Conjugated Oligomer-Based Fluorescent Nanoparticles as Functional Nanocarriers for Nucleic Acids Delivery

Oligonucleotides such as siRNA and plasmid DNA (pDNA) have great potential for gene therapies. Multifunctional, environment-resistant carriers with imaging capabilities are required to track the assembly and disassembly of oligonucleotides, monitor the delivery processes, and develop new delivery systems. Conjugated polymers and oligomers can potentially be used as novel materials for functional nanocarriers with both delivery and imaging abilities. In this work, a novel π-conjugated oligomer 4,7-(9,9′-bis­(6-adenine hexyl)­fluorenyl)-2,1,3-benzothiadiazole (OFBT-A) modified with nucleotide adenine (A) groups in its side chains is synthesized and characterized. Fluorescent nanoparticles based on the π-conjugated oligomers OFBT-A are developed as novel functional nanocarriers for oligonucleotides. Single-stranded DNA (ssDNA) TR-T5 labeled with Texas Red (TR) fluorescent dye is selected as a model payload oligonucleotide. The capture abilities and stability of OFBT-A are investigated by monitoring the fluorescence resonance energy transfer (FRET) efficiency between the OFBT-A nanoparticles and TR labels in solution. The OFBT-A/TR-T5 composites are stable in solution at high ionic strengths (0–500 mM) and have a wide working pH range, from 3.0 to 9.5. The in vitro profile demonstrates that the release of the TR-DNA is induced by the ssDNA A43, which has a high charge density. The release process is monitored by measuring the changes in FRET efficiency and fluorescence color for the OFBT-A/TR-T5 composites. Using this carrier, the uptake of TR-DNA by A549 lung cancer cells is observed. Both the OFBT-A nanoparticles and the OFBT-A/TR-T5 composites show high cytocompatibility. We anticipate that these novel functional nanocarriers will provide a safe strategy for monitoring the gene delivery process

Citrate-Induced Aggregation of Conjugated Polyelectrolytes for Al³⁺-Ion-Sensing Assays

This work shows the sodium citrate induced efficient interpolymer π-stacking aggregation of the planar cationic conjugated polyelectrolyte poly­[{9,9-bis­[6′-(<i>N</i>,<i>N</i>-trimethylamino)­hexyl]-2,7-fluorenyleneethynylene}-<i>alt</i>-<i>co</i>-(1,4-phenylene)] dibromide (PFE) in aqueous solution, which results in the self-quenching of fluorescence. Using the citrate-induced aggregation properties of PFE and the strong chelation ability of citrate with aluminum ions (Al³⁺), a sensitive and selective Al³⁺-ion detection assay in aqueous solution was developed through monitoring of the fluorescence recovery of PFE. The fluorescence intensity recovery of PFE depends on the concentration of Al³⁺ ions, and linear fluorescence recovery was observed in the range of 0.5–9 μM. The limit of detection of this assay is 0.37 μM. Its simplicity and rapidity mean this assay shows promise for the real-time detection of Al³⁺