Short Communication AFM can at an early stage help predict important information The Discriminati... more Short Communication AFM can at an early stage help predict important information The Discrimination of Drug about the behaviour of the drug on large-scale operations.
FASEB journal : official publication of the Federation of American Societies for Experimental Biology, 1998
Controlling receptor-mediated interactions between cells and template surfaces is a central princ... more Controlling receptor-mediated interactions between cells and template surfaces is a central principle in many tissue engineering procedures (1-3). Biomaterial surfaces engineered to present cell adhesion ligands undergo integrin-mediated molecular interactions with cells (1, 4, 5), stimulating cell spreading, and differentiation (6-8). This provides a mechanism for mimicking natural cell-to-matrix interactions. Further sophistication in the control of cell interactions can be achieved by fabricating surfaces on which the spatial distribution of ligands is restricted to micron-scale pattern features (9-14). Patterning technology promises to facilitate spatially controlled tissue engineering with applications in the regeneration of highly organized tissues. These new applications require the formation of ligand patterns on biocompatible and biodegradable templates, which control tissue regeneration processes, before removal by metabolism. We have developed a method of generating micro...
The field of genomics is being immeasurably altered by the introduction of microsystems in the gu... more The field of genomics is being immeasurably altered by the introduction of microsystems in the guise of gene microarrays. There are a number of other microfabricated entities in the literature ranging from single chips for PCR to complete analysis systems. Developments in miniaturised protein analysis, though not as yet as revolutionary as some of those for DNA, are progressing. This
We have demonstrated the site-specific adhesion of photobiotin as a method of producing protein m... more We have demonstrated the site-specific adhesion of photobiotin as a method of producing protein micropatterns. These patterns were created by the selective UV irradiation of a thin film of deposited photobiotin. The UV activated areas of photobiotin were then developed using fluorescently labelled avidin. The size of pattern produced is an order of magnitude smaller than those previously reported by this method. The patterns were characterised using atomic force microscopy (AFM) to determine their microstructure. It was found that the AFM could discriminate between the areas of protein immobilised to the surface through the activated photobiotin, and the bare substrate surface where the inactivated photobiotin had been removed during the washing process. The potential of these patterns as sensing surfaces is demonstrated through the creation of a spatially patterned immunosensing surface. In this case, a biotinylated antibody was bound to the surface and the pattern developed using a second antibody specific to the immobilised biotinylated antibody. This technique could thus provide a simple and efficient method of producing high density immunoassay systems.
We have used albumin-modified atomic force microscope (AFM) tips to probe interactions with a ran... more We have used albumin-modified atomic force microscope (AFM) tips to probe interactions with a range of hydrophilic polymer brush surfaces and protein. Copolymers of poly(ethylene oxide)−poly(propylene oxide)−poly(ethylene oxide) (PEO−PPO−PEO) (Pluronics) ...
A novel liquid flow cell allows atomic force microscopy (AFM) images to be obtained under defined... more A novel liquid flow cell allows atomic force microscopy (AFM) images to be obtained under defined hydrodynamic flow conditions, enabling reaction fluxes calculated from proposed heterogeneous reaction mechanisms to be compared with those determined experimentally. The cell ...
Using the soft lithographic technique, microcontact printing, we demonstrate an example of how a ... more Using the soft lithographic technique, microcontact printing, we demonstrate an example of how a biocompatible polymer can be easily patterned upon another polymer substrate, creating a surface with two spatially different properties. A poly(dimethylsiloxane) mold allowed the ...
This paper describes the formation of highly defined two-dimensional protein arrays onto a polyme... more This paper describes the formation of highly defined two-dimensional protein arrays onto a polymeric substrate expressing biotin functionalities at its surface. Micron-scale arrays of avidin were created by exploiting its interaction with biotin, thereby creating a versatile patterned surface onto ...
... Crystal Shape Engineering. Michael A. Lovette, Andrea Robben Browning, Derek W. Griffin, Jaco... more ... Crystal Shape Engineering. Michael A. Lovette, Andrea Robben Browning, Derek W. Griffin, Jacob P. Sizemore, Ryan C. Snyder and Michael F. Doherty. Industrial & Engineering Chemistry Research 2008 47 (24), 9812-9833. Crystal Shape Engineering. ...
ABSTRACT A scanning probe microscope employing a shear force feedback mechanism as used in most n... more ABSTRACT A scanning probe microscope employing a shear force feedback mechanism as used in most near-field scanning optical microscopes has been utilized to provide phase images of a patterned protein boundary. The microscope employed a dithering fiber optic tip and tuning fork method of tip−sample distance control. The effect of tip vibration amplitude upon the phase contrast is investigated, and possible contrast mechanisms are discussed.
The hydroxide-driven dissolution of the polymer hydroxypropyl methylcellulose phthalate (HPMCP) i... more The hydroxide-driven dissolution of the polymer hydroxypropyl methylcellulose phthalate (HPMCP) in aqueous solution is studied using atomic force microscopy. The novel technique of employing the surfaceaveraged z-piezo voltage as a direct measure of the mean absolute surface height is described, so as, after appropriate calibration, to permit the ready inference of dissolution fluxes. In the case of interest the following dissolution rate law was established: j/g‚cm-2 ‚s-1) 105.0[OH-] over the pH range 8.0-9.2, where j is the flux of the dissolving polymer and [OH-] is measured in mol cm-3. LA961094M
Journal of the Association for Laboratory Automation, 2000
M icrofluidic systems are developing in application and importance in many aspects of chemistry. ... more M icrofluidic systems are developing in application and importance in many aspects of chemistry. This short review aims to provide a simple introduction to some of the concepts and instrumentation involved in this field. In particular, a number of systems for reactions, detections and analysis that have arisen from the research of our group are illustrated.
We report the use of atomic force microscopy to observe the initial stages of b-amyloid ®brilliza... more We report the use of atomic force microscopy to observe the initial stages of b-amyloid ®brillization in situ. The growth of individual b-amyloid proto®brils on a mica substrate was followed over several hours. The ®rst in situ visualization of proto®bril formation from single aggregate units of b-amyloid is reported. The growth of these proto®brils through the subsequent addition of these aggregate units is also observed. Growth of the proto®brils is bi-directional and the outgrowth of proto-®brils from a common amyloid/heterogeneous core is also observed. Elongation also occurred by the addition of proto®brils from solution. This data provides an exciting insight into the early stages of b-amyloid ®brillization and can be used to enhance the understanding of the mechanism(s) by which b-amyloid ®brillizes and may consequently enable inhibition of one or more stages of ®brillization as a potential therapeutic strategy.
In chemical processing, it is important to distinguish between and identify polymorphic forms. We... more In chemical processing, it is important to distinguish between and identify polymorphic forms. We demonstrate the novel use of scanning thermal microscopy (SThM) and localized thermal analysis to distinguish and identify polymorphic forms of the drug cimetidine. These forms cannot be resolved by classical bulk thermal analysis. SThM reveals a sample consisting of a 50 : 50 mixture of the polymorphs contains regions of different thermal conductivity, corresponding to the different polymorphs. Localized thermal analysis of small volumes of pure polymorphic samples (approximately 50 mm 3) shows that the origin of the thermal conductivity contrast lies, at least in part, with the presence of a surface water layer on the more hydrophilic polymorph.
A t|uuiitita[ivc study of the hydrolytic dissolution of solid p-cliloianii at alkaline pH using a... more A t|uuiitita[ivc study of the hydrolytic dissolution of solid p-cliloianii at alkaline pH using a combination of the channel How cell and in situ atomic force microscopy measurements shows that the dissolution is driven by reaction of the substrate with hydroxide ions at, or very close to, the dissolving surface. The dissolution rate equation, deduced from the channel How cell for single crystals of p-chloranil, is rate/molcm 's ' = 3.8 X l()"'[OH ]|| where [OH~^]||/M is the hydroxide ion concentration adjacent to the solid surface. An analogous rate law is derived for pressed pellet substrates. The novel application of the atomic force microscope to make absolute measurements of surface averaged dissolution rates is described. Comparison with the independent channel How cell data reveals good mechanistic agreement and consistency of rate constants provided it is recognised that a thick stagnant diffusion layer can be present under the usual conditions employed for AFM.
The strongly implicit procedure is used to model the diffusion-only chronoamperometric responses ... more The strongly implicit procedure is used to model the diffusion-only chronoamperometric responses of microband electrode geometries which deviate from the ideal. Specifically, attention is focused on four electrode shapes: elevated microband electrodes (with conducting supporting ...
The application of power ultrasound in electrochemistry may promote or usefully modify electrode ... more The application of power ultrasound in electrochemistry may promote or usefully modify electrode reactions. In the work reported here the four-electron reduction of nitrobenzene in alkaline (pH \3) aqueous media was studied as a model system. The electrochemical reduction is known to follow a complex mechanism [E. Laviron, A. Vallat and R. Meunier-Prest, J. Electroanal. Chern., 379 (1994) 427], involving protonations as well as a dehydration step; both surface and solution pathways for this reduction may be observed [c. Nishihara and H. Shindo, J. Electroanal. Chern., 221 (1987) 245], depending on the nature and state of the electrode. Both under silent and ultrasonic conditions nitrobenzene is reduced on glassy carbon electrodes in a chemically reversible one-electron process followed by an irreversible three-electron reduction. At sufficiently negative potentials the reduction process remains overall four-electron, with phenylhydroxylamine as the major product even at the high current densities obtained with intense ultrasound. Glassy carbon electrodes are shown to be suitable for kinetic studies, although damage, as endorsed by an increase in roughness and capacitance and probably initiated by mechanical damage at very short electrode-hom distances, was detected by a.c. impedance, voltammetric and atomic force microscopy (AFM) methods. On gold electrodes a more complicated mechanism due to a surface reaction pathway arises. A comparison of sonovoltammetric and rotating disk voltammetric results gives evidence for the homogeneous pathway being dominant under applied ultrasound conditions. The transition between surface and solution pathways is mass flux as well as concentration dependent, and an estimate for the rate of the surface catalyzed reaction for a concentration of l.44mM nitrobenzene (k = 4 ± 2 X 10-2 em s-1), attributed to protonation of the nitrobenzene radical anion, is obtained from combined rotating disk and sonovoltammetric data. Damage to the gold surface as monitored by various techniques is small, but manifests itself by an interesting decrease in double layer capacitance.
Short Communication AFM can at an early stage help predict important information The Discriminati... more Short Communication AFM can at an early stage help predict important information The Discrimination of Drug about the behaviour of the drug on large-scale operations.
FASEB journal : official publication of the Federation of American Societies for Experimental Biology, 1998
Controlling receptor-mediated interactions between cells and template surfaces is a central princ... more Controlling receptor-mediated interactions between cells and template surfaces is a central principle in many tissue engineering procedures (1-3). Biomaterial surfaces engineered to present cell adhesion ligands undergo integrin-mediated molecular interactions with cells (1, 4, 5), stimulating cell spreading, and differentiation (6-8). This provides a mechanism for mimicking natural cell-to-matrix interactions. Further sophistication in the control of cell interactions can be achieved by fabricating surfaces on which the spatial distribution of ligands is restricted to micron-scale pattern features (9-14). Patterning technology promises to facilitate spatially controlled tissue engineering with applications in the regeneration of highly organized tissues. These new applications require the formation of ligand patterns on biocompatible and biodegradable templates, which control tissue regeneration processes, before removal by metabolism. We have developed a method of generating micro...
The field of genomics is being immeasurably altered by the introduction of microsystems in the gu... more The field of genomics is being immeasurably altered by the introduction of microsystems in the guise of gene microarrays. There are a number of other microfabricated entities in the literature ranging from single chips for PCR to complete analysis systems. Developments in miniaturised protein analysis, though not as yet as revolutionary as some of those for DNA, are progressing. This
We have demonstrated the site-specific adhesion of photobiotin as a method of producing protein m... more We have demonstrated the site-specific adhesion of photobiotin as a method of producing protein micropatterns. These patterns were created by the selective UV irradiation of a thin film of deposited photobiotin. The UV activated areas of photobiotin were then developed using fluorescently labelled avidin. The size of pattern produced is an order of magnitude smaller than those previously reported by this method. The patterns were characterised using atomic force microscopy (AFM) to determine their microstructure. It was found that the AFM could discriminate between the areas of protein immobilised to the surface through the activated photobiotin, and the bare substrate surface where the inactivated photobiotin had been removed during the washing process. The potential of these patterns as sensing surfaces is demonstrated through the creation of a spatially patterned immunosensing surface. In this case, a biotinylated antibody was bound to the surface and the pattern developed using a second antibody specific to the immobilised biotinylated antibody. This technique could thus provide a simple and efficient method of producing high density immunoassay systems.
We have used albumin-modified atomic force microscope (AFM) tips to probe interactions with a ran... more We have used albumin-modified atomic force microscope (AFM) tips to probe interactions with a range of hydrophilic polymer brush surfaces and protein. Copolymers of poly(ethylene oxide)−poly(propylene oxide)−poly(ethylene oxide) (PEO−PPO−PEO) (Pluronics) ...
A novel liquid flow cell allows atomic force microscopy (AFM) images to be obtained under defined... more A novel liquid flow cell allows atomic force microscopy (AFM) images to be obtained under defined hydrodynamic flow conditions, enabling reaction fluxes calculated from proposed heterogeneous reaction mechanisms to be compared with those determined experimentally. The cell ...
Using the soft lithographic technique, microcontact printing, we demonstrate an example of how a ... more Using the soft lithographic technique, microcontact printing, we demonstrate an example of how a biocompatible polymer can be easily patterned upon another polymer substrate, creating a surface with two spatially different properties. A poly(dimethylsiloxane) mold allowed the ...
This paper describes the formation of highly defined two-dimensional protein arrays onto a polyme... more This paper describes the formation of highly defined two-dimensional protein arrays onto a polymeric substrate expressing biotin functionalities at its surface. Micron-scale arrays of avidin were created by exploiting its interaction with biotin, thereby creating a versatile patterned surface onto ...
... Crystal Shape Engineering. Michael A. Lovette, Andrea Robben Browning, Derek W. Griffin, Jaco... more ... Crystal Shape Engineering. Michael A. Lovette, Andrea Robben Browning, Derek W. Griffin, Jacob P. Sizemore, Ryan C. Snyder and Michael F. Doherty. Industrial & Engineering Chemistry Research 2008 47 (24), 9812-9833. Crystal Shape Engineering. ...
ABSTRACT A scanning probe microscope employing a shear force feedback mechanism as used in most n... more ABSTRACT A scanning probe microscope employing a shear force feedback mechanism as used in most near-field scanning optical microscopes has been utilized to provide phase images of a patterned protein boundary. The microscope employed a dithering fiber optic tip and tuning fork method of tip−sample distance control. The effect of tip vibration amplitude upon the phase contrast is investigated, and possible contrast mechanisms are discussed.
The hydroxide-driven dissolution of the polymer hydroxypropyl methylcellulose phthalate (HPMCP) i... more The hydroxide-driven dissolution of the polymer hydroxypropyl methylcellulose phthalate (HPMCP) in aqueous solution is studied using atomic force microscopy. The novel technique of employing the surfaceaveraged z-piezo voltage as a direct measure of the mean absolute surface height is described, so as, after appropriate calibration, to permit the ready inference of dissolution fluxes. In the case of interest the following dissolution rate law was established: j/g‚cm-2 ‚s-1) 105.0[OH-] over the pH range 8.0-9.2, where j is the flux of the dissolving polymer and [OH-] is measured in mol cm-3. LA961094M
Journal of the Association for Laboratory Automation, 2000
M icrofluidic systems are developing in application and importance in many aspects of chemistry. ... more M icrofluidic systems are developing in application and importance in many aspects of chemistry. This short review aims to provide a simple introduction to some of the concepts and instrumentation involved in this field. In particular, a number of systems for reactions, detections and analysis that have arisen from the research of our group are illustrated.
We report the use of atomic force microscopy to observe the initial stages of b-amyloid ®brilliza... more We report the use of atomic force microscopy to observe the initial stages of b-amyloid ®brillization in situ. The growth of individual b-amyloid proto®brils on a mica substrate was followed over several hours. The ®rst in situ visualization of proto®bril formation from single aggregate units of b-amyloid is reported. The growth of these proto®brils through the subsequent addition of these aggregate units is also observed. Growth of the proto®brils is bi-directional and the outgrowth of proto-®brils from a common amyloid/heterogeneous core is also observed. Elongation also occurred by the addition of proto®brils from solution. This data provides an exciting insight into the early stages of b-amyloid ®brillization and can be used to enhance the understanding of the mechanism(s) by which b-amyloid ®brillizes and may consequently enable inhibition of one or more stages of ®brillization as a potential therapeutic strategy.
In chemical processing, it is important to distinguish between and identify polymorphic forms. We... more In chemical processing, it is important to distinguish between and identify polymorphic forms. We demonstrate the novel use of scanning thermal microscopy (SThM) and localized thermal analysis to distinguish and identify polymorphic forms of the drug cimetidine. These forms cannot be resolved by classical bulk thermal analysis. SThM reveals a sample consisting of a 50 : 50 mixture of the polymorphs contains regions of different thermal conductivity, corresponding to the different polymorphs. Localized thermal analysis of small volumes of pure polymorphic samples (approximately 50 mm 3) shows that the origin of the thermal conductivity contrast lies, at least in part, with the presence of a surface water layer on the more hydrophilic polymorph.
A t|uuiitita[ivc study of the hydrolytic dissolution of solid p-cliloianii at alkaline pH using a... more A t|uuiitita[ivc study of the hydrolytic dissolution of solid p-cliloianii at alkaline pH using a combination of the channel How cell and in situ atomic force microscopy measurements shows that the dissolution is driven by reaction of the substrate with hydroxide ions at, or very close to, the dissolving surface. The dissolution rate equation, deduced from the channel How cell for single crystals of p-chloranil, is rate/molcm 's ' = 3.8 X l()"'[OH ]|| where [OH~^]||/M is the hydroxide ion concentration adjacent to the solid surface. An analogous rate law is derived for pressed pellet substrates. The novel application of the atomic force microscope to make absolute measurements of surface averaged dissolution rates is described. Comparison with the independent channel How cell data reveals good mechanistic agreement and consistency of rate constants provided it is recognised that a thick stagnant diffusion layer can be present under the usual conditions employed for AFM.
The strongly implicit procedure is used to model the diffusion-only chronoamperometric responses ... more The strongly implicit procedure is used to model the diffusion-only chronoamperometric responses of microband electrode geometries which deviate from the ideal. Specifically, attention is focused on four electrode shapes: elevated microband electrodes (with conducting supporting ...
The application of power ultrasound in electrochemistry may promote or usefully modify electrode ... more The application of power ultrasound in electrochemistry may promote or usefully modify electrode reactions. In the work reported here the four-electron reduction of nitrobenzene in alkaline (pH \3) aqueous media was studied as a model system. The electrochemical reduction is known to follow a complex mechanism [E. Laviron, A. Vallat and R. Meunier-Prest, J. Electroanal. Chern., 379 (1994) 427], involving protonations as well as a dehydration step; both surface and solution pathways for this reduction may be observed [c. Nishihara and H. Shindo, J. Electroanal. Chern., 221 (1987) 245], depending on the nature and state of the electrode. Both under silent and ultrasonic conditions nitrobenzene is reduced on glassy carbon electrodes in a chemically reversible one-electron process followed by an irreversible three-electron reduction. At sufficiently negative potentials the reduction process remains overall four-electron, with phenylhydroxylamine as the major product even at the high current densities obtained with intense ultrasound. Glassy carbon electrodes are shown to be suitable for kinetic studies, although damage, as endorsed by an increase in roughness and capacitance and probably initiated by mechanical damage at very short electrode-hom distances, was detected by a.c. impedance, voltammetric and atomic force microscopy (AFM) methods. On gold electrodes a more complicated mechanism due to a surface reaction pathway arises. A comparison of sonovoltammetric and rotating disk voltammetric results gives evidence for the homogeneous pathway being dominant under applied ultrasound conditions. The transition between surface and solution pathways is mass flux as well as concentration dependent, and an estimate for the rate of the surface catalyzed reaction for a concentration of l.44mM nitrobenzene (k = 4 ± 2 X 10-2 em s-1), attributed to protonation of the nitrobenzene radical anion, is obtained from combined rotating disk and sonovoltammetric data. Damage to the gold surface as monitored by various techniques is small, but manifests itself by an interesting decrease in double layer capacitance.
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Papers by Giles Sanders