Microtoxicology

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The term microtoxicology originally referred to the analysis of the negative effects of poisons in low doses. Recently, microtoxicology has also been understood to mean the investigation of toxic effects using extremely small amounts of substance in very small test volumes. Such examinations can be carried out particularly well in microfluidic systems or microdroplets, with typical test volumes being in the nanoliter to microliter range, i.e. H. only comprise a thousandth to a millionth of a milliliter. As a result, only very small amounts of toxic substances and other reagents need to be used, and the use of biological material is also very low. Naturally, these highly miniaturized tests cannot be carried out on large organisms or large populations . But they are very well suited for carrying out toxicological studies on cell cultures and microorganisms . In particular, they are also suitable for studying toxic effects on individual cells. Microtoxiology using microfluidic techniques is currently being tested in the laboratory, but has not been introduced as standard and has not yet been used routinely.

High-concentration-resolved dose / effect screenings

In addition to the determination of characteristic critical values ​​for toxic effects (e.g. LD50 value , EC50 value), it is also of interest how the growth or metabolic activity of cells or cell populations changes depending on the concentration . This requires many individual tests with a gradual variation in the concentration of the substance to be examined. For conventional toxicological investigations, this means a high consumption of chemicals, biological material and a lot of work. The larger series of examinations required for such examinations can be carried out in a very resource-saving and elegant manner using microfluid segment technology. This technique uses micropumps to generate an ordered series of droplets with graduated concentrations by varying the flow rates of several starting solutions very precisely. Typically, concentration gradations in the sub-percent range are implemented using sequences with several hundred drops, with the total consumption of solutions being less than one milliliter. In some cases, high-resolution dose / effect screenings show very sharp transitions between strong and suppressed growth and stimulation effects in the sublethal range.

Microtoxicological investigation of combination effects

The characterization of the combined effects of two or more noxae on organisms represents a particular challenge. The common occurrence and the common effect of poisons or other active substances is not the exception, but the rule. This applies not only to the effects on the environment , but also to consumer protection and the use of therapeutic agents in medicine. The poisonous effect of two substances can be independent of one another, additive effects can occur, but reinforcing ( synergistic ) effects or weakening effects ( antagonistic effects) are also possible. In order to be able to assess such effects, a quantitative analysis is particularly important. The number of individual experiments required for a quantitative investigation of combinatorial effects is the product of the number of concentration levels in each individual component. With a concentration level of around 3%, around 1000 individual tests are required for each of two combined substances. If you want to evaluate three substances in terms of their joint effect, around 30,000 tests would already be required with the same concentration resolution. Even with a concentration gradation of only 10%, around 1000 individual tests would still have to be carried out. The miniaturized strategy of microtoxicology offers very good prerequisites for solving this problem. Precise flow rate control can also be used to implement two- and three-dimensional concentration programs in drop sequences with 1000 or more individual drops. Each drop has an individual combination of the concentration of the individual components to be examined. In this way, complete two- and three-dimensional concentration spaces can be examined with minimal consumption of chemicals. In experimental laboratory studies, the method was tested on bacteria and eukaryotic microorganisms for the effects of environmental pollutants and drugs as well as components of food and beverages as well as nanoparticles . All variants of combination effects were observed depending on the noxious agents used.

Individual evidence

  1. ^ J. Cao, JM Koehler: Droplet-based microfluidics for microtoxicological studies, Eng. Life Sci. 15 (2015), 306-317
  2. ↑ JM Köhler, T. Henkel, A. Grodrian et al .: Digital reaction technology by micro segmented flow - components, concepts and applications, Chem. Eng. J. 101 (2004): 201-206
  3. ^ J. Cao, D. Kürsten, K. Krause, E. Kothe, K. Martin, M. Roth, JM Köhler: Application of micro-segmented flow fort wo-dimensional characterization of the combinatorial effect of zinc and copper ions on metal -tolerant Streptomyces strains, Appl. Microbiol. Biotechnol. 20 (2013), 8923-8930
  4. ↑ A. Funfak, J. Cao, A. Knauer, K. Martin, JM Köhler: Synergistic effects of metal nanoparticles and a phenolic uncoupler using microdroplet-based two-dimensional approach, J. Environ. Monit. 13 (2011), 410-415
  5. ↑ D. Kürsten, J. Cao, A. Funfak, Ph. Müller, JM Köhler: Cultivation of Chlorella vulgaris in microfluid segments and microtoxicological determination of their sensitivity against CuCl2 in the nanoliter range, Eng. Life Sci. 11 (2022), 580-587
  6. ↑ J. Cao, J. Goldhan, K. Martin, JM Köhler: Investigation of mixture toxicity of widely used drugs caffeine and ampicilline in the presence of an ACE inhibitor on bacterial growth using droplet-based microfluidic technique, Green Process Synth. 2 (2013), 591-601