Table 6.

Summary of different methods to immobilize bioactive molecules onto the surface of metallic implants.

Immobilization method		Biological molecule	Substrate and pre-treatment	Results	Ref.
Adsorption		Bone morphogenetic protein-3 (BMP-3)	Corundum-blasted Titanium alloy; Hydroxyapatite coated Titanium alloy; Ti coated Titanium alloy	BMP-3 coated samples showed more ability to induce new bone formation compared to those without BMP-3	[251]
Covalent immobilization	by chemical pretreatment	Synthetic receptor binding motif mimicking BMP-2	3-aminopropyltriethoxysilane (APTES) coated Titanium	enhance the rate of bone healing as compared with untreated Ti surfaces	[252]
		Laminin and human epidermal growth factors (EGF)	Silanized TiO2-film Silanisation by reaction of GPTS1	Significantly reduce the amount of irreversibly adsorbed salivary proteins	[253]
		Heparin	Silanized and oxidized Titanium Oxidization by H2SO4/30% H2O2 or annealing at 750 °C; Silanisation by being boiled in APMS2 contained toluene soltution	The remaining activity of heparin is depending on the chain length of spacer	[243]
	by plasma-based modification	Fibronectin	Plasma polymerization of HMDSO3 on Titanium	Enhanced adsorption of fibronectin	[254]
		BMP-4	Plasma polymerization of allyl amine on Titanium alloy	Surfaces with BMP-4 are initially able to induce ALP activity in C3H10T1/2 cells, long term effect is depending on the concentration of surface amino group	[250]
Incorporation with carriers		Recombinant human BMP-2 (rhBMP-2)	Turned or surface etched Titanium dental implant Absorbable Collagen sponge (ACS)	rhBMP-2/ACS significantly enhances the effect of guided bore regeneration (GBR)	[255]
		BMP-2; insulin-like growth factor-1 and transforming growth factor-β1	Titanium Kirschner wires incorporated with poly(D,L-lactide) (PDLLA)	Significantly accelerate the fracture healing	[256,257]

GPTS¹: (3-glycidyloxypropyl)trimethoxysilane; APMS²: 3-(Trimethoxysilyl)-propylamine; HMDSO³: Hexamethyldisiloxane