Date of Completion

5-7-2016

Embargo Period

5-6-2016

Advisors

Dr. Sangamesh Kumbar and Dr. Wendy Vanden Berg-Foels

Field of Study

Biomedical Engineering

Degree

Master of Science

Open Access

Open Access

Abstract

Poly(lactide-co- glycolide) (PLGA) is a versatile biomaterial and is desirable for use in tissue engineering applications requiring a degradable matrix or fixation. PLGA degradation rate can be controlled through manipulation of the ratio of its constituent monomers PLA (polylactic acid) and PGA (polyglycolic acid). When PLGA degrades it can lead to the development of acidic conditions eliciting an inflammatory response. We have investigated the addition of biodegradable Magnesium (Mg) particles to a PLGA matrix, aiming to achieve neutral byproducts. Within the body Mg degrades into a basic oxide and hydrogen gas, so through varying its concentration in a PLGA scaffold it may be possible to determine an optimal concentration for pH neutrality. It was also hypothesized that the maintenance of a neutral pH during degradation would prolong degradation rate of the composite. It was found that as Mg concentration increased, the length of degradation increased from ~35 days (0%wt Mg) to ~75 days (10%wt Mg). There was also a proportional shift in pH toward the basic end of the spectrum. In order to assess neutralization a simulated in vivo degradation study was performed. It was found that the addition of Mg (5%wt Mg) prolonged degradation from ~40 days to ~80 days and kept pH in a fairly neutral range (6-8.5 versus 4-7.5 without Mg). Increasing concentration of Mg was also found to increase the modulus of elasticity of composites. During the development of the PLGA-Mg composites agglomeration of the Mg particles was observed. Agglomeration presents potential issues for the composites including variable mechanics and formation of hydrogen gas pockets in the body. In order to overcome this Mg particles were modified with a hydrophobic self-assembling monolayer. The intention of the layer was to improve particle integration and add a protective coating against degradation. Assessment by micrographs revealed some degree of improvement in 10%wt Mg composites where hydrogen gas formation was reduced. In a degradation study modification wasn’t found to have any consistent observable difference on degradation behavior. Further testing must performed to assess whether modification was successful.

Major Advisor

Dr. Syam Nukavarpu

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