Enzyme reactors were fabricated on silicon wafers using microstructuring technologies. The reacto... more Enzyme reactors were fabricated on silicon wafers using microstructuring technologies. The reactors were made of several parallel vertically-cut flow channels. The reactor structures occupied a wafer area of 3 * 15 mm. Reactors with two different channel densities were fabricated: 10 channels/ mm, 165 /xm deep; and 25 channels/mm, 235 /~m deep. Glucose oxidase was immobilised on the reactors and their corresponding enzyme activities were monitored by a colourimetric assay. It was shown that a reactor surface area increase of 3 times gave rise to a proportional enzyme activity increase in the reactor. The maximum glucose turnover rate for the reactor with 25 channels/ mm was approximately 35 nmol/minute and the corresponding apparent Km was approximately 17 raM. A wafer integrated enzyme reactor was also operated in a microdialysis-based system for continuous glucose monitoring, showing a linear response up to 4 mM glucose.
Technology Transfer (TT) is on the rise in Europe with an increased focus on cooperation between ... more Technology Transfer (TT) is on the rise in Europe with an increased focus on cooperation between public research and the business community, as it enables good ideas and inventions to be transforme ...
The Journal of Hand Surgery: Journal of the British Society for Surgery of the Hand, 1997
SESSION 8 39 tion. We used this neurotization in traumatic cases but it is possibly applicable to... more SESSION 8 39 tion. We used this neurotization in traumatic cases but it is possibly applicable to complete palsies caused by ulnar entrapment at the elbow that cannot be improved by a simple neurolysis. We describe the assessment protocol, physiotherapy and operative regime and standardized functional review which we have instituted to maximize the hand and upper limb function of children with mucopolysaccharidoses and mucolipidoses.
Porous silicon is generated in five different silicon types of -orientation and the influence of ... more Porous silicon is generated in five different silicon types of -orientation and the influence of dopant type and dopant concentration with respect to ability to serve as an enzyme activated biocatalytic substrate. Glucose oxidase was immobilised onto the porous surfaces and a maximum increase in catalytic efficiency of 350 times was demonstrated. The influence of the depth of the porous layer was investigated, showing that an average porous depth of no more than 5–10 μm is optimal for the parallel channel structured micro enzyme reactors developed by our group.
Proceedings of 18th Annual International Conference of the IEEE Engineering in Medicine and Biology Society
Micro flow-through cells were fabricated in silicon and were designed to work as micro enzyme rea... more Micro flow-through cells were fabricated in silicon and were designed to work as micro enzyme reactors (columns) for glucose monitoring. The reactor design comprised a parallel channel structure with 32 channels, 50 μm wide. A reactor with vertical channels yields a much larger surface area than a corresponding v-groove channel structure. Therefore, (110) silicon was used to allow the fabrication
Porous silicon with its spongious structure and vast surface enlargement was investigated as the ... more Porous silicon with its spongious structure and vast surface enlargement was investigated as the carrier matrix for immobilised enzymes in micro enzyme reactors.
Proceedings of the International Solid-State Sensors and Actuators Conference - TRANSDUCERS '95
SUMMARY A micromashined flow-through cell for liquid sampling is presented. The flow channel is f... more SUMMARY A micromashined flow-through cell for liquid sampling is presented. The flow channel is formed by two 350 pn deep silicon basins facing each other with a 60 p diameter orifice in the centre of one of the basins. A piezo-ceramic disc glued to the silicon basin opposite the orifice controls the drop ejection in a drop-on-demand fashion. The ejected
The optimization of the catalytic performance of porous silicon enzyme microreactors with respect... more The optimization of the catalytic performance of porous silicon enzyme microreactors with respect to the reactor geometry is reported. The microreactors were fabricated in p-type silicon with anisotropic KOH-etching. To increase the effective area the silicon was made porous by anodisation in a HF-ethanol solution. The performance of the different reactors was evaluated by coupling glucose oxidase onto the porous matrix and measuring the catalytic turn-over rate.
The design and fabrication of a flow-through cell in <11O>-oriented silicon, which acts as a gluc... more The design and fabrication of a flow-through cell in <11O>-oriented silicon, which acts as a glucose oxidase enzyme reactor, is described. The reactor structure was made of several tall, parallel, standing walls, anisotropically etched in silicon, which occupies a wafer area of 3 * 15 mm 2. Reactors of two geometries were fabricated on the designated area, holding either 30 lamellre (165 11m tall, spaced 50 11m apart) or 75 lamellre (235 11m tall, spaced ",30 11m apart). Glucose oxidase was immobilised to the silicon surface available in the reactor. The lamella structure acted as an area enlarging geometry to achieve a high enzyme activity in the reactor. The two reactors exposed 172 mm 2 and 515 mm 2 of silicon surface respectively for the enzyme immobilisation. Enzyme activity determinations of the reactors showed that the reactor area increase yielded an increase in maximum glucose turnover rate from 10 nmol/min to ",37 nmol/min. The 515 mm 2 reactor was also operated in a system for continuous glucose monitoring, based on continuous glucose sampling via microdialysis. At a perfusion rate of 25 Ill/min, the system responded linearly to glucose levels between o and 5 mM after which the oxygen limitation affected the response.
Journal of Micromechanics and Microengineering, 1997
Miniaturization and silicon integration of micro enzyme reactors for applications in micro total ... more Miniaturization and silicon integration of micro enzyme reactors for applications in micro total analysis systems (µTASs) require new methods to achieve structures with a large surface area onto which the enzyme can be coupled. This paper describes a method to accomplish a highly efficient silicon microstructured enzyme reactor utilizing porous silicon as the carrier matrix. The enzyme activity of microreactors with a porous layer was recorded and compared with a microreactor without the porous layer. The microreactors were fabricated as flow-through cells comprising 32 channels, 50 µm wide, spaced 50 µm apart and 250 µm deep micromachined in 110 oriented silicon, p type (20-70 cm), by anisotropic wet etching. The overall dimension of the microreactors was 13.1 × 3.15 mm. To make the porous silicon layer, the reactor structures were anodized in a solution of hydrofluoric acid and ethanol. In order to evaluate the surface enlarging effect of different pore morphologies, the anodization was performed at three different current densities, 10, 50 and 100 mA cm −2. Glucose oxidase was immobilized onto the three porous microreactors and a non-porous reference reactor. The enzyme activity of the reactors was monitored following a colorimetric assay. To evaluate the glucose monitoring capabilities, the reactor anodized at 50 mA cm −2 was connected to an FIA system for glucose monitoring. The system displayed a linear response of glucose up to 15 mM using an injection volume of 0.5 µl. The result from the studies of glucose turnover rate clearly demonstrates the potential of porous silicon as a surface enlarging matrix for micro enzyme reactors. An increase in enzyme activity by a factor of 100, compared to the non-porous reference, was achieved for the reactor anodized at 50 mA cm −2 .
Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 1998
The performance of doped silicon and porous silicon as a new electrode material in neurophysiolog... more The performance of doped silicon and porous silicon as a new electrode material in neurophysiological applications is investigated. By increasing the surface area of adopted silicon region through anodisation in hydrofluoric acid it was found that the impedance parameters of the electrode were considerably improved. Impedance spectra of bare silicon electrodes, porous electrodes and platinum electroplated porous silicon electrodes are
Proceedings of 18th Annual International Conference of the IEEE Engineering in Medicine and Biology Society
Silicon membranes (diameter=4 mm, thickness=60 μm) with a circular matrix of holes centered at th... more Silicon membranes (diameter=4 mm, thickness=60 μm) with a circular matrix of holes centered at the chip were fabricated using anisotropic etching. The perforated area had a diameter of 2 mm. Three membrane geometries (hole sizes of 10, 50 or 100 μm) were investigated to find a suitable hole size for the nerve regeneration. The silicon membranes were mounted between two
The development of a miniaturised silicon wafer integrated enzyme reactor is described. The react... more The development of a miniaturised silicon wafer integrated enzyme reactor is described. The reactor was micromachined by anisotropic wet etching of (110) silicon. The enzyme glucose oxidase (GOx) was coupled to the reactor surface with standard methods of immobilising enzyme to silica. The glucose turn-over rate was monitored following a colourimetric assay. The advantage, in terms of high surface area per volume ratio, of utilising (110) silicon for microreactor fabrication compared to (100) silicon was demonstrated. Two reactors with different channel widths (50 and 20 µm) and channel densities (10 and 25 per millimetre) were compared, yielding a proportionally increased enzyme activity, for the reactor with the highest surface area (20 µm channels, 25 channels per millimetre). A novel method, utilising porous silicon as a coupling matrix, to increase the surface area for enzyme coupling was investigated. A porous silicon layer was fabricated on samples by anodic dissolution of si...
The influence of the carrier matrix depth and homogeneity was investigated for porous silicon enz... more The influence of the carrier matrix depth and homogeneity was investigated for porous silicon enzyme bioreactors. For the experiments h110i oriented silicon, p-type (20±70 W cm), was used. Porous silicon was generated on planar surfaces and on anisotropically pre-etched high aspect ratio parallel channel reactors. Samples were prepared with three depths, controlled by the anodisation time, and two current densities yielding different morphologies. In a second study, in order to make the porous layer more homogeneous, reactors were fabricated with different channel widths and wall thickness. Glucose oxidase (GO x) was immobilised onto the porous matrix following standard procedures for immobilisation of enzyme to silica. The enzyme activity of the samples was monitored following a colourimetric assay. The results clearly display the influence of the matrix depth for both the planar and the reactor structures. An 170-fold increase in catalytic turnover , when compared to an identical non-porous reference, was recorded for a reactor with an average porous depth of 10 mm. The importance of a homogeneous porous layer was illustrated, giving an increase in catalytic performance of three times between different structures with the same geometric area prior to anodisation.
The use of porous silicon (PS) as an efficient surface enlarging carrier matrix for immobilised e... more The use of porous silicon (PS) as an efficient surface enlarging carrier matrix for immobilised enzymes is demonstrated. An optimal porous matrix in p-type silicon (10±20 Wcm) with respect to enzymatic substrate turnover was obtained when anodising the sample at 100 mA/cm 2 for 5 min. An increase in glucose turnover of %220 times as compared to an enzyme activated polished surface was recorded. The highest increase in turnover was found to be 350 times for an n-epilayer on n + substrate. The application of glucose monitoring is demonstrated showing a linear range to 15 mM glucose with a satisfactory storage and operational stability. The use of ascorbate oxidase activated porous silicon for the elimination of ascorbate (an electrochemical interferent) in glutamate monitoring is reported. An upper elimination level of 1 mM ascorbate was found. PS is also reported as an efficient protein cleavage surface when activated with proteases. Cleavage times normally ranging between 6 and 24 h were found to be 60 s in the microreactor. Myoglobin cleaved on a trypsin microreactor is shown with the corresponding mass spectra having a sequence coverage of 79%.
Rationale: The anticonvulsant valproate is an HDAC inhibitor, which has in vitro been shown to se... more Rationale: The anticonvulsant valproate is an HDAC inhibitor, which has in vitro been shown to sensitize lymphoma cell lines for CHOP chemotherapy, and to upregulate CD20 expression. Based on these findings, we initiated a dose finding trial of valproate in combination with R-CHOP in primary treatment of diffuse large B-cell lymphoma (DLBCL), including a dose expansion cohort. Methods: Eligibility criteria were: age 18-80 years, histologically confirmed (according to the WHO classification) diffuse large B-cell lymphoma stage II-IV, WHO performance status 0-2. R-CHOP was given at standard dose in 14 or 21 day cycles, 6 cycles. Valproate was given in escalating doses days 1-3, starting at 10 mg/kg every 8 hrs, by a standard 3+3 design. Prednisone was given days 1-5, R-CHOP on day 3. Response was evaluated according to the Lugano criteria. Results: In the phase I portion, the MTD of valproate was established as 20 mg/kg every 8 hrs (total 60 mg/kg). At a dose of 80 mg/kg, 2 of 3 patie...
The enzyme glucose oxidase (GOx) was coupled to porous silicon of different morphologies and the ... more The enzyme glucose oxidase (GOx) was coupled to porous silicon of different morphologies and the catalytic turnover of glucose was recorded for the samples. The recorded catalytic turnover of the samples clearly indicated the in¯uence of morphology, with respect to dopant concentration and current density, of the porous silicon carrier matrix. The highest rise in catalytic turnover (350 times), when compared to a non-porous surface, was recorded for a sample with an n-type epilayer on an n 1-type substrate anodised at 100 mA/cm 2. A storage and operational stability measurement was performed on the sample showing the highest catalytic ef®ciency. After 5 months of refrigerated storage a 2% loss of activity was noted, and after 4 days of constant glucose load (0.5 mM) a 56% loss of activity was recorded. A BET (Brunauer, Emmet, and Teller) nitrogen adsorption analysis was performed on one of the substrate types, p 1-type (0.001±0.025 V cm). In spite of the ®ne porous morphology with a high surface area the recorded enzyme activities were moderate. The pore morphology achieved on this substrate most likely comprised too small pores in a too dense porous matrix giving poor diffusion conditions to give ef®cient access for the enzyme during the coupling procedure and for the reactant transport during operation to fully utilise the surface enlargement of the porous layer.
Enzyme reactors were fabricated on silicon wafers using microstructuring technologies. The reacto... more Enzyme reactors were fabricated on silicon wafers using microstructuring technologies. The reactors were made of several parallel vertically-cut flow channels. The reactor structures occupied a wafer area of 3 * 15 mm. Reactors with two different channel densities were fabricated: 10 channels/ mm, 165 /xm deep; and 25 channels/mm, 235 /~m deep. Glucose oxidase was immobilised on the reactors and their corresponding enzyme activities were monitored by a colourimetric assay. It was shown that a reactor surface area increase of 3 times gave rise to a proportional enzyme activity increase in the reactor. The maximum glucose turnover rate for the reactor with 25 channels/ mm was approximately 35 nmol/minute and the corresponding apparent Km was approximately 17 raM. A wafer integrated enzyme reactor was also operated in a microdialysis-based system for continuous glucose monitoring, showing a linear response up to 4 mM glucose.
Technology Transfer (TT) is on the rise in Europe with an increased focus on cooperation between ... more Technology Transfer (TT) is on the rise in Europe with an increased focus on cooperation between public research and the business community, as it enables good ideas and inventions to be transforme ...
The Journal of Hand Surgery: Journal of the British Society for Surgery of the Hand, 1997
SESSION 8 39 tion. We used this neurotization in traumatic cases but it is possibly applicable to... more SESSION 8 39 tion. We used this neurotization in traumatic cases but it is possibly applicable to complete palsies caused by ulnar entrapment at the elbow that cannot be improved by a simple neurolysis. We describe the assessment protocol, physiotherapy and operative regime and standardized functional review which we have instituted to maximize the hand and upper limb function of children with mucopolysaccharidoses and mucolipidoses.
Porous silicon is generated in five different silicon types of -orientation and the influence of ... more Porous silicon is generated in five different silicon types of -orientation and the influence of dopant type and dopant concentration with respect to ability to serve as an enzyme activated biocatalytic substrate. Glucose oxidase was immobilised onto the porous surfaces and a maximum increase in catalytic efficiency of 350 times was demonstrated. The influence of the depth of the porous layer was investigated, showing that an average porous depth of no more than 5–10 μm is optimal for the parallel channel structured micro enzyme reactors developed by our group.
Proceedings of 18th Annual International Conference of the IEEE Engineering in Medicine and Biology Society
Micro flow-through cells were fabricated in silicon and were designed to work as micro enzyme rea... more Micro flow-through cells were fabricated in silicon and were designed to work as micro enzyme reactors (columns) for glucose monitoring. The reactor design comprised a parallel channel structure with 32 channels, 50 μm wide. A reactor with vertical channels yields a much larger surface area than a corresponding v-groove channel structure. Therefore, (110) silicon was used to allow the fabrication
Porous silicon with its spongious structure and vast surface enlargement was investigated as the ... more Porous silicon with its spongious structure and vast surface enlargement was investigated as the carrier matrix for immobilised enzymes in micro enzyme reactors.
Proceedings of the International Solid-State Sensors and Actuators Conference - TRANSDUCERS '95
SUMMARY A micromashined flow-through cell for liquid sampling is presented. The flow channel is f... more SUMMARY A micromashined flow-through cell for liquid sampling is presented. The flow channel is formed by two 350 pn deep silicon basins facing each other with a 60 p diameter orifice in the centre of one of the basins. A piezo-ceramic disc glued to the silicon basin opposite the orifice controls the drop ejection in a drop-on-demand fashion. The ejected
The optimization of the catalytic performance of porous silicon enzyme microreactors with respect... more The optimization of the catalytic performance of porous silicon enzyme microreactors with respect to the reactor geometry is reported. The microreactors were fabricated in p-type silicon with anisotropic KOH-etching. To increase the effective area the silicon was made porous by anodisation in a HF-ethanol solution. The performance of the different reactors was evaluated by coupling glucose oxidase onto the porous matrix and measuring the catalytic turn-over rate.
The design and fabrication of a flow-through cell in <11O>-oriented silicon, which acts as a gluc... more The design and fabrication of a flow-through cell in <11O>-oriented silicon, which acts as a glucose oxidase enzyme reactor, is described. The reactor structure was made of several tall, parallel, standing walls, anisotropically etched in silicon, which occupies a wafer area of 3 * 15 mm 2. Reactors of two geometries were fabricated on the designated area, holding either 30 lamellre (165 11m tall, spaced 50 11m apart) or 75 lamellre (235 11m tall, spaced ",30 11m apart). Glucose oxidase was immobilised to the silicon surface available in the reactor. The lamella structure acted as an area enlarging geometry to achieve a high enzyme activity in the reactor. The two reactors exposed 172 mm 2 and 515 mm 2 of silicon surface respectively for the enzyme immobilisation. Enzyme activity determinations of the reactors showed that the reactor area increase yielded an increase in maximum glucose turnover rate from 10 nmol/min to ",37 nmol/min. The 515 mm 2 reactor was also operated in a system for continuous glucose monitoring, based on continuous glucose sampling via microdialysis. At a perfusion rate of 25 Ill/min, the system responded linearly to glucose levels between o and 5 mM after which the oxygen limitation affected the response.
Journal of Micromechanics and Microengineering, 1997
Miniaturization and silicon integration of micro enzyme reactors for applications in micro total ... more Miniaturization and silicon integration of micro enzyme reactors for applications in micro total analysis systems (µTASs) require new methods to achieve structures with a large surface area onto which the enzyme can be coupled. This paper describes a method to accomplish a highly efficient silicon microstructured enzyme reactor utilizing porous silicon as the carrier matrix. The enzyme activity of microreactors with a porous layer was recorded and compared with a microreactor without the porous layer. The microreactors were fabricated as flow-through cells comprising 32 channels, 50 µm wide, spaced 50 µm apart and 250 µm deep micromachined in 110 oriented silicon, p type (20-70 cm), by anisotropic wet etching. The overall dimension of the microreactors was 13.1 × 3.15 mm. To make the porous silicon layer, the reactor structures were anodized in a solution of hydrofluoric acid and ethanol. In order to evaluate the surface enlarging effect of different pore morphologies, the anodization was performed at three different current densities, 10, 50 and 100 mA cm −2. Glucose oxidase was immobilized onto the three porous microreactors and a non-porous reference reactor. The enzyme activity of the reactors was monitored following a colorimetric assay. To evaluate the glucose monitoring capabilities, the reactor anodized at 50 mA cm −2 was connected to an FIA system for glucose monitoring. The system displayed a linear response of glucose up to 15 mM using an injection volume of 0.5 µl. The result from the studies of glucose turnover rate clearly demonstrates the potential of porous silicon as a surface enlarging matrix for micro enzyme reactors. An increase in enzyme activity by a factor of 100, compared to the non-porous reference, was achieved for the reactor anodized at 50 mA cm −2 .
Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 1998
The performance of doped silicon and porous silicon as a new electrode material in neurophysiolog... more The performance of doped silicon and porous silicon as a new electrode material in neurophysiological applications is investigated. By increasing the surface area of adopted silicon region through anodisation in hydrofluoric acid it was found that the impedance parameters of the electrode were considerably improved. Impedance spectra of bare silicon electrodes, porous electrodes and platinum electroplated porous silicon electrodes are
Proceedings of 18th Annual International Conference of the IEEE Engineering in Medicine and Biology Society
Silicon membranes (diameter=4 mm, thickness=60 μm) with a circular matrix of holes centered at th... more Silicon membranes (diameter=4 mm, thickness=60 μm) with a circular matrix of holes centered at the chip were fabricated using anisotropic etching. The perforated area had a diameter of 2 mm. Three membrane geometries (hole sizes of 10, 50 or 100 μm) were investigated to find a suitable hole size for the nerve regeneration. The silicon membranes were mounted between two
The development of a miniaturised silicon wafer integrated enzyme reactor is described. The react... more The development of a miniaturised silicon wafer integrated enzyme reactor is described. The reactor was micromachined by anisotropic wet etching of (110) silicon. The enzyme glucose oxidase (GOx) was coupled to the reactor surface with standard methods of immobilising enzyme to silica. The glucose turn-over rate was monitored following a colourimetric assay. The advantage, in terms of high surface area per volume ratio, of utilising (110) silicon for microreactor fabrication compared to (100) silicon was demonstrated. Two reactors with different channel widths (50 and 20 µm) and channel densities (10 and 25 per millimetre) were compared, yielding a proportionally increased enzyme activity, for the reactor with the highest surface area (20 µm channels, 25 channels per millimetre). A novel method, utilising porous silicon as a coupling matrix, to increase the surface area for enzyme coupling was investigated. A porous silicon layer was fabricated on samples by anodic dissolution of si...
The influence of the carrier matrix depth and homogeneity was investigated for porous silicon enz... more The influence of the carrier matrix depth and homogeneity was investigated for porous silicon enzyme bioreactors. For the experiments h110i oriented silicon, p-type (20±70 W cm), was used. Porous silicon was generated on planar surfaces and on anisotropically pre-etched high aspect ratio parallel channel reactors. Samples were prepared with three depths, controlled by the anodisation time, and two current densities yielding different morphologies. In a second study, in order to make the porous layer more homogeneous, reactors were fabricated with different channel widths and wall thickness. Glucose oxidase (GO x) was immobilised onto the porous matrix following standard procedures for immobilisation of enzyme to silica. The enzyme activity of the samples was monitored following a colourimetric assay. The results clearly display the influence of the matrix depth for both the planar and the reactor structures. An 170-fold increase in catalytic turnover , when compared to an identical non-porous reference, was recorded for a reactor with an average porous depth of 10 mm. The importance of a homogeneous porous layer was illustrated, giving an increase in catalytic performance of three times between different structures with the same geometric area prior to anodisation.
The use of porous silicon (PS) as an efficient surface enlarging carrier matrix for immobilised e... more The use of porous silicon (PS) as an efficient surface enlarging carrier matrix for immobilised enzymes is demonstrated. An optimal porous matrix in p-type silicon (10±20 Wcm) with respect to enzymatic substrate turnover was obtained when anodising the sample at 100 mA/cm 2 for 5 min. An increase in glucose turnover of %220 times as compared to an enzyme activated polished surface was recorded. The highest increase in turnover was found to be 350 times for an n-epilayer on n + substrate. The application of glucose monitoring is demonstrated showing a linear range to 15 mM glucose with a satisfactory storage and operational stability. The use of ascorbate oxidase activated porous silicon for the elimination of ascorbate (an electrochemical interferent) in glutamate monitoring is reported. An upper elimination level of 1 mM ascorbate was found. PS is also reported as an efficient protein cleavage surface when activated with proteases. Cleavage times normally ranging between 6 and 24 h were found to be 60 s in the microreactor. Myoglobin cleaved on a trypsin microreactor is shown with the corresponding mass spectra having a sequence coverage of 79%.
Rationale: The anticonvulsant valproate is an HDAC inhibitor, which has in vitro been shown to se... more Rationale: The anticonvulsant valproate is an HDAC inhibitor, which has in vitro been shown to sensitize lymphoma cell lines for CHOP chemotherapy, and to upregulate CD20 expression. Based on these findings, we initiated a dose finding trial of valproate in combination with R-CHOP in primary treatment of diffuse large B-cell lymphoma (DLBCL), including a dose expansion cohort. Methods: Eligibility criteria were: age 18-80 years, histologically confirmed (according to the WHO classification) diffuse large B-cell lymphoma stage II-IV, WHO performance status 0-2. R-CHOP was given at standard dose in 14 or 21 day cycles, 6 cycles. Valproate was given in escalating doses days 1-3, starting at 10 mg/kg every 8 hrs, by a standard 3+3 design. Prednisone was given days 1-5, R-CHOP on day 3. Response was evaluated according to the Lugano criteria. Results: In the phase I portion, the MTD of valproate was established as 20 mg/kg every 8 hrs (total 60 mg/kg). At a dose of 80 mg/kg, 2 of 3 patie...
The enzyme glucose oxidase (GOx) was coupled to porous silicon of different morphologies and the ... more The enzyme glucose oxidase (GOx) was coupled to porous silicon of different morphologies and the catalytic turnover of glucose was recorded for the samples. The recorded catalytic turnover of the samples clearly indicated the in¯uence of morphology, with respect to dopant concentration and current density, of the porous silicon carrier matrix. The highest rise in catalytic turnover (350 times), when compared to a non-porous surface, was recorded for a sample with an n-type epilayer on an n 1-type substrate anodised at 100 mA/cm 2. A storage and operational stability measurement was performed on the sample showing the highest catalytic ef®ciency. After 5 months of refrigerated storage a 2% loss of activity was noted, and after 4 days of constant glucose load (0.5 mM) a 56% loss of activity was recorded. A BET (Brunauer, Emmet, and Teller) nitrogen adsorption analysis was performed on one of the substrate types, p 1-type (0.001±0.025 V cm). In spite of the ®ne porous morphology with a high surface area the recorded enzyme activities were moderate. The pore morphology achieved on this substrate most likely comprised too small pores in a too dense porous matrix giving poor diffusion conditions to give ef®cient access for the enzyme during the coupling procedure and for the reactant transport during operation to fully utilise the surface enlargement of the porous layer.
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Papers by Johan Drott