Target disease: Sickle cell anemia
“Sickle Cell Disease” consists of several red blood cell disorders. Victims of the disease have red blood cells with defective hemoglobin (hemoglobin S). Since hemoglobin is largely responsible for circulation of oxygen through the body, a high percentage of sickle cells can lead to a number of symptoms, and ultimately shortens life expectancy by twenty years or longer.
Method: Detection of HBB gene
Since sickle cell is a genetic disease, the most straightforward way to test for it is to test for the presence of the mutant gene, hemoglobin subunit beta. The concentration of defective hemoglobin in one’s blood corresponds to the type of patient – carrier, diseased, or anemia-free.
Blood Processing Algorithm:
- Acquire necessary blood sample through finger prick
- Blood cells lysed by gravity-driven (possibly mechanically/heat driven) flow through a channel
- Remaining cell solution undergoes filtration to separate genome and unwanted cell wall/remains
- Genome flow is blocked, cannot progress (mechanically or possibly utilizing timed flow rates; a perfectly engineered set of channels could align the timing of mixture of flow from two channels)
- Concentration of HBB gene in cell solution amplified by a polymerase chain reaction
- Fluorescent probes injected into channel to cause complimentary base pairing with the gene present in solution
- Capillary electrophoresis used to isolate analyte solution
- Fluorescence of the final product measured and used to determine the status of the patient (free, carrier, diseased)
Required Tech:
- Sample collection: hypodermic needle
- Filtration: cell genome must be physically separated from cell wall, remains, etc.
- nanoporous material membrane
- ceramic filter
- PCR: increase concentration of analyte by polymerase chain reaction
- amplifies many copies of the same DNA across several orders of magnitude
- relies upon thermal cycling (repeated heating/cooling to induce enzymatic replication of DNA from melted DNA)
- requires restriction enzyme (Taq polymerase, BB/II)
- Hybridization probe: tag diseased DNA with fluorescent molecules
- probe is coated in the opposed base pair to encourage complimentary base pair bonding
- Capillary electrophoresis: bonded/tagged analyte can then be separated using a weak electric field
- measured fluorescence in separated analyte solution is indicative of the degree of anemia the patient suffers
- Measuring fluorescence: photodetector/fluorescence reader
