Abstract
Hydrogels are extensively studied for biomaterials application as they provide water swollen noninteracting matrices in which specific binding motifs and enzyme-sensitive degradation sites can be incorporated to tailor cell adhesion, proliferation, and migration. Hydrogels also serve as excellent basis for surface modification of biomaterials where interfacial characteristics are decisive for implant success or failure. However, the three-dimensional nature of hydrogels makes it hard to distinguish between the bioactive ligand density at the hydrogel-cell interface that is able to interact with cells and the ligands that are immobilized inside the hydrogel and not accessible for cells. Here, the authors compare x-ray photoelectron spectrometry (XPS), time-of-flight secondary ion mass spectroscopy (ToF-SIMS), enzyme linked immunosorbent assay (ELISA), and the correlation with quantitative cell adhesion using primary human dermal fibroblasts (HDF) to gain insight into ligand distribution. The authors show that although XPS provides the most useful quantitative analysis, it lacks the sensitivity to measure biologically meaningful concentrations of ligands. However, ToF-SIMS is able to access this range provided that there are clearly distinguishable secondary ions and a calibration method is found. Detection by ELISA appears to be sensitive to the ligand density on the surface that is necessary to mediate cell adhesion, but the upper limit of detection coincides closely with the minimal ligand spacing required to support cell proliferation. Radioactive measurements and ELISAs were performed on amine reactive well plates as true 2D surfaces to estimate the ligand density necessary to allow cell adhesion onto hydrogel films. Optimal ligand spacing for HDF adhesion and proliferation on ultrathin hydrogel films was determined as 6.5 ± 1.5 nm.
Highlights
Biomaterials can act as diagnostic materials in contact with body fluids, or as temporary or permanent substitute for organs, parts of organs or body structures, which are a)Author to whom correspondence should be addressed; electronic mail: juergen.groll@fmz.uni-wuerzburg.de destroyed or restricted in terms of function
We show that x-ray photoelectron spectrometry (XPS) is useful to characterize surface chemistry and identify the maximum number of ligands that can be loaded into these systems, it lacks the sensitivity to measure ligand concentrations at biologically relevant levels
ToF-SIMS is shown to have the requisite sensitivity, providing that clear and unambiguous secondary ions can be detected from the ligand and that a calibration method as indicated by the correlation shown in Fig. 4 and as shown on idealized reference surfaces23 is found to convert secondary ions into surface compositions
Summary
Biomaterials can act as diagnostic materials in contact with body fluids, or as temporary or permanent substitute for organs, parts of organs or body structures, which are a)Author to whom correspondence should be addressed; electronic mail: juergen.groll@fmz.uni-wuerzburg.de destroyed or restricted in terms of function. In the latter application, foreign body reactions are still a significant complication across materials classes that usually occur within the first 2–3 weeks of implantation.. Biosensors and modern biomaterials are designed to actively interact with their environment, either through their stiffness, structure/morphology and/or bioactivation For the latter, a variety of coating systems have been developed. Many hydrogel systems have been functionalized with ligands such as cell adhesion mediating peptides and proteins, the quantification of the ligand concentration at the hydrogel interface that is decisive for cell adhesion is often disregarded
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
