Jonathan Gilbert

Research Summary

John graduated in 2015

My thesis work is focused on the fundamental structure of stratified polymer thin films and the design of non-spherical and anisotropic materials for biomedical applications.

Functional thin films often require stratified structures with a distinct purpose for each layer and nanometer level control over the structure. However, due to diffusion the composition and function of these layers may not be as desired. Using high-resolution depth profiling XPS with polymer-friendly cluster-ion C60 sputtering we can detect and control this diffusion. This technique allows for the direct determination of the composition and chemical bonding properties of polymeric films with ~10nm level resolution.

Progress in drug delivery has been enabled by designing the surface chemistry and the shape of particles for targeted delivery. Furthermore, recent studies have started using cell-mediated drug delivery which uses the cell's natural function, such as homing to disease sites, to deliver the therapeutic materials. We have developed a polymeric particle termed a backpack that conjugates strongly to the surface of immune cells for cell-mediated delivery. Backpacks are anisotropic, stratified polymeric thin films that are hundreds of nanometers thick and microns wide. In partnership with the Mitragotri group at UCSB we show that the backpack is phagocytosis resistant and when attached to a cell it can continue to perform native functions. The capability to resist internalization while strongly attached to the surface of immune cells, uniquely positions the backpack for cell-mediated therapeutic delivery in areas such as arthrosclerosis and cancer.

Another type of particle we have designed is the cell-tube. Inspired by the use of chemically non-uniform Janus particles to control the local orientation of synthetic particles in colloid systems, we designed a tube-shaped, chemically non-uniform microparticle with cell-adhesive ligands on the ends of the tubes and a cell-resistant surface on the sides. Our results show that by altering the presentation of polymer on the end versus the side we can control the orientation of tubes on cells opening the capability to design cellular materials from the bottom up.