Hollow core-shell nanostructured MnO2/Fe2O3 embedded within amorphous carbon nanocomposite as sensitive bioplatform for detecting protein tyrosine kinase-7

We designed and synthesized a novel bimetallic MnFe oxides embedded within amorphous carbon layer (represented by MnO2/Fe2O3@aC) and exploited it as the scaffold to construct a label-free electrochemical aptasensor for selectively detecting the trace cancer marker, i.e., protein tyrosine kinase-7 (PTK7). The used MnO2/Fe2O3@aC composite was derived from the composite of the bimetallic MnFe Prussian blue analog (MnFe PBA) and polypyrrole (PPy) by calcination at 400 degrees C. X-ray photoelectron spectroscopy characterizations revealed that coexisting metal ions (Mn2+, Mn3+, and Fe2+) and metallic Fe (Fe-0) were contained in the pristine hollow MnFe PBA and MnFePBA@PPy nanoboxes. After calcination, metallic ions (Mn2+ and Fe2+) were oxidized to their corresponding metal oxides (MnO2 and Fe2O3). Meanwhile, the covered PPy layer over MnFe PBA was transferred into carbon nitride. The coexistence of MnO2, Fe2O3, amorphous carbon, and various functional N-related groups endows the as-prepared MnO2/Fe2O3@aC composite strong binding interaction with aptamer strands and good electrochemical activity. Most importantly, the synergistic effect between bimetallic oxide particles and amorphous carbon can improve the electrochemical activity of the substrate and also can enhance the G-quadruplex stability in aqueous solution formed between the aptamer strands and PTK7 via biorecognition force. This force further improves the sensing performance toward PTK7. The fabricated MnO2/Fe2O3@aC-based aptasensor exhibited a low detection limit of 44 fg mL(-1) within a broad PTK7 concentration from 0.1 pg mL(-1) to 10 ng mL(-1) and 20 cell.mL(-1) toward human esophageal cancer EC9706 cells ranged from 1x10(2) to 1x10(6) cell.mL(-1), along with high selectivity, good stability and reproducibility, and acceptability in the human serum. The elaborated aptasensor provides a novel strategy for building PBA-based and PBA derivative-based sensors for the sensitive detection of various cancer markers.