Bio- and chemi-luminescent based biochemical sensors are being developed in a multi-well single use format for multi-analyte applications employing a single step, disposable, easy to use and interpret ChemChip.
We briefly review and summarize earlier and ongoing work.
We also argue for far more, rather than less or limited, chemical data in all areas, and particularly in education, health, and medicine.
A centrifugal-based microfluidic device<sup>1</sup> was built with lyophilized bioluminescent reagents for measuring multiple metabolites from a sample of less than 15 <i>μ</i>L. Microfluidic channels, reaction wells, and valves were cut in adhesive vinyl film using a knife plotter with features down to 30 <i>μ</i>m and transferred to metalized polycarbonate compact disks (CDs). The fabrication method was simple enough to test over 100 prototypes within a few months. It also allowed enzymes to be packaged in microchannels without exposure to heat or chemicals. The valves were rendered hydrophobic using liquid phase deposition. Microchannels were patterned using soft lithography to make them hydrophilic. Reagents and calibration standards were deposited and lyophilized in different wells before being covered with another adhesive film. Sample delivery was controlled by a modified CD ROM. The CD was capable of distributing 200 nL sample aliquots to 36 channels, each with a different set of reagents that mixed with the sample before initiating the luminescent reactions. Reflection of light from the metalized layer and lens configuration allowed for 20% of the available light to be collected from each channel. ATP was detected down to 0.1 <i>μ</i>M. Creatinine, glucose, and galactose were also measured in micro and milliMolar ranges. Other optical-based analytical assays can easily be incorporated into the device design. The minimal sample size needed and expandability of the device make it easier to simultaneously measure a variety of clinically relevant analytes in point-of-care settings.
Proteins absorb to almost all surfaces during the first few minutes of exposure. Surfaces that show minimal protein absorption are important in many biomedical applications. Moreover, patient discomfort due to poor lubricating action between tissue and various medical devices, especially contact lenses, is a serious medical problem. An effective polymer for protein- resistant surfaces and improved lubrication properties appears to be polyethylene oxide (PEO). Here we report a study of PEO films on low temperature isotropic (LTI) carbon surfaces, including preparation using a photochemical reaction, characterization of the thickness of the PEO layer by ellipsometry and measurement of coefficient of friction with a custom built tribometer.
Ellipsometry is widely used for investigating the optical properties of thin films on planar substrates,
including films of adsorbed proteins or polymers. The average thickness and effective refractive index of the
adsorbed layer are calculated by measuring the A and 'P ellipsometry parameters. Unfortunately the thickness
of the adsorbed protein layers is often too thin to significantly affect the and 'I' parameters. However, using a
substructure consisting of an additional sublayer placed between the substrate and the adsorbed layer, we can
improve the sensitivities of both and 'P to changes in the adsorbed layer, provided that the thickness of the
sublayer is optimized. We show that for a Si02 layer on a Si wafer, the optimum Si02 thickness is about 1350
A when the incident angle is 70 degrees and the wavelength is 6328 A. The materials of the sublayer can be
metal, semiconductor and/or dielectric.