Bone-Like Mineral and Organically Modified Bone-Like Mineral Coatings - Biological and Biomedical Coatings: Processing and Characterization - page 19

For instance, BMP-2 adsorbed on a titanium implant coated with BLM shows a transient
release up to 1 week and a sporadic osteogenic response over a 5-week period (Liu, de
Groot, and Hunziker 2005).

Surface Adsorption of Peptides to BLM to Enhance Cellular Attachment

Immediately after placing an implant in the body, a protein layer is adsorbed from the sur-
rounding body fluids onto the implant surface, and this protein layer is largely responsible
for recruiting cell populations to its surface and mediating all subsequent cellular events
(Horbett 2004). An approach that utilizes this adsorbed protein coating to dictate cellular
events at the implant surface involves adsorption of adhesive proteins found in the natu-
ral bone ECM onto biomaterials, thus attempting to mimic the cell-matrix interactions
occurring in vivo. Recognition of specific domains/motifs found within these proteins
causes the cells to activate signaling pathways, ultimately resulting in cell proliferation,
differentiation, and new bone formation. However, the use of recombinant human and
animal proteins in vivo has several disadvantages, including adverse immune responses,
enzymatic degradation, and changes in conformation arising from protein-material inter-
actions. Also, proteins usually contain several domains that may be involved in medi-
ating attachment of different types of cells, leading to the possibility of nonspecific cell
binding.
Synthetically designed peptides that mimic specific portions of these proteins are able to
overcome many of these drawbacks. Table 1.6 provides a list of peptides used in bone tissue
engineering. Apart from being cheaper to produce and easier to characterize, peptides are
smaller in length (typically 12-30 amino acids) and are less likely to form secondary and
tertiary structures, and hence are not affected by changes in conformation. Also, peptides
can be engineered to contain domains that are specific to the desired type of cell surface

TABLE 1.6
Examples of Peptides Used in Bone Tissue Engineering Applications

PeptideSequence Source/Derivedfrom Function Reference

EEEEEEEPRGDT Bone sialoprotein Enhances osteoblast adhesion

and differentiation

Fujisawa et al. 1997;
Itoh et al. 2002

VTKHLNQISQSY Phage display Specific affinity toward

bone-like mineral (BLM)

Segvich, Smith, and
Kohn 2009

KIPKASSVPTELSAISTLYL BMP2, osteocalcin Promotes osteogenic

differentiation of human
mesenchymal stem cells

Lee, Lee, and
Murphy 2009

RGDG13PHSRN Fibronectin Enhances osteoblast adhesion

and differentiation

Benoit and Anseth
2005

KRSR Heparin Enhances osteoblast adhesion Dee, Andersen, and

Bizios 1998

DVDVPDGRGDSLAYG Osteopontin Enhances osteoblast

attachment and
differentiation

Shin et al. 2004a,
2004b

SVSVGMKPSPRP Phage display Specific affinity toward

hydroxyapatite

Roy et al. 2008

(DSS)n Dentin

phosphoprotein

Specific affinity toward
calcium phosphate

Yarbrough et al. 2010

Source: Segvich and Kohn 2009, with kind permission from Springer Science + Business Media.