Life cycle assessments of biodegradable, commercial biopolymers - A critical review

Biopolymers are generally considered an eco-friendly alternative to petrochemical polymers due to the renewable feedstock used to produce them and their biodegradability. However, the farming practices used to grow these feedstocks often carry significant environmental burdens, and the production energy can be higher than for petrochemical polymers. Life cycle assessments (LCAs) are available in the literature, which make comparisons between biopolymers and various petrochemical polymers, however the results can be very disparate. This review has therefore been undertaken, focusing on three biodegradable biopolymers, poly(lactic acid) (PLA), poly(hydroxyalkanoates) (PHAs), and starch-based polymers, in an attempt to determine the environmental impact of each in comparison to petrochemical polymers. Reasons are explored for the discrepancies between these published LCAs. The majority of studies focused only on the consumption of non-renewable energy and global warming potential and often found these biopolymers to be superior to petrochemically derived polymers. In contrast, studies which considered other environmental impact categories as well as those which were regional or product specific often found that this conclusion could not be drawn. Despite some unfavorable results for these biopolymers, the immature nature of these technologies needs to be taken into account as future optimization and improvements in process efficiencies are expected. © 2013 Elsevier B.V. All rights reserved.

Evaluation of the functionality of biodegradable polymeric platforms for drug delivery systems

We present the development of a drug-loaded triple-layer platform consisting of thin film biodegradable polymers, in a properly designed form for the desired gradual degradation. Poly(dl-lactide-co-glycolide) (PLGA (65:35), PLGA (75:25)) and polycaprolactone (PCL) were grown by spin coating technique, to synthesize the platforms with the order PCL/PLGA (75:25)/PLGA (65:35) that determine their degradation rates. The outer PLGA (65:35) layer was loaded with dipyridamole, an antiplatelet drug. Spectroscopic ellipsometry (SE) in the Vis-far UV range was used to determine the nanostructure, as well as the content of the incorporated drug in the as-grown platforms. In situ and real-time SE measurements were carried out using a liquid cell for the dynamic evaluation of the fibrinogen and albumin protein adsorption processes. Atomic force microscopy studies justified the SE results concerning the nanopores formation in the polymeric platforms, and the dominant adsorption mechanisms of the proteins, which were defined by the drug incorporation in the platforms. © 2013 Elsevier B.V. All rights reserved.

Chemical surface modification of poly-ε-caprolactone improves Schwann cell proliferation for peripheral nerve repair.

Poly-ε-caprolactone (PCL) is a biodegradable and biocompatible polymer used in tissue engineering for various clinical applications. Schwann cells (SCs) play an important role in nerve regeneration and repair. SCs attach and proliferate on PCL films but cellular responses are weak due to the hydrophobicity and neutrality of PCL. In this study, PCL films were hydrolysed and aminolysed to modify the surface with different functional groups and improve hydrophilicity. Hydrolysed films showed a significant increase in hydrophilicity while maintaining surface topography. A significant decrease in mechanical properties was also observed in the case of aminolysis. In vitro tests with Schwann cells (SCs) were performed to assess film biocompatibility. A short-time experiment showed improved cell attachment on modified films, in particular when amino groups were present on the material surface. Cell proliferation significantly increased when both treatments were performed, indicating that surface treatments are necessary for SC response. It was also demonstrated that cell morphology was influenced by physico-chemical surface properties. PCL can be used to make artificial conduits and chemical modification of the inner lumen improves biocompatibility.

Long term peripheral nerve regeneration using a novel PCL nerve conduit.

The gold standard in surgical management of a peripheral nerve gap is currently autologous nerve grafting. This confers patient morbidity and increases surgical time therefore innovative experimental strategies towards engineering a synthetic nerve conduit are welcome. We have developed a novel synthetic conduit made of poly ε-caprolactone (PCL) that has demonstrated promising peripheral nerve regeneration in short-term studies. This material has been engineered to permit translation into clinical practice and here we demonstrate that histological outcomes in a long-term in vivo experiment are comparable with that of autologous nerve grafting. A 1cm nerve gap in a rat sciatic nerve injury model was repaired with a PCL nerve conduit or an autologous nerve graft. At 18 weeks post surgical repair, there was a similar volume of regenerating axons within the nerve autograft and PCL conduit repair groups, and similar numbers of myelinated axons in the distal stump of both groups. Furthermore, there was evidence of comparable re-innervation of end organ muscle and skin with the only significant difference the lower wet weight of the muscle from the PCL conduit nerve repair group. This study stimulates further work on the potential use of this synthetic biodegradable PCL nerve conduit in a clinical setting.

Polymer film packaging for food: An environmental assessment

Plastics packaging is ubiquitous in the food industry, fulfilling a range of functions including a significant role in reducing food waste. The public perception of packaging, however, is dominated by end-of-life aspects, when the packaging becomes waste often found littering urban, rural and marine environments. A balanced analysis of the role of packaging demands that the whole lifecycle is examined, looking not only at the packaging itself but also at the product being packaged. This paper focuses on packaging in the meat and cheese industry, analysing the impact of films and bags. The functions of packaging are defined and the environmental impact of delivering these functions is assessed. The influence of packaging on levels of waste and energy consumption elsewhere in the system is examined, including the contentious issue of end-of-life for packaging. Strategies for minimizing the environmental impact of the packaging itself involve reduction in the amount of material used (thinner packaging), rather than emphasizing end-of-life issues. Currently, with polymer recycling not at a high level, evidence suggests that this strategy is justifiable. Biodegradable polymers may have some potential for improving environmental performance, but are still problematic. The conclusion is that although current packaging is in some ways wasteful and inefficient, the alternatives are even less desirable. © 2013 Elsevier B.V. All rights reserved.

Development of a nanoporous and multilayer drug-delivery platform for medical implants.

Biodegradable polymers can be applied to a variety of implants for controlled and local drug delivery. The aim of this study is to develop a biodegradable and nanoporous polymeric platform for a wide spectrum of drug-eluting implants with special focus on stent-coating applications. It was synthesized by poly(DL-lactide-co-glycolide) (PLGA 65:35, PLGA 75:25) and polycaprolactone (PCL) in a multilayer configuration by means of a spin-coating technique. The antiplatelet drug dipyridamole was loaded into the surface nanopores of the platform. Surface characterization was made by atomic force microscopy (AFM) and spectroscopic ellipsometry (SE). Platelet adhesion and drug-release kinetic studies were then carried out. The study revealed that the multilayer films are highly nanoporous, whereas the single layers of PLGA are atomically smooth and spherulites are formed in PCL. Their nanoporosity (pore diameter, depth, density, surface roughness) can be tailored by tuning the growth parameters (eg, spinning speed, polymer concentration), essential for drug-delivery performance. The origin of pore formation may be attributed to the phase separation of polymer blends via the spinodal decomposition mechanism. SE studies revealed the structural characteristics, film thickness, and optical properties even of the single layers in the triple-layer construct, providing substantial information for drug loading and complement AFM findings. Platelet adhesion studies showed that the dipyridamole-loaded coatings inhibit platelet aggregation that is a prerequisite for clotting. Finally, the films exhibited sustained release profiles of dipyridamole over 70 days. These results indicate that the current multilayer phase therapeutic approach constitutes an effective drug-delivery platform for drug-eluting implants and especially for cardiovascular stent applications.