Article pubs.acs.org/cm
Thermal Regulation of Colloidal Materials Architecture through Orthogonal Functionalizable Patchy Particles Xiaolong Zheng,† Yufeng Wang,†,‡ Yu Wang,† David J. Pine,*,‡,§ and Marcus Weck*,† †
Molecular Design Institute and Department of Chemistry, New York University, New York, New York 10003, United States Center for Soft Matter Research and Department of Physics, New York University, New York, New York 10003, United States § Department of Chemical & Biomolecular Engineering, Polytechnic School of Engineering, New York University, Brooklyn, New York 11201, United States ‡
S Supporting Information *
ABSTRACT: This contribution presents a sol−gel based cluster encapsulation methodology to produce bifunctional patchy particles. The particles possess azide moieties on the surfaces of the patch and carboxylic acids on the shell. Two types of DNA with distinct terminal sequences are site-specifically conjugated to the particle patches or the shell employing two orthogonal coupling strategies: strainpromoted alkyne−azide cycloaddition and carbodiimide-mediated amidation. We can activate and deactivate assembly on the patches and/or the shell through thermal control, demonstrating reversible and stepwise self-assembly.
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INTRODUCTION Materials with complex microstructure can be obtained through the bottom-up assembly of colloidal building blocks. Colloids with valence or so-called colloidal atoms have drawn extensive attention recently due to their site-specific chemical activity and their potential in constructing higher order or low-coordination open structures1−6 and functional heterostructures.7 Examples include the formation of a colloidal Kagome lattice by tuning the hydrophobic interaction between the poles of triblock Janus particles8 and the fabrication of colloidal molecules from patchy particles site-specifically functionalized with DNA and using DNA hybridization as the driving force.9 These strategies exploit a single source of interaction to “glue” individual particles together. In the case of patchy particles, for example, only the patches have been functionalized with DNA. Assembly occurs only through patch−patch interaction in one step. Studies have shown that more complex or hierarchical architectures could be achieved with particles allowing for stepwise assembly processes. 10−13 The achievement of individual particles with selective regions of different stimuli response is a prerequisite for this process. Template-assisted asymmetric functionalization of particles has been reported and used for selectively controlled and stepwise assemblies, but the poor yields associated with these structures as well as the lack of tunable approaches to incorporate other ligands limit their applications.14−16 Another pathway is to introduce orthogonal functional groups spatially located on the particle surface; each type can be selectively modified and does not interfere with each other.17 While particles with multiple types of functional groups spatially distributed on colloid surface have been developed,18−20 none of them contain orthogonal recognition sites or have been used for self-assembly. © XXXX American Chemical Society
We rationalize that DNA functionalized colloids are excellent candidates to achieve the process due to the thermoreversibility and high specificity of DNA hybridization.21−25 By turning on and off multiple and specific interactions through controlling the temperature and DNA sequences, complex colloidal crystal structures or colloidal phase transitions have been explored recently.26−29 However, these studies focused only on spherical colloids with DNA distributed evenly over the particle surface. Here, we expand on these studies by synthesizing bifunctional patchy particles and asymmetrically functionalizing oligonucleotides onto their surface. We sitespecifically graft two kinds of DNA, differing in length and base pair sequence, resulting in full hybridization orthogonality to each other, onto the patch and the shell of the patchy particles. We can separately activate and/or deactivate the assembly of the patches or the shell using temperature (the melting temperatures of our two sets of DNA differ by 10.8 °C), thus demonstrating a reversible self-assembly process, controllable in two separate stages.
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MATERIALS AND METHODS
General Method. All chemical reagents were purchased from Sigma-Aldrich or Click Chemistry Tool and used as received unless otherwise indicated. Single-stranded oligonucleotides of different sequences were purchased from Integrated DNA Technologies (IDT). Styrene, methacrylic acid, and 3-chloro-2-hydroxypropyl methacrylate were allowed to pass through a column filled with inhibitor remover (Sigma-Aldrich) right before use. Scanning electron microscope (SEM) images were taken using a Merlin (Carl Zeiss) field-emission SEM. Fluorescent images were taken using a Leica SP5 confocal fluorescence microscope. Regular bright-field optical images Received: April 4, 2016 Revised: May 17, 2016
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the ability of aggregates to disperse upon heating.33 Then, the particles were washed with DI water to get rid of the extra DNA and EDC. Finally, the particles were dispersed into PBS containing Pluronic F127 (1% w/w) and used for further fluorescence and self-assembly experiments. Particle Self-Assembly. For the self-assembly studies, the particles of interest were combined, mixed, and transferred to a flat glass capillary tube (2 mm × 100 μm × 10 cm). The capillary tube was pretreated with oxygen plasma and exposed to hexamethyldisilazane vapor to make it hydrophobic to prevent DNA-coated colloids from sticking onto glass. Before loading colloidal particles, the hydrophobic tube is flushed with aqueous 1% F127 solution to coat the inner surface of the tube with the surfactant; the excess solution is removed by blowing with compressed air. After addition of the sample, the capillary tube was sealed onto a microscope glass slide using wax. The capillary tube temperature was controlled by using a homemade microscope thermal stage. For the assembly of AB, AB2, and AB3 types as well as the corresponding multifunctionalized colloidal molecules, TPM spheres of 1.0 μm and 540 nm in diameter were mixed with patchy particles. For the assembly of A2 type or polymers and the corresponding multifunctionalized colloidal structures, only 540 nm or 1.0 μm TPM spheres were used to bind with patchy particles, respectively. Flow Cytometry. We use flow cytometry to quantify the number of DNA strands functionalized per particle. Each of the DNA types is quantified separately. A portion of particles is divided into two aliquots. One aliquot is reacted with Cy5-labeled and DBCO-DNA that allows quantifying the DNA strands attached to the patches. The other aliquot is reacted with Cy5-labeled and amine terminated DNA allowing us to quantify the DNA on the shell. Cy5-labeled microspheres are used as cytometry standard (Quantum Cy5MESF, Bangs Laboratories Inc.). Laser 633 nm is used to excite the dye. Using the provided molecules of equivalent soluble fluorochromes (MESF), a calibration curve is constructed, on the basis of which the measured fluorescent intensity data for each of DNA-coated particle sample is converted to an approximate number of DNA grafted on each particle. We consider the curve valid if the correlation between fluorescence intensity and fluorochromes numbers is larger than 0.9998. For analysis, particle samples are dispersed in PBS containing Pluronic F127 (1% w/w). We then measure the fluorescence of the DNAcoated colloids (Cy5-labeled) using the same instrument under identical conditions. Comparison of the obtained value with calibration curve enables us to read out the number of DNA species per particle. We typically collect data from 300 000 particles and use the mean value to be statistically valid.
and videos were taken using a Nikon TE300 microscope. Flow cytometry experiments were carried out using a BD LSRII HTS cytometer. Some of the microscope images were digitally postprocessed to improve brightness and contrast. Synthesis of Chlorinated 3-(Trimethoxysilyl)propyl Methacrylate (TPM-Cl) Microspheres and Cluster Formation. Particles possessing chlorine anchors on the surface are fabricated by copolymerizing TPM with 3-chloro-2-hydroxypropyl methacrylate (CHPMA). In a typical synthesis, 200 μL of TPM is added into 20 mL of aqueous solution containing 1% ammonium hydroxide, and the reaction is allowed to stir at room temperature for 4 h. Then, 40 μL of CHPMA is added and allowed to stir for another 30 min before the introduction of 10 mL of Pluronic F108 aqueous solution (2% w/w). After 10 min, 20 mg of azobis(isobutyronitrile) (AIBN) is added to initiate the polymerization. The resulting particles are purified by repeated centrifugation/redispersion with DI water. The chlorinated particles were then used to prepare clusters using a modified emulsion evaporation method that was first reported by Manoharan et.al.30 Typically, the spheres are transferred into toluene (with 5% v/v of ethanol)31 and emulsified with 0.1% sodium dodecyl sulfate (SDS) aqueous solution. After the evaporation of toluene, clusters of different symmetries are obtained. Patchy Particles Fabrication. The chlorinated clusters were washed and dispersed in 0.01% SDS aqueous solution, and the concentration was adjusted to about 0.02% w/w. To 5 mL of this particle suspension was added 20 μL of aqueous ammonium hydroxide solution (29% w/w), followed by 80 μL of TPM monomer. After the reaction mixture was allowed to stir for 4 h at room temperature, TPM hydrolyzed and condensed onto the clusters, forming the shells as oil droplets. Then, 8 μL of methacrylic acid (10% v/v to TPM) in 500 μL dichloromethane was introduced, which diffuses into the TPM oil droplets. After 30 min before the evaporation of dichloromethane, 100 μL 1% SDS aqueous solution was added to make the final SDS concentration 0.03%. Then, 10 mg of AIBN was added, and the reaction mixture was allowed to stir for another 20 min before the temperature was raised to 80 °C. Thermal degradation of AIBN initiated the polymerization, generating patchy particles bearing two functional groups spatially located on the surface. Particle Functionalization. Single-stranded oligonucleotides with a sticky end are used in this study. Amine-modified DNAs are purchased directly from IDT, and dibenzyl cyclooctane (DBCO)modified DNAs were converted from amine-modified DNAs by reacting with DBCO-sulfo-NHS in phosphate buffered saline (PBS, 10 mM, pH = 7.4, 100 mM NaCl, same below).32 The DNAs are internally fluorescently labeled with Cy3 (emission maximum 564) or Cy5 (emission maximum 668). Complementary DNAs were used to study self-assembly, with the length of sticky end containing 6 or 11 bases. Palindrome DNA strands with 10 bases of sticky end were also used. Before grafting DNA onto the particle surfaces, the chlorine groups were converted to azide groups. Specifically, 100 mg of sodium azide and a catalytic amount of potassium iodine (KI) were added into 10 mL of patchy particle suspension (0.5% w/w) containing Pluronic F127 (0.5% w/w), and the mixture was heated at 70 °C for 12 h. Then, the particles were washed and stored in DI water. In a typical DNA grafting experiment, azide-functionalized patchy particles with a concentration of 0.1% w/w and 20 μL of DBCO-DNA (100 μM) were first dispersed in 400 μL of PBS containing Triton X-100 (0.1% w/w). Then, the reaction mixture was heated at 55 °C with stirring for 24 h. After the reaction, the particles were washed with DI water three times and stored for fluorescence experiment or further surface 1-ethyl-3-(3dimethylaminopropyl)carbodiimide (EDC) coupling. For EDC coupling, the previous particles were dispersed into 400 μL of 2-(Nmorpholino)ethanesulfonic acid (MES) buffer (pH = 4.5, 0.1 M). A 20 μL portion of amine-DNA (100 μM) and 0.1 mg of EDC were added into the particle suspension. The mixture was allowed to stir for 1 h before another portion of EDC (0.1 mg) was added. This readdition and mixing process was repeated three more times before quenching the reaction by adding 200 μL of 2% (w/w) Tween-20 MES buffer. This quench step is critical to enhance even surface DNA grafting and
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RESULTS AND DISCUSSION Our strategy is based on the installation of azides on the patches and carboxylic acids on the shell that can, respectively, undergo strain-promoted alkyne−azide cycloaddition (SPAAC)32,34,35 and carbodiimide-mediated amide formation,33,36 grafting different DNAs onto the targeted positions. To fabricate such bifunctional patchy particles, we used a modified version of our previously developed cluster encapsulation methodology (Figure 1a).37 Specifically, chlorine-functionalized spheres (TPM-Cl) of 1.0 μm in diameter were synthesized by copolymerizing 3-(trimethoxysilyl)propyl methacrylate (TPM) with 3-chloro-2-hydroxypropyl methacrylate (CHPMA). The resulting spheres were then assembled into clusters, adopting linear, triangular, tetrahedral, trigonal bipyramidal, and higher order symmetries using an emulsion evaporation method (Figure 1b). The relative distribution of each cluster population can be adjusted by changing the emulsification conditions. Then, we partially encapsulated the clusters with the TPM monomer and methacrylic acid (MAA), producing particles with chlorinated patches and a carboxylated shell (Figure 1c). We obtained a mixture of particles with B
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clusters. The patch sizes can be controlled by varying the amount of TPM added to encapsulate the clusters. Smaller patches were obtained by introducing more TPM monomer (Figure S1). We note that this is not possible using previously reported systems where a different material (poly(styrene)) and particle synthesis mechanisms were used.9 The use of TPM as material here is the key to the synthesis of patchy particles with distinct surfaces possessing orthogonal functional groups. When TPM clusters are encapsulated, the shell forms by nucleating TPM prepolymers on the clusters. The prepolymer is highly viscous, preventing the MAA monomer introduced in the shell from diffusing to the patches. The fact that TPM clusters are densely cross-linked also limits the diffusion and migration of the MAA. After successful fabrication of the patchy particles containing two distinct functional groups, we evaluated their orthogonality in surface modification. We converted the chlorine moieties to azides using sodium azide. The azide groups along the patches were coupled to dibenzo-cyclooctyne-modified DNA (DBCODNA) while the carboxylic acid groups along the shell were reacted with amine-modified DNA (NH2-DNA) (Figure 2a). Fluorescently labeled single-stranded DNA (ssDNA) was used to visualize the orthogonal functionalization strategy using confocal microscopy. The DBCO-DNA sequence containing an 11-base sticky end (B11) is labeled with Cy5 (red) while the NH2-DNA is labeled with Cy3 (green) and has a 6-base sticky end (B6). Figure 2b shows that the patches, after SPAAC, fluoresce red. No red fluorescence is observed on the shell demonstrating site-selective functionalization. After SPAAC and carbodiimide-mediated coupling (Figure 2c, Figure S2), dual fluorescence spatially located on patches and shell is observed indicating that the azides and carboxylic acids are functionalized independently. In contrast to the noncovalent functionalization scheme (streptavidin−biotin)9 we used previously to functionalize DNA on colloids, both SPAAC and EDC conjugation used in
Figure 1. Bifunctional patchy particle fabrication. (a) Schematic representation of the preparation of patchy particles: a two-patch particle is shown as an example. (b−d) Electron micrographs of (b) colloidal clusters, (c) patchy particles, (d) purified two-patch particles (left) and three-patch particles (right). Scale bars, 1 μm.
different numbers of patches, adopting spherical, linear, triangular, tetrahedral, and trigonal bipyramidal symmetries. They were separated by density gradient centrifugation to obtain patchy particles of a single symmetry (Figure 1d). Particles with the same number of patches have uniform patch sizes and shapes. The yield and relative distribution of each patchy particle population remained the same as for the
Figure 2. Selective surface functionalization and characterization of particles. (a) Schematic representation demonstrating the orthogonal functionalization strategy. (b and c) Confocal fluorescent images of patchy particles, (b) after coupling with Cy5-labeled DNA, and (c) with Cy5and Cy3-labeled DNAs. Scale bars, 1 μm. C
DOI: 10.1021/acs.chemmater.6b01313 Chem. Mater. XXXX, XXX, XXX−XXX
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Chemistry of Materials this study result in covalent DNA attachment, which are robust enough to survive additional functionalization conditions. We used flow cytometry to quantify the number of DNA strands per particle by comparing them to a Cy5-labeled microsphere standards (Quantum Cy5MESF, Bangs Laboratories Inc.) (See Supporting Information for details.) The areal density of the DNA on the patches is approximately one strand per 60 nm2, equivalent to 52 000 DNA per 1.0 μm spherical particle. The areal density of the DNA on the shell is approximately one strand per 245 nm2, equivalent to 12 800 DNA per 1.0 μm spherical particle. We investigated the assembly process using two types of TPM spheres that selectively bind to either the patches or the shell. We utilized large spheres (1.0 μm, referred to as TPM1000) functionalized with D11 DNA strands (complementary to B11) and small spheres (540 nm, referred to as TPM540) functionalized with D6 DNA strands (complementary to B6). The electron micrographs of TPM1000 and TPM540 are shown in Figure S3. The DNA hybridization of B11/D11 on the patches has a higher melting temperature (45.0 °C) than B6/D6 on the shell (34.2 °C) resulting in a predesigned stepwise assembly/melting behavior for the patchy particles, as illustrated in Figure 3 and will be discussed below.
Figure 4. Stepwise self-assembly of patchy particles. (a−e) First stage assembly (left) and second stage assembly (right). Bright-field micrographs showing one-patch (a), two-patch (b), and three-patch (c) particles sequentially binding to two other spheres. (d) Coassembly of one-patch particles and TPM540 spheres. (e) Co-assembly of two-patch particles and TPM1000 spheres. Scale bars, 1 μm.
disassembly in two separate stages. Here, in order to obtain significantly different melting temperatures for the patch and the shell, we grafted DNA with shorter sticky ends by EDC coupling, which, along with the lower density of DNA, led to a lower melting temperature for the shell. DNA with longer sticky ends attached using SPAAC, which yields higher density DNA leading to a higher melting temperature for the patches. In principle, we can make the system either stepwise or simultaneous at will by grafting DNA strands with different melting temperatures or the same one, respectively. Here, we predesigned the system to allow multiple steps, which not only helps us to distinguish the intermediate structures, but may also facilitate the formation of hierarchical assemblies proposed and simulated in the literature where one structure is required before higher order structures can form.40,41 We can control the difference in melting temperature between patches and shell easily by adjusting the areal density of sticky-ended DNA. Additional sets of particles were prepared wherein the particles were fully functionalized with DNA, yet only a fraction of the DNA had sticky ends.32,38 The melting temperature decreases when the fraction of DNA prepared with sticky ends is decreased demonstrating the effect of hybridization density on the melting behavior (Table S1). The final assembled structure depends on the particle concentrations. At a high concentration of patchy particles, a sphere can bind to two patchy particles since a spherical particle does not have bond directionality. This leads to cross-linked aggregates (Figure S4). Decreasing the concentration of patchy particle suppresses such cross-linking. To form the assembly
Figure 3. Melting curve of patchy particles with two different spheres showing the singlet fraction of patchy particles. A two-patch particle is shown as an example.
When the temperature is well above 45.0 °C, all the particles stay dispersed (Figure 3). At temperatures above 36.0 °C and below 44.0 °C, only TPM1000 particles selectively bind to the patches forming AB, AB2, and AB3 type colloidal molecules made from one-, two-, and three-patch particles (Figure 3 and 4a,b,c, left). When decreasing the temperature below 36.0 °C, TPM540 particles interact with the shell while the TPM1000 is still bound to the patches, resulting in multifunctionalized colloidal molecules (Figure 3 and 4a,b,c, right). The selfassembly results confirm that two types of DNA are spatially immobilized on the surface and orthogonal to each other. With the temperature increasing gradually, the TPM540 first disassembles, followed by TPM1000. The process of particles binding to the patches is fully reversible upon repeated heating and cooling cycles (see Supporting Information Video 1 and Supporting Information). As shown in Figure 3, the melting (or assembling) processes take place in a relative narrow temperature window and with distinct melting temperatures for the patches and the shell. While many factors determine the melting temperature of DNA-coated particles,32,38,39 including particle size, curvature, and DNA grafting density, choosing DNA sticky ends with appropriate different lengths allows for the control of assembly/ D
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of the National Science Foundation under Award Number DMR-0923251 for the purchase of a Zeiss field-emission SEM.
structures shown in Figure 4, we typically keep the total particle concentration to be approximately 0.05% (w/w) with a ratio of TPM1000:TPM540:patchy particle = 3:4:1. We also investigated the use of self-complementary palindrome strands to assemble one-patch and two-patch particles. Specifically, palindrome strands of 10-base sticky ends (P10) were attached to the patches, and complementary strands of B6 sticky ends were immobilized on the shell. The patchy particles were mixed with TPM 540 or TPM 1000 functionalized with D6 DNA strands. Colloidal dumbbells of A2-type colloidal molecules and colloidal polymers are yielded from one- and two-patch particles, assembled at a higher temperature (Figure 4d,e, left). The TPM540 or TPM1000 spheres coassemble to the colloidal dumbbell or polymer and interact only with the shell when decreasing the temperature, forming multifunctionalized colloidal A2-type molecules and polymers (Figure 4d,e, right, and Figure S5).
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(1) Zhang, Z.; Glotzer, S. C. Self-Assembly of Patchy Particles. Nano Lett. 2004, 4, 1407−1413. (2) Glotzer, S. C.; Solomon, M. J. Anisotropy of Building Blocks and Their Assembly into Complex Structures. Nat. Mater. 2007, 6, 557− 562. (3) Zhang, Z.; Keys, A. S.; Chen, T.; Glotzer, S. C. Self-assembly of Patchy Particles into Diamond Structures through Molecular Mimicry. Langmuir 2005, 21, 11547−11551. (4) Chen, Q.; Whitmer, J. K.; Jiang, S.; Bae, S. C.; Luijten, E.; Granick, S. Supracolloidal Reaction Kinetics of Janus Spheres. Science 2011, 331, 199−202. (5) Rocklin, D. Z.; Mao, X. Self-Assembly of Three-Dimensional Open Structures Using Patchy Colloidal Particles. Soft Matter 2014, 10, 7569−7576. (6) Chapela, G. A.; Guzmán, O.; Martínez-González, J. A.; DíazLeyva, P.; Quintana-H, J. Self-Assembly of Kagome Lattices, Entangled Webs and Linear Fibers with Vibrating Patchy Particles in Two Dimensions. Soft Matter 2014, 10, 9167−9176. (7) Guo, J.; Chiou, Y.; Liang, W.; Liu, H.; Chen, Y.; Kuo, W.; Tsai, C.; Tsai, K.; Kuo, H.; Hsieh, W.; Juang, J.; Hsu, Y.; Lin, H.; Chen, C.; Liao, X.; Shi, B.; Chu, Y. Complex Oxide−Noble Metal Conjugated Nanoparticles. Adv. Mater. 2013, 25, 2040−2044. (8) Chen, Q.; Bae, S. C.; Granick, S. Directed Self-Assembly of a Colloidal Kagome Lattice. Nature 2011, 469, 381−384. (9) Wang, Y.; Wang, Y.; Breed, D. R.; Manoharan, V. N.; Feng, L.; Hollingsworth, A. D.; Weck, M.; Pine, D. J. Colloids with Valence and Specific Directional Bonding. Nature 2012, 491, 51−56. (10) Chen, Q.; Bae, S. C.; Granick, S. Staged Self-Assembly of Colloidal Metastructures. J. Am. Chem. Soc. 2012, 134, 11080−11083. (11) Onoe, H.; Matsumoto, K.; Shimoyama, I. Three-Dimensional Sequential Self-Assembly of Microscale Objects. Small 2007, 3, 1383− 1389. (12) Zhang, R.; Dempster, J. M.; Olvera de la Cruz, M. SelfReplication in Colloids with Asymmetric Interactions. Soft Matter 2014, 10, 1315−1319. (13) Groschel, A. H.; Walther, A.; Lobling, T. I.; Schacher, F. H.; Schmalz, H.; Muller, A. H. E. Guided Hierarchical Co-Assembly of Soft Patchy Nanoparticles. Nature 2013, 503, 247−251. (14) Xu, X.; Rosi, N. L.; Wang, Y.; Huo, F.; Mirkin, C. A. Asymmetric Functionalization of Gold Nanoparticles with Oligonucleotides. J. Am. Chem. Soc. 2006, 128, 9286−9287. (15) Huo, F.; Lytton-Jean, A. K. R.; Mirkin, C. A. Asymmetric Functionalization of Nanoparticles Based on Thermally Addressable DNA Interconnects. Adv. Mater. 2006, 18, 2304−2306. (16) Rycenga, M.; McLellan, J. M.; Xia, Y. Controlling the Assembly of Silver Nanocubes through Selective Functionalization of Their Faces. Adv. Mater. 2008, 20, 2416−2420. (17) We define orthogonal functionalities and interactions as noninterfering and individually addressable. (18) Kaufmann, T.; Wendeln, C.; Gokmen, M. T.; Rinnen, S.; Becker, M. M.; Arlinghaus, H. F.; Du Prez, F.; Ravoo, B. J. Chemically Orthogonal Trifunctional Janus Beads by Photochemical “Sandwich” Microcontact Printing. Chem. Commun. 2013, 49, 63−65. (19) Rahmani, S.; Saha, S.; Durmaz, H.; Donini, A.; Misra, A. C.; Yoon, J.; Lahann, J. Chemically Orthogonal Three-Patch Microparticles. Angew. Chem., Int. Ed. 2014, 53, 2332−2338. (20) Zhang, S.; Li, Z.; Samarajeewa, S.; Sun, G.; Yang, C.; Wooley, K. L. Orthogonally Dual-Clickable Janus Nanoparticles via a Cyclic Templating Strategy. J. Am. Chem. Soc. 2011, 133, 11046−11049. (21) Mirkin, C. A.; Letsinger, R. L.; Mucic, R. C.; Storhoff, J. J. A DNA-Based Method for Rationally Assembling Nanoparticles into Macroscopic Materials. Nature 1996, 382, 607−609. (22) Alivisatos, A. P.; Johnsson, K. P.; Peng, X. G.; Wilson, T. E.; Loweth, C. J.; Bruchez, M. P.; Schultz, P. G. Organization of ’Nanocrystal Molecules’ Using DNA. Nature 1996, 382, 609−611.
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CONCLUSION In conclusion, we have demonstrated a stepwise colloidal assembly scheme tuned by temperature, made possible by exploring the orthogonality in particle synthesis, functionalization, and DNA sequence selection. Bifunctional patchy particles with a variety of symmetries were fabricated, leading to an enriched spectrum of building blocks for colloidal self-assembly. The new particle system, featuring predetermined sequential self-assembly capacities, offers a promising route toward colloidal assemblies of structural and functional complexity, such as self-replicating colloids.40,41 One can also imagine exploiting the functionalization of the patchy particle shell to embed spheres in the void of an open lattice structure, such as a diamond, in order to stabilize such crystal structures against collapse.
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ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.chemmater.6b01313. Details for supplementary figures (PDF) Two-patch particles assembling and disassembling with TPM1000 and TPM540 with temperature cycling (AVI)
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REFERENCES
AUTHOR INFORMATION
Corresponding Authors
*E-mail:
[email protected]. *E-mail:
[email protected]. Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS This work was supported in part by the Department of Energy under Grant Award No. DE-SC0007991 (X.Z. and M.W.) and the U.S. Army Research Office under Grant Award No. W911NF-10-1-0518 (Yufeng Wang and D.J.P.). This work was supported partially by the Materials Research Science and Engineering Center (MRSEC) program of the National Science Foundation under Award Number DMR-1420073 (Yu Wang). X.Z. also acknowledges the Margaret and Herman Sokol Doctoral Fellowship. We thank Dr. Elizabeth Elacqua for discussions. We acknowledge support from the MRI program E
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