The authors have no acknowledgements.

CAUTION: One must keep in mind that 18F is a radioactive isotope, and therefore it is necessary to carry out all procedures behind adequate shielding. Lead shielding is appropriate for this type of radiation. Be sure to wear radiation detection badges throughout the entirety of this procedure. Additionally, immediately dispose of gloves before touching anything after the synthesis, as they may be contaminated with radioactive activity. Utilize hand-foot monitors as well as pancake Geiger counters to check for contamination of sleeves, hands, and feet.
1. Azeotropic drying of 18F-anion
NOTE: Figure 2A shows a workflow graph of this procedure, which takes ~10 min.
<ol>
	<li>Precondition a quaternary methyl ammonium (QMA) anion exchange cartridge (Table of Materials) by passing 0.5 M K2CO3 (10 mL) through the cartridge, followed by deionized water (10 mL).</li>
	<li>Pass an aqueous solution of [18F]F-/[18O]H2O (100&#8722;500 MBq) through the preconditioned QMA cartridge in reverse, using a male to male adapter. Discard the [18O]H2O. 
	NOTE: These steps can be performed using an automated synthesis module, or by using additional shielding on the syringe.</li>
	<li>Elute the first four drops of the fixed [18F]fluoride anions from the QMA cartridge into a prepared solution of [2.2.2]cryptand (Table of Materials) (10 mg), 0.2 M K2CO3 (50 &#956;L, 10 &#956;mol), and acetonitrile (1 mL) in a thick-walled v-vial, and seal the vial. 
	NOTE: Only the first four drops are used as the majority of the radioactive [18F]fluoride is eluted off the QMA in these drops. This reduces the amount of base carried forward in the [18F]fluoride stock solution, which is necessary to avoid degradation of the SiFA moiety.</li>
	<li>Seal the vial and place in a 90 &#176;C mineral oil bath positioned on a hot plate. Insert a vent needle and a needle connected to a stream of argon gas into the septum of the vial cap. Wait 5 min to evaporate the solvents under the gentle stream of argon. Remove any remaining traces of water by adding 1 mL of acetonitrile to facilitate azeotropic co-evaporation. Repeat this step 2x to ensure dryness.</li>
	<li>Once the solvent is visibly removed, stop the argon flow, and remove the syringes from the vial cap, and remove the vial from the oil bath.</li>
	<li>Resuspend the dried [18F]fluoride in the reaction solvent of choice. 
	NOTE: In this case, acetonitrile (1 mL) is added to create a stock solution of highly reactive [18F-]F- (100&#8722;500 MBq). This solution can now be used for labeling.</li>
</ol>
2. One-step SiFA-ligand labeling
NOTE: Figure 2B shows a workflow graph of this procedure, which takes ~15 min.
<ol>
	<li>Precondition a C-18 cartridge (Table of Materials) by rinsing it with ethanol (10 mL) and distilled water (10 mL).</li>
	<li>Add the [18F-]fluoride stock solution to a reaction vial containing a SiFA-labeled precursor (100 &#956;L, 20&#8722;100 nmol). Allow the labeling reaction to proceed for 5 min at room temperature without stirring the solution. 
	NOTE: The entire stock solution can be added or an aliquot, depending on how much activity is desired for the reaction.</li>
	<li>Draw up the reaction mixture in a 20 mL syringe containing 0.1 M phosphate buffer (9 mL) and pass the solution through the preconditioned C-18 cartridge to trap the labeled tracer.</li>
	<li>Wash the cartridge with distilled water (5 mL), then elute trapped tracer from the C-18 cartridge with ethanol (300 &#956;L), and dilute with sterile phosphate buffer for injection (3 mL).</li>
	<li>Pass the purified [18F]SiFA-tracer through a sterile filter. 
	NOTE: To obtain a clear PET imagine for small animal imaging, the partitioned patient dose should be between 5&#8722;8 MBq. For human use, the partitioned patient dose should be between 200&#8722;300 MBq.</li>
	<li>Inject a small aliquot (~4 MBq) of the purified [18F]SiFA-tracer onto an HPLC system equipped with a reversed-phase C-18 column to confirm that the radiochemical purity is greater than 95%.</li>
</ol>

<ol>
	<li>Wahl, R. L., Buchanan, J. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Principles and practice of positron emission tomography. , (2002).</li><li>W&#228;ngler, C., Schirrmacher, R., Bartenstein, P., W&#228;ngler, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Click-chemistry+reactions+in+radiopharmaceutical+chemistry:+Fast+&amp;+easy+introduction+of+radiolabels+into+biomolecules+for+in+vivo+imaging.">Click-chemistry reactions in radiopharmaceutical chemistry: Fast &amp; easy introduction of radiolabels into biomolecules for in vivo imaging.</a> Current Medical Chemistry. 17, 1092-1116 (2010).</li><li>Schirrmacher, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=18F-labeling+of+peptides+by+means+of+an+organosilicon-based+fluoride+acceptor.">18F-labeling of peptides by means of an organosilicon-based fluoride acceptor.</a> Angewandte Chemie International Edition. 45, 6047-6050 (2006).</li><li>Kostikov, A. P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Oxalic+acid+supported+Si-18F-radiofluorination:+One-step+radiosynthesis+of+N-succinimidyl+3-(di-tert-butyl[18F]fluorosilyl)benzoate+([18F]SiFB)+for+protein+labeling.">Oxalic acid supported Si-18F-radiofluorination: One-step radiosynthesis of N-succinimidyl 3-(di-tert-butyl[18F]fluorosilyl)benzoate ([18F]SiFB) for protein labeling.</a> Bioconjugate Chemistry. 23 (1), 106-114 (2012).</li><li>Cacace, F., Speranza, M., Wolf, A. P., Macgregor, R. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nucleophilic+aromatic+substitution;+kinetics+of+fluorine-18+substitution+reactions+in+polyfluorobenzenes.+Isotopic+exchange+between+18F-+and+polyfluorobenzenes+in+dimethylsulfoxide.+A+kinetic+study.">Nucleophilic aromatic substitution; kinetics of fluorine-18 substitution reactions in polyfluorobenzenes. Isotopic exchange between 18F- and polyfluorobenzenes in dimethylsulfoxide. A kinetic study.</a> Journal of Fluorine Chemistry. 21, 145-158 (1982).</li><li>Schirrmacher, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synthesis+of+p-(di-tert-butyl[18F]fluorosilyl)benzaldehyde+([18F]SiFA-A)+with+high+specific+activity+by+isotopic+exchange:+A+convenient+labeling+synthon+for+the+18F-labeling+of+N-amino-oxy+derivatized+peptides.">Synthesis of p-(di-tert-butyl[18F]fluorosilyl)benzaldehyde ([18F]SiFA-A) with high specific activity by isotopic exchange: A convenient labeling synthon for the 18F-labeling of N-amino-oxy derivatized peptides.</a> Bioconjugate Chemistry. 18, 2085-2089 (2007).</li><li>Kostikov, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=N-(4-(di-tert-butyl[18F]fluorosilyl)benzyl)-2-hydroxy-N,N-dimethylethylammonium+bromide+([18F]SiFAN+Br-):+A+novel+lead+compound+for+the+development+of+hydrophilic+SiFA-based+prosthetic+groups+for+18F-labeling.">N-(4-(di-tert-butyl[18F]fluorosilyl)benzyl)-2-hydroxy-N,N-dimethylethylammonium bromide ([18F]SiFAN+Br-): A novel lead compound for the development of hydrophilic SiFA-based prosthetic groups for 18F-labeling.</a> Journal of Fluorine Chemistry. 132, 27-34 (2011).</li><li>W&#228;ngler, B., 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=Kit-like+18F-labeling+of+proteins:+Synthesis+of+4-(di-tert-butyl[18F]fluorosilyl)benzenethiol+(Si[18F]FA-SH)+labeled+rat+serum+albumin+for+blood+pool+imaging+with+PET.">Kit-like 18F-labeling of proteins: Synthesis of 4-(di-tert-butyl[18F]fluorosilyl)benzenethiol (Si[18F]FA-SH) labeled rat serum albumin for blood pool imaging with PET.</a> Bioconjugate Chemistry. 20, 317-321 (2009).</li><li>Iovkova, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=para-Functionalized+aryl-di-tert-butylfluorosilanes+as+potential+labeling+synthons+for+18F+radiopharmaceuticals.">para-Functionalized aryl-di-tert-butylfluorosilanes as potential labeling synthons for 18F radiopharmaceuticals.</a> Chemistry. 15, 2140-2147 (2009).</li><li>W&#228;ngler, C., 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=One-step+18F-labeling+of+carbohydrate-conjugated+octreotate-derivatives+containing+a+silicon-fluoride-acceptor+(SiFA):+In+vitro+and+in+vivo+evaluation+as+tumor+imaging+agents+for+positron+emission+tomography+(PET).">One-step 18F-labeling of carbohydrate-conjugated octreotate-derivatives containing a silicon-fluoride-acceptor (SiFA): In vitro and in vivo evaluation as tumor imaging agents for positron emission tomography (PET).</a> Bioconjugate Chemistry. 21, 2289-2296 (2010).</li><li>Ilhan, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=First-in-human+18F-SiFAlin-TATE+PET/CT+for+NET+imaging+and+theranostics.">First-in-human 18F-SiFAlin-TATE PET/CT for NET imaging and theranostics.</a> European Journal of Nuclear Medicine and Molecular Imaging. 46, 2400-2401 (2019).</li></ol>

The authors have nothing to disclose.

SiFA labeling chemistry represents one of the first 18F-labeling methods employing an extraordinarily efficient isotopic exchange reaction that can be performed at room temperature. A typical radiochemical reaction relies on the formation of a carbon-fluorine bond via reaction of [18F]fluoride with a fluoride-reactive functionality through an elimination or substitution pathway. These reaction conditions are often harsh, performed at extreme pH or high temperature, and are laden with byproducts or r...

Fluorine-18 (109-minute half-life, 97% positron emission) is among the most important radionuclides for positron emission tomography (PET), a noninvasive imaging method that visualizes and quantifies the bio-distribution of radiolabeled tracers for various diseases1. Peptides and proteins are especially difficult to label with [18F]fluoride because they require building blocks formed by multi-step syntheses2. To reduce the complexity of 18F-radiolabeling, silicon-fluoride acceptor (SiFA) was recently introduced as reliable tools3. The SiFA group consists of a central silicon atom connected to two tertiary butyl groups, a derivatized phenyl moiety, and a non-radioactive fluorine atom. The tertiary butyl groups impart hydrolytic stability to the silicon-fluoride bond, which is a critical feature for in vivo applications of SiFA conjugates as imaging agents.
When attached to a small molecule or biomolecule, the SiFA building blocks bind radioactive [18F]fluoride anions by exchanging fluorine-19 for fluorine-18 at nanomolar concentrations without forming significant amounts of radioactive side products4. Moreover, a high radiochemical yield is quickly achieved by labeling the SiFA moiety in dipolar aprotic solvents at low temperatures. This is in stark contrast to classical isotopic exchange reactions, which produce radiotracers of low specific activity5. In these cases, large amounts of precursor (in the range of milligrams) must be used to obtain reasonable incorporation of [18F]fluoride. Isotopic exchange reactions using SiFAs are far more efficient, as confirmed by kinetic studies and density functional theory calculations6,7. Labeled SiFAs are easily purified by solid-phase extraction since both the labeled and unlabeled SiFA compounds are chemically identical. This differs from traditional radiolabeled tracers, where the precursor molecule and the labeled product are two different chemical species and must be separated after radiolabeling by high-performance liquid chromatography (HPLC). Using SiFA building blocks, small-molecules, proteins, and peptides can be successfully labeled with [18F]fluoride by one- and two-step labeling protocols devoid of complicated purification procedures (Figure 1)4,8,9. Moreover, some SiFA-labeled compounds are reliable in vivo imaging agents for blood flow and tumors10. The simplicity of SiFA chemistry enables even untrained investigators to use [18F]fluoride for radiotracer synthesis and development.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>[18F]F-/H2[18O]O</td>
			<td>(Cyclotron produced)</td>
			<td>-</td>
			<td>-</td>
		</tr>
		<tr>
			<td>[2.2.2]Cryptand</td>
			<td>Aldrich</td>
			<td>291110</td>
			<td>Kryptofix 2.2.2</td>
		</tr>
		<tr>
			<td>Acetonitrile anhydrous</td>
			<td>Aldrich</td>
			<td>271004</td>
			<td>-</td>
		</tr>
		<tr>
			<td>Deionized water</td>
			<td>Baxter</td>
			<td>JF7623</td>
			<td>-</td>
		</tr>
		<tr>
			<td>Ethanol, anhydrous</td>
			<td>Commercial Alcohols</td>
			<td></td>
			<td>-</td>
		</tr>
		<tr>
			<td>Potassium carbonate</td>
			<td>Aldrich</td>
			<td>209619</td>
			<td>-</td>
		</tr>
		<tr>
			<td>QMA cartridge</td>
			<td>Waters</td>
			<td>186004540</td>
			<td>QMA SepPak Light (46 mg) cartridge</td>
		</tr>
		<tr>
			<td>Equipment</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>C-18 cartridge</td>
			<td>Waters</td>
			<td>WAT023501</td>
			<td>C-18 SepPak Light cartridge</td>
		</tr>
		<tr>
			<td>C18 column</td>
			<td>Phenomenex</td>
			<td>00G-4041-N0</td>
			<td>HPLC Luna C18 250 x 10 mm, 5 &#181;m</td>
		</tr>
		<tr>
			<td>HPLC</td>
			<td>Agilent Technologies</td>
			<td>-</td>
			<td>HPLC 1200 series</td>
		</tr>
		<tr>
			<td>micro-PET Scanner</td>
			<td>Siemens</td>
			<td>-</td>
			<td>micro-PET R4 Scanner</td>
		</tr>
		<tr>
			<td>Radio-TLC plate reader</td>
			<td>Raytest</td>
			<td>-</td>
			<td>Radio-TLC Mini Gita</td>
		</tr>
		<tr>
			<td>Sterile filter 0.22&#181;m</td>
			<td>Millipore</td>
			<td>SLGP033RS</td>
			<td>-</td>
		</tr>
	</tbody>
</table>

18f-labeling of radiotracers functionalized with a silicon fluoride acceptor (sifa) for positron emission tomography

The para-substituted di-tert-butylfluorosilylbenzene structural motif known as the silicon-fluoride acceptor (SiFA) is a useful tag in the radiochemist&#39;s toolkit for incorporating radioactive [18F]fluoride into tracers for use in positron emission tomography. In comparison to conventional radiolabeling strategies, isotopic exchange of fluorine-19 from SiFA with [18F]fluoride is carried out at room temperature and requires minimal reaction participants. The formation of by-products is thus negligible, and purification is greatly simplified. However, while the precursor molecule used for labeling and the final radiolabeled product are isotopically discrete, they are chemically identical and are thus inseparable during purification procedures. The SiFA tag is also susceptible to degradation under the basic conditions arising from the processing and drying of [18F]fluoride. The &#39;4 drop method&#39;, wherein only the first 4 drops of eluted [18F]fluoride are used from the solid-phase extraction, reduces the amount of base in the reaction, facilitates lower molar amounts of precursor, and reduces degradation.

The simplistic SiFA isotopic exchange can achieve high a degree of radiochemical incorporation of [18F]fluoride (60&#8722;90%) with a minimum amount of synthetic complexity (Figure 1). Most molecules can be radiolabeled with [18F]fluoride in one step without involving HPLC for purification (Figure 2). Radio-HPLC can be used for quality control purposes, wherein the ultraviolet (UV) absorbance peak of the final product should coincide with i...

Watch this Scientific Journal Video about 18F-Labeling of Radiotracers Functionalized with a Silicon Fluoride Acceptor SiFA for Positron Emission Tomography at JoVE.com

18F-Labeling of Radiotracers Functionalized with a Silicon Fluoride Acceptor SiFA for Positron Emission Tomography

The synthesis of fluorine-18 (18F) labeled radiopharmaceuticals for positron emission tomography typically requires months of experience. When incorporated into a radiotracer, the silicon-fluoride acceptor (SiFA) motif enables a simple 18F-labeling protocol that is independent of costly equipment and preparatory training, while reducing precursor quantity needed and utilizing milder reaction conditions.

18F-Labeling of Radiotracers Functionalized with a Silicon Fluoride Acceptor (SiFA) for Positron Emission Tomography

The para-substituted di-tert-butylfluorosilylbenzene structural motif known as the silicon-fluoride acceptor (SiFA) is a useful tag in the ...

18f-labeling-radiotracers-functionalized-with-silicon-fluoride

Research

JoVE Journal

Chemistry

7.3K Views.  University of Alberta. The synthesis of fluorine-18 (18F) labeled radiopharmaceuticals for positron emission tomography typically requires months of experience. When incorporated into a radiotracer, the silicon-fluoride acceptor (SiFA) motif enables a simple 18F-labeling protocol that is independent of costly equipment and preparatory training, while reducing precursor quantity needed and utilizing milder reaction conditions.

Video: 18F-Labeling of Radiotracers Functionalized with a Silicon Fluoride Acceptor SiFA for Positron Emission Tomography

Microwave-assisted Intramolecular Dehydrogenative Diels-Alder Reactions for the Synthesis of Functionalized Naphthalenes/Solvatochromic Dyes

Functionalized naphthalenes have applications in a variety of research fields ranging from the synthesis of natural or biologically active molecules to the preparation of new organic dyes. Although numerous strategies have been reported to access naphthalene scaffolds, many procedures still present limitations in terms of incorporating functionality, which in turn narrows the range of available substrates. The development of versatile methods for direct access to substituted naphthalenes is therefore highly desirable.
The Diels-Alder (DA) cycloaddition reaction is a powerful and attractive method for the formation of saturated and unsaturated ring systems from readily available starting materials. A new microwave-assisted intramolecular dehydrogenative DA reaction of styrenyl derivatives described herein generates a variety of functionalized cyclopenta[b]naphthalenes that could not be prepared using existing synthetic methods. When compared to conventional heating, microwave irradiation accelerates reaction rates, enhances yields, and limits the formation of undesired byproducts.
The utility of this protocol is further demonstrated by the conversion of a DA cycloadduct into a novel solvatochromic fluorescent dye via a Buchwald-Hartwig palladium-catalyzed cross-coupling reaction. Fluorescence spectroscopy, as an informative and sensitive analytical technique, plays a key role in research fields including environmental science, medicine, pharmacology, and cellular biology. Access to a variety of new organic fluorophores provided by the microwave-assisted dehydrogenative DA reaction allows for further advancement in these fields.

Microwave-assisted intramolecular dehydrogenative Diels-Alder (DA) reactions provide concise access to functionalized cyclopenta[b]naphthalene building blocks. The utility of this methodology is demonstrated by one-step conversion of the dehydrogenative DA cycloadducts into novel solvatochromic fluorescent dyes via Buchwald-Hartwig palladium-catalyzed cross-coupling reactions.

Functionalized naphthalenes have applications in a variety of research fields ranging from the synthesis of natural or biologically active molecules to ...

Synthesis and Characterization of Functionalized Metal-organic Frameworks

Metal-organic frameworks have attracted extraordinary amounts of research attention, as they are attractive candidates for numerous industrial and technological applications. Their signature property is their ultrahigh porosity, which however imparts a series of challenges when it comes to both constructing them and working with them. Securing desired MOF chemical and physical functionality by linker/node assembly into a highly porous framework of choice can pose difficulties, as less porous and more thermodynamically stable congeners (e.g., other crystalline polymorphs, catenated analogues) are often preferentially obtained by conventional synthesis methods. Once the desired product is obtained, its characterization often requires specialized techniques that address complications potentially arising from, for example, guest-molecule loss or preferential orientation of microcrystallites. Finally, accessing the large voids inside the MOFs for use in applications that involve gases can be problematic, as frameworks may be subject to collapse during removal of solvent molecules (remnants of solvothermal synthesis). In this paper, we describe synthesis and characterization methods routinely utilized in our lab either to solve or circumvent these issues. The methods include solvent-assisted linker exchange, powder X-ray diffraction in capillaries, and materials activation (cavity evacuation) by supercritical CO2 drying. Finally, we provide a protocol for determining a suitable pressure region for applying the Brunauer-Emmett-Teller analysis to nitrogen isotherms, so as to estimate surface area of MOFs with good accuracy.

Synthesis, activation, and characterization of intentionally designed metal-organic framework materials is challenging, especially when building blocks are incompatible or unwanted polymorphs are thermodynamically favored over desired forms. We describe how applications of solvent-assisted linker exchange, powder X-ray diffraction in capillaries and activation via supercritical CO2 drying, can address some of these challenges.

Metal-organic frameworks have attracted extraordinary amounts of research attention, as they are attractive candidates for numerous industrial and ...

Preparation of Mica and Silicon Substrates for DNA Origami Analysis and Experimentation

The designed nature and controlled, one-pot synthesis of DNA origami provides exciting opportunities in many fields, particularly nanoelectronics. Many of these applications require interaction with and adhesion of DNA nanostructures to a substrate. Due to its atomically flat and easily cleaned nature, mica has been the substrate of choice for DNA origami experiments. However, the practical applications of mica are relatively limited compared to those of semiconductor substrates. For this reason, a straightforward, stable, and repeatable process for DNA origami adhesion on derivatized silicon oxide is presented here. To promote the adhesion of DNA nanostructures to silicon oxide surface, a self-assembled monolayer of 3-aminopropyltriethoxysilane (APTES) is deposited from an aqueous solution that is compatible with many photoresists. The substrate must be cleaned of all organic and metal contaminants using Radio Corporation of America (RCA) cleaning processes and the native oxide layer must be etched to ensure a flat, functionalizable surface. Cleanrooms are equipped with facilities for silicon cleaning, however many components of DNA origami buffers and solutions are often not allowed in them due to contamination concerns. This manuscript describes the set-up and protocol for in-lab, small-scale silicon cleaning for researchers who do not have access to a cleanroom or would like to incorporate processes that could cause contamination of a cleanroom CMOS clean bench. Additionally, variables for regulating coverage are discussed and how to recognize and avoid common sample preparation problems is described.

Reproducible cleaning processes for substrates used in DNA origami research are described, including bench-top RCA cleaning and derivatization of silicon oxide. Protocols for surface preparation, DNA origami deposition, drying parameters, and simple experimental set-ups are illustrated.

The designed nature and controlled, one-pot synthesis of DNA origami provides exciting opportunities in many fields, particularly nanoelectronics. Many of ...

Atom Transfer Radical Polymerization of Functionalized Vinyl Monomers Using Perylene as a Visible Light Photocatalyst

A standardized technique for atom transfer radical polymerization of vinyl monomers using perylene as a visible-light photocatalyst is presented. The procedure is performed under an inert atmosphere using air- and water-exclusion techniques. The outcome of the polymerization is affected by the ratios of monomer, initiator, and catalyst used as well as the reaction concentration, solvent, and nature of the light source. Temporal control over the polymerization can be exercised by turning the visible light source off and on. Low dispersities of the resultant polymers as well as the ability to chain-extend to form block copolymers suggest control over the polymerization, while chain end-group analysis provides evidence supporting an atom-transfer radical polymerization mechanism.

A method for the atom transfer radical polymerization of functionalized vinyl monomers using perylene as a visible-light photocatalyst is described.

A standardized technique for atom transfer radical polymerization of vinyl monomers using perylene as a visible-light photocatalyst is presented. The ...

Preparation of a Corannulene-functionalized Hexahelicene by Copper(I)-catalyzed Alkyne-azide Cycloaddition of Nonplanar Polyaromatic Units

The main purpose of this video is to show 6 reaction steps of a convergent synthesis and prepare a complex molecule containing up to three nonplanar polyaromatic units, which are two corannulene moieties and a racemic hexahelicene linking them. The compound described in this work is a good host for fullerenes. Several common organic reactions, such as free-radical reactions, C-C coupling or click chemistry, are employed demonstrating the versatility of functionalization that this compound can accept. All of these reactions work for planar aromatic molecules. With subtle modifications, it is possible to achieve similar results for nonplanar polyaromatic compounds.

Preparation of a Corannulene-functionalized Hexahelicene by CopperI-catalyzed Alkyne-azide Cycloaddition of Nonplanar Polyaromatic Units

Here, we present a protocol to synthesize a complex organic compound comprised of three nonplanar polyaromatic units, assembled easily with reasonable yields.

The main purpose of this video is to show 6 reaction steps of a convergent synthesis and prepare a complex molecule containing up to three nonplanar ...

Automation of a Positron-emission Tomography (PET) Radiotracer Synthesis Protocol for Clinical Production

The development of new positron-emission tomography (PET) tracers is enabling researchers and clinicians to image an increasingly wide array of biological targets and processes. However, the increasing number of different tracers creates challenges for their production at radiopharmacies. While historically it has been practical to dedicate a custom-configured radiosynthesizer and hot cell for the repeated production of each individual tracer, it is becoming necessary to change this workflow. Recent commercial radiosynthesizers based on disposable cassettes/kits for each tracer simplify the production of multiple tracers with one set of equipment by eliminating the need for custom tracer-specific modifications. Furthermore, some of these radiosynthesizers enable the operator to develop and optimize their own synthesis protocols in addition to purchasing commercially-available kits. In this protocol, we describe the general procedure for how the manual synthesis of a new PET tracer can be automated on one of these radiosynthesizers and validated for the production of clinical-grade tracers. As an example, we use the ELIXYS radiosynthesizer, a flexible cassette-based radiochemistry tool that can support both PET tracer development efforts, as well as routine clinical probe manufacturing on the same system, to produce [18F]Clofarabine ([18F]CFA), a PET tracer to measure in vivo deoxycytidine kinase (dCK) enzyme activity. Translating a manual synthesis involves breaking down the synthetic protocol into basic radiochemistry processes that are then translated into intuitive chemistry &#34;unit operations&#34; supported by the synthesizer software. These operations can then rapidly be converted into an automated synthesis program by assembling them using the drag-and-drop interface. After basic testing, the synthesis and purification procedure may require optimization to achieve the desired yield and purity. Once the desired performance is achieved, a validation of the synthesis is carried out to determine its suitability for the production of the radiotracer for clinical use.

Automation of a Positron-emission Tomography PET Radiotracer Synthesis Protocol for Clinical Production

Positron-emission tomography (PET) imaging sites that are involved in multiple early clinical research trials need robust and versatile radiotracer manufacturing capabilities. Using the radiotracer [18F]Clofarabine as an example, we illustrate how to automate the synthesis of a radiotracer using a flexible, cassette-based radiosynthesizer and validate the synthesis for clinical use.

The development of new positron-emission tomography (PET) tracers is enabling researchers and clinicians to image an increasingly wide array of biological ...

Methionine Functionalized Biocompatible Block Copolymers for Targeted Plasmid DNA Delivery

Reversible addition-fragmentation chain transfer (RAFT) polymerization integrates the advantages of radical polymerization and living polymerization. This work presents the preparation of methionine functionalized biocompatible block copolymers via RAFT polymerization. Firstly, N,N-bis(2-hydroxyethyl)methacrylamide-b-N-(3-aminopropyl)methacrylamide (BNHEMA-b-APMA, BA) was synthesized via RAFT polymerization using 4,4&#8217;-azobis(4-cyanovaleric acid) (ACVA) as an initiating agent and 4-cyanopentanoic acid dithiobenzoate (CTP) as the chain transfer agent. Subsequently, N,N-bis(2-hydroxyethyl)methacrylamide-b-N-(3-guanidinopropyl)methacrylamide (methionine grafted BNHEMA-b-GPMA, mBG) was prepared by modifying amine groups in APMA with methionine and guanidine groups. Three kinds of block polymers, mBG1, mBG2, and mBG3, were synthesized for comparison. A ninhydrin reaction was used to quantify the APMA content; mBG1, mBG2, and mBG3 had 21%, 37%, and 52% of APMA, respectively. Gel permeation chromatography (GPC) results showed that BA copolymers possess molecular weights of 16,200 (BA1), 20,900(BA2), and 27,200(BA3) g/mol. The plasmid DNA (pDNA) complexing ability of the obtained block copolymer gene carriers was also investigated. The charge ratios (N/P) were 8, 16, and 4 when pDNA was complexed completely with mBG1, mBG2, mBG3, respectively. When the N/P ratio of mBG/pDNA polyplexes was higher than 1, the Zeta potential of mBG was positive. At an N/P ratio between 16 and 32, the average particle size of mBG/pDNA polyplexes was between 100-200 nm. Overall, this work illustrates a simple and convenient protocol for the block copolymer carrier synthesis.

This work presents the preparation of methionine functionalized biocompatible block copolymers (mBG) via the reversible addition-fragmentation chain transfer (RAFT) method. The plasmid DNA complexing ability of the obtained mBG and their transfection efficiency were also investigated. The RAFT method is very beneficial for polymerizing monomers containing special functional groups.

Reversible addition-fragmentation chain transfer (RAFT) polymerization integrates the advantages of radical polymerization and living polymerization. This ...

Preparation of Poly(pentafluorophenyl acrylate) Functionalized SiO2 Beads for Protein Purification

We demonstrate a simple method to prepare poly(pentafluorophenyl acrylate) (poly(PFPA)) grafted silica beads for antibody immobilization and subsequent immunoprecipitation (IP) application. The poly(PFPA) grafted surface is prepared via a simple two-step process. In the first step, 3-aminopropyltrimethoxysilane (APTMS) is deposited as a linker molecule onto the silica surface. In the second step, poly(PFPA) homopolymer, synthesized via the reversible addition and fragmentation chain transfer (RAFT) polymerization, is grafted to the linker molecule through the exchange reaction between the pentafluorophenyl (PFP) units on the polymer and the amine groups on APTMS. The deposition of APTMS and poly(PFPA) on the silica particles are confirmed by X-ray photoelectron spectroscopy (XPS), as well as monitored by the particle size change measured via dynamic light scattering (DLS). To improve the surface hydrophilicity of the beads, partial substitution of poly(PFPA) with amine-functionalized poly(ethylene glycol) (amino-PEG) is also performed. The PEG-substituted poly(PFPA) grafted silica beads are then immobilized with antibodies for IP application. For demonstration, an antibody against protein kinase RNA-activated (PKR) is employed, and IP efficiency is determined by Western blotting. The analysis results show that the antibody immobilized beads can indeed be used to enrich PKR while non-specific protein interactions are minimal.

Preparation of Polypentafluorophenyl acrylate Functionalized SiO2 Beads for Protein Purification

A protocol for the preparation of poly(pentafluorophenyl acrylate) (poly(PFPA)) grafted silica beads is presented. The poly(PFPA) functionalized surface is then immobilized with antibodies and used successfully for the protein separation through immunoprecipitation.

We demonstrate a simple method to prepare poly(pentafluorophenyl acrylate) (poly(PFPA)) grafted silica beads for antibody immobilization and subsequent ...

Growth of Gold Dendritic Nanoforests on Titanium Nitride-coated Silicon Substrates

In this study, a high-power impulse magnetron sputtering system is used to coat a flat and firm titanium nitride (TiN) film on silicon (Si) wafers, and a fluoride-assisted galvanic replacement reaction (FAGRR) is employed for the rapid and easy deposition of gold dendritic nanoforests (Au DNFs) on the TiN/Si substrates. Scanning electron microscopy (SEM) images and energy-dispersive X-ray spectroscopy patterns of TiN/Si and Au DNFs/TiN/Si samples validate that the synthesis process is accurately controlled. Under the reaction conditions in this study, the thickness of the Au DNFs increases linearly to 5.10 &#177; 0.20 &#181;m within 15 min of the reaction. Therefore, the employed synthesis procedure is a simple and rapid approach for preparing Au DNFs/TiN/Si composites.

This study presents a feasible procedure for synthesizing gold dendritic nanoforests on titanium nitride/silicon substrates. The thickness of gold dendritic nanoforests increases linearly within 15 min of a synthesis reaction.

In this study, a high-power impulse magnetron sputtering system is used to coat a flat and firm titanium nitride (TiN) film on silicon (Si) wafers, and a ...

Efficient Synthesis of All-Carbon Quaternary Centers via the Conjugate Addition of Functionalized Monoorganozinc Bromides

The conjugate addition of organometallic reagents to &#945;,&#946;-unsaturated carbonyls represents an important method to generate C&#8211;C bonds in the preparation of all-carbon quaternary centers. Though conjugate additions of organometallic reagents are typically performed utilizing highly reactive organolithium or Grignard reagents, organozinc reagents have garnered attention for their enhanced chemoselectivity and mild reactivity. Despite numerous recent advances with more reactive diorganozinc and mixed diorganozinc reagents, the generation of all-carbon quaternary centers via the conjugate addition of functionalized monoorganozinc reagents remains a challenge. This protocol details a convenient and mild &#8220;one-pot&#8221; preparation and copper mediated conjugate addition of functionalized monoorganozinc bromides to cyclic &#945;,&#946;-unsaturated carbonyls to afford a broad scope of all-carbon quaternary centers in generally excellent yield and diastereoselectivity. Key to the development of this technology is the utilization of DMA as a reaction solvent with TMSCl as a Lewis acid. Notable advantages to this methodology include the operational simplicity of the organozinc reagent preparation afforded by the utilization of DMA as a solvent, as well as an efficient conjugate addition mediated by various Cu(I) and Cu(II) salts. Moreover, an intermediate silyl enol ether can be isolated utilizing a modified workup procedure. The substrate scope is limited to cyclic unsaturated ketones, and the conjugate addition is impeded by stabilized (e.g., allyl, enolate, homoenolate) and sterically encumbered (e.g., neopentyl, o-aryl) monoorganozinc reagents. Conjugate additions to five- and seven-membered rings were effective, albeit in lower yields compared with six-membered ring substrates.

A simple and practical protocol for the efficient conjugate addition of functionalized monoorganozinc bromides to cyclic &#945;,&#946;-unsaturated carbonyls to furnish all-carbon quaternary centers was developed.

The conjugate addition of organometallic reagents to &#945;,&#946;-unsaturated carbonyls represents an important method to generate C&#8211;C bonds in the ...