Colloidal Assembly of Biodegradable Multifunctional Nanoclusters

University Of Texas At Austin, Austin TX

Investigators

Abstract

0968038 Johnston Intellectual Merit: A major challenge in nanotechnology is to design stable particles smaller than 100 nm with multifunctionality, and in particular, strong optical and magnetic properties. It is difficult to achieve the required particle morphology in the common approach of atomic growth guided by surfactants. Thus, a robust and flexible alternative will be developed to assemble ~5 nm nanoparticle building blocks physically into multifunctional nanoclusters. This colloidal kinetic and interfacial assembly concept will be developed to obtain simultaneously sizes below 100 nm and extremely high loadings (>80%) of gold and iron oxide particles to produce strong optical (NIR absorbance) and magnetic (magnetic moment/volume and spin-spin relaxivity, r2) properties. In addition, these clusters will disassemble back into the original primary nanoparticles upon breakdown of biodegradable polymer stabilizers, which is very important for their translation to the biomedical field. Specifically, nanoclusters with high loadings of closely paced gold and iron oxide nanoparticles will be formed by tuning the colloidal interactions to control the cluster growth, size, and morphology. Weakly adsorbed polymer stabilizers will favor much higher inorganic particle loadings than in the case of equilibrium self-assembly, as well as cluster biodegradation. The spatial orientation of each type of nanoparticle in the cluster will be analyzed by high resolution TEM and TEM tomography at various tilt angles for a variety of nanoparticle compositions, surface coatings and stablilizing polymers. The NIR surface plasmon resonance and the spin-spin magnetic relaxivity will be measured and explained in terms of the cluster morphology. The cluster de-aggregation will be monitored in solution with spectroscopy and dynamic light scattering and in live cells with hyperspectral optical imaging and transmission electron microscopy. Broader Impact: This robust kinetic assembly platform for the design of biodegradable nanoclusters with high inorganic particle loadings for strong multifunctional properties will offer broad opportunities in microelectronics, sensors, imaging and optoelectronics. The simplicity and flexibility of this colloidal approach to form novel classes of nanoclusters will likely spawn numerous experimental and theoretical studies to understand the relationship between the optical/magnetic properties and nanocluster morphology. Furthermore, the optical/magnetic nanoparticles can provide solutions to one of the major challenges of modern medicine efficient delivery of therapeutics and molecular specific treatment of pathology with real-time imaging (photoacoustic imaging and MRI) for guidance and monitoring. The biodegradation of nanoclusters into primary nanoparticles can overcome the major roadblock in nanotechnology that is toxicity upon accumulation in humans and in the broader environment. A key theme will be to show young students that engineering can play a major role in improving health care, by integrating scientific concepts in chemistry and biology to address practical problems. The PIs will develop educational material, laboratory experiments and provide student teachers for the nationally renowned UTeach Outreach program, which provides undergraduate students to serve as volunteer instructors for science lessons in the Austin Independent School District. In the UTeach Young Scientists Summer Camps, rising sixth grade students from heavily Hispanic elementary Schools will come to University of Texas for one week to participate in hands-on inquiry-based science lessons that stress academic rigor. The PIs will add an engineering component to the science lessons and the summer camp to complement current efforts in chemistry and biology.