Monthly Archive for: ‘January, 2013’

The 2nd Canada-Japan Nanotechnology Workshop 2013

Prof Winnik will be at the second Canada-Japan Nanotechnology Worshop  held on January 29th and 30th at Tokyo Big Sight in Tokyo.

For more information, here is the website of the event. You can find the program here.

Professor Winnik joins the Finland Distinguished Professor Program (FiDiPro)

Professor Winnik joins the Finland Distinguished Professor Program (FiDiPro)

Research project: Bioconjugated polymeric nanomaterials for industrial applications


Controlled synthesis and self-assembly of polymer-based bioconjugates will provide  broad array of novel materials for industrial applications (drug delivery, imaging, diagnostics, sensors, cell biological research tools). Despite its vast potential the technology of bioconjugated polymers and nano materials is under-developed field in Finland that needs to be improved. The project will generate an industrially applicable technology platform of bioconjugated polymeric nanostructures. The research involves versatile synthesis and testing of the nanomaterial libraries. The program will be carried out in close collaboration with industrial partners and special attention is paid to the generation of relevant IPR. The project will be linked also to the academic community in Finland beyond the project participants. This project will generate a platform of new polymer-based bioconjugated nanomaterials and relevant test methods for industrial applications. Companies from various fields are integral participants in the project.
Finnish host organization and contact person: University of Helsinki, Department of chemistry, Professor Heikki Tenhu

For more information on the FiDiPro, click here

Dual crosslinked hydrogel nanoparticles by nanogel bottom-up method for sustained-release delivery

Dual crosslinked hydrogel nanoparticles by nanogel bottom-up method for sustained-release delivery

Asako Shimoda, Shin-ichi Sawada, Arihiro Kano, Atsushi Maruyama, Alexandre Moquin, Françoise M. Winnik, Kazunari Akiyoshi

Polysaccharide–PEG hybrid nanogels (CHPOA–PEGSH) crosslinked by both covalent ester bonds and physical interactions were prepared by the reaction of a thiol-modified poly(ethylene glycol) (PEGSH) with acryloyl-modified cholesterol-bearing pullulan (CHPOA). Experimental parameters, including CHPOA concentration, the degree of acryloyl substitution of CHPOA, and the initial amounts of CHPOA and PEGSH, were modified in order to assess their effect on the size of the nanogels (50–150 nm) and on their degradation kinetics, monitored by dynamic light scattering (DLS) and asymmetrical flow field-flow fractionation (AF4) chromatography. Rhodamine-labeled nanogels were injected intravenously into mice and their concentration in blood was determined by a fluorescence assay as a function of post-injection time. The elimination half-life (t1/2) of CHPOA–PEGSH nanoparticles was about 15-fold longer (18 h) than that of CHP nanogels (1.2 h). The half-life enhancement of CHPOA–PEGSH was attributed to the presence of the crosslinker PEG chains, which prevent non-specific protein adsorption, and to the slow hydrolysis kinetics of the crosslinking esters in the biological milieu. The hybrid CHPOA–PEGSH nanogels are expected to be useful as injectable nanocarriers for drugs and proteins, in view of their low surface fouling and slow hydrolysis rate.

Tuning the Properties and Functions of 17β-Estradiol-polysaccharide Conjugates in Thin Films: Impact of Sample History

Tuning the Properties and Functions of 17β-Estradiol-polysaccharide Conjugates in Thin Films: Impact of Sample History

Zhimei Miao, Piotr Kujawa, Yiu-Ting Richard Lau, Sayaka Toita, Baowen Qi, Jun Nakanishi, Isabelle Cloutier, Jean-Francois Tanguay and Francoise M. Winnik

In addition to its role in the regulation of sex-related processes, 17β-estradiol (E2) participates in the prevention and treatment of cardiovascular diseases via nongenomic pathways mediated by estrogen receptors (ER-α) located in the cell membrane. To achieve specific nongenomic activity of E2, we linked E2 (4.4 mol %) to chitosan-phosphorylcholine (CH-PC) (20 mol % PC). Injections of ER-α solutions (5 to 100 nmol L–1) over rehydrated CH-PC-E2 thin films led to permanent adsorption of ER-α to the film surface, as detected by quartz crystal microbalance with dissipation (QCM-D). However, ER-α did not bind onto CH-PC-E2 films formed in situ and never dried. X-ray photoelectron spectroscopy (XPS) analysis of spin-cast CH-PC-E2 films revealed significant E2 enrichment of the topmost section of the film, attributed to the preferential migration of E2 toward the film/air interface upon drying. Mechanical analysis of CH-PC-E2 films in the frequency domain probed by QCM-D indicated that rehydrated films behave as an entangled network with junction points formed by self-assembly of hydrophobic E2 moieties and by ion pairing among PC groups, whereas films formed in situ are entangled polymer solutions with temporary junctions. The structural analysis presented offers useful guidelines for the study of amphiphilic biomacromolecules designed for therapeutic use as thin films.

Amphipol mediated surface immobilization of FhuA: a platform for label-free detection of the bacteriophage protein pb5

Amphipol mediated surface immobilization of FhuA: a platform for label-free detection of the bacteriophage protein pb5

Hajra Basit ,  K. Shivaji Sharma ,  Angéline Van der Heyden ,  Chantal Gondran ,  Cécile Breyton ,  Pascal Dumy ,  Françoise M. Winnik and Pierre Labbé

Biotinylated amphipol was used to entrap FhuA (an E. coli outer membrane protein) and immobilize the FhuA–amphipol complex on streptavidin surfaces. Using this assembly, we have successfully devised surface-based assays for studying the recognition of FhuA by pb5 (a bacteriophage T5 protein) and determination of the affinity constant.

New insights into the effects of molecular weight and end group on the temperature-induced phase transition of poly(N-isopropylacrylamide) in water

XingPing Qiu, Tsuyoshi Koga, Fumihiko Tanaka, Françoise M. Winnik

In an attempt to clarify issues related to the molecular weight dependence of the phase transition of poly(N-isopropylacrylamide) (PNIPAM) in water, we prepared a library of PNIPAM samples of well-controlled molecular weight (7000 to 45000 g/mol) bearing identical groups on each chain end. The polymers were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization of N-isopropylacrylamide (NIPAM) with a bifunctional chain tranfer agent and further end group modification. The effects of the end group chemical structure, hydroxyethyl (HE), propargyl (Pr), chloroethyl (CE), n-butyl (nBu), n-hexyl (nHe), and isobutylsulfanylthiosulfanyl (IBS) on the phase transition temperature of aqueous PNIPAM solutions were investigated by high-sensitivity differential scanning calorimetry (HS-DSC), yielding the enthalpy ΔH and the endotherm maximum temperature (T M), and turbidimetry, providing the cloud point (T CP) of each solution. The T CP and T M of the PNIPAM sample of lowest molar mass (M n 7,000 g/mol, 0.5 g/L) ranged, respectively, from 38.8 to 22.5 °C and 42.2 to 26.0 °C, depending on the structure of the end-group, whereas ΔH showed no strong end-group dependence. The phase transition of all polymers, except α,ω-di(n-butyl-PNIPAM), exhibited a marked dependence on the polymer molar mass.

Quantum Dot Cytotoxicity and ways to reduce it

Quantum Dot Cytotoxicity and ways to reduce it

Francoise M. Winnik and Dusica Maysinger.

The dramatic increase in the use of nanoparticles (NP) in industry and research has raised questions about the potential toxicity of such materials. Unfortunately, not enough is known about how the novel, technologically-attractive properties of NPs correlate with the interactions that may take place at the nano/bio interface. The academic, industrial, and regulatory communities are actively seeking answers to the growing concerns on the impact of nanotechnology on humans. In this Account we adopt quantum dots (QDs) as an illustrative example of the difficulties associated with the development of a rational science-based approach to nanotoxicology.

The optical properties of QDs are far superior to those of organic dyes in terms of emission and absorption bandwidths, quantum yield, and resistance to photobleaching. Moreover, QDs may be decorated with targeting moieties or drugs and, therefore, are candidates for site-specific medical imaging and for drug delivery, for example in cancer treatment. Earlier this year researchers demonstrated that QD-based imaging using monkeys caused no adverse effects although QDs accumulated in lymph nodes, bone marrow, liver, and spleen for up to 3 months after injection. Such persistence of QDs in live animals does, however, raise concerns about the safety of using QDs both in the laboratory and in the clinic.

Researchers anticipate that QDs will be increasingly used not only in clinical applications but also in various manufactured products. For example, QD-solar cells have emerged as viable contenders to complement or replace dye-sensitized solar cells; CdTe/CdS thin film cells have already captured approximately 10 percent of the global market, and in addition, QDs can serve as components of sensors and as emitting materials in LEDs. Given the clear indications that QDs will inevitably become components of a wide range of manufactured and consumer products, researchers and policy makers need to understand the possible health risks associated with exposure to QDs.

In this Account, we initially review the known mechanisms by which QDs can damage cells, including oxidative stress elicited by reactive oxygen species (ROS). We discuss lesser-known impairments induced in cells by nanomolar to picomolar concentrations of QDs, which imply that cadmium-containing QDs can exert genotoxic, epigenetic, and metalloestrogenic effects. These observations strongly suggest that minute concentrations of QDs could be sufficient to cause long lasting, even transgenerational, effects. We also consider various modes by which humans could be exposed to QDs in their work or through the environment. Although considerable advances have been made in enhancing the stability and overall quality of QDs, over time they can partially degrade in the environment or in biological systems, and eventually cause small, but cumulative undesirable effects.

A combination of toxicological, genetic, epigenetic and imaging approaches is required to create comprehensive guidelines for evaluating the nanotoxicity of nanomaterials, including QDs. Prior to biological investigations with these materials, an indispensible step must be the full characterization of NPs by complementary techniques. Specifically, the concentration, size, charge, and ligand stability of NPs in biological media must be known if we are to understand fully how the properties of nanoparticles and of their biological environment contribute to cytotoxicity.