# Research Progress of Polysaccharide-Gold Nanocomplexes in Drug Delivery
## 3 Preparation of polysaccharide Gold Nanoparticles  
AuNPs have several advantages, such as inertness, non-toxicity, good biocompatibility, a large specific surface area, and ease of modification, making them widely used in drug delivery. AuNPs constitute a diverse family of nanoparticles, which includes nanoclusters, nanocages, nanowires, nanorods, nanotubes, nanostars, nanocombs, nanoribbons, and nanoshells [63]. Two main strategies for synthesizing gold nanoscale particles are top-down and bottom-up. Top-down synthesis involves techniques such as laser ablation, ion sputtering, ultraviolet and infrared radiation, etc. On the other hand, bottom-up synthesis methods involve the reduction of Au(iii) to Au and can be categorized into chemical and biosynthetic processes [64]. Chemical reduction involves the reduction of gold ions using a reducing agent such as sodium borohydride or citrate. This is a relatively simple and widely used method for preparing gold nanoparticles. However, control over the size and shape of the resulting particles can be quite limited. The use of physical methods for the synthesis of AuNPs allows for precise control of the size and shape of the nanoparticles, minimal chemical contamination, and the ability to produce AuNPs with application-specific properties. However, it is important to carefully optimize the process parameters in order to obtain the desired nanoparticle properties. Biosynthesis is environmentally friendly and usually allows for better control over the size and shape of the particles. However, optimizing and controlling the synthesis process can be more challenging. Several syntheses of gold nanoscale are summarized in Table 2.  
The main physical methods for synthesizing AuNPs include physical fragmentation, evaporation condensation, plasma precipitation, and sputtering. In addition, gold nanoscale can be synthesized using UV-induced photochemistry, laser ablation, and ultrasound-assisted synthesis. Figure 3B,C present synthetic reduction schemes for AuNPs using UV-induced, ultrasonic, laser ablation, and plant extract-based AuNPs, respectively. [PERSON] et al. utilized the sputtering method to load AuNPs onto the surfaces of carbon nanocoils. This technique resulted in the creation of a visible-light-driven photocatalyst [65]. [PERSON] et al. conducted a study where they successfully synthesized chitosan/gold nanocomposites (Cs/Au) through \(\gamma\)-irradiation. The authors' findings demonstrated that these Cs/Au nanocomposites exhibit remarkable antimicrobial and anti-biofilm activity. Additionally, they showed the ability to inhibit the growth of cancer cells. These significant results underscore the immense potential of Cs/Au nanocomposites in the biomedical and pharmaceutical fields [66]. Chemical methods are widely used for the synthesis of AuNPs. Turkevich-Frens first used the most common and long-established method for preparing AuNPs in 1951(Figure 3A) [67]. This method utilizes relatively green reagents, and the synthesis process is reasonably simple. It involves the formation of 10-20 nm AuNPs by reducing chloroauric acid in boiling water using sodium citrate as a reducing agent and stabilizer. However, the concen \begin{table}
\begin{tabular}{c c c} \hline \hline  & & physical fragmentation \\ \cline{2-3} top-down & physical synthesis & \
\begin{tabular}{c} evaporation condensation \\ \end{tabular} \\ \cline{2-3}  & & plasma precipitation \\ \cline{2-3}  & & sputtering \\ \hline \multirow{3}{*}{bottom-up} & chemical synthesis &
\begin{tabular}{c} Turkevich–Frens \\ \end{tabular} \\ \cline{2-3}  & & Brust-Schiffrin \\ \cline{2-3}  & biosynthesis \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Methods for synthesizing AuNPs. tration of NPs was relatively low. Researchers have been studying the impact of different factors, including reagent concentration, order of reagent addition, the addition of other ions, pH, temperature, time, and synthesis method on the size of gold nanoscale using [PERSON]'s method.