# Recent Advances in Optical Detection of Aminoglycosodies
## 6 Multiplex Detection of Antibiotics
### Based on Multiplex Labels  
Various nanomaterials such as graphene oxide and MoS\({}_{2}\) nanosheets were reported to have an efficient FL quenching effect. These nanomaterials have been employed as quenchers to construct FRET-based biosensing platforms for the detection of antibiotics. For example, [PERSON]'s group employed metal polydopamine frameworks (MPDAs) as an efficient quencher to construct a FRET-based sensing system for the simultaneous detection of kanamycin and oxytetracycline. The kanamycin-aptamer and oxytetracycline-aptamer were labeled as FAM and carboxytetramethylhydomamine (TAMRA), respectively. The MPDAs showed a strong binding ability to single-strand DNA or free aptamer, while they had a weak interaction with double-stranded DNA and the complex of the aptamer and target molecule. Therefore, quenched FL signals were observed in the absence of the target antibiotics, while the binding of target antibiotics to the aptamer resulted in turn-on FL signals. FL emissions at 525 and 583 nm were monitored for the simultaneous determination of kanamycin and oxytetracycline. In the case of kanamycin, the LOD was 0.3 nM [89]. Two-dimensional MOF Cu-tetrakis(4-carboxyphenyl)porphyrin (TCPP) showed a similar property to MPDAs and has been employed as an efficient quencher to construct a multiplex sensing platform for the simultaneous detection of three kinds of antibiotics. Fluorophore-labeled probes adsorbed on the surface of Cu-TCPP caused the FL quenching. Differing from the former work, Y-shaped hybridized DNA strands were employed to assemble aptamers on the surface of a gold bar, and another gold bar that has immobilized complementary probes was employed to initiate target recycling and the release of the aptamer. The released aptamer hybridized with the adsorbed probes, leading to the full recovery of FL signals. The developed aptasensor was sufficiently sensitive to detect antibiotic residues as low as 1.5, 2.4, and 1 pM for chloramphenicol, oxytetracycline, and kanamycin, respectively [90]. [PERSON] et al. employed GO as an FL quencher and developed a signal-on FL method for the simultaneous detection of sulfadinetnokine, kanamycin, and ampicillin by using Cy3, Cy5, and FAM-labeled aptamers. With the aid of the DNAse I-assisted cyclic enzymatic signal amplification method, the aptasensor detected antibiotics in solution with limits of detection of 6.4, 4.5, and 6.7 nM for sulfadinetnokine, kanamycin, and ampicillin, respectively [91].  
Semiconductor quantum dots have unique emission properties such as size-dependent FL emission, a wide excitation spectrum, and a narrow emission spectrum. Therefore, semiconductor QDs have been employed for multiplex sensing platforms. [PERSON] and [PERSON]'s group employed green-emitting QDs and red-emitting QDs as support materials and prepared two kinds of MIP-coated QDs using aminopropyltriethoxysilane (APTES) a functional monomer, tetraethoxysilane (TEOS) as a cross-linker,and antibiotics as the monomers. The two kinds of MIP-coated QDs were used to establish a NAND molecular logic gate for the simultaneous detection of streptomycin sulfate and kanamycin sulfate. The green-emitting QDs responded with streptomycin sulfate, while the red-emitting QDs had a response to kanamycin sulfate. The LOD was 0.22 mM and 0.24 mM for streptomycin sulfate and kanamycin sulfate, respectively [92].