D.C.H., M.B. and F.K. were supported by an EPSRC Follow on Fund. B.L-V and D.S. were each supported by MRC PhD studentships. K.C. was supported by funding from the UK Regenerative Medicine Platform.

1. Synthesis of PHNGAD (Poly[1,6-hexanodiol/neopentyl glycol/di(ethylene glycol)-alt-adipic acid]diol)
<img alt="Scheme 1" fo:content-width="5in" src="/files/ftp_upload/51723/51723scheme1.jpg" width="500" />
Scheme 1: Synthesis of PHNAGD. Schematic representation of the synthesis of PHNAGD. PHNAGD was prepared by the reaction of 1,6-Hexanodiol, diethylene glycol, neoppentyl glycol and adipic acid. PHNAGD, Poly[1,6-hexanodiol/neopentyl glycol/di(ethylene glycol)-alt-adipic acid]diol.
<ol>
	<li>Apply heat treatment to the monomers 1,6-hexanediol, di(ethylene glycol) and neopentyl glycol at 40 &#176;C for 48 hr in a vacuum oven to remove any residual water. Allow to cold down to RT under vacuum.</li>
	<li>Add 22 mmol of each monomer and adipic acid (55 mmol) to a two-necked round bottom flask equipped with a stirred bar and connected to a Dean-Stark apparatus.</li>
	<li>Place the whole assembly under a vacuum and gently heat the glassware at 40 &#176;C for 6 hr, in order to avoid any moisture absorption during the addition of the chemical into the flask.</li>
	<li>Add via syringe, drop by drop, 0.0055 mol of the catalyst titanium (IV) butoxide.</li>
	<li>Stir the reaction mixture at 180 &#176;C, under an N2 atmosphere for 24 hr, and collect residual water in the Dean-Stark trap. Allow the product to cool to RT.</li>
</ol>
2. Synthesis of PU134

<img alt="Scheme 2" fo:content-width="5in" src="/files/ftp_upload/51723/51723scheme2.jpg" width="500" />
Scheme 2: Synthesis of PU134. Schematic representation of the synthesis of polyurethane 134. PU134 was prepared by the reaction of 1.0 equiv of a PHNGAD with 2.0 equiv of a 4,4&#8242;-Methylenebis(phenyl isocyanate), followed by the addition of 1.0 equiv of a 1,4-butanediol chain extender.

<ol>
	<li>Mix one equivalent of the polyol PHNGAD (Mn ~1,800 Da, 3.2 mmol) with two equivalents of 4&#8217;4-Methylenebis(phenyl isocyanate) (6.4 mmol) in anhydrous N,N-Dimethylformamide (12 ml).</li>
	<li>Stir the reaction mixture at 70 &#176;C, under an N2 atmosphere.</li>
	<li>Add via syringe, drop by drop the catalyst titanium (IV) butoxide (0.8% wt).</li>
	<li>After 1 hr, add one equivalent of the chain extender 1,4-butanediol (3.2 mmol). Increase the temperature at 90 &#176;C and stir for 24 hr under an N2 atmosphere.</li>
	<li>Following the reaction, collect the polyurethane by precipitation by adding diethyl ether (hexane or water could also be used) drop wise into the reaction solution until the precipitation occurs.</li>
	<li>Centrifuge the solution at 5,300 x g for 5 min.</li>
	<li>Decant the supernatant and dry off at 40 &#176;C in a vacuum oven until the solvent evaporates. 
	Note: In order to ensure that the final product of the reaction possess the correct parameters regarding to the molecular weight distribution, the functional groups of the polymer, and the melting and glass transition temperatures, various analytical techniques and methods can be used, such as gel permeation chromatography or FITR spectroscopy.</li>
</ol>
3. Preparation of PU134 Solutions
<ol>
	<li>Weigh 200 mg of PU134 into a glass bottle.</li>
	<li>Dilute PU134 to a final concentration of 2% in a number of solvents: chloroform, a combination of chloroform and toluene in 1:1 ratio, tetrahydrofuran, and combination of tetrahydrofuran and dicloromethane in 1:1 ratio. 
	Note: The election of the right solvent varies depending on the polymer to use. Different solvents possess different boiling points that can affect the solubilization of the polymer.</li>
	<li>Shake the solution vigorously for 20 min at RT&#160;using a shaker at a speed of 200 mot/min, until the solution becomes homogeneous and no precipitate is observed.</li>
</ol>
4. Coating of Glass Slides with PU134
<ol>
	<li>Place a round 15 mm2 coverslip on the spin coater.</li>
	<li>Apply 50 &#956;l of the PU134 solution to each using a pipette. Adjust the volume of the PU134 solution accordingly for the required coverslip size keeping the volume to surface ratio proportional.</li>
	<li>Spin each coverslip for 7 sec at 23 x g.</li>
	<li>Air dry coverslip at RT for at least 24 hr before sterilization.</li>
</ol>
5. Irradiation of Coverslip
<ol>
	<li>Gamma-irradiate polymer coated coverslip by applying a dose of 10 Grays using a laboratory irradiator for 12 min.</li>
	<li>UV- irradiate polymer coated coverslip using a 30 W, UV bulb for 16 min each side.</li>
	<li>Place the polymer coated coverslip in a suitable tissue culture plate according to the slide size.</li>
</ol>
6. Scanning Electron Microscopy
<ol>
	<li>Gold coat polymer coverslip by sputtering for 200 sec in an atmosphere of 5 x 10-1 millibars of pressure.</li>
	<li>Capture the micrographs of the polymer coated coverslip using a scanning electron microscope at an accelerating voltage of 20 kV in secondary electron imaging mode.</li>
</ol>
7. Atomic Force Microscopy Observations
<ol>
	<li>Scan an area of 20 x 20 &#956;m of the polymer surface.</li>
	<li>Set up a scan rate from 1.32 Hz to 1.60 Hz.</li>
	<li>Set up a resolution of 512 x 512 pixels in the scanned region.</li>
	<li>Calculate the root mean square (RMS or Rq) of the coating by using the average of height deviations taken from the mean image data plane, expressed as: 
	<img fo:content-width="1in" src="/files/ftp_upload/51723/51723eq1.jpg" width="123" /> 
	Where Zi is the current Z value, and N is the number of points within the given area.</li>
	<li>7.5 Calculate the deviation or mean surface roughness (Ra) of the image using, 
	<img fo:content-width="1.5in" src="/files/ftp_upload/51723/51723eq2.jpg" width="154" /> 
	Where Z (x) is the function that describes the surface profile analyzed in terms of height (Z) and position (x) of the sample over the evaluation length &#8220;L&#8221;. Ra represents the mean value of the surface relative to the center plane.</li>
</ol>
8. Cell Culture and Differentiation
<ol>
	<li>Culture and differentiate the human embryonic stem cell line (hESC) H9 as described in Hay 17.</li>
	<li>Detach cells using a dissociation reagent and replate them onto PU134 coated slides at Day 9 of the differentiation process, in the presence of a serum free medium as describe in Szkolnicka 18,19. 
	Note: The use of an enzymatic cell dissociation is preferred to physical cell detachment.</li>
</ol>
9. Cytochrome p450 Functional Assay
<ol>
	<li>Measure CYP3A activity following the manufacturer&#8217;s instructions.</li>
	<li>Incubate hESC derived hepatocytes at Day 13 or Day 19, and media without cells - as a negative control, with the appropriate substrate for 5 hr at 37 &#176;C.</li>
	<li>Collect supernatants from cells and media, carry out the assay as per manufacturer&#8217;s instructions.</li>
	<li>Measure the level of CYP activity and normalized relative to the surface area (cm2).</li>
</ol>
10. Immunostaining
<ol>
	<li>Wash hESC derived hepatocytes with PBS, for 1 min, repeat two times.</li>
	<li>Add ice cold 100% methanol to fix cells, place in -20 &#176;C for 10 min.</li>
	<li>Wash cells with PBS for 5 min and repeat twice.</li>
	<li>Incubate cells with PBS/T (0.1% tween)/10% BSA for 1 hr at RT.</li>
	<li>Aspirate the PBST solution and add the appropriate primary antibody diluted in PBS/T (0.1% tween)/1% BSA, incubate at 4 &#176;C with gentle agitation O/N.</li>
	<li>Wash cells with PBS/T (0.1% tween)/1% BSA for 5 min and repeat three times.</li>
	<li>Dilute the appropriate antibody in PBS/T (0.1% tween)/1% BSA, add to the cells and incubate in the dark at RT for 1 hr with gentle agitation.</li>
	<li>Wash cells with PBS for 5 min and repeat three times.</li>
	<li>Add MOWIOL 488 (containing DAPI 1:1,000) to each well, add a coverslip gently to reduce number of air bubbles. Store fixed cells at 4 &#176;C in the dark. Observe staining using a microscope with appropriate filter and fluorescent lamp. The optimized primary and secondary antibodies are listed in Table 1.</li>
</ol>

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D.C.H. is CSO, Director, founder and a shareholder in FibromEd Products Ltd. M.B. and J.P.I. are founder shareholders in FibromEd Products Ltd.

Many of the current methods used to generate hepatocytes from stem cells rely on undefined matrices of animal origin. These substrates can be costly and highly variable, affecting cell function and stability, representing a significant barrier to application. Therefore, we performed a screen for synthetic materials which support the culture of stem cell derived hepatocytes. We have identified, a simple polyurethane (PU134), formed by polymerizing PHNGAD, MDI and an extender, that in combination with a robust hepatocyte d...

Biological materials have been widely used in the maintenance and differentiation of pluripotent stem cells 1. While enabling, these biological substrates often contain a myriad of undefined components. Matrigel is a commonly used substrate for stem cell culture and differentiation. Unfortunately, its variable composition influences cell function and phenotype. Although a variety of alternative, more defined biological matrices have been used 2-7, their animal origin or poor scalability makes them unsuitable candidates for industrial manufacture. Therefore the identification of synthetic alternatives, with defined composition and reliable performance, are key goals in stem cell research.
In an attempt to overcome the limitations of undefined cell culture substrates, interdisciplinary collaborations between chemistry and biology have identified synthetic materials with the capacity to support cell phenotype. Synthetic substrates are scalable, cost effective, and can be manufactured into complex 3D structures, mimicking the in vivo environment. Due to these properties synthetic substrates have been widely used to support and drive differentiation of many cell types 8-10.
Advanced and high throughput assays have facilitated the rapid screening of synthetic materials, from large libraries, and delivered novel materials with flexible properties with wide applications in biomedical research and development 11-13. Utilizing high throughput, polymer micro-array screening technology, we rapidly identified a simple polyurethane (PU134), suitable for maintenance of human stem cell derived hepatocytes. This polymer was found to be superior to animal derived substrates with regard to hepatocyte differentiation and function 14-16. We have subsequently optimized the coating conditions, topography and sterilization process to access effects on polymer performance in stabilizing hepatocyte function and lifespan. This has significant implications with regard to understanding fundamentals of hepatocyte biology for cell based modelling and regenerative medicine applications.
The technology here described represents an example of how the surface of a synthetic polymer can be optimized to preserve cell phenotype. We believe that the combination of this technology with an efficient serum free hepatocyte differentiation protocol has the potential to provide a scalable production of hepatocytes for use in in vitro modelling and regenerative medicine.

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td>Synthesis, preparation, coating and characterization of polymer PU134 coated coverslips</td>
		</tr>
		<tr>
			<td>Shaker</td>
			<td>Edmun B&#252;hler</td>
			<td>KS-15</td>
			<td></td>
		</tr>
		<tr>
			<td>Irradiator</td>
			<td>CIS Biointernational</td>
			<td>IBL 637&#160;</td>
			<td></td>
		</tr>
		<tr>
			<td>Spin coater</td>
			<td>Specialty Coating System</td>
			<td>&#160;P-6708</td>
			<td></td>
		</tr>
		<tr>
			<td>Scanning Electron Microscope&#160;</td>
			<td>Philips</td>
			<td>XL30CPSEM</td>
			<td></td>
		</tr>
		<tr>
			<td>Atomic Force Microscope</td>
			<td>DimensionV Nanoscope, VEECO</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>p4-GLO CYP3A4</td>
			<td>Promega</td>
			<td>V8902</td>
			<td></td>
		</tr>
		<tr>
			<td>UV bulb</td>
			<td>ESCO</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>NanoScope analysis software</td>
			<td>VEECO</td>
			<td></td>
			<td>version 1.20</td>
		</tr>
		<tr>
			<td>Fluorescence microscope</td>
			<td>Olympus</td>
			<td>TH45200</td>
			<td>Use Volocity 4 Software</td>
		</tr>
		<tr>
			<td>Tissue culture plates</td>
			<td>Corning, UK&#160;</td>
			<td>3527</td>
			<td></td>
		</tr>
		<tr>
			<td>glass slides</td>
			<td>Scientific Laboratory Supplies</td>
			<td>MIC3308</td>
			<td></td>
		</tr>
		<tr>
			<td>Diethylene glycol</td>
			<td>Sigma&#8211;Aldrich</td>
			<td>93171</td>
			<td></td>
		</tr>
		<tr>
			<td>&#160;1,6-hexanediol</td>
			<td>Sigma&#8211;Aldrich</td>
			<td>240117</td>
			<td></td>
		</tr>
		<tr>
			<td>Neopentyl glycol</td>
			<td>Sigma&#8211;Aldrich</td>
			<td>408255</td>
			<td></td>
		</tr>
		<tr>
			<td>Adipic acid</td>
			<td>Sigma&#8211;Aldrich</td>
			<td>9582</td>
			<td></td>
		</tr>
		<tr>
			<td>anhydrous N,N-Dimethylformamide</td>
			<td>Sigma&#8211;Aldrich</td>
			<td>227056</td>
			<td></td>
		</tr>
		<tr>
			<td>Diethyl ether</td>
			<td>Sigma&#8211;Aldrich</td>
			<td>676845</td>
			<td></td>
		</tr>
		<tr>
			<td>titanium (IV) butoxide&#160;</td>
			<td>Sigma&#8211;Aldrich</td>
			<td>244112</td>
			<td></td>
		</tr>
		<tr>
			<td>1,4-butanediol&#160;</td>
			<td>Sigma&#8211;Aldrich</td>
			<td>493732</td>
			<td></td>
		</tr>
		<tr>
			<td>Vacuum oven</td>
			<td>Thermoscientific</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>4,4&#8217;-Methylenebis(phenyl isocyanate)</td>
			<td>Sigma&#8211;Aldrich</td>
			<td>101688</td>
			<td></td>
		</tr>
		<tr>
			<td>Tetrahydrofurane</td>
			<td>Sigma&#8211;Aldrich</td>
			<td>401757</td>
			<td></td>
		</tr>
		<tr>
			<td>Sputter coater</td>
			<td>Bal-Tec SCD 050</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td>Inmunostaining</td>
		</tr>
		<tr>
			<td>Phosphate buffer saline (-MgCl2, -CaCl2)</td>
			<td>Gibco</td>
			<td>10010031</td>
			<td>&#160;Store at room temperature</td>
		</tr>
		<tr>
			<td>PBST, PBS made up with 0.1% TWEEN 20&#160;</td>
			<td>&#160; Scientific Laboratory Supplies Ltd</td>
			<td>EC607&#160;</td>
			<td></td>
		</tr>
		<tr>
			<td>Methanol</td>
			<td>&#160; Scientific Laboratory Supplies Ltd</td>
			<td>CHE5010</td>
			<td></td>
		</tr>
		<tr>
			<td>Bovine Serum Albumin</td>
			<td>Sigma-Aldrich, UK</td>
			<td>A7906</td>
			<td></td>
		</tr>
		<tr>
			<td>MOWIOL 488 DAPI</td>
			<td>Calbiochem</td>
			<td>475904</td>
			<td>Made up in Tris HCL and glycerol as per manufacturers instructions</td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td>Cell culture and Functional assay</td>
		</tr>
		<tr>
			<td>CYP3A activity pGLO kit</td>
			<td>Promega</td>
			<td>V8902</td>
			<td></td>
		</tr>
		<tr>
			<td>Hepatozyme</td>
			<td>Gibco</td>
			<td>17705021</td>
			<td></td>
		</tr>
		<tr>
			<td>TryLE express</td>
			<td>Life Technologies</td>
			<td><a href="http://www.lifetechnologies.com/order/catalog/product/12604013">12604013</a></td>
			<td></td>
		</tr>
	</tbody>
</table>

stabilizing hepatocellular phenotype using optimized synthetic surfaces

Currently, one of the major limitations in cell biology is maintaining differentiated cell phenotype. Biological matrices are commonly used for culturing and maintaining primary and pluripotent stem cell derived hepatocytes. While biological matrices are useful, they permit short term culture of hepatocytes, limiting their widespread application. We have attempted to overcome the limitations using a synthetic polymer coating. Polymers represent one of the broadest classes of biomaterials and possess a wide range of mechanical, physical and chemical properties, which can be fine-tuned for purpose. Importantly, such materials can be scaled to quality assured standards and display batch-to-batch consistency. This is essential if cells are to be expanded for high through-put screening in the pharmaceutical testing industry or for cellular based therapy. Polyurethanes (PUs) are one group of materials that have shown promise in cell culture. Our recent progress in optimizing a polyurethane coated surface, for long-term culture of human hepatocytes displaying stable phenotype, is presented and discussed.

Polymer solvent influences the topography of the polymer coated surface
Polyurethane 134 was solubilized in chloroform, either alone or in combination with toluene or tetrahydrofuran or dichloromethane and the glass slides spin-coated with the different formulations. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to characterize the physical properties of the polymer coatings (Figure 1). The coating obtained using toluene or chl...

Watch this Scientific Journal Video about Stabilizing Hepatocellular Phenotype Using Optimized Synthetic Surfaces at JoVE.com

Stabilizing Hepatocellular Phenotype Using Optimized Synthetic Surfaces

This article will focus on developing polymer coated surfaces for long-term, stable culture of stem cell derived human hepatocytes.

Currently, one of the major limitations in cell biology is maintaining differentiated cell phenotype. Biological matrices are commonly used for culturing ...

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JoVE Journal

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10.2K Views.  University of Edinburgh. This article will focus on developing polymer coated surfaces for long-term, stable culture of stem cell derived human hepatocytes.

Video: Stabilizing Hepatocellular Phenotype Using Optimized Synthetic Surfaces

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

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

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

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

Towards Biomimicking Wood: Fabricated Free-standing Films of Nanocellulose, Lignin, and a Synthetic Polycation

Woody materials are comprised of plant cell walls that contain a layered secondary cell wall composed of structural polymers of polysaccharides and lignin. Layer-by-layer (LbL) assembly process which relies on the assembly of oppositely charged molecules from aqueous solutions was used to build a freestanding composite film of isolated wood polymers of lignin and oxidized nanofibril cellulose (NFC). To facilitate the assembly of these negatively charged polymers, a positively charged polyelectrolyte, poly(diallyldimethylammomium chloride) (PDDA), was used as a linking layer to create this simplified model cell wall. The layered adsorption process was studied quantitatively using quartz crystal microbalance with dissipation monitoring (QCM-D) and ellipsometry. The results showed that layer mass/thickness per adsorbed layer increased as a function of total number of layers. The surface coverage of the adsorbed layers was studied with atomic force microscopy (AFM). Complete coverage of the surface with lignin in all the deposition cycles was found for the system, however, surface coverage by NFC increased with the number of layers. The adsorption process was carried out for 250 cycles (500 bilayers) on a cellulose acetate (CA) substrate. Transparent free-standing LBL assembled nanocomposite films were obtained when the CA substrate was later dissolved in acetone. Scanning electron microscopy (SEM) of the fractured cross-sections showed a lamellar structure, and the thickness per adsorption cycle (PDDA-Lignin-PDDA-NC) was estimated to be 17 nm for two different lignin types used in the study. The data indicates a film with highly controlled architecture where nanocellulose and lignin are spatially deposited on the nanoscale (a polymer-polymer nanocomposites), similar to what is observed in the native cell wall.

The objective of this research was to form synthetic plant cell wall tissue using layer-by-layer assembly of nanocellulose fibrils and isolated lignin assembled from dilute aqueous suspensions.&#160; Surface measurement techniques of quartz crystal microbalance and atomic force microscopy were used to monitor the formation of the polymer-polymer nanocomposite material.

Woody materials are comprised of plant cell walls that contain a layered secondary cell wall composed of structural polymers of polysaccharides and ...

In Situ SIMS and IR Spectroscopy of Well-defined Surfaces Prepared by Soft Landing of Mass-selected Ions

Soft landing of mass-selected ions onto surfaces is a powerful approach for the highly-controlled preparation of materials that are inaccessible using conventional synthesis techniques. Coupling soft landing with in situ characterization using secondary ion mass spectrometry (SIMS) and infrared reflection absorption spectroscopy (IRRAS) enables analysis of well-defined surfaces under clean vacuum conditions. The capabilities of three soft-landing instruments constructed in our laboratory are illustrated for the representative system of surface-bound organometallics prepared by soft landing of mass-selected ruthenium tris(bipyridine) dications, [Ru(bpy)3]2+ (bpy = bipyridine), onto carboxylic acid terminated self-assembled monolayer surfaces on gold (COOH-SAMs). In situ time-of-flight (TOF)-SIMS provides insight into the reactivity of the soft-landed ions. In addition, the kinetics of charge reduction, neutralization and desorption occurring on the COOH-SAM both during and after ion soft landing are studied using in situ Fourier transform ion cyclotron resonance (FT-ICR)-SIMS measurements. In situ IRRAS experiments provide insight into how the structure of organic ligands surrounding metal centers is perturbed through immobilization of organometallic ions on COOH-SAM surfaces by soft landing. Collectively, the three instruments provide complementary information about the chemical composition, reactivity and structure of well-defined species supported on surfaces.

In Situ SIMS and IR Spectroscopy of Well-defined Surfaces Prepared by Soft Landing of Mass-selected Ions

Soft landing of mass-selected ions onto surfaces is a powerful approach for the highly-controlled preparation of novel materials. Coupled with analysis by in situ secondary ion mass spectrometry (SIMS) and infrared reflection absorption spectroscopy (IRRAS), soft landing provides unprecedented insights into the interactions of well-defined species with surfaces.

Soft landing of mass-selected ions onto surfaces is a powerful approach for the highly-controlled preparation of materials that are inaccessible using ...

Synthetic Methodology for Asymmetric Ferrocene Derived Bio-conjugate Systems via Solid Phase Resin-based Methodology

Early detection is a key to successful treatment of most diseases, and is particularly imperative for the diagnosis and treatment of many types of cancer. The most common techniques utilized are imaging modalities such as Magnetic Resonance Imaging (MRI), Positron Emission Topography (PET), and Computed Topography (CT) and are optimal for understanding the physical structure of the disease but can only be performed once every four to six weeks due to the use of imaging agents and overall cost. With this in mind, the development of &#8220;point of care&#8221; techniques, such as biosensors, which evaluate the stage of disease and/or efficacy of treatment in the clinician&#8217;s office and do so in a timely manner, would revolutionize treatment protocols.1 As a means to exploring ferrocene based biosensors for the detection of biologically relevant molecules2, methods were developed to produce ferrocene-biotin bio-conjugates described herein. This report will focus on a biotin-ferrocene-cysteine system that can be immobilized on a gold surface.

The synthesis of asymmetric species of ferrocene is challenging using solution techniques. This report focuses on the methods carried out to produce a ferrocene-biotin bioconjugate using facile and clean reactions accomplished via solid-phase synthesis. Incorporation of a thiolate moiety is shown to impart the ability for immobilization on gold surfaces.

Early detection is a key to successful treatment of most diseases, and is particularly imperative for the diagnosis and treatment of many types of cancer. ...

Optimization of Synthetic Proteins: Identification of Interpositional Dependencies Indicating Structurally and/or Functionally Linked Residues

Protein alignments are commonly used to evaluate the similarity of protein residues, and the derived consensus sequence used for identifying functional units (e.g., domains). Traditional consensus-building models fail to account for interpositional dependencies &#8211; functionally required covariation of residues that tend to appear simultaneously throughout evolution and across the phylogentic tree. These relationships can reveal important clues about the processes of protein folding, thermostability, and the formation of functional sites, which in turn can be used to inform the engineering of synthetic proteins. Unfortunately, these relationships essentially form sub-motifs which cannot be predicted by simple &#8220;majority rule&#8221; or even HMM-based consensus models, and the result can be a biologically invalid &#8220;consensus&#8221; which is not only never seen in nature but is less viable than any extant protein. We have developed a visual analytics tool, StickWRLD, which creates an interactive 3D representation of a protein alignment and clearly displays covarying residues. The user has the ability to pan and zoom, as well as dynamically change the statistical threshold underlying the identification of covariants. StickWRLD has previously been successfully used to identify functionally-required covarying residues in proteins such as Adenylate Kinase and in DNA sequences such as endonuclease target sites.

Synthetic protein sequences based on consensus motifs typically ignore co-evolving residues, that imply interpositional dependencies (IPDs). IPDs can be essential to activity, and designs that disregard them may result in suboptimal results. This protocol uses StickWRLD to identify IPDs and help inform rational protein design, resulting in more efficient results.

Protein alignments are commonly used to evaluate the similarity of protein residues, and the derived consensus sequence used for identifying functional ...

An Optimized Protocol for the Efficient Radiolabeling of Gold Nanoparticles by Using a 125I-labeled Azide Prosthetic Group

Here, we demonstrate a detailed protocol for the radiosynthesis of a 125I-labeled azide prosthetic group and its application to the efficient radiolabeling of DBCO-group-functionalized gold nanoparticles using a copper-free click reaction. Radioiodination of the stannylated precursor (2) was carried out by using [125I]NaI and chloramine T as an oxidant at room temperature for 15 min. After HPLC purification of the crude product, the purified 125I-labeled azide (1) was obtained with high radiochemical yield (75 &plusmn; 10%, n = 8) and excellent radiochemical purity (&gt;99%). For the synthesis of radiolabeled 13-nm-sized gold nanoparticles, the DBCO-functionalized gold nanoparticles (3) were prepared by using a thiolated polyethylene glycol polymer. A copper-free click reaction between 1 and 3 gave the 125I-labeled gold nanoparticles (4) with more than 95% of radiochemical yield as determined by radio-thin-layer chromatography (radio-TLC). These results clearly indicate that the present radiolabeling method using a strain-promoted copper-free click reaction will be useful for the efficient and convenient radiolabeling of DBCO-group-containing nanomaterials.

An Optimized Protocol for the Efficient Radiolabeling of Gold Nanoparticles by Using a 125I-labeled Azide Prosthetic Group

A detailed procedure for the synthesis of a 125I-labeled azide and the radiolabeling of dibenzocyclooctyne (DBCO)-group-conjugated, 13-nm-sized gold nanoparticles using a copper-free click reaction is described.

Here, we demonstrate a detailed protocol for the radiosynthesis of a 125I-labeled azide prosthetic group and its application to the efficient ...

Color Spot Test As a Presumptive Tool for the Rapid Detection of Synthetic Cathinones

Synthetic cathinones are a large class of new psychoactive substances (NPS) that are increasingly prevalent in drug seizures made by law enforcement and other border protection agencies globally. Color testing is a presumptive identification technique indicating the presence or absence of a particular drug class using rapid and uncomplicated chemical methods. Owing to their relatively recent emergence, a color test for the specific identification of synthetic cathinones is not currently available. In this study, we introduce a protocol for the presumptive identification of synthetic cathinones, employing three aqueous reagent solutions: copper(II) nitrate, 2,9-dimethyl-1,10-phenanthroline (neocuproine) and sodium acetate. Small pin-head sized amounts (approximately 0.1-0.2 mg) of the suspected drugs are added to the wells of a porcelain spot plate, and each reagent is then added dropwise sequentially before heating on a hotplate. A color change from very light blue to yellow-orange after 10 min indicates the likely presence of synthetic cathinones. The highly stable and specific test reagent has the potential for use in the presumptive screening of unknown samples for synthetic cathinones in a forensic laboratory. However, the nuisance of an added heating step for the color change result limits the test to laboratory application and decreases the likelihood of an easy translation to field testing.

Here we present a simple, inexpensive, and selective chemical spot test protocol for the detection of synthetic cathinones, a class of new psychoactive substances. The protocol is suitable for use in various areas of law enforcement that encounter illicit material.

Synthetic cathinones are a large class of new psychoactive substances (NPS) that are increasingly prevalent in drug seizures made by law enforcement and ...

Characterization of Synthetic Polymers via Matrix Assisted Laser Desorption Ionization Time of Flight (MALDI-TOF) Mass Spectrometry

There are many techniques that can be employed in the characterization of synthetic homopolymers, but few provide as useful of information for end group analysis as matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS). This tutorial demonstrates methods for optimization of the sample preparation, spectral acquisition, and data analysis of synthetic polymers using MALDI-TOF MS. Critical parameters during sample preparation include the selection of the matrix, identification of an appropriate cationization salt, and tuning the relative proportions of the matrix, cation, and analyte. The acquisition parameters, such as mode (linear or reflector), polarization (positive or negative), acceleration voltage, and delay time, are also important. Given some knowledge of the chemistry involved to synthesize the polymer and optimizing both the data acquisition parameters and the sample preparation conditions, spectra should be obtained with sufficient resolution and mass accuracy to enable the unambiguous determination of the end groups of most homopolymers (masses below 10,000) in addition to the repeat unit mass and the overall molecular weight distribution. Though demonstrated on a limited set of polymers, these general techniques are applicable to a much wider range of synthetic polymers for determining mass distributions, though end group determination is only possible for homopolymers with narrow dispersity.

Characterization of Synthetic Polymers via Matrix Assisted Laser Desorption Ionization Time of Flight MALDI-TOF Mass Spectrometry

A protocol for the matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS) characterization of synthetic polymers is described including the optimization of sample preparation, spectral acquisition, and data analysis.

There are many techniques that can be employed in the characterization of synthetic homopolymers, but few provide as useful of information for end group ...

Light-driven Molecular Motors on Surfaces for Single Molecular Imaging

The design and synthesis of a synthetic system that aims for the direct visualization of a synthetic rotary motor at the single molecule level on surfaces are demonstrated. This work requires careful design, considerable synthetic effort, and proper analysis. The rotary motion of the molecular motor in solution is shown by 1H NMR and UV-vis absorption spectroscopy techniques. In addition, the method to graft the motor onto an amine-coated quartz is described. This method helps to gain more insight into molecular machines.

The manuscript describes how to synthesize and graft a molecular motor on surfaces for single molecular imaging.

The design and synthesis of a synthetic system that aims for the direct visualization of a synthetic rotary motor at the single molecule level on surfaces ...

A Facile Synthetic Method to Obtain Bismuth Oxyiodide Microspheres Highly Functional for the Photocatalytic Processes of Water Depuration

Bismuth oxyhalide (BiOI) is a promising material for sunlight-driven-environmental photocatalysis. Given that the physical structure of this kind of materials is highly related to its photocatalytic performance, it is necessary to standardize the synthetic methods in order to obtain the most functional architectures and, thus, the highest photocatalytic efficiency. Here, we report a reliable route to obtain BiOI microspheres via the solvothermal process, using Bi(NO3)3 and potassium iodide (KI) as precursors, and ethylene glycol as a template. The synthesis is standardized in a 150 mL autoclave, at 126 &#176;C for 18 h. This results in 2-3 &#181;m-sized mesoporous microspheres, with a relevant specific surface area (61.3 m2/g). Shortening the reaction times in the synthesis results in amorphous structures, while higher temperatures lead to a slight increase in the porosity of the microspheres, with no effect in the photocatalytic performance. The materials are photo-active under UV-A/visible light irradiation for the degradation of the antibiotic ciprofloxacin in water. This method has demonstrated to be effective in interlaboratory tests, obtaining similar BiOI microspheres in Mexican and Chilean research groups.

This article describes a synthetic method to obtain bismuth oxyiodide microspheres, which are highly functional to perform the photocatalytic removal of organic pollutants, such as ciprofloxacin, in water under UV-A/visible light irradiation.

Bismuth oxyhalide (BiOI) is a promising material for sunlight-driven-environmental photocatalysis. Given that the physical structure of this kind of ...