Cross-Linked Bioreducible Layer-by-Layer Films for Increased Cell Adhesion and Transgene Expression

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• 作者：Jenifer Blacklock ; Torsten K. Sievers ; Hitesh Handa ; Ye-Zi You ; David Oupick ; Guangzhao Mao ; Helmuth Mhwald
• 刊名：Journal of Physical Chemistry B
• 出版年：2010
• 出版时间：April 29, 2010
• 年：2010
• 卷：114
• 期：16
• 页码：5283-5291
• 全文大小：422K
• 年卷期：v.114,no.16(April 29, 2010)
• ISSN：1520-5207

文摘

The effect of cross-linking layer-by-layer (LbL) films consisting of bioreducible poly(2-dimethylaminoethyl methacrylate) (rPDMAEMA) and DNA is examined with regard to rigidity, biodegradability, cell adhesion, and transfection activity using 1,5-diiodopentane (DIP) cross-linker. DIP chemically reacts with the tertiary amines of rPDMAEMA, altering the chemical composition of these LbL films. The result is a change in surface morphology, film swelling behavior, and film rigidity, measured with AFM and ellipsometry. It is found that the apparent Young’s modulus is increased more than 4 times its original value upon cross-linking. Cross-linking mass is additionally confirmed with a quartz crystal microbalance with dissipation (QCM-D). Comprehensive analyses of these experimental values were investigated to calculate the degree of cross-linking using the rubber elasticity theory and the Flory−Rehner theory. Additionally, the Flory−Huggins parameter, χ, was calculated. Good agreement in the two methods yields a cross-linking density of 0.82 mmol/cm³. The Flory−Huggins parameter increased upon cross-linking from 1.07 to 1.2, indicating increased hydrophobicity of the network and formation of bulk water droplets within the films. In addition, the effects of cross-linking on film disassembly by 1,4-dithiothreitol (DTT) are found to be insignificant despite the alteration in film rigidity. Mouse fibroblast cells and smooth muscle cells are used to study the effect of cross-linking on cell adhesion and cell transfection activity. In vitro transfection activity up to seven days is quantified using secreted alkaline phosphatase (SEAP) DNA. Film cross-linking is found to enhance cell adhesion and prolong the duration of cellular transfection. These results contribute to the development of bioreducible polymer coatings for localized gene delivery.