Primary Cell Adhesion on RGD‐Functionalized and Covalently Crosslinked Thin Polyelectrolyte Multilayer Films

Abstract

Polyelectrolyte multilayers (PEMs) are now widely used for biomedical applications. In this work, we investigated the primary osteoblast adhesion properties of PEMs of poly(L‐lysine) (PLL), poly(L‐glutamic acid) (PGA), poly(alginic acid) (Palg), and poly(galacturonic acid) (Pgal). In order to compensate for the poor adhesion of the as‐synthesized films, two kinds of film modifications were achieved: a purely physical modification by film crosslinking, and a chemical modification by grafting a arginine–glycine–aspartic acid (RGD) peptide to PGA. Crosslinking was performed using a water‐soluble carbodiimide in combination with N‐hydroxysulfosuccinimide (sulfo‐NHS) to induce amide formation. This reaction was followed by Fourier‐transform IR spectroscopy. For film functionalization, a 15‐amino‐acid peptide was grafted to PGA and deposited as the top layer of the film. PLL/PGA, PLL/Palg, and PLL/Pgal films were crosslinked or functionalized. The films were tested for both short‐term adhesion properties and long‐term proliferation of primary osteoblasts. Whereas the effect of film crosslinking on short‐term adhesion was moderate, it was much more important for the RGD‐functionalized films. On the other hand, the long‐term proliferation was the same or even higher for the crosslinked films as compared with the functionalized films. This effect was particularly enhanced for the PLL/Palg and PLL/Pgal films. Finally, we functionalized PLL/PGA that had been crosslinked prior to PGA‐RGD deposition. These architectures exhibited even higher short‐term adhesion and proliferation. These results clearly show the important role of the physical properties of the films, besides their chemical properties, for the modulation of primary cell‐adhesion behavior.

Electrospun PLGA Fibers Incorporated with Functionalized Biomolecules for Cardiac Tissue Engineering

“…Peptide-conjugated polyelectrolytes have been previously used for surface modification to enhance cell affinity of biomaterials. 15,33,36,40 We suggest that ''isolation'' and reassociation'' of bioactive domains of a protein in polyelectrolytes such as PLL construct a biofunctional ''imitative-protein'' that can perform specific functions of a protein. Such ''imitative proteins'' have some advantages over native proteins.…”

Immunomodulation with Self-Crosslinked Polyelectrolyte Multilayer-Based Coatings

“…14,15 For example, the chemical crosslinking with a mixture of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide/N-hydroxysulfosuccinimide (EDC/NHS) is widely used for several polyelectrolyte multilayers (PEMs), typically, PLL/HA, PLL/polyglutamic acid (PLL/PGA), and chitosan/HA. [16][17][18] The EDC/NHS crosslinking involves a reaction between carboxylic groups of HA and amine groups of PLL. However, to achieve the crosslinking reaction a long incubation time is required (at least 12 hours) and also some extensive rising steps after it, in order to eliminate excess products that can be toxic.…”

Biochemical Functionalization of Polymeric Cell Substrata Can Alter Mechanical Compliance

“…2 For weak PEMs comprising PAA and poly-(allylamine hydrochloride) or PAH, nominal elastic modulus E varies by orders of magnitude for mod-2 changes in assembly pH, due to the pH-dependent degree of ionic cross-linking that correlates inversely with the capacity to swell in aqueous solutions. Further, Thompson et 28 In light of these previous findings on biochemical and mechanical modulation of cell-substrate adhesion, here we sought to confirm that the mechanical properties of PEMs were unaffected by a particular biochemical surface functionalization process. To that end, we employed scanning probe microscope-enabled nanoindentation to measure the nominal elastic modulus E of PEMs functionalized through various processing routes with a synthetic peptide containing the integrin binding sequence RGD.…”