Ahmed Aied

Polymer gene delivery: overcoming the obstacles

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.

DNA Immobilization and Detection on Cellulose Paper using a Surface Grown Cationic Polymer via ATRP

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.

A fluorescently labeled, hyperbranched polymer synthesized from DE-ATRP for the detection of DNA hybridization

The early detection of oligonucleotide biomarkers of disease, such as microRNAs, has been established as a fundamental factor in cancer diagnosis. As the levels of these small molecules (microRNAs) in blood have recently been found to be significantly affected in cancer patients, they offer a means of early stage detection of cancer. Towards the goal of creating a novel method of DNA hybridization detection, we report the detection of specific sequences of small oligonucleotides in a model experiment carried out in serum. The results shown here display the versatility of the DE-ATRP method in synthesizing a specific polymer structure capable of changing its physical properties in the presence of double stranded DNA. The polymer was labeled and used to detect single-stranded DNA in serum successfully.

Liposomal surface coatings of metal stents for efficient non-viral gene delivery to the injured vasculature

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.

An in vitro approach for production of non-scar minicircle DNA vectors

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.