Engineering
biological interfaces represents a powerful means to improve the performance
of biosensors. Here, we developed a DNA-engineered nanozyme interface
for rapid and sensitive detection of dental bacteria. We employed
DNA aptamer as both molecular recognition keys and adhesive substrates
to functionalize the nanozyme. Utilizing different immobilization
strategies and DNA designs, a range of DNA nanoscale biointerfaces
were constructed to modulate enzymatic and biological properties of
the nanozyme systems. These functional biointerfaces improved the
accessibility of bacteria to the nanozyme surface, providing large
signal change range at optimal DNA probe density. The DNA-functionalized
nanozymes demonstrate a rapid, label-free, and highly sensitive direct
colorimetric detection of Streptococcus mutans, with a detection limit of 12 CFU mL–1, as well
as excellent discrimination from other dental bacteria. We demonstrate
the use of this biological nanointerface for identifying dental bacteria
in salivary samples, showing its potential in clinical prevention
and diagnosis of dental diseases.
While the β-lactam antibiotics are known to be susceptible to oxidative degradation by sulfate radical (SO), here we report that peroxymonosulfate (PMS) exhibits specific high reactivity toward β-lactam antibiotics without SO generation for the first time. Apparent second-order reaction constants (k) were determined for the reaction of PMS with three penicillins, five cephalosporins, two carbapenems, and several structurally related chemicals. The pH-dependency of k could be well modeled based on species-specific reactions. On the basis of reaction kinetics, stoichiometry, and structure-activity assessment, the thioether sulfur, on the six- or five-membered rings (penicillins and cephalosporins) and the side chain (carbapenems), was the main reaction site for PMS oxidation. Cephalosporins were more reactive toward PMS than penicillins and carbapenems, and the presence of a phenylglycine side chain significantly enhanced cephalosporins' reactivity toward PMS. Product analysis indicated oxidation of β-lactam antibiotics to two stereoisomeric sulfoxides. A radical scavenging study and electron paramagnetic resonance (EPR) technique confirmed lack of involvement of radical species (e.g., SO). Thus, the PMS-induced oxidation of β-lactam antibiotics was proposed to proceed through a nonradical mechanism involving direct two-electron transfer along with the heterolytic cleavage of the PMS peroxide bond. The new findings of this study are important for elimination of β-lactam antibiotic contamination, because PMS exhibits specific high reactivity and suffers less interference from the water matrix than the radical process.
Graphene-based
nanomaterials (GMs) are served as great promising
agents for the prevention and therapy of infectious diseases. However,
their dental applications remain to be evaluated, especially under
the context of the oral microbial community. Here, we examined the
exposure-response of salivary bacterial community to two types of
GMs, that is, graphene oxide (GO) and GO-silver nanoparticles (AgNPs).
Both GO and GO-AgNPs showed lethal effect against salivary bacteria
in a concentration-dependent manner, and the antibacterial capacity
of GO-AgNPs is superior to GO. Interestingly, the salivary bacterial
community enhanced the tolerance to GMs as compared to homogeneous
bacteria. High-throughput sequencing revealed that both 80 μg/mL
GO and 20 μg/mL GO-AgNPs significantly altered the biodiversity
of salivary bacterial community. Especially, they increased the relative
abundance of Gram-positive bacteria compared to the untreated sample,
notably Streptococcus, suggesting that the bacterial
wall structure plays a critical role in resisting the damage of GMs.
Although GMs could effectively limit the salivary bacterial activity
and cause changes in bacterial community structure, they are not toxic
to mammalian cell lines. We envision this study could provide novel
insights into the application of GMs as “green antibiotics”
in nanomedicine.
The Shamao River is an urban river in Wuhan Economic Development District, which water body is under heavy polluted. A whole year water quality monitoring was carried out in 2019, and the corresponding results showed that the water quality of Shamao river was lower than class V bad water quality. The sediment and overlying water samples were collected. Qualified and analyzed pollution indicators, including COD, ammonia nitrogen (NH3-N) and total phosphorus (TP). The influence of pollutant in water released from sediment was analyzed through laboratory water column simulation experiment. It was found that there was no correlation between concentrations of COD, NH3-N in sediment and corresponding concentrations in overlying water samples. The amount of total phosphorus (TP) in water samples are related to the amount of sediments. Simulated sediment pollution releasing experiments showed that the COD in sediment had weak effect on water quality. The releasing of nitrogen and phosphorus from the sediment increased with time, caused the secondary pollution of the water body.
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