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The work describes the interactions of nanosilver (NAg) with bacterial cell envelope components at a molecular level and how this associates with the reactive oxygen species (ROS)-mediated toxicity of the nanoparticle. Major structural changes were detected in cell envelope biomolecules as a result of damages in functional moieties, such as the saccharides, amides, and phosphodiesters. NAg exposure disintegrates the glycan backbone in the major cell wall component peptidoglycan, causes complete breakdown of lipoteichoic acid, and disrupts the phosphate-amine and fatty acid groups in phosphatidylethanolamine, a membrane phospholipid. Consistent with the oxidative attacks, we propose that the observed cell envelope damages are inflicted, at least in part, by the reactive oxygen radicals being generated by the nanoparticle during its leaching process, abiotically, without cells. The cell envelope targeting, especially those on the inner membrane phospholipid, is likely to then trigger the rapid generation of lethal levels of cellular superoxide (O2•-) and hydroxyl (OH•) radicals herein seen with a model bacterium. The present study provides a better understanding of the antibacterial mechanisms of NAg, whereby ROS generation could be both the cause and consequence of the toxicity, associated with the initial cell envelope targeting by the nanoparticle.

The work describes the interactions of nanosilver (NAg) with bacterial cell envelope components at a molecular level and how this associates with the reactive oxygen species (ROS)-mediated toxicity of the nanoparticle. Major structural changes were detected in cell envelope biomolecules as a result of damages in functional moieties, such as the saccharides, amides, and phosphodiesters. NAg exposure disintegrates the glycan backbone in the major cell wall component peptidoglycan, causes complete breakdown of lipoteichoic acid, and disrupts the phosphate-amine and fatty acid groups in phosphatidylethanolamine, a membrane phospholipid. Consistent with the oxidative attacks, we propose that the observed cell envelope damages are inflicted, at least in part, by the reactive oxygen radicals being generated by the nanoparticle during its leaching process, abiotically, without cells. The cell envelope targeting, especially those on the inner membrane phospholipid, is likely to then trigger the rapid generation of lethal levels of cellular superoxide (O2•-) and hydroxyl (OH•) radicals herein seen with a model bacterium. The present study provides a better understanding of the antibacterial mechanisms of NAg, whereby ROS generation could be both the cause and consequence of the toxicity, associated with the initial cell envelope targeting by the nanoparticle.

© 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.

© 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.

© 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.

The development of therapeutic nucleic acids has led to new strategies for treating various diseases. Non-viral, synthetic nano-vectors in gene therapy have attracted increasing attention due to their low immunogenicity and low toxicity compared to viral counterparts. Due to the molecular structure of nucleic acids, they are very prone to degradation in pH sensitive biological environments. Therefore, synthetic nano-vehicles for therapeutic delivery, known as ‘nano-vectors’, need to be cleverly designed and engineered to protect and deliver appropriate therapeutic nucleic acids to the targeted sites for action. In this chapter, a brief overview of various types of therapeutic nucleic acids is first provided, followed by analysis of the synthetic nanomaterials under development as delivery systems to carry nucleic acids. The nucleic acid-encapsulated nano-vectors discussed here open a window for a new generation of nanomedicine.

The development of therapeutic nucleic acids has led to new strategies for treating various diseases. Non-viral, synthetic nano-vectors in gene therapy have attracted increasing attention due to their low immunogenicity and low toxicity compared to viral counterparts. Due to the molecular structure of nucleic acids, they are very prone to degradation in pH sensitive biological environments. Therefore, synthetic nano-vehicles for therapeutic delivery, known as ‘nano-vectors’, need to be cleverly designed and engineered to protect and deliver appropriate therapeutic nucleic acids to the targeted sites for action. In this chapter, a brief overview of various types of therapeutic nucleic acids is first provided, followed by analysis of the synthetic nanomaterials under development as delivery systems to carry nucleic acids. The nucleic acid-encapsulated nano-vectors discussed here open a window for a new generation of nanomedicine.

Cerium oxide nanoparticles (nanoceria) are effective in scavenging intracellular reactive oxygen species (ROS). In this study nanoceria synthesized by flame spray pyrolysis (dXRD = 12 nm) were functionalised with heparin via an organosilane linker, 3-aminopropyltriethoxysilane. Nanoceria were functionalised with approximately 130 heparin molecules per nanoparticle as determined by thermo gravimetric analysis. Heparin functionalised nanoceria were more effectively internalised by the human monocyte cell line, U937, and U937 cells that had been activated with phorbol 12 myristate 13-acetate (PMA) than bare nanoceria. The heparin functionalised nanoceria were also more effective in scavenging ROS than nanoceria in both activated and unactivated U937 cells. Heparin coupled nanoceria were found to be biologically active due to their ability to bind fibroblast growth factor 2 and signal through FGF receptor 1. Additionally, the heparin-coupled nanoceria, once internalised by the cells, were found to be degraded by 48 h. Together these data demonstrated that heparin enhanced the biological properties of nanoceria in terms of cellular uptake and ROS scavenging, while the nanoceria themselves were more effective at delivering heparin intracellularly than exposing cells to heparin in solution. © 2013.

Cerium oxide nanoparticles (nanoceria) are effective in scavenging intracellular reactive oxygen species (ROS). In this study nanoceria synthesized by flame spray pyrolysis (dXRD = 12 nm) were functionalised with heparin via an organosilane linker, 3-aminopropyltriethoxysilane. Nanoceria were functionalised with approximately 130 heparin molecules per nanoparticle as determined by thermo gravimetric analysis. Heparin functionalised nanoceria were more effectively internalised by the human monocyte cell line, U937, and U937 cells that had been activated with phorbol 12 myristate 13-acetate (PMA) than bare nanoceria. The heparin functionalised nanoceria were also more effective in scavenging ROS than nanoceria in both activated and unactivated U937 cells. Heparin coupled nanoceria were found to be biologically active due to their ability to bind fibroblast growth factor 2 and signal through FGF receptor 1. Additionally, the heparin-coupled nanoceria, once internalised by the cells, were found to be degraded by 48 h. Together these data demonstrated that heparin enhanced the biological properties of nanoceria in terms of cellular uptake and ROS scavenging, while the nanoceria themselves were more effective at delivering heparin intracellularly than exposing cells to heparin in solution. © 2013.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.