On the Effect of Monomer Chemistry on Growth Mechanisms of Nonfouling PEG-like Plasma Polymers

It has been shown that both ions and neutral species may contribute to plasma polymer growth. However, the relative contribution from these mechanisms remains unclear. We present data elucidating the importance of considering monomer structure with respect to which the growth mechanism dominates for nonfouling PEG-like plasma polymers. The deposition rate for saturated monomers is directly linked with ion flux to the substrate. For unsaturated monomers, the neutral flux also plays a role, particularly at low power. Increased fragmentation of the monomer at high power reduces the ability of unsaturated monomers to grow via neutral grafting. Chemical characterization by X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) confirm the role that plasma phase fragmentation plays in determining the deposition rate and surface chemistry of the deposited film. The simple experimental method used here may also be used to determine which mechanisms dominate plasma deposition for other monomers. This knowledge may enable significant improvement in future reactor design and process control

Haptotatic Plasma Polymerized Surfaces for Rapid Tissue Regeneration and Wound Healing

Skin has a remarkable capacity for regeneration; however, with an ever aging population, there is a growing burden to the healthcare system from chronic wounds. Novel therapies are required to address the problems associated with nonhealing chronic wounds. Novel wound dressings that can encourage increased reepithelialization could help to reduce the burden of chronic wounds. A suite of chemically defined surfaces have been produced using plasma polymerization, and the ability of these surfaces to support the growth of primary human skin cells has been assessed. Additionally, the ability of these surfaces to modulate cell migration and morphology has also been investigated. Keratinocytes and endothelial cells were extremely sensitive to surface chemistry showing increased viability and migration with an increased number of carboxylic acid functional groups. Fibroblasts proved to be more tolerant to changes in surface chemistry; however, these cells migrated fastest over amine-functionalized surfaces. The novel combination of comprehensive chemical characterization coupled with the focus on cell migration provides a unique insight into how a material’s physicochemical properties affect cell migration

Development of Advanced Dressings for the Delivery of Progenitor Cells

Culture surfaces that substantially reduce the degree of cell manipulation in the delivery of cell sheets to patients are described. These surfaces support the attachment, culture, and delivery of multipotent adult progenitor cells (MAPC). It was essential that the processes of attachment/detachment to the surface did not affect cell phenotype nor the function of the cultured cells. Both acid-based and amine-based surface coatings were generated from acrylic acid, propanoic acid, diaminopropane, and heptylamine precursors, respectively. While both functional groups supported cell attachment/detachment, amine coated surfaces gave optimal performance. X-ray photoelectron spectroscopy (XPS) showed that at a primary amine to carbon surface ratio of between 0.01 and 0.02, greater than 90% of attached cells were effectively transferred to a model wound bed. A dependence on primary amine concentration has not previously been reported. After 48 h of culture on the optimized amine surface, PCR, functional, and viability assays showed that MAPC retained their stem cell phenotype, full metabolic activity, and biological function. Consequently, in a proof of concept experiment, it was shown that this amine surface when coated onto a surgical dressing provides an effective and simple technology for the delivery of MAPC to murine dorsal excisional wounds, with MAPC delivery verified histologically. By optimizing for cell delivery using a combination of in vitro and in vivo techniques, we developed an effective surface for the delivery of MAPC in a clinically relevant format