Lipoplex-Functionalized Thin-Film Surface Coating Based on Extracellular Matrix Components as Local Gene Delivery System to Control Osteogenic Stem Cell Differentiation

A gene-activated surface coating is presented as a strategy to design smart biomaterials for bone tissue engineering. The thin-film coating is based on polyelectrolyte multilayers composed of collagen I and chondroitin sulfate, two main biopolymers of the bone extracellular matrix, which are fabricated by layer-by-layer assembly. For further functionalization, DNA/lipid-nanoparticles (lipoplexes) are incorporated into the multilayers. The polyelectrolyte multilayer fabrication and lipoplex deposition are analyzed by surface sensitive analytical methods that demonstrate successful thin-film formation, fibrillar structuring of collagen, and homogenous embedding of lipoplexes. Culture of mesenchymal stem cells on the lipoplex functionalized multilayer results in excellent attachment and growth of them, and also, their ability to take up cargo like fluorescence-labelled DNA from lipoplexes. The functionalization of the multilayer with lipoplexes encapsulating DNA encoding for transient expression of bone morphogenetic protein 2 induces osteogenic differentiation of mesenchymal stem cells, which is shown by mRNA quantification for osteogenic genes and histochemical staining. In summary, the novel gene-functionalized and extracellular matrix mimicking multilayer composed of collagen I, chondroitin sulfate, and lipoplexes, represents a smart surface functionalization that holds great promise for tissue engineering constructs and implant coatings to promote regeneration of bone and other tissues.

Extracellular matrix-inspired surface coatings functionalized with dexamethasone-loaded liposomes to induce osteo- and chondrogenic differentiation of multipotent stem cells

Biomimetic surface coatings can be combined with conventional implants to mimic the extracellular matrix (ECM) of the surrounding tissue to make them more biocompatible. Layer-by-layer technique (LbL) can be used for making surface coatings by alternating adsorption of polyanions and polycations from aqueous solutions without need of chemical reactions. Here, polyelectrolyte multilayer (PEM) systems is made of hyaluronic acid (HA) as polyanion and Collagen I (Col) as polycation to mimic the ECM of connective tissue. The PEM are combined with dexamethasone (Dex)-loaded liposomes to achieve a local delivery and protection of this drug for stimulation of osteo- and chondrogenic differentiation of multipotent stem cells. The liposomes possess a positive surface charge that is required for immobilization on the PEM. The surface properties of PEM system show a positive zeta potential after liposome adsorption and a decrease in wettability, both promoting cell adhesion and spreading of C3H10T1/2 multipotent embryonic mouse fibroblasts. Differentiation of C3H10T1/2 was more prominent on the PEM system with embedded Dex-loaded liposomes compared to the basal PEM system and the use of free Dex-loaded liposomes in the supernatant. This was evident by immunohistochemical staining and an upregulation of the expression of genes, which play a key role in osteogenesis (RunX2, ALP, Osteocalcin (OCN)) and chondrogenesis (Sox9, aggrecan (ACAN), collagen type II), determined by quantitative Real-time polymerase chain reaction (qRT-PCR) after 21 days. These findings indicate that the designed liposome-loaded PEM system have high potential for use as drug delivery systems for implant coatings that can induce bone and cartilage differentiation needed for example in osteochondral implants.