Patrick Schexnailder

Assessment of using laponite cross-linked poly(ethylene oxide) for controlled cell adhesion and mineralization.

The in vitro cytocompatibility of silicate (Laponite clay) cross-linked poly(ethylene oxide) (PEO) nanocomposite films using MC3T3-E1 mouse preosteoblast cells was investigated while cell adhesion, spreading, proliferation and mineralization were assessed as a function of film composition. By combining the advantageous characteristics of PEO polymer (hydrophilic, prevents protein and cell adhesion) with those of a synthetic and layered silicate (charged, degradable and potentially bioactive) some of the physical and chemical properties of the resulting polymer nanocomposites could be controlled. Hydration, dissolution and mechanical properties were examined and related to cell adhesion. Overall, this feasibility study demonstrates the ability of using model Laponite cross-linked PEO nanocomposites to create bioactive scaffolds.

Development of Biomedical Polymer-Silicate Nanocomposites: A Materials Science Perspective

Biomedical polymer-silicate nanocomposites have potential to become critically important to the development of biomedical applications, ranging from diagnostic and therapeutic devices, tissue regeneration and drug delivery matrixes to various bio-technologies that are inspired by biology but have only indirect biomedical relation. The fundamental understanding of polymer-nanoparticle interactions is absolutely necessary to control structure-property relationships of materials that need to work within the chemical, physical and biological constraints required by an application. This review summarizes the most recent published strategies to design and develop polymer-silicate nanocomposites (including clay based silicate nanoparticles and bioactive glass nanoparticles) for a variety of biomedical applications. Emerging trends in bio-technological and biomedical nanocomposites are highlighted and potential new fields of applications are examined.

Tuning cell adhesion by incorporation of charged silicate nanoparticles as cross-linkers to polyethylene oxide.

Controlling cell adhesion on a biomaterial surface is associated with the long-term efficacy of an implanted material. Here we connect the material properties of nanocomposite films made from PEO physically cross-linked with layered silicate nanoparticles (Laponite) to cellular adhesion. Fibroblast cells do not adhere to pure PEO, but they attach to silicate containing nanocomposites. Under aqueous conditions, the films swell and the degree of swelling depends on the nanocomposite composition and film structure. Higher PEO compositions do not support cell proliferation due to little exposed silicate surfaces. Higher silicate compositions do allow significant cell proliferation and spreading. These bio-nanocomposites have potential for the development of biomedical materials that can control cellular adhesion.

Addition of Chitosan to Silicate Cross-Linked PEO for Tuning Osteoblast Cell Adhesion and Mineralization

The addition of chitosan to silicate (Laponite) cross-linked poly(ethylene oxide) (PEO) is used for tuning nanocomposite material properties and tailoring cellular adhesion and bioactivity. By combining the characteristics of chitosan (which promotes cell adhesion and growth, antimicrobial) with properties of PEO (prevents protein and cell adhesion) and those of Laponite (bioactive), the resulting material properties can be used to tune cellular adhesion and control biomineralization. Here, we present the hydration, dissolution, degradation, and mechanical properties of multiphase bio-nanocomposites and relate these to the cell growth of MC3T3-E1 mouse preosteoblast cells. We find that the structural integrity of these bio-nanocomposites is improved by the addition of chitosan, but the release of entrapped proteins is suppressed. Overall, this study shows how chitosan can be used to tune properties in Laponite cross-linked PEO for creating bioactive scaffolds to be considered for bone repair.

Silicate Cross-Linked Bio-Nanocomposite Hydrogels from PEO and Chitosan

The compositions and the multi phase structures of bio-nanocomposite hydrogels made from silicate cross-linked PEO and chitosan are related to some of their physical and biological properties. The gels are injectable and self-healing because the cross-linking is physical and reversible under deformation. The presence of chitosan aggregates affects the viscoelastic properties and reinforces the hydrogel network. The chitosan adds advantageous properties to the hydrogel such as enhanced cell spreading and adhesion. In vitro biocompatibility data indicate that NIH 3T3 fibroblasts grow and proliferate on the bio-nanocomposite hydrogel as well as on hydrogel films.

Highly Extensible Bio-Nanocomposite Fibers

Here, we show that a poly(ethylene oxide) polymer can be physically cross-linked with silicate nanoparticles (Laponite) to yield highly extensible, bio-nanocomposite fibers that, upon pulling, stretch to extreme lengths and crystallize polymer chains. We find that both, nanometer structures and mechanical properties of the fibers respond to mechanical deformation by exhibiting strain-induced crystallization and high elongation. We explore the structural characteristics using X-ray scattering and the mechanical properties of the dried fibers made from hydrogels in order to determine feasibility for eventual biomedical use and to map out directions for further materials development.