A Facile and Efficient Protocol for Phospholipid Enrichment in Synovial Joint Fluid: Monodisperse-Mesoporous SiO2 Microspheres as a New Metal Oxide Affinity Sorbent

Phospholipids (PLs), essential components of cell membranes, play significant roles in maintaining the structural integrity and functionality of joint tissues. One of the main components of synovial joint fluid (SJF) is PLs. Structures such as PLs that are found in low amounts in biological fluids may need to be selectively enriched to be analyzed. Monodisperse-mesoporous SiO2 microspheres were synthesized by a multi-step hydrolysis condensation method for the selective enrichment and separation of PLs in the SJF. The microspheres were characterized by SEM, XPS, XRD, and BET analyses. SiO2 microspheres had a 161.5 m2/g surface area, 1.1 cm3/g pore volume, and 6.7 nm pore diameter, which were efficient in the enrichment of PLs in the SJF. The extracted PLs with sorbents were analyzed using Q-TOF LC/MS in a gradient elution mode with a C18 column [2.1 × 100 mm, 2.5 μM, Xbridge Waters (Milford, MA, USA)]. An untargeted lipidomic approach was performed, and the phospholipid enrichment was successfully carried out using the proposed solid-phase extraction (SPE) protocol. Recovery of the SPE extraction of PLs using sorbents was compared to the classical liquid–liquid extraction (LLE) procedure for lipid extraction. The results showed that monodisperse-mesoporous SiO2 microspheres were eligible for selective enrichment of PLs in SJF samples. These microspheres can be used to identify PLs changes in articular joint cartilage (AJC) in physiological and pathological conditions including osteoarthritis (OA) research.