Functional Melanin Nanoparticles-Assisted Laser Desorption Ionization Mass Spectrometry for High-Sensitivity Detection of TBBPA and TBBPS Contaminations in Animal-Derived Foodstuffs.

Tetrabromobisphenol A (TBBPA) and tetrabromobisphenol S (TBBPS) have been widely used as additives in various products; however, their residues damage human health mainly via dietary ingestion. The current detection techniques remain challenging in directly and sensitively identifying TBBPA and TBBPS from food samples. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) has great potential as an alternative tool for the analysis of low-mass environmental pollution. Herein, we successfully screened and optimized COOH-MNP-COOH as a novel MALDI matrix to enhance deprotonation for the analysis of TBBPA and TBBPS from animal-derived food samples in negative-ion mode. Notably, COOH-MNP-COOH was synthesized by a facile self-assembly strategy and characterized by TEM, FT-IR, UV-vis, and zeta potential analysis. Compared with conventional and control matrices, the COOH-MNP-COOH matrix exhibited excellent performance of TBBPA and TBBPS with high chemical stability, favorable reproducibility, remarkable salt and protein tolerance, and high sensitivity owing to abundant active groups, stronger UV-vis absorption at 355 nm, and better hydrophilicity and biocompatibility. TBBPA and TBBPS were detected with the assistance of an internal standard with limits of detection (LODs) of 300 and 200 pg/mL, respectively. Moreover, this method was applied to directly identify the residues of TBBPA and TBBPS in milk products, followed by basa catfish and meat. This research may provide a promising approach for the analysis of environmental pollutants in foodstuffs.

Melanin-gelatin nanoparticles with both EPR effect and renal clearance for PA/MRI dual-modal imaging of tumors.

As cancer nanotherapeutics, the ideal multifunctional nanoparticles not only have the processing ability to accumulate effectively in tumors, but also can be excreted rapidly from the body via renal clearance after effective treatment. Melanin is an endogenous biological material, and gelatin has natural biocompatibility and biodegradability. Such materials are more promising in the development of diagnostic and therapeutic nanoplatform for future clinical translation. In this study, we have developed a kind of size-shrinkable PA/MRI theranostic agent based on gelatin fabricated ultrasmall melanin nanoparticles (MNPs-GNP). The MNPs-GNP nanoparticles, with a size of about 100 nm, presented good dispersibility, broadband light absorbance, negligible cellular cytotoxicity, preferable tumor accumulation by EPR-based passive targeting. The dual-modal imaging results showed that the nanoparticles have excellent photoacoustic (PA) imaging and nuclear magnetic resonance (MRI) imaging after tumor-bearing mice were intravenously injected with MNPs-GNP. Additionally, gelatin is the substrate of matrix metalloproteinase-2 (MMP-2), following with the degradation of gelatin nanoparticles by MMP-2, the large-size MNPs-GNP turns to be small-size melanin, which could mainly be excreted via renal clearance avoiding potential toxicity to body tissues. These preliminary results indicated that MNPs-GNP can overcome the dilemma between EPR and renal clearance, which has clinical application potentiality as a PA/MRI dual-modal candidate agent for cancer theranostics.