Cross-linked bioreducible layer-by-layer films for increased cell adhesion and transgene expression

J Phys Chem B. 2010 Apr 29;114(16):5283-91. doi: 10.1021/jp100486h.


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, chi, was calculated. Good agreement in the two methods yields a cross-linking density of approximately 0.82 mmol/cm(3). 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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Cell Adhesion / drug effects
  • Cell Proliferation / drug effects
  • DNA / metabolism
  • Disulfides / chemistry
  • Gene Expression / drug effects*
  • Kinetics
  • Methacrylates / chemistry*
  • Methacrylates / pharmacology*
  • Methacrylates / toxicity
  • Mice
  • Myocytes, Smooth Muscle / cytology
  • Myocytes, Smooth Muscle / drug effects
  • Myocytes, Smooth Muscle / metabolism
  • NIH 3T3 Cells
  • Nylons / chemistry*
  • Nylons / pharmacology*
  • Nylons / toxicity
  • Pentanes / chemistry
  • Transfection
  • Transgenes / genetics*


  • Disulfides
  • Methacrylates
  • Nylons
  • Pentanes
  • poly(2-(dimethylamino)ethyl methacrylate)
  • DNA