The present invention is drawn to the detection of harmful agents, known or previously unknown, using a biosensor. The biosensor makes use of non-living biological or biochemical sensor molecules for detecting and classifying chemicals, poisons, particles, vira, and bacteria in fluids. In a preferred embodiment, the bioreceptor comprises sensor molecules packaged in a collection device and treated to evoke an optical response to the presence of harmful agents, allowing for photocell detection and signal processing. The sensor molecules are selected from the group of biological molecules consisting of aptamers, single-chain nucleic acids, double-chain nucleic acids, hybridized chemicals incorporating these molecules and combinations thereof that bind with harmful agents. The harmful agents can also be collected in this manner for further analysis, and antibodies produced by the apparatus.