# Synthesis of Star Nanoparticles and Their Applications for Bioactive Compound Encapsulation
## 3 Encapsulation Methods
### Indirect Encapsulation
#### 3.2.1. Bioactive Compound Dissolved in an Aqueous Solution  
One of the most common procedures followed by many authors is to dissolve the drug in an aqueous solution. [PERSON] et al. carried out a study on SNPs as carriers for polyphenols where the SNPs were synthesized through a simple nanoprecipitation method. Four types of polyphenols were used: catechin, epicatechin, epigallocatechin-3-gallate, and proanthocyanidins, dissolved in water. The loaded SNPs were prepared by adsorption experiments and incubated in tubes containing different volumes of polyphenol for different periods of time under constant shaking. Once these times were exceeded, the SNPs were washed three times with water [21]. Also, in 2018, [PERSON] et al. prepared retrograded starch (RS III) nanoparticles for application as a wall material for colon-specific drug delivery by high-speed shearing emulsification using MBAA as the crosslinking agent. The retrograde SNPs were added to 5-fluorouracilacil (5-FU) aqueous solutions which is one of the common drugs for the treatment of colon cancer and finally, the 5-FU concentration was determined using high-performance liquid chromatography (HPLC) in order to obtain the loading capacity and the encapsulation efficiency [36]. In addition, [PERSON] et al. studied two different methods for drug loading: coating and adsorption method. Also, ciprofloxacin was used as the model drug since it is a commonly used antibiotic. The loading of the model drug through the coating method was carried out at the same time as the SNPs synthesis (direct encapsulation) by adding the ciprofloxacin into the emulsion aqueous phase containing the starch and the crosslinking agent. Nevertheless, through the adsorption method SNPs were dispersed into an aqueous solution containing the drug and the adsorption was allowed for 12 h. At last, in both cases, the concentration of ciprofloxacin was determined using UV spectrophotometry. Finally, compared to the coating method, the release of ciprofloxacin from the SNPs was faster when the adsorption method was used [5]. 5-Aminosalicylic acid (5-ASA), which is an anti-inflammatory agent used primarily to treat inflammatory bowel diseases, was used as a model drug to investigate drug loading and controlled release behaviour of crosslinked SNPs synthesized by a microemulsion crosslinking method. SNPs were dispersed in boiled aqueous solution containing the drug with shaking for several days. Subsequently, they were centrifuged and lyophilized to obtain the drug-loaded SNPs in order to determine the drug loading content [84]. [PERSON] et al. prepared SNPs from octenyl succinic anhydride (OSA) starch and 1,4-butane sulfone (OSA-BS SNPs) by using \begin{table}
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**Preparation Method** & **Type of Starch (nm)** & **Particle Size (nm)** & **Encapsulated Compound** & **Evaluation Method** & **Applications** & **Tested On** & **EE (\%)** & **References** \\ \hline High-speed jet & Tapioca & 55.3–120 & Myricetin & / & Food formulations & SIG, SIF in vitro & / & [71] \\ \hline Ultrasound and crystallization & Maize & 351–468 & Tangeretin & UV-vis & Food, pharmaceutical and cosmetic industries & Human microenvironments in vitro & 74–83 & [86] \\ \hline Ball milling & Lotus stem, horse chestnut and water & 419–797 & Resveratrol & Spectrophometry & Food and pharmaceutical oil & SIG, SIF digestion & 76–81 & [54] \\ \hline Ultrasound and nanoprecipitation & Maize & 65–390 & Ardisia compression anthropanins & Differential pH method & Biodegradable food packaging or antioxidant additives & / & 45–52 & [87] \\ \hline \hline \end{tabular}
\end{table} 
Table 3: _Cont._the water dialyzed method for its use to solubilize benzo[a]pyrene (BaP) as a result of the degradation by Fenton process. The drug was introduced in dichloromethane solution and after the solvent evaporation, the starch aqueous solution was added at different concentrations.