Formation of fluorescent platinum nanoclusters using hyper-branched polyethylenimine and their conjugation to antibodies for bio-imaging

We investigated the formation of yellow fluorescent polyethylenimine-protected platinum nanoclusters (Pt NCs@PEI) synthesized by a facile one-pot reduction method. Deep UV (DUV) Raman spectroscopy and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy were employed to estimate chemical bonding between Pt NCs and the surrounding PEI ligands. We found that Pt NCs were produced in the cavities formed by coiled PEI ligands and were mostly stabilized with the amino groups (-NH 2 ). These Pt NCs@PEI with an average diameter of 1.4 ± 0.4 nm demonstrated excellent photo-stability against high salt concentration and long-term light exposure. By conjugating Pt NCs@PEI with the chemokine receptor anti-CXCR4 antibody, we successfully applied Pt NCs@PEI-(anti-CXCR4-Ab) conjugates to bio-imaging of the membrane of live HeLa cells that had their nuclei stained with DAPI. Moreover, Pt NCs@PEI showed lower cell cytotoxicity than Qdots@COOH, indicating that they have better cell viability and great potential for bio-applications. Fluorescent Pt NCs@PEI were formed in the cavities coiled by PEI ligands and bio-imaged HeLa cells via conjugation with antibodies.