@article{KagelFrohmeGloekler2018, author = {Kagel, Heike and Frohme, Marcus and Gl{\"o}kler, J{\"o}rn}, title = {Photoacids in biochemical applications}, series = {Journal of Cellular Biotechnology}, volume = {4}, journal = {Journal of Cellular Biotechnology}, number = {1-2}, publisher = {IOS Press}, issn = {2352-3697}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-16123}, pages = {23 -- 30}, year = {2018}, abstract = {BACKGROUND: After excitation with light photoacids can change the pH in a solution by release of a proton. They have been used mostly for excited state proton transfer studies. In this review the general functionality and mechanisms and the subdivision of photoacids is explained. STATE OF THE ART: Different uses of photoacids are described, covering a wide range of various biochemical topics, focusing on biochemical applications. Examples for the introduced subdivisions are covered. CONCLUSIONS AND OUTLOOK: The areas in which photoacids can be employed are diverse. Photoacids have a promising future in biotechnology and biochemistry and should be considered for upcoming applications, especially in non-invasive control of biochemical reactions.}, language = {en} } @inproceedings{KagelHonselmannGenanntHummeRosaetal.2015, author = {Kagel, Heike and Honselmann Genannt Humme, Julia and Rosa, Edvaldo Antonio Ribeiro and Turchiello, Rozane de F{\´a}tima and Bezerra Junior, Arandi Ginane}, title = {Plasmonic enhancement in the photoinactivation of Escherichia Coli using rose bengal and gold nanoparticles}, series = {Proc. SPIE 9531, Biophotonics South America, 953138 (19 June 2015)}, booktitle = {Proc. SPIE 9531, Biophotonics South America, 953138 (19 June 2015)}, issn = {1996-756X}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-14828}, year = {2015}, abstract = {In the present study we report on the ability of gold nanoparticles (AuNP) to enhance the antimicrobial activity of the photosensitizer Rose Bengal (RB), a very effective singlet oxygen generator. Our experiments were conducted using a suspension of Escherichia Coli in the presence of either RB or a combination of RB and AuNP. Nanoparticles were synthesized by laser ablation in water, which allows high purity, biologically friendly AuNP production, as compared to traditional chemical methods. Several relative concentrations of bacteria, photosensitizes and AuNP were studied. Bacterial survival rates were determined before and after LED light illumination. The phototoxicity of RB with and without AuNP was checked following illumination for 10 and 20 minutes. As a control, the dark toxicity of RB was verified. The results show that the survival rate of bacteria decreases significantly with the increase of RB concentration and illumination time, which is in accordance with previous works. Interestingly, our results also indicate a significant increase in the lethal photosensitization of RB in the presence of AuNP. We propose this effect is due to plasmonic light enhancement, considering the superposition of RB and AuNP absorption spectra, which favors electric field enhancement effects in the presence of AuNP. Similar experiments using the photosensitizer Methylene Blue (MB) allowed us to test our hypothesis for MB did not show any difference in its phototoxicity in the presence of AuNP. We propose this observed synergistic effect could be an effective way for improving photodynamic inactivation of microorganisms.}, language = {en} } @article{KagelBierFrohmeetal.2019, author = {Kagel, Heike and Bier, Frank Fabian and Frohme, Marcus and Gl{\"o}kler, J{\"o}rn}, title = {A Novel Optical Method To Reversibly Control Enzymatic Activity Based On Photoacids}, series = {Scientific Reports}, volume = {9}, journal = {Scientific Reports}, issn = {2045-2322}, doi = {10.1038/s41598-019-50867-w}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-12685}, year = {2019}, abstract = {Most biochemical reactions depend on the pH value of the aqueous environment and some are strongly favoured to occur in an acidic environment. A non-invasive control of pH to tightly regulate such reactions with defined start and end points is a highly desirable feature in certain applications, but has proven difficult to achieve so far. We report a novel optical approach to reversibly control a typical biochemical reaction by changing the pH and using acid phosphatase as a model enzyme. The reversible photoacid G-acid functions as a proton donor, changing the pH rapidly and reversibly by using high power UV LEDs as an illumination source in our experimental setup. The reaction can be tightly controlled by simply switching the light on and off and should be applicable to a wide range of other enzymatic reactions, thus enabling miniaturization and parallelization through non-invasive optical means.}, language = {en} } @article{KagelJacobsBieretal.2019, author = {Kagel, Heike and Jacobs, Hannes and Bier, Frank Fabian and Gl{\"o}kler, J{\"o}rn and Frohme, Marcus}, title = {A Novel Microtiter Plate Format High Power Open Source LED Array}, series = {Photonics}, volume = {6}, journal = {Photonics}, number = {1}, issn = {2304-6732}, doi = {10.3390/photonics6010017}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-11307}, year = {2019}, abstract = {Many photochemical or photobiological applications require the use of high power ultraviolet light sources, such as high-pressure mercury arc lamps. In addition, many photo-induced chemical, biochemical and biological applications require either a combinatorial setting or a parallel assay of multiple samples under the same environmental conditions to ensure reproducibility. To achieve this, alternative, controllable light sources, such as ultraviolet light emitting diodes (UV LEDs) with high power and spatial control are required. Preferably, LEDs are arranged in a suitable standardized 96-well microtiter plate format. We designed such an array and established the methods required for heat management and enabling stable, controllable illumination over time.}, language = {en} }