A Sensitive "Turn-On" Fluorescent Sensor for Melamine Based on FRET Effect between Polydopamine-Glutathione Nanoparticles and Ag Nanoparticles.

In this work, Ag nanoparticles (AgNPs) were synthesized quickly by a one-step method utilizing polydopamine-glutathione nanoparticles (PDA-GNPs) as a reducing agent. The PDA-GNPs and the generated AgNPs acted as the energy donor and acceptor, respectively. Accordingly, the fluorescence of PDA-GNPs was quenched on the basis of fluorescence resonance energy transfer (FRET). In the presence of melamine, the preferential combination of Ag(I) and melamine to form Ag(I)-melamine complex prevents Ag(I) from forming AgNPs, together with fluorescence enhancement compared with the absence of melamine. Under the optimal conditions including the concentration of AgNO3, reaction time, reaction temperature, and pH, the fluorescence enhancement efficiency has a linear response to the concentration of melamine from 0.1 to 40 µM with a detection limit of 23 nM for melamine. The proposed method is simple, time-saving, and low-cost, which was further applied to detect melamine in real milk products with satisfactory results.

[Influence of different acid etching modes on bond strengths to non-carious sclerotic dentin].

PURPOSE: To evaluate the effect of different acid etching modes on bond strength between composite resin and non-carious sclerotic dentin, and to provide references for clinical application. MOTHODS: Thirty premolars with naturally-occurring non-carious cervical lesions were divided into 2 groups based on self-etch adhesive system AdperTM Easy one (AEO) and total-etch adhesive system AdperTM Single Bond2 (ASB2). Each group was further divided into 3 subgroups (ASB21, ASB22, ASB23, AEO1, AEO2, AEO3) and subjected to the following processing: ASB21 subgroup was etched for 15 s with 35% phosphoric acid and coated with binder for 15 s; ASB22 subgroup was etched for 30 s with 35% phosphoric acid and coated with binder for 15 s; ASB23 subgroup was etched for 15 s with 35% phosphoric acid and coated with binder for 30 s; AEO1 subgroup was only etched with binder for 20 s; AEO2 subgroup was etched with binder for 40 s; AEO3 subgroup was etched for 15 s with 35% phosphoric acid and coated with binder for 20 s. The samples were restored with composite resin; 24 h after saved in distilled water at room temperature, the teeth were cut into dumbbell-shaped specimens with surface areas of approximately 1.0 mm2. The microtensile bond strength (µTBS) was detected and evaluated by one-way ANOVA and SNK-q test using SPSS 17.0 software package. RESULTS: µTBS was given in MPa: AEO3>ASB22>ASB23>ASB21>AEO2>AEO1, AEO3 resulted in statistically highest bond strength and AEO1 had the lowest bond strength (P<0.05), ASB22 acquired bond strength just lower than AEO3 (P<0.05). CONCLUSIONS: Use of total-etch adhesive system increasing the etching time of phosphoric time can enhance bond strength. For self-etch adhesive system,both duplicated the time of adhesive treatment and use of phosphoric acid can improve the bond strength. Use of phosphoric acid to etch for 15 s and coated with self-etch adhesive system for 20 s achieved the highest bond strength. In either self-etch or total-etch adhesive system, use of phosphoric acid to etch for 15 s and coated with self-etch adhesive system for 20 s achieved optimal bond strength, there was the lowest bond strength when the self-etch adhesive system used as recommended time.

[The effect of calcium hydroxide on IL-6 and TNF-α expression of osteoblast in periapical tissues].

PURPOSE: To compare the effect of calcium hydroxide in different position on pH and inflammation factor expression of periapical osteoblasts. METHODS: 140 sterilized single-rooted human teeth models were randomly divided into 6 experiment groups and one control group: Group 1-3:calcium hydroxide paste was placed in the apical half of root canal, the upper half of root canal and the pulp champer; Group 4-6:Apexcal was placed in the apical half of root canal, the upper half of root canal and the pulp champer; Group 7: the control group without medication. 10 teeth of each group were placed in P.e suspension, the IL-6 and TNF-α expression of MC3T3-E1 was tested at 3 d and 7 d. The other teeth of each group were placed in distilled water, and the pH in periapical region was tested at 3, 7, 14 and 21 d. SPSS 13.0 software package was used for statistical analysis. RESULTS: Calcium hydroxide placed in different position of the root canal increased periapical pH value and reached its peak at 14 d. The group in which calcium hydroxide paste was placed in pulp chamber gained lower pH level than other experimental groups. IL-6, TNF-α expression of MC3T3-E1 pretreated by P.e suspension of experimental groups was significantly reduced compared with control group, and there was no significant difference between the experimental groups. CONCLUSIONS: Calcium hydroxide placed in different position of the root canal could increase periapical pH value and reduce IL- 6, TNF-α expression of periapical osteoblasts.

[Comparison of expression of transforming growth factor-ß1 in rat dental pulp during direct pulp capping with 2 capping agents].

PURPOSE: To examine and compare the expression of transforming growth factor-ß1(TGF-ß1) in rat dental pulp after direct pulp capping with calcium hydroxide (CH) and mineral trioxide aggregate (MTA). METHODS: The model of direct dental pulp capping after first molars was established in 28 female Wistar rats with CH and MTA. The rats were sacrificed 1, 3, 5, 7, 14,21 and 28 days after direct pulp capping. TGF-ß1 expression in pulp tissues were measured with immunohistochemical staining. The data was analyzed by Dunnett t test and paired t test with SPSS 13.0 software package. RESULTS: The results showed that no TGF-ß1 expression was detected in the control group. After direct pulp capping with MTA, TGF-ß1 expression gradually increased and reached peak expression on 5 day. TGF-ß1 expression gradually decreased afterwards and reached normal on 21 day after direct pulp. TGF-ß1 was mainly expressed in neutrophils, odontoblasts cells, vascular endothelial cells and fibroblasts. The expression of TGF-ß1 was significantly different between 2 capping agents 1, 3, 5, 7, 14 days after direct pulp capping (P<0.05). CONCLUSIONS: The results suggest that TGF-ß1 expression increases at first and then decreases after direct pulp capping. The type of capping agents has an impact on the expression of TGF-ß1 after direct pulp capping. MTA enhances more TGFß-1 expression than CH 1, 3, 5, 7 and 14 days after direct pulp capping. Supported by Science and Technology Plan Project of Liaoning Province (2009225001-2).

Subchronic safety evaluation of EPO-018B, a pegylated peptidic erythropoiesis stimulating agent, after 5-week subcutaneous injection in Cynomolgus monkeys and Sprague-Dawley rats.

EPO-018B, a synthetic peptide-based erythropoiesis stimulating agent (ESA), is coupled to polyethylene glycol (PEG) and designed to specifically bind and activate the erythropoietin (EPO) receptor to result in production of red blood cells. This study was designed to evaluate the potential subchronic toxicity of EPO-018B for Cynomolgus monkeys and Sprague-Dawley rats both at 0, 0.5, 5 and 50 mg/kg every week for 5 weeks, followed by 6-week recovery for rats and 12-week recovery for monkeys. The No Observed Adverse Effect Level (NOAEL) for rats and monkeys were both considered to be at least 0.5 mg/kg/day, the minimum toxic dose to be 5.0 mg/kg/day and the severe toxic dose to be more than 50.0 mg/kg/day. The toxicological effects included the exaggerated pharmacology and secondary sequelae that resulted from an erythropoiesis-stimulating agent treatment to healthy animals. Most treatment induced effects were reversible or showed ongoing recovery upon discontinuation of treatment. The anticipated patient population for EPO-018B treatment is targeted to be the anemia patients caused by chronic renal failure or chemotherapy against to cancer and is expected to have an ideal clinical application prospect.

[An epidemiological investigation of deciduous dental caries among 5375 preschool children aged between 3 to 6 years in Shenyang City].

PURPOSE: To investigate the status of dental caries of deciduous teeth among preschool children in Shenyang city. METHODS: According to the criteria recommended by the World Health Organization and The Second National Oral Health Investigation, the deciduous caries of 5375 preschool children aged from 3 to 6 years were clinically examined. The mean dmft and the prevalence of dental caries for each age group were calculated. The results were analyzed using SPSS11.0 software package for t test (to compare the difference between the two sample groups), one way ANOVA (to compare the differences among three and more sample groups) and chi2 test (to compare the rate of each group). RESULTS: The prevalence of dental caries was 71.29%. The mean dmft score was 3.88. The prevalence of dental caries and mean dmft increased gradually as the children were growing up (P < 0.05).Dental caries of the upper teeth was significantly more common than that of the lower teeth (P < 0.01). Most caries were minor in degree of severity, and mostly lie in the occlusal and proximal surface. The filling rate was 10.82%.As the age increase, the filling rate increased, too. CONCLUSION: Deciduous dental caries of preschool children was an important problem in Shenyang city, and the filling rate was very low. Necessary methods for early prevention of dental caries must be taken into consideration. Supported by Scientific Research Fund for College and University from Liaoning Provincial Education Bureau (Grant No. 20201316).

[Experimental study of the inhibitory effects of Chelidonium majus L. extractive on Streptococcus mutans in vitro].

PURPOSE: To study the inhibitory effects of Chelidonium majus L. extractive on the growth of Streptococcus mutans in vitro, and to explore its mechanism in caries prevention. METHODS: Streptococcus mutans 25175 was chosen as the experimental bacterium. The Chelidonium majus L. extractives chelidonine and chelerythrine were double diluted to different concentrations by two-fold dilution. The inhibitory effect of Streptococcus mutans was measured by slip diffusion method. The minimal inhibitory concentration(MIC) was also determined. 0.16% liquor hibitane was used as positive control. Spearman correlation was used for statistical analysis. RESULTS: Inhibition zone of Streptococcus mutans appeared in some concentration of chelerythrine, but no inhibition zone in each concentration of chelidonine. The MIC of chelerythrine was 0.78 mg/ml which determined by liquid culture medium. The concentration of chelerythrine was highly related to the inhibitory zone of Streptococcus mutans (r=0.99, P<0.01). CONCLUSION: The antibacterial activity of Chelidonium majus L. extractive chelerythrine on Streptococcus mutans was significant,and the antibacterial activity of the concentration 100 mg/ml was higher than that of 0.16% liquor hibitane (19.4 mm), indicating that chelerythrine can be used as an agent for prevention of dental caries.

[Study of caries polarization in 2-5 year-old children of Shenyang, China].

OBJECTIVE: To investigate dental caries polarization in 2-5 year-old children. METHODS: 3 799 random samples of 2-5 year-old children from attending kindergarten in Shenyang were selected. Means of dmft index and SiC index for each age group were calculated by WHO Collaborating Center. The subjects of each age group were further divided into subgroups of different level of dmft: the dmft of subgroup I was 0, the dmft of subgroup II was 1, the dmft of subgroup III was 2, the dmft of sub-group IV was equal to or more than 3. The obtained data were analyzed statistically with SPSS 10.0. RESULTS: 4.5% of 2-year-old children were carriers of 60.0% of the total dmft in that age group, 13.2% of 3-year-old children were carriers of 69.4% of the total dmft in that age group, 34.4% of 4-year-old children were carriers of 86.6% of the total dmft in that age group, and 47.8% of 5-year-old children were carriers of 89.8% of the total dmft of that age group. CONCLUSION: This study supports the assertion that a small percentage of persons with high dental caries rate and a large percentage of caries-free persons of early childhood caries.

[An analysis of the effect of adult tooth-brushing].

OBJECTIVE: This study observed plaque distribution on permanent dentition before and after brushing to analyze the effect of adult tooth-brushing. METHODS: 81 undergraduate were included in this study. Recorded the time of tooth-brushing, stained with disclosing tablets, plaque deposits on all permanent teeth were recorded using plaque index (PLI) before and after tooth-brushing. RESULTS: The time of tooth-brushing was from 28 s to 2 min 32 s, the mean time was 57 s, the males' was 49 s, the females' was 64 s. Statistically significant differences (P < 0.05) were found between males and females. The mean PLI of maxillary tooth was 0.41 +/- 0.03, for mandibular tooth was 0.47 +/- 0.03, there was significant difference between maxillary and mandibular. After brushing, the mean PLI of males was 0.532 +/- 0.04, of females was 0.295 +/- 0.03, there was significant difference of PLI between males and females (P < 0.05). These tooth PLI score were higher than other's mandibular and maxillary molars, these surface PLI score were higher than other's, buccal surface of maxillary molars and palatal site of maxillary molars. CONCLUSION: People should spend more time on brushing tooth. Tooth brushing should be emphasized on these tooth and surfaces with higher PLI score. Man should pay more attention to tooth brushing.

[Fluoride concentration in saliva after use of fluoride varnish].

OBJECTIVE: The purpose of this vivo study was to compare fluoride concentration in saliva of patients treated with fluoride varnish and fluoride solution. METHODS: 20 5-year-old children were selected and divided into fluoride varnish and fluoride solution groups. The samples of unstimulated whole saliva were collected at base-line before and after 0.25h,0.5h,1h,2h,6h,12h,24h treatment with fluoride varnish and fluoride solution. Saliva fluoride concentrations were measured using an ion-specific electrode. RESULTS: After 0.25h,0.5h,1h,2h,6h treatment with fluoride varnish, the values of salivary fluoride concentration were higher than baseline,the values of fluoride varnish group were higher than those in fluoride solution group after 0.5h to 6h. CONCLUSION: Compared with fluoride solution, fluoride varnish maintained a longer time of high salivary fluoride concentration.