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High-performance analysis of heavy metal ions is great importance in both environment and food safety. In this work, a facile and reliable colorimetric sensor was presented for simultaneous detection of Cu2+ and Cr3+ based on indicator-displacement assay (IDA). As a typical silicate nanomaterials, ZnSiO3 hollow nanosphere (ZSHS) exhibited an outstanding ion exchange capacity. Zincon was incorporated with the ZSHS to form a zincon/ZSHS hybrid ionophore with a blue color. Upon the addition of Cr3+, IDA reaction and selective ion exchange occurred with the color change of zincon/ZSHS ionophore from blue to yellow. With such a design, colorimetric measurement of Cr3+ was realized. The linear concentration for Cr3+ detection ranged from 0.5 μM to 75 μM with the LOD of 83.2 nM. Furthermore, we also screened different kinds of complexing agents that may respond with zincon/ZSHS ionophore and various metal ions. It was found that tartaric acid (TA) showed the chelation capability of Zn2+-TA is stronger than that of Zn2+-zincon. Thus zincon/ZSHS/TA presented a yellow color due to the chelation reaction of Zn2+-TA, releasing the zincon as a free state. After addition of Cu2+, a stronger chelation reaction of Cu2+-zincon occurred. This process involved in the color change from yellow to blue and realized colorimetric measurement of Cu2+. The detection limit of Cu2+ was calculated to be 43.7 nM with linear range from 0.1 to 20 μM. In addition, the zincon/ZSHS nanoprobe was successfully applied for simultaneous measurement of Cu2+ and Cr3+ in sorghum and river water, indicating that the zincon/ZSHS nanoprobe provided a promising sensing platform in environment and food safety.

Capripoxvirus (CaPV) is one of the common skin diseases infecting cattle and sheep which can cause serious economic losses. Establishing ultra-sensitive, rapid, and point-of-care detection of CaPV is particularly important for hindering its spread. Here, we use the principle that CRISPR/Cpf1 can specifically recognize the target DNA and activate its trans-cleavage activity to identify the CaPV product amplified by loop-mediated amplification (LAMP). Under the designed specific primers, a set of LAMP which can amplify CaPV specifically was established and optimized firstly. Then, the CRISPR/Cpf1 was introduced to identify LAMP products. LAMP can be completed at a constant temperature, thus avoiding the use of temperature-variable instruments, making it possible to detect viruses outside the laboratory. To further satisfy the point-of-care detection of CaPV, we introduced a portable fluorometer and CRISPR-based lateral flow test. Due to the introduction of CRISPR/Cpf1, the sensitivity of the method is greatly increased, which is of great significance for the early detection of viruses. Through CRISPR/Cpf1-mediated fluorescence detection, we can detect CaPV as low as 1.47 × 10−3 TCID50 in 50 min, 1000 times more sensitive than quantitative real-time PCR. Through CRISPR-based lateral flow test, we can visually detect CaPV as low as 1.47 × 10−2 TCID50. Besides, this strategy can be used for the primary samples obtained from the cell culture of CaPV after simple ultrasonic disruption, which eliminates the complicated nucleic acid extraction steps required by traditional methods.