High-speed and efficient removal of uranium (VI) from aqueous solution by hydroxyapatite-modified ordered mesoporous carbon (CMK-3).

In recent years, the synthesis and application of green, cost-effective, and sustainable materials for uranium (VI) removal was significant to environmental protection. The ordered mesoporous carbon (CMK-3) supported different mass of hydroxyapatite materials (HAP@CMK-3) were facilely synthesized via hydrothermal method. The resultant materials were characterized by XRD, FT-IR, BET, SEM, TEM mapping, and XPS, and implemented for immobilizing U(VI). Not only the specific surface area of HAP (7.01 m2/g) was increased by the loading on CMK-3 (818.37 m2/g), but also the adsorption capacity of CMK-3 was increased by HAP modification. Impressively, HAP@CMK-3 exhibited highly adsorption capacity of U(VI) with the increase of HAP deposition and was capable of achieving fast reaction. Therein to, the specific surface area of HAP@CMK-3(2:1) was 253.68 m2/g, as well as the adsorption capacity was up to 1072 mg/g (fitted by Langmuir isotherm, at pH=3.0, 298 K) and the adsorption process was completed in 30 min (followed by pseudo-second-order kinetic). The adsorption mechanisms of U(VI) on HAP@CMK-3 involved electrostatic forces, ionic interactions, and chemical complexation. This work offered new avenues to address the limitations of cost and less secondary pollution for the removal of U(IV) from wastewater.

Synergistic Inhibitory Effect of Polymyxin B in Combination with Ceftazidime against Robust Biofilm Formed by Acinetobacter baumannii with Genetic Deficiency in AbaI/AbaR Quorum Sensing.

Carbapenem resistance of Acinetobacter baumannii poses challenges to public health. Biofilm contributes to the persistence of A. baumannii cells. This study was designed to investigate the genetic relationships among carbapenem resistance, polymyxin resistance, multidrug resistance, biofilm formation, and surface-associated motility and evaluate the antibiofilm effect of polymyxin in combination with other antibiotics. A total of 103 clinical A. baumannii strains were used to determine antibiotic susceptibility, biofilm formation capacity, and motility. Enterobacterial repetitive intergenic consensus (ERIC)-PCR fingerprinting was used to determine the genetic variation among strains. The distribution of 17 genes related to the resistance-nodulation-cell division (RND)-type efflux, autoinducer-receptor (AbaI/AbaR) quorum sensing, oxacillinases (OXA)-23, and insertion sequence of ISAba1 element was investigated. The representative strains were chosen to evaluate the gene transcription and the antibiofilm activity by polymyxin B (PB) in combination with merapenem, levofloxacin, and ceftazidime, respectively. ERIC-PCR-dependent fingerprints were found to be associated with carbapenem resistance and multidrug resistance. The presence of blaOXA-23 was found to correlate with genes involved in ISAba1 insertion, AbaI/AbaR quorum sensing, and AdeABC efflux. Carbapenem resistance was observed to be negatively correlated with biofilm formation and positively correlated with motility. PB in combination with ceftazidime displayed a synergistic antibiofilm effect against robust biofilm formed by an A. baumannii strain with deficiency in AbaI/AbaR quorum sensing. Our results not only clarify the genetic correlation among carbapenem resistance, biofilm formation, and pathogenicity in a certain level but also provide a theoretical basis for clinical applications of polymyxin-based combination of antibiotics in antibiofilm therapy. IMPORTANCE Deeper explorations of molecular correlation among antibiotic resistance, biofilm formation, and pathogenicity could provide novel insights that would facilitate the development of therapeutics and prevention against A. baumannii biofilm-related infections. The major finding that polymyxin B in combination with ceftazidime displayed a synergistic antibiofilm effect against robust biofilm formed by an A. baumannii strain with genetic deficiency in AbaI/AbaR quorum sensing further provides a theoretical basis for clinical applications of antibiotics in combination with quorum quenching in antibiofilm therapy.