Archive for November, 2013

Paper of the week: Water-soluble BODIPY-conjugated glycopolymers as fluorescent probes for live cell imaging

Fluorescent probes have attracted significant attention in targeted imaging and early detection of tumor cells. Detection of real biomarkers in physiological fluid samples can dramatically impair fluorescent agent sensitivity and specificity because of biofouling and nonspecific binding. These uncertainties and drawbacks have limited the practical use of fluorescent agents in a clinical environment for medical diagnostics. Hence, the development of novel fluorescent materials with high cellular internalization efficiency, good photostability, and high specificity for tumor cell staining is in urgent demand.

Graphical abstract: Water-soluble BODIPY-conjugated glycopolymers as fluorescent probes for live cell imaging

In this article, Zhang, Li and co-workers synthesized by Atom Transfer Radical Polymerization (ATRP) a highly water-soluble, multivalent and highly specific BODIPY-conjugated glycopolymer for direct tumor cell imaging, which showed good photostability. The cell viability of BODIPY-conjugated glycopolymers against HepG2 and NIH3T3 cells was more than 80%, indicating that the glycopolymers have low cytotoxicity to living cells. Moreover, simple incubation of living cells with a BODIPY-conjugated glycopolymer led to efficient internalization into HepG2 and clear visualization in cytoplasm, due to the high brightness of BODIPY and good specificity between HepG2 and galactose as compared to NIH3T3 cells. These results suggest that BODIPY-conjugated glycopolymers have potential use as fluorescent probes in live cell imaging.

Water-soluble BODIPY-conjugated glycopolymers as fluorescent probes for live cell imaging by Zhentan Lu, Lin Mei, Xinge Zhang, Yanan Wang, Yu Zhao and Chaoxing Li Polym. Chem. 2013, 4, 5743-5750.

Julien Nicolas is a guest web-writer and advisory board member for Polymer Chemistry. He currently works at Univ. Paris-Sud (FR) as a CNRS researcher.

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Paper of the week: Highly stretchable and resilient hydrogels

Hydrogels are chemically or physically cross-linked three-dimensional networks that are water insoluble but can absorb a large amount of water or biological fluids and maintain their semisolid morphology. Besides their various applications in superabsorbents, cosmetics and food, contact lenses, actuators and sensors in the materials science domain, hydrogels have become more and more attractive in artificial implants, biomedical devices, tissue engineering and regenerative medicine, etc., due to their unique properties such as similar flexibility, high water content, and molecule diffusion to natural tissues. However, unlike natural hydrogel-like bio-tissues, such as skin, muscle, cartilage, tendon, and blood-vessel which are generally strong and resilient, classic hydrogels are often brittle and have very poor mechanical performance, including low strain to break, low toughness and high strain–stress hysteresis, especially in the high strain region. Thus, design of hydrogels with good mechanical properties, such as high toughness, high stretchability and resilience, is crucially important and has drawn the extensive interest of many scientists.

Graphical abstract: Highly stretchable and resilient hydrogels from the copolymerization of acrylamide and a polymerizable macromolecular surfactant

In this paper, Huang, Guo and co-workers developed a novel micellar cross-linking copolymerization method to prepare highly stretchable and resilient hydrogels. The polymerization was based on free-radical copolymerization of water soluble acrylamide and a polymerizable macromolecular surfactant (i.e., amphiphilic polyurethane macromonomer) which can self-assemble into micelles acting as multifunctional cross-linkers. The mechanical properties, such as breaking elongation ratio, modulus and fracture toughness can be easily adjusted by varying the concentration of the polymerizable macromolecular surfactants. In addition, the mechanical energy storage efficiency (also known as resilience) was more than 96% at a strain up to 400%. These findings established a strategy for the preparation of hydrogels that combine high extendibility with excellent resilience and may greatly benefit the further use of hydrogels in tissue engineering and other soft materials research fields.

Highly stretchable and resilient hydrogels from the copolymerization of acrylamide and a polymerizable macromolecular surfactant by Mei Tan, Tingting Zhao, He Huang and Mingyu Guo Polym. Chem. 2013, 4, 5570-5576.

Julien Nicolas is a guest web-writer and advisory board member for Polymer Chemistry. He currently works at Univ. Paris-Sud (FR) as a CNRS researcher.

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Interview with Christopher Barner-Kowollik

You may have seen our recent profile of Polymer Chemistry Associate Editor Christopher Barner-Kowollik. Here, we ask Christopher more about his career, research and the challenges polymer chemistry can solve.

Which projects are you working on at the moment?

We have a very broad portfolio of project areas in my team, divided into the research platforms ‘synthetic method development’, ‘advanced hybrid materials’, ‘underpinning mechanisms’ and ‘advanced polymer characterization’, with several parallel projects in each. Light driven surface encoding and recoding protocols with applications in cell guidance as well as targeted cell attachment are certainly an important activity, including the development of new photo-chemical reaction sequences. We continue to have a strong interest in biomaterials modification both in solution and the solid state and have not too long ago expanded our portfolio into biomimetic system ranging from universally adhesive bonding/debonding systems to bionspired self-folding single chains and nanoparticles. The design of new functional direct laser writing chemistries featuring reactive surfaces has recently moved into our centre of interest, too, as have supramolecular polymer systems with switchable property profiles. Although a smaller activity, the mechanistic study of photoinduced processes and polymerizations is still an important fundamental activity. For more information on all of our activities, please visit www.macroarc.de.

What motivated you to specialise in polymer chemistry?

I was trained as a physical chemist (albeit with a macromolecular touch) and became continuously more interested in synthetic polymer chemistry over the years. Polymer chemistry offers such a wide variety of research activities and requires knowledge from many chemical disciplines including organic, inorganic, physical and analytical chemistry that very much appeals to me. In addition, I always liked generating materials that can find applications as well as the interactions with industrial partners.
Nevertheless, there is ample room for fundamental research in polymer science and many unanswered questions and challenges exist, which require creativity and clever ideas.

What are the hot topics in polymer research at the moment?

In terms of general challenges that polymer chemistry can and must contribute to solutions for are efficient energy storage, conversion and handling as well as advanced materials for biomedical applications, from regenerative medicine to delivery systems. To address these broad challenges, we as synthetic polymer chemists have to provide solutions for the next step change in our ability to synthesize macromolecules, be it via the provision of precision surface design methodologies, controlling release from polymer systems, folding polymers, sequence controlled polymers or combining synthetic polymer chemistry with biomimetic approaches. Further, many solutions for applications require fine control over network properties, which is not yet available (e.g. monodisperse networks). Some very exciting work is currently also being done in the area of self-healing materials and sheet-like two dimensional polymers. In the materials research area, mimicking nature’s best materials such as nacre is an exciting topic. That said, the field is so diverse that one can identify many hot areas – there is rarely anything non-relevant. It all depends on one’s personal interests and views.

What current problem would you like to see science provide a solution to?

A cure for cancer would certainly be high on the list, but I believe the provision of clean drinking water to the world’s population would probably save even more lives.

What do you find to be the most rewarding aspect of your career?

Discussing and debating scientific questions (down to the details!) with my coworkers and colleagues as well as educating young scientists at all stages of their careers from undergraduate researcher to PhD student to junior group leader.
It is such a rewarding experience to solve a scientific problem and to see enthusiastic researchers mature into confident scientists.

What’s the secret to being a successful scientist?

Curiosity, creativity, very hard work and perseverance as well as the ability to enjoy and part-take in aspects of life that have nothing to do with science (e.g. music, theatre, literature, your family, friends).

Which scientist past or present do you most admire?

Charles Darwin for arguably providing the most influential theory (fact!) in the history of science.

If you weren’t a scientist, what would you be?

On the day of enrolling at university, I was still considering two options: Chemistry or History, both of which I love. No question, as an alternative to the natural sciences, I would have loved to study history – and maybe I will do some day! I have the highest respect for historians and find the works of contemporary historians such as Ian Kershaw absolutely fascinating reading.

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Paper of the week: DNA binding ability of macromolecular platinum-drugs

Cisplatin (cis-diamminedichloroplatinum(II) (CDDP)) is a well-known platinum anticancer drug effective to treat solid tumours in head and neck, non-small cell lung, ovarian and testicular cancers. However, the use of cisplatin also results in severe side effects as well as resistance against the drug. The next generation of platinum drugs had either different amine ligands to replace NH3 or a different leaving ligand to replace chloride to improve water-solubility and stability, and also to reduce side-effects. Meanwhile, Pt(IV) prodrugs were also developed to combat excessive toxicity but also to confer targeting ability for improved anticancer activity.

Graphical abstract: Macromolecular platinum-drugs based on statistical and block copolymer structures and their DNA binding ability

In this article, Stenzel and co-workers designed three different macromolecular Pt-drugs using Cu-click chemistry to attach a bidentate amino ligand to the polymer. Two statistical copolymers with different ligand densities were prepared, which were compared to the block copolymer. DNA binding studies revealed that the statistical copolymer with the highest density of Pt-drugs had the highest affinity to the DNA, due to a multivalent effect. Interestingly, when evaluating the cytotoxic effect of these macromolecular drugs using OVCAR-3 cells the activities of all three polymer architectures were similar. It can therefore be concluded that although DNA binding tests may give an initial indication on the ability of the structure to bind to the DNA, they cannot predict the outcome.

Macromolecular platinum-drugs based on statistical and block copolymer structures and their DNA binding ability by Khairil Juhanni Abd Karim, Sandra Binauld, Wei Scarano and Martina H. Stenzel Polym. Chem. 2013, 4, 5542-5554.

Julien Nicolas is a guest web-writer and advisory board member for Polymer Chemistry. He currently works at Univ. Paris-Sud (FR) as a CNRS researcher.

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Paper of the week: Multicomponent click chemistry from Biginelli reaction

Click chemistry, first described by Sharpless and co-workers, refers to a type of modular, atom-economic reaction that provides high yields in short reaction times with no or only inoffensive byproducts. A few reactions, such as the well-known copper-catalyzed azide–alkyne cycloaddition (CuAAC), thiol–ene/yne free-radical addition, (hetero) Diels–Alder reaction, hydroxyl/thiol-isocyanate coupling, etc., have been discovered to have these attractive ‘clickable’ features and have found important applications in many areas. Until now, almost all click reactions are two-component reactions. It could be very interesting if three or more reactive elements could be combined together to construct new click reactions, which might provide more choices and functional diversity. Multicomponent reactions (MCRs) seem to be possible candidates to address this point. MCRs are a type of modular and highly efficient reaction using at least three different reactants to achieve a single complex and functional product in one pot with negligible or no byproducts.

Graphical abstract: A new insight into the Biginelli reaction: the dawn of multicomponent click chemistry?

In this context, Tao, Wei and co-workers have revisited the Biginelli reaction as a potential tri-component click chemistry. Through the quick and efficient modification of polymer side groups and locking of two polymer chains, Biginelli-type homopolymers and Biginelli-locked copolymers can be facilely and quantitatively obtained. Moreover, the Biginelli reaction showed good compatibility with RAFT polymerization to construct a one-pot MCP system. Both reactions proceeded well without interference, and almost neat Biginelli functionalized homopolymers were successfully achieved in a one-pot fashion. More importantly, the Biginelli reaction can also be recognized as a ‘catalyst-free’ bioorthogonal-click reaction, through which a fluorescent probe can be covalently anchored onto cell membranes without external addition of a catalyst, implying the potential application of the Biginelli reaction in chemical biology.

A new insight into the Biginelli reaction: the dawn of multicomponent click chemistry? by Chongyu Zhu, Bin Yang, Yuan Zhao, Changkui Fu, Lei Tao and Yen Wei Polym. Chem. 2013, 4, 5395-5400.

Julien Nicolas is a guest web-writer and advisory board member for Polymer Chemistry. He currently works at Univ. Paris-Sud (FR) as a CNRS researcher.

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IPST2013: International Polymer Conference, Yogyakarta, Indonesia

The Innovation in Polymer Science and Technology 2013 (IPST2013) was held in Yogyakarta, Indonesia on October 7 – 10, 2013 and organised by the Indonesian Polymer Association (HPI). It was attended by more than 250 participants from over 20 countries; presenting about 200 paper works consisting of 102 oral and 108 poster presentations, including 7 plenary speakers, and 24 keynote speakers. To date, this event was the biggest international polymer conference, organised by the Indonesian Polymer Association.

IPST2013

The conference was officially opened by the representative of Indonesian government, the Ministry of Research and Technology of Indonesia. The Indonesian Polymer Association presented a 2013 HPI award to Dr. M. Sugandi (a former of the HPI’s chair) for her lifetime contributions in polymer research as well as in the polymer society in Indonesia. The best student posters were awarded to 5 students: Arum Patriati (Indonesia), Shih Ming Chang (Taiwan), Emiko Ohara (Japan), Ayami Nagayama (Japan), and Koay Seong Chun (Malaysia). Zainon Othman (Malaysia) and Firman Kurniawansyah (Indonesia) were awarded the best oral presentation prize.

The IPST2013 was officially closed by Ms. Eniya L. Dewi, the chair of the IPST2013 and ICFCHT2013. The next conference will take place in 2016 (IPST2016) and will be held in Padang, West Sumatera, Indonesia. We look forward to seeing you there!

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Author of the Week: Professor Parameswar K. Iyer

Professor Parameswar K. Iyer received his B.Sc. (Chemistry) in 1993 and his M.Sc. (Organic Chemistry) in 1995 at Bhavnagar University. He completed his Ph.D. in 1999 working at the Central Salt and Marine Chemicals Research Institute, Bhavnagar, India working on asymmetric catalysis. He worked as a postdoctoral fellow at Technion, Israel (1999-2001), University of California Santa Barbara (2001-2003) and at Case Western Reserve University, Cleveland (2003-2004). He then joined the Indian Institute of Technology Guwahati as an Assistant Professor in July 2004. In 2008 he was promoted as an Associate Professor and then a full Professor in January 2013. Professor Iyer currently leads a Research Group at the Department of Chemistry and Center for Nanotechnology at IIT Guwahati of ~10 people. His research interests involve the development of novel conjugated polymer and macromolecular structures, their application in optoelectronic devices, chemical and biological sensors and extension to therapeutics.

Group web-link: http://www.iitg.ernet.in/chemistry/fac/pki/

What was your inspiration in becoming a chemist?

As a high school student I had intense curiosity and found science practical, especially chemistry and biology, highly exciting and I used to look forward to it. This interest was further enhanced when I used to visit Central Salt and Marine Chemicals Research Institute (CSMCRI), Bhavnagar, India that used to be in close proximity to my home. Hence, I chose chemistry as my further line of study. I was also fortunate to work at this laboratory for my graduate (PhD) thesis work under the guidance of Dr. Rukhsana I. Kureshy that kindled my interest in chemistry. I realized with time that being a teacher along with being a chemist is much more interesting since this provided immense opportunities to interact with young bright minds.

What was the motivation to write your Polymer Chemistry article?

Over the years I observed that Polymer Chemistry publishes high quality work on several aspects of polymers and their interdisciplinary applications. We have been working for the past few years on the development of conjugated polymer systems with diverse applications in sensors and diagnosis and had an aim of extending these systems to therapeutics. We have developed a number of polymer and oligomer based systems that had diagnosis potential for neurological disorders. The key advantage of the system reported in the present article is that these materials can be prepared by an easy polymerization method, it is non toxic and it can bind toxic metals such as iron and iron containing metalloproteins at varying pH conditions in biological media at extremely low concentrations. This motivated us to use this system to probe metal traces in cerebrospinal fluid (CSF) having amyloid beta (Ab) that add to the toxicity enhancement. The binding of metal in CSF with the help of this new polymer based material disrupted the Ab instantly. With the low levels of detection that were possible with this polymer, the early diagnosis and therapeutic applications of this polymer for Alzheimer’s disease and other neurological disorders are huge.

Why did you choose Polymer Chemistry to publish your work?

Although Polymer Chemistry was a new journal, it has established itself as a top journal in polymer chemistry. I have known from colleagues that the reviewer comments received from Polymer Chemistry were very helpful and criticisms allowed improvement of the manuscript. I experienced the same as my colleagues, and found that this also encouraged me and my students to carry out the revisions with great enthusiasm, drawing praise from reviewers. I also found that the rapid review and publication time and wide readership were very helpful.

In which upcoming conferences may our readers meet you?

I am planning to attend http://www.kjf-icomep2013.org and http://www.icsm2014.fi/ conferences. I am also organizing the 3rd International Conference on ‘Advanced Nanomaterials and Nanotechnology” (ICANN-2013) at the Indian Institute of Technology Guwahati (IITG), India, which will take plade between December 1-3, 2013.

http://www.iitg.ernet.in/icann2013/

How do you spend your spare time?

When I am not at work, I am either at the athletics track or at basketball courts which helps me stay fit physically and mentally. Besides sports, I love cooking, gardening and photography.

Which profession would you choose if you were not a scientist?

It’s easier to tell what I would not have become than what I would have. As an undergraduate student, I was inclined to join Air force due to my NCC activities. Being a sports coach would also have been a good career option.

A rapid and sensitive detection of ferritin at a nanomolar level and disruption of amyloid β fibrils using fluorescent conjugated polymer
B. Muthuraj, Sameer Hussain and Parameswar Krishnan Iyer  
Polym. Chem., 2013, 4, 5096-5107 DOI: 10.1039/C3PY00680H

Professor Iyer’s peper was recently featured as the Paper of the Week.

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