The present invention concerns molecularly imprinted polymers (MIPs) having an affinity for natriuretic peptides, such as atrial natriuretic peptide (ANP). In some embodiments, the MIP is a nanoparticle (a molecularly imprinted polymeric nanoparticle (MIPNP)). Other aspects of the invention include methods of preparing an MIP having affinity for a natriuretic peptide, methods for binding a natriuretic peptide in vitro or in vivo using an MIP of the invention, methods for interfering with the binding of a natriuretic peptide with its receptor in vivo, methods for reducing inflammation, cell growth, cell differentiation, or a cell proliferation disorder, methods for detecting natriuretic peptides, and devices and kits for sequestering and/or detecting natriuretic peptides.