Integrating synthetic hydrogel nanoparticles with carbon dots for selective detection of hemoglobin

Synthetic hydrogel nanoparticles (NPs) display high affinity to biomacromolecules target and have significant potential as protein capture agents for medical and biotechnological applications. In this study, we proposed a strategy to modify Carbon dots (CDs) with engineered NPs to address their detection specificity in complex biological sensing matrices. A library of NPs tagged CDs (NPs@CDs) incorporating hydrophobic and carboxylate groups that bound with high affinity to hemoglobin (Hb) was prepared by precipitation polymerization and screened based on the fluorescence quenching effect. NPs and CDs were integrated through noncovalent interaction, which was confirmed by Transmission electron microscopy (TEM), Scanning electron microscopy (SEM), Dynamic Light Scattering (DLS) and Fourier transform infrared spectroscopy analyses. The specificity of NPs@CDs was prominently attributed to the unique affinity between the screened NPs and Hb, compared with the contrast fluorescence quenching study by corresponding CDs to structural analogues and coexistence substances of Hb. Moreover, the Hb-induced fluorescence quenching process was dominated by a synergistic effect of internal filter effect (IFE) and static quenching proved by UV–vis absorption spectrometry and time-resolved fluorescence spectrometry. The screened NPs@CDs showed strong recognition capability to Hb, and the fluorescence quenching rate was about 97 % which was 3.2 times that of CDs. A biosensing platform based on NPs@CDs was constructed, and the fluorescence signal of the nanoprobe decreased linearly as the concentration of Hb over the range of 0.2–80 μM L⁻¹ with a detection limit of 7.5 nM L⁻¹. The synergy between CDs and NPs resulted in high-speed real-time detection capability, high sensitivity, considerable specificity, low interference and good stability of this nanoprobe.