The authors acknowledge Oriol Font-Bach and Albert G. Casta&#241;o for their help in dmin quantification. They also acknowledge the Advanced Digital Microscopy Unit at the Institute for Research in Biomedicine (IRB Barcelona) to let the authors record the video in their premises. This work was supported by the Networking Biomedical Research Center (CIBER), Spain. CIBER is an initiative funded by the VI National R&amp;D&amp;i Plan 2008-2011, Iniciativa Ingenio 2010, Consolider Program, CIBER Actions, and the Instituto de Salud Carlos III, with the support of the European Regional Development Fund. This work has been supported by the Commission for Universities and Research of the Department of Innovation, Universities, and Enterprise of the Generalitat de Catalunya (2014 SGR 1442). It was also funded by the projects OLIGOCODES (No. MAT2012-38573-C02) and CTQ2013-41339-P, awarded by the Spanish Ministry of Economy and Competitiveness, in addition to INTERREG V-A Spain-Portugal 2014-2020 POCTEP (0245_IBEROS_1_E). C.R.P. acknowledges financial support from the Spanish Ministry of Economy and Competitiveness grant (No. IFI15/00151).

1. Substrate Preparation
<ol>
	<li>Annealing 1.4 x 1.1 cm Au(111) on Mica Substrates.
	<ol>
		<li>Place the Au(111) substrate on a glass-ceramic hob and anneal it with a butane flame for 3 min. Allow the substrate to cool under an argon atmosphere. Repeat this step for each Au(111) substrate. 
		NOTE: Au(111) substrates should be used immediately after annealing.</li>
	</ol>
	</li>
	<li>Preparation of Poly(L-Lactic Acid) (PLLA)-Coated Glass Substrates.
	<ol>
		<li>Cut and wash the...

<ol>
	<li>Jiang, F., H&#246;rber, H., Howard, J., M&#252;ller, D. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Assembly+of+collagen+into+microribbons:+Effects+of+pH+and+electrolytes.">Assembly of collagen into microribbons: Effects of pH and electrolytes.</a> J. Struct. Biol. 148 (3), 268-278 (2004).</li><li>Smith, M. 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=Force-induced+unfolding+of+fibronectin+in+the+extracellular+matrix+of+living+cells.">Force-induced unfolding of fibronectin in the extracellular matrix of living cells.</a> PLoS Biol. 5 (10), 2243-2254 (2007).</li><li>Little, W. C., Smith, M. L., Ebneter, U., Vogel, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Assay+to+mechanically+tune+and+optically+probe+fibrillar+fibronectin+conformations+from+fully+relaxed+to+breakage.">Assay to mechanically tune and optically probe fibrillar fibronectin conformations from fully relaxed to breakage.</a> Matrix Biol. 27 (5), 451-461 (2008).</li><li>Christman, K. L., Enriquez-Rios, V. D., Maynard, H. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nanopatterning+proteins+and+peptides.">Nanopatterning proteins and peptides.</a> Soft Matter. 2, 928-939 (2006).</li><li>Falconnet, D., Csucs, G., Grandin, H. M., Textor, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Surface+engineering+approaches+to+micropattern+surfaces+for+cell-based+assays.">Surface engineering approaches to micropattern surfaces for cell-based assays.</a> Biomaterials. 27 (16), 3044-3063 (2006).</li><li>Arnold, 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=Activation+of+integrin+function+by+nanopatterned+adhesive+interfaces.">Activation of integrin function by nanopatterned adhesive interfaces.</a> ChemPhysChem. 5 (3), 383-388 (2004).</li><li>Cavalcanti-Adam, E. 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=Lateral+spacing+of+integrin+ligands+influences+cell+spreading+and+focal+adhesion+assembly.">Lateral spacing of integrin ligands influences cell spreading and focal adhesion assembly.</a> Eur. J. Cell. Biol. 85 (3-4), 219-224 (2006).</li><li>Cavalcanti-Adam, E. 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=Cell+spreading+and+focal+adhesion+dynamics+are+regulated+by+spacing+of+integrin+ligands.">Cell spreading and focal adhesion dynamics are regulated by spacing of integrin ligands.</a> Biophys. J. 92 (8), 2964-2974 (2007).</li><li>Arnold, 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=Cell+interactions+with+hierarchically+structured+nano-patterned+adhesive+surfaces.">Cell interactions with hierarchically structured nano-patterned adhesive surfaces.</a> Soft Matter. 5 (1), 72-77 (2009).</li><li>Malmstr&#246;m, J., 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=Large+area+protein+patterning+reveals+nanoscale+control+of+focal+adhesion+development.">Large area protein patterning reveals nanoscale control of focal adhesion development.</a> Nano Lett. 10 (2), 686-694 (2010).</li><li>Deeg, J. 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=Impact+of+local+versus+global+ligand+density+on+cellular+adhesion.">Impact of local versus global ligand density on cellular adhesion.</a> Nano Lett. 11 (4), 1469-1476 (2011).</li><li>Medda, R., 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+early+cell&#8211;surface+interactions+of+human+mesenchymal+stem+cells+on+nanopatterned+&#946;-type+titanium-niobium+alloy+surfaces.">Investigation of early cell&#8211;surface interactions of human mesenchymal stem cells on nanopatterned &#946;-type titanium-niobium alloy surfaces.</a> Interface Focus. 4, 20130046 (2014).</li><li>Wang, X., 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=Effect+of+RGD+nanospacing+on+differentiation+of+stem+cells.">Effect of RGD nanospacing on differentiation of stem cells.</a> Biomaterials. 34 (12), 2865-2874 (2013).</li><li>Wang, X., Ye, K., Li, Z. H., Yan, C., Ding, J. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Adhesion,+proliferation,+and+differentiation+of+mesenchymal+stem+cells+on+RGD+nanopatterns+of+varied+nanospacings.">Adhesion, proliferation, and differentiation of mesenchymal stem cells on RGD nanopatterns of varied nanospacings.</a> Organogenesis. 9 (4), 280-286 (2013).</li><li>Wang, X., Li, S. Y., Yan, C., Liu, P., Ding, J. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fabrication+of+RGD+micro/nanopattern+and+corresponding+study+of+stem+cell+differentiation.">Fabrication of RGD micro/nanopattern and corresponding study of stem cell differentiation.</a> Nano Lett. 15 (3), 1457-1467 (2015).</li><li>Li, Z. 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=Effects+of+RGD+nanospacing+on+chondrogenic+differentiation+of+mesenchymal+stem+cells.">Effects of RGD nanospacing on chondrogenic differentiation of mesenchymal stem cells.</a> J. Mater. Chem. B. 3 (12), 5197-5209 (2015).</li><li>Stephanopoulos, N., 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=Bioactive+DNA-peptide+nanotubes+enhance+the+differentiation+of+neural+stem+cells+into+neurons.">Bioactive DNA-peptide nanotubes enhance the differentiation of neural stem cells into neurons.</a> Nano Lett. 15 (1), 603-609 (2015).</li><li>Rolland, O., Turrin, C. O., Caminade, A. M., Majoral, J. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dendrimers+and+nanomedicine:+Multivalency+in+action.">Dendrimers and nanomedicine: Multivalency in action.</a> New J. Chem. 33, 1809-1824 (2009).</li><li>Saovapakhiran, A., D&#8217;Emanuele, A., Attwood, D., Penny, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Surface+modification+of+PAMAM+dendrimers+modulates+the+mechanism+of+cellular+internalization.">Surface modification of PAMAM dendrimers modulates the mechanism of cellular internalization.</a> Bioconjug. Chem. 20 (4), 693-701 (2009).</li><li>Albertazzi, L., Fernandez-Villamarin, M., Riguera, R., Fernandez-Megia, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Peripheral+functionalization+of+dendrimers+regulates+internalization+and+intracellular+trafficking+in+living+cells.">Peripheral functionalization of dendrimers regulates internalization and intracellular trafficking in living cells.</a> Bioconjug. Chem. 23 (5), 1059-1068 (2012).</li><li>Mikhail, A. S., Jones, K. S., Sheardown, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dendrimer+grafted+cell+adhesion+peptide-modified+PDMS.">Dendrimer grafted cell adhesion peptide-modified PDMS.</a> Biotechnol. Prog. 24 (4), 938-944 (2008).</li><li>Kino-oka, M., Kim, J., Kurisaka, K., Kim, M. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preferential+growth+of+skeletal+myoblasts+and+fibroblasts+in+co-culture+on+a+dendrimer-immobilized+surface.">Preferential growth of skeletal myoblasts and fibroblasts in co-culture on a dendrimer-immobilized surface.</a> J. Biosci. Bioeng. 115 (1), 96 (2013).</li><li>Kim, M. 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=Morphological+regulation+and+aggregate+formation+of+rabbit+chondrocytes+on+dendrimer+immobilized+surfaces+with+D-glucose+display.">Morphological regulation and aggregate formation of rabbit chondrocytes on dendrimer immobilized surfaces with D-glucose display.</a> J. Biosci. 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The authors have nothing to disclose.

During the development of the described protocol, a number of critical steps should be considered. The first refers to nanopattern characterization with scanning probe microscopy techniques. To visualize the nanopatterns, the surface where patterning is produced must have a roughness value below the mean diameter of the dendrimers, which is around 4&#8211;5 nm as measured by STM (Figure 1B). Also, it should be taken into account that high resolution STM imaging is restricted to conductive substrates, in ...

Here we describe a simple and versatile dendrimer-based nanopatterning procedure to obtain cell culture surfaces that allow the control of local adhesiveness at the nanoscale. Nanoscale details of ECM organization have been reported,1,2,3 and the nanopatterning of cell adhesion surfaces has provided deep insights into the cellular requirements related to adhesion4,5. Experiments using micellar lithography-based nanopatterns revealed a threshold value of around 70 nm for RGD peptide nanospacing, cell adhesion being significantly delayed above this value6,7,8,9. These studies also highlighted the greater influence of local than global ligand density on cell adhesion9,10,11.
During morphogenesis, cell interactions with the surrounding environment trigger the first differentiation events, which continue until final complex tissue structures have been formed. Within this framework, nanopatterned surfaces have been used to tackle the influence of the initial cell-surface interactions on morphogenesis. Lithography-based RGD nanopatterns with a lateral spacing of 68 nm in &#946;-type Ti-40Nb alloys help to maintain the undifferentiated phenotype of non-committed stem cells12, while RGD nanospacings of between 95 and 150 nm enhance the differentiation of mesenchymal stem cells (MSCs) towards adipogenic/osteogenic13,14,15 and chondrogenic fates16. Also, self-assembling macromolecules modified with signaling components have been shown to direct cell adhesion and differentiation by providing nanoscale architectural regulation of the signaling cues17. In this regard, the deposition of dendrimers with cell-interacting moieties in their outer sphere18,19,20 onto surfaces has been used to study cell adhesion21,22, morphology23,24, and migration events25,26. Nevertheless, the lack of surface characterization in these studies makes it difficult to establish any correlation between dendrimer surface configuration and cell response.
Dendrimer nanopatterns with liquid-like order and defined spacing can be obtained when dendrimers adsorb to low-charged surfaces from solutions with low ionic strengths.27 On the basis of this property, here we present a method to obtain large-scale uneven nanopatterns of RGD-functionalized dendrimers on low-charged surfaces that permit the nanoscale control of local RGD surface density. Water contact angle (CA), X-ray photoelectron spectroscopy (XPS) and scanning probe microscopy techniques (STM and AFM nanopatterns) show that local ligand densities can be adjusted modifying the initial dendrimer concentration in solution. The local RGD surface density is quantified from AFM images by probability contour maps of minimum interparticle distances and then correlated with cell experiments. Compared with other nanopatterning techniques4, dendrimer-based nanopatterning is straightforward and can be easily scaled up to large surface areas, thus being fully compatible with cell culture applications. Nanopatterns are used as bioactive substrates to evaluate the effect of the local RGD surface density on cell adhesion28 and on the chondrogenic induction of adult human MSCs29. Our results show that RGD dendrimer-based nanopatterns sustain cell growth and that cell adhesion is reinforced by high local RGD surface densities. In the differentiation experiments, intermediate adhesiveness of cells to the substrates favored MSC condensation and early chondrogenic differentiation. Due to the ease with which dendrimer peripheral groups can be modified, the method described here can be further extended to other ECM ligands that exert concentration-dependent effects on cells.

<table border="0" cellpadding="0" cellspacing="0" width="1384">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:504px;">Gold (111) on mica. 1.4x1.1 cm&#160;</td>
			<td style="width:169px;">Spi Supplies</td>
			<td style="width:307px;">466PS-AB</td>
			<td style="width:405px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:504px;">Glass micro slides, plain</td>
			<td style="width:169px;">Corning</td>
			<td style="width:307px;">2947-75x25</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:504px;">Deionized water</td>
			<td style="width:169px;">Millipore</td>
			<td style="width:307px;"></td>
			<td>18M&#937; cm</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:504px;">Ethanol 96%</td>
			<td style="width:169px;">PanReac</td>
			<td style="width:307px;">131085.1212</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:504px;">L-Lactide/DL-Lactide copolymer</td>
			<td style="width:169px;">Corbion</td>
			<td style="width:307px;"></td>
			<td>95/05 molar ratio</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:504px;">1,4 - dioxane</td>
			<td style="width:169px;">Sigma-Aldrich</td>
			<td style="width:307px;">296309-1L</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:504px;">Silicone oil, high temperature</td>
			<td style="width:169px;">Acros Organics</td>
			<td style="width:307px;">174665000</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:504px;">Spinner</td>
			<td style="width:169px;">Laurell</td>
			<td style="width:307px;">WS-650MZ-23NPP/Lite</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:504px;">Tissue culture laminar flow hood</td>
			<td style="width:169px;">Telstar</td>
			<td style="width:307px;">Bio II Advance</td>
			<td>Class II biological safety cabinet</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:504px;">Filter unit</td>
			<td style="width:169px;">Millex-GP</td>
			<td style="width:307px;">SLGP033RB</td>
			<td>0.22 &#181;m</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:504px;">Syringe 10 mL</td>
			<td style="width:169px;">Discardit</td>
			<td style="width:307px;">309110</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:504px;">Atomic Force microscope</td>
			<td style="width:169px;">Veeco Instruments</td>
			<td style="width:307px;">Dimension 3000 AFM instrument</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:504px;">Silicon AFM probes</td>
			<td style="width:169px;">Budget Sensors</td>
			<td style="width:307px;">Tap300AI-G</td>
			<td>Resonant Freq. 300 kHz, k = 40 N/m</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:504px;">Scanning tunneling microscope</td>
			<td style="width:169px;">Molecular Imaging</td>
			<td style="width:307px;">PicoSPM microscope</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:504px;">Pt0.8:Ir0.2 wire</td>
			<td style="width:169px;">Advent</td>
			<td style="width:307px;">PT671012</td>
			<td>Diameter 0.25 mm</td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:504px;">WSxM 4.0 software</td>
			<td style="width:169px;">Nanotec electronica</td>
			<td style="width:307px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:504px;">Optical contact angle (CA) system</td>
			<td style="width:169px;">Dataphysics</td>
			<td style="width:307px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:504px;">SCA20 software</td>
			<td style="width:169px;">Dataphysics</td>
			<td style="width:307px;"></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:504px;">X-ray photoelectron spectrometer</td>
			<td style="width:169px;">Physical Electronics</td>
			<td style="width:307px;">Perkin-Elmer PHI 5500 Multitechnique System</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:504px;">Fibronectin from bovine plasma</td>
			<td style="width:169px;">Sigma-Aldrich</td>
			<td style="width:307px;">F1141-1MG</td>
			<td>1.0 mL solution</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:504px;">Dulbecco&#39;s Phosphate Buffer Saline (DPBS)</td>
			<td style="width:169px;">Gibco</td>
			<td style="width:307px;">21600-10</td>
			<td>Powder</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:504px;">Mouse embryo fibroblasts</td>
			<td style="width:169px;">ATCC</td>
			<td style="width:307px;">ATCC CRL-1658</td>
			<td>NIH/3T3</td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:504px;">Dulbecco&#39;s modified eagle medium (DMEM) liquid high glucose</td>
			<td style="width:169px;">Gibco</td>
			<td style="width:307px;">11960044</td>
			<td>liquid high glucose, no glutamine, 500 mL</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:504px;">Fetal Bovine Serum (FBS)</td>
			<td style="width:169px;">Gibco</td>
			<td style="width:307px;">16000044</td>
			<td>500 mL</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:504px;">L-Glutamine</td>
			<td style="width:169px;">Invitrogen</td>
			<td style="width:307px;">25030</td>
			<td>200 mM (100X)</td>
		</tr>
		<tr height="23">
			<td height="23" style="height:23px;width:504px;">Penicillin-streptomycin</td>
			<td style="width:169px;">Invitrogen</td>
			<td style="width:307px;">15140</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:504px;">Sodium pyruvate</td>
			<td style="width:169px;">Invitrogen</td>
			<td style="width:307px;">11360039</td>
			<td>100 mL</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:504px;">T75 culture flasks</td>
			<td style="width:169px;">Nunclon</td>
			<td style="width:307px;">156499</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:504px;">Trypsin</td>
			<td style="width:169px;">Life Technologies</td>
			<td style="width:307px;">25200072</td>
			<td>0,25% EDTA</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:504px;">Centrifuge</td>
			<td style="width:169px;">Hermle Labortechnik</td>
			<td style="width:307px;">Z 206 A</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:504px;">Non-tissue culture treated plate, 12 well</td>
			<td style="width:169px;">Falcon</td>
			<td style="width:307px;">351143</td>
			<td>Non-adherent</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:504px;">Adipose-derived hMSCs</td>
			<td style="width:169px;">ATCC</td>
			<td style="width:307px;">ATCC PCS-500-011</td>
			<td>Cell vial 1 mL</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:504px;">MSC basal medium</td>
			<td style="width:169px;">ATCC</td>
			<td style="width:307px;">ATCC PCS-500-030</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:504px;">MSC growth kit</td>
			<td style="width:169px;">ATCC</td>
			<td style="width:307px;">ATCC PCS-500-040</td>
			<td>Low serum</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:504px;">Chondrocyte differentiation tool</td>
			<td style="width:169px;">ATCC</td>
			<td style="width:307px;">ATCC PCS-500-051</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:504px;">Formalin solution</td>
			<td style="width:169px;">Sigma-Aldrich</td>
			<td style="width:307px;">HT5011-15ML</td>
			<td>neutral buffered, 10%</td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:504px;">Ammonium chloride</td>
			<td style="width:169px;">Sigma-Aldrich</td>
			<td style="width:307px;">A9434-500G</td>
			<td>for molecular biology, suitable for cell culture, &#8805;99.5%</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:504px;">Saponin</td>
			<td style="width:169px;">Sigma-Aldrich</td>
			<td style="width:307px;">47036-50G-F</td>
			<td>for molecular biology, used as non-ionic surfactant, adjuvant</td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:504px;">Bovine Serum Albumin (BSA)</td>
			<td style="width:169px;">Sigma-Aldrich</td>
			<td style="width:307px;">A3059-50G</td>
			<td></td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:504px;">Rabbit monoclonal [Y113] anti-paxillin antibody</td>
			<td style="width:169px;">Abcam</td>
			<td style="width:307px;">ab32084</td>
			<td>Diluted 1:200</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:504px;">Mouse monoclonal [1F5] anti-collagen alpha-1 XX chain&#160;</td>
			<td style="width:169px;">Acris Antibodies</td>
			<td style="width:307px;">AM00212PU-N</td>
			<td>Diluted: 1:400</td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:504px;">Alexa Fluor 488-conjugated goat anti-mouse IgG (H+L) secondary antibody</td>
			<td style="width:169px;">Invitrogen</td>
			<td style="width:307px;">A10667</td>
			<td>2 mg/mL. Diluted 1:1000</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:504px;">Alexa Fluor 568-conjugated goat anti-rabbit IgG (H+L) secondary antibody</td>
			<td style="width:169px;">Invitrogen</td>
			<td style="width:307px;">A11036</td>
			<td>2 mg/mL. Diluted 1:1000</td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:504px;">Hoechst 33342</td>
			<td style="width:169px;">Thermo Fisher</td>
			<td style="width:307px;">H3570 10ML</td>
			<td>10 mg/mL. Diluted 1:1000</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:504px;">Cover glass 24x24 mm</td>
			<td style="width:169px;">Deltalab</td>
			<td style="width:307px;">D102424</td>
			<td></td>
		</tr>
		<tr height="23">
			<td height="23" style="height:23px;width:504px;">Fluoromount</td>
			<td style="width:169px;">Sigma-Aldrich</td>
			<td style="width:307px;">F4680-25ML</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:504px;">Epifluorescence Microscope</td>
			<td style="width:169px;">Nikon</td>
			<td style="width:307px;">Eclipse E1000 upright microscope</td>
			<td>with a CCD camera</td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:504px;">Confocal Microscope</td>
			<td style="width:169px;">Leica Microsystems</td>
			<td style="width:307px;"></td>
			<td>Leica SPE Upright Confocal Microscope</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:504px;">ImageJ 1.50g freeware</td>
			<td style="width:169px;">http://imgej.nih.gov/ij</td>
			<td style="width:307px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:504px;">MATLAB software</td>
			<td style="width:169px;">The MATHWORKS, Inc.</td>
			<td style="width:307px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:504px;">OriginPro 8.5 software&#160;</td>
			<td style="width:169px;">OriginLab Coorporation</td>
			<td style="width:307px;"></td>
			<td></td>
		</tr>
	</tbody>
</table>

dendrimer-based uneven nanopatterns to locally control surface adhesiveness: a method to direct chondrogenic differentiation

Cellular adhesion and differentiation is conditioned by the nanoscale disposition of the extracellular matrix (ECM) components, with local concentrations having a major effect. Here we present a method to obtain large-scale uneven nanopatterns of arginine-glycine-aspartic acid (RGD)-functionalized dendrimers that permit the nanoscale control of local RGD surface density. Nanopatterns are formed by surface adsorption of dendrimers from solutions at different initial concentrations and are characterized by water contact angle (CA), X-ray photoelectron spectroscopy (XPS), and scanning probe microscopy techniques such as scanning tunneling microscopy (STM) and atomic force microscopy (AFM). The local surface density of RGD is measured using AFM images by means of probability contour maps of minimum interparticle distances and then correlated with cell adhesion response and differentiation. The nanopatterning method presented here is a simple procedure that can be scaled up in a straightforward manner to large surface areas. It is thus fully compatible with cell culture protocols and can be applied to other ligands that exert concentration-dependent effects on cells.

We present a nanopatterning method that allows surface adhesiveness to be addressed at the nanoscale (Figure 1). The chemical structure of RGD-Cys-D1 is shown in Figure 1A. Dendrimers were patterned on electrical conductive Au(111) surfaces for high resolution STM characterization. Low dendrimer concentrations in solution (up to 10-5% w/w) rendered isolated dendrimers of 4-5 nm in diameter (<strong class="xfig...

Watch this Scientific Journal Video about Dendrimer-based Uneven Nanopatterns to Locally Control Surface Adhesiveness: A Method to Direct Chondrogenic Differentiation at JoVE.com

Dendrimer-based Uneven Nanopatterns to Locally Control Surface Adhesiveness: A Method to Direct Chondrogenic Differentiation

A method to obtain dendrimer-based uneven nanopatterns that permit the nanoscale control of local arginine-glycine-aspartic acid (RGD) surface density is described and applied for the study of cell adhesion and chondrogenic differentiation.

Cellular adhesion and differentiation is conditioned by the nanoscale disposition of the extracellular matrix (ECM) components, with local concentrations ...

The overall goal of this protocol is to obtain large scale dendrimer based uneven nanopatterns that permit the nanoscale control of local surface adhesiveness. The method described is applied for the study of cell adhesion and chondrogenic differentiation. Dendrimer raised nanopatterns allow to locally control surface adhesiveness at the nanoscale.First generation polynanomers modified with the cell adhesive RGD peptide are used to create nanopatterns. They are characterized by a scanning per microscopy techniques and used in cell adhesion and differentiation studies. We then analyze the results from microscopy and immunostaining techniques.The first step is to prepare the working substrates. Customized square glass slides are produced by cutting microscopy slides with a diamond tipped cutter. Make slides of 1.25 by 1.25 centimeters in size.Wash the slides with deionized water, followed by 96%ethanol and let them air dry. Prepare the 2%PLLA solution by adding 200 milligrams of PLLA to a pressure tube and add 10 milliliters of dioxane. Add a stir bar and close the tube tightly.Warm the mixture in a glycerine bath at 60 degrees centigrade for 24 hours under gentle stirring. Place the glass slides in a glass vial containing the PLLA solution on a clean, hot plate at 60 degrees centigrade. Wait at least 10 minutes to reach the necessary temperature.Spin coat the glass substrates with the PLLA solution by placing the glass slide on the spin coater stage and running the selected program. We select 3, 000 rpm for 30 seconds with an acceleration of 1, 500 rpms per second with a pre-step of 500 rpm at five seconds at 300 rpms per second to ensure an homogenous coating. Spin coated glasses can be stored in the fridge.Prepare and sonicate for 10 minutes solution A, a 0.77 milligrams per milliliter solution of RGD-Cys-D1 dendrimer in deionized water. Then prepare dendrimer solutions of 10 to the 2%and 10 to the 5%solution B and C respectively in deionized water. Sonicate solution C for 10 minutes and prepare the following dendrimer solutions, D, E, and F also in deionized water.Solution D, 2.5x10 to the 8%solution E, 10 to the 8%and solution F, 4 10 to the 9%Preserve these solutions in the fridge until use. You graduate with a UV lamp of the cell culture cabin 18 PLLA coated glasses for 13 minutes to make them sterile. Sonicate each of the dendrimer solutions for 10 minutes.Filter the dendrimer solutions through 0.22 micrometer diameter filters on the PLLA coated glass slides in a 12 well plate under the cell culture cabin laminar flow. Leave them inside the cabin at room temperature for 16 hours and wash them with sterile, deionized water. For the positive control samples, prepare a sterile fibronectin solution in PBS and incubate the replicas with the solution for one hour at room temperature in the cell culture cabin.Wash them with PBS. The remaining three PLLA coated substrates will serve as the replicas for the negative control. Nanopattern topography is analyzed with AFM operated in tapping mode in air.Mount a silicon cantilever with a spring constant of 40 newtons per meter and a resonant frequency of 300 kilohertz into the AFM tip holder. With the nanopattern substrate on the AFM stage, approach the surface until contact and choose an amplitude set point that permits imaging the dendrimer configuration without exerting excessive pressure on the surface. Register at least three representative images of 5x5 micrometers per substrate of three independent substrates per condition.Treat the acquired images with the AFM processing software. Select dendrimers on the processed AFM height images and obtain the corresponding image thresholds. Get the particle precisions and use them to obtain the minimum inter-particle distances.Let the minimum inter-particle distances in Z to the corresponding particle precisions to obtain the probability control plugs for the minimum inter-particle distances. Adjust the color scale of the plot to visualize the regions where local RGD surface density is below 70 nanometers. Quantify the area of these regions by selecting them on the image and generating a threshold.Use commercial human adipose derived from mesenchymal stem cells from early passages, preferably below five. Culture them at 37 degrees and 4.6%CO2 atmosphere in the stem cell growth medium until 70 or 80%confluence is reached. Seed the cells at a cell density of 3, 000 cells per square centimeter on the substrates in a chondrogenesis inducing medium.Change the medium every three days. The condensation step can be observed from the first day in culture, and their evolution can be followed by an optical phase contrast microscope during all the culture labs. Fix the cells with 10%formalin solution at room temperature for 20 minutes, and then wash with PBS.Lock the furaldehyde groups by adding a 50 millimolar solution of ammonium chloride in PBS. Leave for 20 minutes at room temperature. Wash with PBS.Permeabilize the cells with 0.1%solution of saponin in the blocking solution of 1%albumin in PBS for 10 minutes at room temperature. Incubate with primary antibodies in the blocking solution for one hour at room temperature. Wash with PBS.Incubate with secondary antibodies in the blocking solution for on hour at room temperature, avoiding light exposure. Wash with PBS and dry. Apply microscopy mounting medium on the samples and cover them gently with cover slips.Image the immunostained samples for the focal adhesion protein paxillin after one day of chondrogenic induction, and for the early chondrogenic marker, collagen II alpha I after five days of chondrogenic induction using an upright confocal microscope. Collect sections at a representative interval, for example 0.5 or 1 micrometers. Filter the images stained for paxillin from the basal zone of cell condensates.Remove the background, smooth, and convert to eight bit files. Make them binary by setting an empirically selected threshold. Treat a minimum of three cell condensates per condition of three independent samples.Quantify the selected areas and express them as the corresponding percentage of area divided by the number of cell nuclei in the image. To quantify collagen II alpha I staining, create confocal Z projections. Filter the resulting images, remove background, smooth, and set a threshold.Quantify the sum of the projected area maximum collagen II alpha I area per sample against the area of the corresponding cell condensate. Different nanopattern configurations can be obtained modifying the initial dendrimer concentration in solution. Nanopatterns can be visualized by AFM analysis and probability contour plots for the minimum inter-particle distance constructed.They highlight the regions on the surface with the highest local RGD surface density. Dendrimer nanopatterns are used in cell adhesion studies. Adhesion increases with local RGD surface density.For the positive control and surfaces containing dendrimer aggregates, this correlation is lost. Influence of local RGD surface density was tested in chondrogenesis, both cell condensation and differentiation are favored by nanopatterns presenting an intermediate adhesiveness. In conclusion, dendrimer-based nanopattern in a three table method to address the affect of local RGD density on cell response.Nanopatterns sustain cell adhesion more efficiently at the corresponding homogenous surface commonly used in cell culture. In differentiation experiments, intermediate adhesiveness of cells to the substrate favored mesenchymal cell condensation and early chrondogenic differentiation. Due to the easy modification of dendrimer peripheral growth, the method here described can be further extended to all the excessive rheumatic layers having density effects on cells.

dendrimer-based-uneven-nanopatterns-to-locally-control-surface

Research

JoVE Journal

Bioengineering

7.8K visualizações.  Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute of Science and Technology (BIST). The overall goal of this protocol is to obtain large scale dendrimer based uneven nanopatterns that permit the nanoscale control of local surface adhesiveness. The method described is applied for the study of cell adhesion and chondrogenic differentiation. Dendrimer raised nanopatterns allow to locally control surface adhesiveness at the nanoscale.First generation polynanomers modified with the cell adhesive RGD peptide are used to create nanopatterns. They are characterized by a scann...