The authors would like to acknowledge Mr. Richard Zink and Todd Wiernicki for methodological training and assay guidance. We also thank John Paul Spence for careful reading and editorial suggestions. This work was supported by the National Institute of Health MH 060397, Brain and Behavior Research Foundation, and Eli Lilly and Company through the Lilly Research Award Program (LRAP).

1. Expansion and Cryopreservation of Assay Ready Cells
<ol>
	<li>Culture CHO-K1-DRD2L (CHO-D2L) cells on a 15 cm2 cell culture dish in Ham&#39;s F12 media supplemented with 1.0 &#956;M L-glutamine, 800 &#956;g/&#956;l G418, 300 &#956;g/&#956;l hygromycin, 100 u/&#956;l penicillin, 100 &#956;g/&#956;l streptomycin, and 10% fetal bovine serum (FBS).</li>
	<li>Incubate the cells at 37 &#176;C in a humidified incubator with 5% CO2 until the cells are 90-95% confluent. Wash the cells with 10 &#956;l Phosphate Buffered Saline (PBS), and harvest the cells by adding 3 &#956;l of cell dissociation buffer for 5 min at 37 &#176;C. Resuspend the cells using 12 &#956;l of the culture media and count cells using trypan blue exclusion.</li>
	<li>Centrifuge the cell suspension at 500 x g for 5 min at room temperature. Aspirate the supernatant and resuspend the cell pellet in 5 &#956;l of freezing media (10% dimethyl sulfoxide, 90% FBS). Dilute the cell suspension to achieve the desired cell concentration (e.g. 1-20 x 106 cells/&#956;l).</li>
	<li>Aliquot 1.0 &#956;l of cell solution to each cryovial. Incubate the cryovials in a cell freezing container at -80 &#176;C overnight. Transfer the cryovials to a liquid N2 tank for long term storage.</li>
</ol>
2. Plating Assay Ready Cells (and Reverse Transfection Option)
<ol>
	<li>Rapidly thaw a frozen cryovial of cells in a 37 &#176;C water bath. Once cells are thawed, transfer the cells to a 15 &#956;l conical tube containing 9 &#956;l of Opti-MEM, and mix by inverting the tube 3-5x.</li>
	<li>Centrifuge the cells at 500 x g for 5 min at room temperature. Aspirate the supernatant and resuspend the cells in 1 &#956;l Opti-MEM.</li>
	<li>Count the cells using trypan blue exclusion to determine cell viability and dilute the viable cells as necessary (e.g. 3 x 105 cells/&#956;l concentration) in Opti-MEM. Plate 10 &#956;l/well of cells in a tissue culture treated 384-well plate using a multichannel pipette.</li>
	<li>Make serial dilutions of cAMP in Opti-MEM to generate a standard curve for estimating cAMP production by the cells (according to the manufactures recommendations - see Section 7). Add 10 &#956;l/well of the cAMP standards to the plate. Note: a single standard curve can be prepared on a separate plate or blank wells on one of the assay plates.</li>
	<li>Centrifuge the plate at 100 x g for 15 sec at room temperature, and incubate at 37 &#176;C in a humidified incubator with 5% CO2 for 1 hr.</li>
</ol>
3. Reverse siRNA Transfection Option*
This section is optional and relevant to Figure 3.
<ol>
	<li>Prepare a solution of siRNA in RNase-free ddH2O (e.g. 0.4 pmol/&#956;l). Add 5 &#956;l to individual wells of 384-well plate, and centrifuge the plate at 100 x g for 15 sec at room temperature.</li>
	<li>Dilute Lipofectamine 2000 in Opti-MEM by a factor of 0.006 (e.g. add 6 &#956;l of Lipofectamine 2000 to 1,000 &#956;l of Opti-MEM), and mix by pipetting up and down.</li>
	<li>Incubate the Lipofectamine 2000/Opti-MEM solution for 5 min at room temperature. Add 5 &#956;l of the diluted Lipofectamine 2000/Opti-MEM solution to individual wells of 384-well plate that already contains siRNA. Centrifuge the plate at 100 x g for 15 sec at room temperature.</li>
	<li>Incubate the plate for 30 min at room temperature.</li>
	<li>Plate assay ready cells as described above (Section 2). Centrifuge the plate at 100 x g for 15 sec at room temperature.</li>
	<li>Return assay plate to humidified incubator at 37 &#176;C (5% CO2) for 48-96 hr as determined for targeted gene knock down (see discussion).</li>
</ol>
4. Small Molecule Screening
<ol>
	<li>Dilute the drug of interest (e.g. small molecule inhibitors) in Opti-MEM to 6x the desired final concentrations. Serial dilutions can be completed using hand-held pipettes or a liquid handling station.</li>
	<li>Add 2.5 &#956;l/well of the test compound or buffer containing vehicle (e.g. DMSO) to the side of the wells using a multichannel pipette.</li>
	<li>Centrifuge the plate at 100 x g for 15 sec at room temperature (incubation is optional).</li>
</ol>
5. Persistent Agonist Treatment
<ol>
	<li>Prepare a 600 nM (i.e. 6 times the desired final concentration of 100 nM) solution of quinpirole in Opti-MEM.</li>
	<li>Add 2.5 &#956;l/well of the 600 nM quinpirole solution to the side of the wells using a multichannel pipette.</li>
	<li>Centrifuge the plate at 100 x g for 15 sec at room temperature, and incubate at 37 &#176;C in a humidified incubator with 5% CO2 for 2 hr.</li>
</ol>
6. Stimulation of cAMP Accumulation
<ol>
	<li>During the 2 hr incubation, prepare the stimulation solution in Opti-MEM. The stimulation solution is comprised of 40 &#956;M forskolin, 2 &#956;M 3-isobutyl-1-methyxanthine (IBMX), and 4 &#956;M spiperone (all concentrations in step 6 are 4x the desired final concentration).</li>
	<li>Add 5 &#956;l/well of the stimulation solution to the side of the wells using a multichannel pipette.</li>
	<li>Centrifuge the plate at 100 x g for 15 sec at room temperature, and incubate at room temperature for 1 hr.</li>
</ol>
7. Quenching and Estimation of cAMP Accumulation
<ol>
	<li>Production of cAMP by the cells is measured using the cAMP dynamic 2 kit according to manufacturer&#8217;s instructions. Briefly, reconstitute anti-cAMP-cryptate and cAMP-d2 in distilled water. Freeze aliquots at -20 &#176;C for short term storage.</li>
	<li>Dilute one aliquot of anti-cAMP-cryptate and one aliquot of cAMP-d2 separately in the lysis buffer according to the manufacturer&#8217;s instructions to make working solutions.</li>
	<li>Add 10 &#956;l/well of the anti-cAMP-cryptate working solution and 10 &#956;l/well of the cAMP-d2 working solution to the 384-well plate using a multichannel pipette.</li>
	<li>Centrifuge the plate at 100 x g for 15 sec at room temperature, and incubate at room temperature for 1 hr.</li>
	<li>Read the plate in a fluorescence plate reader (auto scale setting for sensitivity) using an excitation of 337 nm, and measure the emissions at 620 nm and 665 nm per manufactures instructions.</li>
	<li>Apply ratiometric analysis to assess cAMP standard curve per manufactures instructions. Using the resulting values, extrapolate the estimated cAMP accumulation in the test wells using data analysis software.</li>
</ol>

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The authors have nothing to disclose.

In an effort to facilitate studies of heterologous sensitization, we have extensively modified our previous method achieving a streamlined "mix and read" format that is amendable to high-throughput screening and mechanism of action examination. The major modifications to our protocol can be summarized as follows: 1) the use of cryopreserved cells as "assay-ready" reagents; 2) the miniaturization of the assay into 384-well format; and 3) the utilization of the HTRF measurement of cAMP.
The adop...

An adaptive adenylyl cyclase (AC) signaling response known as heterologous- or super-sensitization was first discovered in the laboratory of Nobel Laureate, Dr. Marshall Nirenberg. Dr. Nirenberg proposed that the observed increased AC responsiveness following chronic &#948; opioid receptor activation was a mechanism involved in opiate tolerance and dependence1. In addition to chronic &#948; opioid receptor activation, this neuroadaptive response of AC signaling also occurs following persistent activation of several other G&#945;i/o-coupled receptors2. Notably, many of these receptors are associated with pain, neuropsychiatric and neurological disorders, and include &#956;/&#954; opioid, D2/4 dopamine, 5HT1A, and M2/4 muscarinic receptors2. In addition to Dr. Nirenberg&#39;s findings, a large body of evidence exists linking sensitization of AC signaling to chronic opioid receptor activation both in vitro and in vivo3-7. Sensitization of AC has also been associated with a variety of diseases involving D2-like dopamine receptors including schizophrenia and Parkinson&#39;s disease (for review see reference2). Despite the potential importance of sensitization, the precise mechanism(s) associated with persistent G&#945;i/o-coupled receptor activation that leads to increased AC responsiveness remains largely unknown.
These studies provide the rationale for examining the mechanisms for sensitization of adenylyl cyclase as an important neurobiological target. Likewise, the physiological relevance of AC signaling8 and the importance that the individual AC isoforms hold in this adaptive response should also be recognized2,9,10. In the context of our research, the general features associated with heterologous sensitization of the recombinant isoforms of AC parallel those characteristics described for studying the endogenous isoforms of AC. Specifically, previous research has found that the activation of G&#945;i/o proteins and subsequent release/rearrangement &#946;&#947; subunits are important requirements for receptor induced sensitization of all AC isoforms. Additionally, several studies suggest that signaling from protein kinases and G&#946;&#947; subunits are involved in sensitization2,11-13. Individual ACs also display unique and distinct sensitization patterns12. For instance, persistent exposure of D2 receptors to agonists is associated with sensitization of AC1 and AC8 to Ca2+/calmodulin stimulation14,15, whereas the closely related AC3 is not sensitized2. AC2, AC4, and AC7 are closely related, however, only PKC-stimulated AC2 activity is robustly sensitized after prolonged exposure of D2 receptors to agonists7,14,16,17. Additionally, AC5 and AC6 show a marked degree of heterologous sensitization to Gas- and forskolin-stimulated cAMP accumulation following activation of D2 receptors14,18-20, but appear to differ in their requirement for G&#946;&#947; subunit-AC interactions21. Although most studies of AC sensitization have used model cell lines (e.g. HEK293 cells expressing individual AC isoforms), it appears that these findings translate to native neuronal cell models4,22. More recently, the effects of AC isoform selective small molecule inhibitors identified in HEK293 cells expressing AC isoforms can also be translated to in vivo behavioral studies23.
The lack of an identified molecular mechanism for heterologous sensitization likely reflects the complexity of the adaptive response as well as the unique regulatory properties of the individual AC isoforms12. Unraveling such complexity is further complicated by the use of cumbersome methodology that has limited academic investigators from employing unbiased approaches. For example, our previous mechanistic studies involved the use of continuously cultured cellular models using 24- and 48-well tissue culture format15. Cultured cells were typically grown for 48 hr and then subjected to agonist drug treatment (2-18 hr) followed by a series of cell washes and incubations (Figure 1). AC-isoform specific cAMP accumulation protocols were then employed followed by measurement of cAMP accumulation using a laborious and time consuming [3H]cAMP binding methodology15,24. The duration from start to finish for each assay generally required a total of four to five days from cell plating to data analysis (Figure 1). The application of new technologies and automation has led to marked enhancements for sensitization studies in the industrial and HTS center setting. For example, a group working with the National Center for Chemical Genomics reported a two day HTS assay procedure for identifying small molecule inhibitors of &#956; opioid receptor induced sensitization in 1,536-well format25.
The present article describes our efforts to develop an HTS assay for studies of heterologous sensitization using technologies that are available at most academic research institutions. This strategy was accomplished by incorporating the use of cryopreserved cells from cell models heterologously expressing the D2 dopamine receptor in combination with endogenous or individual recombinant adenylyl cyclase isoforms (CHO-D2L or HEK-AC6/D2L). To improve our throughput, we redesigned our 48 well sensitization assay (ca. &#62;20 steps over 4-5 days) to a five-step, single day assay in 384-well format that was essentially "mix and read". The new format uses a commercially available homogenous time resolved fluorescence (HTRF) assay to measure cAMP accumulation in intact cells with a multi mode plate reader. The assay is robust and amenable to small molecule screening, and can be effectively applied to screen for inhibitors of heterologous sensitization. In addition, we provide data that allows the use of this assay with reverse transfection of siRNA for targeted or genome wide siRNA library screening with only a minor modification to the general approach.

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	<tbody>
		<tr height="28">
			<td height="28" style="height:28px;width:205px;">CHO-K1-DRD2L cells</td>
			<td style="width:144px;">DiscoveRx</td>
			<td style="width:148px;">930579C2</td>
			<td style="width:199px;"></td>
		</tr>
		<tr height="28">
			<td height="28" style="height:28px;width:205px;">Ham&#8217;s F12 media</td>
			<td style="width:144px;">VWR</td>
			<td style="width:148px;">SH30026fs</td>
			<td></td>
		</tr>
		<tr height="28">
			<td height="28" style="height:28px;width:205px;">Fetal Bovine Serum</td>
			<td style="width:144px;">VWR</td>
			<td style="width:148px;">SH3007003</td>
			<td></td>
		</tr>
		<tr height="28">
			<td height="28" style="height:28px;width:205px;">G418</td>
			<td style="width:144px;">Sigma</td>
			<td style="width:148px;">A1720</td>
			<td></td>
		</tr>
		<tr height="28">
			<td height="28" style="height:28px;width:205px;">Hygromycin</td>
			<td style="width:144px;">Fisher</td>
			<td style="width:148px;">50-230-5556</td>
			<td></td>
		</tr>
		<tr height="28">
			<td height="28" style="height:28px;width:205px;">Penicillin/ streptomycin</td>
			<td style="width:144px;">Life Technologies</td>
			<td style="width:148px;">15070063</td>
			<td></td>
		</tr>
		<tr height="28">
			<td height="28" style="height:28px;width:205px;">15 cm dishes</td>
			<td style="width:144px;">BD Falcon</td>
			<td style="width:148px;">353025</td>
			<td></td>
		</tr>
		<tr height="28">
			<td height="28" style="height:28px;width:205px;">DMSO</td>
			<td style="width:144px;">Sigma</td>
			<td style="width:148px;">D2650</td>
			<td></td>
		</tr>
		<tr height="28">
			<td height="28" style="height:28px;width:205px;">Cell dissociation buffer</td>
			<td style="width:144px;">Life Technologies</td>
			<td style="width:148px;">13150016</td>
			<td></td>
		</tr>
		<tr height="28">
			<td height="28" style="height:28px;width:205px;">Phosphate Buffered Saline</td>
			<td style="width:144px;">Life Technologies</td>
			<td style="width:148px;">10010-049</td>
			<td></td>
		</tr>
		<tr height="28">
			<td height="28" style="height:28px;width:205px;">Cryovials</td>
			<td style="width:144px;">Fisher</td>
			<td style="width:148px;">976171</td>
			<td></td>
		</tr>
		<tr height="28">
			<td height="28" style="height:28px;width:205px;">Opti-MEM</td>
			<td style="width:144px;">Life Technologies</td>
			<td style="width:148px;">31985070</td>
			<td></td>
		</tr>
		<tr height="28">
			<td height="28" style="height:28px;width:205px;">TC treated 384 well plates</td>
			<td style="width:144px;">Perkin-Elmer</td>
			<td style="width:148px;">6007688</td>
			<td></td>
		</tr>
		<tr height="66">
			<td height="66" style="height:66px;width:205px;">HTRF cAMP Dynamic 2 kit</td>
			<td style="width:144px;">Cisbio Bioassays</td>
			<td style="width:148px;">62AM4PEB</td>
			<td style="width:199px;">http://www.htrf.com/camp-cell-based-assay</td>
		</tr>
		<tr height="28">
			<td height="28" style="height:28px;width:205px;">Synergy 4</td>
			<td style="width:144px;">Biotek</td>
			<td style="width:148px;">H4MLFPTAD</td>
			<td></td>
		</tr>
		<tr height="28">
			<td height="28" style="height:28px;width:205px;">Prism 6</td>
			<td style="width:144px;">GraphPad Software</td>
			<td style="width:148px;">NA</td>
			<td></td>
		</tr>
		<tr height="28">
			<td height="28" style="height:28px;width:205px;">3-Isobutyl-1-methylxanthine</td>
			<td style="width:144px;">Sigma</td>
			<td style="width:148px;">I5879</td>
			<td></td>
		</tr>
		<tr height="28">
			<td height="28" style="height:28px;width:205px;">(&#177;)Quinpirole</td>
			<td style="width:144px;">Sigma</td>
			<td style="width:148px;">Q111</td>
			<td></td>
		</tr>
		<tr height="28">
			<td height="28" style="height:28px;width:205px;">Spiperone</td>
			<td style="width:144px;">Sigma</td>
			<td style="width:148px;">S7395</td>
			<td></td>
		</tr>
		<tr height="28">
			<td height="28" style="height:28px;width:205px;">Clozapine</td>
			<td style="width:144px;">Sigma</td>
			<td style="width:148px;">C6305</td>
			<td></td>
		</tr>
		<tr height="28">
			<td height="28" style="height:28px;width:205px;">Haloperidol</td>
			<td style="width:144px;">Sigma</td>
			<td style="width:148px;">H1512</td>
			<td></td>
		</tr>
		<tr height="28">
			<td height="28" style="height:28px;width:205px;">S-(-)Sulpiride</td>
			<td style="width:144px;">Sigma</td>
			<td style="width:148px;">S112</td>
			<td></td>
		</tr>
		<tr height="55">
			<td height="55" style="height:55px;width:205px;">Lipofectamine2000 transfection reagent</td>
			<td style="width:144px;">Invitrogen</td>
			<td style="width:148px;">11668019</td>
			<td></td>
		</tr>
		<tr height="28">
			<td height="28" style="height:28px;width:205px;">Trypan blue</td>
			<td style="width:144px;">Life Technologies</td>
			<td style="width:148px;">T10282</td>
			<td></td>
		</tr>
		<tr height="28">
			<td height="28" style="height:28px;width:205px;">Water, DNase, RNase-free</td>
			<td style="width:144px;">MP Biomedicals</td>
			<td style="width:148px;">821739</td>
			<td></td>
		</tr>
		<tr height="28">
			<td height="28" style="height:28px;width:205px;">Gas siRNA</td>
			<td style="width:144px;">Dharmacon</td>
			<td style="width:148px;">custom siRNA</td>
			<td></td>
		</tr>
		<tr height="28">
			<td height="28" style="height:28px;width:205px;">Non-targeting siRNA control</td>
			<td style="width:144px;">Dharmacon</td>
			<td style="width:148px;">D-001206-14-20</td>
			<td></td>
		</tr>
		<tr height="28">
			<td height="28" style="height:28px;width:205px;">siGlo Red</td>
			<td style="width:144px;">Dharmacon</td>
			<td style="width:148px;">D-001630-02</td>
			<td></td>
		</tr>
	</tbody>
</table>

drug-induced sensitization of adenylyl cyclase: assay streamlining and miniaturization for small molecule and sirna screening applications

Sensitization of adenylyl cyclase (AC) signaling has been implicated in a variety of neuropsychiatric and neurologic disorders including substance abuse and Parkinson&#39;s disease. Acute activation of G&#945;i/o-linked receptors inhibits AC activity, whereas persistent activation of these receptors results in heterologous sensitization of AC and increased levels of intracellular cAMP. Previous studies have demonstrated that this enhancement of AC responsiveness is observed both in vitro and in vivo following the chronic activation of several types of G&#945;i/o-linked receptors including D2 dopamine and &#956; opioid receptors. Although heterologous sensitization of AC was first reported four decades ago, the mechanism(s) that underlie this phenomenon remain largely unknown. The lack of mechanistic data presumably reflects the complexity involved with this adaptive response, suggesting that nonbiased approaches could aid in identifying the molecular pathways involved in heterologous sensitization of AC. Previous studies have implicated kinase and Gb&#947; signaling as overlapping components that regulate the heterologous sensitization of AC. To identify unique and additional overlapping targets associated with sensitization of AC, the development and validation of a scalable cAMP sensitization assay is required for greater throughput. Previous approaches to study sensitization are generally cumbersome involving continuous cell culture maintenance as well as a complex methodology for measuring cAMP accumulation that involves multiple wash steps. Thus, the development of a robust cell-based assay that can be used for high throughput screening (HTS) in a 384&#160;well format would facilitate future studies. Using two D2 dopamine receptor cellular models (i.e.&#160;CHO-D2L and HEK-AC6/D2L), we have converted our 48-well sensitization assay (&#62;20 steps 4-5 days) to a five-step, single day assay in 384-well format. This new format is amenable to small molecule screening, and we demonstrate that this assay design can also be readily used for reverse transfection of siRNA in anticipation of targeted siRNA library screening.

Part I. Developing a 384 well heterologous sensitization assay for identifying small molecule inhibitors using a commercially available cell model.
To study heterologous sensitization in a cell model, we made a number of improvements that enabled us to streamline the assay into a "mix and read" format. Several of the key modifications are highlighted below, and are described in more detail in the discussion. The first key step was modifying our cell culture from continuously c...

Watch this Scientific Journal Video about Drug-induced Sensitization of Adenylyl Cyclase: Assay Streamlining and Miniaturization for Small Molecule and siRNA Screening Applications at JoVE.com

Drug-induced Sensitization of Adenylyl Cyclase: Assay Streamlining and Miniaturization for Small Molecule and siRNA Screening Applications

Persistent activation of inhibitory G protein-coupled receptors results in sensitization of adenylyl cyclase signaling. To identify the essential molecular pathways, nonbiased approaches are necessary; however, this strategy requires the development of a scalable cell-based cAMP sensitization assay. Herein, we describe a sensitization assay for small molecule and siRNA screening.

Sensitization of adenylyl cyclase (AC) signaling has been implicated in a variety of neuropsychiatric and neurologic disorders including substance abuse ...

drug-induced-sensitization-adenylyl-cyclase-assay-streamlining

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JoVE Journal

Bioengineering

12.6K Views.  Purdue University. Persistent activation of inhibitory G protein-coupled receptors results in sensitization of adenylyl cyclase signaling. To identify the essential molecular pathways, nonbiased approaches are necessary; however, this strategy requires the development of a scalable cell-based cAMP sensitization assay. Herein, we describe a sensitization assay for small molecule and siRNA screening.

Video: Drug-induced Sensitization of Adenylyl Cyclase: Assay Streamlining and Miniaturization for Small Molecule and siRNA Screening Applications

Cell-based Calcium Assay for Medium to High Throughput Screening of TRP Channel Functions using FlexStation 3

The Molecular Devices' FlexStation 3 is a benchtop multi-mode microplate reader capable of automated fluorescence measurement in multi-well plates. It is ideal for medium- to high-throughput screens in academic settings. It has an integrated fluid transfer module equipped with a multi-channel pipetter and the machine reads one column at a time to monitor fluorescence changes of a variety of fluorescent reagents. For example, FlexStation 3 has been used to study the function of Ca2+-permeable ion channels and G-protein coupled receptors by measuring the changes of intracellular free Ca2+ levels. Transient receptor potential (TRP) channels are a large family of nonselective cation channels that play important roles in many physiological and pathophysiological functions. Most of the TRP channels are calcium permeable and induce calcium influx upon activation. In this video, we demonstrate the application of FlexStation 3 to study the pharmacological profile of the TRPA1 channel, a molecular sensor for numerous noxious stimuli. HEK293 cells transiently or stably expressing human TRPA1 channels, grown in 96-well plates, are loaded with a Ca2+-sensitive fluorescent dye, Fluo-4, and real-time fluorescence changes in these cells are measured before and during the application of a TRPA1 agonist using the FLEX mode of the FlexStation 3. The effect of a putative TRPA1 antagonist was also examined. Data are transferred from the SoftMax Pro software to construct concentration-response relationships of TRPA1 activators and inhibitors.

This video provides a detailed protocol for studying the pharmacological profile of human TRPA1 channels using FlexStation 3. The protocol covers details of cell preparation, dye loading and operation of the microplate reader, FlexStation 3.

The Molecular Devices' FlexStation 3 is a benchtop multi-mode microplate reader capable of automated fluorescence measurement in multi-well plates.  It is ...

Wideband Optical Detector of Ultrasound for Medical Imaging Applications

Optical sensors of ultrasound are a promising alternative to piezoelectric techniques, as has been recently demonstrated in the field of optoacoustic imaging. In medical applications, one of the major limitations of optical sensing technology is its susceptibility to environmental conditions, e.g. changes in pressure and temperature, which may saturate the detection. Additionally, the clinical environment often imposes stringent limits on the size and robustness of the sensor. In this work, the combination of pulse interferometry and fiber-based optical sensing is demonstrated for ultrasound detection. Pulse interferometry enables robust performance of the readout system in the presence of rapid variations in the environmental conditions, whereas the use of all-fiber technology leads to a mechanically flexible sensing element compatible with highly demanding medical applications such as intravascular imaging. In order to achieve a short sensor length, a pi-phase-shifted fiber Bragg grating is used, which acts as a resonator trapping light over an effective length of 350 &#181;m. To enable high bandwidth, the sensor is used for sideway detection of ultrasound, which is highly beneficial in circumferential imaging geometries such as intravascular imaging. An optoacoustic imaging setup is used to determine the response of the sensor for acoustic point sources at different positions.

Optical detection of ultrasound is impractical in many imaging scenarios because it often requires stable environmental conditions. We demonstrate an optical technique for ultrasound sensing in volatile environments with miniaturization and sensitivity levels appropriate for optoacoustic imaging in restrictive scenarios, e.g. intravascular applications.

Optical sensors of ultrasound are a promising alternative to piezoelectric techniques, as has been recently demonstrated in the field of optoacoustic ...

Porous Silicon Microparticles for Delivery of siRNA Therapeutics

Small interfering RNA (siRNA) can be used to suppress gene expression, thereby providing a new avenue for the treatment of various diseases. However, the successful implementation of siRNA therapy requires the use of delivery platforms that can overcome the major challenges of siRNA delivery, such as enzymatic degradation, low intracellular uptake and lysosomal entrapment. Here, a protocol for the preparation and use of a biocompatible and effective siRNA delivery system is presented. This platform consists of polyethylenimine (PEI) and arginine (Arg)-grafted porous silicon microparticles, which can be loaded with siRNA by performing a simple mixing step. The silicon particles are gradually degraded over time, thereby triggering the formation of Arg-PEI/siRNA nanoparticles. This delivery vehicle provides a means for protecting and internalizing siRNA, without causing cytotoxicity. The major steps of polycation functionalization, particle characterization, and siRNA loading are outlined in detail. In addition, the procedures for determining particle uptake, cytotoxicity, and transfection efficacy are also described.

Delivery remains the main challenge for the therapeutic implementation of small interfering RNA (siRNA). This protocol involves the use of a multifunctional and biocompatible siRNA delivery platform, consisting of arginine and polyethylenimine grafted porous silicon microparticles.

Small interfering RNA (siRNA) can be used to suppress gene expression, thereby providing a new avenue for the treatment of various diseases. However, the ...

A Rapid and Quantitative Fluorimetric Method for Protein-Targeting Small Molecule Drug Screening

We demonstrate a new drug screening method for determining the binding affinity of small drug molecules to a target protein by forming fluorescent gold nanoclusters (Au NCs) within the drug-loaded protein, based on the differential fluorescence signal emitted by the Au NCs. Albumin proteins such as human serum albumin (HSA) and bovine serum albumin (BSA) are selected as the model proteins. Four small molecular drugs (e.g., ibuprofen, warfarin, phenytoin, and sulfanilamide) of different binding affinities to the albumin proteins are tested. It was found that the formation rate of fluorescent Au NCs inside the drug loaded albumin protein under denaturing conditions (i.e., 60 &#176;C or in the presence of urea) is slower than that formed in the pristine protein (without drugs). Moreover, the fluorescent intensity of the as-formed NCs is found to be inversely correlated to the binding affinities of these drugs to the albumin proteins. Particularly, the higher the drug-protein binding affinity, the slower the rate of Au NCs formation, and thus a lower fluorescence intensity of the resultant Au NCs is observed. The fluorescence intensity of the resultant Au NCs therefore provides a simple measure of the relative binding strength of different drugs tested. This method is also extendable to measure the specific drug-protein binding constant (KD) by simply varying the drug content preloaded in the protein at a fixed protein concentration. The measured results match well with the values obtained using other prestige but more complicated methods.

A protocol for small molecular drug screening based on in-situ synthesis of ultrasmall fluorescent gold nanoclusters (Au NCs) using drug-loaded protein as template is presented. This method is simple to determine the binding affinity of drugs to a target protein by a visible fluorescent signal emitted from the protein-templated Au NCs.

We demonstrate a new drug screening method for determining the binding affinity of small drug molecules to a target protein by forming fluorescent gold ...

Fabrication of Mechanically Tunable and Bioactive Metal Scaffolds for Biomedical Applications

Biometal systems have been widely used for biomedical applications, in particular, as load-bearing materials. However, major challenges are high stiffness and low bioactivity of metals. In this study, we have developed a new method towards fabricating a new type of bioactive and mechanically reliable porous metal scaffolds-densified porous Ti scaffolds. The method consists of two fabrication processes, 1) the fabrication of porous Ti scaffolds by dynamic freeze casting, and 2) coating and densification of the porous scaffolds. The dynamic freeze casting method to fabricate porous Ti scaffolds allowed the densification of porous scaffolds by minimizing the chemical contamination and structural defects. The densification process is distinctive for three reasons. First, the densification process is simple, because it requires a control of only one parameter (degree of densification). Second, it is effective, as it achieves mechanical enhancement and sustainable release of biomolecules from porous scaffolds. Third, it has broad applications, as it is also applicable to the fabrication of functionally graded porous scaffolds by spatially varied strain during densification.

Bioactive and mechanically reliable metal scaffolds have been fabricated through a method which consists of two processes, dynamic freeze casting for the fabrication of porous Ti, and coating and densification of the Ti scaffolds. The densification process is simple, effective and applicable to the fabrication of functionally graded scaffolds.

Biometal systems have been widely used for biomedical applications, in particular, as load-bearing materials. However, major challenges are high stiffness ...

Light-mediated Formation and Patterning of Hydrogels for Cell Culture Applications

Click chemistries have been investigated for use in numerous biomaterials applications, including drug delivery, tissue engineering, and cell culture. In particular, light-mediated click reactions, such as photoinitiated thiol&#8722;ene and thiol&#8722;yne reactions, afford spatiotemporal control over material properties and allow the design of systems with a high degree of user-directed property control. Fabrication and modification of hydrogel-based biomaterials using the precision afforded by light and the versatility offered by these thiol&#8722;X photoclick chemistries are of growing interest, particularly for the culture of cells within well-defined, biomimetic microenvironments. Here, we describe methods for the photoencapsulation of cells and subsequent photopatterning of biochemical cues within hydrogel matrices using versatile and modular building blocks polymerized by a thiol&#8722;ene photoclick reaction. Specifically, an approach is presented for constructing hydrogels from allyloxycarbonyl (Alloc)-functionalized peptide crosslinks and pendant peptide moieties and thiol-functionalized poly(ethylene glycol) (PEG) that rapidly polymerize in the presence of lithium acylphosphinate photoinitiator and cytocompatible doses of long wavelength ultraviolet (UV) light. Facile techniques to visualize photopatterning and quantify the concentration of peptides added are described. Additionally, methods are established for encapsulating cells, specifically human mesenchymal stem cells, and determining their viability and activity. While the formation and initial patterning of thiol-alloc hydrogels are shown here, these techniques broadly may be applied to a number of other light and radical-initiated material systems (e.g., thiol-norbornene, thiol-acrylate) to generate patterned substrates.

We describe a sequential process for light-mediated formation and subsequent biochemical patterning of synthetic hydrogel matrices for three-dimensional cell culture applications. The construction and modification of hydrogels with cytocompatible photoclick chemistry is demonstrated. Additionally, facile techniques to quantify and observe patterns and determine cell viability within these hydrogels are presented.

Click chemistries have been investigated for use in numerous biomaterials applications, including drug delivery, tissue engineering, and cell culture. In ...

Extraction of Plant-based Capsules for Microencapsulation Applications

Microcapsules derived from plant-based spores or pollen provide a robust platform for a diverse range of microencapsulation applications. Sporopollenin exine capsules (SECs) are obtained when spores or pollen are processed so as to remove the internal sporoplasmic contents. The resulting hollow microcapsules exhibit a high degree of micromeritic uniformity and retain intricate microstructural features related to the particular plant species. Herein, we demonstrate a streamlined process for the production of SECs from Lycopodium clavatum spores and for the loading of hydrophilic compounds into these SECs. The current SEC isolation procedure has been recently optimized to significantly reduce the processing requirements which are conventionally used in SEC isolation, and to ensure the production of intact microcapsules. Natural L. clavatum spores are defatted with acetone, treated with phosphoric acid, and extensively washed to remove sporoplasmic contents. After acetone defatting, a single processing step using 85% phosphoric acid has been shown to remove all sporoplasmic contents. By limiting the acid processing time to 30 hr, it is possible to isolate clean SECs and avoid SEC fracturing, which has been shown to occur with prolonged processing time. Extensive washing with water, dilute acids, dilute bases, and solvents ensures that all sporoplasmic material and chemical residues are adequately removed. The vacuum loading technique is utilized to load a model protein (Bovine Serum Albumin) as a representative hydrophilic compound. Vacuum loading provides a simple technique to load various compounds without the need for harsh solvents or undesirable chemicals which are often required in other microencapsulation protocols. Based on these isolation and loading protocols, SECs provide a promising material for use in a diverse range of microencapsulation applications, such as, therapeutics, foods, cosmetics, and personal care products.

This protocol/manuscript describes a streamlined process for the production of sporopollenin exine capsules (SECs) from Lycopodium clavatum spores and for the loading of hydrophilic compounds into these SECs.

Microcapsules derived from plant-based spores or pollen provide a robust platform for a diverse range of microencapsulation applications. Sporopollenin ...

Applications for Open Source Microplate-Compatible Illumination Panels

Microplates are commonly used in the modern laboratory environment for a wide variety of tasks both in small-scale laboratory benchtop operations as well as large-scale high-throughput screening (HTS) campaigns. Though laboratory automation has greatly increased the utility of microplates there remain instances where automation-based instrumentation is not feasible, cost-effective or compatible with microplate formatting needs. In these cases, microplates must be manually prepared. Problematic to manual microplate manipulations is that a number of difficulties can arise pertaining to the accurate tracking of sample operations, data record keeping and quality control (QC) inspection for well artifacts or formatting errors. As microplate well densities increase (i.e., 96-well, 384-well, 1536-well) the potential for introducing errors also drastically increases.&#160; Moreover, for small bench-top laboratory operations there exists a need to improve the ease and accuracy of sample handling in a cost-effective fashion. Herein, we describe a system that acts as a semi-automated pipetting guide referred to as the Microplate Assistive Pipetting Light Emitter (M.A.P.L.E.). &#160;M.A.P.L.E. has multiple uses for supporting compound hit-picking and microplate preparation for assay development in high-throughput screening or laboratory benchtop operations, as well as QC/quality assurance (QA) diagnostic evaluation of microplate quality or visualizing well formatting errors.

Microplate Assistive Pipetting Light Emitter (M.A.P.L.E.) is a computer-driven device that systematically illuminates microtiter wells to provide guidance for the manual preparation of microplates.&#160; M.A.P.L.E. improves the accuracy of microplate preparation while automating data recordkeeping. &#160;In addition, it can assist with examining microplate quality or aid in the detection of errors.&#160; &#160;

Microplates are commonly used in the modern laboratory environment for a wide variety of tasks both in small-scale laboratory benchtop operations as well ...

Screening and Identification of Small Peptides Targeting Fibroblast Growth Factor Receptor2 using a Phage Display Peptide Library

The human Fibroblast Growth Factor Receptor (FGFR) family comprises four members, namely, FGFR1, FGFR2, FGFR3, and FGFR4, that are involved in various biological activities including cell proliferation, survival, migration and differentiation. Several aberrations in the FGFR signaling pathway, owing to mutations or gene amplification events, have been identified in various types of cancers. Hence, recent research has focused on developing strategies involving therapeutic targeting of FGFRs. Current FGFR inhibitors at various stages of pre-clinical and clinical development include either small molecule inhibitors of tyrosine kinases or monoclonal antibodies, with only a few peptide- based inhibitors in the pipeline. Here, we provide a protocol using phage display technology to screen small peptides as antagonists of FGFR2. Briefly, a library of phage-displayed peptides was incubated in a plate coated with FGFR2. Subsequently, unbound phage was washed off by TBST (TBS + 0.1% [v/v] Tween-20), and bound phage was eluted with 0.2 M glycine-HCl buffer (pH 2.2). The eluted phage was further amplified and used as input for the next round of biopanning. Following three rounds of biopanning, the peptide sequences of individual phage clones were identified by DNA sequencing. Finally, the screened peptides were synthesized and analyzed for affinity and biological activity.

Herein, we present a detailed protocol for screening small peptides that bind to FGFR2 using a phage display peptide library. We further analyze the affinity of the selected peptides toward FGFR2 in vitro and its ability to suppress cell proliferation.

The human Fibroblast Growth Factor Receptor (FGFR) family comprises four members, namely, FGFR1, FGFR2, FGFR3, and FGFR4, that are involved in various ...

Rapid Fabrication of Custom Microfluidic Devices for Research and Educational Applications

Microfluidic devices allow for the manipulation of fluids, particles, cells, micro-sized organs or organisms in channels ranging from the nano to submillimeter scales. A rapid increase in the use of this technology in the biological sciences has prompted a need for methods that are accessible to a wide range of research groups. Current fabrication standards, such as PDMS bonding, require expensive and time consuming lithographic and bonding techniques. A viable alternative is the use of equipment and materials that are easily affordable, require minimal expertise and allow for the rapid iteration of designs. In this work we describe a protocol for designing and producing PET-laminates (PETLs), microfluidic devices that are inexpensive, easy to fabricate, and consume significantly less time to generate than other approaches to microfluidics technology. They consist of thermally bonded film sheets, in which channels and other features are defined using a craft cutter. PETLs solve field-specific technical challenges while dramatically reducing obstacles to adoption. This approach facilitates the accessibility of microfluidics devices in both research and educational settings, providing a reliable platform for new methods of inquiry.

Here we present a protocol to design and fabricate custom microfluidic devices with minimal financial and time investment. The aim is to facilitate the adoption of microfluidic technologies in biomedical research laboratories and educational settings.