Degradable pollen as potential candidates to replace plastic packages

• Main Author: Deng, Jingyu
• Other Authors: Cho Nam-Joon
• Format: Thesis-Master by Research
• Language: English
• Published: Nanyang Technological University 2022
• Subjects: Engineering::Materials::Biomaterials
• Online Access: https://hdl.handle.net/10356/156177
• Institution: Nanyang Technological University

The explosive growth of plastic consumption contaminates the natural environment seriously and microplastic debris with toxic additives threatens marine organisms and human health. Along with large amounts of plastic use, improper management of plastic wastes and pose bigger pressure to ecological environment. More than 90% of plastic discards are landfilled and combusted which could cause secondary contamination, while small parts are recycled which is time-consuming and costly. To date, scientists already have detected influence of plastic pollution in marine and terrestrial ecosystems. The uptake of plastic debris by marine organisms and toxicity impact on lifespan shortening are investigated. More researchers also explored the direct microplastic leaches from cosmetics, teabags, mineral water bottles, infant bottles and daily necessities. With increasing demands for plastic food packaging due to COVID-19 personal protection, the direct contamination released from plastic food containers with cooked food and hot beverages remains equivocal and becomes extra important. Plastic polymers, derived from petro and fuel chemicals, are ultra-resistant, easy-processing, low-costing, thermal stable and with great mechanical properties. Although plastic polymers and toxic additives are malignant, plastic inevitably promotes development of society. Scientists researched the biodegradation process of individual types of plastic through bacterium and cells which are expensive and complicated. On the other hand, discovering alternatives of plastic is compulsory that bioinspired and biological materials are significant because of biocompatibility and environmental protection. Bee pollen granules attract attention due to durable shell structure. Sporopollenin exine capsules (SECs), are extracted from bee pollen and resistant with anti-oxidation, ultraviolet resistance. SECs are widely applied as drug delivery vehicles including orally therapeutic medicine and anti-cancer drug carriers. Degradation of SECs in gastrointestinal tract fluids and human plasma are analyzed that proves enzyme-dependent and chemical/enzyme-dependent degradation with happens of SECs. Elasticpollen microgel particles are found to fabricate pollen papers with high surface contact areas. Pollen papers are elastic, flexible, easy processed that can be considered as alternatives of flexible plastic. However, the chemical-degradation without enzyme remains unknown. Herein, a significant amount of microplastics in the nanoscale range are demonstrated to be generated from the plastic packages that contact with high temperatures associated with cooked food or hot beverages. The quantities, diameters and morphologies of micro/nano plastic particles are refined and observed. In-vitro experiments are conducted and prove procedures of murine macrophages to inject different types of micro/nano plastics. The inhibited activity of lysosome presents the plastic effects to mammal organisms after long-term exposure. Human intake large quantities of plastic debris and chronic exposure may cause inflammation and cancers. To prove pollen papers are eco-friendly and biocompatible, in-vitro degradation of pollen papers are conducted in phosphate buffer saline (PBS) solution, the same ion concentration and pH values as extracellular fluid, and deionized water (DI) that chemical hydrolysis process is discovered after several months. Pollen papers exhibit obvious chemical degradation in PBS solution after several months, while the mechanical properties remain stable in short term. Although poor mechanical properties and hydrophobicity of pollen papers remain to be further improved, pollen papers are flexible, biodegradable, easy-processing and with low cost. The way to fabricate pollen papers to replace plastic are long journey but moving forward to realize sustainability and to protect nature environment are inevitable and significant for human.