Mikromanipulációs kísérletek lézercsipesszel = Micromanipulation experiments with optical tweezers

A kutatás az optikai mikromanipuláció területén, különböző irányokban végzett fejlesztéseket és kutatási alkalmazásokat képviselt. A mikromanipuláció területén azt vizsgáltuk, milyen új manipulációs lehetőségeket nyújtanak speciális alakú próbatestek (ellentétben az általáéban használt gömb alakkal). Ennek során kidolgoztuk a lézeres fotopolimerizációs struktúra építés technikáját. Ezzel egyrészt a mikromanipuláció új lehetőségeit vizsgáltuk. Például, lehetőség nyílik torziós manipulálásra, csavarásra, meghatároztuk a DNS molekula torziós rugalmasságát. Ezen kívül, bonyolult struktúrákat építettünk, fénnyel hajtott mikrogépeket, mikrofluidikai csatornákat, integrált optikai szenzorokat. Ezekből bonyolultab összetett rendszereket raktunk össze: fénnyel vezérelt fluorescencia aktivált optikai sejtszeparátort. Kidolgoztuk a fénnyel vezérelt elektroozmózis eljárását. Itt elektromos térrel mozgatott folyadék áramlását vezéreljük fénnyel, ez érdekes jelenség, és új lehetőségeket nyújt mikrofluidikai rendszerek vezérlésében. | The research represented studies in the area of optical micromanipulation, both developing new procedures and basic applications. In the area of micromanipulation we investigated, what new possibilities are offered by test objects of special shapes (as opposed to the generally used spheres). In this process we developed the structure building by laser induced photopolymerization. With this we studied new possibilities of optical manipulation. For example, a poissibility emerges for torsional manipulation, twisting, we determined the torsional elasticity of DNA molecules. In addition, we built complex structures, light driven micromachines, microfluidics channels, integrated optical sensors. From this we constructed complex systems, e.g. a fluorescence activated cell separator. We developed the method of optically controlled electroosmosis. Here the fluid is driven by electric field and this is controlled by light. This is an interesting phenomenon, and is opens new possibilities in the control of microfluidics systems

On-line characterization of nanoparticles by single particle ICP-MS utilizing microfluidic devices

In this study, polydimethylsiloxane (PDMS) - glass microfluidic chips (MCs) were designed and fabricated using moulds prepared by a professional 3D printer. The prepared chips were used for the dilution, counting and characterization of nanoparticles (NPs) performing single particle inductively coupled plasma mass spectrometry (spICP-MS) measurements

Multifunctional microfluidic chips for the single particle inductively coupled plasma mass spectrometry analysis of inorganic nanoparticles

This study aimed at exploiting the so far unexploited potential of carrying out on-line sample pretreatment steps on microfluidic chips for single particle inductively coupled plasma mass spectrometry (spICP-MS) measurements, and demonstrating their ability to practically facilitate most of the simpler tasks involved in the spICP-MS analysis of nanoparticles. For this purpose, polydimethylsiloxane microfluidic chips, capable of high-range dilution and sample injection were made by casting, using high-precision, 3D-printed molds. Optimization of their geometry and functions was done by running several hydrodynamic simulations and by gravimetric, fluorescence enhanced microscope imaging and solution-based ICP-MS experiments. On the optimized microfluidic chips, several experiments were done, demonstrating the benefits of the approach and these devices, such as the determination of nanoparticle concentration using only a few tens of microliters of sample, elimination of solute interferences by dilution, solution-based size calibration and characterisation of binary nanoparticles. Due to the unique design of the chips, they can be linked together to extend the dilution range of the system by more than a magnitude per chip. This feature was also demonstrated in applications requiring multiple-magnitude dilution rates, when two chips were sequentially couple

Optimization of flow control and channel patterns designed for use in sequentially coupled microfluidic chips and nanoparticle characterization by single particle ICP-MS

In this study, we developed polydimethylsiloxane (PDMS) - glass microfluidic chips (MCs) with the ability to function in a sequentially coupled way. We optimized their channel pattern and demonstrated that this feature makes them a more effective tool for carrying out sample preparation steps in single particle inductively coupled plasma mass spectrometry (spICP-MS) such as dilution, counting, and characterization of nanoparticles (NPs)

Microfluidic study of the chemotactic response of Escherichia coli to amino acids, signaling molecules and secondary metabolites

Quorum sensing and chemotaxis both affect bacterial behavior on the population level. Chemotaxis shapes the spatial distribution of cells, while quorum sensing realizes a cell-density dependent gene regulation. An interesting question is if these mechanisms interact on some level: Does quorum sensing, a density dependent process, affect cell density itself via chemotaxis? Since quorum sensing often spans across species, such a feedback mechanism may also exist between multiple species. We constructed a microfluidic platform to study these questions. A flow-free, stable linear chemical gradient is formed in our device within a few minutes that makes it suitable for sensitive testing of chemoeffectors: we showed that the amino acid lysine is a weak chemoattractant for Escherichia coli, while arginine is neutral. We studied the effect of quorum sensing signal molecules of Pseudomonas aeruginosa on E. coli chemotaxis. Our results show that N-(3-oxododecanoyl)-homoserine lactone (oxo-C12-HSL) and N-(butryl)-homoserine lactone (C4-HSL) are attractants. Furthermore, we tested the chemoeffector potential of pyocyanin and pyoverdine, secondary metabolites under a quorum sensing control. Pyocyanin is proved to be a weak attractant while pyoverdine are repellent. We demonstrated the usability of the device in co-culturing experiments, where we showed that various factors released by P. aeruginosa affect the dynamic spatial rearrangement of a neighboring E. coli population, while surface adhesion of the cells is also modulated. © 2015 AIP Publishing LLC

Nonlinear Optical Investigation of Microbial Chromoproteins

Membrane-bound or cytosolic light-sensitive proteins, playing a crucial role in energy- and signal-transduction processes of various photosynthetic microorganisms, have been optimized for sensing or harvesting light by myriads of years of evolution. Upon absorption of a photon, they undergo a usually cyclic reaction series of conformations, and the accompanying spectro-kinetic events assign robust nonlinear optical (NLO) properties for these chromoproteins. During recent years, they have attracted a considerable interest among researchers of the applied optics community as well, where finding the appropriate NLO material for a particular application is a pivotal task. Potential applications have emerged in various branches of photonics, including optical information storage and processing, higher-harmonic and white-light continuum generation, or biosensorics. In our earlier work, we also raised the possibility of using chromoproteins, such as bacteriorhodopsin (bR), as building blocks for the active elements of integrated optical (IO) circuits, where several organic and inorganic photonic materials have been considered as active components, but so far none of them has been deemed ideal for the purpose. In the current study, we investigate the linear and NLO properties of biofilms made of photoactive yellow protein (PYP) and bR. The kinetics of the photoreactions are monitored by time-resolved absorption experiments, while the refractive index of the films and its light-induced changes are measured using the Optical Waveguide Lightmode Spectroscopy (OWLS) and Z-scan techniques, respectively. The nonlinear refractive index and the refractive index change of both protein films were determined in the green spectral range in a wide range of intensities and at various laser repetition rates. The nonlinear refractive index and refractive index change of PYP were compared to those of bR, with respect to photonics applications. Our results imply that the NLO properties of these proteins make them promising candidates for utilization in applied photonics, and they should be considered as valid alternatives for active components of IO circuits. © Copyright © 2020 Krekic, Zakar, Gombos, Valkai, Mero, Zimányi, Heiner and Dér

All-Optical Switching Demonstrated with Photoactive Yellow Protein Films

Integrated optics (IO) is a field of photonics which focuses on manufacturing circuits similar to those in integrated electronics, but that work on an optical basis to establish means of faster data transfer and processing. Currently, the biggest task in IO is finding or manufacturing materials with the proper nonlinear optical characteristics to implement as active components in IO circuits. Using biological materials in IO has recently been proposed, the first material to be investigated for this purpose being the protein bacteriorhodopsin; however, since then, other proteins have also been considered, such as the photoactive yellow protein (PYP). In our current work, we directly demonstrate the all-optical switching capabilities of PYP films combined with an IO Mach-Zehnder interferometer (MZI) for the first time. By exploiting photoreactions in the reaction cycle of PYP, we also show how a combination of exciting light beams can introduce an extra degree of freedom to control the operation of the device. Based on our results, we discuss how the special advantages of PYP can be utilized in future IO applications

Integrated optical biosensor for rapid detection of bacteria

In medical diagnostics, rapid detection of pathogenic bacteria from body fluids is one of the basic issues. Most state-of-the-art methods require optical labeling, increasing the complexity, duration and cost of the analysis. Therefore, there is a strong need for developing selective sensory devices based on label-free techniques, in order to increase the speed, and reduce the cost of detection. In a recent paper, we have shown that an integrated optical Mach-Zehnder interferometer, a highly sensitive all-optical device made of a cheap photopolymer, can be used as a powerful lab-on-a-chip tool for specific, labelfree detection of proteins. By proper modifications of this technique, our interferometric biosensor was combined with a microfluidic system allowing the rapid and specific detection of bacteria from solutions, having the surface of the sensor functionalized by bacterium-specific antibodies. The experiments proved that the biosensor was able to detect Escherichia coli bacteria at concentrations of 106 cfu/ml within a few minutes, that makes our device an appropriate tool for fast, label-free detection of bacteria from body fluids such as urine or sputum. On the other hand, possible applications of the device may not be restricted to medical microbiology, since bacterial identification is an important task in microbial forensics, criminal investigations, bio-terrorism threats and in environmental studies, as well

Optikai mikromanipuláció a biofizikában = Optical micromanipulation in biophysics

A projekt új lézercsipesz laboratórium kiépítését finanszírozta. Fő fejlesztés egy fény térmodulátorral (Spatial Light Modulator -SLM) felszerelt lézercsipesz megépítése. Ezzel tetszőlegesen sok csapda független egyidejű programozására van lehetőség. Új litográfiás berendezést is beszereztünk, ezzel mikrofluidikai eszközöket és integrált optikai elemeket készítünk. Az új laboratóriumban új típusú optikai mikromanipulációs kísérleteket végeztünk. Bonyolult alakú teszt objektumokkal összetett mozgásokat lehet megvalósítani. Négy típusú kutatást folytattunk: 1. A torziós manipulációs lehetőséget kihasználva DNS molekula csavarási tulajdonságait viszgáltuk. 2. A fotopolimerizációs struktúra építést és az új lézercsipeszt kihasználva új vizsgálati eszközöket készítettünk, mint mikroviszkozitásmérő, optikai mikromanipulátor. Modellrendszert alkottunk biológiai mozgások modellezésére: Kísérletileg kimutattuk és jellemeztük a hidrodinamikai szinkronizáció jeléenségét. 3. A folyadék mozgatásának fénnyel való vezérlését továbbfejlesztettük, a folyadék áramlási mintázatának fénnyel való változtatását oldottuk meg mikrofluidikai csatornában. 4. Integrált optikai elemeket készítettünk fotopolimerizációval mikrofluidikai alkalmazásra. Nagy érzékenységű interferometrikus szenzort készítettünk, ezt intermolekuláris reakciók jellemzésére, illetve optoelektronikai logikai áramkörök építésére alkalmaztuk. | The project supported the development of a new optical tweezers laboratory. The main development was the building of optical tweezers based on a Spatial Light Modulator (SLM). With this there is possibility to independently program an arbitrary number of optical traps. We also purchased a new photolythography device, this supportsthe building of microfluidics elements and integrated optical parts. In the new laboratory we performed novel optical manipulation experiments.We can realise complicated motions with test objects of complex shape. We worked on four types of experiments: 1. Using the possibility to rotate the trapped objects, we performed torsional manipulation experiments on DNA molecules. 2. Applying the photopolymerisation technique and the new optical tweezers we developed new experimental methods, like microviscosimeter, optical micromanipulator. We also created a model system to mimic biological motions. We experimentally demonstrated and characterised the phenomenon of hydrodynamic synchronisation. 3. We further developed the optical control of fluid flow: we realised the opticaal change of flow pattern in a microfluidics channel. 4. We built integrated optical elements for microfluidics applications. We built a high sensitivity interferometric sensor, and we used this to follow intermolecular interactions and to create optoelectronic logical circuit elements