The latent dangers of waterborne viral transmission have become a major public health concern. In this study, reduced graphene oxide (rGO)-Fe 3 O 4 nanoparticles were decorated with cetyltrimethylammonium bromide (CTAB) to adsorb severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike pseudovirus and three human enteric viruses (HuNoV, HRV, and HAdV). The successful combination of CTAB with rGO-Fe 3 O 4 was confirmed by transmission electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, zeta potential, Brunner-Emmet-Teller, and vibrating sample magnetometer measurements. The adsorption of HuNoV and HAdV followed pseudo-first-order kinetics, while that of HRV conformed to the pseudo-second-order model. CTAB-functionalized rGO-Fe 3 O 4 exhibited exceptionally high adsorption of HuNoV, HRV, HAdV and SARS-CoV-2 spike pseudovirus, with maximum adsorption capacities of 3.55 × 10 7 , 7.01 × 10 7 , 2.21 × 10 7 and 6.92 × 10 6 genome copies mg −1 , respectively. Moreover, the composite could effectively adsorb the four types of virus particles from coastal, tap, and river water. In addition, concentrating the virions using CTAB functionalized rGO-Fe 3 O 4 composites before qPCR analysis significantly improved the detection limit. The results indicate that viruses are captured on the surface of CTAB functionalized rGO-Fe 3 O 4 composites through electrostatic interactions and the intrinsic adsorption ability of rGO. Overall, CTAB-functionalized rGO-Fe 3 O 4 composites are promising materials for the adsorption and detection of human enteric viruses as well as SARS-CoV-2 from complex aqueous environments.
Clustered regularly interspaced short palindromic repeats (CRISPR)-based diagnostics have been considered as the next generation molecular diagnosis tool. Single-readout mode has been extensively employed in massive CRISPR/Cas12a-based biosensors. In this work, we propose a one-tube dual-readout biosensor for ultrasensitive nucleic acids and non-nucleic acids detection by harnessing CRISPR-ALP tandem assay for the first time (termed CRISAT). In the presence of target, the Cas12a is activated to randomly cut the single-stranded hyDNA sequence of MB@hyDNA-cALP, thus releasing abundant alkaline phosphatase (ALP) in the supernatant solution. By using 4-aminophenol phosphate as the substrate of ALP, p-aminophenol is produced and then reacts with N-[3-(trimethoxysilyl)propyl]ethylenediamine or diethylenetriamine to generate silicon-containing polymer carbon dots (Si PCDs) or polymer carbon dots (PCDs) in situ, which can be observed by naked eye or detected by a fluorescent device in the same solution. Using this strategy, a fluoroscence and colorimetry dual-readout nanoplatform for CRISPR-based biosensor can be rationally developed. We ascertain the applicability of CRISAT through detecting SARS-CoV-2 pseudovirus, achieving superior sensitivity and specificity. With simple modification of crRNAs, the CRISAT platform can be also employed to detect monkeypox virus (MPXV) and non-nucleic acids of adenosine triphosphate (ATP). This work provides a great potential for nucleic acids and non-nucleic acids detection.
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