The development of organic polymer materials for disinfection and sterilization is thought of as one of the most promising avenues to solve the growth and spread of harmful microorganisms. Here, a series of linear polyisocyanide quaternary ammonium salts (L-PQASs) with different structures and chain lengths were designed and synthesized by polymerization of phenyl isocyanide monomer containing a 4-chloro-1-butyl side chain followed by quaternary amination salinization. The resultant compounds were characterized by 1H NMR and FT-IR. The antibacterial activity of L-PQASs with different structures and chain lengths against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) was evaluated by determining the minimum inhibitory concentrations (MICs). The L-POcQAS-M50 has the strongest antimicrobial activity with MICs of 27 μg/mL against E. coli and 32 μg/mL against S. aureus. When the L-PQASs had the same polymerization degree, the order of the antibacterial activity of the L-PQASs was L-POcQAS-Mn > L-PBuQAS-Mn > L-PBnQAS-Mn > L-PDBQAS-Mn (linear, polyisocyanide quaternary ammonium salt, monomer, n = 50,100). However, when L-PQASs had the same side chain, the antibacterial activity reduced with the increase of the molecular weight of the main chain. These results demonstrated that the antibacterial activity of L-PQASs was dependent on the structure of the main chain and the length of the side chain. In addition, we also found that the L-POcQAS-M50 had a significant killing effect on MK-28 gastric cancer cells.

The development of non-polluting and non-hazardous polymeric antimicrobial agents has become a hot issue in current research and development. Among them, polymer quaternary ammonium salts are thought to be one of the most promising materials for antibacterial efficacy. Here, we present an efficient strategy for synthesizing polyisocyanide quaternary ammonium salts (PQASs) with a novel star-shaped structure. Benefitting from the novel structure, increased cation density and enhanced water solubility, the prepared star polyisocyanide quaternary ammonium salts (S-PQASs) exhibit excellent antibacterial properties against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). In particular, S-POcQAS-M50 (where M stands for isonitrile monomer and 50 stands for the initial feeding ratio) showed the best antimicrobial activity with minimum inhibitory concentration (MIC) of 17 and 20 µg/mL against E. coli and S. aureus, respectively. It was also found that the unique star-shaped structure can give QASs with improved antimicrobial performance compared with our previously prepared linear quaternary ammonium salts (L-PQASs). These results demonstrated that the antibacterial activity of QASs is closely related to its structure. This work provides an idea for the design of efficient polymeric antimicrobial agents.

Much research has demonstrated that metabolic imbalances of biothiols are closely associated with the emergence of different types of disease. In view of the significant effect of biothiols, quantitative evaluation and discrimination of intracellular Cys/Hcy and GSH in complex biological environments is very important. In this study, probe CDS-NBD, synthesized by attaching 2,4-dinitrobenzenesulfonate (DNBS, site 1) and nitrobenzoxadiazole (NBD, site 2) as the highly sensitive and selective dual response site for thiols onto the coumarin derivative 7-hydroxycoumarin-4-acetic acid, exhibited large separation of the emission wavelengths, fast response, notable fluorescence enhancement, excellent sensitivity and selectivity to Cys/Hcy and GSH over other biological species. Additionally, CDS-NBD could make a distinction between two different fluorescent signals, GSH (an obvious blue fluorescence) and Cys/Hcy (a mixed blue-green fluorescence). Further study on imaging of Cys/Hcy and GSH in vivo by employing probe CDS-NBD could also be successfully achieved.

Photodynamic therapy (PDT) is an innovative and perspective antineoplastic therapy. Tetra-α-(4-carboxyphenoxy) phthalocyanine zinc (TαPcZn)-mediated PDT (TαPcZn-PDT) has shown antitumor activity in some tumor cells, but the manner in which caspase-1 is involved in the regulation of apoptosis and pyroptosis in the TαPcZn-PDT-treated breast cancer MCF-7 cells is unclear. Therefore, effects of TαPcZn-PDT on cytotoxicity, cell viability, apoptosis, pyroptosis, cellular reactive oxygen species (ROS), mitochondrial membrane potential (ΔΨm), caspase-1, caspase-3, and nuclear transcription factor-κB (NFκB) in MCF-7 cells was firstly examined in the present study. The findings demonstrated that TαPcZn-PDT resulted in the increase in cytotoxicity and the percentage of apoptotic and pyroptotic cells, the reduction in cell viability and ΔΨm, the production of ROS and the activation of caspase-1, caspase-3 and NFκB in MCF-7 cells. Furthermore, the results also revealed that siRNA-targeting caspase-1 (siRNA-caspase-1) attenuated the effect of TαPcZn-PDT on apoptosis, pyroptosis and the activation of caspase-1, caspase-3 and NFκB in MCF-7 cells. Taken together, we conclude that caspase-1 regulates the apoptosis and pyroptosis induced by TαPcZn-PDT in MCF-7 cells.