Wednesday, December 5, 2012

Multifunctional Non-Viral Delivery Systems Based on Conjugated Polymers

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This review covers recent developments of a few potential biomedical applications conjugated polymers (CPs). CPs have a variety of properties that lend themselves to non-viral delivery systems of SiRNA, DNA plasmids and proteins. Cationic conjugated polymers are generally used to form nanoparticles with negatively charged biomolecules through electrostatic interactions. These nanoparticles have enhanced cell permeability and are easily monitored by fluorescence microscopy. 

 Some examples of CPs that are discussed in this review: poly(fluorene-co-phenylene) (PFP), poly(p-phenylenevinylene) (PPV), poly(p-phenyleneethynylene) (PPE), polydiacetylene (PDA), and polythiophene (PT)

Hydrophobic Interaction-Mediated Capture and Release of Cancer Cells on Thermoresponsive Nanostructured Surfaces

Advanced Materials

Hongliang Liu1,Xueli Liu1,2,Jingxin Meng1,Pengchao Zhang1,2,Gao Yang2,Bin Su1,Kang Sun1,Li Chen1,Dong Han3,Shutao Wang1,*,Lei Jiang

Capture and release of cancer cells: A thermoresponsive nanostructured surface has been designed to reversibly capture and release cancer cells, wherein hydrophobic interaction helps the realization of target capture/release of cancer cells. The unique nature of our designed platform is based on the synergistic effect of hydrophobic interactions between the smart surface and the hydrophobic anchor (i.e., biotin-BSA), and topographic interactions between the nanostructured substrates and cancer cells. 
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Closing The Skills Gap

Linda Wang, C&EN 2012 Volume 90 Issue 24 | pp. 49-51
This C&EN article discusses the "skills gap" between academic and industrial jobs and what PhD programs could be doing to better prepare their students for jobs in industry. Despite the large amount of stellar PhDs being churned out by top programs throughout the country, many employers in industry are still having a hard time finding applicants with the skills they deem key to success in industrial jobs. The article cites a few programs that incorporate short-term internships into their programs, but acknowledges that internships are not an option for most PhD candidates. In the end, they comment on the responsibility of students to focus on their professional development and to "do their homework" as far as what is required to obtain a position in industry. 

Functionalized Cyclopropenes As Bioorthogonal Chemical Reporters

Another example of tetrazine ligation using cyclopropenes. 

Uniform Polypyrrole Nanoparticles with High Photothermal Conversion Efficiency for Photothermal Ablation of Cancer Cells

Advanced Materials

Zhengbao Zha,Xiuli Yue,Qiushi Ren,Zhifei Dai

Uniform polypyrrole (PPy) nanoparticles were fabricated from a facile one-step aqueous dispersion polymerization. Owing to their high photothermal conversion efficiency and photostability compared with the well-known Au nanorods, as well as their good colloidal stability and biocompatibility, the resulting PPy nanoparticles could be used as a novel promising photothermal ablation coupling agent for targeted treatment of cancer.

Au nanorods have low photostability since their NIR absorbance peak would diminish after a long period of laser irradiation due to the “melting effect”; whereas other inorganic nanomaterials, such as carbon nanomaterials,and copper sulfide nanoparticles, which have also been shown to generate sufficient photothermal heating by NIR light illumination to destroy cancer cells, are non-biodegradable and usually  remain in the body for long periods of time.

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The PEG-Fluorochrome Shielding Approach for Targeted Probe Design

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This somewhat clunky paper outlines the synthesis of a multifunctional pegylated small molecule for use in vivo imaging. The multifunctional fluorochromes feature a long peg chain, DOTA ligands and an integrin binding peptide. They discuss the values of pegylation- an increased quantum yield, decreased interactions and nonspecific binding. Their mouse imaging studies show a localized signal versus an un-pegylated control. These are interesting because they look similar to macromonomers in our arsenal.

Load-Controlled Roll Transfer of Oxide Transistors for Stretchable Electronics

This MatSci paper reports on a method of fabricating stretchable transistors using a steam-rolling machine of their own design to mount molten PDMS onto a flexible substrate. They test the stretchability and conductivity before and after transfer showing that the properties do not change significantly.

Recent Developments in Enantioselective Metal-Catalyzed Domino Reactions

A long winded review of various catalyzed "Domino" or multi-component reactions. (Really long winded: their list of abbreviations is a page long.) It's worth a look-though for the diverse sampling of interesting cross coupling reactions. A representative example involves an asymmetric aldol condensation-cyclization to yield enriched oxazolines. Cobalt, coordinated to a chiral ligand, gets extra assistance from a chiral thiourea to facilitate ordered coordination and cyclization of a racemic nitrile substrate. 

Bioorthogonal Copper-Free Click Chemistry In Vivo for Tumor- Targeted Delivery of Nanoparticles

Heebeom Koo, Sangmin Lee, Jin Hee Na, Sun Hwa Kim, Sei Kwang Hahn, Kuiwon Choi,
Ick Chan Kwon, Seo Young Jeong, and Kwangmeyung Kim

N-azidoacetyl-D-mannosamine was injected into tumor cells, then PEGylated liposomes with dibenzyl cyclooctyne groups were intraveneously injected to bind to the unnatural sialic acid molecules incorporated within the surface of tumor cells. They tested their system in cells and showed that the liposomes were taken up intracellularly, and also tested and verified liposome uptake in tumor-bearing mice.

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DNA Self-Assembly of Targeted Near-Infrared-Responsive Gold Nanoparticles for Cancer Thermo-Chemotherapy

Zeyu Xiao, Changwei Ji, Jinjun Shi, Eric M. Pridgen, Jillian Frieder, Jun Wu, and
Omid C. Farokhzad

Gold nanoparticles were conjugated with PEG and DNA. The DNA consisted of CG base pairs for doxorubicin loading with one strand terminated with thiols for binding to gold and the complementary strand was functionalized with a ligand (folic acid) to target specific cells. DOX can intercalate within CG base pairs, upon which its fluorescence is quenched, so drug loading can be monitored through fluorescence. With near-IR radiation the gold heats up and denatures the DNA, which releases DOX. This system was also tested in mouse models.

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Digital photography for the analysis of fluorescence responses

himon Schwaebel, Oliver Trapp and Uwe H. F. Bunz

 The color change in pyridine substituted cruciform fluorophores (XF) in the presence of different carboxylci acids was evaluated using digital photography to address whether extraction of color from digital photography was a suitable, reproducible equivalent to spectrometers in obtaining quantitative information. Errors in reproducibility in pictures of fluorescent samples can arise from the excitation lamp used, sample positioning, exposure time, and white balance. The authors suggested taking the RGD values from a photograph and converting them into CIE LUV standardized color space, which does not contain brightness information.  One strong recommendation was to use a fixed white blance and slightly underexpose the fluorescent sample. 

Graphical abstract: Digital photography for the analysis of fluorescence responses

Engineering of Complex Order and the Macroscopic Deformation of Liquid Crystal Polymer Networks

Angewandte Chemie International Edition
  1. Laurens T. de Haan,
  2. Dr. Carlos Sánchez-Somolinos,
  3. Dr. Cees M. W. Bastiaansen,
  4. Dr. Albertus P. H. J. Schenning*,
  5. Prof. Dr. Dirk J. Broer*

Complex-structured freestanding polymer films with molecular order in three dimensions were prepared through photoalignment of polymerizable liquid crystals. The resulting films deform into cone and saddle shapes upon heating.

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Chemoselective Cross-Coupling Reactions with Differentiation between Two Nucleophilic Sites on a Single Aromatic Substrate

Julian Linshoeft, Annika C. J. Heinrich, Stephan A. W. Segler, Paul J. Gates,† and Anne Staubitz*

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The stannyl-boronate above can be made easily from the corresponding bis-stannane by transmetallation with MeLi and quenching with a boronate reagent.  The reactions could be one-pot but have to be sequential.

Functional Graphenic Materials Via a Johnson−Claisen Rearrangement

In spirit of one of Jeremiah's "favorites": 

Graphene oxide (GO) is modified using the Johnson-Claisen rearrangement, an improvement over the group's previously reported GO functionalization methods. By utilizing triethyl orthoacetate (TEOA) as reagent and solvent, the rearrangement installs carbon bonded reactive ester functionalities that are not affected by further reduction of the GO to its more conductive counterpart, Graphene. The ester-functionalized GO was then reduced using sodium borohydride. After reduction, treatment with oxalyl chloride and subsequent reaction with various amines creates amide functionalized graphenes with various properties. By installing propargyl groups, they make a "clickable" graphene surface. Furthermore, by using a sulfonated azide tag, they are able to assess the degree of functionalization by XPS. In an alternate demonstration of the use of their method, they synthesize cationic and anionic graphene derivatives and assemble them in a layer by layer fashion to create graphene sheets up to 12 layers thick.

High Aspect Ratio Sub-15 nm Silicon Trenches From Block Copolymer Templates

Adv. Mater.

Xiaodan Gu , Zuwei Liu , Ilja Gunkel , S. T. Chourou , Sung Woo Hong ,
Deirdre L. Olynick , * and Thomas P. Russell * 

High-aspect-ratio sub-15-nm silicon trenches are fabricated directly from plasma etching of a block copolymer mask. A novel method that combines a block copolymer reconstruction process and reactive ion etching is used to make the polymer mask. Silicon trenches are characterized by various methods and used as a master for subsequent imprinting of different materials. Silicon nanoholes are generated from a block copolymer with cylindrical microdomains oriented normal to the surface.

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Covalent Functionalization of Graphene with Reactive Intermediates

Acc. Chem. Res.

Department of Chemistry, University of Massachusetts Lowell, 1 University Avenue, Lowell, Massachusetts

Free radical additions are among the most common reaction, and these radicals can be generated from diazonium salts and benzoyl peroxide. Electron transfer from graphene to aryl diazonium ion or photoactivation of benzoyl peroxide yields aryl radicals that subsequently add to graphene to form covalent adducts. Nitrenes, electron-deficient species generated by thermal or photochemical activation of organic azides, can functionalize graphene very efficiently. Because perfluorophenyl nitrenes show enhanced bimolecular reactions compared with alkyl or phenyl nitrenes, perfluorophenyl azides are especially effective. Carbenes are used less frequently than nitrenes, but they undergo CH insertion and CdC cycloaddition reactions with graphene. In addition, arynes can serve as a dienophile in a Diels Alder type reaction with graphene. 
Further study is needed to understand and exploit the chemistry of graphene. The generation of highly reactive intermediates in these reactions leads to side products that complicate the product composition and analysis. Fundamental questions remain about the reactivity and regioselectivity of graphene. The differences in the basal plane and the undercoordinated edges of graphene and the zigzag versus arm-chair configurations warrant comprehensive studies. The availability of well-defined pristine graphene starting materials in large quantities remains a key obstacle to the advancement of synthetic graphene chemistry .


Photoselective Delivery of Model Therapeutics from Hydrogels
Donald R. Griffin and Andrea M. Kasko

 Fluorescein, rhodamine, and aminomethylcoumarin acetate were linked to PEG macromers via several different photodegrable ortho-nitrobenzyl based linkers. The macromers were polymerized into gels through redox polymerization using APS (ammonia persulfate) and TEMED (N,N,N',N'-tetramethylenediamine). The rates of degradation and release of the linked molecules were observed at different wavelengths and found to differ for each molecule.

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The First Generation of b-Galactosidase-Responsive Prodrugs Designed for the Selective Treatment of Solid Tumors in Prodrug Monotherapy

Thibaut Legigan, Jonathan Clarhaut, Isabelle Tranoy-Opalinski, Arnaud Monvoisin,
Brigitte Renoux, Mika l Thomas, Alain Le Pape, St phanie Lerondel, and S bastien Papot

One strategy for treating cancer is antibody-directed enzyme prodrug therapy (ADEPT), in which a prodrug (eg. a galactosidase prodrug) can be used in combination with an antibody-beta-galactosidase conjugate that can bind an antigen on the tumor surface (that is often overexpressed), and release active drug at the site of the tumor. These researchers instead synthesized a galactoside prodrug composed of a targeting ligand, galactoside trigger, and drug that can interact with the tumor's endogenous beta-galactosidases. The researchers were able to show targeting of these drugs and activation in tumor cells, and confirm with studies done in mice. 

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Novel drug carriers: from grafted polymers to cross-linked vesicles

Jiangtao Xua, Qiang Fua, Jing M. Rena, Gary Bryantb and Greg G. Qiao*a
aDepartment of Chemical and Biomolecular Engineering, The University of Melbourne, Parkville, VIC 3010, Australia. 
bSchool of Applied Sciences, RMIT University, Melbourne, VIC 3000, Australia

This papers describes the synthesis of cross-linked particles via thiol-ene chemistry.  The authors make diblock copolymers via ROMP using oxonorbornene anhydride and a norbornene-PEG MM as monomers.  Next, they hydrolize the anhydride to to give free -COOH and then the block copolymers self-assemble into nanoparticles (~150 nm) at pH 4.  The self-assembled nanoparticles are then crosslinked using a tetrafunctional thiol crosslinker and the double bonds in the backbone of the polymer.  Finally, cisplatin (18.9% drug loading) is conjugated to the free -COOH from the hyrdolized oxonorbornene anhydride.  They showed the crosslinked nanoparticles hardly change size in different pH solutions and the drug loaded nanoparticles release cisplatin at a steady rate. 

Graphical abstract: Novel drug carriers: from grafted polymers to cross-linked vesicles

Post-Functionalization of a ROMP Polymer Backbone Via Radical Thiol-ene Coupling Chemistry

Johannes Arend van Hensbergen, Robert P. Burford, Andrew B. Lowe

Centre for Advanced Macromolecular Design (CAMD), School of Chemical Engineering,
University of New South Wales, Kensington, Sydney, New South Wales 2052, Australia

The authors ROMP a simple oxonobornene derivative and then functionalize the backbone of the polymer with different thio reagents.  The thiol-ene reaction is confirmed by NMR and most of the polymers retain their relative low PDI's after functionalization.

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Designing Biomaterials To Direct Stem Cell Fate

Chaenyung Cha,† William B. Liechty,‡ Ali Khademhosseini,†,Δ,§ and Nicholas A. Peppas‡,#,z,*

†Center for Biomedical Engineering, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School
‡Department of Chemical Engineering, #Department of Biomedical Engineering, zCollege of Pharmacy, The University of Texas, Austin
§Harvard-MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology, ΔWyss Institute for Biology Inspired Engineering, Harvard University, Boston, Massachusetts 02115, United States

This is a perspective on the design of biomaterials to direct stem cell fate.  The authors discuss factors such as, cell-responsive ligands, soluble factors, mechanical stimuli, and a relatively new example- targeting glycosaminoglycans. 

Tuning structural parameters of polyethylene brushes on silica nanoparticles in surface-initiated ethylene ‘‘living’’ polymerization and effects on silica dispersion in a polyolefin matrix

Polymer Chemistry

Polymerization from silica nanoparticle surface.

Graphical abstract: Stoichiometric imbalance-promoted synthesis of polymers containing highly substituted naphthalenes: rhodium-catalyzed oxidative polycoupling of arylboronic acids and internal diynes