Starch nanoparticles

A similar procedure was adopted for synthesis of nanoparticles of cellulose (CelNPs). The polysaccharide nanoparticles were derivatised under ambient conditions to obtain nanosized hydrophobic derivatives. The challenge here is to maintain the nanosize even after derivatisation due to which less vigorous conditions are preferred. A schematic synthesis of acetyl and isocyanate modified derivatives of starch nanoparticles (SNPs) is shown in scheme 3. The organic modification was confirmed from X-ray diffraction (XRD) pattern which revealed that A- style crystallinity of starch nanoparticles (SNPs) was destroyed and new peaks emerged on derivatisation. FT-IR spectra of acetylated derivatives however showed the presence of peak at 3400 cm- due to -OH stretching indicating that the substitution is not complete. 

Chakraborty, S., Sahoo, B., Teraka, I., Miller, L. M., Gross, R. A. (2005). Enzyme-Catalyzed regioselective modification of starch nanoparticles. Macromoleculess 38,61-68. 

Shi, A. Li, D. Wang, L. Adhikari, B. Rheological properties of suspensions containing cross-linked starch nanoparticles prepared by spray and vacuum freeze drying methods. Carbohydr. Polym. 2012, 90 (4), 1732-1738. 

Likhitkar, S. Bajpai, A.K. Magnetically controlled release of cisplatin from superparamagnetic starch nanoparticles. Carbohydr. Polym. 2012, 87 (1), 300-308. 

Cimi, C.K. Abraham, T.E. Hydrophobic grafted and cross-linked starch nanoparticles for drug delivery. Bioprocess Biosyst. Eng. 2007, 30 (3), 173-180. 

In most recent studies, new processes have been tried out to produce starch nanoparticles by (i) precipitation of amorphous starch by Ma et al and Tan et al. (ii) combining complex formation and enzymatic hydrolysis by Kim and Lim, yielding nanocrystals i.e. complexed with lipids), and... 

Figure 14.10 Different approaches to producing crystaUine and amorphous starch nanoparticles.

The nanocomposite materials were also developed from acetylated and hexamethylenediisocyanate (HMDI) modified starch nanoparticles by a commercial milling process. The bionanocomposites showed superior strength... 

Figure 14.16 SEM of the fractured surfaces of (a) unfilled NR, NR filled with (b) 5 and (c, d) 30 wt% of starch nanocrystals, NR filled with (e) 5 and (f) 30 wt% of ASA-modified particles, and NR filled with (g) 5 and (h) 30 wt% of Pl-modified starch nanoparticles.

Figure 14.17 Effect of various fillers on (a) tensUe strength and (b) % elongation of nanocomposites at 30 phr loading of waxy starch (SW), starch nanoparticles (SNP), HMDI-modified SNP (SMI), acetylated SNP (SNAC). (Reproduced from reference 89 with permission from Elsevier.)...

X. Ma, R. J. Jian, P. R. Chang, and J. G. Yu, Fabrication and characterization of citric acid-modified starch nanoparticles/plasticized-starch composites. Biomacromolecules 9(11), 3314-3320 (2008). 

Fig. 2 Release profile of EFA (filled squares), testosterone (open squares), and caffeine (crossed squares) from propyl starch nanoparticles [35]...

Rutkaite R, Bendoraitiene J, Klimaviciute R, Zemaitaitis A (2012) Cationic starch nanoparticles based on polyelectrolyte complexes. Int J Biol Macromol 50 687... 

Enzyme-Catalyzed Regioselective Modification of Starch Nanoparticles... 

Incorporation of starch nanoparticles within reverse micelles of AOT/isooctane/H20 microemuisions A concentrated aqueous solution of starch nanoparticles (0.25g/ml) was added dropwise with vigorous stirring to SOml of 0.1 M AOT/anhydrous isooctane solution in a round bottom flask capped with a rubber septum. The dropwise addition was continued. Throughout this process the solution remained clear and phase separation did not occur. This gave reverse micelles of AOT coated starch nanoparticles in isooctane. The isooctane was removed under reduced pressure by using a rotavaporator. The AOT coated micelles were further dried (30°C, 6hrs, 30mm Hg). A similar procedure was adopted to incorporate starch nanoparticles in reverse micelles of CTAB/chloroform and TritonX-lOQ/toluene where, in place of AOT/isooctane, the surfactant/solvent systems used were CTAB/chloroform and TritonX-100/toluene. 

Incorporation of non>imniobilized Candida antartka Lipase B (CALB) within AOT-coated starch nanoparticles Starch nanoparicles (2.2 g) and SP-... 

Acylation of starch nanoparticles using SP>525 The acylation of AOT-coated starch nanoparticles with vinyl stearate was performed as described above except that the catalyst (CALB) was incorporated within the microsphoes instead of as part of heterogeneous Novozyme-435 beads. 

Scheme 1. Reactions between AOT coated starch nanoparticles with different acylating agents ...

The reaction between vinyl stearate and AOT-coated starch nanoparticles was performed for 24hrs, at 40 C, with a 3 1 mol/mol ratio of vinyl stearate to glucose residues. The peak positions and assignments are listed in the... 

Figure 1. DEPT-135 (75 MHz) spectra recorded in DMSO-d6 of A) native starch nanoparticles(l) B) vinyl stearate modified starch nanoparticles (4) with D.S. =0.8 (showed the carbon signals for sugar ring)...

Reaction time 24h starch nanoparticles Novozym 435=10 l(wAv) ratio of... 

Acylation of AOT-coated starch nanoparticles with maleic anhydride The... 

Reaction progress with time The effect of reaction time on the D.S. for acylations of AOT-coated starch nanoparticles with vinyl stearate, CL, and maleic anhydride are shown in Figure 2 and discussed below. Acylation with vinyl stearate starts after a 2 h lag period and by 24 h reached D.S. 0.7. Extending the reaction time to 48 h showed at most an increase in the D.S. to 0.8. The lag period observed for stearate acylation is likely due to the immiscibility of hydrophobic vinyl stearate and hydrophilic starch molecules. However, once a low degree of stearate ester formation occurred the solubility of vinyl stearate in the hydrophobically modified starch nanoparticles increases thus accelerating the reaction. In contrast, a lag period was not observed for the reaction with CL. This is consistent with a relatively higher miscibility of CL than vinyl stearate with the starch nanoparticles. 

Maleation of starch nanoparticles occurred slowly. In 12h the D.S. was 0.1 and it increased to 0.4 by 48h. The reactions with maleic anhydride were performed in the presence of hydroquinone to avoid the possibility of free-radical side reactions. Furthermore, when succinic anhydride was used in place of maleic anhydride, its reactivity was similarly slow. 

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