Nanocellulose, a unique and promising natural material extracted from native cellulose, has gained much attention for its use as biomedical material, because of its remarkable physical properties, special surface chemistry and excellent biological properties (biocompatibility, biodegradability and low toxicity). Three different types of nanocellulose, viz. cellulose nanocrystals (CNC), cellulose nanofibrils (CNF) and bacterial cellulose (BC), are introduced and compared in terms of production, properties and biomedical applications in this article. The advancement of nanocellulose-based biomedical materials is summarized and discussed on the analysis of latest studies (especially reports from the past five years). Selected studies with significant findings are emphasized, and focused topics for nanocellulose in biomedicine research in this article include the discussion at the level of molecule (e.g. tissue bioscaffolds for cellular culture; drug excipient and drug delivery; and immobilization and recognition of enzyme/protein) as well as at the level of macroscopic biomaterials (e.g. blood vessel and soft tissue substitutes; skin and bone tissue repair materials; and antimicrobial materials). Functional modification of nanocellulose will determine the potential biomedical application for nanocellulose, which is also introduced as a separated section in the article. Finally, future perspectives and possible research points are proposed in Section 5

Intensive exploration and research in the past few decades on polysaccharide nanocrystals, the highly crystalline nanoscale materials derived from natural resources, mainly focused originally on their use as a reinforcing nanophase in nanocomposites. However, these investigations have led to the emergence of more diverse potential applications exploiting the functionality of these nanomaterials. Based on the construction strategies of functional nanomaterials, this article critically and comprehensively reviews the emerging polysaccharide nanocrystal-based functional nanomaterials with special applications, such as biomedical materials, biomimetic optical nanomaterials, bio-inspired mechanically adaptive nanomaterials, permselective nanostructured membranes, template for synthesizing inorganic nanoparticles, polymer electrolytes, emulsion nano-stabilizer and decontamination of organic pollutants. We focus on the preparation, unique properties and performances of the different polysaccharide nanocrystal materials. At the same time, the advantages, physicochemical properties and chemical modifications of polysaccharide nanocrystals are also comparatively discussed in view of materials development. Finally, the perspective and current challenges of polysaccharide nanocrystals in future functional nanomaterials are outlined.

Preparation of cellulose nanocrystals with gradiented sulfation degrees, and surface chemistry affected by different cross-section models.