Retention and release of black phosphorus nanoparticles in porous media under various physicochemical conditions.

Black phosphorus nanosheets/nanoparticles (BPNs) are widely applied in many fields. However, the transport of BPNs in the subsurface still has not yet been reported and there is increasing concern about potential adverse impacts on ecosystems. Roles of median grain size and surface roughness, BPN concentration, and solution chemistries (pH, ionic strength, and cation types) on the retention and release of BPNs in column experiments were therefore investigated. The mobility of BPNs significantly increased with increasing grain size and decreasing surface roughness due to their influence on the mass transfer rate, number of deposition sites and retention capacity, and straining processes. Transport of BPNs was enhanced with an increase in pH and a decrease in ionic strength because of surface deprotonation and stronger repulsion that tends to reduce aggregation. The BPN transport was significantly sensitive to ionic strength, compared with other engineered nanoparticles. Additionally, charge heterogeneity and cation-bridging played a critical role in the retention of BPNs in the presence of divalent cations. Higher input concentrations increased the retention of BPNs, probably because collisions, aggregation at pore throat locations, and hydrodynamic bridging were more pronounced. Small fractions of BPNs can be released under decreasing IS and increasing pH due to the expansion of the electrical double layer and increased repulsion at convex roughness locations. A mathematical model that includes provisions for advective dispersive transport and time-dependent retention with blocking or ripening terms well described the retention and release of BPNs. These findings provide fundamental information that helps to understand the transport of BPNs in the subsurface environments.

Lactic Acid and Peroxyacetic Acid Inhibit Biofilm of Escherichia coli O157:H7 Formed in Beef Extract.

The objective of this study was to evaluate the inhibitory effect of lactic acid (LA) and peroxyacetic acid (PAA) on the biofilm formation of Escherichia coli O157:H7 in beef extract (BE). BE medium was used as the growth substrate in this study, to make the control effect closer to the situation of the factory. The biofilm inhibitory efficacy of LA and PAA was tested by using a crystal violet staining assay and microscopic examination. And then, extracellular polymeric substance (EPS) production, metabolic activity, and real-time polymerase chain reaction assay were used to reveal the biofilm inhibition mechanism of LA and PAA. The results showed that both LA and PAA significantly inhibited biofilm formation of E. coli O157:H7 at minimum inhibitory concentrations (MICs) (p < 0.05). At MIC, LA and PAA showed different effects on the biofilm metabolic activity and the EPS production of E. coli O157:H7. Supporting these findings, expression analysis showed that LA significantly suppressed quorum sensing genes (luxS and sdiA) and adhesion genes (flhC), while PAA downregulated the transcription of extracellular polysaccharide synthesis genes (adrB and adrA) and the global regulatory factor csgD. This result revealed that LA and PAA had different biofilm inhibitory mechanisms on E. coli O157:H7; LA inhibited the biofilm formation mainly by inhibiting metabolic activity, while PAA inhibited EPS production. This study provided a theoretical basis for the control of E. coli O157:H7 biofilm in the actual production process.

Effect of lutein and zeaxanthin on macular pigment and visual function in patients with early age-related macular degeneration.

PURPOSE: To determine whether supplementation with lutein and zeaxanthin improves macular pigment and visual function in patients with early age-related macular degeneration (AMD). DESIGN: Randomized, double-masked, placebo-controlled trial. PARTICIPANTS: Participants with probable AMD who were 50 to 79 years of age were screened for study eligibility from the local communities. One hundred eight subjects with early AMD were recruited. INTERVENTION: Early AMD patients were assigned randomly to receive 10 mg/day lutein (n = 27), 20 mg/day lutein (n = 27), 10 mg/day lutein plus 10 mg/day zeaxanthin (n = 27); or placebo (n = 27) for 48 weeks. Macular pigment optical density (MPOD) and visual function variables were assessed at baseline, 24 weeks, and 48 weeks. MAIN OUTCOME MEASURES: The primary outcome was MPOD. Secondary outcomes were visual function variables including best-corrected visual acuity (BCVA), contrast sensitivity (CS), photorecovery time, and Amsler grid testing results. RESULTS: Macular pigment optical density increased significantly by a mean ± standard error of 0.076 ± 0.022 density unit in the 20-mg lutein group and 0.058 ± 0.027 density unit in the lutein and zeaxanthin group during 48 weeks. There was a significant dose-response effect for lutein supplementation, and the changes in MPOD from baseline to 48 weeks were correlated negatively with baseline MPOD in all active treatment groups (r = -0.56; P<0.001). At 48 weeks, a trend toward improvement was seen in BCVA, and there was a significant between-group difference in CS at 3 and 6 cycles/degree between the 20-mg lutein group and the placebo group. The increase in MPOD related positively to the reduction in the logarithm of the minimum angle of resolution BCVA (r = -0.31; P<0.01) and the increases in CS at 4 spatial frequencies (r ranging from 0.26 to 0.38; all P<0.05). CONCLUSIONS: Among patients with early AMD, supplementation with lutein and zeaxanthin improved macular pigment, which played a causative role in boosting visual function and might prevent the progression of AMD. Future studies are required to evaluate the effect of these carotenoids on the incidence of late AMD.

Improvement of retinal function in early age-related macular degeneration after lutein and zeaxanthin supplementation: a randomized, double-masked, placebo-controlled trial.

PURPOSE: To examine the effects of lutein and zeaxanthin supplementation on retinal function using multifocal electroretinograms (mfERG) in patients with early age-related macular degeneration (AMD). DESIGN: Randomized, double-masked, placebo-controlled trial. METHODS: One hundred eight subjects with early AMD were randomly assigned to receive 10 mg/d lutein (n = 27), 20 mg/d lutein (n = 27), 10 mg/d lutein plus 10 mg/d zeaxanthin (n = 27), or placebo (n = 27) for 48 weeks. Thirty-six age-matched controls without AMD were also enrolled to compare baseline data with early AMD patients. MfERG responses and macular pigment optical densities (MPODs) were recorded and analyzed at baseline and at 24 and 48 weeks. RESULTS: There were significant reductions in N1P1 response densities in ring 1 to ring 3 in early AMD patients compared with the controls (P < .05), whereas neither N1P1 response densities in ring 4 to ring 6 nor P1 peak latencies significantly changed. After 48-week supplementation, the N1P1 response densities showed significant increases in ring 1 for the 20 mg lutein group and for the lutein and zeaxanthin group, and in ring 2 for the 20 mg lutein group. The increases in MPOD related positively to the increases in N1P1 response density in ring 1 and ring 2 for nearly all active treatment groups. N1P1 response densities in ring 3 to ring 6 or P1 peak latencies in all rings did not change significantly in any group. CONCLUSION: Early functional abnormalities of the central retina in the early AMD patients could be improved by lutein and zeaxanthin supplementation. These improvements may be potentially attributed to the elevations in MPOD.