A method for performing a combined protein and nucleic acid assay on a target captured by a capture agent, includes providing a microfluidic device having a microfluidic channel network having at least one microfluidic channel, the channel arranged to receive fluid, the device having at least two micro-particles disposed in fixed position in the channel, the micro-particles being functionalized with a capture agent for the assay, one of the micro-particles in the channel being functionalized with an antibody or antigen capture agent and another of the micro-particles being functionalized with a nucleic acid capture agent. In some embodiments, the network may have at least two microfluidic channels, each channel of the two channels arranged to receive portions of the same fluid and to be fluidicly isolatable from each other, the device having at least two micro-particles disposed in fixed position in the network channels, the micro-particles being functionalized with a capture agent, one of the micro-particles in one of the channels being functionalized with an antibody or antigen capture agent and another of the micro-particles in another of the channels being functionalized with a nucleic acid capture agent. The method may also include detecting both protein and nucleic acid present in an input sample using the respectively functionalized micro particles. In some embodiments, the micro particles may be micro-length tubes or glass nano reactors.