A ferrofluid-based homogeneous assay for highly sensitive and selective detection of single-nucleotide polymorphisms. 
A simple and low-cost colorimetric assay utilizing ferrofluidic nanoparticulate probes (FNPs) and a ligase for single-nucleotide polymorphism genotyping is described.  Excellent sensitivity and selectivity were accomplished through the engagement of the FNPs and a ligase chain reaction.