Ahmed Aied - Academia.edu (original) (raw)

Papers by Ahmed Aied

Journal of Biotechnology, Jul 1, 2013

Minicircle (MC) DNA vectors have shown prolonged expression in gene transfection studies. Here we... more Minicircle (MC) DNA vectors have shown prolonged expression in gene transfection studies. Here we have developed a facile approach based on enzyme-catalyzed reactions to produce the MC DNA in vitro. eGFP plasmid was inserted by two mirror-symmetry pairs of EcoRV and HindIII restriction enzyme sites at both sides of the expression cassette. The highly purified eGFP MC DNA vector was obtained through a dephosphorylating/re-exposing process, followed by a selective ligation of MC DNA and selective removal of the bacterial backbone fragment. The GFP expression study showed a significant improvement by using MC vectors. This method mimics the recombination process in vitro, avoids the need for specific bacterial strains, strict inducing strategy and complex purification approach, which provides potential for manufacturing the high-quality minicircle DNA vectors for vaccination and gene therapy applications.

Biomacromolecules, Nov 20, 2014

Polymer-based transfection vectors are increasingly becoming the preferred alternative to viral v... more Polymer-based transfection vectors are increasingly becoming the preferred alternative to viral vectors thanks to their safety and ease of production, but low transfection potency has limited their application. Many polycationic vectors show high efficiency in vitro, but their excessive charge density makes them toxic for in vivo applications. Herein, we demonstrate the synthesis of new and unique disulfide-reducible polymeric gene nano-carriers that exhibit significantly enhanced transfection potency and low cytotoxicity, particularly in skin cells, surpassing the efficiency of the well-known transfection reagents Polyethylenimine (PEI) and Lipofectamine®2000. The unique 3D 'multi-knot' vectors were synthesized from in situ deactivation enhanced atom transfer radical (co-)polymerization (DE-ATRP) of multivinyl monomers (MVMs). The high transfection levels and low toxicity of this multi-knot structured polymer in vitro, combined with its ability to mediate Page 1 of 27 ACS Paragon Plus Environment Biomacromolecules collagen VII expression in 3D skin equivalents made from cells of Recessive dystrophic Epidermolysis Bullosa patients, demonstrates its use as a platform nanotechnology which should be investigated further for dermatological disease therapies. Our findings suggest that the marked improvements stem from the dense multi-knot architecture and degradable property, which facilitate both the binding and releasing process of the plasmid DNA.

Bioprinting, Mar 1, 2018

Synthetic polymers possess more reproducible physical and chemical properties than their naturall... more Synthetic polymers possess more reproducible physical and chemical properties than their naturally occurring counterparts. They have also emerged as an important alternative for fabricating tissue substitutes because they can be molecularly tailored to have vast array of molecular weights, block structures, active functional groups, and mechanical properties. To this date however, there has been very few successful and fully functional synthetic tissue and organ substitutes and with the rapidly spreading 3D printing technology beginning to reshape the tissue engineering and regenerative field, the need for an effective, safe, and bio printable biomaterial is becoming more and more urgent. Here, we have developed a synthetic polymer from controlled living radical polymerization that can be printed into well-defined structures. The polymer showed low cytotoxicity before and after printing. Additionally, the incorporation of gelatine-methacrylate coated PLGA microparticles within the hydrogel provided cell adhesion surfaces for cell proliferation. The results point to possible application of the microparticle seeded, synthetic hydrogel as a direct printable tissue or organ substitute.

Bioprinting, 2018

Synthetic polymers possess more reproducible physical and chemical properties than their naturall... more Synthetic polymers possess more reproducible physical and chemical properties than their naturally occurring counterparts. They have also emerged as an important alternative for fabricating tissue substitutes because they can be molecularly tailored to have vast array of molecular weights, block structures, active functional groups, and mechanical properties. To this date however, there has been very few successful and fully functional synthetic tissue and organ substitutes and with the rapidly spreading 3D printing technology beginning to reshape the tissue engineering and regenerative field, the need for an effective, safe, and bio printable biomaterial is becoming more and more urgent. Here, we have developed a synthetic polymer from controlled living radical polymerization that can be printed into well-defined structures. The polymer showed low cytotoxicity before and after printing. Additionally, the incorporation of gelatine-methacrylate coated PLGA microparticles within the hydrogel provided cell adhesion surfaces for cell proliferation. The results point to possible application of the microparticle seeded, synthetic hydrogel as a direct printable tissue or organ substitute.

Journal of controlled release : official journal of the Controlled Release Society, Dec 8, 2016

Poly(β-amino ester)s (PAEs) have emerged as a promising class of gene delivery vectors with perfo... more Poly(β-amino ester)s (PAEs) have emerged as a promising class of gene delivery vectors with performances that can even be compared to viruses. However, all of the transfection studies (over 2350 PAEs) have been limited to linear poly(β-amino ester)s (LPAEs) despite increasing evidence that polymer structure significantly affects performance. Herein, we describe the development of highly branched poly(β-amino ester)s (HPAEs) via a new "A2+B3+C2" Michael addition approach demonstrating 2 to 126-fold higher in vitro transfection efficiencies of different cell types in comparison to their linear LPAE counterparts as well as greatly out-performing the leading transfection reagents SuperFect and the "gold-standard" polyethyleneimine (PEI) - especially on skin epidermal cells. More importantly, the ability to correct a skin genetic defect is demonstrated in vivo utilizing a recessive dystrophic epidermolysis bullosa (RDEB) knockout mouse model. Our results provide evide...

Biomaterials Science, 2016

A knot polymer, poly[bis(2-acryloyl)oxyethyl disulphide-co-2-(dimethylamino) ethyl methacrylate] ... more A knot polymer, poly[bis(2-acryloyl)oxyethyl disulphide-co-2-(dimethylamino) ethyl methacrylate] (DSP), was synthesized, optimized and evaluated as a non-viral vector for gene transfection for skin cells, keratinocytes.

Angewandte Chemie International Edition in English

Biomacromolecules, 2014

Polymer-based transfection vectors are increasingly becoming the preferred alternative to viral v... more Polymer-based transfection vectors are increasingly becoming the preferred alternative to viral vectors thanks to their safety and ease of production, but low transfection potency has limited their application. Many polycationic vectors show high efficiency in vitro, but their excessive charge density makes them toxic for in vivo applications. Herein, we demonstrate the synthesis of new and unique disulfide-reducible polymeric gene nano-carriers that exhibit significantly enhanced transfection potency and low cytotoxicity, particularly in skin cells, surpassing the efficiency of the well-known transfection reagents Polyethylenimine (PEI) and Lipofectamine®2000. The unique 3D 'multi-knot' vectors were synthesized from in situ deactivation enhanced atom transfer radical (co-)polymerization (DE-ATRP) of multivinyl monomers (MVMs). The high transfection levels and low toxicity of this multi-knot structured polymer in vitro, combined with its ability to mediate Page 1 of 27 ACS Paragon Plus Environment Biomacromolecules collagen VII expression in 3D skin equivalents made from cells of Recessive dystrophic Epidermolysis Bullosa patients, demonstrates its use as a platform nanotechnology which should be investigated further for dermatological disease therapies. Our findings suggest that the marked improvements stem from the dense multi-knot architecture and degradable property, which facilitate both the binding and releasing process of the plasmid DNA.

Chemical communications (Cambridge, England), Jan 21, 2014

An acid labile branched PDMAEMA/acetal copolymer with amino group was synthesized by the DE-ATRP ... more An acid labile branched PDMAEMA/acetal copolymer with amino group was synthesized by the DE-ATRP and followed by Michael addition. The degradation of the polymer was strongly pH-dependent. High nucleic acid transfection efficiency with low cytotoxicity was observed compared to its non-degradable copolymer counterpart.

Angewandte Chemie (International ed. in English), Jan 10, 2014

A series of degradable branched PDMAEMA copolymers were investigated with the linear PDMAEMA coun... more A series of degradable branched PDMAEMA copolymers were investigated with the linear PDMAEMA counterpart as gene-delivery vectors. The branched PDMAEMA copolymers were synthesized by controlled radical cross-linking copolymerization based on the "vinyl oligomer combination" approach. Efficient degradation properties were observed for all of the copolymers. The degree of branching was found to have a big impact on performance in transfection when tested on different cell types. The product with the highest degree of branching and highest degree of functionality had a superior transfection profile in terms of both transfection capability and the preservation of cell viability. These branched PDMAEMA copolymers show high potential for gene-delivery applications through a combination of the simplicity of their synthesis, their low toxicity, and their high performance.

Polym. Chem., 2012

A hyperbranched polymer synthesised from DE-ATRP and labelled with Rhodamine B was used to detect... more A hyperbranched polymer synthesised from DE-ATRP and labelled with Rhodamine B was used to detect DNA hybridisation in serum.

Nanoscale, 2014

A cationic knot structured transfection vector showed a more favorable transfection profile for a... more A cationic knot structured transfection vector showed a more favorable transfection profile for a neural cell type compared to other polyplexes whilst maintaining cell viability at over 80% after four days of culture and could mediate luciferase overexpression in the adult brain.

Journal of Controlled Release, 2013

Despite the widespread use of drug eluting stents (DES), in-stent restenosis (ISR), delayed arter... more Despite the widespread use of drug eluting stents (DES), in-stent restenosis (ISR), delayed arterial healing and thrombosis remain important clinical complications. Gene-eluting stents (GES) represent a potential strategy for the prevention of ISR by delivering a therapeutic gene via a vector from the stent surface to the vessel wall. To this end, a model in vitro system was established to examine whether cationic liposomes could be used for gene delivery to human artery cells. Three different formulations were compared (DOTMA/ DOPE, DDAB/DOPE or DDAB/POPC/Chol) to examine the effects of different cationic and neutral lipids on the transfection efficiency of lipoplex-coatings of metal surfaces. Upon completion of the characterization and optimization of the materials for gene delivery in vitro, these coatings were examined on a range of stents and deployed in a rabbit iliac artery injury model in vivo. Maximal transfection efficiencies for all coatings were observed on day 28, followed by declining, but persisting gene expression 42 days after stent placement, thereby, presenting liposomal coatings for gene eluting stents as treatment options for clinical complications associated with stenting procedures.

Journal of Biotechnology, 2013

Minicircle (MC) DNA vectors have shown prolonged expression in gene transfection studies. Here we... more Minicircle (MC) DNA vectors have shown prolonged expression in gene transfection studies. Here we have developed a facile approach based on enzyme-catalyzed reactions to produce the MC DNA in vitro. eGFP plasmid was inserted by two mirror-symmetry pairs of EcoRV and HindIII restriction enzyme sites at both sides of the expression cassette. The highly purified eGFP MC DNA vector was obtained through a dephosphorylating/re-exposing process, followed by a selective ligation of MC DNA and selective removal of the bacterial backbone fragment. The GFP expression study showed a significant improvement by using MC vectors. This method mimics the recombination process in vitro, avoids the need for specific bacterial strains, strict inducing strategy and complex purification approach, which provides potential for manufacturing the high-quality minicircle DNA vectors for vaccination and gene therapy applications.

Drug Discovery Today, 2013

Recent progress in gene therapy has opened doors for the development of new and multifunctional d... more Recent progress in gene therapy has opened doors for the development of new and multifunctional delivery agents based on the tailored synthesis of polymers. These polymers are in their infancy compared with viral agents, which have been optimised during millions of years of evolution, making viral vectors naturally efficient transfection agents. To improve the efficiency of polymer gene delivery to the level seen in viral vectors, it is necessary to understand the challenges faced by polymer gene delivery vectors both in vitro and in vivo. In this review, we analyse and discuss those obstacles that scientists have to overcome to design a highly efficient synthetic transfection agent.

ACS Applied Materials & Interfaces, 2012

Cationic polymers with various structures have been widely investigated in the areas of medical d... more Cationic polymers with various structures have been widely investigated in the areas of medical diagnostics and molecular biology because of their unique binding properties and capability to interact with biological molecules in complex biological environments. In this work, we report the grafting of a linear cationic polymer from an atom transfer radical polymerization (ATRP) initiator bound to cellulose paper surface. We show successful binding of ATRP initiator onto cellulose paper and grafting of polymer chains from the immobilized initiator with ATRP. The cellulose paper grafted polymer was used in combination with PicoGreen (PG) to demonstrate detection of nucleic acids in the nanogram range in homogeneous solution and in a biological sample (serum). The results showed specific identification of hybridized DNA after addition of PG in both solutions.

Journal of Biotechnology, Jul 1, 2013

Minicircle (MC) DNA vectors have shown prolonged expression in gene transfection studies. Here we... more Minicircle (MC) DNA vectors have shown prolonged expression in gene transfection studies. Here we have developed a facile approach based on enzyme-catalyzed reactions to produce the MC DNA in vitro. eGFP plasmid was inserted by two mirror-symmetry pairs of EcoRV and HindIII restriction enzyme sites at both sides of the expression cassette. The highly purified eGFP MC DNA vector was obtained through a dephosphorylating/re-exposing process, followed by a selective ligation of MC DNA and selective removal of the bacterial backbone fragment. The GFP expression study showed a significant improvement by using MC vectors. This method mimics the recombination process in vitro, avoids the need for specific bacterial strains, strict inducing strategy and complex purification approach, which provides potential for manufacturing the high-quality minicircle DNA vectors for vaccination and gene therapy applications.

Biomacromolecules, Nov 20, 2014

Polymer-based transfection vectors are increasingly becoming the preferred alternative to viral v... more Polymer-based transfection vectors are increasingly becoming the preferred alternative to viral vectors thanks to their safety and ease of production, but low transfection potency has limited their application. Many polycationic vectors show high efficiency in vitro, but their excessive charge density makes them toxic for in vivo applications. Herein, we demonstrate the synthesis of new and unique disulfide-reducible polymeric gene nano-carriers that exhibit significantly enhanced transfection potency and low cytotoxicity, particularly in skin cells, surpassing the efficiency of the well-known transfection reagents Polyethylenimine (PEI) and Lipofectamine®2000. The unique 3D 'multi-knot' vectors were synthesized from in situ deactivation enhanced atom transfer radical (co-)polymerization (DE-ATRP) of multivinyl monomers (MVMs). The high transfection levels and low toxicity of this multi-knot structured polymer in vitro, combined with its ability to mediate Page 1 of 27 ACS Paragon Plus Environment Biomacromolecules collagen VII expression in 3D skin equivalents made from cells of Recessive dystrophic Epidermolysis Bullosa patients, demonstrates its use as a platform nanotechnology which should be investigated further for dermatological disease therapies. Our findings suggest that the marked improvements stem from the dense multi-knot architecture and degradable property, which facilitate both the binding and releasing process of the plasmid DNA.

Bioprinting, Mar 1, 2018

Synthetic polymers possess more reproducible physical and chemical properties than their naturall... more Synthetic polymers possess more reproducible physical and chemical properties than their naturally occurring counterparts. They have also emerged as an important alternative for fabricating tissue substitutes because they can be molecularly tailored to have vast array of molecular weights, block structures, active functional groups, and mechanical properties. To this date however, there has been very few successful and fully functional synthetic tissue and organ substitutes and with the rapidly spreading 3D printing technology beginning to reshape the tissue engineering and regenerative field, the need for an effective, safe, and bio printable biomaterial is becoming more and more urgent. Here, we have developed a synthetic polymer from controlled living radical polymerization that can be printed into well-defined structures. The polymer showed low cytotoxicity before and after printing. Additionally, the incorporation of gelatine-methacrylate coated PLGA microparticles within the hydrogel provided cell adhesion surfaces for cell proliferation. The results point to possible application of the microparticle seeded, synthetic hydrogel as a direct printable tissue or organ substitute.

Bioprinting, 2018

Synthetic polymers possess more reproducible physical and chemical properties than their naturall... more Synthetic polymers possess more reproducible physical and chemical properties than their naturally occurring counterparts. They have also emerged as an important alternative for fabricating tissue substitutes because they can be molecularly tailored to have vast array of molecular weights, block structures, active functional groups, and mechanical properties. To this date however, there has been very few successful and fully functional synthetic tissue and organ substitutes and with the rapidly spreading 3D printing technology beginning to reshape the tissue engineering and regenerative field, the need for an effective, safe, and bio printable biomaterial is becoming more and more urgent. Here, we have developed a synthetic polymer from controlled living radical polymerization that can be printed into well-defined structures. The polymer showed low cytotoxicity before and after printing. Additionally, the incorporation of gelatine-methacrylate coated PLGA microparticles within the hydrogel provided cell adhesion surfaces for cell proliferation. The results point to possible application of the microparticle seeded, synthetic hydrogel as a direct printable tissue or organ substitute.

Journal of controlled release : official journal of the Controlled Release Society, Dec 8, 2016

Poly(β-amino ester)s (PAEs) have emerged as a promising class of gene delivery vectors with perfo... more Poly(β-amino ester)s (PAEs) have emerged as a promising class of gene delivery vectors with performances that can even be compared to viruses. However, all of the transfection studies (over 2350 PAEs) have been limited to linear poly(β-amino ester)s (LPAEs) despite increasing evidence that polymer structure significantly affects performance. Herein, we describe the development of highly branched poly(β-amino ester)s (HPAEs) via a new "A2+B3+C2" Michael addition approach demonstrating 2 to 126-fold higher in vitro transfection efficiencies of different cell types in comparison to their linear LPAE counterparts as well as greatly out-performing the leading transfection reagents SuperFect and the "gold-standard" polyethyleneimine (PEI) - especially on skin epidermal cells. More importantly, the ability to correct a skin genetic defect is demonstrated in vivo utilizing a recessive dystrophic epidermolysis bullosa (RDEB) knockout mouse model. Our results provide evide...

Biomaterials Science, 2016

A knot polymer, poly[bis(2-acryloyl)oxyethyl disulphide-co-2-(dimethylamino) ethyl methacrylate] ... more A knot polymer, poly[bis(2-acryloyl)oxyethyl disulphide-co-2-(dimethylamino) ethyl methacrylate] (DSP), was synthesized, optimized and evaluated as a non-viral vector for gene transfection for skin cells, keratinocytes.

Angewandte Chemie International Edition in English

Biomacromolecules, 2014

Polymer-based transfection vectors are increasingly becoming the preferred alternative to viral v... more Polymer-based transfection vectors are increasingly becoming the preferred alternative to viral vectors thanks to their safety and ease of production, but low transfection potency has limited their application. Many polycationic vectors show high efficiency in vitro, but their excessive charge density makes them toxic for in vivo applications. Herein, we demonstrate the synthesis of new and unique disulfide-reducible polymeric gene nano-carriers that exhibit significantly enhanced transfection potency and low cytotoxicity, particularly in skin cells, surpassing the efficiency of the well-known transfection reagents Polyethylenimine (PEI) and Lipofectamine®2000. The unique 3D 'multi-knot' vectors were synthesized from in situ deactivation enhanced atom transfer radical (co-)polymerization (DE-ATRP) of multivinyl monomers (MVMs). The high transfection levels and low toxicity of this multi-knot structured polymer in vitro, combined with its ability to mediate Page 1 of 27 ACS Paragon Plus Environment Biomacromolecules collagen VII expression in 3D skin equivalents made from cells of Recessive dystrophic Epidermolysis Bullosa patients, demonstrates its use as a platform nanotechnology which should be investigated further for dermatological disease therapies. Our findings suggest that the marked improvements stem from the dense multi-knot architecture and degradable property, which facilitate both the binding and releasing process of the plasmid DNA.

Chemical communications (Cambridge, England), Jan 21, 2014

An acid labile branched PDMAEMA/acetal copolymer with amino group was synthesized by the DE-ATRP ... more An acid labile branched PDMAEMA/acetal copolymer with amino group was synthesized by the DE-ATRP and followed by Michael addition. The degradation of the polymer was strongly pH-dependent. High nucleic acid transfection efficiency with low cytotoxicity was observed compared to its non-degradable copolymer counterpart.

Angewandte Chemie (International ed. in English), Jan 10, 2014

A series of degradable branched PDMAEMA copolymers were investigated with the linear PDMAEMA coun... more A series of degradable branched PDMAEMA copolymers were investigated with the linear PDMAEMA counterpart as gene-delivery vectors. The branched PDMAEMA copolymers were synthesized by controlled radical cross-linking copolymerization based on the "vinyl oligomer combination" approach. Efficient degradation properties were observed for all of the copolymers. The degree of branching was found to have a big impact on performance in transfection when tested on different cell types. The product with the highest degree of branching and highest degree of functionality had a superior transfection profile in terms of both transfection capability and the preservation of cell viability. These branched PDMAEMA copolymers show high potential for gene-delivery applications through a combination of the simplicity of their synthesis, their low toxicity, and their high performance.

Polym. Chem., 2012

A hyperbranched polymer synthesised from DE-ATRP and labelled with Rhodamine B was used to detect... more A hyperbranched polymer synthesised from DE-ATRP and labelled with Rhodamine B was used to detect DNA hybridisation in serum.

Nanoscale, 2014

A cationic knot structured transfection vector showed a more favorable transfection profile for a... more A cationic knot structured transfection vector showed a more favorable transfection profile for a neural cell type compared to other polyplexes whilst maintaining cell viability at over 80% after four days of culture and could mediate luciferase overexpression in the adult brain.

Journal of Controlled Release, 2013

Despite the widespread use of drug eluting stents (DES), in-stent restenosis (ISR), delayed arter... more Despite the widespread use of drug eluting stents (DES), in-stent restenosis (ISR), delayed arterial healing and thrombosis remain important clinical complications. Gene-eluting stents (GES) represent a potential strategy for the prevention of ISR by delivering a therapeutic gene via a vector from the stent surface to the vessel wall. To this end, a model in vitro system was established to examine whether cationic liposomes could be used for gene delivery to human artery cells. Three different formulations were compared (DOTMA/ DOPE, DDAB/DOPE or DDAB/POPC/Chol) to examine the effects of different cationic and neutral lipids on the transfection efficiency of lipoplex-coatings of metal surfaces. Upon completion of the characterization and optimization of the materials for gene delivery in vitro, these coatings were examined on a range of stents and deployed in a rabbit iliac artery injury model in vivo. Maximal transfection efficiencies for all coatings were observed on day 28, followed by declining, but persisting gene expression 42 days after stent placement, thereby, presenting liposomal coatings for gene eluting stents as treatment options for clinical complications associated with stenting procedures.

Journal of Biotechnology, 2013

Minicircle (MC) DNA vectors have shown prolonged expression in gene transfection studies. Here we... more Minicircle (MC) DNA vectors have shown prolonged expression in gene transfection studies. Here we have developed a facile approach based on enzyme-catalyzed reactions to produce the MC DNA in vitro. eGFP plasmid was inserted by two mirror-symmetry pairs of EcoRV and HindIII restriction enzyme sites at both sides of the expression cassette. The highly purified eGFP MC DNA vector was obtained through a dephosphorylating/re-exposing process, followed by a selective ligation of MC DNA and selective removal of the bacterial backbone fragment. The GFP expression study showed a significant improvement by using MC vectors. This method mimics the recombination process in vitro, avoids the need for specific bacterial strains, strict inducing strategy and complex purification approach, which provides potential for manufacturing the high-quality minicircle DNA vectors for vaccination and gene therapy applications.

Drug Discovery Today, 2013

Recent progress in gene therapy has opened doors for the development of new and multifunctional d... more Recent progress in gene therapy has opened doors for the development of new and multifunctional delivery agents based on the tailored synthesis of polymers. These polymers are in their infancy compared with viral agents, which have been optimised during millions of years of evolution, making viral vectors naturally efficient transfection agents. To improve the efficiency of polymer gene delivery to the level seen in viral vectors, it is necessary to understand the challenges faced by polymer gene delivery vectors both in vitro and in vivo. In this review, we analyse and discuss those obstacles that scientists have to overcome to design a highly efficient synthetic transfection agent.

ACS Applied Materials & Interfaces, 2012

Cationic polymers with various structures have been widely investigated in the areas of medical d... more Cationic polymers with various structures have been widely investigated in the areas of medical diagnostics and molecular biology because of their unique binding properties and capability to interact with biological molecules in complex biological environments. In this work, we report the grafting of a linear cationic polymer from an atom transfer radical polymerization (ATRP) initiator bound to cellulose paper surface. We show successful binding of ATRP initiator onto cellulose paper and grafting of polymer chains from the immobilized initiator with ATRP. The cellulose paper grafted polymer was used in combination with PicoGreen (PG) to demonstrate detection of nucleic acids in the nanogram range in homogeneous solution and in a biological sample (serum). The results showed specific identification of hybridized DNA after addition of PG in both solutions.