Liposome encapsulated electron donor strategy for signal-on CYFRA 21-1 photoelectrochemical analysis

A novel electron donor controlled-release system is proposed based on liposome encapsulated L-cysteine for the sensitive determination of cytokeratin 19 fragment 21-1 (CYFRA 21-1). On the one hand, a defective TiO₂ modified with methylene blue was employed as a photoactive platform which exhibited a high photoelectrochemical (PEC) response owing to the introduction of oxygen vacancies and the high  photosensitivity of the dye. On the other hand, L-cysteine as the sacrificial electron donor was encapsulated in the vesicles of liposomes, and this composite was used as the signal amplification factor, which is labeled on the secondary antibody of CYFRA 21-1 to further improve the photocurrent sensitivity. The excellent electron transfer path in photoactive materials coupled with the skilful electron donor controlled-release system, contributed to the sensitive  PEC analysis of CYFRA 21-1 underoptimum conditions. The PEC immunoassay showed a linear current response in the range 0.0001-100 ng/mL with a detection limitof 37 fg/mL. Enhanced stability and satisfactory reproducibility were also achieved. The proposed concept  provides a novel signal-on strategy for the sensitive detection of other cancer markers in the electrochemical sensing field.

Ag3PO4 decorated black urchin-like defective TiO2 for rapid and long-term bacteria-killing under visible light

Both phototherapy via photocatalysts and physical puncture by artificial nanostructures are promising substitutes for antibiotics when treating drug-resistant bacterial infectious diseases. However, the photodynamic therapeutic efficacy of photocatalysts is seriously restricted by the rapid recombination of photogenerated electron–hole pairs. Meanwhile, the nanostructures of physical puncture are limited to two-dimensional (2D) platforms, and they cannot be fully used yet. Thus, this research developed a synergistic system of Ag₃PO₄ nanoparticles (NPs), decorated with black urchin-like defective TiO₂ (BU–TiO_2-X/Ag₃PO₄). These NPs had a decreased bandgap compared to BU-TiO_2-X, and BU-TiO_2-X/Ag₃PO₄ (3:1) exhibited the lowest bandgap and the highest separation efficiency for photogenerated electron–hole pairs. After combination with BU-TiO_2-X, the photostability of Ag₃PO₄ improved because the oxygen vacancy of BU-TiO_2-X retards the reduction of Ag⁺ in Ag₃PO₄ into Ag⁰, thus reducing its toxicity. In addition, the nanospikes on the surface of BU-TiO_2-X can, from all directions, physically puncture bacterial cells, thus assisting the hybrid's photodynamic therapeutic effects, alongside the small amount of Ag⁺ released from Ag₃PO₄. This achieves synergy, endowing the hybrid with high antibacterial efficacy of 99.76 ± 0.15% and 99.85 ± 0.09% against Escherichia coli and Staphylococcus aureus, respectively, after light irradiation for 20 min followed by darkness for 12 h. It is anticipated that these findings may bring new insight for developing synergistic treatment strategies against bacterial infectious diseases or pathogenic bacterial polluted environments.

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BU-TiO_2-X/Ag₃PO₄ (3:1) hybrid improved the photostability of Ag₃PO₄.

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BU-TiO_2-X/Ag₃PO₄ (3:1) hybrid exhibited outstanding photodynamic therapeutic effects.

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The nanospikes from all directions on the BU-TiO_2-X physically punctured bacterial cells.

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The physical puncture combined with the Ag⁺ released by Ag₃PO₄ had long-term bacteriostatic efficacy.