Impact of Graphene Exposure on Microbial Activity and Community Ecosystem in Saliva.

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.

Programming biosensing sensitivity by controlling the dimension of nanostructured electrode.

Development of new nanostructured materials has shown high impact for improving the performance of chemical and biological sensors. In this work, we show that by controlling the dimensions of the gold flower microelectrode (GFME), it is possible to regulate detection sensitivity of a sensor for rapid analysis of chemical species. A ~13-fold increase in sensitivity was achieved by enlarging the dimension of GFMEs from 70 to 330 µm, whereas the response dynamics are dimension-independent, with the signal attaining saturation ~20 s. Due to the intrinsic nanostructure on the microelectrode surface, our GFME exhibits excellent anti-interference property when applied to detect dopamine (DA) in the presence of 10-fold excess of ascorbic acid (AA). The regulable sensitivity, fast response dynamics, and excellent anti-interference property will make GFME an ideal sensing platform for biomedical applications. Graphical abstract ᅟ.

Graphene oxide-silver nanocomposites modulate biofilm formation and extracellular polymeric substance (EPS) production.

Biofilms with positive and negative actions ubiquitously affect medical infections, environmental remediation and industrial processes. However, it remains challenging to control the growth of harmful biofilms as well as to exploit the use of beneficial biofilms. Here we investigated the effect of an antibacterial graphene oxide-silver nanoparticles (GO-AgNPs) composite on Pseudomonas aeruginosa biofilm formation. We found that GO-AgNPs prevented biofilm formation in a dose-dependent manner, with a threshold of 15 µg mL-1. Interestingly, the bacterial biomass significantly decreased, but extracellular polymeric substance (EPS) production remarkably increased in mature biofilms treated with GO-AgNPs of an appropriate concentration, suggesting that GO-AgNPs effectively modulate biofilm development and structure. Moreover, we established that GO-AgNPs caused bacterial death via both physical damage and oxidative stress, showing the synergic action of GO and AgNPs. These findings facilitate the use of graphene-based nanocomposites for greener antibiotic applications.

Framework Nucleic Acid-Mediated Pull-Down MicroRNA Detection with Hybridization Chain Reaction Amplification.

Gastric cancer remains a disease of high mortality worldwide due to its poor prognosis. Previous studies have shown that microRNAs (miRNAs) are effective biomarkers for early diagnosis of gastric cancer. To realize sensitive detection of related miRNAs for improved early diagnosis, classification, and survival prognosis of gastric cancer, herein we developed a framework nucleic acid (FNA)-mediated microarray for quantitative analysis of multiple miRNAs. By rationally designing FNA with different sizes, we systematically modulated the surface density and lateral interactions of DNA probes, which provides an effective means for programmable tailoring of the hybridization efficiency and kinetics of the biosensing interface. We found that the hybridization efficiency was increased along with the size of the FNA and was optimum for FNA-17. In combination with the hybridization chain reaction amplification strategy, this established FNA microarray can serve as an ultrasensitive and selective analytical platform for simultaneous multiplexed detection of miRNA (e.g., FNA-miR-652, FNA-miR-627, and FNA-miR-629) biomarkers in gastric cancer.

Real-Time Continuous Identification of Greenhouse Plant Pathogens Based on Recyclable Microfluidic Bioassay System.

The development of a real-time continuous analytical platform for the pathogen detection is of great scientific importance for achieving better disease control and prevention. In this work, we report a rapid and recyclable microfluidic bioassay system constructed from oligonucleotide arrays for selective and sensitive continuous identification of DNA targets of fungal pathogens. We employ the thermal denaturation method to effectively regenerate the oligonucleotide arrays for multiple sample detection, which could considerably reduce the screening effort and costs. The combination of thermal denaturation and laser-induced fluorescence detection technique enables real-time continuous identification of multiple samples (<10 min per sample). As a proof of concept, we have demonstrated that two DNA targets of fungal pathogens (Botrytis cinerea and Didymella bryoniae) can be sequentially analyzed using our rapid microfluidic bioassay system, which provides a new paradigm in the design of microfluidic bioassay system and will be valuable for chemical and biomedical analysis.