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The DNA in the shell of Crassostrea gigas could have important roles in the shell biomineralization. However, limited by the low efficiency of existing extraction methods, studies investigating the DNA in shells are lacking. In this study, the shell DNA of C. gigas was extracted using the organic solvent extraction (OSE) and guanidine lysis buffer (GLB) methods; the efficiency and quality of these two methods were compared. The sequences of a mitochondrial gene (cytochrome c oxidase subunit I, COI) and a nuclear gene (28S rRNA) of C. gigas were analyzed to verify the origin of the extracted shell DNA. Finally, the DNA contents of the ventral edge, middle part, and dorsal edge of C. gigas shells were compared. The results showed that OSE had a higher DNA extraction efficiency than GLB; the oyster shell DNA was homologous to the oyster genome; the DNA content was higher in the ventral edge than in the middle part or in the dorsal edge of the C. gigas shell. This study not only reports an improved extraction method for the mollusk shell DNA, but also revealed that the DNA in the oyster shell originates from the oyster body and that the DNA content in different parts of the C. gigas shell showed obvious variance. These results provide supporting evidence for the hypothesis that oyster cells participate in shell formation, and also afford a nondestructive method for oyster genetic identification, which can promote the application of molecular biology technology in oyster breeding. In addition, a shell growth pattern of ‘Under Old & Exceeding Old’ was also proposed.

Electrochemical sensors can be used to detect neurotransmitters. A miniature potentiometric all-solid-state coated wire dopamine sensor was investigated in this work. Conducting polymer poly (3,4- ethylenedioxythiophene) doped with poly (styrenesulfonate) as the solid contact was electropolymerized on one end of a gold wire (diameter 0.25 mm). The conducting polymer was covered with a dopamine-selective membrane containing 12-crown-4-tetraphenylborate as a neutral carrier, 2-nitrophenyloctyl ether as a plasticizer and poly (vinyl chloride) as the membrane matrix. The dopamine sensor covered a wide linear range from 10–5 M to 10–1 M with a slope of 53.85 ± 0.93 mV/decade, while the detection limit was 5.80 ± 0.31 µM. The other characteristics of the dopamine sensor were also evaluated. The experimental results showed that the sensor operated properly within the pH range of 5.5–7.5 and displayed good selectivity, fast dynamic response, high reproducibility and long stability. In addition, the dopamine sensor was successfully applied for the detection of dopamine in artificial cerebrospinal fluid by using the standard addition method, indicating that this sensor is promising for applications in dopamine determination in neuroscientific research.