A LED-based cell irradiation system was built that can irradiate a 96-well plate with monochromatic light at controlled temperature and with a built-in dark control. This system was used to study the response of six human cancer cell lines to blue, green, and red light.
We successfully developed a hollow microneedle technology for dermal vaccination that enables fundamental research on factors, such as insertion depth and volume, and insertion angle, on the immune response.
The aim of this work was to develop a nanolayered pH sensitive coating method whereby proteins are coated at a suitable pH on the surface of chemically modified biomedical/bioanalytical microdevices and protein release is triggered by a pH-shift upon contact with the physiological environment. In this work such a coating was developed and was applied onto microneedles. First, the surface of microneedle arrays was modified with basic groups with a surface pK a below physiological pH. This modification was a multistep procedure: first the surface was hydroxylated in a piranha mixture, then 3-aminopropyltriethoxysilane was coupled (yielding a "pH independent" surface with a positive charge over a broad pH range), next 4-pyridinecarboxaldehyde was coupled to the obtained surface amine groups and finally the imine bond was reduced by sodium cyanoborohydride. The obtained pH-sensitive pyridinemodified microneedles were coated with ovalbumin at surface pK a > pH > pI of the protein; thus the surface of the microneedles is positively charged and the protein is negatively charged. The coating efficiency of ovalbumin was 95% for the amine-modified (pH independent) and the pyridine-modified (pH sensitive) surfaces, whereas a non-modified surface had a coating efficiency of only 2%. After the protein-coated microneedle arrays were pierced into the skin, having a pH > surface pK a of the microneedle arrays, 70% of the protein was released within 1 minute, whereas the protein release from pH independent microneedle arrays was only 5%. In conclusion, we developed a procedure to efficiently coat microneedle arrays with proteins that are released upon piercing into human skin.
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