Biomedical Engineering Reference
In-Depth Information
Drug delivery options used in orthopedics
(a) Coating
- Cap
- Polymer
- Porous
- Porous/polymer
(b) Biomaterials/cement
(c) Beads
- Cap
- Polymer
- Composite (CaP/poly.)
- Cap
- Polymer
FIGURE 10.4
Drug delivery options used in orthopedics: (a) drug coating on an implant, (b) drug incorporation in a scaffold
or cement, and (c) drug incorporation in beads, as described by Pioletti et al. (
Current Drug Delivery
, 5, 59-63,
2008; with permission).
BP are generally delivered from a CaP coating. In particular, calcium-deficient apatites
(CDA) have been used to complex with BP such as zoledronate (Roussiere et al., 2005).
Release is controlled by disassociation of the complex. The efficacy of the BPs has been
demonstrated in an in vivo study involving rats (Peter et al., 2005). Here, a titanium implant
was inserted into the femur, and bone density was followed as a function of distance from
the implants. The implants were first coated with hydroxyl apatite sing plasma and then
soaked in zoledronate solutions of varying concentrations to obtain a range of BP loadings,
ranging from 0.2 to 16
μ
g. Bone density correlated well with loading, clearly demonstrating
the efficacy of local delivery of BP.
rhBMP was delivered locally from a carrier and tested in a canine total hip arthroplasty
(THP) model (Bragdon et al., 2003). The localized delivery did enhance bone formation
near the implant. Such an approach does appear promising, but the cost and the dose
needed may prove to be prohibitive.
In summary, the local delivery of BPs from a CaP coating appears to be the closest to
clinical examination, although there are no reports to date of such trials.
BioactiveCoatingsII:SurfaceModificationforCellularInteractions
Drug or other bioactive elution from coatings has been commercially successful. However,
that approach has a temporal limitation in that the effect lasts only as long as the drug is
being eluted. To make the “coating” more permanent, researchers have been exploring
the use of surface modification techniques. Most of these attempts have been focused on
improving biocompatibility, particularly blood compatibility and osteointegration.
