Microfluidic devices and nanobiosensors comprising a magnetic nanoparticle attached to a reporter molecule via a release unit for microfluidic-based detection of a target analyte in a biological sample. The nanobiosensors can be magnetically manipulated or guided through the microfluidics channels for incubation with the biological sample, concentration of the nanobiosensors, and detection of target analytes, without having to pump the entire initial sample through a microfluidic channel of the microfluidic device. The magnetic nanoparticles are separated from the reporter molecules before detection and can be re-used.