We acknowledge funding from NIH (NHLBI Contract No. HHSN268201000044C to R.W., S.H. and S.Y.S.).

1. Preparation of GST and Nanoparticle (NP) Conjugates
<ol>
	<li>GST-TCO preparation:
	<ol>
		<li>Add 8 &#956;l of TCO-NHS solution (50 mM in DMSO) to 100 &#956;l of GST (1 mg/ml in PBS) and shake mixture at RT for 1 hr.</li>
		<li>Remove excess reagent using a Zeba spin desalting column. The recovered filtrate containing the GST-TCO conjugate is stored at 4 &#176;C prior to use.</li>
	</ol>
	</li>
	<li>GST-Tz preparation:
	<ol>
		<li>Add 6 &#956;l of Tz-NHS solution (25 mM in DMF) to 75 &#956;l of GST (1 mg/ml in PBS)...

<ol>
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Y., Shtatland, T., Josephson, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cell-specific+targeting+of+nanoparticles+by+multivalent+attachment+of+small+molecules.">Cell-specific targeting of nanoparticles by multivalent attachment of small molecules.</a> Nat Biotechnol. 23, 1418-1423 (2005).</li><li>Yuan, J., Oliver, R., Aguilar, M. I., Wu, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Surface+plasmon+resonance+assay+for+chloramphenicol.">Surface plasmon resonance assay for chloramphenicol.</a> Anal Chem. 80, 8329-8333 (2008).</li><li>Myung, J. H., Gajjar, K. A., Saric, J., Eddington, D. T., Hong, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dendrimer-mediated+multivalent+binding+for+the+enhanced+capture+of+tumor+cells.">Dendrimer-mediated multivalent binding for the enhanced capture of tumor cells.</a> Angew Chem Int Ed Engl. 50, 11769-11772 (2011).</li><li>Keelan, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nanotoxicology:+nanoparticles+versus+the+placenta.">Nanotoxicology: nanoparticles versus the placenta.</a> Nat Nanotechnol. 6, 263-264 (2011).</li><li>Lundqvist, M., Stigler, J., Elia, G., Lynch, I., Cedervall, T., Dawson, K. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nanoparticle+size+and+surface+properties+determine+the+protein+corona+with+possible+implications+for+biological+impacts.">Nanoparticle size and surface properties determine the protein corona with possible implications for biological impacts.</a> Proc Natl Acad Sci U S A. 105, 14265-14270 (2008).</li><li>Lundqvist, 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=The+evolution+of+the+protein+corona+around+nanoparticles:+a+test+study.">The evolution of the protein corona around nanoparticles: a test study.</a> ACS Nano. 5, 7503-7509 (2011).</li><li>Mammen, M., Choi, S. -. K., Whitesides, G. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Polyvalent+interactions+in+biological+systems:+implications+for+design+and+use+of+multivalent+ligands+and+inhibitors.">Polyvalent interactions in biological systems: implications for design and use of multivalent ligands and inhibitors.</a> Angew Chem Int Ed Engl. 37, 2754-2899 (1998).</li><li>Kausaite-Minkstimiene, A., Ramanaviciene, A., Kirlyte, J., Ramanavicius, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparative+study+of+random+and+oriented+antibody+immobilization+techniques+on+the+binding+capacity+of+immunosensor.">Comparative study of random and oriented antibody immobilization techniques on the binding capacity of immunosensor.</a> Anal Chem. 82, 6401-6408 (2010).</li><li>Arkin, M. R., Wells, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Small-molecule+inhibitors+of+protein-protein+interactions:+progressing+towards+the+dream.">Small-molecule inhibitors of protein-protein interactions: progressing towards the dream.</a> Nat Rev Drug Discov. 3, 301-317 (2004).</li><li>Giannetti, A. M., Koch, B. D., Browner, M. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Surface+plasmon+resonance+based+assay+for+the+detection+and+characterization+of+promiscuous+inhibitors.">Surface plasmon resonance based assay for the detection and characterization of promiscuous inhibitors.</a> J Med Chem. 51, 574-580 (2008).</li><li>Kimple, A. J., Willard, F. S., Giguere, P. M., Johnston, C. A., Mocanu, V., Siderovski, D. 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The authors declare that they have no competing financial interests.

The capture-cycloaddition method described here enables rapid, reversible immobilization of modified nanoparticles and small molecules for label-free chip-based interaction and kinetic studies. The immobilization protocol can be performed in minutes requiring &#60;10 &#956;M concentrations of small-molecule ligands. By modulating ligand concentration and contact time immobilization densities can be closely controlled. Our data show that on-chip bioorthogonal reactions preserve the ability of in situ functionaliz...

Efficient conjugation reactions are valuable tools for attaching bioactive molecules to surfaces for a variety of biotechnology applications. Recently, the very fast bioorthogonal [4+2] cycloaddition reaction between trans-cyclooctene (TCO) and 1,2,4,5-tetrazine (Tz) has been used to label cell surfaces, subcellular structures, antibodies and nanoparticles.1-7 Here, we use the [4+2] cycloaddition reaction in combination with antigen/antibody capture (GST/anti-GST) for reversible on-chip synthesis of multi-component structures for Surface Plasmon Resonance (SPR) interaction analysis and monitor the process in real-time (Figure 1).8,9 Notably, the capture-cycloaddition strategy enables surface regeneration using an established protocol.8 As a consequence, assembly of stable sensor surfaces with control over ligand orientation and density for variety of new assay formats is now possible. Using this strategy we demonstrate the immobilization of TCO/Tz-derivatized small molecules and characterize the cycloaddition rates in a variety of buffer conditions. We chose the well-known interaction between FKBP12 and a molecule AP1497 that binds FKBP1210-12 as an example to verify that the capture-cycloaddition strategy preserves the ability of the small molecule to interact with its target when either directly attached to immobilized GST antigens or to immobilized nanoparticles (NPs).
This method offers several benefits. First, the reversible immobilization of small molecules on sensor chips is now possible. Second, TCO/Tz immobilization of small molecules also enables label-free interaction studies that reverse the orientation of canonical SPR studies, and may provide a complementary view of a binding interaction. Third, this method enables the microfluidic synthesis of targeted nanoparticles, and immediate evaluation of their binding properties. This promises to improve the efficiency of evaluating or screening targeted nanoparticles, and also decrease the amounts of nanoparticles required.13-15 Fourth, this approach can measure the reaction kinetics of bioorthogonal cycloaddition reactions in real-time under continuous flow. Finally, the TCO/Tz immobilization chemistry is robust in the presence of serum. Taken together, we anticipate that this versatile approach will broadly facilitate construction of stable sensor surfaces for a wide variety of microfluidic studies with relevance to in vitro and in vivo cellular applications.

<table border="1">
	<tbody>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td>Reagent</td>
		</tr>
		<tr>
			<td>Sensor Chip CM5</td>
			<td>GE Healthcare</td>
			<td>BR-1005-30</td>
			<td></td>
		</tr>
		<tr>
			<td>Amine coupling kit</td>
			<td>GE Healthcare</td>
			<td>BR-1000-50</td>
			<td></td>
		</tr>
		<tr>
			<td>GST capture kit</td>
			<td>GE Healthcare</td>
			<td>BR-1002-23</td>
			<td></td>
		</tr>
		<tr>
			<td>NAP-10 Columns</td>
			<td>GE Healthcare</td>
			<td>17-0854-01</td>
			<td></td>
		</tr>
		<tr>
			<td>GST, lyophilized in 1X PBS</td>
			<td>Genscript</td>
			<td>Z02039</td>
			<td>1 mg/ml</td>
		</tr>
		<tr>
			<td>rhFKBP12</td>
			<td>R&#38;D Systems</td>
			<td>3777-FK</td>
			<td></td>
		</tr>
		<tr>
			<td>Surfactant P-20</td>
			<td>GE Healthcare</td>
			<td>BR-1000-54</td>
			<td></td>
		</tr>
		<tr>
			<td>Glycine 2.0</td>
			<td>GE Healthcare</td>
			<td>BR-1003-55</td>
			<td></td>
		</tr>
		<tr>
			<td>Zeba spin desalting column</td>
			<td>Thermo</td>
			<td>89882</td>
			<td>7 K MWCO</td>
		</tr>
		<tr>
			<td>Amicon Ultra 4</td>
			<td>Fisher</td>
			<td>UFC810096</td>
			<td>100 K centrifugal filter</td>
		</tr>
		<tr>
			<td>TCO-OH</td>
			<td>Ref. 8</td>
			<td></td>
			<td>Synthesized in-house</td>
		</tr>
		<tr>
			<td>TCO-NHS</td>
			<td>Ref. 8</td>
			<td></td>
			<td>Synthesized in-house, *Commercially available from Click Chemistry Tools # 1016-25</td>
		</tr>
		<tr>
			<td>Tz-BnNH2</td>
			<td>Ref. 8</td>
			<td></td>
			<td>Synthesized in-house</td>
		</tr>
		<tr>
			<td>Tz-NHS</td>
			<td>Ref. 8</td>
			<td>764701</td>
			<td>Synthesized in-house, *Commercially available from Sigma Aldrich # 764701</td>
		</tr>
		<tr>
			<td>NP-NH2 = CLIO-NH2</td>
			<td>Ref. 8</td>
			<td></td>
			<td>Synthesized in-house</td>
		</tr>
		<tr>
			<td>AP1497, AP1497-Tz</td>
			<td>Ref. 8</td>
			<td></td>
			<td>Synthesized in-house</td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td>Equipment</td>
		</tr>
		<tr>
			<td>SPR Biosensor</td>
			<td>GE Healthcare</td>
			<td>Biacore T100</td>
			<td></td>
		</tr>
	</tbody>
</table>

microfluidic on-chip capture-cycloaddition reaction to reversibly immobilize small molecules or multi-component structures for biosensor applications

Methods for rapid surface immobilization of bioactive small molecules with control over orientation and immobilization density are highly desirable for biosensor and microarray applications. In this Study, we use a highly efficient covalent bioorthogonal [4+2] cycloaddition reaction between trans-cyclooctene (TCO) and 1,2,4,5-tetrazine (Tz) to enable the microfluidic immobilization of TCO/Tz-derivatized molecules. We monitor the process in real-time under continuous flow conditions using surface plasmon resonance (SPR). To enable reversible immobilization and extend the experimental range of the sensor surface, we combine a non-covalent antigen-antibody capture component with the cycloaddition reaction. By alternately presenting TCO or Tz moieties to the sensor surface, multiple capture-cycloaddition processes are now possible on one sensor surface for on-chip assembly and interaction studies of a variety of multi-component structures. We illustrate this method with two different immobilization experiments on a biosensor chip; a small molecule, AP1497 that binds FK506-binding protein 12 (FKBP12); and the same small molecule as part of an immobilized and in situ-functionalized nanoparticle.

Data and figures have been adapted from reference 8. 
 Efficient reversible immobilization of bioactive small molecules with control over orientation and density plays a key role in development of new biosensor applications. Using the fast bioorthogonal reaction between TCO and Tz, we describe a method for the stepwise assembly and regeneration of ligand surfaces with retention of biological activity. Figure 2 shows the real-time monitoring of Tz-BnNH2 immobil...

Watch this Scientific Journal Video about Microfluidic On-chip Capture-cycloaddition Reaction to Reversibly Immobilize Small Molecules or Multi-component Structures for Biosensor Applications at JoVE.

Microfluidic On-chip Capture-cycloaddition Reaction to Reversibly Immobilize Small Molecules or Multi-component Structures for Biosensor Applications

We present a method for rapid, reversible immobilization of small molecules and functionalized nanoparticle assemblies for Surface Plasmon Resonance (SPR) studies, using sequential on-chip bioorthogonal cycloaddition chemistry and antibody-antigen capture.

Methods  for rapid surface immobilization of bioactive small molecules with control over  orientation and immobilization density are highly desirable for ...

microfluidic-on-chip-capture-cycloaddition-reaction-to-reversibly

Research

JoVE Journal

Chemistry

10.7K Görüntüleme.  Massachusetts General Hospital.  Biz sıralı on-chip bioorthogonal Siklokatılma kimya ve antikor-antijen yakalama kullanarak, küçük moleküllerin hızlı, geri dönüşümlü immobilizasyon ve Yüzey Plazmon Rezonans (SPR) çalışmaları için işlevselleştirilen nanoparçacık meclisleri için bir yöntem mevcut. 

Video: Microfluidic On-chip Capture-cycloaddition Reaction to Reversibly Immobilize Small Molecules or Multi-component Structures for Biosensor Applications