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Biomedical subjects

M J Vellekoop

Publications and source records attributed to M J Vellekoop.

4 recordsLinked to original sources

Towards biochemical reaction monitoring using FT-IR synchrotron radiation.

A lab-on-a-chip device made of CaF2 windows and SU-8 polymer was used for fluid lamination to achieve rapid mixing of two streamlines with a cross section of 300 x 5 microm each. Time resolved measurements of the induced chemical reaction was achieved by applying constant feeding low flow rates and by on-chip measurement at defined distances after the mixing point. Synchrotron IR microscopic detection was employed for direct and label-free monitoring of (bio)chemical reactions. Furthermore, using synchrotron IR microscopy the measurement spot could be reduced to the diffraction limit, thus maximizing time resolution in the experimental set-up under study. Based on computational fluid dynamic simulations the principle of the set-up is discussed. Experimental results on the basic hydrolysis of methyl chloroacetate proved the working principle of the experimental set-up. First results on the interaction between the antibiotic vancomycin and a tripeptide (Ac2KAA) involved in the build up of the membrane proteins of gram-positive bacteria are presented.

Animals↗

Time-resolved Fourier transform infrared spectroscopy of chemical reactions in solution using a focal plane array detector.

A Fourier transform infrared (FT-IR) microscope equipped with a single as well as a 64 x 64 element focal plane array MCT detector was used to measure chemical reaction taking place in a microstructured flow cell designed for time-resolved FT-IR spectroscopy. The flow cell allows transmission measurements through aqueous solutions and incorporates a microstructured mixing unit. This unit achieves lamination of the two input streams with a cross-section of 300 x 5 microm each, resulting in fast diffusion-controlled mixing of the two input streams. Microscopic measurement at defined positions along the outlet channel allows time-resolved information of the reaction taking place in the flow cell to be obtained. In this paper we show experimental results on the model reaction between formaldehyde and sulfite. Using the single-point MCT detector, high-quality FT-IR spectra could be obtained from a spot size of 80 x 200 microm whereas the FPA detector allowed recording light from an area of 260 x 260 microm focused on its 64 x 64 detector elements. Therefore, more closely spaced features could be discerned at the expense of a significantly lower signal-to-noise (S/N) ratio per spectrum. Multivariate curve resolution-alternating least squares was used to extract concentration profiles of the reacting species along the outlet channel axis.

Journal Article↗

Mid-IR synchrotron radiation for molecular specific detection in microchip-based analysis systems.

Microstructures constructed from SU-8 polymer and produced on CaF(2) base plates have been developed for microchip-based analysis systems used to perform FTIR spectroscopic detection using mid-IR synchrotron radiation. The high brilliance of the synchrotron source enables measurements at spot sizes at the diffraction limit of mid-IR radiation. This corresponds to a spatial resolution of a few micrometers (5-20 microm). These small measurement spots are useful for lab-on-a-chip devices, since their sizes are comparable to those of the structures usually used in these devices. Two different types of microchips are introduced here. The first chip was designed for time-resolved FTIR investigations of chemical reactions in solution. The second chip was designed for chip-based electrophoresis with IR detection on-chip. The results obtained prove the operational functionality of these chips, and indicate the potential of these new devices for further applications in (bio)analytical chemistry.

Journal Article↗

Integrated flow-cells for novel adjustable sheath flows.

In this paper two integrated flow-cells are presented that can generate novel sheath flows. The flow-cells allow for dynamic orthogonal control of the sample flow dimensions. In addition to this, the sample flow can be freely positioned inside the channel. The flow-cells are attractive, because they are very simple to fabricate and are compatible with the integration of sensors. Experiments have been carried out demonstrating that the sample flow dimensions can be controlled over a wide range; also the results show good agreement with finite element simulation results.

Biosensing Techniques↗