Polypyrrole RVC biofuel cells for powering medical implants

© 2017 IEEE. Batteries for implanted medical devices such as pacemakers typically require surgical replacement every 5 to 10 years causing stress to the patient and their families. A Biofuel cell uses two electrodes with enzymes embedded to convert sugar into electricity. To evaluate the power producing capabilities of biofuel cells to replace battery technology, polypyrrole electrodes were fabricated by compression with Glucose oxidase and Laccase. Vitreous carbon was added to increase the conductivity, whilst glutaraldehyde acted as a crosslinking molecule. A maximum open circuit potential of 558.7 mV, short circuit current of 1.09 mA and maximum power of 0.127 mW was obtained from the fuel cells. This was able to turn on a medical thermometer through a TI BQ25504 energy harvesting circuit, hence showing the powering potential for biomedical devices

Synthesis of pH-responsive and thiol-degradable hollow microspheres

Hollow microspheres were synthesized using an oil in water suspension system. The oil droplets were comprised of ethylene glycol dimethacrylate (EGDMA) and n-butyl acetate. Upon radical polymerization and gel formation, the polymer phase-separated from the solution and precipitated on the interface between water and organic solvent. The solvent n-butyl acetate was found to be crucial in the process as other solvent did not lead to hollow particles. The ratio between EGDMA and n-butyl acetate determined the structure of the microspheres with low EGDMA amounts leading to solid particles while increasing amounts of EGDMA results in bigger particles with larger shells. The crosslinking density of the microspheres could be adjusted by copolymerization of EGDMA with methyl methacrylate (MMA) or tert-butyl methacrylate (tBuMA). The latter allowed easy hydrolysis under acidic conditions to create pH-responsive hollow microspheres with methacrylic acid repeating units (MAA). Depending on the crosslinking density, the microsphere increased in size from around 75 μm in acidic conditions to more than 150 μm at high pH value creating hollow spheres that expand and collapse depending on the pH value. Replacing the stable EGDMA crosslinker with the cleavable crosslinker bis(2-methacryloyloxyethyl) disulfide (DSDMA) leads to the formation of hollow spheres held together by disulfide bridges. Degradation of hydrophobic (with MMA as comonomer) and hydrophilic (with MAA as comonomers) microspheres were tested in a reductive environment, which was simulated by the addition of thiols. While the hydrophilic hollow microspheres had a weight loss of more than 50-70% after 3 days, only 20 wt% of the hydrophobic microspheres were lost after one week. © 2013 Elsevier Ltd. All rights reserved

Retardation in RAFT polymerization: Does cross-termination occur with short radicals only?

The recently proposed model by Perrier and co-workers [J. Polym. Sci., Part A: Polym. Chem. 2009, 47, 3455 ] to account for retardation effects in dithiobenzoate-mediated reversible addition-fragmentation chain transfer (RAFT) polymerization of styrene has been tested experimentally. According to this model, retardation is caused by cross-termination of very short radicals only. Polymerizations were conducted employing a macroazoinitiator and a polymeric RAFT agent based on cumyl dithiobenzoate, thereby effectively eliminating all short radicals from the system. The results show, in basic agreement with the model, that there is very little, if any, retardation in dithiobenzoate-mediated RAFT polymerization of styrene in the absence of short radicals. © 2011 American Chemical Society

One pot synthesis of surface PEGylated core-shell microparticles by suspension polymerization with surface enrichment of Biotin/Avidin Conjugation

Core-shell microparticles that consist of poly(vinyl neodecanoate) (VND) crosslinked with poly(ethylene glycol dimethacrylate) (EGDMA) as the core and poly(ethylene glycol methacrylate) (PEGMA) (M̄n = 360 or M̄n = 526 g · mol-1) as the shell have been synthesized using suspension polymerization by a conventional free radical polymerization process. Interfacial tension and stability tests show that PEGMA acts as an amphiphilic macromonomer and is located on the oil/water interface of the suspension system, thus forming an outer layer during the polymerization. Kinetic studies of the monomers' conversion of VND, EGDMA, and PEGMA have been carried out using 1H NMR spectroscopy. EGDMA and PEGMA were found to have faster reaction rates compared to VND. Moreover, scanning electron microscopy showed that the polymerization of these particles starts from the shell and finishes towards the core. Consequently, the resulting microsphere is found to have a multi-layer structure. Biotin was covalently bound to the surface by the PEGMA hydroxy groups. Conjugation of biotin with streptavidin PE (phycoerythrin) was subsequently carried out. Confocal microscopy was used to confirm the presence of fluorescing streptavidin. The amount of avidin conjugated to the microspheres was calculated by the release of a 2-(4-hydroxyphenylazo) benzoic acid /avidin complex using UV/vis spectroscopy. One avidin molecule was found to occupy 7 nm2 on the surface of the microspheres. © 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Reversible AdditionFragmentation Chain Transfer (RAFT) polymerization in miniemulsion based on in situ surfactant generation

Reversible additionfragmentation chain transfer (RAFT) polymerization of styrene has been implemented in aqueous miniemulsion based on the in situ surfactant generation approach using oleic acid and potassium hydroxide in the absence of high energy mixing. The best results were obtained using the RAFT agent 3-benzylsulfanyl thiocarbonyl sufanylpropionic acid (BSPAC), most likely as a result of the presence of a carboxylic acid functionality in the RAFT agent that renders it surface active and thus imparts increased colloidal stability. Stable final miniemulsions were obtained with no coagulum with particle diameters less than 200nm. The results demonstrate that the RAFT miniemulsion polymerization of styrene employing the low energy in situ surfactant method is challenging, but that a system that proceeds predominantly by a miniemulsion mechanism can be achieved under carefully selected conditions. © 2011 CSIRO

Miniemulsion polymerization based on in situ surfactant formation without high-energy homogenization: Effects of organic acid and counter ion

Miniemulsion polymerization of styrene based on the in situ surfactant-generation technique has been investigated for a range of carboxylic acids and counterions. This technique relies on in situ formation of the surfactant at the oil-water interface and circumvents the use of traditional high-energy mixing (for example, ultrasonication) for generation of the initial miniemulsion. Miniemulsion polymerizations have been conducted successfully using the carboxylic acids lauric acid, palmitic acid and oleic acid, respectively. Coagulation/phase separation was not observed and the number-average particle diameters were < 100 nm. The counterions K +, Na + and Li + were investigated in combination with five different carboxylic acids (all permutations), revealing that satisfactory miniemulsion formation/stability could only be obtained with K +. Results of miniemulsion polymerizations conducted in the presence of an aqueous-phase radical scavenger were consistent with predominant monomer droplet nucleation. Use of the corresponding preformed surfactants added to the aqueous phase, without high-energy mixing, did not result in sufficiently stable initial (before polymerization) miniemulsions. © 2012 The Society of Polymer Science, Japan (SPSJ) All rights reserved

Size-tunable nanoparticle synthesis by RAFT polymerization in CO <inf>2</inf>-induced miniemulsions

A novel environmentally friendly low-energy emulsification method that relies on pressurization with CO 2 to low pressure has been applied to reversible addition-fragmentation chain transfer (RAFT) polymerization of styrene-in-water miniemulsions with the anionic surfactant Dowfax 8390. This method circumvents traditional high-energy homogenization, and over a certain CO 2 pressure range, a transparent miniemulsion is formed. RAFT polymerization of styrene using benzyldodecyl trithiocarbonate and the aqueous phase initiator VA-044 was carried out successfully in CO 2-induced miniemulsions at 50 °C with good control/livingness. Interestingly, the particle size could be conveniently tuned via the CO 2 pressure without altering the recipe, with 6.00, 6.50, and 7.50 MPa generating number-average particle diameters of 98, 89, and 48 nm, respectively, at ∼70% conversion. The smallest particle size corresponded to the pressure range within which the emulsion was transparent. © 2012 American Chemical Society

Acetyl-α-d-mannopyranose-based cationic polymer via RAFT polymerization for lectin and nucleic acid bindings

© 2017 Wiley Periodicals, Inc. Functional cationic polymers carrying mannose moieties were synthesized in a facile manner by employing RAFT polymerization. Initially, a protected carbohydrate based monomer, [2-(2,3,4,6-tetra-O-acetyl-α-d-mannopyranosyloxy)ethyl methacrylate (AcManEMA)], was prepared by the O-glycosylation of 2-hydroxyethyl methacrylate (HEMA). Subsequently, a macroRAFT agent of poly[2-(dimethyl)amino ethyl methacrylate] (PDMAEMA) was generated, and a further chain extension polymerization with AcManEMA was carried out in dioxane to form a acetylated mannose cationic diblock copolymer, PDMAEMA-b-PAcManEMA. It was attained in high yields and displayed low dispersity (Ð). Acetylated mannose moieties on the polymer were deprotected with sodium methoxide and the amines from the DMAEMA block were protonated to yield a cationic diblock glycopolymer, PDMAEMA-b-PManEMA. The cationic property of polymers were characterized by mixing with a negatively charged siRNA duplex and a pDNA, and aggregates of 102 and 233 nm were obtained, respectively. Agarose gel shift assay revealed that the polymers were able to retain the nucleic acids as large polymer complexes. Lectin binding assay proved that the mannose residue on the polymers were only able to bind specifically with ConA. PNA lectin was employed as a control and did not show specific binding. The cationic glycopolymer could be advantageous in targeted nucleic acids delivery in specific cells. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44947

Controlled/Living ab initio emulsion polymerization via a glucose raft stab: Degradable cross-linked glyco-particles for concanavalin A/ Fim H conjugations to cluster E. Coli bacteria

Glyco-particles bearing glucose units have been prepared via a one-step controlled/living ab initio cross-linking emulsion polymerization of styrene based on self-assembly via a glucose RAFTstab (reversible addition - fragmentation chain transfer colloidal stabilizer). The RAFTstab was synthesized from the monomer 2-(methacrylamido)glucopyranose (MAG) and the hydrophobic trithiocarbonate RAFT agent S-methoxycarbonylphenylmethyl dodecyltrithiocarbonate (MCPDT). In order to obtain glyco-particles stable for biomedical applications, a degradable bis(2-acryloyloxyethyl) disulfide cross-linker (disulfide diacrylate, DSDA) was employed in the emulsion polymerization. The cross-linked glyco-particles were stable in N,N-dimethylacetamide (DMAc), in contrast to the corresponding non-cross-linked glyco-particles which disintegrate to form linear glycopolymers in solution. The cross-linked particles underwent reductive degradation into the constituent linear (primary) chains upon treatment with 1,4-dithiothreitol (DDT). The bioactivity of the glucose moieties on the surface of the particles was examined using two classes of lectins, namely plant lectin (Concanavalin A, Canavalia ensiformis) and bacteria lectin (fimH, from Escherichia coli). Successful binding was demonstrated, thus illustrating that these particles have potential as smart materials in biological systems. © 2010 American Chemical Society