Current Research

• Macromolecular design and engineering via controlled/living polymerisation techniques (including ATRP, RAFT, ROP and anionic polymerisation) and click chemistry

• Functional nanomaterials - knot and/or dendritic polymers as multifunctional carriers for targeted therapeutic drugs (proteins and peptides) and DNA/RNA delivery

• Skin gene therapy and the development of new DNA plasmid vectors

• Bio-inspired responsive polymers as dressing/adhesive for wound healing

• Injectable ECM biopolymer hybrid hydrogels for Stem cells encapsulation and delivery

• 3D Bio-printing

• Clinical targets: Gene therapy for RDEB, Skin wound healing, Cardiovascular disease

Current Research Group

• Supervise 6 Postdoctoral researchers, 12 Ph.D students

Research Areas

Deactivation-Enhanced Atom Transfer Radical Polymerisation (DE-ATRP)

In 2007, Prof Wenxin Wang discovered a completely new concept leading to a facile synthetic route towards dendritic structures. Since then, he has been continually working on the development of this new approach for the design and preparation of functional polymeric materials for applied applications. The breakthrough in this novel synthetic approach has been to realize that by precisely controlling the competition between chain growth and reversible chain termination, the polymers can grow slowly and effectively while branching is introduced by the multi-functional vinyl monomers in a controlled fashion and the cross linking reaction is delayed. This new concept has been demonstrated by the successful polymerisation of 100% multi-vinyl monomers (MVMs) e.g. ethylene glycol dimethacrylate (EGDMA) with good control over the molecular weight and chain structure (1). This is a significant achievement on polymer synthesis. It allows use of readily available multifunctional vinyl monomers as branching agent for the synthesis of novel dendritic polymers. We believe that this novel synthetic approach can be applied to yield high value dendritic polymers that can have many topical applications such as in the area of nanotechnology and drug delivery.

‘Celtic Knot’ polymer

Controlled/living radical polymerisation (CRP) is a widely used technique that allows the synthesis of defined polymer architectures through precise control of molecular weights and distributions. The architectures of polymers prepared by the CRP techniques are reported to be the linear, crosslinked, branched/dendritic structures. Recently, we have prepared a new 3D single cyclized polymer chain structure from an in situ deactivation enhanced atom transfer radical polymerisation of multi-vinyl monomers (MVMs), which are conventionally used for the production of branched/crosslinked polymeric material as defined by P. Flory and W. Stockmayer 70 years ago. Prof Wenxin Wang has provided new evidence to show that it is possible to kinetically control both the macromolecular architecture and the critical gelling point in the polymerisation of MVMs, suggesting the classical Flory-Stockmayer mean field theory should be supplemented with a new kinetic theory based on the space and instantaneous growth boundary concept.

Prof Wenxin Wang has demonstrated that it is possible to kinetically control both the macromolecular architecture and the critical gel point in the polymerisation of MVMs, which is beyond the scope of F-S theory. This new kinetically controlled approach allows the preparation of a new 3D ‘Celtic Knot’ polymeric material which is distinct from the definition of conventional dendritic/hyperbranched and crosslinked materials. It can be expected that the ability and understanding to control intramolecular cyclization within polymer structures for the polymerisation of MVMs will be proved to be a revolutionary concept in the field of polymer science. The broad range of novel nanosize 3D polymeric materials that can be designed and produced from the numerous available multivinyl monomers, will have significant applications in a wide range of different fields. (2)

Development of minicircle DNA vectors

Minicircle (MC) DNA vectors are small circular sequences of DNA similar to plasmids but devoid of any bacterial sequences, such as an origin of replication and antibiotic resistance genes. MCs could be considered the second-generation of DNA vectors, they have shown promising applications in clinical gene therapy. These vectors have been used since 1997 (Draquet et al) in preclinical gene transfer research because of their 10- to 1,000-fold enhancement of gene translation. Compared with regular plasmids in vivo in quiescent tissues, they have also performed favorably for long term transgene expression (Chen et al 2003). Our group is currently developing a minicircle vector to carry wound healing gene. We are developing a new method to remove any bacterial DNA sequences from the backbone and to achieve the minimum possible circular DNA size. 

We hope that via the combination of minimizing the DNA size and removing the bacterial sequences that could cause an immune reaction, these MCs will achieve a longer lasting transgene expression in vivo and provide an excellent tool for our translational research.(3-4)

Responsive Smart Hydrogel for Wound Healing

Skin substitutes have been widely used for wound healing and wound closure applications. A number of skin substitute products are commercially available and can be used for different types of wounds based on their components. The mechanisms by which skin substitutes aid wound healing are not completely understood, but they may provide maintenance of a biologically balanced moist wound environment, structural support for tissue regeneration and supply of beneficial cytokines and growth factors to the wound.
Among these devices, cellular skin substitutes represent the most advanced and closely mimic native skin tissue, they are composed of a scaffold structure seeded with living cells that synthesize proteins or other extracellular matrix components to stimulate host cells and promote the healing process. Meanwhile, recent studies have reported that Adipose Tissue Derived Stem Cells (ADSCs) greatly accelerate the wound healing process by regulation of growth factors and cytokines such as platelet-derived growth factor (PDGF), insulin-like growth factor (IGF) and keratinocyte growth factor (KGF). Therefore, the aim of this project is to develop an in situ crosslinking hybrid scaffold which can easily encapsulate ADSCs, support the cells proliferation inside the scaffold and lead to enhanced secretion of growth factors and cytokines for the healing of chronic wounds.(5-7)

Cell therapy for diabetic wound

A diabetic foot ulcer is an open sore or wound with disintegration of the surrounding tissue. They most commonly occur on the bottom of the foot, and can affect anyone with diabetes. Ulcers occur due to multiple physical and physiological factors, such as lack of feeling in the foot (neuropathy), restricted circulation, deformities, friction or pressure, and trauma, as well as being an indication of mismanaged diabetes.

There are 25.8 million children and adults in the United States or 8.3% of the population who have diabetes (2011 National Diabetes Fact Sheet). It has also become a growing problem in Ireland and the EU with an estimated prevalence of 5%. 15% of people with diabetes develop foot ulcers and 70% of ulcers reoccur within five years, placing a heavy load in terms of cost on community services (Centre for Reviews and Dissemination, 1999). 15% of Diabetic foot ulcer cases lead to amputation and so are the cause of 85% of all amputations (Ramsey SD et all 1999). Many diabetes patients develop ulcers because of an acute of chronic repeated trauma and a combination of the following conditions: i) Neuropathy, a reduced or complete lack of feeling in the feet due to nerve damage caused by elevated blood glucose levels over time. ii) Vascular disease which reduces the body’s ability to heal and prevents the access of antibiotics, increasing the risk of infection.iii) Elevations in blood glucose can also reduce the body’s ability to fight off a potential infection and also retard and progress to gangrene. If the infection spreads to the blood stream it can become life threatening. As diabetic foot ulcers have such a range of etiological factors there is a high level of variation seen in these wounds.

Current treatment for Diabetic foot ulcers is aggressive regular debridement, antibiotics, moist wound dressings, pressure offloading and closely monitored glycemic control, however as previously mentioned there is still a very high level of amputations. Therefore, a pressing need for efficacious and low cost treatments in diabetic wounds still exists. Recent studies have indicated that stem cells may contribute to tissue repair or regeneration of many tissues including myocardium, blood vessels, damaged bone, and skin. Some factors have to be taken into account prior to engaging stem cells for therapeutic purposes such as i) they should be easily extracted, manipulated and multiplied effectively without being invasive ii) they should be differentiated into specific cells either through direct cell-cell contact or paracrine mechanisms on a biomaterial/ scaffold iii) they should withstand the wounded environment and not be prone to apoptosis and iv) they should promote neovascularization through the secretion of various proangiogenic growth factors. Taking this all into perspective we propose to use adipose derived stem cells (ADSCs) to effectively treat diabetic wounds and hence substantially enhance quality of life. Adipose tissue is a favourable source of stem cells as it can be extracted in large amounts with minor donor site morbidity.
Therefore, our strategy is to develop an advanced in-situ stem cell based dressing system with unique thermo-responsive properties for the treatment of chronic diabetic wounds. This novel polymeric system will consist of adipose derived stem cells encapsulated in-situ along with extracellular matrix biomolecules such as hyaluronic acid, collagen or gelatine. The dressing will facilitate the growth of adipose derived stem cells. This smart wound dressing consisting of polymer and stem cells will be liquid at room temperature; however after the application onto the wound, it will turn into a hydrogel thus forming a dressing as well as a reservoir system to secrete essential growth factors and cytokines for accelerated wound healing in chronic diabetic ulcers (8).

Gene therapy for RDEB

The skin is made up of a number of different layers. The outer is called the epidermis; the inner layers are the dermis. "Bullosa" is simply the name for a blister and "lysis" means breakdown. Hence, Epidermolysis Bullosa means the breakdown and blistering of the epidermis. There are 30 subtypes of EB divided across three groups, simplex, junctional and dystrophic.
One in 18,000 newborns are affected by EB in Ireland, over 500,000 people have EB worldwide [] Ireland website) The specific form of EB studied at the NFB is recessive dystrophic epidermolysis bullosa (RDEB, OMIM ID #226600) It is an autosomal recessive blistering disorder which can be caused by a variety of mutations in the COL7A1 gene. Located on chromosome band 3p21 the COL7A1 gene encodes type VII collagen, a main structural protein that attaches the epidermal basement membrane to the dermal matrix. Nearly every family has its own unique type of mutation effecting COL7A1. The protein is primarily produced by keratinocytes but also by fibroblasts. As collagen is such an integral protein RDEB affects the skin, eyes and internal membranes. Mutations in this gene lead to disruption of the integrity of the dermal-epidermal junction through structurally defective and reduced numbers of anchoring homotrimer fibrils. Thus, blisters are formed with ease, some only damaging the top layer of skin, others go on to form chronic wounds comparable to third degree burns. Clinically, the RDEB phenotype varies in severity, these patients have a 90% lifetime risk of squamous carcinoma, most commonly in areas of scarring. More than 55% of patients with severe phenotypes of RDEB die from squamous cell carcinomas by the age of 40. Current treatment is purely palliative, consisting of daily dressing changes and medication to prevent infections and manage pain.

In an effort to find a cure to this devastating disease, scientists have reverted to gene therapy approaches to treat the mechanobullous condition. Reversion of RDEB cell phenotype has been achieved by transducing the target cells with PhiC31 bacteriophage integrase carrying the COL7A1 cDNA, microinjection of P1-based artificial chromosome comprising the COL7A1 gene, in addition to lentiviral and retroviral vectors. The reverted keratinocytes secreted biologically functional collagen type VII protein and generate epithelia that restored formation of anchoring fibrils at the dermal-epidermal junction. However, the non-viral techniques lack transduction efficiency due to the large size (9.2 kb) of the COL7A1 cDNA while viral based vectors are hampered in clinical trials due to concerns over safety and absence of suitable packaging cell lines. Additionally, nearly all of the current gene therapy approaches associated with restoration of normal cutaneous phenotype are ex-vivo based. This involves transduction of collagen type VII null-RDEB keratinocytes and autologous transplantation of the corrected cells onto the recipient.

To overcome these obstacles we have developed a direct approach for the treatment of severe RDEB wounds by topical application of a non-viral, polymer-based vector (9) carrying the COL7A1 pcDNA to collagen type VII null-RDEB keratinocytes and dermal fibroblasts. Polymer-based vectors have previously been utilised for gene therapy and treatment of various diseases but none of them involve gene delivery to cutaneous tissue.
The objective of the project is synthesis of a hyperbranched cationic biodegradable polymer via one-pot in situ deactivation enhanced atom transfer radical polymerisation (DE-ATRP) for the efficient delivery of COL7A1 to the cells found in the epidermal-dermal junction, specifically; keratinocytes and dermal fibroblasts. The polymer will be optimised to achieve sufficient collagen type VII expression with reduced cytotoxicity. Prolonged expression of collagen type VII will be achieved by delivering the COL7A1 sequence containing the attb integrase.

Drug Delivery

The unique properties of dendritic polymer or ‘Celtic knot’ polymer include their high degree of branching, multi-functionalities, their globular/densed architecture and the precisely controlled of their molecular weight. This makes them promising new vehicles for drug delivery. We are focusing on the design and synthesis of multi-functional dendritic/ knot polymeric materials and their application to many areas of bioscience including drug delivery, immunology and the development of vaccines, biodetection and biosensor, antimicrobials and anti-virals (10-11).


[1]. Wang, W.; Zheng, Y.; Roberts, E.; Duxbury, C. J.; Ding, L.; Irvine, D. J.; Howdle, S. M. ‘Controlling chain growth: a new strategy to hyperbranched materials’ MACROMOLECULES 2007, 40(20), 7184-7194.

[2]. Zheng, Y.; Cao, H.; Newland, B.; Dong, Y.; Pandit, A.; Wang, W. ‘3D Single Cyclized Polymer Chain Structure From Controlled Polymerization of Multi-Vinyl Monomers: Beyond Flory-Stockmayer Theory’ JOURNAL OF AMERICAN CHEMICAL SOCIETY, 2011, 133(33), 13130-13137.

[3]. Chen, Z.; He, C.; Ehrhardt, A.; Kay, M. 'Minicircle DNA Vectors Devoid of Bacterial DNA Result in Persistent and High-Level Transgene Expression in Vivo' MOLECULAR THERAPY 2003, 8(3), 495-500.

[4]. Darquet, A.; Cameron, B.; Wils, P.; Scherman, D.; Crouzet, J. 'A new DNA vehicle for nonviral gene delivery: supercoiled minicircle' GENE THERAPY 1997, 4, 1341–1349.

[5]. Tai, H.; Howard, D.; Takae, S.; Wang, W.; Vermonden, T.; Hennink, W. E.; Stayton, P.; Hoffman, A.; Endruweit, A.; Alexander, C.; Howdle, S. M., Shakesheff, K. M. ‘Photocrosslinked hydrogels from thermoresponsive PEGMEMA-PPGMA-EGDMA copolymers containing multiple methacrylate groups: mechanical property, swelling, protein release and cytotoxicity’  BIOMACROMOLECULES 2009, 10, 2895-2903.

[6]. Tai, H.; Wang, W.; Vermonden, T.; Heath, F.; Hennink, W. E.; Alexander, C.; Shakesheff, K. M. and Howdle, S. M. ‘Thermal responsive and photocrosslinkable dendritic copolymers from one-step ATRP synthesis.’ BIOMACROMOLECULES 2009, 10, 822–828.

[7]. Dong, Y.; Cao, H.; Mathew, A.; Newland, B. E.; Saeed, A. O.; Gunning, P.; Magnusson, J. P.; Alexander, C.; Tai, H.; Pandit, A.; Wang, W. ‘Dual stimuli responsive PEG based dendritic polymers’ POLYMER CHEMISTRY 2010, 1, 827-830.

[8]. Wang, W.; Liang, H.; Hamilton, L.; Fraylich, M.; Shakesheff, K. M.; Saunders, B.; Alexander, C. ‘Biodegradable thermo-responsive microparticle dispersions for injectable cell delivery systems prepared using a single-step process’ ADVANCED MATERIALS 2009, 21, 1809–1813.

[9]. Newland, B. E.; Tai, H.; Zheng, Y.; Velascoa, D. B.; Howdle, S. M.; Alexander, C.; Wang, W.; Pandit, A. ‘A highly effective gene delivery vector - dendritic poly(2-(dimethylamino) ethyl methacrylate) from in-situ deactivation enhanced ATRP’ CHEMICAL COMMUNICATIONS 2010, 46, 4698-4700.

[10]. Cao, H.; Dong, Y.; O’Rorke, S.; Wang, W.; Pandit, P. ‘PEG based Hyperbranched Polymeric Hollow Nanospheres’ NANOTECHNOLOGY 2011, 22, 065604.

[11]. Magnússon, J. Pl; Khan, A.; Pasparakis, G.; Wang, W.; Alexander, C. ‘Ion-responsive polymers prepared in water’ JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 2008, 130(33), 10852-10853