Covalent Functionalization of Graphene with Reactive Intermediates

Acc. Chem. Res.

Jaehyeung Park and Mingdi Yan *

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

http://pubs.acs.org/doi/abs/10.1021/ar300172h

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

http://pubs.acs.org/doi/pdf/10.1021/mz300366s
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.

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

http://onlinelibrary.wiley.com/doi/10.1002/anie.201204935/full

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. 

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

http://pubs.rsc.org/en/content/articlehtml/2012/cc/c2cc37319j

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. 

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

http://onlinelibrary.wiley.com/doi/10.1002/pola.26433/full

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.

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

http://pubs.acs.org/doi/full/10.1021/nn304773b

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

http://pubs.rsc.org/en/content/articlepdf/2013/py/c2py20758c

Polymerization from silica nanoparticle surface.