In addition to single-target detection, RCA is also desirable for multiple-analyte sensing assays because amplified products are considered to be localized at the array spot [62] . An array of real-time RCA in combination with the parallelism of arrays was developed by Yang et al. for protein quantitation down to the low nanomolar range [53] . Konry et al. constructed a two-layer sandwich assay on microbead surfaces for the combined detection of DNA and protein molecules in a single approach [63] . This array chip achieved detection limits of 1 pM and 10 fM for target DNA and proteins, respectively.