Carbodiimide Conjugation of Latent Transforming Growth Factor β1 to Superparamagnetic Iron Oxide Nanoparticles for Remote Activation

Conjugation of latent growth factors to superparamagnetic iron oxide nanoparticles (SPIONs) is potentially useful for magnetically triggered release of bioactive macromolecules. Thus, the goal of this work was to trigger the release of active Transforming Growth-Factor Beta (TGF-beta) via magnetic hyperthermia by binding SPIONs to the latent form of TGF-beta, since heat has been shown to induce release of TGF-beta from the latent complex. Commercially available SPIONS with high specific absorption rates (SAR) were hydrolyzed in 70% ethanol to create surface carboxylic acid conjugation sites for carbodiimide chemistry. Fourier-Transform Infra-Red (FTIR) analysis verified the conversion of maleic anhydride to maleic acid. 1-Ethyl-2-(3-dimethyulaminopropyl) carbodiimide (EDC) and N-hydroxysulfosuccinimide (Sulfo-NHS) were used to bind to the open conjugation sites of the SPION in order to graft latent TGF-beta onto the particles. The resulting conjugated particles were imaged with transmission electron microscopy (TEM), and the complexed particles were characterized by dynamic light scattering (DLS) and superconducting quantum interference device (SQUID) magnetometry. Enzyme-linked immunosorbent assay (ELISA) was used to assess the thermally triggered release of active TGF-beta from the latent complex, demonstrating that conjugation did not interfere with release. Results showed that latent TGF-beta was successfully conjugated to the iron oxide nanoparticles, and magnetically triggered release of active TGF-beta was achieved.