Initial cell adhesion of three cell types in the presence and absence of serum proteins.

With the development of a wide range of new biomaterials for the sensing of different cell behaviour, it is important to consider whether the cells tested in vitro are in direct contact with the material or whether cell-biomaterial contact is mediated by an interfacial layer of proteins originating from the culture medium or from the cells themselves. Thus, this study describes the differences between the cell adhesion mediated by proteins originating from foetal bovine serum and without the presence of such proteins 2 h following cell seeding exemplarily with different cell types (an osteoblastic cell line, primary fibroblasts, and mesenchymal stem cells). Three of the examined cell types were found to react differently to differing conditions in terms of cell shape, area, and number. Nevertheless, the expression and localization of the various proteins involved in cell adhesion and signalling (CD44, vinculin, talin, actin, focal adhesion kinase, Rho-GTPases and extracellular signal-regulated kinases 1 and 2) were, in general, similar with respect to all the cell types tested, albeit varying according to the presence or absence of serum. Moreover, no classical focal adhesions were formed during cell adhesion without serum proteins, while different signalling pathways were involved in this process. The study systematically describes and discusses the cell adhesion of three different human cell types to a well-known substrate without the presence of external proteins and it is hoped that this knowledge will be subsequently applied in biomaterial applications in which the presence of external proteins is undesirable (e.g. for biosensing purposes).

Nanocarbon Allotropes-Graphene and Nanocrystalline Diamond-Promote Cell Proliferation.

Two profoundly different carbon allotropes - nanocrystalline diamond and graphene - are of considerable interest from the viewpoint of a wide range of biomedical applications including implant coating, drug and gene delivery, cancer therapy, and biosensing. Osteoblast adhesion and proliferation on nanocrystalline diamond and graphene are compared under various conditions such as differences in wettability, topography, and the presence or absence of protein interlayers between cells and the substrate. The materials are characterized in detail by means of scanning electron microscopy, atomic force microscopy, photoelectron spectroscopy, Raman spectroscopy, and contact angle measurements. In vitro experiments have revealed a significantly higher degree of cell proliferation on graphene than on nanocrystalline diamond and a tissue culture polystyrene control material. Proliferation is promoted, in particular, by hydrophobic graphene with a large number of nanoscale wrinkles independent of the presence of a protein interlayer, i.e., substrate fouling is not a problematic issue in this respect. Nanowrinkled hydrophobic graphene, thus, exhibits superior characteristics for those biomedical applications where high cell proliferation is required under differing conditions.

The effects of different cross-linking conditions on collagen-based nanocomposite scaffolds-an in vitro evaluation using mesenchymal stem cells.

Nanocomposite scaffolds which aimed to imitate a bone extracellular matrix were prepared for bone surgery applications. The scaffolds consisted of polylactide electrospun nano/sub-micron fibres, a natural collagen matrix supplemented with sodium hyaluronate and natural calcium phosphate nano-particles (bioapatite). The mechanical properties of the scaffolds were improved by means of three different cross-linking agents: N-(3-dimethylamino propyl)-N'-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide in an ethanol solution (EDC/NHS/EtOH), EDC/NHS in a phosphate buffer saline solution (EDC/NHS/PBS) and genipin. The effect of the various cross-linking conditions on the pore size, structure and mechanical properties of the scaffolds were subsequently studied. In addition, the mass loss, the swelling ratio and the pH of the scaffolds were determined following their immersion in a cell culture medium. Furthermore, the metabolic activity of human mesenchymal stem cells (hMSCs) cultivated in scaffold infusions for 2 and 7 days was assessed. Finally, studies were conducted of cell adhesion, proliferation and penetration into the scaffolds. With regard to the structural stability of the tested scaffolds, it was determined that EDC/NHS/PBS and genipin formed the most effectively cross-linked materials. Moreover, it was discovered that the genipin cross-linked scaffold also provided the best conditions for hMSC cultivation. In addition, the infusions from all the scaffolds were found to be non-cytotoxic. Thus, the genipin and EDC/NHS/PBS cross-linked scaffolds can be considered to be promising biomaterials for further in vivo testing and bone surgery applications.

Evaluation of sericin as a fetal bovine serum-replacing cryoprotectant during freezing of human mesenchymal stromal cells and human osteoblast-like cells.

A reliable, cryoprotective, xeno-free medium suitable for different cell types is highly desirable in regenerative medicine. There is danger of infection or allergic reaction with the use of fetal bovine serum (FBS), making it problematic for medical applications. The aim of the present study was to develop an FBS-free cryoprotective medium for human mesenchymal stromal cells (hMSCs; primary cells) and immortalized human osteoblasts (SAOS-2 cell line). Furthermore, we endeavored to eliminate or reduce the presence of dimethyl sulfoxide (DMSO) in the medium. Sericin, a sticky protein derived from the silkworm cocoon, was investigated as a substitute for FBS and DMSO in the freezing medium. Cell viability (24 hours after thawing, both hMSC and SAOS-2) and colony-forming ability (2 weeks after thawing, only for hMSCs) were both determined. The FBS-free medium with 1% sericin in 10% DMSO was found to be a suitable freezing medium for primary hMSCs, in contrast to immortalized human osteoblasts. Surprisingly, the storage of hMSCs in a cultivation medium with only 10% DMSO also provided satisfactory results. Any drop in DMSO concentration led to significantly worse survival of cells, with little improvement in hMSC survival in the presence of sericin. Thus, sericin may substitute for FBS in the freezing medium for primary hMSCs, but cannot substitute for DMSO.