Development of novel scaffold systems for modulating biotic activity

Abstract

Composite scaffolds are the core of tissue engineering therapeutics that are being used to revolutionise modern medicine. Microbial interactions with scaffolds have become an important area of study as infection has been a major problem for these devices. This study explores means of modulating biotic activity through the use of differentiated coatings on a biocompatible polymer matrix. Both antibacterial and pro-bacterial scaffold systems were developed for chronic skin wounds and ethylene-mediated spoilage respectively. Chronic skin wounds present a major problem for the health sector. Wound dressings and other treatments have many shortfalls. Tissue engineered skin grafts are recognised as having great potential, but as yet these have failed to address wound sepsis. An acellular wound healing scaffold is proposed: The bi-phasic scaffold is comprised of a bioresorbable aliphatic polyester supporting a polyvinyl alcohol (PVA) hydrogel webbing capable of delivering erythromycin antibiotic and bioactive factors. Erythromycin was loaded into the PVA employing ethanol as a carrier and sustained release assays were performed showing that Staphylococcus aureus could be inhibited for up to 5 days. A novel in vitro co-culture was used to validate the scaffold which proved it could simultaneously prevent bacterial biofilms while allowing for fibroblast adhesion and proliferation. The price of fresh food is on the rise and spoilage is a key inefficiency in the fresh food value chain. In post-harvest storage facilities ethylene can build up and cause the food to spoil before it reaches the consumer. Chemical scrubbers are used to prevent this but their active agents require regular replacement. Biofilters using live microbes have dramatically longer working lifetimes. An ethylene biofilter was designed using tissue engineering principles offering control of biofiltration properties. Mycobacterium strain NBB4 cells were immobilised to a porous matrix in an agar coating. 0.4% w/v agar was found to be the optimal concentration for ethylene removal. The biofilter was able to degrade ethylene efficiently for > 85 days and had a shelf life up to > 60 days when in humidified packaging. The biofilters prevented bananas from rotting for up to 1 month compared to controls that spoiled in 2 weeks.