Table 4.

Lignin-derived scaffold for possible bone tissue engineering applications.

Aim	Matrix Type	Additional Ingredients	Results	References
osteoconductivity	heat-treated birch wood	none	heat treatment of wood increases osteoconductivity	Rekola et al. 2009 [91]
scaffold fabrication	alginate-lignin aerogel (lignin from wheat straw by enzymatic hydrolysis)	none	fluid uptake in Tris-HCl buffer of >1600%, good biocompatibility	Quraishi et al. 2015 [92]
scaffold fabrication	starch, lignin (from Kraft lignin) or hemicellulose	none	hydrogels produced by reactive extrusion show pH dependent swelling behavior (water uptake at pH 9: from 400 to 1400%); the amount of citric acid used as cross-linker also influences both swelling and degradation of the hydrogels. Additional catalysts used during extrusion slow down degradation	Farhat et al. 2017 [94]
scaffold fabrication	agarose-lignin composites (lignin from Kraft black liquor)	none	crosslinked agarose-lignin hydrogels exhibit enhanced mechanical properties compared to pure agarose gels	Techato et al. 2018 [95]
influencing mechanical properties	lignin-chitosan microfibers	none	improving mechanical properties of chitosan fibers by adding 3% lignin	Wang et al. 2016 [97]
influencing mechanical properties	poly(lactic acid) with lignin as filler (Kraft lignin)	none	lignin as filler does not decrease storage modulus, but inhibits PLA crystallization	Anwer et al. 2015 [98]
influencing mechanical properties	poly(lactic acid) with up to 15% lignin as filler (Organosolv lignin from birch wood and Kraft lignin from softwood)	none	higher lignin content leads to higher tensile strength, but also slightly decreased water sorption capacity. Organosolv lignin yields slightly better mechanical results; good biocompatibility against SaOS-2 cells regardless of lignin type	Tanase et al. 2018 [99]
influencing mechanical properties	lignin-based copolymer/polyester blend nanofibers (alkali lignin)	none	mechanical improvement dependent on polyester, good antioxidant activity and biocompatibility against NIH/3T3 fibroblasts	Kai et al. 2017 [100]
bioactive coating for implants	hydroxyapatite/lignin composite coatings on titanium (Organosolv lignin)	doping of silver for antimicrobial effect	HA coatings on Ti were non-cytotoxic to peripheral blood mononuclear cells; Ag-doped coatings showed antibacterial behavior against S. aureus	Erakovic et al. 2014 [101]