This research was supported by National Science Foundation (CCF 1814797) and University of Missouri Research Board, Material Research Center, and the College of Arts and Science at Missouri University of Science and Technology

1 . Preparation of Reagents
CAUTION: Please read and understand all relevant material safety data sheets (MSDS) before use. Some of the chemicals are toxic and volatile. Please follow special handling procedures and storage requirements. During the experimental procedure, use personal protective equipment, such as gloves, safety glasses, and a lab coat to avoid potential hazards.
<ol>
	<li>Preparation of Tris-HCl buffer
	<ol>
		<li>Dissolve 30.29 g of Tris powder in 100 mL of deionized H<sub...

<ol>
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M., Miller, W. M., Messersmith, P. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mussel-inspired+surface+chemistry+for+multifunctional+coatings.">Mussel-inspired surface chemistry for multifunctional coatings.</a> Science. 318 (5849), 426-430 (2007).</li><li>Wang, C., Zhou, J., Wang, P., He, W., Duan, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Robust+Nanoparticle-DNA+Conjugates+Based+on+Mussel-Inspired+Polydopamine+Coating+for+Cell+Imaging+and+Tailored+Self-Assembly.">Robust Nanoparticle-DNA Conjugates Based on Mussel-Inspired Polydopamine Coating for Cell Imaging and Tailored Self-Assembly.</a> Bioconjugate Chemistry. 27 (3), 815-823 (2016).</li><li>Liu, R., Guo, Y., Odusote, G., Qu, F., Priestley, R. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Core-shell+Fe3O4+polydopamine+nanoparticles+serve+multipurpose+as+drug+carrier,+catalyst+support+and+carbon+adsorbent.">Core-shell Fe3O4 polydopamine nanoparticles serve multipurpose as drug carrier, catalyst support and carbon adsorbent.</a> ACS Applied Materials and Interfaces. 5 (18), 9167-9171 (2013).</li><li>Liu, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dopamine+as+a+Carbon+Source:+The+Controlled+Synthesis+of+Hollow+Carbon+Spheres+and+Yolk-Structured+Carbon+Nanocomposites.">Dopamine as a Carbon Source: The Controlled Synthesis of Hollow Carbon Spheres and Yolk-Structured Carbon Nanocomposites.</a> Angewandte Chemie International Edition. 50 (30), 6799-6802 (2011).</li><li>Zeng, Y., Liu, W., Wang, Z., Singamaneni, S., Wang, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Multifunctional+surface+modification+of+nanodiamonds+based+on+dopamine+polymerization.">Multifunctional surface modification of nanodiamonds based on dopamine polymerization.</a> Langmuir. 34 (13), 4036-4042 (2018).</li><li>Qin, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dopamine@Nanodiamond+as+novel+reinforcing+nanofillers+for+polyimide+with+enhanced+thermal,+mechanical+and+wear+resistance+performance.">Dopamine@Nanodiamond as novel reinforcing nanofillers for polyimide with enhanced thermal, mechanical and wear resistance performance.</a> RSC Advances. 8 (7), 3694-3704 (2018).</li><li>Barras, A., Lyskawa, J., Szunerits, S., Woisel, P., Boukherroub, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Direct+functionalization+of+nanodiamond+particles+using+dopamine+derivatives.">Direct functionalization of nanodiamond particles using dopamine derivatives.</a> Langmuir. 27 (20), 12451-12557 (2011).</li><li>Khanal, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Toward+Multifunctional+"Clickable"+Diamond+Nanoparticles.">Toward Multifunctional "Clickable" Diamond Nanoparticles.</a> Langmuir. 31 (13), 3926-3933 (2015).</li><li>Rad, M. H., Zamanian, A., Hadavi, S. M. M., Khanlarkhani, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Two-Stage+Kinetics+Model+for+Polydopamine+Layer+Growth.+A+Two-Stage+Kinetics+Model+for+Polydopamine+Layer+Growth.">A Two-Stage Kinetics Model for Polydopamine Layer Growth. A Two-Stage Kinetics Model for Polydopamine Layer Growth.</a> Macromolecular Chemistry and Physics. , 1700505 (2018).</li><li>Ball, V., Frari, D. D., Toniazzo, V., Ruch, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Kinetics+of+polydopamine+film+deposition+as+a+function+of+pH+and+dopamine+concentration:+Insights+in+the+polydopamine+deposition+mechanism.">Kinetics of polydopamine film deposition as a function of pH and dopamine concentration: Insights in the polydopamine deposition mechanism.</a> Journal of Colloid and Interface Science. 386 (1), 366-372 (2012).</li><li>Liu, Y., Ai, K., Lu, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Polydopamine+and+its+derivative+materials:+synthesis+and+promising+applications+in+energy,+environmental,+and+biomedical+fields.">Polydopamine and its derivative materials: synthesis and promising applications in energy, environmental, and biomedical fields.</a> Chemical Reviews. 114 (9), 5057-5115 (2014).</li><li>Hu, J., Wu, S., Cao, Q., Zhang, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synthesis+of+core-shell+structured+alumina/Cu+microspheres+using+activation+by+silver+nanoparticles+deposited+on+polydopamine-coated+surfaces.">Synthesis of core-shell structured alumina/Cu microspheres using activation by silver nanoparticles deposited on polydopamine-coated surfaces.</a> RSC Advances. 6 (85), 81767-81773 (2016).</li><li>Orishchin, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid+Deposition+of+Uniform+Polydopamine+Coatings+on+Nanoparticle+Surfaces+with+Controllable+Thickness.">Rapid Deposition of Uniform Polydopamine Coatings on Nanoparticle Surfaces with Controllable Thickness.</a> Langmuir. 33, 6046-6053 (2017).</li><li>Gonza&#769;lez, A. 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This article provides a detailed protocol for the surface functionalization of NDs with self-polymerized DA coating, and the reduction of Ag[(NH3)2]+ to AgNPs on PDA layers (Figure 3). The strategy is capable of producing various thicknesses of PDA layers by simply changing the concentration of DA. The size of the AgNPs can also be controlled by altering the original concentration of metal ion solution. The TEM image in Figure 1<...

Nanodiamonds (NDs), a novel carbon-based material, have attracted considerable attention in recent years for use in various applications1,2. For instance, the high surface areas of NDs provide excellent catalyst support for metal nanoparticles (NPs) because of their super-chemical stability and thermal conductivity3. Furthermore, NDs play significant roles in bio-imaging, bio-sensing, and drug delivery due to their outstanding biocompatibility and nontoxicity4,5.
To efficiently extend their capabilities, it is valuable to conjugate functional species on the surfaces of NDs, such as proteins, nucleic acids, and nanoparticles6. Although a variety of functional groups (e.g., hydroxyl, carboxyl, lactone, etc.) are created on the surfaces of NDs during their purification, the conjugation yields of the functional groups are still very low because of the low density of each active chemical group7. This results in unstable NDs, which tend to aggregate, limiting further application8.
Currently, the most common methods used to functionalize NDs, are covalent conjugation by using copper-free click chemistry9, covalent linkage of peptide nucleic acids (PNA)10, and self-assembled DNA11. The non-covalent wrapping of NDs has also been proposed, including carbohydrate-modified BSA4, and HSA12coating. However, because these methods are time consuming and inefficient, it is desirable that a simple and generally applicable method can be developed to modify the surfaces of NDs.
Dopamine (DA)13, known as a natural neurotransmitter in the brain, was widely used for adhering and functionalizing nanoparticles, such as gold nanoparticles (AuNPs)14, Fe2O315, and SiO216. Self-polymerized PDA layers enrich amino and phenolic groups, which can be further utilized to directly reduce metal nanoparticles or to easily immobilize thiol/amine-containing biomolecules on an aqueous solution. This simple approach was recently applied to functionalize NDs by Qin et al. and our laboratory17,18, although DA derivatives were employed to modify NDs via Click Chemistry in earlier studies19,20.
Here, we describe a simple PDA-based surface modification method that efficiently functionalizes NDs. By varying the concentration of DA, we can control the thickness of a PDA layer from a few nanometers to tens of nanometers. In addition, the metal nanoparticles are directly reduced and stabilized on the PDA surface without the need for additional toxic reduction agents. The sizes of the silver nanoparticles depend on the initial concentrations of Ag[(NH3)2]+. This method allows the well-controlled deposition of PDA on the surfaces of NDs and the synthesis of ND conjugated AgNPs, which dramatically extends the functionality of NDs as excellent nano-platforms of catalyst supports, bio-imaging, and bio-sensors.

<table border="0" cellpadding="0" cellspacing="0" style="width:839px;" width="838">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Nanodiamond</td>
			<td style="width:121px;">FND Biotech, Inc.</td>
			<td style="width:136px;">brFND-100</td>
			<td style="width:365px;">dispersed in water, and used without further purification</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Dopamine hydrochloride</td>
			<td style="width:121px;">Sigma</td>
			<td style="width:136px;">H8502-25G</td>
			<td>prepare freshly</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Silver Nitrate</td>
			<td style="width:121px;">Fisher</td>
			<td style="width:136px;">S181-25</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Ammonium Hydroxide</td>
			<td style="width:121px;">Fisher</td>
			<td style="width:136px;">A669S-500</td>
			<td>highly toxic</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Tris Hydrochloride</td>
			<td style="width:121px;">Fisher</td>
			<td style="width:136px;">BP153-500</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">TEM grid carbon film</td>
			<td style="width:121px;">Ted Pella</td>
			<td style="width:136px;">01843-F</td>
			<td>300 mesh copper</td>
		</tr>
	</tbody>
</table>

bio-inspired polydopamine surface modification of nanodiamonds and its reduction of silver nanoparticles

Surface functionalization of nanodiamonds (NDs) is still challenging due to the diversity of functional groups on the ND surfaces. Here, we demonstrate a simple protocol for the multifunctional surface modification of NDs by using mussel-inspired polydopamine (PDA) coating. In addition, the functional layer of PDA on NDs could serve as a reducing agent to synthesize and stabilize metal nanoparticles. Dopamine (DA) can self-polymerize and spontaneously form PDA layers on ND surfaces if the NDs and dopamine are simply mixed together. The thickness of a PDA layer is controlled by varying the concentration of DA. A typical result shows that a thickness of ~5 to ~15 nm of the PDA layer can be reached by adding 50 to 100 &#181;g/mL of DA to 100 nm ND suspensions. Furthermore, the PDA-NDs are used as a substrate to reduce metal ions, such as Ag[(NH3)2]+, to silver nanoparticles (AgNPs). The sizes of the AgNPs rely on the initial concentrations of Ag[(NH3)2]+. Along with an increase in the concentration of Ag[(NH3)2]+, the number of NPs increases, as well as the diameters of the NPs. In summary, this study not only presents a facile method for modifying the surfaces of NDs with PDA, but also demonstrates the enhanced functionality of NDs by anchoring various species of interest (such as AgNPs) for advanced applications.

The formation of PDA layers on ND surfaces were analyzed by TEM (Figure 1). Different thicknesses of PDA layers were observed as higher concentrations of DA led to thicker PDA layers. In addition, after an encapsulating reaction, the color of the NDs solution changed from colorless to dark, while the higher the initial concentration of DA was, the darker the solution became.
Fig...

Watch this Scientific Journal Video about Bio-inspired Polydopamine Surface Modification of Nanodiamonds and Its Reduction of Silver Nanoparticles at JoVE.com

Bio-inspired Polydopamine Surface Modification of Nanodiamonds and Its Reduction of Silver Nanoparticles

A facile protocol is presented to functionalize the surfaces of nanodiamonds with polydopamine.

Surface functionalization of nanodiamonds (NDs) is still challenging due to the diversity of functional groups on the ND surfaces. Here, we demonstrate a ...

This method can help answer key questions about effective surface functionalization of nanodiamond, which have broad applications in material science and biomedicine. This method can be used for nanodiamonds. It can also be applied for other materials, such as metal nanoparticles, magnetic nanoparticles, or surfaces that need an active biopolymer coating.In this method, nanodiamonds are funtionalized with a coating of polydopamine, a universal adhesive. The thickness of the PDA layer is well controlled by varying the concentration of dopamine. To begin, dissolve 30.29 grams of tris HCl powder in 100 microliters of deionized water.Transfer the solution to a 250 milliliter volumetric flask. Fill the flask to the line with deionized water, and mix it to obtain a one molar tris HCl buffer. From this stock solution, prepare 20 milliliters of 0.1 molar tris HCl buffer by serial dilution.While monitoring the buffer with a pH meter, adjust the pH to 8.5 using one molar hydrochloric acid. Next, dilute 0.02 milliliters of a one milligram per milliliter suspension of 100 nanometer monocrystalline nanodiamonds to one milliliter with the pH 8.5 tris buffer. Stir the mixture for 10 minutes to obtain a 0.02 milligram per milliliter nanodiamond suspension.Then, dissolve 20 milligrams of dopamine hydrochloride in two milliliters of pH 8.5 tris buffer, by vortexing for 30 seconds to obtain a buffered 10 milligram per milliliter dopamine hydrochloride solution. Add five, 7.5, or 10 microliters of the freshly prepared dopamine solution to the nanodiamond solution, depending on whether a final dopamine hydrochloride concentration of 50, 75, or 100 milligram per milliliter is desired. After adjusting the reaction volume, vigorously stir the mixture at 25 degrees Celsius for 12 hours in the dark.Then, transfer the suspension of polydopamine-coated nanodiamonds to a 1.5 milliliter centrifuge tube, and centrifuge it at 16, 000 g for two hours. Remove the supernatant and wash the nanodiamonds three times with one milliliter portions of deionized water at 16, 000 g for one hour each time. Then add 200 microliters of deionized water to the washed solids, and sonicate the mixture for 30 seconds to redisperse the polydopamine-coated nanodiamonds.Serially dilute 40 microliters of a suspension of polydopamine-coated nanodiamonds twice with deionized water. Then, dissolve 100 milligrams of silver nitrate in 10 milliliters of deionized water by vortexing. In a fume hood, add one molar aqueous ammonia to the silver nitrate solution, dropwise, until a yellow precipitate forms, periodically shaking the solution.Continue adding ammonia until the precipitate disappears to obtain a solution of diamine silver hydroxide. Immediately add either 4.3 or 6.4 microliters of the diamine silver solution to 40 microliters of the diluted nanodiamond dispersion, for a final concentration of 0.4 or 0.6 milligrams per milliliter respectively. After this, adjust the volume to 100 microliters with deionized water.Sonicate the mixture for 10 minutes. Then, centrifuge the dispersion for 15 minutes at 16, 000 g to remove free silver ions. Discard the supernatant and wash the silver nanoparticle-decorated polydopamine-coated nanodiamonds by centrifuging them three times in 100 microliter portions of deionized water at 16, 000 g for five minutes each time.Add 100 microliters of deionized water to the silver nanoparticle-decorated nanodiamonds and redisperse them by sonication for 30 seconds. Characterize the nanodiamonds with UV-Vis spectroscopy scanning from 250 to 550 nanometers. Next, deposit five microliters of the silver nanoparticle-decorated nanodiamonds on plasma-cleaned carbon-coated copper grids, and let them sit for three minutes.Then, wick away excess solution with filter paper. Wash each grid three times by applying a drop of deionized water, letting it sit for 15 seconds, and then wicking it away with filter paper. Let the grids air dry before visualizing the samples with transmission electron microscopy.The uncoated nanodiamonds tended to form microclusters and aggregates, while polydopamine-coated nanodiamonds formed good dispersions. Higher dopamine concentrations resulted in the formation of thicker polydopamine layers in the nanodiamond surfaces. The uncoated nanodiamond dispersion was clear and colorless.Upon coating the nanodiamonds with a five nanometer thick polydopamine layer, the dispersion appeared cloudy and brown. The dispersion appearance became progressively darker with thicker polydopamine coatings. The reduction of diamine silver on nanodiamonds coated with a 15 nanometer thick polydopamine layer was most successful when the diamine silver hydroxide concentration was 0.4 to 0.6 milligrams per milliliter.The nanodiamonds formed at lower concentrations were too small to be studied effectively. The maximum absorbance values indicated that the nanoparticles formed from the 0.4 to 0.6 milligram per milliliter solutions had diameters of roughly 20 and 30 nanometers respectively. TEM showed that the silver nanoparticles generated from the 0.4 milligram per milliliter diamine silver solution were about 24 nanometers wide, while the nanoparticles generated from the 0.6 milligram per milliliter solution were about 28 nanometers wide.The number of nanoparticles on the nanodiamond surfaces was also greater at the higher diamine silver concentration. After using this procedure, well-dispersed nanodiamonds with a controllable PDA thickness were formed. This technique paves the way for researchers to explore nanodiamond applications for catalyst, biosensors, and nanocarriers.Without using any additional reducing agent, the PDA-assisted materialization process can induce the formation of silver nanoparticles upon the reduction of metal precursors and immobilize them on the PDA-coated surface. In addition, the PDA layers contain open functional groups which can be further utilized to conjugate serial and amine-modified biomolecules.

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JoVE Journal

Chemistry

8.0K visualizações.  Missouri University of Science and Technology. Este método pode ajudar a responder a perguntas-chave sobre a efetiva funcionalização superficial do nanodiamanhã, que têm amplas aplicações em ciência material e biomedicina. Este método pode ser usado para nanodiamantes. Também pode ser aplicado para outros materiais, como nanopartículas metálicas, nanopartículas magnéticas ou superfícies que precisam de um revestimento biopolímero ativo.Neste método, os nanodiamantes são funtionalizados com um revestimento de polid...