# Research Progress of Polysaccharide-Gold Nanocomplexes in Drug Delivery
## 6 Drug Release from Polysaccharide-AuNPs
Additionally, gold nanostructures possess excellent biocompatibility and exhibit strong light absorption in the NIR region. Consequently, they are considered highly suitable for PTT applications [146]. The induction of PTT for cancer treatment using gold nanoparticles was first published in 2003 [147]. PTT therapies, such as antibacterial and antitumor treatments, are widely used in various biological fields. Polysaccharide-AuNPs, in particular, have been found to induce a favorable immune response effectively at the tumor site. This leads to the conversion of an immunosuppressive TME into an immunostimulatory one. In PTT, NIR absorbers are typically employed to eradicate cancer cells. These absorbers efficiently convert light energy into heat, thereby increasing the local temperature of the tumor. Consequently, the elevated temperature \"burns\" the cancer cells and destroys them. Using AuNPs conjugated to cisplatin, the antitumor effect can be enhanced by delivering and accumulating cisplatin at the tumor site. Under near-infrared light irradiation, this strategy maximizes the potential to treat tumors [148]. [PERSON] et al. conducted a study in which poly (2-methylacrylic acid (3-amido-2,4,6-triiodobenzoic acid))/polyethyleneimine/hyaluronic acid modified AuNSs, referred to as PMATIB/PEI/Au/HA. These nanoshells were injected intravenously into mice with human mammary carcinoma MCF-7 cell-loaded tumors. The researchers observed that this injection significantly enhanced the contrast of CT imaging  
Figure 7: The photothermal effect of gold nanoscale in tumor therapy: (**A**): The LSPR phenomenon on the surface of gold nanoparticles under irradiation at specific light wavelengths. Reproduced with permission from Ref. [140]. (**B**): Illustration for preparing TPPS/QCS-SH/AuNPs and their anticancer properties by PDT/PTT. Reproduced with permission from Ref. [143]. Copyright 2018, American Chemical Society. (**C**): Enhanced photo-immunotherapy by the combination effect of PTT-induced immune activation and M2-TAMs depletion-induced ITME modulation based on HA-AuNRs/M-M2 pep. Reproduced with permission from Ref. [118]. 2021 Published by Elsevier B.V.  
of the tumors. Moreover, this effect was achieved while selectively ablating the tumors through an increase in local temperature under NIR laser irradiation [149]. [PERSON] et al. developed the hybridized hyaluronic acid gold nanocluster (AuNCs-HyNA). This material exploits the photothermal enhancement of photodynamic tumor ablation, achieved by incorporating the antitumor drug vitexoporfin. After reaching the tumor site via targeting hyaluronic acid, the material facilitates the decomposition of the hyaluronic acid, allowing the gold nanoclusters and the drug to enter the tumor tissue and exert a therapeutic effect [150]. The insertion of gold nanoclusters into carrageenan gum formed an antimicrobial hydrogel platform with a photothermal product, which showed sound antimicrobial effects against both Gram-positive and Gram-negative bacteria in vitro, and it is worthwhile to investigate other gold nanomaterials and whether the same antimicrobial effect can be produced against different strains of bacteria [151]. pH-responsive gold nanodrug carriers are widely used owing to the unique tumor microenvironment of tumor tissues, characterized by slightly acidic extracellular pH (\(\sim\)6.0-7.0) and intranuclear pH (\(\sim\)4.5-6.5) [152; 153], it has proven to be an ideal tool for delivering therapeutic agents to lesions. In a study by [PERSON] et al., dextran and pullual polysaccharides were used to encapsulate AuNRs, materials capable of self-destruction in the acidic environment of tumor cells and under conditions of high glutathione concentration. This approach enables targeted drug release specifically within tumor cells--the pH of the tissue changes after bacterial infection [154]. [PERSON] et al. utilized this property to design a pH-dependent nanocar for delivering curcumin to the site of bacterial infection.