Graduation Semester and Year

2008

Language

English

Document Type

Thesis

Degree Name

Master of Science in Biomedical Engineering

Department

Bioengineering

First Advisor

Cheng-Jen Chuong

Abstract

The objective of this work is to develop multilayered nanoparticles for drug delivery and cell isolation applications. These particles principally consist of three layers; biodegradable polymer, thermo sensitive polymer and magnetic materials. For drug delivery, multilayered nanoparticles (MLNP) consisting of a magnetic core and two encompassing shells made up of temperature sensitive polymer, poly (N-isopropylacrylamide) (PNIPAAm), and biodegradable polymer, poly(D, L lactide-co-glycolide) (PLGA), were developed for targeted and controlled drug delivery. The PNIPAAm layer was immobilized onto magnetic nanoparticles (MNPs) via a silane coupling agent, Vinyltrimethoxysilane (VTMS), and free radical polymerization. These particles were then encapsulated with PLGA using a double emulsion solvent evaporation method with poly (vinyl alcohol) (PVA) as a surfactant. Transmission electron microscopy (TEM) confirmed that multilayered particles were obtained with PNIPAAm magnetic nanoparticles embedded within the PLGA shell. Factorial design analysis of the results showed that the particles size was inversely proportional to surfactant PVA concentrations and sonication powers while it was directly proportional to PLGA concentrations. PVA concentrations were the most important factor affecting the particle size, while PLGA was the least important factor. The drug release results demonstrated that these multilayer particles produced an initial burst release and a subsequent sustained release of both drugs loaded in the core and shell of MLNP. For cell isolation, Multi Layered Microparticles (MLMP) with a biodegradable polymeric core and two shells made up of MNPs and PNIPAAm-AH were synthesized. PLGA microspheres loaded with protein were prepared by using a double emulsion method. Magnetic nanoparticles functionalized with silane and silane amide were conjugated onto the surface of the PLGA microspheres by covalently bonding. PNIPAAm-AH copolymer was then immobilized onto the magnetic nanoparticles layer using a coupled silane agent and free radical polymerization of the NIPPAAm and Allylamine (AH) monomers. Scanning electron microscopy (SEM) showed that multilayered particles of size 50 to 100 µm were obtained. The polymeric composition of particles was also confirmed by FTIR spectrum. Differential scanning calorimetric (DSC) analysis determined that the polymer had a lower critical solution temperature (LCST) of 34.9ºC. Conjugation studies showed that the particles could further be conjugated with antibodies. The protein release results demonstrated that these multilayer particles produced an initial burst release and a subsequent sustained release of proteins. The shell release profile was affected by the changes of temperature where as the core release was affected by the core degradation, shell hydrophilicity, and protein diffusion through the shell. These results show that the particles can be used for impulsive release of differentiating factors followed by slow release of cell enrichment factors. Cell adhesion studies showed that the PNIPAAm-AH surface of the particles supports cell adhesion. Also, cell extraction studies showed that MLMPs can be used to extract cells from a suspension and the isolation process has no significant effect on cell viability.

Disciplines

Biomedical Engineering and Bioengineering | Engineering

Comments

Degree granted by The University of Texas at Arlington

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