(227c) Surface Micropatterning of Poly(Ethylene Glycol) Hydrogels

Techniques which control the spatial presentation of surface moieties are important for the advancement of tissue engineering, the elucidation of fundamental structure-function relationships of tissues, and the formation of immobilized cell arrays for biotechnology [1]. In the present study, photoactive poly(ethylene glycol) (PEG) hydrogels are examined for the spatially controlled presentation of peptides. PEG polymers are hydrophilic, biocompatible, and are intrinsically resistant to protein adsorption and cell adhesion. PEG-diacrylate (PEG-DA) hydrogels thus provide a ?blank slate?, upon which desired biofunctionality can be built using monoacrylated PEG conjugated to the peptide or biological moiety of interest [2]. The following work exploits the photoactivity and material properties of PEG-acrylates and the laser scanning functionality of certain confocal microscopes to create surface patterned hydrogels. Specifically, regions of interest (ROIs) corresponding to desired areas of the PEG-DA hydrogel surface to be patterned with monoacrylated PEG-peptide were specified. A thin layer of monoacrylated PEG-peptide was spread onto the surface of a PEG-DA hydrogel prepared using eosin Y as a photoinitiator. Patterning was carried out using an irradiation cycle in which a confocal microscope was programmed to apply a 514 nm Argon ion laser line only to the specified ROIs. Unbound monoacrylated PEG-peptide was rinsed away with sterile PBS. The utility of the patterns for controlling cell adhesion and behavior was verified by maintaining monoacrylated-PEG-RGDS patterned gels in the presence of human dermal fibroblasts for 3 days. A range of feature sizes can be patterned onto hydrogel surfaces using this laser scanning lithographic (LSL) technique, including features down to 5µm in size. In addition, a variety of shapes, including free-form objects, can be patterned using LSL. Since the concentration of bound monoacrylated PEG-peptide can be controlled by varying the irradiation exposure time, 1D and 2D spatial gradients in bound peptide concentration can be formed. This capability is unique and should allow for the study of the interplay of geometrical and ligand concentration effects on cell behavior. Controlled functionalization of PEG-DA hydrogels should allow for increased insight into the cell behavior and cell-biomaterial interactions.

References

[1] Chen CS, et al. Biotechnol Prog. 1998; 14(3):356-63. [2] Gombotz WR, et al. J. Biomed. Mater. Res. 1991; 25: 1547-62.

Acknowledgements

Project funding provided by the NIH and NSF.