Valorization of Multifunctional Lignin for Green and Facile Synthesis of Bio-inspired PLA/lignin Composites and a Light-colored Lignin Nanoparticle Sunscreen = 바이오 기반 PLA/Lignin 복합체와 밝은 색상의 리그닌 나노입자 자외선 차단제의 친환경 및 용이한 합성을 위한 다기능 리그닌으로서의 활용

다국어 초록 (Multilingual Abstract)

This study encompasses two areas of lignin utilization i.e. fabrication of lignin/PLA composites for biomedical purposes and synthesis of Lignin nanoparticles for sunscreen applications.
Firstly, acetylated and non-acetylated soda lignin were utilized to fabricate anti-oxidant PLA/lignin composites for biomedical applications. After acetylation of lignin a good compatibility between PLA and lignin was observed in SEM images. The tensile properties of all the PLA/ASL composites were higher than PLA/SL composites. PLA/ASL5 displayed highest tensile strength and elongation at break of around 56 MPa and 10% respectively. PLA/SL15 and PLA/SL20 demonstrated superior UV-blocking potential with UV-transmittance less than 10%.
Anti-oxidant test by DPPH assay showed that PLA/SL composites rendered excellent radical scavenging activity with PLA/SL20 displaying RSA value of around 80%. Furthermore, In vitro antioxidant activity was evaluated by H2O2 exposure and was confirmed by live/dead assay. The results demonstrated that PLA/SL composites could protect both type of cell lines from oxidative stress. In addition, all the PLA/SL and PLA/ASL composites promoted cell proliferation compared to neat PLA. PLA/SL5 and PLA/SL10 displayed the highest cell proliferation amongst all the composites. Lastly, all the PLA/SL and PLA/ASL composites had haemoglobin release below 2%.
Secondly, Kraft lignin was fractionated and acetylated to obtain fractions with different molecular weights (Mw 2,175 – 8,150) and phenolic hydroxyl group content (total 3.05 – 3.2 mmolg-1). Subsequently, the lignins fractions were synthesised into Lignin nanoparticles (LNPs) by nanoprecipitation. Spherical LNPs of size between 219nm – 912nm were obtained. Fractions with high molecular weight generated particles of small diameter. The biocompatibility test with Human skin cell lines demonstrated good biocompatibility at low concentration of LNPs. Moreover, follow up analysis will be performed in order to develop a light-coloured, high SPF and antioxidant sunscreen from lignin nanoparticles.
The results of the first study indicate that lignin/PLA composites could be a sustainable option to develop green, antioxidant, bioactive and hemo-compatible biomaterials for biomedical applications

다국어 초록 (Multilingual Abstract)

This study encompasses two areas of lignin utilization i.e. fabrication of lignin/PLA composites for biomedical purposes and synthesis of Lignin nanoparticles for sunscreen applications.
Firstly, acetylated and non-acetylated soda lignin were utilized to fabricate anti-oxidant PLA/lignin composites for biomedical applications. After acetylation of lignin a good compatibility between PLA and lignin was observed in SEM images. The tensile properties of all the PLA/ASL composites were higher than PLA/SL composites. PLA/ASL5 displayed highest tensile strength and elongation at break of around 56 MPa and 10% respectively. PLA/SL15 and PLA/SL20 demonstrated superior UV-blocking potential with UV-transmittance less than 10%.
Anti-oxidant test by DPPH assay showed that PLA/SL composites rendered excellent radical scavenging activity with PLA/SL20 displaying RSA value of around 80%. Furthermore, In vitro antioxidant activity was evaluated by H2O2 exposure and was confirmed by live/dead assay. The results demonstrated that PLA/SL composites could protect both type of cell lines from oxidative stress. In addition, all the PLA/SL and PLA/ASL composites promoted cell proliferation compared to neat PLA. PLA/SL5 and PLA/SL10 displayed the highest cell proliferation amongst all the composites. Lastly, all the PLA/SL and PLA/ASL composites had haemoglobin release below 2%.
Secondly, Kraft lignin was fractionated and acetylated to obtain fractions with different molecular weights (Mw 2,175 – 8,150) and phenolic hydroxyl group content (total 3.05 – 3.2 mmolg-1). Subsequently, the lignins fractions were synthesised into Lignin nanoparticles (LNPs) by nanoprecipitation. Spherical LNPs of size between 219nm – 912nm were obtained. Fractions with high molecular weight generated particles of small diameter. The biocompatibility test with Human skin cell lines demonstrated good biocompatibility at low concentration of LNPs. Moreover, follow up analysis will be performed in order to develop a light-coloured, high SPF and antioxidant sunscreen from lignin nanoparticles.
The results of the first study indicate that lignin/PLA composites could be a sustainable option to develop green, antioxidant, bioactive and hemo-compatible biomaterials for biomedical applications

목차 (Table of Contents)

• 1. Introduction 1
• 1.1. Climate change and biomass-based energy 1
• 1.2. Lignin production, structure and chemistry 4
• 1.3. The need for sustainable alternatives in the food packaging and polymeric biomedical industry 7
• 1.4. Sunscreen formulations and the organic skin care industry 10
• 1.5. Objectives 13
• 2. Literature review 15
• 2.1. Lignin as a biomaterial 15
• 2.2. Sustainable materials in sunscreen formulations 18
• 2.2.1. Previous attempts to use lignin in sunscreen formulations 18
• 2.2.2. Lignin nanoparticles as sunscreen ingredients 22
• 3. Materials and methods 25
• 3.1. Bioactive and Hemo-compatible PLA/lignin Bio composites: Assessment of In-vitro Antioxidant Activity for biomedical applications 25
• 3.1.1. Materials 25
• 3.1.2. Acetylation of lignin 25
• 3.1.3. Preparation of lignin-PLA composites by extrusion 25
• 3.1.4. Physiochemical characterization of composites 29
• 3.1.5. Antioxidant Activity by DPPH assay 31
• 3.1.6. Biocompatibility tests 32
• 3.2. Synthesis and colour reduction of Lignin nanoparticles encapsulating CeO2 for safe, anti-oxidant and high SPF sunscreen 36
• 3.2.1. Materials 36
• 3.2.2. Fractionation and acetylation of lignin 36
• 3.2.3. Characterization of fractionated and acetylated lignin 38
• 3.2.4. Lignin nanoparticle formation 39
• 3.2.5. Biocompatibility by CKK-8 assay 41
• 3.3. Statistical Analysis 43
• 4. Results and discussion 44
• 4.1. Bioactive and Hemo-compatible PLA/lignin Bio composites: Assessment of In-vitro Antioxidant Activity for biomedical applications 44
• 4.1.1. FTIR 44
• 4.1.2. Thermal properties 48
• 4.1.3. Surface Morphology 54
• 4.1.4. Mechanical properties 56
• 4.1.5. Optical properties and wettability of composites 58
• 4.1.6. Determination of Antioxidant Activity by DPPH assay and In-vitro H2O2 exposure 62
• 4.1.7. In-vitro cell viability of composites 69
• 4.1.8. Hemocompatibility of composites 79
• 4.2. Synthesis and colour reduction of Lignin nanoparticles encapsulating CeO2 for safe, anti-oxidant and high SPF sunscreen 81
• 4.2.1. Characterization of lignin fractions 81
• 4.2.2. Lignin nanoparticles size and morphology 87
• 4.2.3. In vitro cell viability 91
• 5. Conclusion 94