Nonconventional Luminescent Biomacromolecules with Efficient Dilute-Solution Emission for Lipid Droplet Imaging

Organic luminescent materials are essential for OLEDs and bioimaging, yet traditional π-conjugated molecules face synthetic and environmental challenges. Nonconventional luminescent materials (NLMs) offer better biocompatibility but typically exhibit weak clustering-triggered emission (CTE) in dilute solutions, limiting their biomedical utility. To address this, we synthesized four aspartic acid-based NLMs (S1-S4) featuring hydrophobic segments. These polymers self-assemble into nanoclusters in dilute solutions, restricting molecular motion to enable potent CTE. Remarkably, S1-S4 achieved high photoluminescence quantum yields (up to 10.07% at 0.5 mg/mL) and demonstrated low cytotoxicity. These NLMs function as effective lipid droplet (LD) imaging agents; specifically, S4 exhibited a 94% colocalization rate with the commercial probe Nile Red. By achieving performance comparable to traditional fluorescent probes in dilute states, these NLMs provide a robust, sustainable tool for specific subcellular imaging and advance the practical application of nonconjugated emitters.