Grantee Research Project Results
Final Report: A Bioengineering Approach to Nanoparticle based Environmental Remediation
EPA Grant Number: R829601Title: A Bioengineering Approach to Nanoparticle based Environmental Remediation
Investigators: Strongin, Daniel R. , Douglas, Trevor , Schoonen, Martin A.A.
Institution: Temple University , The State University of New York at Stony Brook , Montana State University
EPA Project Officer: Hahn, Intaek
Project Period: February 1, 2002 through January 31, 2005
Project Amount: $399,979
RFA: Exploratory Research: Nanotechnology (2001) RFA Text | Recipients Lists
Research Category: Hazardous Waste/Remediation , Nanotechnology , Safer Chemicals
Objective:
The overall goal of this research project was to develop biomediated routes to the synthesis and control of nanometal and metal oxide structures and to use these nanostructures for both chemical and photochemical environmental remediation. Our working hypothesis is that nanomaterials will provide a chemistry conducive to environmental remediation that cannot be obtained at more traditional spatial dimensions (i.e., > Fm).
The research was a multidisciplinary effort to develop a firm understanding of the properties of nanosize metal oxide compounds within the protein shell (or cage) of the iron (Fe) storage protein, ferritin. These systems are unexplored in terms of their potential use in remediation processes or as a method for synthesis of nanoscale particles of metal compounds. The entire system, consisting of the inorganic core material and protein shell, provided opportunities for the development of new catalysts by manipulating the composition and size of the core material, as well as chemically functionalizing the surrounding protein shell.
The specific objectives of this research project were to: (1) develop a bioengineering approach to assemble nano-size particles with well-defined size and composition; and (2) investigate the potential for use of the synthesized nanoparticles in environmental remediation chemistry as a function of size and composition. To meet Objective 1, we developed methods to synthesize oxide nanoparticles within ferritin having different sizes in the nanoregime. These nanoparticles also were to be used as precursors to nanometallic particles. To meet Objective 2, we investigated the photochemistry of ferritin-derived particles for environmentally relevant redox chemistry.
Summary/Accomplishments (Outputs/Outcomes):
Reduction of CrO42-
Horse spleen ferritin (HS_fn) is a 24-subunit protein of roughly spherical shape with outer and inner diameters of approximately 12 and 8 nm, respectively. The native mineral core of ferritin is the ferric oxyhydroxide ferrihydrite, Fe(O)OH. Fe(O)OH particles, which ranged from 5 to 7.5 nm in diameter, were used in the experiments. The ferritin protein without the Fe(O)OH core (i.e., apoferritin) was inactive toward hexavalent chromium reduction under our experimental conditions, suggesting that the Fe(O)OH provided the active catalytic sites in the redox chemistry. Experiments using photon band-pass filters suggested that the reaction occurred out of a photo-induced electron-hole pair, and the optical band gap for the Fe(O)OH semiconductor was determined to be in the range of 2.5-3.5 eV. Comparison of ferritin and protein-free Fe(O)OH mineral nanoparticles indicated that ferritin provided a photocatalyst with significantly more stability to aggregation and the loss of catalytic activity.
HS-Fn as a Precursor to Supported Metal Oxide and Metallic Nanoparticles
Figure 1 shows an Atomic Force Microscopy (AFM) Tapping mode™ image of ferrihydrite nanoparticles prepared by ultraviolet (UV)-ozone treatment of 2500 Fe loaded ferritin dispersed on a SiO2 substrate. The accompanying cross-section shows the full range of height values to be 6.5 nm, with a root-mean-square (RMS) roughness (standard deviation of the height about the average value) of 1.46 nm. The peak-to-valley height differences for the large features in the cross-section are in the 4-6 nm range. The lateral full widths at half maximum of the individual particles are several times larger than the heights caused by tip convolution effects.
Figure 1. AFM Tapping Mode™ Micrographs (top view) of Fe(O)OH Nanoparticles Prepared by UV-Ozone Treatment of 2500 Fe Loaded Ferritin for 60 Minutes at 100°C Under Oxygen (< 5 psi); Section Analysis
Reduction of the ferrihydrite nanoparticles to the Fe metal was carried out in a reaction cell coupled to the ultrahigh vacuum (UHV) chamber. The sample then was transferred directly into the UHV chamber where X-ray photoelectron spectroscopy was carried out. The AFM image of these particular particles (Figure 2) shows a similar morphology to the particles before reduction. Again, the peak-to-valley height differences for the large features in the cross-section are in the 4-6 nm range, and in this case the RMS roughness is 1.47.
Figure 2. AFM Tapping Mode™ Micrographs (Top View) of Fe Nanoparticles Prepared by Heating 2500 Fe Loaded Fe(O)OH Nanoparticles in a Reducing Environment; Section Analysis
Formation of Reactive Cu Nanoparticles Encapsulated Within the Protein Cage of Ferritin
The photolysis of Cu(II) in the presence of Fe oxide-mineralized ferritin and a sacrificial reductant such as citrate or tartrate resulted in the formation of a red-wine color after an hour. Control reactions photolyzed in the absence of Cu(II), tartrate/citrate, or Fe oxide mineralized ferritin did not change color over the same period. No reaction was observed when solutions were left in the dark or in the presence of the unmineralized (apo) ferritin. In addition, Fe(II) alone was not observed to spontaneously reduce Cu(II) in deaerated solutions. Examination of the photolysis products by transmission electron microscopy (TEM) revealed electron-dense spherical particles (see Figure 3), with the Cu(II) ferritin ratio serving as the major determinant of particle size. Histograms of particle sizes were fit to Gaussian distributions. Higher Cu(II) ferritin ratios led to larger particle sizes, with loadings of 250, 500, 1000, and 2000 leading to average particle diameters of 4.5 ± 0.8, 9.7 ± 4.2, 12.7 ± 3.6, and 31.4 ± 10.1 nm, respectively. The reactivity of these nano-Cu particles will be investigated with regard to environmental remediation reactions.
Figure 3. Metallic Cu Particles Grown Within Ferritin
Formation of Fe2O3 and TiO2 Nanoparticles Within the Protein Cage of Ferritin
Mineralization of mammalian ferritin using high oxidation state transition metal ions as starting materials can be achieved using a photoreduction process. We have successfully mineralized the Fn cages with Fe-oxhydroxide and Ti-oxhydroxide nanoparticles, in a spatially selective manner, and encapsulated the resultant nanoparticles within the protein cages. The composite materials, synthesized in this way, have particle sizes that are highly monodisperse. This represents a new synthetic approach to the formation of protein encapsulated metal oxhydroxide materials in the nanoscale size regime.
Photolysis of a solution of Fe(III) or Ti(IV) citrate in the presence of the apo-ferritin cage results in the formation of small amounts of Fe(II) and Ti(III), respectively. In the presence of oxygen these reoxidize and hydrolyze to form nanoparticles within the protein cage. The Fe reaction could be monitored spectroscopically by the development of the ligand-to-metal charge transfer absorbance characteristic of Fe(III)oxo-polymers. When the reaction was performed in the absence of the protein cages, the development of the color clearly was associated with the formation of a rust colored precipitate. When Ti(IV) citrate was used as a starting material, there was no change in color during the photolysis reaction, but in the presence of the protein cages the reaction solution remained homogeneous, whereas in control reactions, in the absence of the protein cage, a white precipitate formed as the photolysis proceeded. If the photolysis was performed under inert atmosphere, the characteristic purple color of d1Ti(III) species could be observed.
The Ti-oxyhydroxide material was tested for its ability to catalyze the photo-reduction of CrO42- under Xe-arc lamp illumination. This material exhibited a catalytic behavior similar to that observed previously for Fe2O3-Ferritin.
Sorption of SO2 on Nanoferrihydrite Assembled Within Ferritin
Nanoscale materials potentially could form the basis of a new generation of environmental remediation technologies that provide solutions to some of the challenging environmental cleanup problems. In this study, we report on the preparation of a series of supported Fe and cobalt oxyhydroxide nanoparticle model surfaces and investigated their reactivities toward a SO2/O2 mixture. HS_fn was used to prepare 3 nm- and 5 nm-supported ferrihydrite nanoparticles and a ferritin-like protein from Listeria innocua was used to prepare 3-4 nm cobalt oxide nanoparticles. AFM was used to characterize the particles. Attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy was used to study the in situ oxidation of SO2 on the nanoparticles. The ATR-FTIR data shown in Figure 4 is associated with the adsorption and reaction of SO2 with 8 nm (left panel), 4 nm(center panel), and 2 nm (right panel) particles assembled within ferritin. Analysis of the data suggests that SO2 is converted efficiently to SO42- on the largest particles, but on the smaller particles SO32- is the dominant product.
Figure 4. ATR-FTIR Data
Journal Articles on this Report : 3 Displayed | Download in RIS Format
Other project views: | All 26 publications | 7 publications in selected types | All 3 journal articles |
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Type | Citation | ||
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Ensign D, Young M, Douglas T. Photocatalytic synthesis of copper colloids from Cu(II) by the ferrihydrite core of ferritin. Inorganic Chemistry 2004;43(11):3441-3446. |
R829601 (Final) |
not available |
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Hosein HA, Strongin DR, Allen M, Douglas T. Iron and Cobalt oxide and metallic nanoparticles prepared from ferritin. Langmuir 2004;20(23):10283-10287. |
R829601 (Final) |
not available |
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Kim I, Hosein H-A, Strongin DR, Douglas T. Photochemical reactivity of ferritin for Cr(VI) reduction. Chemistry of Materials 2002;14(11):4874-4879. |
R829601 (2002) R829601 (Final) |
not available |
Supplemental Keywords:
nanotechnology, environmental chemistry, remediation, soil, water, chemicals, toxics, organics, metals, solvents, photocatalysis, environmental sustainability, nanocatalysts, environmental engineering,, RFA, Scientific Discipline, Waste, Water, Sustainable Industry/Business, Sustainable Environment, Physics, Environmental Chemistry, Remediation, Technology for Sustainable Environment, New/Innovative technologies, Bioremediation, Environmental Engineering, Engineering, Chemistry, & Physics, nanoparticle remediation, decontamination, bioengineering, nanoscale biopolymers, wastewater, biodegradation, remediation technologies, nanotechnology, environmental sustainability, bio-engineering, nanocatalysts, groundwater remediation, aquifer remediation design, environmentally applicable nanoparticles, biotechnology, sustainability, groundwater contamination, biochemistry, contaminated aquifers, innovative technologies, cadmium, nanoparticle based remediationProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.