Trypanosoma brucei is a parasitic protozoan causative of African trypanosomiasis, or African Sleeping Sickness, in humans. Transmission of the parasite occurs through the bite of the testse fly or can be passed congenitally. The purpose of this research is to address the prevalence of undiagnosed infants through the use of a device that utilizes the characteristics of T. brucei to detect its presence in the vulnerable population. Detection of this parasite is costly and requires extensive technical training (1) so it is important to further characterize this organism in hopes of developing more affordable and intuitive diagnostic tools. Previous work suggests a possible affinity of T. brucei to hydrophobic surfaces, such as paraffin wax (2). This project attempts to further analyze this attraction as well as to determine the effects of varying topographies on the movement of the parasite.

Initial experiments consisted of exposing T. brucei to randomized lines of paraffin wax randomly deposited on the surface of a petri dish. Parasites were observed on the edges of the paraffin wax. In order to determine if this was attraction to the paraffin wax or simply the topography of the wax on a flat surface, a polycarbonate chip with steps of various heights was fabricated on a minimill to analyze the effect of topography on the parasite. This chip was placed in a petri dish and covered in media containing parasites at 106 parasites/ml concentration. The movement of the parasites around the edges of the steps was then monitored. In order to analyze the effect of hydrophobic surfaces and topography, another chip made of paraffin wax, using the polycarbonate piece above as mold, was created in order to run an experiment similar to the ones discussed above.

Initial results point to possible affinity to hydrophobic surfaces and topography. The testing of paraffin smeared onto a petri dish lead to the observation of dead T. brucei accumulated around the edges of the paraffin wax. This accumulation indicates that further experimentation must be done to conclude whether this is a result of the hydrophobic nature of the paraffin wax or the topography of the hydrophobic substance on a flat substrate. Testing topography on the polycarbonate chip demonstrated occasional parasites accumulating around the cleft created by the topographical steps, and most swimming undeterred by the height difference. The testing of the topographical chip created from paraffin will be revisited as the chip was ultimately too thick for clear visibility of the parasites under a microscope.

Ongoing work is on examining different ranges of elevation T. brucei could be attracted to. A new topography chip is being fabricated with shorter topographical surfaces in order to appropriately examine the effects of topography on a scale that is better fit to that of the parasite. Besides testing topography, the affinity for paraffin and polycarbonate will be further examined. The expected impact of this research is to enable the inexpensive and rapid aggregation of the parasite to enable its identification with low caliber microscopes in the field.

References

1. Holm, S. H., Beech, J. P., Barrett, M. P., & Tegenfeldt, J. O. (2011). Separation of parasites from human blood using deterministic lateral displacement. Lab on a Chip, 11(7), 1326-1332.

2. Souto-Padrón, T. (2002). The surface charge of trypanosomatids. Anais da Academia Brasileira de Ciências, 74(4), 649-675.