Bozena Nowak

Biodegradation of Pre-Aged Modified Polyethylene Films

Synthetic polymers, which are ubiquitous in modern industrial society, contribute to improving comfort and quality of our life. Currently more than 260 million tonnes of plastics are being produced each year (O’Brine & Thompson, 2010). Among them polyolefins constitute the majority of consumed thermoplastics. Polyolefin materials, such as low-density polyethylene (LDPE), due to the exceptional mechanical and thermal properties, ease of fabrication and low cost, find diverse applications in many fields. Polyethylenes represent 64% of materials used for various applications such as containers, bottles, tubing, plastic bags, greenhouses, mulching films, which are usually discarded after only brief use (Peacock, 2000). These mostly one-trip applications lead to a large quantity of plastic waste accumulating, at the rate of 25 million tons per year (Meenakshi et al., 2002) in landfill and in natural habitats (Thompson et al., 2009). Thus, plastics the most visible form of trash have become ubiquitous in our environment, leading to long-term environment, economic and waste management problems (Koutny et al., 2006). Since plastic waste are often soiled by biological substances, physical recycling of these materials turned out impractical and generally undesirable (El-Naggar & Farag, 2010). Incineration of plastics, in turn, has various environmental and social constraints. It seems that the use of plastics, which can re-enter the biological life cycle through biodegradation will be the best choice (Sivan, 2011; Soni et al., 2009).

Poly(isosorbide succinate)-based in situ forming implants as potential systems for local drug delivery: Preliminary studies

In situ forming implants (ISFI) are proved to be effective drug delivery systems in various local therapies. This research focuses on preliminary characteristics of a new biodegradable ISFI formulation based on poly(isosorbide succinate) (PISU) for modulated, over 3-week, release of doxycycline hyclate (DOXY). The Alamar Blue cytotoxicity assay was carried out for PISU using FK-1 and AoSMC cell lines. PISU resin was found to be non-toxic in wide range of concentrations. The formulation viscosity, dependent on shear rate, facilitates its easy injection into required site where solid depot is formed immediately after injection. DOXY, incorporated into this formulation, was released in vitro within 21 days, during which collected solutions exhibited antibacterial activity against gram-positive and gram-negative bacteria Staphylococcus aureus and Escherichia coli, respectively. The morphology of the precipitated depots was characterized by scanning electron microscopy (SEM). The obtained results suggest potential applicability of this new PISU-based formulation as injectable drug delivery system forming implant at an injection site by phase separation and precipitation of the polymer.

Degradation of PVC/rPLA Thick Films in Soil Burial Experiment

Some of the biodegradable polymers can be blended with a synthetic polymer to facilitate their biodegradation in the environment. The objective of the study was to investigate the biodegradation of thick films of poly(vinyl chloride)/recycled polylactide (PVC/rPLA). The experiments were carried out in the garden soil or in the mixture of garden soil and hydrocarbon-contaminated soil under laboratory conditions. Since it is widely accepted that the biosurfactants secreted by microorganisms enable biotransformation of various hydrophobic substances in the environment, it was assumed that the use of contaminated soil, rich in biosurfactant producing bacteria, may accelerate biodegradation of plastics. After the experimental period, the more noticeable weight loss of polymer films was observed after incubation in the garden soil. However, more pronounced changes in the film surface morphology and chemical structure as well as decrease of tensile strength were observed after incubation of films in the mixture of garden and contaminated soil. It turned out that as a result of competition between two distinct groups of microorganisms present in the mixture of garden and hydrocarbon-contaminated soils the number of microorganisms and their activity were lower than the activity of indigenous microflora of garden soil as well as the amount of secreted biosurfactants towards plastics.