Microfluidic separation techniques for the removal of micro-organisms from semen for the veterinary industry
Due to the COVID-19 crisis the PhD defence of Tanja Hamacher will take place (partly) online.
The PhD defence can be followed by a live stream.
Tanja Hamacher is a PhD student in the research group Biomedical and Environmental Sensorsystems (BIOS). Her supervisor is prof.dr.ir. L.I. Segerink from the Faculty of Electrical Engineering, Mathematics and Computer Science (EEMCS).
Artificial insemination (AI) is the most widely used breeding technique in the porcine and bovine industry. The presence of micro-organisms in semen used for AI, is a potential risk for disease transmittance and decreases semen quality. To minimize the hazards caused by micro-organisms, many precautionary measures are in place. For example, antibiotics are mandatorily added to semen extenders to kill bacteria and semen is regularly screened for the presence of viruses. Although these practices are known to be beneficial, they hold limitations. The overuse of antibiotics leads to the emergence of antibiotic-resistant bacteria strains. Since antibiotics are the only treatment for bacterial infections, infections caused by antibiotic-resistant bacteria strains are a global threat. The transmission of viruses between animals can also spread to humans causing global pandemics. Two well-known examples are the swine flu and Covid-19 pandemics. To prevent the spread of viruses, semen is regularly screened but this is labor-intensive, expensive and time-consuming. Additionally, test results are usually not available prior insemination with fresh semen. The implementation of a step that removes micro-organisms during routine semen processing, increases the biosecurity of AI, eliminates the use of antibiotics, makes contaminated semen usable and can be economically beneficial.
The aim of this project is to remove micro-organisms from semen with microfluidic separation techniques by considering not only the micro-organism removal rates, but also sperm recovery, semen quality and processing time. Hence, this thesis explores the potential of two microfluidic separation techniques for the removal of micro-organisms from semen for the veterinary industry.
The two applied separation techniques are pinched flow fractionation and acoustophoresis. The first microfluidic separation technique explored is pinched flow fractionation, in which hydrodynamic forces are used to separate different particles by size. After optimizing the chip design and flow parameters, virus removal rates of at least 84 ± 4% and sperm recovery of 86 ± 6% were achieved. The second explored microfluidic separation technique is acoustophoresis, in which particles are manipulated by an acoustic force. The removal of micro-organisms from semen was explored with the benchtop instrument AcouWash (AcouSort, Lund, Sweden). With optimized flow parameters, bacteria removal rates of at least 88 ± 7% and sperm recovery rates of 90 ± 4% were achieved. Also, virus removal from semen was successful with acoustophoresis. The current processing times of both techniques of one (porcine) ejaculate are too long and, therefore, the separation process is not implementable in routine semen processing. Several ideas to increase the sample throughput were suggested with respect to their impacts on separation quality and processing time.
In conclusion, the microfluidic separation techniques PFF and acoustophoresis removed (a high percentage of) micro-organisms from semen. In contrast to PFF, acoustophoresis holds more promise for removing both types of micro-organisms in one separation step and in reaching the desired processing time. The advantage of implementing a physical micro-organism removal step in routine semen processing can eliminate the use of antibiotics and will increase the biosecurity of AI in the veterinary industry.
