Electrochemiluminescence biosensing of spatially conjugated ester groups triggered by smart bridging between nano-silica and poly (ethylene maleate)

Organic luminescent materials with unique photoelectric properties are as a kind of emerging luminophore at the forefront of research in biological detection on account of their facilely varied functional groups. However, most organic luminophores are aromatic compounds with certain biological toxicity to limit their application. Herein, we envisioned a green organic electrochemiluminescencence (ECL) luminophore without aromatic ring structure but electron-rich functional groups via in-situ growth of poly (ethylene maleate) (PEM) on nano-silica (NS). The experimental and theoretical modelling results indicate that ECL signal of PEM-NSs was enhanced by the spatial conjugation of ester groups (ester clusters), due to the contribution of smart bridging of NS with different sizes. The smaller the NS size is, the more growth of ester groups on the NS surface is, and the closer individual ester groups are linked via “through-space interaction” to form stable ester clusters with smaller energy gaps, thus achieving high ECL performance. For further application, PEM-NS-1 was selected as meaningful ECL luminophore, and integrated with exonuclease III-assisted catalytic hairpin assembly amplification strategy, an efficient platform for biomarkers (microRNA-21) detection was constructed with the detection limit of 2.73 fM (S/N = 3). This work sets the stage for strengthening ECL of electron-rich functional groups, and provides a way of thinking for low-toxicity organic luminophores.