## 2 Metal-Based Carbohydrate Drug Conjugates
The antiproliferative activity of complexes **8a-c** was evaluated on A431 and SVT2 cancer cells and HaCaT and BALB/c3T3 normal cells. The obtained IC\({}_{50}\) values are in the high micromolar range (35-100 \(\upmu\)M), with the highest selectivity index in the case of complex **8c**. The traditional circular dichroism and fluorescence techniques suggested that this class of complexes can alter the DNA conformation by intercalation, especially in the iodide derivative **8c**. Moreover, crystallization with RNase A and egg white lysozyme proteins (HEWL) highlighted the ability of these gold-NHC complexes to bind specific protein residues. As far as concerns the position and number of glycosidic moieties in a gold complex, [PERSON] and colleagues have investigated a selection of dinuclear gold derivatives  
Figure 2: (**A**) Mononuclear gold complexes prepared by [PERSON] group; (**B**) Digold complexes published by [PERSON] and colleagues. (Figure 2B) [58]. In particular, complexes **9a-b** and **10** were synthesized and tested towards A431 and SVT2 cancer cells and HaCaT and BALB/c3T3 normal ones. Notably, the anticancer activity of the corresponding Au(III) complexes was not explored due to their poor stability in the physiological solution. Unfortunately, both neutral complexes **9a-b** exhibited high IC\({}_{50}\) values (>100 uM). On the contrary, the biscationic complex **10** showed a moderate cytotoxicity (IC\({}_{50}\) = 85 uM) and a certain selectivity towards cancer cells. The well-known antiarthitic and antitumor properties of _Auranofin_ have prompted many research groups to use thioglucidic residues in the design of new promising metallodrugs. Taking advantage of the _weak-base route_[59], [PERSON], [PERSON] and [PERSON] have recently reported the S-H activation of thiosugars under mild conditions, affording the desired gold complexes **11-14** with a wide scope of NHC ligands (Figure 3A) [60]. The synthesized complexes have been tested in relevant human cancer cell lines such as A549, HT-29 and MDAMB-231. All the tested compounds exhibited a remarkable anticancer activity, with IC\({}_{50}\) values in the low micromolar or sub-micromolar range. Interestingly, the most promising results were obtained in the case of thioglucene tetraacetate as thiosugar. As far as concerns the application of silver complexes in this area of research, [PERSON], [PERSON] and [PERSON] have developed a solvent-free procedure (via _ball milling_) for the preparation of Ag(I) complexes **15a-d** (see Figure 3B) [61]. In particular, a selection of imidazolium salts bearing thiosugars in _para_ position of the NHC-aryl substituents and Ag\({}_{2}\)O reacts smoothly in the ball mill apparatus, affording the desired complexes in high yields. The anticancer activity of these Ag-NHC complexes and their azolium precursors was evaluated on HCT 116 cancer cell line. The obtained results have demonstrated the superior antiproliferative activity of the silver complexes with respect to their azolium precursors. The highest activity was achieved with complex **15a**[61]. Organoalladium complexes have recently been considered as promising anticancer agents, owing to their remarkable in vitro, ex vivo and in vivo cytotoxicity even on cisplatin-resistant tumour models [62; 63; 64; 65]. Recently contributions from our group have demonstrated the interesting anticancer properties of Pd(II)-allyl complexes bearing NHC and phosphine ligands [67]. More specifically, the use of PTA (1,3,5-triaza-7-phosphoaadamantane) as phosphine ligand improves the solubility and stability of the Pd complexes in physiological conditions as well as their selectivity towards cancer cells. Moreover, this category of organo Palladium derivatives seems to target mitochondria. With the aim of further improving their activity and selectivity, in 2020, we reported the use of glucosidic-NHCs as ancillary ligands in Pd(II)-allyl complexes.