Functionalized Nanoporous Silica for the Removal of Heavy Metals from Biological Systems: Adsorption and Application

Department of Biomedical Engineering, OHSU School of Medicine, Portland, Oregon 97239, USA.
ACS Applied Materials & Interfaces (Impact Factor: 5.9). 10/2010; 2(10):2749-58. DOI: 10.1021/am100616b
Source: PubMed

ABSTRACT Surface-functionalized nanoporous silica, often referred to as self-assembled monolayers on mesoporous supports (SAMMS), has previously demonstrated the ability to serve as very effective heavy metal sorbents in a range of aquatic and environmental systems, suggesting that they may be advantageously utilized for biomedical applications such as chelation therapy. Herein we evaluate surface chemistries for heavy metal capture from biological fluids, various facets of the materials' biocompatibility, and the suitability of these materials as potential therapeutics. Of the materials tested, thiol-functionalized SAMMS proved most capable of removing selected heavy metals from biological solutions (i.e., blood, urine, etc.) Consequentially, thiol-functionalized SAMMS was further analyzed to assess the material's performance under a number of different biologically relevant conditions (i.e., variable pH and ionic strength) to gauge any potentially negative effects resulting from interaction with the sorbent, such as cellular toxicity or the removal of essential minerals. Additionally, cellular uptake studies demonstrated no cell membrane permeation by the silica-based materials generally highlighting their ability to remain cellularly inert and thus nontoxic. The results show that organic ligand functionalized nanoporous silica could be a valuable material for a range of detoxification therapies and potentially other biomedical applications.

1 Follower
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Divalent cations, especially calcium (Ca 2ϩ), are known to significantly affect the performance of anionic surfactants and polymers used in enhanced oil recovery (EOR) processes. An efficient technique to remove Ca 2ϩ from brine is reported, which is based on selective adsorption of Ca 2ϩ onto functionalized iron oxide magnetic nanoparticles (IOMNPs). Upon adsorption, the IOMNPs can be separated by applying a magnetic field, leaving behind softened water. IOMNP was synthesized by coprecipitation, and the amine-functionalization of its surface was obtained according to an aqueous APTES coating process. Chelating agent, polyacrylic acid (PAA), was successfully coated on amine-functionalized IOMNPs via amidation of carboxylic acid using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC). PAA modification significantly enhanced the adsorption capacity of IOMNPs due to their great ability to chelate Ca 2ϩ . The effect of pH on adsorption capacity was also investigated. The adsorption capacity of Ca 2ϩ onto PAA-IOMNPs was found to be as high as 57.2 mg/g at pH 7 from the 400 mg/L Ca 2ϩ solution. However, in American Petroleum Institute (API) standard brine (8ϫ10 4 mg/L NaCl and 2ϫ10 4 mg/L CaCl 2), the adsorption capacity of IOMNPs decreased to 9.8 mg/g since the high salinity screens the charges on the surface of PAA-IOMNPs and results in the formation of nanoparticle aggregates. PAA-IOMNPs can be reused after treated by acetic acid solution. A geochemical model was developed to describe the competitive adsorption of Ca 2ϩ and H ϩ onto amine-functionalized IOMNPs as a function of solution pH and Ca 2ϩ concentration. Comparison between the model and the experiments shows that the adsorption isotherms predict the behavior of the system very well. Below pH 4, adsorption of Ca 2ϩ is negligible and becomes important above pH 7. This opens the possibility of recovering the nanoparticles after the divalent cation removal, and reusing them for the repeated water softening.
    2014 International Petroleum Technology Conference; 12/2014
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Phosphate removal is both biologically and environmentally important. Biologically, hyperphosphatemia is a critical condition in end-stage chronic kidney disease patients. Patients with hyperphosphatemia are treated long-term with oral phosphate binders to prevent phosphate absorption to the body by capturing phosphate in the gastrointestinal (GI) tract followed by fecal excretion. Environmentally, phosphate levels in natural water resources must be regulated according to limits set forth by the US Environmental Protection Agency. By utilizing nanotechnology and ligand design, we developed a new material to overcome limitations of traditional sorbent materials such as low phosphate binding capacity, slow binding kinetics, and negative interference by other anions. A phosphate binder based on ironethylenediamine on nanoporous silica (Fe-EDA-SAMMS) has been optimized for substrates and Fe(III) deposition methods. The Fe-EDA-SAMMS material had a 4-fold increase in phosphate binding capacity and a broader operating pH window compared to other reports. The material had a faster phosphate binding rate and was significantly less affected by other anions than Sevelamer HCl, the gold standard oral phosphate binder, and AG® 1-X8, a commercially available anion exchanger. It had less cytotoxicity to Caco-2 cells than lanthanum carbonate, another prescribed oral phosphate binder. The Fe-EDA-SAMMS also had high capacity for arsenate and chromate, two of the most toxic anions in natural water.
    Journal of Nanomedicine & Nanotechnology 09/2014; 5(4):222. DOI:10.4172/2157-7439.1000222 · 5.72 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Thiol-functionalized porous silicon (PS) monolayer was evaluated for its possible application in As (III) adsorption. Dimercaptosuccinic acid (DMSA) attached to mesoporous silicon via amide bond linkages was used as a chelate for As (III). Two different aminosilanes namely 3-(aminopropyl) triethoxysilane (APTES) and 3-aminopropyl (diethoxy)-methylsilane (APDEMS) were tested as linkers to evaluate the relative response for DMSA attachment. The aminosilane-modified PS samples were attached to DMSA by wet impregnation followed by the adsorption of As (III). Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) have been used to identify the functional groups and to estimate the As (III) content, respectively. FTIR spectroscopy confirmed the covalent bonding of DMSA with amide and R-COOH groups on the nanostructured porous surface. XPS confirms the preferred arsenic adsorption on the surface of PS/DMSA samples as compared to the aminosilane-modified and bare PS substrates.
    Nanoscale Research Letters 09/2014; 9(1):508. DOI:10.1186/1556-276X-9-508 · 2.52 Impact Factor

Full-text (2 Sources)

Available from
May 22, 2014