Ultrasensitive Biochemical Sensing Platform Enabled by Directly Grown Graphene on Insulator.

To fabricate label-free and rapid-resulting semiconducting biosensor devices incorporating graphene, it is pertinent to directly grow uniform graphene films on technologically important dielectric and semiconducting substrates. However, it has long been intuitively believed that the nonideal disordered structures formed during direct growth, and the resulted inferior electrical properties will inevitably lead to deteriorated sensing performance. Here, graphene biosensor chips are constructed based on direct plasma-enhanced chemical vapor deposition (PECVD) grown graphene on a 4-inch silicon wafer with excellent film uniformity and high yield. To surprise, optimal operations of graphene biosensors permit ultrasensitive detection of SARS-CoV-2 virus nucleocapsid protein with dilutions down to sub-femtomolar concentrations. Such impressive limit of detection (LOD) is comparable to or even outperforms that of the state-of-the-art biosensor devices based on high-quality graphene. Further noise spectral characterizations and analysis confirms that the LOD is limited by molecular diffusion and/or known interference signals such as drift and instability of the sensors, rather than the electrical merits of the graphene devices along. Hence, result sheds light on processing directly grown PECVD graphene into high-performance sensor devices with important economic benefits and social significance.

Degree of disorder-regulated ion transport through amorphous monolayer carbon.

Nanopore technology, re-fueled by two-dimensional (2D) materials such as graphene and MoS2, controls mass transport by allowing certain species while denying others at the nanoscale and has a wide application range in DNA sequencing, nano-power generation, and others. With their low transmembrane transport resistance and high permeability stemming from their ultrathin nature, crystalline 2D materials do not possess nanoscale holes naturally, thus requiring additional fabrication to create nanopores. Herein, we demonstrate that nanopores exist in amorphous monolayer carbon (AMC) grown at low temperatures. The size and density of nanopores can be tuned by the growth temperature, which was experimentally verified by atomic images and further corroborated by kinetic Monte Carlo simulation. Furthermore, AMC films with varied degrees of disorder (DOD) exhibit tunable transmembrane ionic conductance over two orders of magnitude when serving as nanopore membranes. This work demonstrates the DOD-tuned property in amorphous monolayer carbon and provides a new candidate for modern membrane science and technology.

Dielectric-Modulated Biosensing with Ultrahigh-Frequency-Operated Graphene Field-Effect Transistors.

Owing to their excellent electrical properties and chemical stability, graphene field-effect transistors (Gr-FET) are extensively studied for biosensing applications. However, hinging on surface interactions of charged biomolecules, the sensitivity of Gr-FET is hampered by ionic screening under physiological conditions with high salt concentrations up to frequencies as high as MHz. Here, an electrolyte-gated Gr-FET in reflectometry mode at ultrahigh frequencies (UHF, around 2 GHz), where the ionic screening is fully cancelled and the dielectric sensitivity of the device allows the Gr-FET to directly function in high-salt solutions, is configured. Strikingly, by simultaneous characterization using electrolyte gating and UHF reflectometry, the developed graphene biosensors offer unprecedented capability for real-time monitoring of dielectric-specified biomolecular/cell interactions/activities, with superior limit of detection compared to that of previously reported nanoscale high-frequency sensors. These achievements highlight the unique potential of ultrahigh-frequency operation for unblocking the true potential of graphene biosensors for point-of-care diagnostic.

[Evaluation of Heavy Metal Content, Sources, and Potential Ecological Risks in Soils of Southern Hilly Areas].

In order to explore the characteristics of soil heavy metal pollution and ecological risk status in southern hilly areas, a hilly area of a southern province was selected as the research area, using soil samples collected at 60 points in 2017. The single factor pollution index (Pi), Nemero comprehensive pollution index, and potential ecological risk index (RI) were used to evaluate the content characteristics and potential ecological risks of eight heavy metal elements (As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn), and positive definite matrix factor analysis models (PMF) were used to analyze their sources of pollution. The results were as follows:① the content of eight heavy metal elements in the study area exceeded the standard, and the Nemeiro comprehensive pollution index showed that the proportions of light, moderate, and heavy pollution in the study area were 63%, 8%, and 2%, respectively. Unpolluted and lightly polluted samples accounted for 27% and were thus basically lightly polluted. ②The comprehensive potential ecological risk index showed that the RI of soil heavy metals was 39.58-224.15, the proportions of samples with low and medium ecological risks were 73.33% and 25%, respectively, and the proportion of sites with severe ecological risks was 1.67%. Although this site had the highest ecological risk, the content of heavy metals was lower than the background value of soil elements in the province. ③Six pollution sources were obtained through the PMF model:natural sources, agricultural activity sources, mixed sources composed of copper mining and transportation, industrial activity sources, transportation sources, and domestic waste emission sources. The contribution rates of each source were 24.8%, 17.7%, 17.7%, 17.6%, 12.0%, and 10.2%, respectively.

Glutathione S-transferase mu-1, glutathione S-transferase theta-1 null genotypes, and oral cancer risk: A meta-analysis in the Chinese population.

AIM OF STUDY: Several studies have evaluated the correlation between glutathione S-transferase mu-1 (GSTM1), GST theta-1 (GSTT1) polymorphisms and oral cancer in Chinese people. However, the results are inconsistent. To assess the effects of GSTM1, GSTT1 null genotypes on the risk for development of oral cancer in the Chinese population, a meta-analysis was performed. MATERIALS AND METHODS: Studies were identified using PubMed and Chinese databases through February 2016. The associations were assessed with pooled odds ratios (ORs) and 95% confidence intervals (CIs). RESULTS: This meta-analysis included six studies with 1306 oral cancer cases and 1484 controls. In the overall analysis, no significant association between GSTM1, GSTT1 polymorphisms and oral cancer was found in the Chinese population. In the subgroup analyses by geographic areas and source of controls, significant risk was found between GSTM1 null genotype and oral cancer in Mainland China (OR = 2.715, 95% CI = 2.17-3.38), but not in Taiwan China. CONCLUSION: Our meta-analysis suggested that GSTM1 null genotype might be associated with an increased risk of developing oral cancer in individuals from Mainland China.

[Relationship between dental caries and salivary proteome by electrospray ionization ion-trap tandem mass spectrometry in children aged 6 to 8 years].

OBJECTIVE: To explore the relationship between salivary proteome and dental caries and to promote the biomarker studies of dental caries susceptibility by comparing the salivary proteome of caries-active children and caries-free children with electrospray ionization ion-trap tandem mass spectrometry (ESI-MS/MS). METHODS: Ten caries-active children and ten caries-free children were sampled. The salivary proteome of the two groups was studied, and the differential protein between the two groups was analyzed by ESI-MS/MS after sodium dodecyl sulfate polyacrylamide gel electrophoresis, filter-aided sample preparation, and liquid chromatography. RESULTS: The concentration of salivary protein was higher in the caries-active group than in the caries-free group. The polypeptide counts of thecaries-active and caries-free groups were 602 and 481, which belonged to 286 and 227 proteins, respectively. The differential polypeptide count of the two groups was 361, and the differential protein count was 118. The detected proteins included matrix metalloproteinase-9 (MMP9), mucin-7 (MUC7), lactotransferrin (LTF), carbonic anhydrase 6 (CA6), azurocidin (AZU), and cold agglutinin. CONCLUSION: The total salivary protein was higher in the caries-active group than in the caries-free group. The preliminary detection of differential proteins (MMP9, MUC7, LTF, CA6, AZU, and cold agglutinin) may lay some foundation for biomarker research of dental caries susceptibility.

[RANKL and OPG expression in bone marrow-derived mesenchymal stem cells of ovariectomied promotes osteoclast development and enhances its function].

OBJECTIVE: To investigate the expression of receptor activator of nuclear factor-kappa B lig (RANKL), osteoprotegerin (OPG) in bone marrow mesenchymal stem cells (BMSCs) and its impact on osteoclast formation and function in the ovariectomied mice. METHODS: An animal model of osteoporosis was established by ovariectomy (OVX bilateral ovarian resection) in 8-week-old healthy female mice. The sham group was the 8-week-old healthy female mice with bilateral resection. Macrophages from mice were inducted by M-CSF and RANKL, and co-cultured with the BMSCs collected from mice in the OVX group and sham group, respectively. The osteoclast numbers of the two groups were compared by TRAP staining. The resorption pits were measured by toluidine blue staining. The level of RANKL/OPG expression was detected by RT-PCR and Western blotting. RESULTS: TRAP assay and toluidine blue staining showed that the numbers of osteoclasts and resorption pits in OVX group were more than that in the sham group. The expression of RANKL in BMSC was lower in sham group than that of the OVX group. On the contrary, the expression of OPG in BMSCs was higher in the shame group than that of the OVX group. CONCLUSION: Expression of RANKL/OPG are regulated by estrogen in BMSCs. RANKL and OPG expression promotes osteoclast development and enhances its function under the condition of estrogen deficiency.