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Development of a DNA Aptamer for detection of the Oocysts of Cryptosporidium parvum in drinking and recreational waters

Environmentally stable and disinfectant-resistant oocysts (eggs) of Cryptosporidium parvum (C. parvum) and other species shed in the feces of infected humans and animals frequently contaminate water resources with subsequent spread via potable and recreational waters. The current monoclonal antibody-based methods for detecting them in water are slow, labor-intensive, and skill demanding while requiring interpretation. CREM Co Labs has developed DNA-aptamer-based technique,  coupled with magnetic beads, to detect and identify the oocysts of C. parvum in water, for the monitoring of recreational and drinking waters. A sensitive and specific electrochemical aptasensor (3¢-biotinylated R4-6 aptamer) was used as a secondary ligand to bind the streptavidin-coated magnetic beads. This was incorporated into a probe using gold nanoparticle-modified screen-printed carbon electrodes (GNP-SPCE). Square wave voltammetry (SWV) allowed for specific recognition of C. parvum oocysts. The aptamer-coated probes had an oocyst detection limit of 50, with no binding to the cysts of Giardia duodenalis, another common waterborne pathogen, indicating high specificity. The system could successfully recover and detect C. parvum oocysts in spiked samples of raw lake and river water. Therefore, the combined use of the aptasensor and magnetic beads has potential to monitor water quality for C. parvum oocysts in field samples without relying on monoclonal antibodies and skill-demanding microscopy.