School of Chemistry - Research Publications
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ItemA self-healing waterborne acrylic latex coating based on intrinsic hydrogen bonding(Elsevier, 2024-03)Acrylic coatings suffer damage in the form of cracking, which degrades both their protective and aesthetic performance over time. Self-healing technology offers the ability to solve this problem by allowing cracks to spontaneously heal without external diagnosis or intervention, offsetting the enormous costs associated with coating damage and repair. However, there is currently no efficient self-healing acrylic coating design, and research in the area remains noticeably sparse. In this research we sought to imbue a mechanically tough methyl methacrylate (MMA)/butyl acrylate (BA)/acrylic acid (AA) acrylic coating with self-healing functionality by incorporating self-healing monomers within the formulation. We synthesized a library of four acrylic monomers containing both a long amphiphilic spacer of variable length, and the 2-ureido-4[1H]-pyrimidinone (UPy) unit, which forms strong self-complementary quadruple hydrogen bonds. These UPy-monomers were able to participate in the emulsion polymerization of MMA, BA and AA, forming intrinsic hydrogen bonding networks within the subsequent acrylic coatings. These UPy functionalized coatings displayed optical self-healing and strain recovery over 24 h both at room temperature (∼28 %), and at elevated temperatures up to 50 °C (∼80 %). The coatings also displayed repeatable self-healing after four healing cycles, relative to an MMA/BA/AA coating.
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ItemNo Preview AvailableSelf-Immolative Polymer Nanoparticles with Precise and Controllable pH-Dependent Degradation(AMER CHEMICAL SOC, 2023-09-14)Polymer nanoparticles have generated significant interest as delivery systems for therapeutic cargo. Self-immolative polymers (SIPs) are an interesting category of materials for delivery applications, as the characteristic property of end-to-end depolymerization allows for the disintegration of the delivery system, facilitating a more effective release of the cargo and clearance from the body after use. In this work, nanoparticles based on a pH-responsive polymer poly(ethylene glycol)-b-(2-diisopropyl)amino ethyl methacrylate) and a self-immolative polymer poly[N,N-(diisopropylamino)ethyl glyoxylamide-r-N,N-(dibutylamino)ethyl glyoxylamide] (P(DPAEGAm-r-DBAEGAm)) were developed. Four particles were synthesized based on P(DPAEGAm-r-DBAEGAm) polymers with varied diisopropylamino to dibutylamino ratios of 4:1, 2:1, 2:3, and 0:1, termed 4:1, 2:1, 2:3, and 0:1 PGAm particles. The pH of particle disassembly was tuned from pH 7.0 to pH 5.0 by adjusting the ratio of diisopropylamino to dibutylamino substituents on the pendant tertiary amine. The P(DPAEGAm-r-DBAEGAm) polymers were observed to depolymerize (60-80%) below the particle disassembly pH after ∼2 h, compared to <10% at pH 7.4 and maintained reasonable stability at pH 7.4 (20-50% depolymerization) after 1 week. While all particles exhibited the ability to load a peptide cargo, only the 4:1 PGAm particles had higher endosomal escape efficiency (∼4%) compared to the 2:3 or 0:1 PGAm particles (<1%). The 4:1 PGAm particle is a promising candidate for further optimization as an intracellular drug delivery system with rapid and precisely controlled degradation.
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ItemNo Preview AvailableImpact of the Core Architecture of Dual pH-Responsive Polymer Nanoparticles on Intracellular Delivery of Doxorubicin(AMER CHEMICAL SOC, 2023-06-05)
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ItemNo Preview AvailableSelf-healing organic coatings-Fundamental chemistry to commercial application(ELSEVIER SCIENCE SA, 2023-10)
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ItemUnderstanding the Biological Interactions of pH-Swellable Nanoparticles(WILEY-V C H VERLAG GMBH, 2022-05)pH-responsive nanoparticles have generated significant interest for use as drug delivery systems due to their potential for inducible release at low pH. The pH variation from the bloodstream (pH 7.4) to intracellular compartments of cells called endosomes/lysosomes (pH < 5.0) has been of particular interest. However, one of the limitations with nanoparticle delivery systems is the inability to migrate out of these compartments to the cytosol or other organelles, via a process termed endosomal escape. Previous studies have postulated that pH-responsive nanoparticles can facilitate endosomal escape through a range of mechanisms including membrane interaction, pH-induced swelling, and the proton-sponge effect. In this study, a series of pH-swellable nanoparticles (85-100 nm) are designed and their impact on biological interactions, particularly endosomal escape, are investigated. The particles exhibit tunable pH-induced swelling (from 120% to 200%) and have good buffering capacity. The cellular association is studied using flow cytometry and endosomal escape is determined using a calcein leakage assay. Interestingly, no endosomal escape with all nanoparticle formulations is found, which suggests there are limitations with both the proton-sponge effect and pH-induced swelling mechanism as the primary methods for inducing endosomal escape.
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ItemLewis Base Catalyzed Synthesis of Sulfur Heterocycles via the C1‐Pyridinium Enolate(Wiley, 2022-08-15)Abstract While the addition of C1‐Lewis base enolates to carbonyls and related structures are well established, the related addition to thiocarbonyls compounds are unknown. Herein, we report a reaction cascade in which a C1‐pyridinium enolate undergos addition to dithioesters, trithiocarbonates and xanthates. The reaction provides access to a range of dihydrothiophenes and dihydrothiopyrans (28‐examples). Mechanistic investigations, including isolation of intermediates, electronic correlation, and kinetic isotope effect studies support the viability of an activated acid intermediate giving rise to the C1‐pyridinium enolate which undergoes turnover limiting cyclization. Subsequent formation of a β‐thiolactone regenerates the catalyst with loss of carbon oxysulfide providing the observed products.
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ItemLewis Base Catalyzed Synthesis of Sulfur Heterocycles via the C1-Pyridinium Enolate(WILEY-V C H VERLAG GMBH, 2022-08-15)While the addition of C1-Lewis base enolates to carbonyls and related structures are well established, the related addition to thiocarbonyls compounds are unknown. Herein, we report a reaction cascade in which a C1-pyridinium enolate undergos addition to dithioesters, trithiocarbonates and xanthates. The reaction provides access to a range of dihydrothiophenes and dihydrothiopyrans (28-examples). Mechanistic investigations, including isolation of intermediates, electronic correlation, and kinetic isotope effect studies support the viability of an activated acid intermediate giving rise to the C1-pyridinium enolate which undergoes turnover limiting cyclization. Subsequent formation of a β-thiolactone regenerates the catalyst with loss of carbon oxysulfide providing the observed products.
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ItemMicroencapsulation-based cell therapies(SPRINGER BASEL AG, 2022-07)Mapping a new therapeutic route can be fraught with challenges, but recent developments in the preparation and properties of small particles combined with significant improvements to tried and tested techniques offer refined cell targeting with tremendous translational potential. Regenerating new cells through the use of compounds that regulate epigenetic pathways represents an attractive approach that is gaining increased attention for the treatment of several diseases including Type 1 Diabetes and cardiomyopathy. However, cells that have been regenerated using epigenetic agents will still encounter immunological barriers as well as limitations associated with their longevity and potency during transplantation. Strategies aimed at protecting these epigenetically regenerated cells from the host immune response include microencapsulation. Microencapsulation can provide new solutions for the treatment of many diseases. In particular, it offers an advantageous method of administering therapeutic materials and molecules that cannot be substituted by pharmacological substances. Promising clinical findings have shown the potential beneficial use of microencapsulation for islet transplantation as well as for cardiac, hepatic, and neuronal repair. For the treatment of diseases such as type I diabetes that requires insulin release regulated by the patient's metabolic needs, microencapsulation may be the most effective therapeutic strategy. However, new materials need to be developed, so that transplanted encapsulated cells are able to survive for longer periods in the host. In this article, we discuss microencapsulation strategies and chart recent progress in nanomedicine that offers new potential for this area in the future.
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ItemPolyoxometalates as chemically and structurally versatile components in self-assembled materials(ROYAL SOC CHEMISTRY, 2022-03-02)Polyoxometalates (POMs) are anionic molecular metal oxides with expansive diversity in terms of their composition, structure, nuclearity and charge. Within this vast collection of compounds are dominant structural motifs (POM platforms), that are amenable to significant chemical tuning with minimal perturbation of the inorganic oxide molecular structure. Consequently, this enables the systematic investigation of these compounds as inorganic additives within materials whereby structure and charge can be tuned independently i.e. [PW12O40]3- vs. [SiW12O40]4- while also investigating the impact of varying the charge balancing cations on self-assembly. The rich surface chemistry of POMs also supports their functionalisation by organic components to yield so-called inorganic-organic hybrids which will be the key focus of this perspective. We will introduce the modifications possible for each POM platform, as well as discussing the range of nanoparticles, microparticles and surfaces that have been developed using both surfactant and polymer building blocks. We will also illustrate important examples of POM-hybrids alongside their potential utility in applications such as imaging, therapeutic delivery and energy storage.
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ItemTuning the properties of pH responsive nanoparticles to control cellular interactions in vitro and ex vivo(ROYAL SOC CHEMISTRY, 2016-01-01)Engineering the properties of nanoparticles to limit non-specific cellular interactions is critical for developing effective drug delivery systems. Differences between interactions with cultured cells and human blood highlights the need for appropriate assays