Publications
92 results found
Lu B, Tarn MD, Pamme N, et al., 2017, Fabrication of Tailorable pH Responsive Cationic Amphiphilic Microgels on a Microfluidic Device for Drug Release, Journal of Polymer Science Part A: Polymer Chemistry, Vol: 56, Pages: 59-66, ISSN: 0887-624X
Cationic, amphiphilic microgels of differing compositions based on hydrophilic, pH, and thermoresponsive 2-(dimethylamino)ethyl methacrylate (DMAEMA) and hydrophobic, nonionic n-butyl acrylate (BuA) are synthesized using a lab-on-a-chip device. Hydrophobic oil-in-water (o/w) droplets are generated via a microfluidic platform, with the dispersed (droplet) phase containing the DMAEMA and BuA, alongside the hydrophobic cross-linker, ethylene glycol dimethacrylate, and a free radical initiator in an organic solvent. Finally, the hydrophobic droplets are photopolymerized via a UV light source as they traverse the microfluidic channel to produce the cationic amphiphilic microgels. This platform enables the rapid, automated, and in situ production of amphiphilic microgels, which do not match the core-shell structure of conventionally prepared microgels but are instead based on random amphiphilic copolymers of DMAEMA and BuA between the hydrophobic cross-links. The microgels are characterized in terms of their swelling and encapsulation abilities, which are found to be influenced by both the pH response and the hydrophobic content of the microgels.
Luongo G, Perez JE, Kosel J, et al., 2017, Scalable high-affinity stabilization of magnetic iron oxide nanostructures by a biocompatible antifouling homopolymer, ACS Applied Materials and Interfaces, Vol: 9, Pages: 40059-40069, ISSN: 1944-8244
Iron oxide nanostructures have been widely developed for biomedical applications, due to their magnetic properties and biocompatibility. In clinical application, the stabilization of these nanostructures against aggregation and non-specific interactions is typically achieved using weakly anchored polysaccharides, with better-defined and more strongly anchored synthetic polymers not commercially adopted due to complexity of synthesis and use. Here, we show for the first time stabilization and biocompatibilization of iron oxide nanoparticles by a synthetic homopolymer with strong surface anchoring and a history of clinical use in other applications, poly(2-methacryloyloxyethy phosphorylcholine) (poly(MPC)). For the commercially important case of spherical particles, binding of poly(MPC) to iron oxide surfaces and highly effective individualization of magnetite nanoparticles (20 nm) are demonstrated. Next-generation high-aspect ratio nanowires (both magnetite/maghemite and core-shell iron/iron oxide) are furthermore stabilized by poly(MPC)-coating, with nanowire cytotoxicity at large concentrations significantly reduced. The synthesis approach is exploited to incorporate functionality into the poly(MPC) chain is demonstrated by random copolymerization with an alkyne-containing monomer for click-chemistry. Taking these results together, poly(MPC) homopolymers and random copolymers offer a significant improvement over current iron oxide nanoformulations, combining straightforward synthesis, strong surface-anchoring and well-defined molecular weight.
Chung JJ, Sum BST, Li S, et al., 2017, Effect of comonomers on physical properties and cell attachment to silica-methacrylate/acrylate hybrids for bone substitution, Macromolecular Rapid Communications, Vol: 38, Pages: 1-5, ISSN: 1022-1336
Hybrids with a silica network covalently bonded to a polymer are promising materials for bone repair. Previous work on synthesizing methyl methacrylate (MMA) based copolymers by reversible addition‐fragmentation chain transfer (RAFT) polymerization gives high tailorability of mechanical properties since sophisticated polymer structures can be designed. However, more flexible hybrids would be beneficial. Here, n‐butyl methacrylate (BMA) and methyl acrylate (MA) based hybrids are produced. Unlike MMA, BMA and MA hybrids do not show plastic deformation, and BMA hybrid has strain to failure of 33%. Although the new hybrids are more flexible, preosteoblast cells do not adhere on their surfaces, due to higher hydrophobicity and lower stiffness. Comonomer choice is crucial for bone regenerative hybrids.
Chung JJ, Fujita Y, Li S, et al., 2017, Biodegradable inorganic-organic hybrids of methacrylate star polymers for bone regeneration, Acta Biomaterialia, Vol: 54, Pages: 411-418, ISSN: 1878-7568
Hybrids that are molecular scale co-networks of organic and inorganic components are promising biomaterials, improving the brittleness of bioactive glass and the strength of polymers. Methacrylate polymers have high potential as the organic source for hybrids since they can be produced, through controlled polymerization, with sophisticated polymer architectures that can bond to silicate networks. Previous studies showed the mechanical properties of hybrids can be modified by polymer architecture and molar mass (MM). However, biodegradability is critical if hybrids are to be used as tissue engineering scaffolds, since the templates must be remodelled by host tissue. Degradation by-products have to either completely biodegrade or be excreted by the kidneys. Enzyme, or bio-degradation is preferred to hydrolysis by water uptake as it is expected to give a more controlled degradation rate. Here, branched and star shaped poly(methyl methacrylate-co-3-(trimethoxysilyl)propyl methacrylate) (poly(MMA-co-TMSPMA)) were synthesized with disulphide based dimethacrylate (DSDMA) as a biodegradable branching agent. Biodegradability was confirmed by exposing the copolymers to glutathione, a tripeptide which is known to cleave disulphide bonds. Cleaved parts of the star polymer from the hybrid system were detected after 2 weeks of immersion in glutathione solution, and MM was under threshold of kidney filtration. The presence of the branching agent did not reduce the mechanical properties of the hybrids and bone progenitor cells attached on the hybrids in vitro. Incorporation of the DSDMA branching agent has opened more possibilities to design biodegradable methacrylate polymer based hybrids for regenerative medicine.Statement of significanceBioactive glasses can regenerate bone but are brittle. Hybrids can overcome this problem as intimate interactions between glass and polymer creates synergetic properties. Implants have previously been made with synthetic polymers that degrade by
Constantinou AP, Zhao H, McGilvery CM, et al., 2017, A Comprehensive Systematic Study on Thermoresponsive Gels: Beyond the Common Architectures of Linear Terpolymers, Nanomaterials, Vol: 9, ISSN: 2079-4991
In this study, seven thermoresponsive methacrylate terpolymers with the same molar mass (MM) and composition but various architectures were successfully synthesized using group transfer polymerization (GTP). These terpolymers were based on tri(ethylene glycol) methyl ether methacrylate (TEGMA, A unit), n-butyl methacrylate (BuMA, B unit), and 2-(dimethylamino)ethyl methacrylate (DMAEMA, C unit). Along with the more common ABC, ACB, BAC, and statistical architectures, three diblock terpolymers were also synthesized and investigated for the first time, namely (AB)C, A(BC), and B(AC); where the units in the brackets are randomly copolymerized. Two BC diblock copolymers were also synthesized for comparison. Their hydrodynamic diameters and their effective pKas were determined by dynamic light scattering (DLS) and hydrogen ion titrations, respectively. The self-assembly behavior of the copolymers was also visualized by transmission electron microscopy (TEM). Both dilute and concentrated aqueous copolymer solutions were extensively studied by visual tests and their cloud points (CP) and gel points were determined. It is proven that the aqueous solution properties of the copolymers, with specific interest in their thermoresponsive properties, are influenced by the architecture, with the ABC and A(BC) ones to show clear sol-gel transition.
Constantinou A, Zhao H, McGilvery C, et al., 2017, A comprehensive systematic study on thermoresponsive gels: beyond the common architectures of linear terpolymers, Polymers, Vol: 9, ISSN: 2073-4360
In this study, seven thermoresponsive methacrylate terpolymers with the same molar mass (MM) and composition but various architectures were successfully synthesized using group transfer polymerization (GTP). These terpolymers were based on tri(ethylene glycol) methyl ether methacrylate (TEGMA, A unit), n-butyl methacrylate (BuMA, B unit), and 2-(dimethylamino)ethyl methacrylate (DMAEMA, C unit). Along with the more common ABC, ACB, BAC, and statistical architectures, three diblock terpolymers were also synthesized and investigated for the first time, namely (AB)C, A(BC), and B(AC); where the units in the brackets are randomly copolymerized. Two BC diblock copolymers were also synthesized for comparison. Their hydrodynamic diameters and their effective pKas were determined by dynamic light scattering (DLS) and hydrogen ion titrations, respectively. The self-assembly behavior of the copolymers was also visualized by transmission electron microscopy (TEM). Both dilute and concentrated aqueous copolymer solutions were extensively studied by visual tests and their cloud points (CP) and gel points were determined. It is proven that the aqueous solution properties of the copolymers, with specific interest in their thermoresponsive properties, are influenced by the architecture, with the ABC and A(BC) ones to show clear sol-gel transition.
Lu B, Tarn MD, Pamme N, et al., 2016, Microfluidic fabrication of novel pH-responsive amphiphilic microgel for drug delivery, The 20th International Conference of Miniaturized Systems for Chemistry and Life Sciences (MicroTAS 2016), Pages: 729-730
Amphiphilic, pH-responsive microgels for drug delivery were fabricated by on-chip photopolymerisation of precursor droplets containing hydrophilic 2-(dimethylamino)ethyl methacrylate (DMAEMA) and hydrophobic n-butyl acrylate (BuA) monomers enabling efficient polymerisation and excellent control of size, crosslinking density and hydrophobic/hydrophilic ratio of the microgels.
Chung J, Li S, Stevens MM, et al., 2016, Tailoring mechanical properties of sol-gel hybrids for bone regeneration through polymer structure, Chemistry of Materials, Vol: 28, Pages: 6127-6135, ISSN: 1520-5002
Bioglass was the first synthetic biomaterial that formed a chemical bond to bone. Although bioactive glass scaffolds can mimic bone’s porous structure, they are brittle. Sol–gel derived hybrids could overcome this problem because their nanoscale conetworks of silica and organic polymer have the potential to provide unique physical properties and controlled homogeneous biodegradation. Copolymers of methyl methacrylate (MMA) and 3-(trimethoxysilyl)propyl methacrylate (TMSPMA) have been used as an organic source for hybrids to take advantage of their self-hardening property. However, the effect of well-defined poly(MMA-co-TMSPMA) architecture in the hybrid system has not been investigated. Here, linear, randomly branched, and star shaped methacrylate based copolymers were synthesized via reversible addition–fragmentation chain transfer (RAFT) polymerization method. These copolymers were then used to fabricate hybrids. The 3-D polymer structure had a significant effect on mechanical properties, providing higher strain to failure while maintaining a compressive strength similar to sol–gel glass. Star copolymer–SiO2 hybrids had a modulus of toughness 9.6-fold greater and Young’s modulus 4.5-fold lower than a sol–gel derived bioactive glass. During in vitro cell culture, MC3T3-E1 osteoblast precursor cells adhered on the surface regardless of the polymer structure. Introducing star polymers to inorganic–organic hybrids opens up possibilities for the fine-tuning physical properties of bone scaffold materials.
Lu B, Tarn MD, Pamme N, et al., 2016, Microfluidically fabricated pH-responsive anionic amphiphilic microgels for drug release, Journal of Materials Chemistry B, Vol: 4, Pages: 3086-3093, ISSN: 2050-7518
Amphiphilic microgels of different composition based on the hydrophilic, pH-responsive acrylic acid (AA) and the hydrophobic, non-ionic n-butyl acrylate (BuA) were synthesised using a lab-on-a-chip device. Hydrophobic droplets were generated via a microfluidic platform that contained a protected form of AA, BuA, the hydrophobic crosslinker, ethylene glycol dimethacrylate (EGDMA), and a free radical initiator in an organic solvent. These hydrophobic droplets were photopolymerised within the microfluidic channels and subsequently hydrolysed, enabling an integrated platform for the rapid, automated, and in situ production of anionic amphiphilic microgels. The amphiphilic microgels did not feature the conventional core–shell structure but were instead based on random amphiphilic copolymers of AA and BuA and hydrophobic crosslinks. Due to their amphiphilic nature they were able to encapsulate and deliver both hydrophobic and hydrophilic moieties. The model drug delivery and the swelling ability of the microgels were influenced by the pH of the surrounding aqueous solution and the hydrophobic content of the microgels.
D'Elia E, Eslava S, Miranda M, et al., 2016, Autonomous self-healing structural composites with bio-inspired design, Scientific Reports, Vol: 6, ISSN: 2045-2322
Strong and tough natural composites such as bone, silk or nacre are often built from stiff blocks boundtogether using thin interfacial soft layers that can also provide sacrificial bonds for self-repair. Herewe show that it is possible exploit this design in order to create self-healing structural composites byusing thin supramolecular polymer interfaces between ceramic blocks. We have built model brick-andmortarstructures with ceramic contents above 95 vol% that exhibit strengths of the order of MPa(three orders of magnitude higher than the interfacial polymer) and fracture energies that are twoorders of magnitude higher than those of the glass bricks. More importantly, these properties can befully recovered after fracture without using external stimuli or delivering healing agents. This approachdemonstrates a very promising route towards the design of strong, ideal self-healing materials able toself-repair repeatedly without degradation or external stimuli.
Georgiou T, Constantinou A, 2016, Thermoresponsive Gels based on ABC Triblock Copolymers: Effect of the Length of the PEG Side Group, Polymer Chemistry, Vol: 7, Pages: 2045-2056, ISSN: 1759-9962
In this study, one statistical and nine well-defined ABC triblock thermoresponsive terpolymers were synthesised via group transfer polymerisation (GTP). The A, B, and C blocks were based on poly(ethylene glycol) (PEG) based methacrylate , n-butyl methacrylate (BuMA), and 2-(dimethylamino)ethyl methacrylate (DMAEMA), respectively. The length of the PEG side group was varied. Specifically, three different PEG based monomers were used; methoxy di-, penta-, and nona(ethylene glycol) methacrylate (DEGMA, PEGMA, and NEGMA, respectively). Along with the length of PEG side group, the composition of the terpolymers was also systematically varied in order to investigate the effect of both these parameters on the thermoresponsive behaviour of the polymers. The molar mass (MM) and the architecture were kept the same. Their hydrodynamic diameters, the effective pKas, and the cloud points of aqueous copolymer solutions were determined by dynamic light scattering (DLS), potentiometric titrations, and visual tests, respectively. Micelle formation was observed for all the copolymers and the pKas were influenced by the hydrophobic content but not by the PEG side length. On the other hand both the composition and the PEG side chain length affected the cloud points and the sol-gel transition. In summary, it was demonstrated the sol-gel transition can be tailored by varying both the PEG length as well as the composition of the polymers.
Constantinou A, Georgiou, 2016, Tuning the Gelation of Thermoresponsive Gels, European Polymer Journal, Vol: 78, Pages: 366-375, ISSN: 1873-1945
Thermoresponsive gels are exciting polymeric materials with many biomedical applicationsin medical devices, drug delivery, tissue engineering and bio-printing. Also, they have greatpotential to be used in 3-D printing and thus in the fabrication of many different devices andmaterials. As it is crucial for the application of these gels to be able to control and tailor thegelation temperature and concentration this was the main focus and point of discussion of thisfeature article. Thus, it is discussed in detail how by varying the molar mass, composition,stereochemistry and architecture the thermoresponsive properties of these gels are altered.
Chung JJ, Jones JR, Georgiou T, 2015, Towards Hybrid Materials: Group Transfer Polymerization of 3-(Trimethoxylsilyl)propyl Methacrylate, Macromolecular Rapid Communications, Vol: 36, Pages: 1806-1809, ISSN: 1521-3927
In this study the Group Transfer Polymerization (GTP) of the functional monomer 3-(trimethoxylsilyl)propyl methacrylate (TMSPMA) is reported to produce polymers of different architectures and topologies. TMSPMA was successfully polymerized and copolymerized with GTP to produce well-defined (co)polymers that can be used to fabricate functional hybrid materials like hydrogels and films.
Chung JJ, Jones JR, Georgiou TK, 2015, Toward Hybrid Materials: Group Transfer Polymerization of 3-(Trimethoxysilyl)propyl Methacrylate, Macromolecular Rapid Communications, Vol: 36, Pages: 1806-1809, ISSN: 1521-3927
In this study, the group transfer polymerization (GTP) of the functionalmonomer 3-(trimethoxysilyl)propyl methacrylate (TMSPMA)is reported to produce polymers of different architectures andtopologies. TMSPMA is successfully polymerized and copolymerizedwith GTP to produce well-defi ned (co)polymers that canbe used to fabricate functional hybrid materials like hydrogels andfi lms.
Ghasdian N, Buzza DMA, Fletcher PDI, et al., 2015, ABC Triblock Copolymer Micelles: Spherical Versus Worm-Like Micelles Depending on the Preparation Method, MACROMOLECULAR RAPID COMMUNICATIONS, Vol: 36, Pages: 528-532, ISSN: 1022-1336
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- Citations: 18
Fleischli FD, Ghasdian N, Georgiou TK, et al., 2015, Tailoring the optical properties of poly(3-hexylthiophene) by emulsion processing using polymeric macrosurfactants, Journal of Materials Chemistry C, Vol: 3, Pages: 2065-2071, ISSN: 2050-7534
Lu B, Tarn MD, Pamme N, et al., 2015, Novel amphiphilic microgels fabricated via on-chip polymerisation, Pages: 1044-1046
We report the on-chip polymerisation of hydrophobic microgels from precursor droplets, and their downstream synthesis to pH-responsive amphiphilic microgels for drug delivery. This elegant platform offers superior control over microgel properties, including size, crosslinking density and hydrophobic/hydrophilic properties. The encapsulation and release of hydrophilic (Trypan Blue) and hydrophobic (Sudan Red) dyes based on the microgel shrinking/swelling properties was also studied.
Lu B, Tarn MD, Pamme N, et al., 2015, Tailoring pH-responsive acrylic acid microgels with hydrophobic crosslinks for drug release, JOURNAL OF MATERIALS CHEMISTRY B, Vol: 3, Pages: 4524-4529, ISSN: 2050-750X
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- Citations: 16
Georgiou TK, 2014, Star polymers for gene delivery, POLYMER INTERNATIONAL, Vol: 63, Pages: 1130-1133, ISSN: 0959-8103
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- Citations: 46
Lu B, Tarn MD, Pamme N, et al., 2014, Amphiphilic microgels from polymerisation of hydrophobic droplets - Novel microgels fabricated on-chip, Pages: 1199-1201
We report the synthesis of microgels for drug delivery via on-chip droplet generation and downstream photo-polymerization which affords control over hydrophobicity/hydrophilicity and enables the synthesis of amphiphilic microgels from hydrophobic droplets. The amphiphilic microgels were found to be effective for encapsulation and release of a hydrophobic dye (Sudan red) as an analog of a drug molecule.
Ghasdian N, Ward MA, Georgiou TK, 2014, Well-defined "clickable'' copolymers prepared <i>via</i> one-pot synthesis, CHEMICAL COMMUNICATIONS, Vol: 50, Pages: 7114-7116, ISSN: 1359-7345
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- Citations: 8
Buzza DMA, Fletcher PDI, Georgiou TK, et al., 2013, Water-in-Water Emulsions Based on Incompatible Polymers and Stabilized by Triblock Copolymers-Templated Polymersomes, LANGMUIR, Vol: 29, Pages: 14804-14814, ISSN: 0743-7463
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- Citations: 61
Ward MA, Georgiou TK, 2013, Thermoresponsive gels based on ABA triblock copolymers: Does the asymmetry matter?, JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY, Vol: 51, Pages: 2850-2859, ISSN: 0887-624X
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- Citations: 42
Ghasdian N, Church E, Cottam AP, et al., 2013, Novel "core-first" star-based quasi-model amphiphilic polymer networks, RSC ADVANCES, Vol: 3, Pages: 19070-19080, ISSN: 2046-2069
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- Citations: 15
Krasia-Christoforou T, Georgiou TK, 2013, Polymeric theranostics: using polymer-based systems for simultaneous imaging and therapy, JOURNAL OF MATERIALS CHEMISTRY B, Vol: 1, Pages: 3002-3025, ISSN: 2050-750X
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- Citations: 111
Ward MA, Georgiou TK, 2013, Multicompartment thermoresponsive gels: does the length of the hydrophobic side group matter?, POLYMER CHEMISTRY, Vol: 4, Pages: 1893-1902, ISSN: 1759-9954
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- Citations: 49
Pafiti KS, Patrickios CS, Georgiou TK, et al., 2012, Cationic star polymer siRNA transfectants interconnected with a piperazine-based cationic cross-linker, EUROPEAN POLYMER JOURNAL, Vol: 48, Pages: 1422-1430, ISSN: 0014-3057
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- Citations: 17
Rikkou-Kalourkoti M, Patrickios CS, Georgiou TK, 2012, Model Networks and Functional Conetworks, Polymer Science: A Comprehensive Reference, 10 Volume Set, Editors: Matyjaszewski, Möller, Publisher: Elsevier, Pages: 293-308
Ward MA, Georgiou TK, 2012, Thermoresponsive triblock copolymers based on methacrylate monomers: effect of molecular weight and composition, SOFT MATTER, Vol: 8, Pages: 2737-2745, ISSN: 1744-683X
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- Citations: 59
Ward MA, Georgiou TK, 2011, Thermoresponsive Polymers for Biomedical Applications, POLYMERS, Vol: 3, Pages: 1215-1242
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- Citations: 821
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