Bioinspired Materials

Simulated body fluids (SBF) with a composition similar to the inorganic part of the human blood plasma were used for in vitro bioactivity tests. Beyond that, SBF was used to precipitate biomimetic apatite with a composition, morphology, and growth orientation equal to the mineral part of the vertebrate bone. The photoluminescence of annealed biomimetic apatite might be of specific interest for histological probing and monitoring of bone re-modelling. SBF solutions with modified ion concentrations and increased super­saturation were used to accelerate the formation of apatite and to coat various materials with bioactive calcium phosphate.

DOI: 10.1016/j.msec.2017.08.032External link
DOI: 10.1111/jace.15736External link

The wet-chemical synthesis of nano-sized, bioactive or resorbable calcium phosphate powders is of particular interest for the development of load-bearing orthopedical implants. Ionic substitutions were performed to affect the solubility of the material and to enhance its bio-acceptance. The mechanical properties of sintered calcium phosphates were significantly increased by vacuum synthesis technologies. Biomimetic techniques were used to synthesise hydroxy apatite powders with a bone-like composition. Sol-gel processes were used to prepare bioactive sodium titanate ceramics and SiO₂-CaO-glasses, respectively.

DOI: 10.3390/ma11020192External link // DOI: 10.3390/ma11091610External link

Calcium phosphate cements (CPCs) are a promising material for bone tissue regeneration, especially after tumor removal or tooth extraction, due to their biocompatibility and osteoconductive properties. However, due to their inherent brittleness, the application of such CPCs has so far been limited to non-load bearing bone areas. For this reason, we developed a damage-tolerant CPC in which the incorporation of functionalized carbon fibers allows steady state, flat crack propagation with crack openings smaller than 10 µm in the event of damage. A subsequent self-healing process in simulated body fluid (SBF), which mimics the in vivo mineralization of bioactive surfaces in vitro, closes the cracks and fully restores the mechanical properties. Two pathways of self-healing were investigated: (i) intrinsic healing, based on the bioactive properties of the cement matrix and chemically treated C-fibers, allowing nucleation of apatite at the crack flanks and fiber surfaces, and (ii) extrinsic self-healing, in which H₂PO^4- is released from polymeric capsule systems opened by a propagating crack as an initiator for apatite formation, resulting in complete mineralization of the cracks through local supersaturation of PO₄^3- ions. In this process, the self-healing capacity of CPC is maintained even with repeated damage over several cycles. Damage-tolerant, self-healing CPCs are of particular interest to increase the lifetime of calcium phosphate-based implants and to extend their application potential to load-bearing areas.

DOI: 10.1038/s41598-020-66207-2External link

Bacterial Nanocellulose (BNC)

Cellulose is the world´s most abundant biopolymer. Langmuir-Blodgett monolayers, fibres and knits made of cellulose were used to prepare scaffolds and drug delivery systems for the regeneration of bone and cartilage. The coagulation and co-extrusion of cellulose/hydroxy apatite solutions were used to prepare composite tapes and fibres, respectively.

Photocatalytically active hybrids consisting of anatase nano­particles (NP) and bacterial nanocellulose were prepared by dispersing the NP into the Hestrin-Schramm culture medium. In contact with air the bacteria produce cellulose from glucose and simultaneously integrate the NP homogeneously in the BNC hydrogel. The antibacterial activity of such kind of materials was demonstrated by methanol conversion (MC) under UV irradiation. Thus, the in situ integration of NPs into BNC represents an attractive possibility to extend its use to novel innovative fields of application.

DOI: dx.doi.org/10.1021/la302787zExternal link // DOI: 10.1039/C4RA09898FExternal link