29. Jahrestagung der Deutschen Gesellschaft für Biomaterialien

Prof. Dr.

Chair

Amino group density of amine-based polymer coatings correlates with cell response

Cell-material interactions

Tissue regeneration/regenerated medicine

Abstract text (incl. figure legends and references) Demographic change in industrialized countries results in an increased incidence of osteoporosis. Most of the implants are not adapted for use in systemically diseased bone and therefore, osseointegration is a challenge. Amine-based coatings improve initial cell attachment, and signaling1,2. The question arose if there is a correlation between amino group density and cell response. Covalent grafting of polymer-based nano-coatings on titanium (ZfM Chemnitz) with different amino group densities was prepared by INNOVENT e.V., e.g. trimethoxysilylpropyl modified poly(ethyleneimine (TMS-PEI). For protein adsorption, size-exclusion HPLC was used (λ 215 nm). WCA, zeta potential and XPS characterized the surface coatings. Cell areas (PKH-26) of human MG-63 cells (ATCC®) were determined via LSM780 (Carl Zeiss), and differential gene expression via ClariomTM S microarrays (Applied Biosystems). Interestingly, a correlation exists between amino group density and cell spreading (Fig. 1). TMS-PEI offers the highest amino group density (N/C 32.2%) and positive surface charges, which is preferred by cells2. A premature activation of cell proliferation and differentiation was identified. BSA adsorption is highest on TMS-PEI compared to Ti-Ref. The fact that differentiation on amine-based coatings is enhanced has already been shown, but no microarray data are available now. The effects of TMS-PEI could compensate for the age-related slowing of osteoblast proliferation3 and thus promote osseointegration. Fig. 1: MG-63s on different polymer coatings with increased amino group density. TMS-PEI pushed significantly the cell spreading after 30 min. References Chen S. et al., Colloids Surf B Biointerfaces, 164:58-69, 2018 Gruening M. et al., Front Bioeng Biotechnol, 8:1016, 2020 Rauner M. et al., Age (Dordr), 30(4):273-82, 2008 Acknowledgments: Funded by the (i) ANR-DFG NLE2020 (DFG NE560/19-1, SCHN1099/9-1, no. 446225522) and (ii) Agence Nationale de la Recherche (ANR-20-CE92-0032).

Short Talk

Professor

Modulation of the platelets adhesion and activation by TiO2 crystallographic orientation-dependent fibrinogen conformation

Implant associated

Abstract text (incl. figure legends and references) One of the most frequently used materials for biomedical applications is titanium oxide (TiO2) in rutile form. However, thrombogenic phenomena, i.e., pathologic clot formation on the implant surface, is still problematic and can lead to many complications if a clot detaches and enter the bloodstream. The clot formation process is governed by the activation and aggregation of platelets. Their behavior is controlled by pre-adsorbed proteins, especially human blood plasma fibrinogen (HPF), and HPF conformation-dependent availability of the specific platelet recognition sites (γ400-411). The aim of this study was the examination how the crystallographic orientation of the material surface modulates HPF-mediated platelets adhesion. Firstly, atomic force microscopy (AFM) visualization of individual protein molecules revealed distinct HPF conformations (trinodular or globular) depending on the crystal. Furthermore, analysis of AFM-based adhesion forces showed statistically significant changes in surface energies of HPF-covered rutile surfaces, which was linked to HPF conformation. Subsequently, scanning electron microscopy (SEM) and confocal microscopy visualization of platelets demonstrated significant changes in cell adhesion and activation. It has been proved that platelets state is correlated with a conformation of pre-adsorbed HPF and HPF conformation-dependent availability of the γ400-411. We proposed a new possibility to control HPF conformation, and thus platelet adhesion and activation by adjusting the crystallographic orientation of the underlying material surface. This mechanism is driven by crystallographic orientation-dependent surface energy and wettability. It can contribute to the design and development of anti-thrombogenic titanium-based biomaterials.

Mimicking bone marrow sinusoids of vascular hematopoietic stem cell niches

Abstract text (incl. figure legends and references) Introduction Hematopoietic stem and progenitor cells (HSPCs) are indispensable for treating many hematological malignancies. Recreating their natural microenvironment – their niches – in vitro is one potential way to gain control and program their behavior ex vivo. Besides the endosteal niche close to the endosteum, perivascular niches were described in the vicinity of small blood vessels including bone marrow sinusoids, which are are specialized, single-cell-walled, fenestrated blood vessels with a discontinuous basal lamina. Objectives In the current project, we aimed to mimic vascular HSPC niches at bone marrow sinusoids, with particular emphasis on their microvascular nature and the specialized basal lamina. Methods Nanofibrous fibrinogen scaffolds were used to mimic the basal lamina of bone marrow sinusoids. The biomaterial was seeded with microvascular endothelial cells from one and mesenchymal stem/stromal cells from the other side to mimic the inner endothelial layer of microvasculature and the outer layer of vessel-associated stromal cells, respectively. HSPCs were introduced to either the stromal or the endothelial side to imitate residing in or homing to the niche. Results We observed that HSPCs proliferate more in triple cocultures than in double or single cultures on the scaffolds. Furthermore, maintenance of the HSC marker CD34 and abundance of hematopoietic cytokines were affected by presence of scaffolds and the different cell types in double and triple cocultures. The layered model of the vascular niche allowed migration of HSPCs through the scaffold, showing that the nanofibrous fibrinogen scaffolds are a suitable model for the fenestrated basal lamina. Conclusions The presented model mimics crucial aspects of bone marrow sinusoids of vascular HSPC niches and allows investigations of related cell-cell and cell-matrix interactions. Thus, this model is one step towards the goal of functional, biomimetic models of the vascular HSPC niche.

Regulating keratinocyte functions using polydopamine-based janus film

Abstract text (incl. figure legends and references) Question: Polydopamine (PDA) gains significant attention for biomedical applications, which conventionally is generated via the polymerization of dopamine and deposits onto substrate [1]. Recent studies show that PDA films can be formed at the air/liquid interface, which can be transferred onto substrates [2]. The potentials of PDA films for guiding cell behaviors were explored by investigating the physical, chemical, and bioinstructive properties of the PDA film, compared to the PDA coating. Methods: Dopamine was used as the precursor for the synthesis of PDA, and the resulting PDA materials were collected from either the liquid/solid (coating) or the air/liquid (film) interface. Results: The results showed that the thickness of the PDA coating was ~ 20 nm, while the thickness of the PDA film was ~ 100 nm. Significantly, the top and bottom surfaces of the PDA film possessed distinct properties, including surface roughness, elasticity, adhesion, and surface chemistry, which were characterized by atomic force microscopy (AFM), Raman spectroscopy, and X-ray photoelectron spectroscopy. Of note, the AFM-based single-cell force spectroscopy demonstrated that the bottom surface of the PDA film showed a higher binding affinity to keratinocytes, compared to the PDA coating and the top surface of the PDA film. Consequently, the difference in the cell-PDA adhesion led to changes in the gene expression profiles. Conclusions: PDA materials generated at different interfaces could guide diverse cellular behaviors, demonstrating the ease and versatility of using PDA surface modification to modulate cell functions. Together, developments in PDA-based materials hold great potential to advance fields such as tissue engineering and regenerative medicine. Reference [1] J. H. Ryu, P. B. Messersmith, H. Lee, Acs Appl Mater Inter 2018, 10, 7523. [2] E. Coy, I. Iatsunskyi, J. C. Colmenares, Y. Kim, R. Mrówczyński, Acs Appl Mater Inter 2021, 13, 23113.

PD Dr.

Promotion of wound healing with zinc oxide nanoparticles

Abstract text (incl. figure legends and references) Question: There is a growing need for biomaterials in medicine. Considering the demographic change, it's clear that it is becoming more and more important to handle comorbidities that hinder the tissue integration of biomaterials. In addition to preventing bacterial infection, it is essential to actively support the tissue regeneration of biomaterials. Since zinc is involved in the modulation of wound healing and the immunological response to foreign materials, we propose zinc oxide nanoparticles as a novel agent to improve the tissue integration of biomaterials. Methods: We analyzed the antibacterial properties of zinc oxide nanoparticles using bacterial growth assays. In addition, we investigated the interaction between zinc oxide nanoparticles and fibroblasts, endothelial cells, and macrophages by measuring their cellular metabolic activity. Finally, the biocompatibility and potential angiogenesis-modulating effects of zinc oxide nanoparticles were investigated in the chorioallantoic membrane (CAM) of fertilized chicken eggs. Results: Our study could confirm the antibacterial properties of zinc oxide nanoparticles. Bacterial growth was significantly reduced by concentrations of 50 μg/ml zinc oxide nanoparticles or higher in comparison to untreated bacterial control cultures. In addition, we demonstrated for the first time that zinc oxide nanoparticles stimulated the metabolic activity of fibroblasts and endothelial cells in vitro. By using the chicken embryo CAM, we also demonstrated the high biocompatibility of zinc oxide nanoparticles in a living organism. Conclusion: In conclusion, we found that zinc oxide nanoparticles have favorable properties to modulate wound healing and the immunological response to foreign materials while containing bacterial infection at the site of surgical trauma. Thus, the incorporation of zinc oxide nanoparticles into biomaterials could help to improve their tissue integration.

Artificial 3D cell models – key technology for biomedical applications

Additive manufacturing (e. g. 3D printing)

Clinical applications and translation

Abstract text (incl. figure legends and references) Introduction Structural functionalities, regulatory processes and interactions of living matter follow the principle of three-dimensionality. Research of properties and functions of living structures requires suitable approaches that can replicate these functionalities in the laboratory. 3D cell models have become very important for research approaches and drug testing. Objectives This lecture is intended to provide an overview of the strategies and methods used at the iba to make three-dimensional cell models available as carrier structures for pathogenicity research and biomedical application. Materials and Techniques The iba uses two-photon polymerisation and bioprinting to produce three-dimensional carrier structures. By choosing suitable polymerizable materials, carriers are available which correspond to the biochemical and mechanical characteristics of native matrices. Stem cells are increasingly being used to build complex cell models. Cell differentiation can be controlled by various bioactive surface modifications. Microfluidic chip applications are ideal so that cell models can be used efficiently for biomedical and pharmacological research. Examples of bone-cartilage tissue engineering, multi-organ chips and infection research are presented. Conclusion and Outlook Bioprinting and laser-based structuring processes in connection with stem cells are a powerful tool for the production of artificial 3D cell models. The field of application is very broad and ranges from differentiation and pathogenicity studies, from studies to optimize therapy as part of personalized medical care to pharmacological drug tests with high practical relevance. Future chip applications based on artificial cell models will help to better understand pathogenic processes and to be able to provide efficient therapeutic approaches.

Short Talks 3
Cell-Material Interaction

Appointment

Chair

Topic

Programme

Short Talks 3Cell-Material Interaction

Appointment

Chair

Topic

Programme

Short Talks 3
Cell-Material Interaction