# Synthesis of Star Nanoparticles and Their Applications for Bioactive Compound Encapsulation
## 3 Encapsulation Methods
### Direct Encapsulation
#### 3.1.1 Nanoprecipitation Starch Sources  
The most common synthesis method used for direct encapsulation is through nano-precipitation method. Many authors use this method for the encapsulation of different active compounds and also, different types of starches can be used, where corn starch is the most common of them.  
#### 3.1.1 Nanoprecipitation Starch Sources  
In recent studies, acetylated corn starch was formulated with high and low degree of substitution (DS) where the antibiotic-loaded SNPs were prepared by a nanoprecipitation  
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process by [PERSON] et al. Acetylated starch with different DS was dissolved and mixed with the antibiotic (ciprofloxacin) in acetone as the organic phase. Subsequently, distilled water was added into the solution containing the polymer under stirring until the acetone was completely evaporated [16]. In the same way, [PERSON] et al. synthesized diclofenac sodium (DS) loaded cross-linked corn SNPs by modified nanoprecipitation method. The aqueous phase contained corn starch dispersed in distilled water containing NaOH under continuous high-speed homogenization. Tween 80 was dissolved in distilled water containing different amounts of the drug was added dropwise to the starch solution under a high rate of homogenization and then distilled water containing different amounts of the crosslinking agent (sodium tripolyphosphate) was added to the solution. The resulting DS encapsulated crosslinked SNPs were subsequently precipitated with absolute ethanol and further purified by centrifugation and washing two times with absolute ethanol/water to remove unreacted compounds and finally with absolute ethanol [14]. Other authors reported the loading of _Triphala churna_ in corn SNPs following the graft copolymerization method, which consists of loading the drug in gelatinized starch. This is accomplished by heating starch in NaOH solution. Thereafter, the gelatinized starch and the drug were mixed, and acetone is added dropwise under constant stirring for the conversion of the solubilized starch into SNPs [79]. Also, some authors used native waxy corn starch that was debranched with pullulanase to obtain short linear glucans for the synthesis of SNPs for encapsulation of essential oils (EO). The debranched starch was precipitated in presence of an excess of absolute alcohol and washed with aqueous dimethyl sulfoxide solution. The starch was dispersed in deionized water and then autoclaved. Synthesis and encapsulation were carried out by precipitating the dissolved EO in hot ethanol into the starch solution under constant stirring [15]. The loading of drugs in porous starch nanoparticles was also studied by [PERSON] et al. in 2019. The paclitaxel used as the drug was completely dissolved in acetone and then insoluble porous corn starch (starch treated with \(\alpha\)-amylase and glucoamylase in weak acid) was added under stirring. Subsequently, the porous starch adsorbed with the paclitaxel acetone solution was added to deionized water containing hydroxypropyl methyl cellulose and then stirred. At the same time, the load of paclitaxel in porous starch was also studied as a control group [78]. [PERSON] et al. also synthesized lutein-loaded SNPs in order to find a better dispersibility of lutein in water and its stability against chemical oxidation. Corn starch or amylose was mixed with deionized water at different concentrations. These solutions were heated under continuous stirring until the starch was gelatinized. Subsequently, half of an ethanol solution containing lutein was added dropwise. After cooling the mixture to room temperature, the same volume of the ethanol and lutein solution was added again, and the precipitate obtained was washed with ethanol. In this study, an oxidation rate of 25% for the pure lutein encapsulated in SNPs was obtained [19].