Sonny Mark | Cornell University (original) (raw)
Papers by Sonny Mark
Journal of Physical Chemistry C, 2007
... suppressed, revealing an inverse ionic strength dependence, and was thus assigned to the Gouy... more ... suppressed, revealing an inverse ionic strength dependence, and was thus assigned to the Gouy−Chapman diffusion layer (Gouy−Chapman capacitance C dl ... Sofia Sotiropoulou, Yajaira Sierra-Sastre, Sonny S. Mark and Carl A. Batt. Chemistry of Materials 2008 20 (3), 821-834. ...
MRS Proceedings, 2006
... Parijat Bhatnagar , Sonny S Mark , Il Kim , Hongyu Chen , Brad Schmidt , Michal Lipson , and ... more ... Parijat Bhatnagar , Sonny S Mark , Il Kim , Hongyu Chen , Brad Schmidt , Michal Lipson , and Carl A Batt 1 2 3 3 4 4 ... be used to create high resolution patterns as aligning the PDMS stamp with submicron features is non-trivial.[13] Polymer lift-off[14] and patterned gold[15] based ...
The Journal of Physical Chemistry B, 2004
Arrays of Au nanoparticles were created using the inherent repeating patterns of bacterial S-laye... more Arrays of Au nanoparticles were created using the inherent repeating patterns of bacterial S-layer proteins. Bacterial self-assembling S-layer protein lattices display a highly repetitive surface structure that makes them particularly suitable as biotemplates to fabricate metallic/semiconducting nanostructures and arrays. One interesting S-layer for nanoparticle templating is the hexagonally packed intermediate (HPI) layer of Deinococcus radiodurans. This S-layer, displaying hexagonal (p6) symmetry, is comprised of a hexameric protein core unit with a central pore, surrounded by six relatively large openings ("vertex points"). In this work, the influences of particle properties and adsorption conditions on the formation of ordered arrays of 5-nm Au nanoparticles using HPI S-layers were investigated. Using transmission electron microscopy (TEM), it was found that the templating of citrate-capped Au nanoparticles on HPI layers under low ionic strength conditions resulted in hexagonal-packed ordered arrays with ∼18-nm interparticle spacings that corresponded with the pore-to-pore distance of the S-layer. Interestingly, nanoparticle binding occurs at the vertex points on the HPI layer and, due to repulsion forces, adsorption tends to be favored at every second vertex point. Upon increasing the ionic strength, ordered packing is still observed. However, because interparticle repulsions are less prominent, adsorption of nanoparticles occurs in virtually every available vertex point, resulting in the formation of a honeycomb-like pattern of nanoparticles extending throughout the HPI monolayer sheet. Combined with the results of additional investigations using either uncharged hydroxy-terminated particles or positively charged ferritin molecules, the experimental data suggest that the creation of ordered arrays through biotemplating of Au nanoparticles onto HPI S-layers depends on the electrostatic interactions between individual nanoparticles as well as the interaction with the HPI layer.
Macromolecular Bioscience, 2008
Aqueous suspendible polymer nanostructures were prepared by simple microtome processing of electr... more Aqueous suspendible polymer nanostructures were prepared by simple microtome processing of electrospun nylon 6 nanofibers and were used to immobilize calf intestinal alkaline phosphatase (ALP) by either covalent or noncovalent bioconjugation chemistries. It was found that noncovalent immobilization of ALP to the mechanically cut nanofibers (mean length % 4 mm; mean diameter % 80 nm) using a multi-stacked, layer-by-layer (LBL) approach with the cationic polymer Sapphire II TM resulted in the highest enzyme loading (48.1 AE 0.4 mg Á mg À1 nanofiber) when compared to other covalent immobilization methods based on glutaraldehyde crosslinking. The biofunctionalized nanofibers were also characterized for their chemiluminescent activity with the dioxetane substrate, CSPD TM . The results indicate that the kinetic parameters, K m and V max , for the catalytic activity of the nanostructure-bound ALP enzyme were influenced by the particular types of immobilization methods employed. In terms of the overall catalytic performance of the various immobilized ALP systems, a single-stacked LBL assembly approach resulted in the highest level of enzymatic activity per unit mass of nanofiber support. To the best of our knowledge, this study represents the first report examining the preparation of mechanically shortened, aqueous dispersed electrospun polymer nanofibers for potential application as enzyme scaffolds in chemiluminescent-based assay systems.
Macromolecular Bioscience, 2008
Cover: The cover shows the bioconjugation and characterization of aqueous suspendible polymer nan... more Cover: The cover shows the bioconjugation and characterization of aqueous suspendible polymer nanostructures prepared by simple microtome processing of electrospun nylon 6 nanofibers. Mechanically shortened, aqueous dispersed electrospun polymer nanofibers have potential application as enzyme scaffolds in chemiluminescentbased assay systems. Further details can be found in the article by
Macromolecular Bioscience, 2010
S-Layer proteins are an example of bionanostructures that can be exploited in nanofabrication. In... more S-Layer proteins are an example of bionanostructures that can be exploited in nanofabrication. In addition to their ordered structure, the ability to self-assembly is a key feature that makes them a promising technological tool. Here, in vitro self-assembly kinetics of SpbA was investigated, and found that it occurs at a rate that is dependent on temperature, its concentration, and the concentration of calcium ions and sodium chloride. The activation enthalpy (120.81 kJ Á mol À1 ) and entropy (129.34 J Á mol À1 Á K À1 ) obtained infers that the incorporation of monomers incurs in a net loss of hydrophobic surface. By understanding how the protein monomers drive the self-assembly at different conditions, the rational optimization of this process was feasible.
Macromolecular Bioscience, 2006
Langmuir, 2006
Two-dimensional (2-D) surface layer (S-layer) protein lattices isolated from the Gram-positive ba... more Two-dimensional (2-D) surface layer (S-layer) protein lattices isolated from the Gram-positive bacterium Deinococcus radiodurans and the acidothermophilic archaeon Sulfolobus acidocaldarius were investigated and compared for their ability to biotemplate the formation of self-assembled, ordered arrays of inorganic nanoparticles (NPs). The NPs employed for these studies included citrate-capped gold NPs and various species of CdSe/ZnS core/shell quantum dots (QDs). The QD nanocrystals were functionalized with different types of thiol ligands (negative-or positivecharged/short-or long-chain length) in order to render them hydrophilic and thus water-soluble. Transmission electron microscopy, Fourier transform analyses, and pair correlation function calculations revealed that ordered nanostructured arrays with a range of spacings (∼7-22 nm) and different geometrical arrangements could be fabricated through the use of the two types of S-layers. These results demonstrate that it is possible to exploit the physicochemical/structural diversity of prokaryotic S-layer scaffolds to vary the morphological patterning of nanoscale metallic and semiconductor NP arrays.
Langmuir, 2004
We report here a multistep route for the immobilization of DNA and proteins on chemically modifie... more We report here a multistep route for the immobilization of DNA and proteins on chemically modified gold substrates using fourth-generation NH(2)-terminated poly(amidoamine) dendrimers supported by an underlying amino undecanethiol (AUT) self-assembled monolayer (SAM). Bioactive ultrathin organic films were prepared via layer-by-layer self-assembly methods and characterized by fluorescence microscopy, variable angle spectroscopic ellipsometry, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and attenuated total internal reflection Fourier transform infrared spectroscopy (ATR-FTIR). The thickness of the AUT SAM base layer on the gold substrates was determined to be 1.3 nm from ellipsometry. Fluorescence microscopy and AFM measurements, in combination with analyses of the XPS/ATR-FTIR spectra, confirmed the presence of the dendrimer/biopolymer molecules on the multilayer sensor surfaces. Model proteins, including streptavidin and rabbit immunoglobulin proteins, were covalently attached to the dendrimer layer using linear cross-linking reagents. Through surface plasmon resonance measurements, we found that sensor surfaces containing a dendrimer layer displayed an increased protein immobilization capacity, compared to AUT SAM sensor surfaces without dendrimer molecules. Other SPR studies also revealed that the dendrimer-based surfaces are useful for the sensitive and specific detection of DNA-DNA interactions. Significantly, the multicomponent films displayed a high level of stability during repeated regeneration and hybridization cycles, and the kinetics of the DNA-DNA hybridization process did not appear to be influenced by surface mass transport limiting effects.
Colloids and Surfaces B: Biointerfaces, 2008
The noncovalent immobilization of alkaline phosphatase (ALP) onto aqueous dispersed nylon 6 nanor... more The noncovalent immobilization of alkaline phosphatase (ALP) onto aqueous dispersed nylon 6 nanorods ( approximately 310 nm mean diameter; approximately 6 microm mean length) prepared by anodic aluminum oxide (AAO) membrane templating was studied. Using multi-stacked layer-by-layer (LBL) assembly with the cationic quaternary ammonium polymer Sapphire II , the amount of ALP enzyme loaded onto the polymer nanostructures was found to be 115+/-7 microg mg(-1) nanorod. The biofunctionalized nanorods were also characterized for their chemiluminescent activity with the dioxetane substrate, CSPD . The results indicate that the kinetic parameters, K(m) and V(max), for the catalytic activity of the nanostructure-bound ALP enzyme are different from those of soluble ('free') ALP. While the K(m) value was measured to be 156 microM for free ALP, the apparent K(m) value determined for the LBL-immobilized ALP is approximately 20% lower (122 microM). Furthermore, despite the relatively high enzyme loading capacity of the nanorods, the specific activity of the bound ALP enzyme was found to be almost nine times lower than that measured for free ALP. Finally, additional experiments revealed that the catalytic activities of both free ALP and nanorod-conjugated ALP are affected similarly by changes in pH, with optimal performance levels occurring under conditions of pH 9.5. To the best of our knowledge, this study represents the first report examining the preparation of aqueous dispersed, AAO-templated polymer nanorods for potential application as enzyme scaffolds in chemiluminescent-based assay systems.
Chemistry of Materials, 2008
... that TMV particles could be used for the deposition of a variety of nanoparticle types, inclu... more ... that TMV particles could be used for the deposition of a variety of nanoparticle types, including ... the use of phage-display techniques.(28) This allowed the formation of ZnS and CdS ... Thefabrication of highly oriented quantum dot nanowires was also demonstrated, as well as the ...
Biotechnology Progress, 2006
Poly-gamma-glutamic acid (gamma-PGA) obtained from Bacillus licheniformis ATCC 9945 was evaluated... more Poly-gamma-glutamic acid (gamma-PGA) obtained from Bacillus licheniformis ATCC 9945 was evaluated as a potential biosorbent material for use in the removal of heavy metals from aqueous solution. Copper (Cu(2+)) was chosen as the model heavy metal used in these studies since it is extensively used by electroplating and other industries, has been the model for many other similar studies, and can be easily assayed through a number of convenient methods. Cu(2+)-gamma-PGA binding parameters under varying conditions of pH, temperature, ionic strength, and in the presence of other heavy metal ions were determined for the purified biopolymer using a specially designed dialysis apparatus. Applying the Langmuir adsorption isotherm model showed that gamma-PGA had a copper capacity approaching 77.9 mg/g and a binding constant of 32 mg/L (0.5 mM) at pH 4.0 and 25 degrees C. Cu(2+)-gamma-PGA adsorption was relatively temperature independent between 7 and 40 degrees C, while an increase in ionic strength led to a decrease in metal ion binding. Cd(2+) and Zn(2+) ions compete with Cu(2+) for binding sites on the gamma-PGA biopolymer. Metal uptake by gamma-PGA was further tested using a tangential flow filtration apparatus in a diafiltration mode in which metal was continually processed through a dilute solution of gamma-PGA without allowing for equilibrium to be established. The circulating polymer solution was able to complex metal as well as successfully prevent passage of unbound copper ions present in solution through the membrane. Using 500 mL of a 0.2% gamma-PGA solution, up to 97% of a 50 mg/L copper sulfate solution processed at a flow rate of 115 mL/min was retained by the polymer. For a 10 mg/L solution of Cu(2+) as copper sulfate, filtrate concentrations of Cu(2+) never rose above 0.6 mg/L while processing 2.5 L of dilute copper sulfate.
Biomacromolecules, 2006
We investigated the formation of self-assembled two-dimensional (2-D) arrays of dendrimer-encapsu... more We investigated the formation of self-assembled two-dimensional (2-D) arrays of dendrimer-encapsulated platinum nanoparticles (Pt-DENs) using prokaryotic surface-layer (S-layer) proteins as biomacromolecular templates. The Pt-DENs (mean core diameter 1.8 +/- 0.5 nm) were synthesized by chemical reduction of metal ion species complexed within the interior of fourth-generation, hydroxyl-terminated, starburst poly(amidoamine) dendrimers (G4 PAMAM-OH). Detailed structural and elemental composition analyses performed using high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, electron energy loss spectroscopy, and X-ray photoelectron spectroscopy indicated that the dendrimer-metal nanocomposite particles were crystalline in nature rather than amorphous and that at least some quantity of the platinum found within the particles is present in the expected zerovalent state. By using the S-layer lattices from the acidothermophilic archaeon Sulfolobus acidocaldarius and the Gram-positive bacterium Deinococcus radiodurans as a biotemplate, hexagonal- and honeycomb-ordered arrays of the Pt-DENs were successfully fabricated under a range of different pH conditions via noncovalent nanoparticle-protein interactions. Fast Fourier transform analyses of transmission electron microscopy images verified that the fabricated Pt-DEN assemblies displayed mean periodicities that corresponded well with the lattice constants of the native protein templates (i.e., 22 and 18 nm for S. acidocaldarius and D. radiodurans S layers, respectively). Our results demonstrate that utilizing pre-synthesized Pt-DENs in conjunction with microbial S-layer proteins displaying highly periodic topochemical properties can be an effective, novel route for creating patterned arrays of Pt nanoparticles with potential technological applications.
We will present results of simultaneous electrical and fluorescence detection of biomolecules in ... more We will present results of simultaneous electrical and fluorescence detection of biomolecules in microfluidic channels. For the electrical signal we use carbon nanotube field effect transistors suspended across the fluidic channel. When a single molecule tethered with standard fluorescence dyes passes the carbon nanotube a sharp change in conductance occurs, correlated with fluorescence signal from the molecule itself. We will
Advanced Materials, 2006
. Hybridization assay of probe DNA with complementary target DNA. a) After hybridization with ctD... more . Hybridization assay of probe DNA with complementary target DNA. a) After hybridization with ctDNA. b) After treatment with 99.5 % formamide as a chaotropic medium. c) After rehybridization with ctDNA. Scale bar represents 30 lm for all three panels.
Colloids and Surfaces B: Biointerfaces, 2007
We explored the bionanofabrication of silicon nanopillar structures using ordered gold nanopartic... more We explored the bionanofabrication of silicon nanopillar structures using ordered gold nanoparticle arrays generated from microbial surface layer (S-layer) protein templates. The S-layer template used for these thin film processing experiments was isolated from the Gram-positive bacterium Deinococcus radiodurans. In this preliminary work, S-layers preimmobilized onto chemically modified silicon substrates were initially used to template the fabrication of a nanolithographic hard mask pattern comprised of a hexagonally ordered array of 5-nm gold nanoparticles (lattice constant = 18 nm). Significantly, the use of the biotemplated gold nanoparticle mask patterns in an inductively coupled plasma (ICP) etching process successfully yielded silicon nanopillar structures. However, it was found that the resultant nanopillars (8-13 nm wide at the tip, 15-20 nm wide at half-height, 20-30 nm wide at the base, and 60-90 nm tall) appeared to lack any significant degree of translational ordering. The results suggest that further studies are needed in order to elucidate the optimal plasma processing parameters that will lead to the generation of long-range ordered arrays of silicon-based nanostructures using S-layer protein templates.
Journal of Physical Chemistry C, 2007
... suppressed, revealing an inverse ionic strength dependence, and was thus assigned to the Gouy... more ... suppressed, revealing an inverse ionic strength dependence, and was thus assigned to the Gouy−Chapman diffusion layer (Gouy−Chapman capacitance C dl ... Sofia Sotiropoulou, Yajaira Sierra-Sastre, Sonny S. Mark and Carl A. Batt. Chemistry of Materials 2008 20 (3), 821-834. ...
MRS Proceedings, 2006
... Parijat Bhatnagar , Sonny S Mark , Il Kim , Hongyu Chen , Brad Schmidt , Michal Lipson , and ... more ... Parijat Bhatnagar , Sonny S Mark , Il Kim , Hongyu Chen , Brad Schmidt , Michal Lipson , and Carl A Batt 1 2 3 3 4 4 ... be used to create high resolution patterns as aligning the PDMS stamp with submicron features is non-trivial.[13] Polymer lift-off[14] and patterned gold[15] based ...
The Journal of Physical Chemistry B, 2004
Arrays of Au nanoparticles were created using the inherent repeating patterns of bacterial S-laye... more Arrays of Au nanoparticles were created using the inherent repeating patterns of bacterial S-layer proteins. Bacterial self-assembling S-layer protein lattices display a highly repetitive surface structure that makes them particularly suitable as biotemplates to fabricate metallic/semiconducting nanostructures and arrays. One interesting S-layer for nanoparticle templating is the hexagonally packed intermediate (HPI) layer of Deinococcus radiodurans. This S-layer, displaying hexagonal (p6) symmetry, is comprised of a hexameric protein core unit with a central pore, surrounded by six relatively large openings ("vertex points"). In this work, the influences of particle properties and adsorption conditions on the formation of ordered arrays of 5-nm Au nanoparticles using HPI S-layers were investigated. Using transmission electron microscopy (TEM), it was found that the templating of citrate-capped Au nanoparticles on HPI layers under low ionic strength conditions resulted in hexagonal-packed ordered arrays with ∼18-nm interparticle spacings that corresponded with the pore-to-pore distance of the S-layer. Interestingly, nanoparticle binding occurs at the vertex points on the HPI layer and, due to repulsion forces, adsorption tends to be favored at every second vertex point. Upon increasing the ionic strength, ordered packing is still observed. However, because interparticle repulsions are less prominent, adsorption of nanoparticles occurs in virtually every available vertex point, resulting in the formation of a honeycomb-like pattern of nanoparticles extending throughout the HPI monolayer sheet. Combined with the results of additional investigations using either uncharged hydroxy-terminated particles or positively charged ferritin molecules, the experimental data suggest that the creation of ordered arrays through biotemplating of Au nanoparticles onto HPI S-layers depends on the electrostatic interactions between individual nanoparticles as well as the interaction with the HPI layer.
Macromolecular Bioscience, 2008
Aqueous suspendible polymer nanostructures were prepared by simple microtome processing of electr... more Aqueous suspendible polymer nanostructures were prepared by simple microtome processing of electrospun nylon 6 nanofibers and were used to immobilize calf intestinal alkaline phosphatase (ALP) by either covalent or noncovalent bioconjugation chemistries. It was found that noncovalent immobilization of ALP to the mechanically cut nanofibers (mean length % 4 mm; mean diameter % 80 nm) using a multi-stacked, layer-by-layer (LBL) approach with the cationic polymer Sapphire II TM resulted in the highest enzyme loading (48.1 AE 0.4 mg Á mg À1 nanofiber) when compared to other covalent immobilization methods based on glutaraldehyde crosslinking. The biofunctionalized nanofibers were also characterized for their chemiluminescent activity with the dioxetane substrate, CSPD TM . The results indicate that the kinetic parameters, K m and V max , for the catalytic activity of the nanostructure-bound ALP enzyme were influenced by the particular types of immobilization methods employed. In terms of the overall catalytic performance of the various immobilized ALP systems, a single-stacked LBL assembly approach resulted in the highest level of enzymatic activity per unit mass of nanofiber support. To the best of our knowledge, this study represents the first report examining the preparation of mechanically shortened, aqueous dispersed electrospun polymer nanofibers for potential application as enzyme scaffolds in chemiluminescent-based assay systems.
Macromolecular Bioscience, 2008
Cover: The cover shows the bioconjugation and characterization of aqueous suspendible polymer nan... more Cover: The cover shows the bioconjugation and characterization of aqueous suspendible polymer nanostructures prepared by simple microtome processing of electrospun nylon 6 nanofibers. Mechanically shortened, aqueous dispersed electrospun polymer nanofibers have potential application as enzyme scaffolds in chemiluminescentbased assay systems. Further details can be found in the article by
Macromolecular Bioscience, 2010
S-Layer proteins are an example of bionanostructures that can be exploited in nanofabrication. In... more S-Layer proteins are an example of bionanostructures that can be exploited in nanofabrication. In addition to their ordered structure, the ability to self-assembly is a key feature that makes them a promising technological tool. Here, in vitro self-assembly kinetics of SpbA was investigated, and found that it occurs at a rate that is dependent on temperature, its concentration, and the concentration of calcium ions and sodium chloride. The activation enthalpy (120.81 kJ Á mol À1 ) and entropy (129.34 J Á mol À1 Á K À1 ) obtained infers that the incorporation of monomers incurs in a net loss of hydrophobic surface. By understanding how the protein monomers drive the self-assembly at different conditions, the rational optimization of this process was feasible.
Macromolecular Bioscience, 2006
Langmuir, 2006
Two-dimensional (2-D) surface layer (S-layer) protein lattices isolated from the Gram-positive ba... more Two-dimensional (2-D) surface layer (S-layer) protein lattices isolated from the Gram-positive bacterium Deinococcus radiodurans and the acidothermophilic archaeon Sulfolobus acidocaldarius were investigated and compared for their ability to biotemplate the formation of self-assembled, ordered arrays of inorganic nanoparticles (NPs). The NPs employed for these studies included citrate-capped gold NPs and various species of CdSe/ZnS core/shell quantum dots (QDs). The QD nanocrystals were functionalized with different types of thiol ligands (negative-or positivecharged/short-or long-chain length) in order to render them hydrophilic and thus water-soluble. Transmission electron microscopy, Fourier transform analyses, and pair correlation function calculations revealed that ordered nanostructured arrays with a range of spacings (∼7-22 nm) and different geometrical arrangements could be fabricated through the use of the two types of S-layers. These results demonstrate that it is possible to exploit the physicochemical/structural diversity of prokaryotic S-layer scaffolds to vary the morphological patterning of nanoscale metallic and semiconductor NP arrays.
Langmuir, 2004
We report here a multistep route for the immobilization of DNA and proteins on chemically modifie... more We report here a multistep route for the immobilization of DNA and proteins on chemically modified gold substrates using fourth-generation NH(2)-terminated poly(amidoamine) dendrimers supported by an underlying amino undecanethiol (AUT) self-assembled monolayer (SAM). Bioactive ultrathin organic films were prepared via layer-by-layer self-assembly methods and characterized by fluorescence microscopy, variable angle spectroscopic ellipsometry, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and attenuated total internal reflection Fourier transform infrared spectroscopy (ATR-FTIR). The thickness of the AUT SAM base layer on the gold substrates was determined to be 1.3 nm from ellipsometry. Fluorescence microscopy and AFM measurements, in combination with analyses of the XPS/ATR-FTIR spectra, confirmed the presence of the dendrimer/biopolymer molecules on the multilayer sensor surfaces. Model proteins, including streptavidin and rabbit immunoglobulin proteins, were covalently attached to the dendrimer layer using linear cross-linking reagents. Through surface plasmon resonance measurements, we found that sensor surfaces containing a dendrimer layer displayed an increased protein immobilization capacity, compared to AUT SAM sensor surfaces without dendrimer molecules. Other SPR studies also revealed that the dendrimer-based surfaces are useful for the sensitive and specific detection of DNA-DNA interactions. Significantly, the multicomponent films displayed a high level of stability during repeated regeneration and hybridization cycles, and the kinetics of the DNA-DNA hybridization process did not appear to be influenced by surface mass transport limiting effects.
Colloids and Surfaces B: Biointerfaces, 2008
The noncovalent immobilization of alkaline phosphatase (ALP) onto aqueous dispersed nylon 6 nanor... more The noncovalent immobilization of alkaline phosphatase (ALP) onto aqueous dispersed nylon 6 nanorods ( approximately 310 nm mean diameter; approximately 6 microm mean length) prepared by anodic aluminum oxide (AAO) membrane templating was studied. Using multi-stacked layer-by-layer (LBL) assembly with the cationic quaternary ammonium polymer Sapphire II , the amount of ALP enzyme loaded onto the polymer nanostructures was found to be 115+/-7 microg mg(-1) nanorod. The biofunctionalized nanorods were also characterized for their chemiluminescent activity with the dioxetane substrate, CSPD . The results indicate that the kinetic parameters, K(m) and V(max), for the catalytic activity of the nanostructure-bound ALP enzyme are different from those of soluble ('free') ALP. While the K(m) value was measured to be 156 microM for free ALP, the apparent K(m) value determined for the LBL-immobilized ALP is approximately 20% lower (122 microM). Furthermore, despite the relatively high enzyme loading capacity of the nanorods, the specific activity of the bound ALP enzyme was found to be almost nine times lower than that measured for free ALP. Finally, additional experiments revealed that the catalytic activities of both free ALP and nanorod-conjugated ALP are affected similarly by changes in pH, with optimal performance levels occurring under conditions of pH 9.5. To the best of our knowledge, this study represents the first report examining the preparation of aqueous dispersed, AAO-templated polymer nanorods for potential application as enzyme scaffolds in chemiluminescent-based assay systems.
Chemistry of Materials, 2008
... that TMV particles could be used for the deposition of a variety of nanoparticle types, inclu... more ... that TMV particles could be used for the deposition of a variety of nanoparticle types, including ... the use of phage-display techniques.(28) This allowed the formation of ZnS and CdS ... Thefabrication of highly oriented quantum dot nanowires was also demonstrated, as well as the ...
Biotechnology Progress, 2006
Poly-gamma-glutamic acid (gamma-PGA) obtained from Bacillus licheniformis ATCC 9945 was evaluated... more Poly-gamma-glutamic acid (gamma-PGA) obtained from Bacillus licheniformis ATCC 9945 was evaluated as a potential biosorbent material for use in the removal of heavy metals from aqueous solution. Copper (Cu(2+)) was chosen as the model heavy metal used in these studies since it is extensively used by electroplating and other industries, has been the model for many other similar studies, and can be easily assayed through a number of convenient methods. Cu(2+)-gamma-PGA binding parameters under varying conditions of pH, temperature, ionic strength, and in the presence of other heavy metal ions were determined for the purified biopolymer using a specially designed dialysis apparatus. Applying the Langmuir adsorption isotherm model showed that gamma-PGA had a copper capacity approaching 77.9 mg/g and a binding constant of 32 mg/L (0.5 mM) at pH 4.0 and 25 degrees C. Cu(2+)-gamma-PGA adsorption was relatively temperature independent between 7 and 40 degrees C, while an increase in ionic strength led to a decrease in metal ion binding. Cd(2+) and Zn(2+) ions compete with Cu(2+) for binding sites on the gamma-PGA biopolymer. Metal uptake by gamma-PGA was further tested using a tangential flow filtration apparatus in a diafiltration mode in which metal was continually processed through a dilute solution of gamma-PGA without allowing for equilibrium to be established. The circulating polymer solution was able to complex metal as well as successfully prevent passage of unbound copper ions present in solution through the membrane. Using 500 mL of a 0.2% gamma-PGA solution, up to 97% of a 50 mg/L copper sulfate solution processed at a flow rate of 115 mL/min was retained by the polymer. For a 10 mg/L solution of Cu(2+) as copper sulfate, filtrate concentrations of Cu(2+) never rose above 0.6 mg/L while processing 2.5 L of dilute copper sulfate.
Biomacromolecules, 2006
We investigated the formation of self-assembled two-dimensional (2-D) arrays of dendrimer-encapsu... more We investigated the formation of self-assembled two-dimensional (2-D) arrays of dendrimer-encapsulated platinum nanoparticles (Pt-DENs) using prokaryotic surface-layer (S-layer) proteins as biomacromolecular templates. The Pt-DENs (mean core diameter 1.8 +/- 0.5 nm) were synthesized by chemical reduction of metal ion species complexed within the interior of fourth-generation, hydroxyl-terminated, starburst poly(amidoamine) dendrimers (G4 PAMAM-OH). Detailed structural and elemental composition analyses performed using high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, electron energy loss spectroscopy, and X-ray photoelectron spectroscopy indicated that the dendrimer-metal nanocomposite particles were crystalline in nature rather than amorphous and that at least some quantity of the platinum found within the particles is present in the expected zerovalent state. By using the S-layer lattices from the acidothermophilic archaeon Sulfolobus acidocaldarius and the Gram-positive bacterium Deinococcus radiodurans as a biotemplate, hexagonal- and honeycomb-ordered arrays of the Pt-DENs were successfully fabricated under a range of different pH conditions via noncovalent nanoparticle-protein interactions. Fast Fourier transform analyses of transmission electron microscopy images verified that the fabricated Pt-DEN assemblies displayed mean periodicities that corresponded well with the lattice constants of the native protein templates (i.e., 22 and 18 nm for S. acidocaldarius and D. radiodurans S layers, respectively). Our results demonstrate that utilizing pre-synthesized Pt-DENs in conjunction with microbial S-layer proteins displaying highly periodic topochemical properties can be an effective, novel route for creating patterned arrays of Pt nanoparticles with potential technological applications.
We will present results of simultaneous electrical and fluorescence detection of biomolecules in ... more We will present results of simultaneous electrical and fluorescence detection of biomolecules in microfluidic channels. For the electrical signal we use carbon nanotube field effect transistors suspended across the fluidic channel. When a single molecule tethered with standard fluorescence dyes passes the carbon nanotube a sharp change in conductance occurs, correlated with fluorescence signal from the molecule itself. We will
Advanced Materials, 2006
. Hybridization assay of probe DNA with complementary target DNA. a) After hybridization with ctD... more . Hybridization assay of probe DNA with complementary target DNA. a) After hybridization with ctDNA. b) After treatment with 99.5 % formamide as a chaotropic medium. c) After rehybridization with ctDNA. Scale bar represents 30 lm for all three panels.
Colloids and Surfaces B: Biointerfaces, 2007
We explored the bionanofabrication of silicon nanopillar structures using ordered gold nanopartic... more We explored the bionanofabrication of silicon nanopillar structures using ordered gold nanoparticle arrays generated from microbial surface layer (S-layer) protein templates. The S-layer template used for these thin film processing experiments was isolated from the Gram-positive bacterium Deinococcus radiodurans. In this preliminary work, S-layers preimmobilized onto chemically modified silicon substrates were initially used to template the fabrication of a nanolithographic hard mask pattern comprised of a hexagonally ordered array of 5-nm gold nanoparticles (lattice constant = 18 nm). Significantly, the use of the biotemplated gold nanoparticle mask patterns in an inductively coupled plasma (ICP) etching process successfully yielded silicon nanopillar structures. However, it was found that the resultant nanopillars (8-13 nm wide at the tip, 15-20 nm wide at half-height, 20-30 nm wide at the base, and 60-90 nm tall) appeared to lack any significant degree of translational ordering. The results suggest that further studies are needed in order to elucidate the optimal plasma processing parameters that will lead to the generation of long-range ordered arrays of silicon-based nanostructures using S-layer protein templates.