# Research Progress of Polysaccharide-Gold Nanocomplexes in Drug Delivery
## 1 Introduction
Active targeting promotes active cellular uptake of nanoparticles by cancer cells, whereas passive targeting allows nanoparticles to be efficiently localized in a tumor microenvironment [4]. Passive targeting refers to the accumulation of small molecules at the tumor site through the EPR effect. Due to the EPR effect, nanocarriers with a particle size of less than 200 nm can easily penetrate the tumor vasculature system, resulting in passive targeting, which produces therapeutic effects in the tumor tissue. Passively targeted drug delivery systems mainly include liposomes, microemulsions, and nanoparticles [5]. In addition, combining nanocarriers with pH-dependent polymers can be utilized to target tumor cells actively, facilitating intracellular drug release from cancer cells [6]. Active targeting means modifying the surface of nanoparticles using the targeting ligands to direct to the specific receptors overexpressed on tumor cells precisely. The targeted ligands include antibodies, polysaccharides, and proteins, among others. The active targeting nanoparticles passively exude blood vessels into tumor tissue [7]. This recognition stimulates receptor-mediated endocytosis, which in turn internalizes nanocarriers and enhances their ability to exert therapeutic effects on tumors [8]. Several classifications of nanomedicine delivery systems can be grouped into three types based on the drugs they deliver: nanosystems for transporting chemical drugs, nanosystems for transporting peptide- or protein-based agents, and nanosystems for transporting nucleic acids. Furthermore, these nanodelivery systems can be categorized based on the nanocarr used, including liposomes, polymer carriers such as microspheres, hydrogels, polymeric NPs, dendrimers, and nanowires, metallic NPs (e.g., Au, Ag, Ti), carbon nanodevices (e.g., nanotubes, nanodiamonds (NDs), graphene), and inorganic particles (e.g., silica particles) [9; 10]. There are various drug delivery systems available for administering drugs to the targeted area of action. Each type of material possesses its own advantages and disadvantages, and the selection of a particular method should be based on individual clinical needs and considerations. Nano-drug delivery systems heavily rely on the utilization of nanoparticles, which are categorized as inorganic materials, organic small molecules, and polymers. The physicochemical properties are altered by changing the chemical composition, structure, size, and shape of the surface. The main types of distributions are shown in Figure 1. Additionally, Table 1 summarizes the advantages and disadvantages of different nanodelivery carriers. This comprehensively overviews the various distribution methods and their associated benefits and drawbacks. Figure 1: Application summary of nanodelivery systems. The associated image materials were prepared by Figdraw 2.0. Gold nanoparticles (AuNPs) have gained attention in the field of drug delivery due to their superior properties compared to liposomes, polymers, dendrimers, and metal nanoparticles [25]. These properties include good biocompatibility, a large specific surface area, surface modifiability, and excellent stability and dispersion characteristics [26]. In addition to their effectiveness in delivering various drugs, such as proteins, peptides, nucleic acids, and macromolecules, AuNPs can also stabilize and enhance the efficacy of other drug delivery carriers [4]. AuNPs have firm local surface plasmonic resonance (LSPR), high X-ray radiation absorption capacity, and photothermal conversion performance. These characteristics make them attractive for biosensors, catalysis, and tumor therapy applications, including photothermal and radiation therapy. The potential of AuNPs in these areas is promising [27; 28; 29]. Additionally, such modifications enable the efficient delivery of drugs to specific targets, thereby enhancing the application of gold nanoparticles in drug deliv