A method for synthesis and evaluation of molecularly imprinted polymers (MIPs) on a semiautomated... more A method for synthesis and evaluation of molecularly imprinted polymers (MIPs) on a semiautomated miniature scale is reported. This technique combines molecular imprinting with the combinatorial chemistry approach, allowing rapid screening and optimizations of libraries of MIPs. The polymers were prepared and evaluated in situ by rebinding utilizing powder dispensing and liquid handling systems. MIPs were prepared by a combinatorial approach using methacrylic acid (MAA), 4-vinylpyridine (4-VP), acrylamide, and styrene as functional monomers, and acetonitrile and toluene as porogenic solvents. A drug substance having aromatic, hydroxyl,-O-CONH 2 functional groups was selected as the template molecule for this study. The MIP library results demonstrated that the polymer prepared with MAA as functional monomer shows the strongest binding affinity, and therefore, is preferred for the preparation of this particular template molecule. Due to the low consumption of reagents, and more importantly, the demonstrated ability of this method to effectively identify optimal imprinting conditions, this small-scale combinatorial protocol is well suited for fast and efficient screening and optimizations of MIPs.
We report the fabrication of carbon nanotube field-effect transistors for biosensing applications... more We report the fabrication of carbon nanotube field-effect transistors for biosensing applications and the development of protocols for reliable protein and DNA sensing. The sensing method we employ is 'label free', relying only on the intrinsic charge of the biological molecule of interest. We discuss fabrication issues that we have solved, for example the preparation of clean surfaces, and the sensing protocol issues that we have encountered. Polylysine and ss-dna, highly charged biological molecules, are used as model systems to illustrate the performance of our biosensors.
Capillary electrophoresis (CE) coupled with UV absorbance detection has been applied as an analys... more Capillary electrophoresis (CE) coupled with UV absorbance detection has been applied as an analysis tool for carbon dots (C-dots), which were hydrothermally synthesized from precursors citric acid (CA) and ethylene diamine (EDA). An alkaline working buffer (100mM tris acetate, pH 8.4) was found to be optimal for rapid and reliable analysis of C-dots. A calibration curve was established over a broad concentration range (0.5-10mg/mL) with excellent linearity (R2=0.9989). The CE method was also applied to enhance understanding of and facilitate optimization of ensuing C-dot biolabeling reactions. The novel CE method was used to confirm and quantify production of C-dot labeled antibodies. The optimum concentration of antibody for use in the labeling reaction was determined.
Polymer−inorganic nanocomposites are a recently developed class of materials that have altered ph... more Polymer−inorganic nanocomposites are a recently developed class of materials that have altered physical or chemical properties with respect to the pure polymer, inorganic host, or their micro-and macrocomposites. Lower generation (G0.0−2.0) polyamidoamine (PAMAM) dendrimer/sodium montmorillonite (Na-MMT) nanocomposites were synthesized in a solution-phase exfoliation adsorption reaction. These are the first reports of the G0.0/ and G1.0/Na-MMT nanocomposites and of a structurallyordered G2.0/Na-MMT. The materials were characterized using powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FTIR). PAMAM characteristics at acidic and basic aqueous media were studied using capillary zone electrophoresis (CZE). Pseudospherical PAMAM dendrimers in aqueous medium attain a highly flattened conformation within the confined space between MMT sheets upon nanocomposite formation. The nanocomposite structure depends on the PAMAM generation and the starting dendrimer/ organic composition. G0.0 always forms monolayer structures (d = 0.42 nm), while G2.0 forms monolayer structure, mixed phase, and bilayer structures (d = 0.84 nm) at lower, intermediate, and higher organic content, respectively, showing an interesting monolayer to bilayer transition. G1.0 showed an intermediate behavior, with monolayer to mixed-phase transition at the reactant ratios studied. This monolayer arrangement of PAMAM/clay nanocomposites is reported for the first time. Maximum organic contents of G0.0 monolayer and G2.0 bilayer nanocomposites were ∼7% and ∼14%, respectively. Gallery expansions were similar to those observed with linear polymer intercalates, but the packing fractions (0.31−0.32) were 2−3 times lower. At acidic pH, the nanocomposites forming only monolayer structures are obtained, indicating a stronger electrostatic attraction between MMT and protonated PAMAM, and these nanocomposites formed more slowly and were more ordered. Na + ions play a significant role in nanocomposite formation. At high pH, PAMAMs show high mobility, ζ potential, and surface charge densities due to Na + complexation in solution. FTIR data indicates that both Na-MMT and PAMAM structural units are preserved in the nanocomposites obtained.
This work presents the design and characterization of the individual microfluidic instrument comp... more This work presents the design and characterization of the individual microfluidic instrument components to be used for an integrated micro-total-analysis device for in-situ, colorimetric, water quality monitoring. Components include a microfabricated filter, a passive micromixer, a 1-cm pathlength microfluidic absorbance flow cell, mini-motor driven peristaltic micropumps with normally-closed valving capacity, a miniature collapsible reagent storage bag, and compact waterproof packaging. Preliminary development of the integrated device employing a miniature spectrometer is also presented.
Separation of blood plasma or serum from blood is essential for accurate analysis. Conventional b... more Separation of blood plasma or serum from blood is essential for accurate analysis. Conventional blood separation requires instrumentation, reagents, and large sample volumes, limiting this process to laboratory environments with trained personnel. Full implementation of effective blood separation and analysis on microliter sample volumes for point of care (POC) diagnostics has proven extremely challenging resulting in a growing market demand, with common challenges such as expensive device fabrication processes or devices being comprised of materials which are not easily disposable. We developed a membrane-based wicking microfluidic device which is made using a simple fabrication process. This device uses a unique 3D flow channel geometry, fabricated in a polycaprolactone-filled glass microfiber membrane, to efficiently separate microliter sample volumes of blood. Colorimetric assay chemistries were integrated to demonstrate utility of these devices in POC diagnostics. The devices are capable of separating both fresh and anticoagulant-treated blood at microscale sample volumes (<15.0 μL). Modifications to the base device are also reported herein which increased sample volume capacity and separation efficiency. Integrated colorimetric assay enabled semi-quantitative detection of conjugated bilirubin in real blood samples (1.0–1.5 mg/dL). These blood separation devices, fabricated on polycaprolactone-filled glass microfiber, enabled effective blood plasma (anticoagulant-treated blood) and serum (fresh blood) separation with microscale sample volumes. Sample volume capacity and separation efficiency are customizable for specific applications and devices can be integrated with downstream assay chemistries to develop complete POC devices that offer blood separation and diagnostics at the same time on a single membrane.
A paper-based analytical device (PAD) with an integrated composite electrode for non-enzymatic cr... more A paper-based analytical device (PAD) with an integrated composite electrode for non-enzymatic creatinine sensing was developed. The electrode was produced and optimization was efficiently accomplished using a rapid digital dispensing approach. The electrochemical sensor was fabricated using an HP D300 digital dispenser to deliver a copper oxide and ionic liquid composite onto an electrochemically reduced graphene modified screen-printed carbon electrode (CuO/IL/ERGO/SPCE) on a PAD. The modified electrode was characterized using electrochemical and microscopic techniques. Electrochemical detection of creatinine was performed on the SPCE using amperometry at a constant potential. Under optimized conditions, the paper-based sensor exhibited a linear range of 0.01-2.0 mM (R2 = 0.99) and the limit of detection was 0.22 μM (S/N = 3, IUPAC definition) for creatinine. The simple fabrication process, low cost, and clinically appropriate creatinine sensitivity make this device applicable for point-of-care use.
The MICRO project has developed a series of active-learning labs that can be safely delivered to ... more The MICRO project has developed a series of active-learning labs that can be safely delivered to students either at home or in person using paper microfluidic technology. The skills covered in these labs are appropriate for sophomore-level analytical chemistry courses and general chemistry.
Patterning within a polymer-encapsulated porous fluidic layer, achieved via selective in situ las... more Patterning within a polymer-encapsulated porous fluidic layer, achieved via selective in situ laser ablation arising from different optical transmission properties.
Methods such as capillary electrophoresis (CE) and capillary liquid chromatography (LC) are parti... more Methods such as capillary electrophoresis (CE) and capillary liquid chromatography (LC) are particularly useful in the analysis of complex mixtures because of their high resolving power. Continued refinement of these techniques has led to a novel separation method known as capillary electrochromatography (CEC), also referred to as capillary electrokinetic chromatography, which is a combination of capillary LC and conventional CE. As in LC, mobile phase is transported through a column where partitioning of solutes occurs. In CEC, mobile phase flow is generated by electroosmosis, which arises when an electric potential is applied across the long axis of the capillary column. The favorable flow dynamics of electroosmosis result in higher chromatographic efficiencies in CEC relative to LC. If the species of interest are charged, a second separation mechanism is afforded by electrophoresis. CEC combines the high efficiency of capillary electrophoretic separations with the broad range of ...
A method for synthesis and evaluation of molecularly imprinted polymers (MIPs) on a semiautomated... more A method for synthesis and evaluation of molecularly imprinted polymers (MIPs) on a semiautomated miniature scale is reported. This technique combines molecular imprinting with the combinatorial chemistry approach, allowing rapid screening and optimizations of libraries of MIPs. The polymers were prepared and evaluated in situ by rebinding utilizing powder dispensing and liquid handling systems. MIPs were prepared by a combinatorial approach using methacrylic acid (MAA), 4-vinylpyridine (4-VP), acrylamide, and styrene as functional monomers, and acetonitrile and toluene as porogenic solvents. A drug substance having aromatic, hydroxyl,-O-CONH 2 functional groups was selected as the template molecule for this study. The MIP library results demonstrated that the polymer prepared with MAA as functional monomer shows the strongest binding affinity, and therefore, is preferred for the preparation of this particular template molecule. Due to the low consumption of reagents, and more importantly, the demonstrated ability of this method to effectively identify optimal imprinting conditions, this small-scale combinatorial protocol is well suited for fast and efficient screening and optimizations of MIPs.
We report the fabrication of carbon nanotube field-effect transistors for biosensing applications... more We report the fabrication of carbon nanotube field-effect transistors for biosensing applications and the development of protocols for reliable protein and DNA sensing. The sensing method we employ is 'label free', relying only on the intrinsic charge of the biological molecule of interest. We discuss fabrication issues that we have solved, for example the preparation of clean surfaces, and the sensing protocol issues that we have encountered. Polylysine and ss-dna, highly charged biological molecules, are used as model systems to illustrate the performance of our biosensors.
Capillary electrophoresis (CE) coupled with UV absorbance detection has been applied as an analys... more Capillary electrophoresis (CE) coupled with UV absorbance detection has been applied as an analysis tool for carbon dots (C-dots), which were hydrothermally synthesized from precursors citric acid (CA) and ethylene diamine (EDA). An alkaline working buffer (100mM tris acetate, pH 8.4) was found to be optimal for rapid and reliable analysis of C-dots. A calibration curve was established over a broad concentration range (0.5-10mg/mL) with excellent linearity (R2=0.9989). The CE method was also applied to enhance understanding of and facilitate optimization of ensuing C-dot biolabeling reactions. The novel CE method was used to confirm and quantify production of C-dot labeled antibodies. The optimum concentration of antibody for use in the labeling reaction was determined.
Polymer−inorganic nanocomposites are a recently developed class of materials that have altered ph... more Polymer−inorganic nanocomposites are a recently developed class of materials that have altered physical or chemical properties with respect to the pure polymer, inorganic host, or their micro-and macrocomposites. Lower generation (G0.0−2.0) polyamidoamine (PAMAM) dendrimer/sodium montmorillonite (Na-MMT) nanocomposites were synthesized in a solution-phase exfoliation adsorption reaction. These are the first reports of the G0.0/ and G1.0/Na-MMT nanocomposites and of a structurallyordered G2.0/Na-MMT. The materials were characterized using powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FTIR). PAMAM characteristics at acidic and basic aqueous media were studied using capillary zone electrophoresis (CZE). Pseudospherical PAMAM dendrimers in aqueous medium attain a highly flattened conformation within the confined space between MMT sheets upon nanocomposite formation. The nanocomposite structure depends on the PAMAM generation and the starting dendrimer/ organic composition. G0.0 always forms monolayer structures (d = 0.42 nm), while G2.0 forms monolayer structure, mixed phase, and bilayer structures (d = 0.84 nm) at lower, intermediate, and higher organic content, respectively, showing an interesting monolayer to bilayer transition. G1.0 showed an intermediate behavior, with monolayer to mixed-phase transition at the reactant ratios studied. This monolayer arrangement of PAMAM/clay nanocomposites is reported for the first time. Maximum organic contents of G0.0 monolayer and G2.0 bilayer nanocomposites were ∼7% and ∼14%, respectively. Gallery expansions were similar to those observed with linear polymer intercalates, but the packing fractions (0.31−0.32) were 2−3 times lower. At acidic pH, the nanocomposites forming only monolayer structures are obtained, indicating a stronger electrostatic attraction between MMT and protonated PAMAM, and these nanocomposites formed more slowly and were more ordered. Na + ions play a significant role in nanocomposite formation. At high pH, PAMAMs show high mobility, ζ potential, and surface charge densities due to Na + complexation in solution. FTIR data indicates that both Na-MMT and PAMAM structural units are preserved in the nanocomposites obtained.
This work presents the design and characterization of the individual microfluidic instrument comp... more This work presents the design and characterization of the individual microfluidic instrument components to be used for an integrated micro-total-analysis device for in-situ, colorimetric, water quality monitoring. Components include a microfabricated filter, a passive micromixer, a 1-cm pathlength microfluidic absorbance flow cell, mini-motor driven peristaltic micropumps with normally-closed valving capacity, a miniature collapsible reagent storage bag, and compact waterproof packaging. Preliminary development of the integrated device employing a miniature spectrometer is also presented.
Separation of blood plasma or serum from blood is essential for accurate analysis. Conventional b... more Separation of blood plasma or serum from blood is essential for accurate analysis. Conventional blood separation requires instrumentation, reagents, and large sample volumes, limiting this process to laboratory environments with trained personnel. Full implementation of effective blood separation and analysis on microliter sample volumes for point of care (POC) diagnostics has proven extremely challenging resulting in a growing market demand, with common challenges such as expensive device fabrication processes or devices being comprised of materials which are not easily disposable. We developed a membrane-based wicking microfluidic device which is made using a simple fabrication process. This device uses a unique 3D flow channel geometry, fabricated in a polycaprolactone-filled glass microfiber membrane, to efficiently separate microliter sample volumes of blood. Colorimetric assay chemistries were integrated to demonstrate utility of these devices in POC diagnostics. The devices are capable of separating both fresh and anticoagulant-treated blood at microscale sample volumes (<15.0 μL). Modifications to the base device are also reported herein which increased sample volume capacity and separation efficiency. Integrated colorimetric assay enabled semi-quantitative detection of conjugated bilirubin in real blood samples (1.0–1.5 mg/dL). These blood separation devices, fabricated on polycaprolactone-filled glass microfiber, enabled effective blood plasma (anticoagulant-treated blood) and serum (fresh blood) separation with microscale sample volumes. Sample volume capacity and separation efficiency are customizable for specific applications and devices can be integrated with downstream assay chemistries to develop complete POC devices that offer blood separation and diagnostics at the same time on a single membrane.
A paper-based analytical device (PAD) with an integrated composite electrode for non-enzymatic cr... more A paper-based analytical device (PAD) with an integrated composite electrode for non-enzymatic creatinine sensing was developed. The electrode was produced and optimization was efficiently accomplished using a rapid digital dispensing approach. The electrochemical sensor was fabricated using an HP D300 digital dispenser to deliver a copper oxide and ionic liquid composite onto an electrochemically reduced graphene modified screen-printed carbon electrode (CuO/IL/ERGO/SPCE) on a PAD. The modified electrode was characterized using electrochemical and microscopic techniques. Electrochemical detection of creatinine was performed on the SPCE using amperometry at a constant potential. Under optimized conditions, the paper-based sensor exhibited a linear range of 0.01-2.0 mM (R2 = 0.99) and the limit of detection was 0.22 μM (S/N = 3, IUPAC definition) for creatinine. The simple fabrication process, low cost, and clinically appropriate creatinine sensitivity make this device applicable for point-of-care use.
The MICRO project has developed a series of active-learning labs that can be safely delivered to ... more The MICRO project has developed a series of active-learning labs that can be safely delivered to students either at home or in person using paper microfluidic technology. The skills covered in these labs are appropriate for sophomore-level analytical chemistry courses and general chemistry.
Patterning within a polymer-encapsulated porous fluidic layer, achieved via selective in situ las... more Patterning within a polymer-encapsulated porous fluidic layer, achieved via selective in situ laser ablation arising from different optical transmission properties.
Methods such as capillary electrophoresis (CE) and capillary liquid chromatography (LC) are parti... more Methods such as capillary electrophoresis (CE) and capillary liquid chromatography (LC) are particularly useful in the analysis of complex mixtures because of their high resolving power. Continued refinement of these techniques has led to a novel separation method known as capillary electrochromatography (CEC), also referred to as capillary electrokinetic chromatography, which is a combination of capillary LC and conventional CE. As in LC, mobile phase is transported through a column where partitioning of solutes occurs. In CEC, mobile phase flow is generated by electroosmosis, which arises when an electric potential is applied across the long axis of the capillary column. The favorable flow dynamics of electroosmosis result in higher chromatographic efficiencies in CEC relative to LC. If the species of interest are charged, a second separation mechanism is afforded by electrophoresis. CEC combines the high efficiency of capillary electrophoretic separations with the broad range of ...
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