Nanocrystals, polysaccharid

Roman, M. Dong, S. Hirani, A. Lee, Y.W. Chapter 12 Cellulose nanocrystals for drug delivery. In Polysaccharide Materials Performance by Design Edgar, K.J., Heinze, T., Buchanan, C. Eds. ACS Symposium Series 1017. American Chemical Society Washington, DC, 2009. 

Lin N, Huang J, Chang PR et al (2011) Effect of polysaccharide nanocrystals on structure, properties, and drug release kinetics of alginate-based microspheres. Colloids Surf B 85 270-279... 

Lin N, Huang J, Dufresne A (2012) Preparation, properties and applications of polysaccharide nanocrystals in advanced functional nanomaterials a review. Nanoscale 4 3274—3294... 

Hu Z, Cranston ED, Ng R, Pelton R (2014) Tuning cellulose nanocrystal gelation with polysaccharides and surfactants. Langmuir 30 2684-2692... 

Yang X, Bakaic E, Hoare T, Cranston ED (2013) Injectable polysaccharide hydrogels reinforced with cellulose nanocrystals morphology, rheology, degradation, and cytotoxicity. Biomacromolecules 14 4447-4455... 

Intelligent processing techniques described in the next sections are currently used to produce nanocrystals, also called rod-like nanowhiskers, of polysaccharides that can act as reinforcing fillers in bionanocomposites as well as carriers for therapeutic compounds. The chemical nature of these nanocrystals, along with their rigid, uniform, hierarchical structure, is the reason for their excellent reinforcing properties. 

In tissue engineering, the bionanocomposite scaffolds comprising polysaccharide nanocrystals can be used as carriers for the localized and controlled release of hioactive compounds, such as growth factors, proteins. 

As previously mentioned, natural fibres present a multi-level organization and consist of several cells formed out of semi-crystalline oriented cellulose micro fibrils. Each microfibril can be considered as a string of cellulose crystallites, linked along the chain axis by amorphous domains (Fig. 19.10) and having a modulus close to the theoretical limit for cellulose. They are biosynthesized by enzymes and deposited in a continuous fashion. A similar structure is reported for chitin, as discussed in Chapter 25. Nanoscale dimensions and impressive mechanical properties make polysaccharide nanocrystals, particularly when occurring as high aspect ratio rod-like nanoparticles, ideal candidates to improve the mechanical properties of the host material. These properties are profitably exploited by Mother Nature. 

Stable aqueous suspensions of polysaccharide nanocrystals can be prepared by the acid hydrolysis of vegetable biomass. Different descriptors of the resulting colloidal suspended particles are used, including whiskers, mono-crystals and nanocrystals. The designation whiskers is used to describe elongated rod-like nanoparticles. These crystallites have also often been referred in the literature as microfibrils, microcrystals or microcrystallites, despite their nanoscale dimensions. Most of the studies reported in the literature refer to cellulose nanocrystals. A recent review described the properties and applications of cellulose whiskers in nanocomposites [31]. 

Polysaccharides are good candidates for renewable nanofillers because they have partially crystalline structures conferring interesting properties. Two important types of nanofillers have been developed from cellulose, namely whiskers and nanocrystals. Whiskers have also been developed from chitin while starch has been used for preparation of nanocrystals. 

This technique is also a kind of casting and evaporating technique which is used for polysaccharides modified by various surface chemical reactions. With improved hydrophobicity, these nanocrystals can disperse in non-aqueous solvents and be more compatible with hydrophobic polymers. Therefore, non-aqueous solution mixing techniques are possible for preparing well-dispersed polymer/polysaccharide nanocrystals nanocomposites. 

Greiner A, Wendorff JH (2007) Electrospinning a fascinating method for the preparation of ultrathin fibers. Angew Chem Int Ed 46 5670-5703 Grunnert M, Winter WT (2002) Nanocomposites of cellulose acetate butyrate reinforced with cellulose nanocrystals. J Polym Environ 10 27-30 Habibi Y, Dufresne A (2008) Highly filled bionanocomposites from functionalized polysaccharide nanocrystals. Biomacromolecules 9 1974-1980... 

Ljungberg N, Cavaille J-Y, Heux L (2006) Nanocomposites of isotactic polypropylene reinforced with rod-like cellulose whiskers. Polymer 47 6285-6292 Lu Y, Weng L, Cao X (2005) Biocomposites of plasticized starch reinforced with cellulose crystallites from cottonseed linter. Macromol Biosci 5 1101-1107 Lu J, Wang T, Drzal LT (2008) Preparation and properties of microfibrillated cellulose polyvinyl alcohol composite materials. Compos Part A 39A 738-746 Magalhaes WLE, Cao X, Lucia LA (2009) Cellulose nanocrystals/cellulose core-in-shell nanocomposite assemblies. Langmuir. doi 10.1021Aa901928j Malainine ME, Mahrouz M, Dufresne A (2005) Thermoplastic nanocomposites based on cellulose microfibrils from Opuntiaficus-indica parenchyma cell. Compos Sci Technol 65 1520-1526 Marchessault RH, Sundararajan PR (1983) Cellulose. In Aspinall GO (ed) The polysaccharides. Academic, New York... 

Dong XM, Revol JF, Gray DG (1998) Effect of microcrystallite preparation conditions on the formation of colloid crystals of cellulose. Cellulose 5 19-32 Dubief D, Samain E, Dufresne A (1999) Polysaccharide microcrystals reinforced amorphous poly (beta-hydroxyoctanoate) nanocomposite materials. Macromolecules 32 5765-5771 Dufresne A (2000) Dynamic mechanical analysis of the interphase in bacterial polyester/cellulose whiskers natural composites. Compos Interface 7 53-67 Dufresne A (2003) Interfacial phenomena in nanocomposites based on polysaccharide nanocrystals. Compos Interface 10 369-387... 

Polymer nanocomposites can be synthesized using cellulose in the form of cellulose nanocrystals or CWs. Pure cellulose is a biopolymer, specifically the polysaccharide of D-anhydroglucose units connected through the (1-1,4-glycosidic ether bond [31], as shown in Figure 6.2. 

Habibi Y, Dufresne A. Highly filled bionanocomposites from functionalized polysaccharide nanocrystals. Biomacromolecules 2008 9 1974-1980. 

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