Cellulose nanocrystals physical properties

This chapter focuses on the use of nanotechnology in the development of cellulose and chitin nanoctystals and their novel biomedical applications. It consists of four main sections. The first section is a brief introduction. The second section focuses on cellulose nanocrystals (CNCs) and their preparation procedure, physical properties, and surface modifications. Cationic modification of CNCs is also presented to produce positively charged CNCs. Various bioapplications of CNCs in bionanocomposites, drug delivery, and biosensors are discussed as well. The third section focuses on chitin nanoctystals (CHNCs). Except for a short introduction on chitin and its structure, the methods of isolation and characterization of chitin are discussed and the surface modifications and properties of CHNCs are summarized. The applications of CHNCs as reinforcing fillers in nanocomposites and several biomedical applications are discussed. The fourth section is a summary and perspective highlighting the future directions on the application of these natural nanoctystals in various key industries related to biomedicine. 

Nanocrystals extracted from starch are also used as fillers in polymer matrices. These nanoparticles not only increase the mechanical properties but also the physical properties such as permeability and fire retardancy of these composites. Unlike cellulose or chitin which exhibit needle-like nanocrystals, SNs occur as platelet-like nanoparticles. Thus starch has the versatility of being used both as a matrix and a filler. 

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