A supramolecular magnetic nanoparticle (SMNP) structure comprising an anti-cancer drug for use in a therapeutic method for treating cancer in a subject, the SMNP structure comprising: a plurality of structural components each including a plurality of binding elements; at least one magnetic nanoparticle each including a plurality of binding elements; a plurality of binding components each including a plurality of binding regions, wherein each of the binding regions is adapted to bind to a binding element; and a plurality of terminating components each including a terminating element, wherein the terminating element is adapted to occupy a binding region, wherein the plurality of terminating components are present in a sufficient quantity relative to the plurality of binding regions of the plurality of binding components to terminate further binding; said anti-cancer drug being a cargo encapsulated within the SMNP structure; said therapeutic method comprising the delivery of said cargo to a subject, and further comprising: imaging of the subject using positron electron tomography imaging; measuring time dependent accumulation of the cargo within the supramolecular magnetic nanoparticles (SMNP) in tumor versus a whole body of the subject using PET imaging; determining an optimal or critical point in time after administration of the SMNPs to the subject when the cargo within the SMNPs achieves maximum tumor accumulation; and triggering a release of the encapsulated cargo from disassembled SMNPs by using an alternating magnetic field. a plurality of structural components each including a plurality of binding elements; at least one magnetic nanoparticle each including a plurality of binding elements; a plurality of binding components each including a plurality of binding regions, wherein each of the binding regions is adapted to bind to a binding element; and a plurality of terminating components each including a terminating element, wherein the terminating element is adapted to occupy a binding region, wherein the plurality of terminating components are present in a sufficient quantity relative to the plurality of binding regions of the plurality of binding components to terminate further binding; said anti-cancer drug being a cargo encapsulated within the SMNP structure; said therapeutic method comprising the delivery of said cargo to a subject, and further comprising: imaging of the subject using positron electron tomography imaging; measuring time dependent accumulation of the cargo within the supramolecular magnetic nanoparticles (SMNP) in tumor versus a whole body of the subject using PET imaging; determining an optimal or critical point in time after administration of the SMNPs to the subject when the cargo within the SMNPs achieves maximum tumor accumulation; and triggering a release of the encapsulated cargo from disassembled SMNPs by using an alternating magnetic field. imaging of the subject using positron electron tomography imaging; measuring time dependent accumulation of the cargo within the supramolecular magnetic nanoparticles (SMNP) in tumor versus a whole body of the subject using PET imaging; determining an optimal or critical point in time after administration of the SMNPs to the subject when the cargo within the SMNPs achieves maximum tumor accumulation; and triggering a release of the encapsulated cargo from disassembled SMNPs by using an alternating magnetic field.