A biocompatible synthesis of gold nanoparticles by Tris(hydroxymethyl)aminomethane
© Chen et al.; licensee Springer. 2014
Received: 25 November 2013
Accepted: 16 April 2014
Published: 7 May 2014
Gold nanoparticles' novel properties are widely realized in catalysis, plasmonics, electronics, and biomedical applications. For biomedical application, one challenge is to find a non-toxic chemical and/or physical method of functionalizing gold nanoparticles with biomolecular compounds that can promote efficient binding, clearance, and biocompatibility and to assess their safety to other biological systems and their long-term effects on human health and reproduction. In the present study, we describe a new method by using Tris(hydroxymethyl)aminomethane (Tris), a widely used buffer solvent of nucleic acid and proteins, as the reducing agent for synthesizing gold nanoparticles by one step. It is found that Tris carries out the reduction reactions in relatively mild conditions for biomacromolecules. Particularly, it can be used to modify the DNA during the process of preparation of gold nanoparticles. The morphology and size distribution of gold nanoparticles are consistent and were confirmed by many different approaches including dynamic light scattering (DLS), UV-visible (UV-vis) spectrophotometry, atomic force microscopy (AFM), and transmission electron microscopy (TEM).
KeywordsGold nanoparticle Tris(hydroxymethyl)aminomethane Biocompatible
Chemical and physical properties of gold nanoparticles are dependent of their sizes, shapes, and crystallinity . Up to now, most of the protocols for preparing gold nanoparticles (AuNPs) focus on the particles whose diameters range from 2 to 200 nm with various morphologies [2–5]. Due to their electrochemical properties, such as high affinity with biomolecules and their well-known optical absorption in the visible region surface plasmon band (SPB), gold nanoparticles are proved to be ideal nano-objects for medical imaging and even for photo-thermal therapy [6–8]. Therefore, the application of AuNPs in the biomedical field is growing exponentially. Despite a variety of reductants have been used to stabilize and synthesize AuNPs, only three approaches have been explored to produce size-defined gold nanoparticles through chemical reduction for medicinal applications. They are the citrate capping method , the biphasic Schiffrin-Brust method, and the seeding growth method [10, 11]. Reducing agents or stabilizers and synthetic processes under non-toxic chemicals are important for biocompatible application, particularly for additional integration of the nanoparticles with other biological substrates, which is useful in diagnostic procedures, drug delivery, therapies, and biomedical applications . Thus, a biocompatible protocol with a direct one-pot reaction in a mild condition and well-controlled shapes and sizes is needful in these fields. Many biomolecules such as liposomes , plant extracts , and chitosan [15, 16], as stabilizer and/or reducing agents, have been directly used to synthesize AuNPs. In the present investigation, we describe a new method of designing and synthesizing gold nanoparticles by using Tris(hydroxymethyl)aminomethane. As we have known, Tris is one of the most widely used buffers of nucleic acids and proteins in biochemistry and biotechnology, and has also been adopted as a ligand for the synthesis of chromatographic adsorbents [17, 18]. It is quite active in reduction reactions in various conditions due to its specific structure. More importantly, the reducing agent makes it possible to modify DNA during the process of preparing AuNPs. This feature is very useful for some applications, such as sensors, spectroscopic enhancers, quantum dot, nanostructure fabrication, microimaging methods, and ultrasensitive detection [19–22].
Gold nanoparticles were synthesized by Tris method. Chloroauric acid (AR; 97 ml, 0.01% m/m, SCRC, Beijing, China) with 4 ml Tris solution was stirred using a magnetic stirrer, reduced to Au(0) slowly at 600 rpm at 40°C, and remained for 10 min until it has no visual change for another 10 min. Then, 3 ml NaOH (pH > 14) solution was injected to the solution drop by drop, meanwhile increasing the temperature of the solution to 50°C slowly. We could see the color of the solution gradually change from pink to deep red wine color. After about 8 min, the temperature was decreased to room temperature while stirring was continued to cool the solution. The reaction solution was then centrifuged at 12,000 rpm for 20 min (Xiang Yi centrifugal machine, Changsha, China), and its supernatant was removed; then, the AuNP solution was diluted to the original concentration with ultrapure water (18.2 MΩ, produced by a Milli-Q system, Millipore Co., Billerica, MA, USA). Absorptions were measured using a UV-2450 spectrophotometer (Shimadzu Co., Nakagyo-ku, Kyoto, Japan) operated at a resolution of 1 nm. Atomic force microscopy imaging was performed on SPM-9600 (Shimadzu Co.). Samples for transmission electron microscope (TEM) analysis were prepared by dropping Au nanoparticle solutions onto carbon-coated copper grids. JEM-2100 F (accelerating voltage 200 kV, JEOL, Ltd., Akishima, Tokyo, Japan) was used for obtaining the TEM images, and dynamic light scattering (Nano-zeta-size 90, Malvern Instruments, Westborough, MA, USA) was used mainly for the measurement of particle size and zeta potential.
Results and discussion
UV-vis spectroscopy and atomic force microscopy
The images of transmission electron microscope
Dynamic light scattering (DLS) data of the size distributions of three kinds of gold nanoparticles
For DNA conjugate application, we can further optimize the experimental process to make the reaction conditions much more mildly and to keep the DNA intact under such environment. For this purpose, we replaced the magnetic stirring by ultrasonic vibration, and the heating temperature was set to 45°C. First, the chloroauric acid solution was treated by ultrasonic and heated for 15 min (actual temperature is about 30°C). Then, the mixed solution of 2 ml of 10 mM Tris containing DNA at a concentration of 1 ng/μl with 2 ml NaOH whose mass fraction is 1% was added, and then the solution was ultrasonically treated for one more hour. The final DNA gold nanoparticles were ready for further conjugation.
Zeta potential and mobility of pure DNA and gold nanoparticles prepared using Tris-DNA mixture at 25°C
Zeta potential (mV)
In summary, we presented a new biocompatible synthesis method of gold nanoparticles by Tris, a widely used buffer of nucleic acids and proteins. The method has a useful feature to allow modifying the DNA during the process of preparation of gold nanoparticles. However, the mechanism responsible for biomolecule-directed gold nanoparticle formation remains unclear due to the lack of structural information about biological systems and the fast kinetics of biomimetic chemical systems in solution .
Tris(hydroxymethyl)aminomethane, or 2-amino-2-(hydroxymethyl)-1,3-propanediol, coordinates with a number of metallic ions. In order to understand its unusual acid-base and redox activities, we added Tris solution to chloroauric acid solution until it is completely mixed with the gold ions. Then, we slowly heated the solution to 40°C while adding NaOH solution gently into the solution until the color is stable, immediately adjusting the temperature to room temperature by stirring the solution. In the whole process, temperature does not exceed 45°C, and the stirring speed is about 1,000 rpm or less. In this protocol, by using Tris in alkaline aqueous solution, we can prepare large Au nanoparticles with a polyhedral structure in a temperately process. DNA or cells in vitro are capable of maintaining their intrinsic characteristics under such mild conditions. By using ultrasonic vibration, we can even prepare one-pot DNA-gold nanoparticle conjugates directly, ready for further applications of sensing, imaging, and ultrasensitive detection in biomolecular field [27–29]. During the reaction, a high concentration of NaOH solution is used to promote the reaction rate.
This work was supported by the National Natural Science Foundation of China (No. 11274245) and Innovation Fund of Wenzhou University (31606036010187).
- Zhao P, Li N, Astruc D: State of the art in gold nanoparticle synthesis. Coord Chem Rev 2013, 257(3):638–665.View ArticleGoogle Scholar
- Song C, Zhao G, Zhang P, Rosi NL: Expeditious synthesis and assembly of sub-100 nm hollow spherical gold nanoparticle superstructures. J Am Chem Soc 2010, 132(40):14033–14035.View ArticleGoogle Scholar
- Xia Y, Xia X, Wang Y, Xie S: Shape-controlled synthesis of metal nanocrystals. MRS Bull 2013, 38(04):335–344.View ArticleGoogle Scholar
- Grzelczak M, Perez-Juste J, Mulvaney P, Liz-Marzan LM: Shape control in gold nanoparticle synthesis. Chem Soc Rev 2008, 37(9):1783–1791.View ArticleGoogle Scholar
- Sau TK, Murphy CJ: Room temperature, high-yield synthesis of multiple shapes of gold nanoparticles in aqueous solution. J Am Chem Soc 2004, 126(28):8648–8649.View ArticleGoogle Scholar
- Llevot A, Astruc D: Applications of vectorized gold nanoparticles to the diagnosis and therapy of cancer. Chem Soc Rev 2012, 41(1):242–257.View ArticleGoogle Scholar
- Dreaden EC, Alkilany AM, Huang X, Murphy CJ, El-Sayed MA: The golden age: gold nanoparticles for biomedicine. Chem Soc Rev 2012, 41(7):2740–2779.View ArticleGoogle Scholar
- Rosi NL, Giljohann DA, Thaxton CS, Lytton-Jean AK, Han MS, Mirkin CA: Oligonucleotide-modified gold nanoparticles for intracellular gene regulation. Science 2006, 312(5776):1027–1030.View ArticleGoogle Scholar
- Kimling J, Maier M, Okenve B, Kotaidis V, Ballot H, Plech A: Turkevich method for gold nanoparticle synthesis revisited. J Phys Chem B 2006, 110(32):15700–15707.View ArticleGoogle Scholar
- Brust M, Walker M, Bethell D, Schiffrin DJ, Whyman RJ: Synthesis of thiol-derivatised gold nanoparticles in a two-phase liquid–liquid system. Chem Soc, Chem Commun 1994, 7: 801–802.View ArticleGoogle Scholar
- Jana NR, Gearheart L, Murphy CJ: Seeding growth for size control of 5–40 nm diameter gold nanoparticles. Langmuir 2001, 17(22):6782–6786.View ArticleGoogle Scholar
- Ishizaka T, Ishigaki A, Kawanami H, Suzuki A, Suzuki TM: Dynamic control of gold nanoparticle morphology in a microchannel flow reactor by glucose reduction in aqueous sodium hydroxide solution. J Colloid Interface Sci 2012, 367(1):135–138.View ArticleGoogle Scholar
- He P, Urban MW: Phospholipid-stabilized Au-nanoparticles. Biomacromolecules 2005, 6(3):1224–1225.View ArticleGoogle Scholar
- Kumar KP, Paul W, Sharma CP: Green synthesis of gold nanoparticles with Zingiber officinale extract: characterization and blood compatibility. Process Biochem 2011, 46(10):2007–2013.View ArticleGoogle Scholar
- Huang H, Yang X: Synthesis of chitosan-stabilized gold nanoparticles in the absence/presence of tripolyphosphate. Biomacromolecules 2004, 5(6):2340–2346.View ArticleGoogle Scholar
- Laudenslager MJ, Schiffman JD, Schauer CL: Carboxymethyl chitosan as a matrix material for platinum, gold, and silver nanoparticles. Biomacromolecules 2008, 9(10):2682–2685.View ArticleGoogle Scholar
- Zhang B, Wang Y, Gao M, Gu M, Wang C: Tris (hydroxymethyl) aminomethane‒functionalized agarose particles: parameters affecting the binding of bovine serum albumin. J Sep Sci 2012, 35(12):1406–1410.View ArticleGoogle Scholar
- Dotson RL: Characterization and studies of some four, five and six coordinate transition and representative metal complexes of tris-(hydroxymethyl)-aminomethane. J Inorg Nucl Chem 1972, 34(10):3131–3138.View ArticleGoogle Scholar
- Zanoli LM, D'Agata R, Spoto G: Functionalized gold nanoparticles for ultrasensitive DNA detection. Anal Bioanal Chem 2012, 402(5):1759–1771.View ArticleGoogle Scholar
- Castañeda MT, Alegret S, Merkoçi A: Electrochemical sensing of DNA using gold nanoparticles. Electroanalysis 2007, 19(7–8):743–753.View ArticleGoogle Scholar
- Qian LH, Wang K, Fang HT, Li Y, Ma XL: Au nanoparticles enhance CO oxidation onto SnO2 nanobelt. Mater Chem Phys 2007, 103(1):132–136.View ArticleGoogle Scholar
- Taton TA, Mirkin CA, Letsinger RL: Scanometric DNA array detection with nanoparticle probes. Science 2000, 289(5485):1757–1760.View ArticleGoogle Scholar
- Yu CH, Schubert CP, Welch C, Tang BJ, Tamba MG, Mehl GH: Design, synthesis, and characterization of mesogenic amine-capped nematic gold nanoparticles with surface-enhanced plasmonic resonances. J Am Chem Soc 2012, 134(11):5076–5079.View ArticleGoogle Scholar
- Zhang X, Servos MR, Liu J: Surface science of DNA adsorption onto citrate-capped gold nanoparticles. Langmuir 2012, 28(8):3896–3902.View ArticleGoogle Scholar
- Dujardin E, Hsin LB, Wang CRC, Mann S: DNA-driven self-assembly of gold nanorods. Chem Commun 2001, 14: 1264–1265.View ArticleGoogle Scholar
- Wei H, Wang Z, Zhang J, House S, Gao Y-G, Yang L, Robinson H, Tan LH, Xing H, Hou C: Time-dependent, protein-directed growth of gold nanoparticles within a single crystal of lysozyme. Nat Nanotechnol 2011, 6(2):93–97.View ArticleGoogle Scholar
- Elghanian R, Storhoff JJ, Mucic RC, Letsinger RL, Mirkin CA: Selective colorimetric detection of polynucleotides based on the distance-dependent optical properties of gold nanoparticles. Science 1997, 277(5329):1078–1081.View ArticleGoogle Scholar
- Pei H, Li F, Wan Y, Wei M, Liu H, Su Y, Chen N, Huang Q, Fan C: Designed diblock oligonucleotide for the synthesis of spatially isolated and highly hybridizable functionalization of DNA–gold nanoparticle nanoconjugates. J Chem Soc 2012, 134(29):11876–11879.View ArticleGoogle Scholar
- Zhang X, Servos MR, Liu J: Instantaneous and quantitative functionalization of gold nanoparticles with thiolated DNA using a pH-assisted and surfactant-free route. J Am Chem Soc 2012, 134(17):7266–7269.View ArticleGoogle Scholar
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited.