Medical imaging technologies allow for the rapid diagnosis and evaluation of a wide range of pathologies. In order to increase their sensitivity and utility, many imaging technologies such as CT and MRI rely on intravenously administered contrast agents. While the current generation of contrast agents has enabled rapid diagnosis, they still suffer from many undesirable drawbacks including a lack of tissue specificity and systemic toxicity issues. Through advances made in nanotechnology and materials science, researchers are now creating a new generation of contrast agents that overcome many of these challenges, and are capable of providing more sensitive and specific information. In this review, we summarize the main classes of nanotechnology-based contrast agents for each of the major imaging technologies, and highlight progress in their development as well as the challenges to be addressed. We also review the relevant biological interactions that determine the in vivo fate of these contrast agents, and describe major themes in medical nanotechnology including stealth and targeting.

Superparamagnetic iron oxide nanoparticles (SPIONs) comprise a fundamental technology class within the emerging field of nanomedicine, and have been extensively researched for cancer imaging and therapy. This review article will discuss the chemistry and design considerations associated with the synthesis of SPIONs and their incorporation into pharmaceutical formulations. Specific synthesis methods discussed include coprecipitation, thermal decomposition, microemulsion and solvothermal synthesis, as well as surface treatments and encapsulations to improve the nanoparticle biocompatibility and efficacy. Emerging applications of novel particle designs as MRI contrast agents are also discussed.

We investigated the contact behaviors of a nanoscopic stiff thin film bonded to a compliant substrate and derived an analytical solution for determining the elastic modulus of thin films. Microscopic contact deformations of the gold and polydopamine thin films (<200 nm) coated on polydimethylsiloxane elastomers were measured by indenting a soft tip and analyzed in the framework of the classical plate theory and Johnson-Kendall-Roberts (JKR) contact mechanics. The analysis of this thin film contact mechanics focused on the bending and stretching resistance of thin films and is fundamentally different from conventional indentation measurements where the focus is on the fracture and compression of the films. The analytical solution of the elastic modulus of nanoscopic thin films was validated experimentally using 50 and 100 nm gold thin films coated on polydimethylsiloxane elastomers. The technical application of this analysis was further demonstrated by measuring the elastic modulus of thin films of polydopamine, a recently discovered biomimetic universal coating material. Furthermore, the method presented here is able to quantify the contact behaviors of nanoscopic thin films, effectively providing fundamental design parameters, the elastic modulus, and the work of adhesion, crucial for transferring them effectively into practical applications.

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