UC San Diego

The interfaces with micro/nanostructures in nature play important roles to bring in specific functions, which inspired and drove the development of novel nanostructures, including inorganic nanoparticles and organic nanoparticles. Among them, polymeric nanoparticles have been widely explored to programming interfaces because of the precise controlling in synthesis of polymers. Ring opening metathesis polymerization (ROMP) is a unique polymerization technique, which can incorporate versatile functional groups, tunable composition (hydrophobicity, molecular weight), and stimuli-responsiveness to endow various functionalities for the polymers, which have been explored for different application areas. In our research, we focused on designing and synthesizing multifunctional ROMP-based polymeric materials programming interfaces for different applications.

For Chapter 2, we describe amphiphilic tri-block copolymers containing FeIII-catecholate complexes formulated as spherical- or cylindrical-shaped micellar nanoparticles (SMN and CMN respectively) as new T1-weighted agents with high relaxivity, low cytotoxicity, and long-term stability in biological fluids. Relaxivities of both SMN and CMN exceed those of established gadolinium chelates across a wide range of magnetic field strengths. Interestingly, shape-dependent behavior was observed in terms of the particles’ interactions with HeLa cells, with CMN exhibiting enhanced uptake and contrast via magnetic resonance imaging (MRI) compared with SMN. These results suggest that control over soft nanoparticle shape will provide an avenue for optimization of particle based contrast agents as biodiagnostics. We propose those polycatechol nanoparticles as suitable for pre-clinical investigations into their viability as gadolinium-free, safe and effective imaging agents for MRI contrast enhancement.

For Chapter 3, we describe a method for the stabilization of low-boiling point (low-bp) perfluorocarbons (PFCs) at physiological temperatures by an amphiphilic triblock copolymer which can emulsify PFCs and be crosslinked. After UV-induced thiol-ene crosslinking, the core of the PFC emulsion remains in liquid form even at temperatures exceeding their boiling points. Critically, the formulation permits vaporization at rarefactional pressures relevant for clinical ultrasound.

For Chapter 4, liquid crystals confined within micrometer-scale domains have been explored as the basis of a wide range of field- and stimuli-responsive materials for use in technologies spanning from biological sensors to electro-optical devices. We aim to build up a versatile stimuli-responsive polymeric surfactant to modulate the orientation of liquid crystal microdroplets. By incorporated different types of cleavable linkers into this system, we are able to endow versatile stimuli-responsiveness (UV, Redox, pH, ROS) in order to adapt to different certain circumstances. We proved that those cleavable linker-contained homopolymers were able to emulsify with liquid crystal droplets and generate radial configuration. Then, by introducing specific stimuli, the linker will be cleaved and the homopolymer will be disassembled from the surface, then the configurations of liquid crystal droplets will change into bipolar. This work will provide fundamental information for designing a stimuli-responsive ROMP-based polymeric system, and it is promising to utilize this system as biosensor to detect some specific behaviors.

For Chapter 5, we prepared melanin-like nanoparticles (MelNPs) via spontaneous oxidation of dopamine, as biocompatible, synthetic analogues of naturally occurring melanosomes, and investigated their uptake, transport, distribution, and UV-protective capabilities in human keratinocytes. Critically, we demonstrate that MelNPs are endocytosed, undergo perinuclear aggregation, and form a supranuclear cap, or so-called microparasol in human epidermal keratinocytes (HEKa), mimicking the behavior of natural melananosomes in terms of cellular distribution and the fact that they serve to protect the cells from UV damage.