Bioresorbable implant materials are in great demand for the repair of bone defects in reconstructive surgery. Many investigated biomaterials consist of calcium phosphates which excel in their biocompatibility, bioactivity and osteoconductivity. However, many commercially available products are limited for clinical applications because of their brittleness, incompressibility and difficulty to shape.
treatment is one of the major issues in dental science with more than 20 mio
treatments per year in the USA. Conventional medications like calcium hydroxide
are used for disinfection of the root canal (killing of bacteria). However, it
attacks the dentine and makes the tooth more prone to fracture. A possible
alternative to this material are bioactive glasses. This class of biomaterials
does not only disinfect a root canal it forms also crystalline apatites, main
component of the root canal, on its surface when immersed in simulated
bodyfluids and it does not attack the dentine. Using nanotechnology the
formation of this apatite and the reactivity of such bioactive glass can be
enhanced via the high specific surface area. Bioactive glasses are tailored
using the flame spray synthesis process in order to improve the current root
canal treatment in collaboration with the dental hospital of the University of
Bioactive glass doped with up to 50wt% bismuth oxide to render the
particles visible on X-ray images.
Bioactive glass is mixed with a sterile NaCl solution (left) and applied into an artificial root canal by a lentulo spiral (right).
A highly bioactive network of
fibers was synthesized by electrospinning using flame sprayed amorphous calcium
phosphate (a-CaP) nanoparticles and biodegradable poly(lactide-co-glycolide)
(PLGA). In vitro degradation in simulated body fluid (SBF) showed that
significant deposition of a nano-featured hydroxyapatite layer occurred only on
the surface of a-CaP doped PLGA as followed using scanning electron microscopy.
This compressible and cotton-wool like biomaterial suggests application for
complex shaped and non-load bearing bone defects as they appear for example in
dental surgery. The in vivo bone
regeneration of this easy applicable biomaterial was investigated in
cooperation with the University Hospital in Zurich
by creating calvarial defects in New Zealand White rabbits. Histological and
micro-computed tomographic analysis after four weeks implantation showed a
spongiosa-like structure of newly formed bone tissue. Furthermore we improved
the material’s properties towards an antibacterial implant by using silver
containing ATCP nanoparticles without influencing the bioactivity. A study in sheep using a drill
hole defect model in the femur and humerus showed that both PLGA/a-CaP and
PLGA/Ag-a-CaP scaffolds are biocompatible and that the fibrous material allows
bone formation even at the center of former defects.
The cotton wool-like PLGA/a-CaP scaffolds enable fast
mineralization when coming in contact with body fluid and are easy-to-apply by
Electrospinning was used to produce a double membrane, which
presents two different fronts. One front was made of a-CaP carrying collagen
fibres strengthened with PLGA, the opposite front was composed of pure PLGA
fibres. The mineral : collagen ratio was similar to the one in bone and hence
not only the fibrous structure of bone tissue was mimicked but also its
composition. In vitro
biomineralisation was observed for the aCaP/Col/PLGA fibres in an SBF study. Incubation
of hMSC for 4 weeks allowed for assessment of the proliferation and osteogenic
differentiation of the cells on both sides of the double membrane.
The anisotropic pliable bilayer of a-CaP/Col/PLGA (dyed with Brilliant Blue) on pure PLGA could be given a spherical shape and was positioned on a femur head model. This flexibility indicates possible application as wound wrapping material.
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