Diseases induced by bacterial infections increasingly threaten the health of people all over the world; thus, it is urgent and significant to early diagnose and effectively eliminate infections to save people’s lives. To this end, we synthesized an intelligent hydrogel that integrated in situ visualized diagnosis and photothermal therapy of bacterial infections. By simply and subtly incorporating pH-sensitive bromothymol blue (BTB) and near-infrared (NIR)-absorbing conjugated polymer (termed as PTDBD) into thermosensitive chitosan (CS)-based hydrogel, the synthesized BTB/PTDBD/CS hydrogel can diagnose the acidic microenvironment of Staphylococcus aureus (S. aureus) biofilm and infected wounds by showing visualized color change. After rapid diagnosis, the hydrogel can immediately treat the infection site by local hyperthermia under irradiation of NIR laser (808 nm) and even the stubborn biofilm that is difficult to eradicate. Since the dominating antibacterial mechanism is hyperthermia, the hybrid hydrogel shows broad-spectrum antibacterial activity against Gram-positive, Gram-negative, and drug-resistant bacteria. In addition, it has low cytotoxicity to normal cells and no effect on the main organs of mice. It paves a brand new avenue to develop smart and facile diagnosis and a treatment platform for bacterial infections.

A novel NIR-absorbing and water-soluble conjugated polymer (PTDBD) for single-NIR-light induced synergetic photothermal/photodynamic therapy was developed.

Phototherapy has great advantages in combating bacterial infection, in particular, those therapies mediated by near-infrared light. To advance phototherapy for bacterial infections, a positively charged conjugated polymer (termed PTDBD) with near-infrared light-triggered activity is employed for antimicrobial therapy in this paper. The quaternary ammonium groups in side chains of PTDBD can benefit from the interaction between the polymer and negatively charged membrane of bacteria, and such a structure can also induce the aggregation of bacteria to improve local antibacterial efficiency. Upon single near-infrared light irradiation, simultaneous reactive oxygen species (ROS) and heat generated by the polymer PTDBD can effectively kill bacteria at low treatment concentration (40 μg·mL–1) and low light density (1.0 W·cm–2) toward both Gram-positive bacteria (Staphylococcus aureus) and Gram-negative bacteria (ampicillin-resistant Escherichia coli TOP 10). For fungi (Candida albicans), a higher treatment concentration of PTDBD is needed to kill at the same light density. Finally, the dual phototherapy is also employed to treat the bacteria-infected wound of mice with no tissue damage observed. The integration of positive charges, ROS, and heat provides a highly efficient and broad spectrum antimicrobial strategy for further treatment of bacterial infections in vivo.

Colloidal semiconductor CdSe-based quantum dots (QDs) show undesirable photoluminescence (PL) intermittency with frequent and long-lasting dark states due to positively charged states, significantly limiting QD optoelectronic and photonics applications. Here, we show that p-phenylenediamine (PPD) can completely suppress the long-lasting dark states in the PL intensity trajectories for single CdSe-based QDs in the full-color emission range from 459 to 800 nm, while hardly influencing any other PL properties of the QDs, such as the PL intensity, lifetime, and emission spectra. The suppression mechanism is investigated by comparing PPD to another amine compound, N,N-dimethylaniline. With a reasonable highest occupied molecular orbital energy, PPD facilitates electron transfer from PPD to the positively charged QDs, thus, neutralizing the extra hot holes via an Auger-assisted process. Therefore, the positively charged states of QDs and the PL intermittency could be eliminated. Moreover, we demonstrate that PPD can effectively suppress the photobleaching of CdSe-based QDs, and the average survival time of single QDs can be extended from a few minutes to more than 1 h. Finally, we demonstrate the application of PPD-stabilized QDs to single-particle tracking and HeLa cell imaging under relevant biological conditions and show their promising potential in various biomedical applications.

Incomplete local treatment of solid tumors is the main cause of tumor difficult to cure, and easily leads to tumor metastasis and recurrence. The dense external matrix and hypoxic microenvironment of solid tumors severely restrict the therapy efficacy of local tumors. Enhancing the infiltration ability of agents to tumor tissues and adapting the therapy mode favored to hypoxic microenvironments are beneficial to improve the cure rate of tumors. In this work, we designed and developed a self-assembled biomaterial with a cascade effect triggered by near-infrared light. The self-assembly was combined of biotin, phase change material (PNIPAM), photochemical agent (ATT-2), and alkyl radical generator (AIPH). In the assembly, biotin acted as a targeted group. ATT-2 was used to provide heat to synergistically induce the phase change and decompose alkyl radicals. The superficial and deep tumors were ablated by heat and alkyl radicals with white light irradiation of the assembly, respectively. The assay in vivo showed that the self-assembly could effectively eliminate local lesions of solid tumors. This work provides new insights for improving the cure rate of tumors, which not only develops biomaterials adapted to the tumor microenvironment, but also proposes new therapies for complete elimination of solid tumors.