Flexible Antibacterial Film Based on Conjugated Polyelectrolyte/Silver Nanocomposites

In this work, we report a flexible film based on conjugated polyelectrolyte/silver nanocomposites with efficient antibacterial activity. A flexible poly­(dimethylsiloxane) film served as a substrate for deposition of nanostructured silver. A light-activated antibacterial agent, based on the cationic conjugated polyelectrolyte poly­({9,9-bis­[6′-(<i>N,N</i>-trimethylamino)­hexyl]-2,7-fluorenyleneethynylene}-<i>alt</i>-<i>co</i>-1,4-(2,5-dimethoxy)­phenylene)­dibromide (PFEMO) was self-assembled on the negatively charged substrate. By changing the thickness of the poly­(l-lysine)/poly­(acrylic acid) multilayers between the metal substrate and PFEMO, we obtained concomitant enhancement of PFEMO fluorescence, phosphorescence, and reactive oxygen species generation. These enhancements were induced by surface plasmon resonance effects of the Ag nanoparticles, which overlapped the PFEMO absorption band. Owing to the combination of enhanced bactericidal effects and good flexibility, these films have great potential for use as novel biomaterials for preventing bacterial infections

Preparation of Novel Fluorescent Nanocomposites Based on Au Nanoclusters and Their Application in Targeted Detection of Cancer Cells

Fluorescent gold nanoclusters (AuNCs) have drawn considerable research interest owing to their unique emission properties. However, the environment surrounding the NC greatly influences its luminous behavior. In this work, a novel nanocomposite based on AuNCs with bright fluorescence and high biocompatibility was prepared. In this nanocomposite, mesoporous silica nanospheres provided a mesoporous framework, which helped to template the formation of ultrasmall AuNCs and also prevented their aggregation in different solutions. These nanocomposites emitted stable fluorescence even in complex biological environments. After the self-assembly of folic acid-conjugated poly­(l-lysine), the presence of folic acid on the nanocomposites guaranteed a good recognition in folate receptor (FR)-positive cells, improving detection selectivity. Cellular experiments demonstrated that the nanocomposites had good dispersity in the physiological environment and could be internalized by FR-positive cancer cells, resulting in bright fluorescence. We believe that this research provides a simple approach to the fabrication of stable fluorescent AuNC nanocomposites, which show good compatibility with complex biological systems and great potential for applications in biological imaging and cell detection

Facile Preparation of Fluorescent Nanoparticles with Tunable Exciplex Emission and Their Application to Targeted Cellular Imaging

Fluorescent nanoparticles with a tunable emission show a good potential for usage in biological imaging. Exciplex emission usually appears with a large red shift from the normal emission peak. The integration of exciplex emission into nanoparticles offers a rational strategy to designing fluorescent nanoparticles with a tunable emission. In this work, we doped electron acceptors into the electron donor poly­(<i>N</i>-vinylcarbazole) (PVK) to develop novel fluorescent nanoparticles with a conveniently modulated PVK emission. Through careful design of the molecular structures of the electron acceptors, we demonstrated that controlled donor–acceptor spatial stacking and electron transitions could regulate the exciplex emission of the PVK/acceptor nanoparticles. Thus, the structurally controlled exciplex formation allowed for the preparation of multicolored fluorescent nanoparticles. Moreover, further modifications with the cyclic peptide RGD showed little disruption to the structure of the PVK/acceptor nanoparticles and the corresponding exciplex emission. Hence, the nanoparticles showed the ability to be used for targeted cellular imaging. On the basis of the RGD-integrin α_vβ₃ (ligand<i>–</i>receptor) interaction, the nanoparticles were effectively endocytosed by target cancer cells. We anticipate that this research could provide a new strategy for the fabrication of fluorescent nanoparticles with a tunable emission, leading to useful materials for fluorescent imaging

Conjugated Polymer with Aggregation-Directed Intramolecular Förster Resonance Energy Transfer Enabling Efficient Discrimination and Killing of Microbial Pathogens

Rapid and effective differentiation and killing of microbial pathogens are major challenges in the diagnosis and treatment of infectious diseases. Here, we report a novel system based on the conjugated polymer poly­[(9,9-bis­{6′-[<i>N</i>-(triethylene glycol methyl ether)-di­(1<i>H</i>-imidazolium)­methane]­hexyl}-2,7-fluorene)-<i>co</i>-4,7-di-2-thienyl-2,1,3-benzothiadiazole] tetrabromide (PFDBT-BIMEG), which enables efficient microbial pathogen discrimination and killing. The functional side chains of PFDBT-BIMEG enabled both electrostatic and salt bridge interactions with microorganisms. Microorganism binding events caused a change in the aggregation structure of PFDBT-BIMEG, which could be recognized by a change of its fluorescence signal by intramolecular Förster resonance energy transfer (FRET). This sensing strategy allowed rapid and sensitive distinction of microbial pathogens within 15 min. We performed linear discrimination analysis that featured this advance to confirm that the polymer PFDBT-BIMEG could accurately classify microbial pathogens. Owing to the different adhesion mechanism of PFDBT-BIMEG to the surface of the microorganisms, we applied different sterilization strategies for each kind of microbial pathogen. The microbial pathogens could be efficiently killed by reactive oxygen species produced from PFDBT-BIMEG under irradiation, avoiding the use of any other antibacterial agents. This methodology, which combines pathogen discrimination and killing, represents a promising alternative to current diagnostic platforms