Assembling inner filter effect reduced SnS2 quantum dots-based hollow polymeric spherical nanoshells for ratio electrochemiluminescence bioassay

SnS2 quantum dots (QDs) as excellent electrochemiluminescence (ECL) luminators have exhibited a good application prospect in ECL field, but the difficulty of being effectively immobilized on the electrode and inner filter effect caused by their compact packaging make the construction of SnS2 QDs-based ECL system challenging. This work developed a hollow polymeric spherical nanoshells (HPSNs) for loading SnS2 QDs. SiO2 nanoparticles (NPs) served as the carrier for the multilayer assembly of polyethyleneimine (PEI)-SnS2 QDs and polyacrylic acid (PAA). Then, SiO2 NPs were etched to produce SnS2 QDs-based HPSNs (SnS2-HPSNs), which can not only achieve the high loading of SnS2 QDs but effectively reduce their inner filter effect, revealing a significantly improved cathodic ECL performance. SnS2-HPSNs coupled with anodic luminators Ir nanorods (NRs) to construct a ratiometric ECL biosensor for detecting cardiac troponin I (cTnI) with tripropylamine (TPrA) and persulfate (S2O82-) as anodic and cathodic co-reactants, respectively. Norepinephrine (NE) and gold nanoparticles (AuNPs) were innovatively developed as dual-quencher for Ir NRs. The secondary antibody complex containing SnS2-HPSNs and NE-AuNPs was specially constructed and its assembly on the biosensor modified with Ir NRs can conveniently realize the different changes of the two signals, thus achieving the sensitive detection of cTnI with a detection limit of 0.32 pg/mL. The HPSNs provided an effective strategy for high loading of QDs while reducing their inner filter effect. The integration of two luminators (SnS2-HPSNs and Ir NRs) and dual-quencher created a promising ECL ratio platform for the accurate detection of various biomarkers.