Catechols in the form of DOPA are found in high concentrations in mussel adhesive proteins (MAPs) and contribute to the unique ability of MAPs to strongly bind to almost any material surface. We have stabilized sub-10-nm superparamagnetic iron oxide nanoparticles (SPIONs) through catechol-derivative anchor groups, such as nitroDOPA, bound to 5 kDa poly(ethylene glycol) and shown that the dispersed particles possess essentially irreversible binding affinity to iron oxide and thus can optimally disperse superparamagnetic nanoparticles under physiologic conditions1. This not only leads to ultrastable iron oxide nanoparticles but also allows close control over the hydrodynamic diameter and interfacial chemistry. The latter is a crucial aspect for the assembly of functionalized magnetic nanoparticles, e.g., as targeted magnetic resonance contrast agents. Preliminary applications in vitro and in vivo of functionalized SPIONs for Magnetic Resonance Imaging (MRI).
Furthermore, we have functionalized <5 nm diameter SPIONs with alkane-catechol self-assembly systems to render them hydrophobic and subsequently incorporated them into lipidic vesicles2. Choosing a lipid system with a transition temperature above 40°C allowed for the design of a delivery system where hydrophilic model chemicals could be stably incorporated in the lumen of the liposomes at room temperature. Upon application of an ac magnetic field using an in vitro system, local heating of the membrane caused an increase of temperature to above the transition temperature and subsequent efficient release without destroying the liposomal structure and integrity. This cargo system has the potential of targeting drug-loaded nanocontainers to specific tissue/location (e.g., tumor) followed by highly controlled, externally triggered drug release.
References
1) E. Amstad et al., Nano Letters 9(12): 4042–4048 (2009)
2) E. Amstad et al., Nanoletters 11(4), 1664-1670 (2011)