Design and Preparation of Nanochitin–Nanolignin Complexes for Innovative Cosmeceuticals, Nutraceuticals, and Skin-Beneficial Products

Chitin nanofibrils (CNs) and lignin nanoparticles (LNPs) are renewable nanomaterials whose complementary surface chemistry enables the formation of chitin nanofibril–nanolignin (CN–NL) complexes. This review addresses a specific gap in the literature by linking the source and preparation of each component to surface charge, complexation conditions, processing, and application-level performance. Conventional and emerging CN and LNP production routes are compared critically in terms of morphology, surface chemistry, yield, scalability, energy and solvent demand, and compatibility with subsequent assembly. Available quantitative evidence indicates that electrostatic attraction is the principal interaction under mildly acidic conditions, while hydrogen bonding and hydrophobic interactions provide secondary contributions. Reported CN–NL carrier formulations commonly use a 2:1 CN:NL mass ratio, but this value has not been established as universally optimal; similarly, encapsulation efficiency, release kinetics, storage stability, and scale-up economics remain insufficiently quantified. The strongest direct evidence concerns skin-contact and wound-related systems, whereas nutraceutical and agricultural uses remain prospective. Safety, biodegradation, lifecycle, and regulatory requirements are therefore evaluated separately from performance claims. Overall, CN–NL complexes are a promising multifunctional platform, but translation requires standardized characterization and application-specific validation rather than assuming functionality or sustainability from their bio-based origin alone.