Design of green magneto-fluorescent γ-Fe2O3-methyldopa conjugate nanocrystal as a targeted probe for monitoring of esterase activity

Multifunctional Near-Infrared Fluorescent Probes with Different Ring-Structure Trigger Groups for Cell Health Monitoring and In Vivo Esterase Activity Detection

A series of multifunctional ratiometric near-infrared fluorescent probes (CYOH-3, CYOH-4, CYOH-5, and CYOH-6) for esterase detection are designed by gradually changing the deflection of the plane twist in the molecule. These probes are composed of different ring-structure trigger groups (from three-membered ring to six-membered ring) and the same luminescent group CYOH. These probes show maximum absorption at ∼585 nm and a fluorescence emission peak at ∼655 ± 5 nm. In the presence of esterase, the probes were hydrolyzed to expose the fluorophore CYOH (λ_abs = 690 nm, λ_em = 710 ± 5 nm), thus exhibiting ratiometric near-infrared fluorescence. The probe CYOH-6 has lower plane deflection angle and better ratiometric (R = I_710±5nm/I_657±4nm) fluorescence properties than probes CYOH-3, CYOH-4, and CYOH-5. CYOH-6 (six-membered ring) has been successfully used to target esterase in mitochondria and distinguish between dead cells (esterase inactivation) and live cells. In addition, CYOH-6 has been well used for monitoring of esterase activity in zebrafish and mice, which proves that these probes have good prospects for clinical biomedical applications.

A fluorescent sensor based on methyldopa drug modified γ-Fe2O3 nanoparticles for ultrasensitive detection of calf thymus DNA

We reported the study of calf thymus DNA (ct-DNA) adsorption by the polymer of methyldopa (2-amino-3-(3,4-dihydroxyphenyl)-2-methyl acid, propanoic) (PMDP), magnetofluorescent PMDP-γ-Fe2O3 nanocrystal. The method is based on the extraordinarily high quenching efficiency of ct-DNA and the specific interaction between ct-DNA and PMDP-γ-Fe2O3 via guanine base and metal coordination, probably. It was found that the designed magnetic nanoparticles can adsorb ct-DNA in nM levels in the presence of NaCl and KCl. In acetate and phosphate buffers DNA were adsorbed completely. Also, we found that pH plays an important role in DNA adsorption onto PMDP-γ-Fe2O3 nanocrystal. PMDP-γ-Fe2O3 nanocrystal is highly hydrophilic and DNA desorption wasn't observed. We believe this study will further stimulate the application of PMDP-γ-Fe2O3 nanocrystal in bioanalytical chemistry and nanotechnology. PMDP-γ-Fe2O3 nanocrystal possesses the ability to interact with ct-DNA via a partial intercalative binding mechanism, as demonstrated by fluorescence displacement experiments and a significant red shift (ca, 10nm) in UV-vis spectra.