Streptococcus Sanguis Biofilm Architecture and Its Influence on Titanium Corrosion in Enriched Artificial Saliva

Bacteria biofilm formation on metals is well-known, while biofilm architecture varies under different conditions. To date, few studies have determined the possible contribution to corrosion of titanium made by biofilm architecture. We investigated the interaction between the oral Streptococcus sanguis biofilm architecture and its influence on titanium corrosion in enriched artificial saliva using electrochemical methods and microscopic study. Patchy biofilms were observed on titanium surface after being immersed in solution containing S. sanguis. The thickness and size of the patchy biofilms increased with an increase of immersion time. The extensive pits were clearly observed by scanning electron microscopy, showing that adsorption of S. sanguis on titanium promoted the localized corrosion. The electrochemical results indicated that the corrosion rates were clearly accelerated in the presence of S. sanguis. The low icorr and high Rt in the first 48 h indicated that a typical passive behavior still remained. Our study showed that the pitting corrosion of titanium was mainly attributed to the formation of a self-catalytic corrosion cell by the co-effect of patchy biofilm and organic acid secreted by S. sanguis

Ultrasensitive Electrochemical Detection of Clostridium perfringens DNA Based Morphology-Dependent DNA Adsorption Properties of CeO2 Nanorods in Dairy Products

Foodborne pathogens such as Clostridium perfringens can cause diverse illnesses and seriously threaten to human health, yet far less attention has been given to detecting these pathogenic bacteria. Herein, two morphologies of nanoceria were synthesized via adjusting the concentration of NaOH, and CeO2 nanorod has been utilized as sensing material to achieve sensitive and selective detection of C. perfringens DNA sequence due to its strong adsorption ability towards DNA compared to nanoparticle. The DNA probe was tightly immobilized on CeO2/chitosan modified electrode surface via metal coordination, and the DNA surface density was 2.51 × 10−10 mol/cm2. Under optimal experimental conditions, the electrochemical impedance biosensor displays favorable selectivity toward target DNA in comparison with base-mismatched and non-complementary DNA. The dynamic linear range of the proposed biosensor for detecting oligonucleotide sequence of Clostridium perfringens was from 1.0 × 10−14 to 1.0 × 10−7 mol/L. The detection limit was 7.06 × 10−15 mol/L. In comparison, differential pulse voltammetry (DPV) method quantified the target DNA with a detection limit of 1.95 × 10−15 mol/L. Moreover, the DNA biosensor could detect C. perfringens extracted DNA in dairy products and provided a potential application in food quality control

Additional file 1: of Controllable Growth of the Graphene from Millimeter-Sized Monolayer to Multilayer on Cu by Chemical Vapor Deposition

Supplementary information. Figure S1. (a) The TEM image shows the corner of the graphene domains. (b–e) Selected area electron diffraction (SAED) data for small regions indicated 1 to 4. These SAED data confirm the single-crystalline structure of the graphene domains as they have the same set of sixfold symmetric diffraction points. Figure S2. The optical microscopy images of the multilayer graphene with increasing size in the center region grown by decreasing hydrogen concentration and keeping the methane for constant (0.5 sccm CH4). (a) 38 sccm H2; (b) 29 sccm H2. Figure S3. The deconvolution of the 2D band of the (a) monolayer, (b) bilayer, (c) trilayer, and (d) tetralayer graphene with Lorentzians function as shown in Fig. 3a. Figure S4. The optical microscopy images of the multilayer graphene with non-Bernal stacking transferred to SiO2. Figure S5. The deconvolution of the 2D band of the (a) monolayer, (b) bilayer, (c) trilayer, and (d) tetralayer graphene with Lorentzians function as shown in Fig. 3b. Figure S6. The G (a) and 2D (b) peak position of the multilayer grahene with Bernal and non-Bernal stacking order as shown in Fig. 3a and b, respectively. Figure S7. The I2D/IG value of the multilayer graphene with Bernal and non-Bernal stacking order as shown in Fig. 3a and b, respectively. Figure S8. The typical EDS spectrum of the probe site on the nanoparticle and not on the nanoparticle. Figure S9. The optical microscopy images of the multilayer graphene growth with 32 sccm H2, 0.5 CH4 at different time. (a) 10 min, (b) 20 min, (c) 40 min. (DOC 6452 kb