Facile synthesis of yolk–shell magnetic mesoporous carbon microspheres for efficient enrichment of low abundance peptides

Abstract

Magnetic mesoporous carbon microspheres with a yolk-shell structure (YSMMCS) have been prepared via a new in situ carbon source strategy. The material was fabricated by two shells coated onto the Fe3O4 particles; the inner dense and thick silica shell could protect the magnetic core from harsh acidic solvents as well as induce the void between the core and the outer shell for the yolk-shell structure, while the outer organosilica shell was used as the template and carbon source for in situ preparation of a carbon shell with mesoporous structure. A C18-alkyl chain was incorporated in situ as the carbon precursor efficiently, avoiding the conventional infiltration step, which was very difficult to manipulate and time-consuming with the possibility of losing the carbon precursor. The resulting yolk-shell magnetic mesoporous carbon microspheres exhibited a high surface area (273.15 m(2) g(-1)), a large pore volume (0.31 cm(3) g(-1)), and a strong magnetic response (a saturation magnetization value of 34.57 emu g(-1)). As a result of the void between the core and the outer shell and the π-π stacking effect, adsorption capacity reached 191.64 mg g(-1) by using Rhodamine B as a standard analyte, indicating the great potential application of the material as drug carriers. Owing to the inherent hydrophobicity and high surface area, the composite material showed better performance in the enrichment of peptides than a magnetic mesoporous silica material (Fe2O3@nSiO2@mSiO2). According to the LC-MS/MS results, about 51 and 29 nonredundant peptides were identified from tryptic digests of 5 nM BSA. Additionally, taking advantage of the mesoporous structure and strong magnetic response, the material was utilized to selectively extract low abundance endogenous peptides from human serum in the presence of high abundance proteins. Based on the LC-MS/MS results, 962 endogenous peptides were obtained by 2.5 mg YSMMCS relative to 539 endogenous peptides by 5 mg Fe2O3@nSiO2@mSiO2, confirming the outstanding performance of YSMMCS in peptidome analysis.