Tendon augmentation is increasingly clinically relevant due to rising amount of tendon ruptures because of the aging and more demanding population. Therefore, newly developed scaffolds based on bovine epoxide stabilized collagen maintaining the native fibril-like collagen structure were characterized and compared to two commercially available porcine collagen scaffolds. For biomechanical testing (ultimate load, ultimate stress, stiffness, and elastic modulus), bovine collagen scaffolds were hydrated and compared to reference products. Cell viability and proliferation were assessed by seeding human primary fibroblasts on each collagen-based scaffold and cultured over various time periods (3 d, 7 d, and 14 d). Live/dead staining was performed and metabolic cell activity (WST-1 assay) was measured. Biochemical degradability was investigated by enzymatic digestion. The bovine collagen scaffold showed significantly enhanced biomechanical properties. These persisted over different rehydration times. Cell biological tests revealed that the bovine collagen scaffolds support reproducible cell colonization and a significant increase in the number of viable cells during cultivation. The results are comparable with the viability and proliferation rate of cells grown on porcine reference materials. With regard to biochemical degradability, all tested materials showed comparable resistance to enzymatic degradation in vitro. Due to imitating the natural tendon structure the new scaffold material is supposed to provide beneficial effects in future clinical application.

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Detonation nanodiamonds (NDs) are a novel class of carbon-based nanomaterials, and have received a great deal of attention in biomedical applications, due to their high biocompatibility, facile surface functionalization, and commercialized synthetic fabrication. We were able to transfer the NDs from large-size agglomerate suspensions to homogenous coatings. ND suspensions have been used in various techniques to coat on commercially available substrates of pure Ti and Si. Scanning electron microscopy (SEM) imaging and nanoindentation show that the densest and strongest coating of NDs was generated when using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide (EDC/NHS)-mediated coupling to macroscopic silanized surfaces. In the next step, the feasibility of DNA-mediated coupling of NDs on macroscopic surfaces is discussed using fluorescent microscopy and additional particle size distribution, as well as zeta potential measurements. This work compares different ND coating strategies and describes the straightforward technique of grafting single-stranded DNA onto carboxylated NDs via thioester bridges.

Human mesenchymal stem cells (hMSCs) are well-known for their immunomodulatory potential. In recent clinical trials and in vivo studies, hMSCs were used as therapeutic measures to dampen inflammation. In this context, their effect on macrophages in vivo has been described to induce a phenotype change shifting from a proinflammatory to an anti-inflammatory environment. Despite several in vitro studies that investigated the potential of hMSCs to inhibit the polarization of macrophages into the proinflammatory M1 subtype, it is still unclear if hMSCs affect polarized M1 macrophages or if they control the environment by inhibiting the M1 polarization of unpolarized macrophages. Here, a comparative in vitro investigation of hMSC immunomodulation via soluble factors concerning the influence on the polarization of macrophages to M1 and on polarized M1 macrophages is presented. Human primary monocyte-derived macrophages (hMDMs) as well as THP-1 cells were used for this investigation. The macrophage subtype was analyzed by gene expression as well as cytokine secretion. hMSCs affected cytokine secretion of polarizing macrophages, while changes in gene expression were evident in polarized M1 macrophages. These effects were observed in THP-1 and hMDM macrophages. In conclusion, we suggest that hMSCs implement their immunomodulatory effects on polarizing and polarized macrophages in different ways.