Adsorption behavior of Plasmid DNA on Binary Self-Assembled Monolayers Modified Gold Substrate
Date Issued
2011
Date
2011
Author(s)
Kao, Wei-Lun
Abstract
Biodegradable polymers have been widely applied in the drug delivery, which has drug-targeting specificity and can control the release rate. Most of these drug molecules are covalently bonded with the polymers and cannot release easily. On the other hand, gold is known to have good biocompatibility and the surface properties can be modified with the use of self-assembled monolayer (SAM) hence it is a promising carrier for drug delivery. In previous work, surface properties of gold surface were tailored with homogeneously-mixed amine and carboxylic acid functional groups and Au nanoparticles with a series of iso-electronic points (IEP) were prepared. In other words, the sign of surface potential flips at a tunable pH. Considering electrostatic interactions, these engineered nanoparticle could switch between adsorbing or desorbing molecules in specific pH range and serve as a pH sensitive drug delivery system. In order to understand how macromolecules interact with these gold substrates modified with different ratio of HS(CH2)8NH2 and HS(CH2)15COOH, Quartz crystal microbalance with dissipation detection (QCM-D) is used. Simultaneously collected frequency and dissipation shift is examined using visco-elastic model to examine the adsorption behavior of plasmid DNA on the binary functional groups modified gold surfaces. The experimental results revealed that the plasmid DNA can adsorbed on the SAM surfaces electrostatically, and the amount of adsorbed plasmid DNA decreased with environmental pH and increased with the ratio of amine functional group on the surfaces. Nevertheless, unlike the case of depositing inorganic materials, it is found that the adsorption behavior of plasma DNA cannot be simply discussed via IEP of the surfaces because dipole-induced dipole interaction between uncharged functional groups on SAM and negatively charged DNA backbone. It is also found that the apparent absorption rate (in terms of thickness) is lower when electrostatic attraction dominated because the deposited DNA film is more dense and rigid.
Subjects
drug delivery
SAM
plasmid DNA
IEP
electrostatic interaction
dipole-induced dipole
Type
thesis
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