Tannic Acid-Modified Silver Nanoparticles for Antibacterial and Anticancer Applications

In recent years, antibacterial nanosystems with loadingand deliverycapacity for anticancer agents have received increasingly widespreadattention in the field of cancer treatment involving bacterial infection.Silver nanoparticles (AgNPs) are the most representative and widelyused biocompatible metallic nanoparticles, which possess long-lastingand broad-spectrum antibacterial activity. However, conventional AgNPsare difficult to load and deliver anticancer agents directly becauseof their relatively inert surfaces. Herein, biocompatible silver nanoparticles(TA-AgNPs) were prepared via a simple approach inwhich tannic acid (TA) served as a green reducingand stabilizing agent. The resultant TA-AgNPs have low cytotoxicityagainst normal cells and exhibit significant antibacterial activity.The minimum inhibitory concentration (MIC) value of TA-AgNPs toward Escherichia coli was about 16 mu g/mL, and theelimination rate of TA-AgNPs at a concentration of 0.5 mg/mL was above99 and 93% at 6 h for E. coli and Staphylococcus aureus, respectively. TA-AgNPs havea good ability to load and deliver anticancer drug epirubicin hydrochloride(EPI). EPI can be adsorbed onto the surface of TA-AgNPs by strongelectrostatic interaction between TA and EPI. The TA-AgNPs/EPI nanodrugdisplays a pH- and glutathione (GSH)-sensitive drug release performancethrough the protonation of phenolic hydroxyl groups in TA under anacid condition and the disassociation of TA molecules from the surfaceof AgNPs due to the ligand exchange reaction between GSH thiols andTA molecules. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide (MTT) assay results showed an equal cytotoxicity effect againstHep G2 cells between free EPI and EPI-loaded TA-AgNPs. More importantly,the 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay results indicated that the cytotoxicityof free EPI was significantly reduced in the presence of bacteria,but the resultant EPI-loaded TA-AgNPs could effectively prevent theinfluence of bacteria on the cytotoxicity of EPI. The animal tumorsuppression and anti-infection model assay results indicated goodtumor suppression and antibacterial properties of the TA-AgNPs/EPInanodrug.

Automated summary

In recent years, there has been increasing attention on antibacterial nanosystems for cancer treatment involving bacterial infection. Silver nanoparticles (AgNPs) are widely used for their long-lasting and broad-spectrum antibacterial activity, but their inert surfaces make it difficult to load and deliver anticancer agents directly. This study developed biocompatible silver nanoparticles (TA-AgNPs) using tannic acid as a reducing and stabilizing agent. The TA-AgNPs exhibited low cytotoxicity and significant antibacterial activity. They could also effectively load and deliver the anticancer drug epirubicin hydrochloride (EPI), and showed pH- and GSH-sensitive drug release performance. The TA-AgNPs/EPI nanodrug demonstrated equal cytotoxicity to free EPI against cancer cells and prevented the influence of bacteria on EPI cytotoxicity.