# Synthesis of Star Nanoparticles and Their Applications for Bioactive Compound Encapsulation
## 2 SNP Preparation Method
### Nanoprecipitation
Smaller particle sizes were obtained when the acid hydrolysis method was used with particle sizes approximately between 82 and 92 nm, while sizes between 158 and 180 nm were observed when nanoprecipitation was used [20]. On the other hand, as it was aforementioned, starch can also be added in the aqueous phase in the form of short glucan chain powder dissolved into deionized water and subsequently be mixed with an ethanolic solution added dropwise leading to the starch precipitation. In the study carried out by [PERSON] et al., native wavy maize debranched by pullulanase was used to obtain short linear glucans to synthesize SNPs. Short glucan chains were linear and had a low degree of polymerization compared to the native starch and contributed to a more compact structure formation. Finally, particles with an average particle size of 84 nm were obtained [15]. [PERSON] et al. also synthesized SNPs through a modified solvent displacement method using waxy corn starch which was altered into short linear glucans obtaining a particle size range between 40 and 50 nm but apparent aggregation was observed [21]. Besides, the aqueous phase, in addition to distilled water, may also contain other chemical compounds as sodium hydroxide or DMSO mixed with the starch solution allowing its precipitation by adding absolute ethanol dropwise. [PERSON] et al. synthesized crosslinked corn SNPs by a nanoprecipitation method using a mixture of distilled water and sodium hydroxide as the dispersed phase, sodium tripolyphosphate (STPP) as a crosslinking agent in the presence of Tween 80 as a surfactant. Crosslinkers can enhance the granule stability with new covalent bonds which allows to increase the desired stability conditions [22]. Different amounts of the crosslinking agent were studied, and it was observed that the greater the amount of STPP, the greater the particle sizes. In any case, none of the experiments exceeded particle sizes of 68 nm [14]. In recent studies, [PERSON] et al. also synthesized SNPs using the nanoprecipitation method by modifying main operating parameters. Maize starch was dissolved into an aqueous phase containing sodium hydroxide in the presence or absence of urea since it was recently reported that the interactions between sodium hydroxide and urea improve the solubility of the polymers as sodium hydroxide breaks the hydrogen bonds of the starch and urea prevents self-association of the starch molecules [23]. Then, in order to precipitate the starch in the form of SNPs 1 mL of the starch solution was added into absolute ethanol as the organic phase. Also, the effect of the addition of a cationic surfactant (CTAB) into the aqueous phase was studied. As a result, SNPs from 59 nm to 118 nm were obtained, registering the higher values when surfactant was added into the aqueous phase. The result of this study showed that the total amount of SNPs obtained was greater for urea-containing formulations and fewer agglomeration were observed for an aqueous solution with 8% (_w/v_) NaOH and 10% (_w/v_) urea [24]. [PERSON] et al. also prepared oxidized starch nanoparticles (oxy-SNPs) modifying the native starch by liquid-phase oxidation using H\({}_{2}\)O\({}_{2}\) as the oxidant, followed by chemical dissolution and solvent-free precipitation. Starch was dispersed in ethanol and DMSO was added until the starch was gelatinized and dissolved in the DMSO, then the precipitation of the SNPs was carried out by mixing the starch solution with ethanol. The final size of the oxy-SNPs was confirmed in a scale range of approximately 178 nm [25].