Layer-by-layer assembly strategy for fabrication of polydopamine-polyethyleneimine hybrid modified fibers and their application to solid-phase microextraction of bioactive molecules from medicinal plant samples followed by surface plasmon resonance biosensor validation.

A solid-phase microextraction method is introduced to overcome limitations of classical phytochemical pattern of identifying bioactive compounds, including tedious and time-consuming separation and purification step and consumption of large amounts of organic solvents, which was non-environmentally- friendly. In this proposed method for solid-phase microextraction, polyvinylidene fluoride fibers@polydopamine@polyethyleneimine@receptor as a solid part of the extractors were pushed into sample solution of medicinal plants, and the procedure was followed by stirring and easily dissociation of receptor binding ligands in organic solvent through pulling out of the functionalized fibers. Xanthine oxidase was chosen as the model receptor, while isoacteoside was selected as the model inhibitor. Several effecting parameters were optimized by experimental design, including temperature, ion strength and pH. Nine bioactive components were obtained from extract of Plantago depressa by using the established solid-phase micro-extraction method. The limit of detection and limit of quantification of the nine components ranged from 0.0008 to 0.03 mg mL-1 and from 0.001 to 0.016 mg mL-1, respectively. The RSD values of intra-day and inter-day precisions ranged from 0.24% to 2.19% and 0.62%-2.84%, respectively. The average recoveries of the nine components were from 95.06 to 104.03% with relative standard deviation (RSD) values from 1.02 to 2.90% for Plantago depressa. The RSD values of stability of the nine components ranged from 1.36% to 2.74%, which satisfied the requirements of an analytical method. In addition, surface plasmon resonance biosensor was utilized to corroborate the binding affinity between these compounds and receptor. The avidity values of these ligands corresponded well with their IC50 values. The results confirmed that polydopamine and polyethyleneimine hybrid modified polyvinylidene fluoride fibers based solid-phase microextraction method was successfully utilized for locating bioactive compounds of medicinal plants.