Bioinformatics-based selection of a model cell type for in vitro biomaterial testing

Research progress of implantation materials and its biological evaluation

With the development of modern material science, life science and medical science, implantation materials are widely employed in clinical fields. In recent years, these materials have also evolved from inert supports or functional substitutes to bioactive materials able to trigger or promote the regenerative potential of tissues. Reasonable biological evaluation of implantation materials is the premise to make sure their safe application in clinical practice. With the continual development of implantation materials and the emergence of new implantation materials, new challenges to biological evaluation have been presented. In this paper, the research progress of implantation materials, the progress of biological evaluation methods, and also the characteristics of biocompatibility evaluation for novel implantation materials, like animal-derived implantation materials, nerve contact implantation materials, nanomaterials and tissue-engineered medical products were reviewed in order to provide references for the rational biological evaluation of implantable materials.

Phenotypic stability of the human MG-63 osteoblastic cell line at different passages

One of the most popular cell lines in osteogenesis studies is the human osteoblastic line MG-63. For cell biological investigation, it is important that the cells remain stable in their phenotype over several passages in cell culture. MG-63 cells can be used to provide fundamental insights into cell--material interaction. The aim of this study is to present a systematic characterization of the physiological behavior of MG-63 cells in the range of passages 5-30. Significant cell physiology processes during the first 24 h, including cell morphology, availability of adhesion receptors, cell cycle phases, as well as the expression of the signaling proteins Akt, GSK3a/b, IkB-α, ERK1/2, p38-MAPK, and intracellular calcium ion mobilization, remained stable over the entire range of passages P5-P30. Due to these stable characteristics in a wide range of cell culture passages, MG-63 cells can be considered as a suitable in vitro model to analyze the biocompatibility and biofunctionality of implant materials.

Development of a microfluidic platform integrating high-resolution microstructured biomaterials to study cell-material interactions

Microfluidic screening platforms offer new possibilities for performing in vitro cell-based assays with higher throughput and in a setting that has the potential to closely mimic the physiological microenvironment. Integrating functional biomaterials into such platforms is a promising approach to obtain a deeper insight into the interactions occurring at the cell-material interface. The success of such an approach is, however, largely dependent on the ability to miniaturize the biomaterials as well as on the choice of the assay used to study the cell-material interactions. In this work, we developed a microfluidic device, the main component of which is made of a widely used biocompatible polymer, polylactic acid (PLA). This device enabled cell culture under different fluidic regimes, including perfusion and diffusion. Through a combination of photolithography, two-photon polymerization and hot embossing, it was possible to microstructure the surface of the cell culture chamber of the device with highly defined geometrical features. Furthermore, using pyramids with different heights and wall microtopographies as an example, adhesion, morphology and distribution of human MG63 osteosarcoma cells were studied. The results showed that both the height of the topographical features and the microstructural properties of their walls affected cell spreading and distribution. This proof-of-concept study shows that the platform developed here is a useful tool for studying interactions between cells and clinically relevant biomaterials under controlled fluidic regimes.

Linking the Transcriptional Landscape of Bone Induction to Biomaterial Design Parameters

New engineering possibilities allow biomaterials to serve as active orchestrators of the molecular and cellular events of tissue regeneration. Here, the molecular control of tissue regeneration for calcium phosphate (CaP)-based materials is established by defining the parameters critical for tissue induction and those are linked to the molecular circuitry controlling cell physiology. The material properties (microporosity, ion composition, protein adsorption) of a set of synthesized osteoinductive and noninductive CaP ceramics are parameterized and these properties are correlated to a transcriptomics profile of osteogenic cells grown on the materials in vitro. Using these data, a genetic network controlling biomaterial-induced bone formation is built. By isolating the complex material properties into single-parameter test conditions, it is verified that a subset of these genes is indeed controlled by surface topography and ions released from the ceramics, respectively. The gene network points to a decisive role for extracellular matrix deposition in osteoinduction by genes such as tenascin C and hyaluronic acid synthase 2, which are controlled by calcium and phosphate ions as well as surface topography. This work provides insight into the biomaterial composition and material engineering aspects of bone void filling and can be used as a strategy to explore the interface between biomaterials and tissue regeneration.

Biodegradation and Osteosarcoma Cell Cultivation on Poly(aspartic acid) Based Hydrogels

Development of novel biodegradable and biocompatible scaffold materials with optimal characteristics is important for both preclinical and clinical applications. The aim of the present study was to analyze the biodegradability of poly(aspartic acid)-based hydrogels, and to test their usability as scaffolds for MG-63 osteoblast-like cells. Poly(aspartic acid) was fabricated from poly(succinimide) and hydrogels were prepared using natural amines as cross-linkers (diaminobutane and cystamine). Disulfide bridges were cleaved to thiol groups and the polymer backbone was further modified with RGD sequence. Biodegradability of the hydrogels was evaluated by experiments on the base of enzymes and cell culture medium. Poly(aspartic acid) hydrogels possessing only disulfide bridges as cross-links proved to be degradable by collagenase I. The MG-63 cells showed healthy, fibroblast-like morphology on the double cross-linked and RGD modified hydrogels. Thiolated poly(aspartic acid) based hydrogels provide ideal conditions for adhesion, survival, proliferation, and migration of osteoblast-like cells. The highest viability was found on the thiolated PASP gels while the RGD motif had influence on compacted cluster formation of the cells. These biodegradable and biocompatible poly(aspartic acid)-based hydrogels are promising scaffolds for cell cultivation.

Exploring the Material-Induced Transcriptional Landscape of Osteoblasts on Bone Graft Materials

During the past decades, there have been major advances in the field of biomaterials, thereby generating a vast variety of materials for a broad range of tissue engineering and regeneration applications. Although gene expression profiling has been used occasionally in biomaterial research, its usefulness for understanding cell-biomaterial interactions should be further explored for it to fulfill its promise as a tool to assess and improve material properties. Here, the transcriptional landscape induced by 23 materials is explored with a variety of properties within the scope of bone regeneration. An osteoblast cell line is used to identify the gene expression profiles that can be adopted in response to biophysical and chemical cues. It is shown that TGF-β and WNT signaling may be involved in the cellular response to osteoinductive materials along with differential cell adhesion kinetics via attenuated FAK signaling. The previously reported effect of calcium and phosphate on BMP2 and TGF-β signaling is confirmed and the biological effect of the addition of nanohydroxyapatite in poly (d,l-lactic acid) polymer particles is studied. Together with future applications, this approach will help researchers understand cellular responses in relation to material properties, which will promote the development of more effective biomaterials for applications in tissue regeneration.

Laser photofabrication of cell-containing hydrogel constructs

The two-photon polymerization (2PP) of photosensitive gelatin in the presence of living cells is reported. The 2PP technique is based on the localized cross-linking of photopolymers induced by femtosecond laser pulses. The availability of water-soluble photoinitiators (PI) suitable for 2PP is crucial for applying this method to cell-containing materials. Novel PIs developed by our group allow 2PP of formulations with up to 80% cell culture medium. The cytocompatibility of these PIs was evaluated by an MTT assay. The results of cell encapsulation by 2PP show the occurrence of cell damage within the laser-exposed regions. However, some cells located in the immediate vicinity and even within the 2PP-produced structures remain viable and can further proliferate. The control experiments demonstrate that the laser radiation itself does not damage the cells at the parameters used for 2PP. On the basis of these findings and the reports by other groups, we conclude that such localized cell damage is of a chemical origin and can be attributed to reactive species generated during 2PP. The viable cells trapped within the 2PP structures but not exposed to laser radiation continued to proliferate. The live/dead staining after 3 weeks revealed viable cells occupying most of the space available within the 3D hydrogel constructs. While some of the questions raised by this study remain open, the presented results indicate the general practicability of 2PP for 3D processing of cell-containing materials. The potential applications of this highly versatile approach span from precise engineering of 3D tissue models to the fabrication of cellular microarrays.