Temperature-Responsive Fluorescence Polymer Probes with Accurate Thermally Controlled Cellular Uptakes

Area of Science:

• Polymer Chemistry
• Biotechnology
• Materials Science

Background:

• Thermoresponsive polymers, such as poly(N-isopropylacrylamide) (PNIPAAm), exhibit a lower critical solution temperature (LCST) where they transition from hydrophilic to hydrophobic.
• Fluorescent labeling of polymers allows for real-time tracking and visualization of their behavior in biological systems.

Purpose of the Study:

• To develop novel fluorescent polymer probes with tunable temperature-responsive properties.
• To investigate the cellular uptake mechanisms of these probes in relation to their LCST.
• To explore the potential of these probes in biological applications, including cell discrimination and intracellular drug delivery.

Main Methods:

• Radical polymerization was employed to synthesize PNIPAAm-based copolymers.
• 3-Mercaptopropionic acid was used as a chain-transfer agent.
• Terminal carboxyl groups were activated and conjugated with 5-aminofluorescein (FL) to create fluorescent probes.

Main Results:

• The synthesized fluorescent polymer probes demonstrated distinct LCSTs dependent on copolymer composition.
• Cellular uptake was significantly suppressed below the LCST and markedly increased above it.
• A specific copolymer, P(NIPAAm-co-DMAPAAm2%)-FL, exhibited controlled cellular uptake within a 1°C range near body temperature (LCST: 37.4 °C).

Conclusions:

• Temperature precisely controls the cellular uptake of these thermoresponsive fluorescent polymer probes.
• These probes show potential for differentiating between normal and pathological cells.
• The probes are promising for intracellular drug delivery systems, particularly when combined with local hyperthermia.