1-Step Versus 2-Step Immobilization of Alkaline Phosphatase and Bone Morphogenetic Protein-2 onto Implant Surfaces Using Polydopamine

Abstract

Immobilization of biomolecules onto implant surfaces is highly relevant in many areas of biomaterial research. Recently, a 2-step immobilization procedure was developed for the facile conjugation of biomolecules onto various surfaces using self-polymerization of dopamine into polydopamine. In the current study, a 1-step polydopamine-based approach was applied for alkaline phosphatase (ALP) and bone morphogenetic protein-2 (BMP-2) immobilization, and compared to the conventional 2-step polydopamine-based immobilization and plain adsorption. To this end, ALP and BMP-2 were immobilized onto titanium and polytetrafluoroethylene (PTFE) substrates. The absolute quantity and biological activity of immobilized ALP were assessed quantitatively to compare the three types of immobilization. Plain adsorption of both ALP and BMP-2 was inferior to both polydopamine-based immobilization approaches. ALP was successfully immobilized onto titanium and PTFE surfaces via the 1-step approach, and the immobilized ALP retained its enzymatic activity. Using the 1-step approach, the amount of immobilized ALP was increased twofold to threefold compared to the conventional 2-step immobilization process. In contrast, more BMP-2 was immobilized using the conventional 2-step immobilization approach. Retention of ALP and BMP-2 was measured over a period of 4 weeks and was found to be similar for the 1-step and 2-step methods and far superior to the retention of adsorbed biomolecules due to the formation of covalent linkages between catechol moieties and immobilized proteins. The biological behavior of ALP and BMP-2 coatings immobilized using polydopamine (1- and 2-step) as well as adsorption was assessed by culturing rat bone marrow cells, which revealed that the cell responses to the various experimental groups were not statistically different. In conclusion, the 1-step polydopamine-based immobilization method was shown to be more efficient for immobilization of ALP, whereas the conventional 2-step method was shown to be more efficient for attachment of BMP-2 onto implant surfaces.

Effective Immobilization of BMP-2 Mediated by Polydopamine Coating on Biodegradable Nanofibers for Enhanced in Vivo Bone Formation

“…41 In a recent report, long-term release behavior of immobilized BMP-2 was analyzed over a period of 28 days from a polydopamine coated titanium surface and which showed excellent retention of growth factor even after 1 month. 42 To the best of our knowledge, we are reporting first time of a long-term release behavior of BMP-2 from a polydopamine-coated fibrous polymeric membrane. Long-term retention of immobilized growth factor is particularly relevant in the context of guided bone regeneration approaches, as the porous membrane expected to provide osteoinductivity for relatively longer period.…”

In vitro response to alkaline phosphatase coatings immobilized onto titanium implants using electrospray deposition or polydopamine‐assisted deposition

“…This assumption is further supported by studies that showed improved bone formation around scaffolds with covalently immobilized-and thus more tightly bound-ALP. 19,27 Despite the fact that the immobilization efficacy of ALP using polydopamine was confirmed in previous studies, 11 a final proof for the in vivo efficacy of poydopamine-assisted immobilization of ALP is still lacking and can only be provided by an orthotopic animal implantation study.…”

“…Inspired by the composition of mussel adhesive proteins, Messersmith and coworkers, 8,9 developed a dopamine-based method for immobilization of biomolecules onto a wide range of inorganic and organic materials via selfpolymerization of dopamine. This method has been used to immobilize numerous biomolecules, such as bone morphogenetic protein 2, 10,11 vascular endothelial growth factor, 12 bovine serum albumin (BSA), 13 and alkaline phosphatase (ALP) 11 onto a wide range of surfaces. Beside the use of polydopamine for biomolecule immobilization, it was shown that polydopamine coatings can decrease water contact angles on nonwetting surfaces to values of around 47 .…”

Materials from Mussel-Inspired Chemistry for Cell and Tissue Engineering Applications

“…While neither method affected biomolecule activity, it was suggested that the one-step and two-step process may be more appropriate for higher and lower concentrations of biomolecules, respectively. 86 …”