Silver nanoclusters have been extensively used to construct fluorescent sensors for the detection of metal ions. Many synthetic strategies have been employed for development of these remarkable fluorescent materials by using different organic or biological templates such as proteins, peptides, polyelectrolyte, and DNAs. In the case of polyelectrolyte, polyethyleneimine (PEI) is a positively charged hyper-branched polyamine regarded as an ideal template to modify and stabilize nanoparticles based on several advantages: firstly, PEI contains primary, secondary and tertiary amine groups, which could efficiently chelate with metallic nucleus and stabilize these particles against flocculation by the strong columbic interaction due to the inherent high cationic density of the polymer.¹ Considering the benefits of PEI-AgNCs, we have synthesized PEI-AgNCs using formaldehyde as the reducing agent and further bio-conjugated with the active form of vitamin B₆ cofactor pyridoxal 5 -phosphate (PLP) to tune the sensing properties. Thus, the bio-conjugation of PLP with PEI-AgNCs (PLP_PEI-AgNCs) results in the formation of Schiff base that perceive significance complexation-induced turn-on fluorescent response in the presence of Zn²⁺ and Cd²⁺ with the detection limit down to 50.5 x 10^-8 M for Zn²⁺ and 59.0 x 10^-8 M for Cd²⁺, respectively. Also, low cost covalently anchored cellulose strips were prepared using the nano-assembly PLP_PEI-AgNCs for the easy on-site detection of Zn²⁺ and Cd²⁺. In addition, the nanoprobe was employed in live cell imaging for the detection of intracellular Zn²⁺ in live HeLa cells.²

References

1. 1. Manoth, M.; Manzoor, K.; Patra, M.; Pandey, P.; Vadera, S.; Kumar, N., Dendrigraft polymer-based synthesis of silver nanoparticles showing bright blue fluorescence. Materials Research Bulletin 2009, 44 (3), 714-717.
2. Bothra, S.; Paira, P.; Kumar Sk, A.; Kumar, R.; Sahoo, S. K., Vitamin B6 Cofactor-Conjugated Polyethyleneimine-Passivated Silver Nanoclusters for Fluorescent Sensing of Zn²⁺and Cd²⁺ Using Chemically Modified Cellulose Strips. ChemistrySelect 2017, 2 (21), 6023-6029.