This review covers the latest developments and challenges in the field of broad-spectrum sunscreens and how sunscreens based on lignin address their requirements in terms of sunlight protection, antioxidants, and preservatives.

The purpose of this study was to elucidate the structures and functional properties of tannin- and lignin-derived nano- and microparticles and the coatings prepared from them. Nanoparticles prepared from technical lignins and water-insoluble tannin obtained from softwood bark showed large differences in the suspension testing of antibacterial efficacy against methicillin-resistant Staphylococcus aureus (MRSA) bacteria. A common factor among the most effective lignin nanoparticles was a relatively low molar mass of the lignin, but that alone did not guarantee high efficacy. Tannin nanoparticles showed good antibacterial activity both in suspension testing and as coatings applied onto cellulose. The nanoparticles of nitrogen-modified tannin and the small microparticles of nitrogen-modified kraft lignin exhibited promising flame-retardant parameters when applied as coatings on cellulose. These results illustrate the potential of nano- and microsized particles of unmodified and chemically modified polyphenols to provide functional coatings to cellulosic substrates for environments and applications with high hygiene and fire safety requirements.

Full penetration-dyed solid wood has the advantage that furniture or other items fabricated from it do not require additional painting or staining. However, anatomical barriers along potential dye infiltration pathways may result in unsatisfactory dyeing in terms of depth of dye penetration or colour intensity and uniformity. Dyed wood items, even those intended for interior use, should also possess a certain degree of water fastness. In the present paper, full-thickness dyeing of radiata pine blocks was achieved with fibre-reactive and direct dyes as well as pine tannin. Leaching of the treated blocks in cold water removed excess dye but the target colours were well retained. Pectinase pre-treatment of wood blocks was shown to increase the uptake of fibre-reactive and direct dyes by tracheid cell walls and the uptake of tannin by rays, resin canals, and tracheid lumina. In the case of a direct dye and pine tannin, pectinase treatment markedly increased the intensity of the target colours. Combining tannin with laccase to achieve covalent bonding of tannin to wood lignin was associated with a small, albeit not statistically significant, shift towards the target colour.