Photoswitchable Silver(I) Complex with Anticancer and Antimicrobial Potential

A photoswitchable silver(I) complex incorporating two arylazopyrazole ligands was synthesized and characterized. The system undergoes efficient and reversible trans–cis and cis–trans photoisomerization upon irradiation at 365 and 530 nm, respectively, with the metastable cis form exhibiting a thermal half-life of 13 days at 37 °C, indicating potential suitability for photopharmacological applications. The complex showed significant dose-dependent toxicity in both cancer (4T1) and normal (NMuMG) murine mammary gland cells. However, the concentration window around 18 μM was identified in which the cis photoisomer is not toxic in both normal and cancer mammary gland cells, while the trans photoisomer is toxic in cancer cells and nontoxic in normal cells. Favorably, in cancer 4T1 cells, the trans photoisomer was more toxic than cisplatin, which in turn was more toxic than the cis photoisomer. Both photoisomers were nontoxic in human prostate cancer (PC3) and nonsmall cell lung cancer (A549) cells. The complex showed higher fungistatic than bacteriostatic activity, with no differences in toxicity between photoisomers. In human keratinocytes (HaCaT), the cis photoisomer was nontoxic, while the LC50 of the trans one in these cells was 10 times higher than its MIC against Aspergillus fumigatus, revealing the potential of the complex as an antifungal agent.