We thank Prof. J.P. Spatz (Department of Biophysical Chemistry, University of Heidelberg and Department of New Materials and Biosystems, Max Planck Institute for Intelligent Systems, Stuttgart) for his kind support. The financial support from the Max-Planck-Gesellschaft and the Deutsche Forschungsgemeinschaft (DFG SFB/TR79 to E.A.C.-A.) are also greatly acknowledged.

1. Synthesis of 11-Mercaptoundecanoyl-N-hydroxysuccinimide Ester (MU-NHS)
<ol>
	<li>Add dropwise a solution of 500 mg N-hydroxysuccinimide and 30 mg 4-(dimethylamino)pyridine in 10 ml acetone (p.a.) to 1 g 11-mercaptoundecanoic acid in 40 ml dichloromethane (p.a.) at room temperature (RT).</li>
	<li>Cool the reaction to 0 &#176;C and add dropwise 1.1 g N,N&#39;-dicyclohexylcarbodiimide in 10 ml dichloromethane (under nitrogen atmosphere). Keep the reaction at low temperature for 1 hr and then...

<ol>
	<li>Helm, G., Andersson, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Summary+statement:+Bone+morphogenetic+proteins:+Basic+science.">Summary statement: Bone morphogenetic proteins: Basic science.</a> Spine. 27 (16S), S9 (2002).</li><li>Hogan, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bone+morphogenetic+proteins:+multifunctional+regulators+of+vertebrate+development.">Bone morphogenetic proteins: multifunctional regulators of vertebrate development.</a> Genes Dev. 10 (13), 1580-1594 (1996).</li><li>Reddi, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=BMPs:+from+bone+morphogenetic+proteins+to+body+morphogenetic+proteins.">BMPs: from bone morphogenetic proteins to body morphogenetic proteins.</a> Cytokine Growth Factor Rev. 16, 249-250 (2005).</li><li>Rengachary, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bone+morphogenetic+proteins:+basic+concepts.">Bone morphogenetic proteins: basic concepts.</a> Neurosurg Focus. 13 (6), 1-6 (2002).</li><li>Schlunegger, M., Gru&#776;tter, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+unusual+feature+revealed+by+the+crystal+structure+at+2.2+&#197;;+resolution+of+human+transforming+growth+factor-&#946;2.">An unusual feature revealed by the crystal structure at 2.2 &#197;; resolution of human transforming growth factor-&#946;2.</a> Nature. 358, 430-434 (1992).</li><li>Scheufler, C., Sebald, W., Hu&#776;lsmeyer, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Crystal+structure+of+human+bone+morphogenetic+protein-2+at+2.7+&#197;+resolution.">Crystal structure of human bone morphogenetic protein-2 at 2.7 &#197; resolution.</a> J. Mol. Biol. 287 (1), 103-115 (1999).</li><li>Nimni, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Polypeptide+growth+factors:+targeted+delivery+systems.">Polypeptide growth factors: targeted delivery systems.</a> Biomaterials. 18 (18), 1201-1225 (1997).</li><li>Wozney, J., Rosen, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bone+morphogenetic+protein+and+bone+morphogenetic+protein+gene+family+in+bone+formation+and+repair.">Bone morphogenetic protein and bone morphogenetic protein gene family in bone formation and repair.</a> Clin. Orthop. 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Biol. 11 (5), 481-488 (2004).</li><li>Miyazono, K., Maeda, S., Imamura, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=BMP+receptor+signaling:+transcriptional+targets,+regulation+of+signals,+and+signaling+cross-talk.">BMP receptor signaling: transcriptional targets, regulation of signals, and signaling cross-talk.</a> Cytokine Growth Factor Rev. 16 (3), 251-263 (2005).</li><li>Nohe, A., Hassel, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+mode+of+bone+morphogenetic+protein+(BMP)+receptor+oligomerization+determines+different+BMP-2+signaling+pathways.">The mode of bone morphogenetic protein (BMP) receptor oligomerization determines different BMP-2 signaling pathways.</a> J. Biol. 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K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+critical+review+of+recombinant+human+bone+morphogenetic+protein-2+trials+in+spinal+surgery:+emerging+safety+concerns+and+lessons+learned.">A critical review of recombinant human bone morphogenetic protein-2 trials in spinal surgery: emerging safety concerns and lessons learned.</a> Spine J. 11, 471-491 (2011).</li><li>Luginbuehl, V., Meinel, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Localized+delivery+of+growth+factors+for+bone+repair.">Localized delivery of growth factors for bone repair.</a> Eur. J. Pharm. 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M., Boergermann, J. H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Surface+immobilization+of+bone+morphogenetic+protein+2+via+a+self-assembled+monolayer+formation+induces+cell+differentiation.">Surface immobilization of bone morphogenetic protein 2 via a self-assembled monolayer formation induces cell differentiation.</a> Acta Biomater. 8 (2), 772-780 (2012).</li><li>Love, J., Estroff, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Self-assembled+monolayers+of+thiolates+on+metals+as+a+form+of+nanotechnology.">Self-assembled monolayers of thiolates on metals as a form of nanotechnology.</a> Chem. Rev. 105 (4), 1103-1169 (2005).</li><li>Katagiri, T., Yamaguchi, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bone+morphogenetic+protein-2+converts+the+differentiation+pathway+of+C2C12+myoblasts+into+the+osteoblast+lineage.">Bone morphogenetic protein-2 converts the differentiation pathway of C2C12 myoblasts into the osteoblast lineage.</a> J. Cell Biol. 127 (6), 1755-1766 (1994).</li><li>Whitaker, M. J., Quirk, R. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Growth+factor+release+from+tissue+engineering+scaffolds.">Growth factor release from tissue engineering scaffolds.</a> J. Pharm. 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Res. 50 (2), 227-238 (2000).</li><li>Kashiwagi, K., Tsuji, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Directional+BMP-2+for+functionalization+of+titanium+surfaces.">Directional BMP-2 for functionalization of titanium surfaces.</a> Biomaterials. 30 (6), 1166-1175 (2008).</li><li>Karageorgiou, V., Meinel, V. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bone+morphogenetic+protein-2+decorated+silk+fibroin+films+induce+osteogenic+differentiation+of+human+bone+marrow+stromal+cells.">Bone morphogenetic protein-2 decorated silk fibroin films induce osteogenic differentiation of human bone marrow stromal cells.</a> J. Biomed. Mater. Res. 71 (3), 528-573 (2004).</li><li>Rose, F. R. A. 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Biosci. 11 (9), 1149-1163 (2011).</li><li>Crouzier, T., Fourel, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Presentation+of+BMP-2+from+a+soft+biopolymeric+film+unveils+its+activity+on+cell+adhesion+and+migration.">Presentation of BMP-2 from a soft biopolymeric film unveils its activity on cell adhesion and migration.</a> Adv. Mater. 23 (12), H111-H118 (2011).</li><li>Ruppert, R., Hoffmann, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Human+bone+morphogenetic+protein+2+contains+a+heparin-binding+site+which+modifies+its+biological+activity.">Human bone morphogenetic protein 2 contains a heparin-binding site which modifies its biological activity.</a> European Journal of Biochemistry. 237 (1), 295-302 (1996).</li><li>Love, J., Estroff, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Self-assembled+monolayers+of+thiolates+on+metals+as+a+form+of+nanotechnology.">Self-assembled monolayers of thiolates on metals as a form of nanotechnology.</a> Chem. Rev. 105 (4), 1103-1169 (2005).</li><li>Kato, K., Sato, H., Iwata, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Immobilization+of+histidine-tagged+recombinant+proteins+onto+micropatterned+surfaces+for+cell-based+functional+assays.">Immobilization of histidine-tagged recombinant proteins onto micropatterned surfaces for cell-based functional assays.</a> Langmuir. 21 (16), 7071-7075 (2005).</li><li>Martins, M., Curtin, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Molecularly+designed+surfaces+for+blood+deheparinization+using+an+immobilized+heparin-binding+peptide.">Molecularly designed surfaces for blood deheparinization using an immobilized heparin-binding peptide.</a> J. Biomed. Mater. Res. 88 (1), 162-173 (2009).</li><li>Limbut, W., Kanatharana, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+comparative+study+of+capacitive+immunosensors+based+on+self-assembled+monolayers+formed+from+thiourea,+thioctic+acid,+and+3-+mercaptopropionic+acid.">A comparative study of capacitive immunosensors based on self-assembled monolayers formed from thiourea, thioctic acid, and 3- mercaptopropionic acid.</a> Biosens. Bioelectron. 22 (2), 233-240 (2006).</li><li>Patel, N., Davies, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Immobilization+of+protein+molecules+onto+homogeneous+and+mixed+carboxylate-terminated+self-assembled+monolayers.">Immobilization of protein molecules onto homogeneous and mixed carboxylate-terminated self-assembled monolayers.</a> Langmuir. 13 (24), 6485-6490 (1997).</li><li>Hu, J., Duppatla, V., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Site-specific+PEGylation+of+bone+morphogenetic+protein-2+cysteine+analogues.">Site-specific PEGylation of bone morphogenetic protein-2 cysteine analogues.</a> Bioconjug. Chem. 21 (10), 1762-1772 (2010).</li><li>Hersel, U., Dahmen, C., Kessler, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=RGD+modified+polymers:+biomaterials+for+stimulated+cell+adhesion+and+beyond.">RGD modified polymers: biomaterials for stimulated cell adhesion and beyond.</a> Biomaterials. 24 (24), 4385-4415 (2003).</li><li>Cao, T., Wang, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Investigation+of+spacer+length+effect+on+immobilized+Escherichia+coli+pili-antibody+molecular+recognition+by+AFM.">Investigation of spacer length effect on immobilized Escherichia coli pili-antibody molecular recognition by AFM.</a> Biotechnol. 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Authors have nothing to disclose.

In this protocol we describe the preparation of surfaces functionalized with bioactive rhBMP-2. This approach comprises two steps: 1) the initial formation of a self-assembling monolayer (SAM) of a bifunctional linker on the gold surface; 2) covalent immobilization of the rhBMP-2 protein. In previous work, we validated the effective binding of the bifunctional linker and the growth factor, and demonstrated that surface-immobilized rhBMP-2 maintains its biological activity19. The bioactivity of growth factors p...

Bone morphogenetic protein 2 (BMP-2) is a member of the transforming growth factor (TGF-&#946;) family and acts as inducer of de novo bone formation as well as regulator of several tissues during embryonic development and adult homeostasis1-3. Each monomer of the biologically active homodimeric BMP-2 protein contains a &#34;cysteine knot&#34; motif, which is highly conserved in all BMPs4. Six of the seven cysteine residues form intramolecular disulfide bonds that stabilize each monomer, whereas the seventh cysteine is involved in dimerization, forming an intermolecular bond between the two monomers5,6. This highly conserved cysteine knot defines the three-dimensional structure of the BMP-2 protein and determines its unique properties, such as resistance against heat, denaturants and acidic pH7-9. BMP-2 binds to serine/threonine kinase transmembrane receptors, thereby inducing signal transduction10-12. Depending on the mode of receptor oligomerization, different signaling pathways are activated: a Smad-independent signaling cascade leads to alkaline phosphatase induction via p38 signaling, whereas a Smad-dependent pathway activated by receptor phosphorylation results in Smad complex nuclear translocation and activation of transcription of specific target genes, such as the inhibitor of differentiation (Id)12-14.
In bone, BMP-2 induces the differentiation of mesenchymal stem cells into osteoblasts, thus stimulating the healing and de novo formation of bone. Currently, recombinantly expressed BMP-2 is applied clinically to enhance the healing of fractured sites. A common strategy in bone tissue engineering is the use of injectable growth factors, which is less invasive compared to local delivery systems. However, in vivo studies and clinical applications have shown that the short biological half-life, unspecific localization and rapid local clearance of BMP-2 may lead to several local, ectopic and systemic problems15. Hence, to obtain an effective presentation, the entrapment or immobilization of BMP-2 within or onto materials is necessary for its local and sustained delivery at the target site. Sustained delivery can be achieved with non-covalent retention approaches, such as physical entrapment, adsorption or ion complexation16. However, it is known that unspecific adsorption of proteins to surfaces may results in denaturation of the molecules17. For the covalent binding of growth factors, different types of supports have been developed over the last decade. The use of bifunctional linking molecules that target amino or carboxyl groups of the protein for example, is one type of approach that does not necessarily require protein modification to achieve its immobilization. In fact, while protein modification offers the advantage of controlling protein orientation, the introduction of artificial domains, peptide tags and site-specific chains may alter the biological activity of growth factors17. Thus, to circumvent denaturation due to interaction with the supporting material, surfaces can be functionalized beforehand, for example, with a self-assembled monolayer (SAM) of a linking molecule, followed by coupling of the desired factor18. We have used a SAM-based approach to covalently immobilize BMP-2 onto a surface by targeting its free amine residues and have shown that the immobilized protein retains both its short- and long-term biological activity19. This protocol provides a simple and efficient way to deliver BMP-2 to cells for in vitro studies on the mechanisms which occur at the cell membrane and regulate intracellular signaling responsible for osteogenic signaling.

<table border="1">
	<tbody>
		<tr>
			<td>Name of Material/ Equipment</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments/Description</td>
		</tr>
		<tr>
			<td>N-hydroxysuccinimide</td>
			<td>Sigma-Aldrich</td>
			<td>130672</td>
			<td></td>
		</tr>
		<tr>
			<td>4-(dimethylamino)pyridin</td>
			<td>Sigma-Aldrich</td>
			<td>522805</td>
			<td></td>
		</tr>
		<tr>
			<td>Acetone</td>
			<td>AppliChem</td>
			<td>A2282</td>
			<td></td>
		</tr>
		<tr>
			<td>11-mercaptoundecanoic acid</td>
			<td>Sigma-Aldrich</td>
			<td>674427</td>
			<td></td>
		</tr>
		<tr>
			<td>Dichlormethane</td>
			<td>Merck</td>
			<td>106050</td>
			<td></td>
		</tr>
		<tr>
			<td>N,N&#39;-dicyclohexylcarbodiimide</td>
			<td>Sigma-Aldrich</td>
			<td>D80002</td>
			<td></td>
		</tr>
		<tr>
			<td>Petroleum benzene</td>
			<td>Merck</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Glass coverslips</td>
			<td>Carl Roth</td>
			<td>M 875</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethylacetate</td>
			<td>AppliChem</td>
			<td>A3550</td>
			<td></td>
		</tr>
		<tr>
			<td>Methanol</td>
			<td>Carl Roth</td>
			<td>4627</td>
			<td></td>
		</tr>
		<tr>
			<td>N,N-dimethylformamide</td>
			<td>Carl Roth</td>
			<td>T921</td>
			<td></td>
		</tr>
		<tr>
			<td>rhBMP-2</td>
			<td>R&#38;D Systems</td>
			<td>355-BM</td>
			<td>Carrier-free; expressed in E.coli</td>
		</tr>
		<tr>
			<td>PBS</td>
			<td>PAA</td>
			<td>H15-002</td>
			<td></td>
		</tr>
		<tr>
			<td>NaCl</td>
			<td>Carl Roth</td>
			<td>HN00.2</td>
			<td></td>
		</tr>
		<tr>
			<td>Poly(dimethyl siloxane) (PDMS)</td>
			<td>Dow Corning</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Sylgard 184 silicone elastomer kit</td>
			<td>Dow Corning</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Anti-rhBMP-2</td>
			<td>Sigma</td>
			<td>B9553</td>
			<td></td>
		</tr>
		<tr>
			<td>Goat anti-mouse IgG-HRP</td>
			<td>Santa Cruz</td>
			<td>sc-2005</td>
			<td>Secondary antibody</td>
		</tr>
		<tr>
			<td>Ampliflu Red assay</td>
			<td>Sigma</td>
			<td>90101</td>
			<td></td>
		</tr>
		<tr>
			<td>Dulbecco&#39;s Modified Eagle Medium (DMEM) (1x), liquid</td>
			<td>Gibco</td>
			<td>41966</td>
			<td>High glucose</td>
		</tr>
		<tr>
			<td>Fetal Bovine Serum (FBS)</td>
			<td>Sigma</td>
			<td>F7524</td>
			<td>Sterile filtered, cell culture tested</td>
		</tr>
		<tr>
			<td>Pen/Strep</td>
			<td>Gibco</td>
			<td>15140</td>
			<td></td>
		</tr>
		<tr>
			<td>Trypsin 0.05% (1x) with EDTA 4Na</td>
			<td>Gibco</td>
			<td>25300</td>
			<td></td>
		</tr>
		<tr>
			<td>Glycine (0.1 M)</td>
			<td>Riedel-de Ha&#235;n</td>
			<td>33226</td>
			<td></td>
		</tr>
		<tr>
			<td>IGEPAL CA-630 (1%)</td>
			<td>Sigma</td>
			<td>I8896</td>
			<td>Lysis buffer (ALP assay)19</td>
		</tr>
		<tr>
			<td>Magnesium chloride (MgCl2)(1 mM)</td>
			<td>Carl Roth</td>
			<td>HNO3.2</td>
			<td></td>
		</tr>
		<tr>
			<td>Zinc chloride (ZnCl2) (1 mM)</td>
			<td>Carl Roth</td>
			<td>3533.1</td>
			<td></td>
		</tr>
		<tr>
			<td>p-nitrophenylphosphate (pNPP)</td>
			<td>Sigma</td>
			<td>S0942</td>
			<td>Phosphatase substrate</td>
		</tr>
		<tr>
			<td>Anti-mysin heavy chain (MHC)</td>
			<td>Developmental Studies Hybridoma Bank, University of Iowa</td>
			<td>MF20</td>
			<td>Monoclonal antibody</td>
		</tr>
		<tr>
			<td>Alexa Fluor 488 Goat anti-mouse IgG</td>
			<td>Invitrogen</td>
			<td>A11001</td>
			<td></td>
		</tr>
		<tr>
			<td>DAPI</td>
			<td>Sigma</td>
			<td>D9542</td>
			<td></td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td>Equipment</td>
		</tr>
		<tr>
			<td>Ultrsonic bath (Sonorex Super RK 102H), Frequency 35 kHz</td>
			<td>BANDELIN electronic GmbH &#38; Co. KG</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>MED 020 Sputtercoating system</td>
			<td>BAL-TEC AG</td>
			<td></td>
			<td>Coating conditions 
			Cr: 120 mA, 1.3 x 10-2 mbar, 30 sec 
			Au: 60 mA, 5.0 x 10-2 mbar, 45 sec</td>
		</tr>
		<tr>
			<td>Tecan Infinite M200 Plate reader</td>
			<td>Tecan</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

covalent binding of bmp-2 on surfaces using a self-assembled monolayer approach

Bone morphogenetic protein 2 (BMP-2) is a growth factor embedded in the extracellular matrix of bone tissue. BMP-2 acts as trigger of mesenchymal cell differentiation into osteoblasts, thus stimulating healing and de novo bone formation. The clinical use of recombinant human BMP-2 (rhBMP-2) in conjunction with scaffolds has raised recent controversies, based on the mode of presentation and the amount to be delivered. The protocol presented here provides a simple and efficient way to deliver BMP-2 for in vitro studies on cells. We describe how to form a self-assembled monolayer consisting of a heterobifunctional linker, and show the subsequent binding step to obtain covalent immobilization of rhBMP-2. With this approach it is possible to achieve a sustained presentation of BMP-2 while maintaining the biological activity of the protein. In fact, the surface immobilization of BMP-2 allows targeted investigations by preventing unspecific adsorption, while reducing the amount of growth factor and, most notably, hindering uncontrolled release from the surface. Both short- and long-term signaling events triggered by BMP-2 are taking place when cells are exposed to surfaces presenting covalently immobilized rhBMP-2, making this approach suitable for in vitro studies on cell responses to BMP-2 stimulation.

In our setup, gold was chosen as excipient since it provides a biologically unspecific but chemically tunable system. Furthermore, the application of self-assembling monolayers entails many benefits: SAMs spontaneously adsorb via their "head-groups" on metals and form monolayers with few defects, while their functional end-groups can be further modified. Thus they provide a platform to tailor the properties of the interface in a controlled yet highly adaptable way20.
For the immobil...

Watch this Scientific Journal Video about Covalent Binding of BMP-2 on Surfaces Using a Self-assembled Monolayer Approach at JoVE.com

Covalent Binding of BMP-2 on Surfaces Using a Self-assembled Monolayer Approach

We describe a method for accomplishing efficient immobilization of BMP-2 on surfaces. Our approach is based on the formation of a self-assembled monolayer to achieve the covalent binding of BMP-2 via its free amine residues. This method is a useful tool to study signaling at the cell membrane.

Bone morphogenetic protein 2 (BMP-2) is a growth factor embedded in the extracellular matrix of bone tissue. BMP-2 acts as trigger of mesenchymal cell ...

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JoVE Journal

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Organic Chemistry

Chemistry

Unit 1

Covalent Bonding and Structure

SCIENTISTS IN ACTION

13.8K visualizações.  University of Heidelberg.  Descreve-se um método para realizar a imobilização eficiente de BMP-2 em superfícies. A nossa abordagem é baseada na formação de uma monocamada auto-montada para alcançar a ligação da BMP-2 por meio dos seus resíduos de amina livres covalente. Este método é uma ferramenta útil para o estudo de sinalização na membrana celular. 