Figure 2c and d) (the detailed fabrication can be found in the Experimental Section). Figure 2e demonstrates the integrated bioinspired biomolecule cleaning device with a PAM porous membrane and PAA− PSDVB heterostructured nanoporous particles. Figure 2f shows that both of the simulated fluids could freely enter the channels of bioinspired biomolecule cleaning device. The simulated blood was stained red, and the simulated dialysate C

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Figure 3. Emulsion interfacial polymerization for the synthesis of heterostructured nanoporous particles and their fixing into a microchannel. (a) Schematic of the fabrication of PAA−PSDVB heterostructured nanoporous particles by emulsion interfacial polymerization. (b) Scanning electron microscope (SEM) image of the PAA−PSDVB heterostructured nanoporous particles. These heterostructured nanoporous particles exhibited excellent monodispersity and uniformity. (c) High-resolution transmission electron microscopy (HRTEM) image of embedded heterostructured nanoporous particles after microtome cutting and staining with phosphotungstic acid. (d) Surface potential of a heterostructured nanoporous particle. (e, f) SEM images of the fixed heterostructured nanoporous particle in a microchannel.

polymerization, according to our previous works.27−29 The polymerization allowed the fabrication of negatively charged PAA−PSDVB heterostructured nanoporous particles with amphiphilicity (Figure 3a,d and Figure S5). These particles with diameters of 7.8 ± 0.19 μm exhibited excellent monodispersity and uniformity (Figure 3b). A high-resolution transmission electron microscopy image of the embedded particles after microtome cutting and staining with phosphotungstic acid showed that the thickness of the PAA layer in the surface of the particles was 63 ± 11 nm (Figure 3c). Next, the fixing of heterostructured nanoporous particles into the channel was carried out by a cross-linking reaction between the nanoporous particles and oxygen-plasma-treated polydimethylsiloxane (PDMS) with glutaraldehyde serving as a cross-linker.30 As shown in Figure 3e,f and Figure S6, these heterostructured nanoporous particles could be fixed onto the bottom of a dialysate channel. Therefore, these PAA−PSDVB heterostructured nanoporous particles could be successfully fabricated by emulsion interfacial polymerization and subsequently be fixed into the microfluidic channel. Biomolecule Cleaning by the Bioinspired Device. To demonstrate the effectiveness of our bioinspired biomolecule cleaning device for the clearance of biomolecules spanning from small molecules to macromolecules, we chose three kinds

of molecules, including urea, creatinine, and lysozyme as model molecules. As shown in Figure 4a,b, both urea and creatinine molecules could be effectively cleaned after three cycles. The cleaning efficiency could reach 96.5 ± 0.7% for urea and 96.2 ± 3.3% for creatinine, respectively, indicating a high cleaning efficiency. It is worth noting that, compared to the single device with only a PAM porous membrane, no obvious promotion in cleaning efficiency of small molecules (urea and creatinine) was observed in our bioinspired biomolecule cleaning device due to weak interaction (for urea) or electrostatic repulsion (for creatinine) between negatively charged nanoporous particles and these small molecules (Figure S7). As expected, the cleaning efficiency of macromolecules (lysozyme) could be significantly enhanced by our bioinspired biomolecule cleaning device in comparison with the single device with only a PAM porous membrane. As shown in Figure 4c, in the first cycle, more than 40% of lysozyme was cleaned, which was about 2 times higher than the single device with only a PAM porous membrane. After three cycles, the cleaning efficiency of lysozyme by our bioinspired biomolecule cleaning device had increased 21% over the single device with only a PAM porous membrane, indicating that introducing heterostructured nanoporous particles into the dialysate channel could significantly facilitate the clearance of D

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Figure 4. Molecule clearance effectiveness and mechanism of the bioinspired biomolecule cleaning device. (a−c) Cleaning efficiency of urea, creatinine, and lysozyme by the single device with only a PAM porous membrane and our bioinspired biomolecule cleaning device. Compared to the single device with only a PAM porous membrane, our bioinspired biomolecule cleaning device could significantly enhance the clearance of macromolecules. (d) Schematic of molecule clearance by the single device with only a PAM porous membrane and our bioinspired biomolecule cleaning device. Compared to the single device with only a porous membrane, our bioinspired biomolecule cleaning device is more beneficial for the transport of molecules due to the adsorption (C0 − C1 < C0 − C2). (e, f) COMSOL numerical simulation of molecule transport by the single device with only a PAM porous membrane and our bioinspired biomolecule cleaning device. The color in the channel represents the concentration of the metabolic molecule. Our bioinspired biomolecule cleaning device could significantly reduce the concentration of molecules in the dialysate channel in comparison with the single device with only a PAM porous membrane. (g) Transport flux of molecules (lysozyme, with a diffusion coefficient of 1.1 × 10−10 m2/s). The lysozyme transport capacity of our bioinspired biomolecule cleaning device was much higher than that of the single device with only a PAM porous membrane. (h, i) Bright-field microscope and fluorescence microscope images of a heterostructured nanoporous particle that was exfoliated from the microchannel after performing FITC-lysozyme purification. During the process of purification, the heterostructured nanoporous particles could effectively adsorb FITC-lysozyme.

flux of metabolic molecules follows the general permeation equation31

macromolecules. We monitored the adsorption of lysozyme by heterostructured nanoporous particles in the dialysate channel by using fluorescent FITC-lysozyme macromolecules. The heterostructured nanoporous particles showed green fluorescence (Figure S8), suggesting that the FITC-lysozyme macromolecules were adsorbed by heterostructured nanoporous particles during the process of molecule cleaning. Moreover, after purifying FITC-lysozyme, these heterostructured nanoporous particles were exfoliated from the channel for bright-field microscope and fluorescence microscope observation. The results demonstrated that these FITClysozyme macromolecules could be effectively adsorbed onto/into the external/internal surface of the heterostructured nanoporous particles (Figure 4h,i). The transport of metabolic molecules through a porous membrane is due to the concentration gradient. The transport

Js =

DiK i (C0 − Ci) l

(1)

where Di is the diffusion coefficient of the metabolic molecules, Ki is the solubility constant, C0 is the initial concentration of molecules in the sample channel, and Ci is the concentration of molecules that diffused through the porous membrane to the underlying channel, l is thickness of the membrane. From eq 1, the diffusion flux of metabolic molecules mainly depends on the concentration difference between the sample channel and underlying channel. When a concentration difference existed, the molecules in the sample fluid would diffuse through the PAM porous membrane to the underlying fluid channel. After that, the negatively charged PAA−PSDVB heterostructured nanoporous particles could adsorb these E

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Figure 5. Effect of fabrication parameters of the bioinspired biomolecule cleaning device for the clearance of lysozyme. (a) Effect of flow rate on the clearance of lysozyme. The flow rate of blood is the same as that of the dialysate. (b) Effect of pore size of the PAM porous membrane on the clearance of lysozyme. (c) Effect of pore size of PAA−PSDVB heterostructured nanoporous particles on the clearance of lysozyme. (d) Effect of concentration of PAA−PSDVB heterostructured nanoporous particles on the clearance of lysozyme.

filtrated molecules (mainly those macromolecules in our work) by the electrostatic interaction and hydrophobic interaction,32 significantly decreasing the concentration of molecules in the underlying channel. In this case, compared to the single device with only a PAM porous membrane, the concentration difference between the sample fluid channel and underlying fluid channel in our bioinspired device would be continuously maintained at a high level due to C0 − C1 < C0 − C2 (where C0 is the initial concentration of molecules in the sample channel, C1 is the concentration of filtrated molecules in the underlying fluid channel from the single device with only a PAM porous membrane, and C2 is the concentration of filtrated molecules in the underlying fluid channel from our bioinspired device), as illustrated in Figure 4d. Thus, our bioinspired biomolecule cleaning device would be more beneficial for the transport of molecules than the single device with only a PAM porous membrane. These results demonstrated that the synergistical bioinspired design that combines a kidney-inspired porous membrane and natural sponge-inspired heterostructured nanoporous particles enables the highly efficient clearance of molecules spanning from small molecules to macromolecules. Flow Simulation of Heterostructured Nanoporous Particle Adsorption-Assisted Efficient Transport of Macromolecules in the Bioinspired Device. To better understand the heterostructured nanoporous particle adsorption-assisted efficient transport of molecules, we constructed a fluid flow simulation using commercial COMSOL software (Figure S9 and Figure S10). The parameters in the simulation were consistent with those in our experiments (the detailed information can be found in the Supporting Information). The serpentine channel was simplified to a straight one. The COMSOL numerical simulation results showed that our bioinspired biomolecule cleaning device is more efficient than the single device with only a PAM porous membrane in the clearance of molecules (Figure 4e,f). The transport flux of

macromolecules (lysozyme,33 with a diffusion coefficient of 1.1 × 10−10 m2/s) by our bioinspired biomolecule cleaning device was higher than that by the single device with only a PAM porous membrane (Figure 4g), which was consistent with our experimental results. The influence of flow rate, pore size of the PAM porous membrane, and the pore size and concentration of PAA− PSDVB heterostructured nanoporous particles on the clearance of lysozyme was investigated comprehensively. In this study, the flow rate of the upper sample fluid was the same as the underlying fluid. As shown in Figure 5a, superb lysozyme cleaning efficiency (about 70%) was accomplished at a flow rate of 8 mL h−1. In addition, the cleaning efficiency of lysozyme increased with increasing the pore size of the membrane and the pore size and concentration of PAA− PSDVB heterostructured nanoporous particles (Figure 5b−d). These results demonstrated that the efficient clearance of lysozyme could be achieved by controlling the flow rate, pore size of the nanoporous particles and membrane, and the concentration of heterostructured nanoporous particles in the bioinspired biomolecule cleaning device. Furthermore, to demonstrate the potential clinical applications, such as blood purification, the clearance capacity of the bioinspired biomolecule cleaning device for whole blood was tested under optimized parameter conditions. To determine the cleaning efficiency of the bioinspired biomolecule cleaning device in blood samples, three kinds of molecules, urea (4 × 10−2 mol/L), creatinine (4.5 × 10−4 mol/L), and β2microglobulin (2.86 × 10−5 mol/L), were spiked into whole blood. The results showed that the cleaning efficiency of urea, creatinine, and β2-microglobulin were 86%, 86%, and 65%, respectively, demonstrating a good future in clinical applications of our bioinspired biomolecule cleaning device. F

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plastic culture dish. Finally, a PAM porous membrane was sandwiched between the two PDMS chips before precisely aligning the two chips. After curing at 65 °C for 1 h, the integrated microfluidic device was obtained. Clearance of Urea, Creatinine, and Lysozyme by the Bioinspired Biomolecule Cleaning Device. The concentration of urea, creatinine, and lysozyme could be calculated by UV absorption based on their corresponding standard curves. The concentration of urea was recorded by a color reaction between dimethylaminobenzaldehyde (DMAB) and urea. According to the Ehrlich reaction, the reaction product of DMAB and urea has a maximum absorption peak at 406 nm. The concentration of creatinine was calculated by UV absorption at 234 nm. The concentration of lysozyme solution was calculated by UV absorption at 281 nm. The standard curve of urea detection was y = 2.3128x + 2.5669 (R2 = 0.9981). The standard curve of creatinine detection was y = 0.1264x + 0.0539 (R2 = 0.99721). The standard curve of lysozyme detection was y = 0.00516x + 0.03873 (R2 = 0.99968). The cleaning efficiency of urea, creatinine, and lysozyme was calculated as follows:

CONCLUSIONS We have demonstrated a bioinspired biomolecule cleaning device that synergistically combines a kidney-inspired porous membrane and natural sponge-inspired heterostructured nanoporous particles, exhibiting good function in highly efficient clearance of molecules spanning from small molecules to macromolecule. The bioinspired biomolecule cleaning device that integrates the capacities of the heterostructured nanoporous particle adsorption and porous membrane filtration can efficiently clean all kinds of molecules from simulant liquid and even whole blood, including small molecules (urea and creatinine) and macromolecules (lysozyme and β2-microglobulin), with high efficiency. We demonstrate that the amphiphilic PAA−PSDVB heterostructured nanoporous particles fixed onto the bottom of the microfluidic channel can particularly enhance the clearance of macromolecules during the process of cleaning, as indicated by experiment results and fluid simulation. Our bioinspired synergistic design that combines different functional materials with microfluidic technology may provide perspectives on organs-on-chips.

cleaning efficiency of molecules = (C0 − C t)/ C0 × 100% where Ct is the residual concentration of molecules in solution after clearance and C0 is the initial concentration of molecules. Clearance of Molecules in Whole Blood by Our Bioinspired Biomolecule Cleaning Device. Urea, creatinine, and β2-microglobulin were respectively introduced into sheep blood. Then, these blood samples were applied to the bioinspired biomolecule cleaning device for the clearance of molecules. After three cycles, the purified sheep blood was collected and subsequently tested by an automatic biochemistry analyzer (Beckman AU5800) from Peking University Third Hospital.

EXPERIMENTAL SECTION Synthesis of the PAA−PSDVB Heterostructured Nanoporous Particles. The PAA−PSDVB heterostructured nanoporous particles were fabricated by an emulsion interfacial polymerization method. First, 0.2 g of polystyrene (PS) particles with a diameter of about 3.5 μm was dispersed in 20 mL of aqueous solutions (containing 0.25% sodium dodecyl sulfate (SDS)). The dispersed PS particles were mixed with 10 mL of emulsion containing 0.1 mL of 1-chlorododecane at 40 °C for 20 h. After that, 10 mL of emulsion (0.25% w/v SDS) containing 0.5 mL of AA, 0.5 mL of St, 2 mL of DVB, and 40 mg of azodiisobutyronitrile was added into the above solution at 40 °C for 6 h. Subsequently, 5 mL of PVA aqueous solution was added into the aforementioned mixture, which was then treated with N2 to remove oxygen for 5 min. Finally, the polymerization was carried out at 70 °C for 14 h. The obtained heterostructured nanoporous particles were washed with water and ethanol three times. Fabrication of the Bioinspired Biomolecule Cleaning Device. The bioinspired biomolecule cleaning device was fabricated by two-step PDMS replication on a serpentine mask template of silicon substrate. In a typical fabrication, the serpentine mask template of silicon substrate was first treated with oxygen plasma and then with fluoroalkyl silane (FAS) modification. Subsequently, the PDMS and curing agent with a feed ratio of 8:1 were poured into the silicon wafer template and then cured at 80 °C for 2 h to form the mask template of PDMS. After that, the resulting PDMS template was modified with the FAS, after which PDMS/curing agent (feed ratio, 10:1) were poured into the above-mentioned PDMS template and then cured at 80 °C for 30 min. Finally, the microfluidic chip with a serpentine channel was fabricated after releasing the PDMS template. Fixing of PAA−PSDVB Porous Particles into a PDMS Channel. In a typical fixing process, the above-mentioned PDMS microfluidic chip with a serpentine channel was first treated with oxygen plasma for 10 min. Then, an aqueous solution of PAA− PSDVB heterostructured nanoporous particles containing 1% v/v glutaraldehyde was imported into the channel. After evaporating water at room temperature, the microfluidic chip was rinsed three times with water to remove non-cross-linked particles. Integration of the Bioinspired Biomolecule Cleaning Device. First, the above-mentioned PDMS chips with and without PAA−PSDVB heterostructured nanoporous particles were respectively punched with holes at the injection port of the microfluidic chip. Subsequently, an n-hexane solution with 1% v/v PDMS was spin coated on the surface of a plastic culture dish. Then, the abovementioned PDMS chips with and without PAA−PSDVB heterostructured nanoporous particles were dipped onto the surface of a

ASSOCIATED CONTENT S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsnano.9b03918. Additional figures (PDF) Supporting movie (MP4)

AUTHOR INFORMATION Corresponding Author

*E-mail: [email protected]. ORCID

Yongyang Song: 0000-0003-1737-2428 Jingxin Meng: 0000-0002-4160-9790 Zijian Zheng: 0000-0002-6653-7594 Xiaodong Chen: 0000-0002-3312-1664 Shutao Wang: 0000-0002-2559-5181 Author Contributions #

J.B.F., J.L., and Z.L. contributed equally to this work.

Notes

The authors declare no competing financial interest.

ACKNOWLEDGMENTS The authors thank the National Natural Science Foundation of China (21872158, 21425314, and 21875269), National Key R&D Program of China (2018YFC1105301), and National Program for Special Support of Eminent Professionals Youth Innovation Promotion Association CAS (2019028) for financial support. G

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DOI: 10.1021/acsnano.9b03918 ACS Nano XXXX, XXX, XXX−XXX