http://hdl.handle.net/1721.1/3649 http://dspace.mit.edu:80/retrieve/3311 http://hdl.handle.net/1721.1/3649 http://hdl.handle.net/1721.1/35879 Understanding the Induced Self-Assembly System Between PEO-b-PAA and Iron Sondjaja, H. Ronny Tam, Michael K.C. Yap, Miranda G.S. Hatton, T. Alan The induced self-assembly phenomenon between PEO-b-PAA and Fe(II) was investigated. It was revealed that the electrostatic interaction between Fe(II) in the form of green rust (GR²⁺) particles and the COO- groups from the PAA backbone at pH 7 causes the formation of stable aggregates with Dh~156 nm. While it is stable at pH 7, the induced self-assembly structure, however, is disordered during the transformation of GR²⁺ into Fe₃O₄. The pH increment and the oxidation process itself were found to affect the stability. http://hdl.handle.net/1721.1/35878 Three-Dimensional Simulation of Carmustine Delivery to a Patient-Specific Brain Tumor Arifin, Davis Yohanes Wang, Chi-Hwa Smith, Kenneth A. This study presents the recent development of three-dimensional patient-specific simulation of carmustine delivery to brain tumor that highlights several crucial factors affecting the delivery. The simulation utilizes the full-brain three-dimensional geometry constructed from magnetic resonance images (MRI) of a brain tumor patient. Prior to the simulation with tumor, the baseline simulation is initially done to obtain the interstitial fluid homeostasis in the normal brain so that the real picture of brain fluid dynamics in human brain is obtained. The simulation is conducted by coupling equations of continuity, motion, and carmustine species conservation, which, in turn, are solved simultaneously to calculate pressure, flow, and drug concentration fields, respectively. Carmustine is delivered by using the commercially available Gliadel wafers following the surgical removal of the tumor. The possible effects of vasogenic edema (due to surgery trauma) to brain fluid dynamics is also included. Here, the compiled results highlight that the drug release profile is, if not more than, as important as the dosage and the possible increase of convection due to edema. This study also reveals that a new strategy, namely convection enhanced delivery (CED) is able to increase drug penetration by enhancing interstitial fluid convection; but, over-enhanced convection may cause toxicity complications to surrounding healthy tissue during later stages of treatment. http://hdl.handle.net/1721.1/35877 Synthesis and Self-Assembly Behavior of Poly(acrylic Acid)-b-Poly(l-Amino Acid) System Sinaga, Akasta Ravi, P. Hatton, T. Alan Tam, Michael K. C. The talk will present the synthesis and characterization of a new class of hybrid amphiphilic system between an electrolyte polyacrylic acid (PAA) synthetic segment, and a hydrophobic beta-sheet forming peptide segment, poly(L-valine) (PLVAL). The synthesis of monodispersed copolymers (Mw/Mn < 1.3) was achieved through a combination of atom transfer radical polymerization, click chemistry, and nickel-catalyzed ring opening of N-carboxy anhydrides. The click chemistry is demonstrated to be an excellent method for the intermediate -amino functionalization step to afford macroinitiators that are free from deactivating or interfering molecules with degree of functionality about 90%. Light scattering and circular dichroism characterization of PAAx-block-PLVALy (x-y of 80-100, 80-80, 80-60, and 40-100) show a correlation of the formation of spherical core-shell micelles to the ability of the peptide segment to form ordered beta-sheet structures. Generally, the beta sheet formation is stabilized by a low pH condition (low charge on PAA), higher Val/PAA ratio (less interference from PAA-Val hydrogen bondings), and degree of core shielding by PAA in the presence of disrupting agents, e.g. urea. At higher pH, the beta-sheet structure was also found to counteract the charge repulsions of PAA units, which allows the micelles to retain their overall size and shape. http://hdl.handle.net/1721.1/35875 On the Droplet Formation Process in Electrohydrodynamic Atomization Lim, Liang Kuang Xie, Jingwei Hua, Jinsong Wang, Chi-Hwa Smith, Kenneth A. A novel method of using a secondary electrical field source to control both the spray mode and the droplet size in the electrohydrodynamic atomization process is presented. Size of particles fabricated using the electrohydrodynamic atomization process can also be controlled using the same method. To further understand the electrohydrodynamic atomization process and the effect of a secondary electrical field source, a Front Tracking/Finite Difference method was employed for the Computational Fluid Dynamic Simulation of the Electrohydrodynamic Atomization process. To take into account of the electrical stresses, the Maxwell Stress tensor was included in the Navier-Stokes equation. Special care was taken to accurately include a secondary electrical field source. The formation of the Taylor Cone, jet and liquid droplets was successfully simulated. The simulated results were compared to the experimental results and the comparison was found to be reasonable when empirically determined charge density on the surface of the liquid was used as a simulation input.