00 College Street

Toronto, Canada

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Toronto, Canada
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Cherukupally P.,King's College | Acosta E.J.,00 College Street | Hinestroza J.P.,Cornell University | Bilton A.M.,King's College | Park C.B.,King's College
Environmental Science and Technology | Year: 2017

Separation of toxic organic pollutants from industrial effluents is a great environmental challenge. Herein, an acid-base engineered foam is employed for separation of micro-oil droplets from an aqueous solution. In acidic or basic environments, acid-base polymers acquire surface charge due to protonation or dissociation of surface active functional groups. This property is invoked to adsorb crude oil microdroplets from water using polyester polyurethane (PESPU) foam. The physicochemical surface properties of the foam were characterized using X-ray photoelectron spectroscopy, inverse gas chromatography, electrokinetic analysis, and micro-computed tomography. Using the surface charge of the foam and oil droplets, the solution pH (5.6) for maximum separation efficacy was predicted. This optimal pH was verified through underwater wetting behavior and adsorption experiments. The droplet adsorption onto the foam was governed by physisorption, and the driving forces were attributed to electrostatic attraction and Lifshitz-van der Waals forces. The foam was regenerated and reused multiple times by simple compression. The lowest trace oil content in the retentate was 3.6 mg L-1, and all oil droplets larger than 140 nm were removed. This work lays the foundation for the development of a new class of engineered foam adsorbents with the potential to revolutionize water treatment technologies. © 2017 American Chemical Society.


Ng A.H.C.,University of Toronto | Ng A.H.C.,Donnelly College | Dean Chamberlain M.,University of Toronto | Dean Chamberlain M.,Donnelly College | And 6 more authors.
Nature Communications | Year: 2015

We report a new technique called Digital microfluidic Immunocytochemistry in Single Cells (DISC). DISC automates protocols for cell culture, stimulation and immunocytochemistry, enabling the interrogation of protein phosphorylation on pulsing with stimulus for as little as 3s. DISC was used to probe the phosphorylation states of platelet-derived growth factor receptor (PDGFR) and the downstream signalling protein, Akt, to evaluate concentration- and time-dependent effects of stimulation. The high time resolution of the technique allowed for surprising new observations - for example, a 10s pulse stimulus of a low concentration of PDGF is sufficient to cause >30% of adherent fibroblasts to commit to Akt activation. With the ability to quantitatively probe signalling events with high time resolution at the single-cell level, we propose that DISC may be an important new technique for a wide range of applications, especially for screening signalling responses of a heterogeneous cell population. © 2015 Macmillan Publishers Limited.


Chou L.Y.T.,Institute of Biomaterials and Biomedical Engineering | Zagorovsky K.,Institute of Biomaterials and Biomedical Engineering | Chan W.C.W.,Institute of Biomaterials and Biomedical Engineering | Chan W.C.W.,University of Toronto | Chan W.C.W.,00 College Street
Nature Nanotechnology | Year: 2014

The assembly of nanomaterials using DNA can produce complex nanostructures, but the biological applications of these structures remain unexplored. Here, we describe the use of DNA to control the biological delivery and elimination of inorganic nanoparticles by organizing them into colloidal superstructures. The individual nanoparticles serve as building blocks, whose size, surface chemistry and assembly architecture dictate the overall superstructure design. These superstructures interact with cells and tissues as a function of their design, but subsequently degrade into building blocks that can escape biological sequestration. We demonstrate that this strategy reduces nanoparticle retention by macrophages and improves their in vivo tumour accumulation and whole-body elimination. Superstructures can be further functionalized to carry and protect imaging or therapeutic agents against enzymatic degradation. These results suggest a different strategy to engineer nanostructure interactions with biological systems and highlight new directions in the design of biodegradable and multifunctional nanomedicine. © 2014 Macmillan Publishers Limited. All rights reserved.


Fiddes L.K.,University of Toronto | Chang J.,00 College Street | Yan N.,University of Toronto | Yan N.,00 College Street
Sensors and Actuators, B: Chemical | Year: 2014

This work outlines a new approach for modifying conventional RFID tags with chemically sensitive conductive composites. Conductive composite films were integrated into the RFID tag circuit. As the film was exposed to selected analytes the film swelled increasing the resistance of the film and decreasing the communicating ability of the RFID tag. Using maleic anhydride as the sensing material, the composite was able to detect different biogenic amines associated with food spoilage. RFID tag response was found to depend on amine concentration, tag initial resistance and type of biogenic amine. RFID sensors of this nature are attractive for a number of applications in the gaseous sensing industry. © 2014 Elsevier B.V.


Fiddes L.K.,University of Toronto | Yan N.,University of Toronto | Yan N.,00 College Street
Sensors and Actuators, B: Chemical | Year: 2013

This work outlines a new approach for the construction of a wireless and battery-free broad response vapour sensor. Carbon black/organic polymer composites are known to swell reversibly upon exposure to volatile chemicals. We integrated these types of composites into the electronic elements of a conventional passive RFID tag circuitry to produce resistance changes that result in a change in the RFID tag's output signal frequency and amplitude. To identify vapours, arrays of RFID tags with such vapour-sensing elements were constructed, with each tag containing carbon black as the conducting element and a polymer as the sensing element. The different gas-solid partition coefficients for the polymers in the sensor array produce a unique pattern of signal changes that can be used to classify vapours. This sensor array was able to identify and quantify several vapours of interest (water, ammonia, ethanol and toluene). © 2013 Elsevier Ltd.


Ballios B.G.,King's College | Clarke L.,King's College | Coles B.L.K.,King's College | Shoichet M.S.,King's College | And 2 more authors.
Biology Open | Year: 2012

Self-renewing, multipotential retinal stem cells (RSCs) reside in the pigmented ciliary epithelium of the peripheral retina in adult mammals. RSCs can give rise to rhodopsin positive-cells, which can integrate into early postnatal retina, and represent a potentially useful option for cellular therapy. The ability to purify a stem cell population and direct the differentiation toward a particular cell lineage is a challenge facing the application of stem cells in regenerative medicine. Here we use cell sorting to prospectively enrich mouse RSCs based on size, granularity and low expression of P-cadherin and demonstrate that only rare cells with defined properties proliferate to form colonies.We show that clonally-derived mouse and human RSC progeny are multipotent and can differentiate into mature rhodopsin-positive cells with high efficiency using combinations of exogenous culture additives known to influence neural retinal development, including taurine and retinoic acid. This directed RSC differentiation follows the temporal sequence of photoreceptor differentiation in vivo, and the cells exhibit morphology, protein and gene expression consistent with primary cultures of rods in vitro. These results demonstrate that the RSC, an adult stem cell, can be enriched and directed to produce photoreceptors as a first step toward a targeted cell replacement strategy to treat retinal degenerative disease. © 2012. Published by The Company of Biologists Ltd.


Chan D.P.Y.,00 College Street | Chan D.P.Y.,60 Co | Deleavey G.F.,McGill University | Owen S.C.,00 College Street | And 5 more authors.
Biomaterials | Year: 2013

Efficient and targeted cellular delivery of small interfering RNAs (siRNAs) and antisense oligonucleotides (AONs) is a major challenge facing oligonucleotide-based therapeutics. The majority of current delivery strategies employ either conjugated ligands or oligonucleotide encapsulation within delivery vehicles to facilitate cellular uptake. Chemical modification of the oligonucleotides (ONs) can improve potency and duration of activity, usually as a result of improved nuclease resistance. Here we take advantage of innovations in both polymeric delivery vehicles and ON stabilization to achieve receptor-mediated targeted delivery of siRNAs or AONs for gene silencing. Polymeric nanoparticles comprised of poly(lactide-. co-2-methyl, 2-carboxytrimethylene carbonate)-. g-polyethylene glycol-furan/azide are click-modified with both anti-HER2 antibodies and nucleic acids on the exterior PEG corona. Phosphorothioate (PS), 2'F-ANA, and 2'F-RNA backbone chemical modifications improve siRNA and AON potency and duration of activity. Importantly, delivery of these nucleic acids on the exterior of the polymeric immuno-nanoparticles are as efficient in gene silencing as lipofectamine transfection without the associated potential toxicity of the latter. © 2013 Elsevier Ltd.


Ho K.S.,00 College Street | Ho K.S.,University of Toronto | Poon P.C.,00 College Street | Owen S.C.,00 College Street | And 3 more authors.
BMC Cancer | Year: 2012

Background: Human tumour xenografts in immune compromised mice are widely used as cancer models because they are easy to reproduce and simple to use in a variety of pre-clinical assessments. Developments in nanomedicine have led to the use of tumour xenografts in testing nanoscale delivery devices, such as nanoparticles and polymer-drug conjugates, for targeting and efficacy via the enhanced permeability and retention (EPR) effect. For these results to be meaningful, the hyperpermeable vasculature and reduced lymphatic drainage associated with tumour pathophysiology must be replicated in the model. In pre-clinical breast cancer xenograft models, cells are commonly introduced via injection either orthotopically (mammary fat pad, MFP) or ectopically (subcutaneous, SC), and the organ environment experienced by the tumour cells has been shown to influence their behaviour.Methods: To evaluate xenograft models of breast cancer in the context of EPR, both orthotopic MFP and ectopic SC injections of MDA-MB-231-H2N cells were given to NOD scid gamma (NSG) mice. Animals with matched tumours in two size categories were tested by injection of a high molecular weight dextran as a model nanocarrier. Tumours were collected and sectioned to assess dextran accumulation compared to liver tissue as a positive control. To understand the cellular basis of these observations, tumour sections were also immunostained for endothelial cells, basement membranes, pericytes, and lymphatic vessels.Results: SC tumours required longer development times to become size matched to MFP tumours, and also presented wide size variability and ulcerated skin lesions 6 weeks after cell injection. The 3 week MFP tumour model demonstrated greater dextran accumulation than the size matched 5 week SC tumour model (for P < 0.10). Immunostaining revealed greater vascular density and thinner basement membranes in the MFP tumour model 3 weeks after cell injection. Both the MFP and SC tumours showed evidence of insufficient lymphatic drainage, as many fluid-filled and collagen IV-lined spaces were observed, which likely contain excess interstitial fluid.Conclusions: Dextran accumulation and immunostaining results suggest that small MFP tumours best replicate the vascular permeability required to observe the EPR effect in vivo. A more predictable growth profile and the absence of ulcerated skin lesions further point to the MFP model as a strong choice for long term treatment studies that initiate after a target tumour size has been reached. © 2012 Ho et al.; licensee BioMed Central Ltd.


PubMed | 00 College Street
Type: Journal Article | Journal: Biomaterials | Year: 2013

Efficient and targeted cellular delivery of small interfering RNAs (siRNAs) and antisense oligonucleotides (AONs) is a major challenge facing oligonucleotide-based therapeutics. The majority of current delivery strategies employ either conjugated ligands or oligonucleotide encapsulation within delivery vehicles to facilitate cellular uptake. Chemical modification of the oligonucleotides (ONs) can improve potency and duration of activity, usually as a result of improved nuclease resistance. Here we take advantage of innovations in both polymeric delivery vehicles and ON stabilization to achieve receptor-mediated targeted delivery of siRNAs or AONs for gene silencing. Polymeric nanoparticles comprised of poly(lactide-co-2-methyl, 2-carboxytrimethylene carbonate)-g-polyethylene glycol-furan/azide are click-modified with both anti-HER2 antibodies and nucleic acids on the exterior PEG corona. Phosphorothioate (PS), 2F-ANA, and 2F-RNA backbone chemical modifications improve siRNA and AON potency and duration of activity. Importantly, delivery of these nucleic acids on the exterior of the polymeric immuno-nanoparticles are as efficient in gene silencing as lipofectamine transfection without the associated potential toxicity of the latter.

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