Fibronectin terminated multilayer films: Protein adsorption and cell attachment studies

Abstract

Electrostatically driven layer-by-layer (LbL) assembly is a simple and robust method for producing structurally tailored thin film biomaterials, of thickness ca. 10nm, containing biofunctional ligands. We investigate the LbL formation of multilayer films composed of polymers of biological origin (poly(L-lysine) (PLL) and dextran sulfate (DS)), the adsorption of fibronectin (Fn)--a matrix protein known to promote cell adhesion--onto these films, and the subsequent spreading behavior of human umbilical vein endothelial cells (HUVEC). We employ optical waveguide lightmode spectroscopy (OWLS) and quartz crystal microgravimetry with dissipation (QCMD) to characterize multilayer assembly in situ, and find adsorbed Fn mass on PLL-terminated films to exceed that on DS terminated films by 40%, correlating with the positive charge and lower degree of hydration of PLL terminated films. The extent and initial rate of Fn adsorption to both PLL and DS-terminated films exceed those onto the bare substrate, indicating the important role of electrostatic complexation between negatively charged protein and positively charged PLL at or near the film surface. We use phase-contrast optical microscopy to investigate the time-dependent morphological changes of HUVEC as a function of layer number, charge of terminal layer, and the presence of Fn. We observe HUVEC to attach, spread, and lose circularity on all surfaces. Positively charged PLL-terminated films exhibit a greater extent of cell spreading than do (negatively charged) DS-terminated films, and spreading is enhanced while circularity loss is suppressed by the presence of adsorbed Fn. The number of layers plays a significant role only for DS-terminated films with Fn, where spreading on a bilayer greatly exceeds that on a multilayer, and PLL-terminated films without Fn, where initial spreading is significantly higher on a monolayer. We observe initial cell spreading to be followed by retraction (i.e. decreased cell area and circularity with time) for films without Fn, and for DS-terminated films with Fn. Overall, the Fn-coated PLL monolayer and the Fn-coated PLL-terminated multilayer are the best performing films in promoting cell spreading. We conclude the presence of Fn to be an important factor (more so than film charge or layer number) in controlling the interaction between multilayer films and living cells, and thus to represent a promising strategy toward in vivo applications such as tissue engineering.

Vascularization of Engineered Tissues: Approaches to Promote Angiogenesis in Biomaterials

“…ECs have been cultured successfully on ECM coated polymers such as hyaluronic acid [19], poly(dimethyl siloxane) (PDMS) [20], poly(L-lysine) [21], poly(Llactide), and poly(caprolactone) [22]. ECM coating on biomaterials can facilitate neovascularization in vivo.…”

Polyelectrolyte Multilayers in Tissue Engineering

“…61 This feature can be altered by varying the final PE deposited during the LbL assembly. 34 80 In situ mass adsorption measurements with a quartz crystal microbalance with dissipation showed a 40% increase in fibronectin adsorption on PLL-terminated PEMs compared to dextran sulfateterminated multilayers. Further, significant spreading of human umbilical vein endothelial cells was observed only on the PLL-terminated PEM, due to the increased fibronectin adsorption and terminal PLL layer.…”

Interaction of PC-3 cells with fibronectin adsorbed on sulfonated polystyrene surfaces

“…As a result of adsorption, FN conformation can become compact or extended, depending on physicochemical conditions. It has been observed that adhesion of normal and cancer cells to substrate surfaces containing chemical groups with a negative charge (-SO 3 H, -OH, -COOH) or a positive charge (-NH 2 ) depends on surface wettability and the conformation of the protein molecule on the surface [9,[11][12][13][14][15][16][17][18][19]. Fibronectin adsorbed on strongly hydrophilic polystyrene surfaces, in contrast to the adsorption on hydrophobic surfaces, is characterized by extended, biologically active conformation with the unfolded cellbinding domain (CCBD), which stimulates not only the early phase of adhesion, but also the cell spreading process [13,14,20,21].…”