Heteroaggregation and deposition behaviors of carboxylated nanoplastics with different types of clay minerals in aquatic environments: Important role of calcium(II) ion-assisted bridging.

The widespread utilization of plastic products ineluctably leads to the ubiquity of nanoplastics (NPs), causing potential risks for aquatic environments. Interactions of NPs with mineral surfaces may affect NPs transport, fate and ecotoxicity. This study aims to investigate systematically the deposition and aggregation behaviors of carboxylated polystyrene nanoplastics (COOH-PSNPs) by four types of clay minerals (illite, kaolinite, Na-montmorillonite, and Ca-montmorillonite) under various solution chemistry conditions (pH, temperature, ionic strength and type). Results demonstrate that the deposition process was dominated by electrostatic interactions. Divalent cations (i.e., Ca2+, Mg2+, Cd2+, or Pb2+) were more efficient for screening surface negative charges and compressing the electrical double layer (EDL). Hence, there were significant increases in deposition rates of COOH-PSNPs with clay minerals in suspension containing divalent cations, whereas only slight increases in deposition rates of COOH-PSNPs were observed in monovalent cations (Na+, K+). Negligible deposition occurred in the presence of anions (F-, Cl-, NO3-, CO32-, SO42-, or PO43-). Divalent Ca2+ could incrementally facilitate the deposition of COOH-PSNPs through Ca2+-assisted bridging with increasing CaCl2 concentrations (0-100 mM). The weakened deposition of COOH-PSNPs with increasing pH (2.0-10.0) was primarily attributed to the reduce in positive charge density at the edges of clay minerals. In suspensions containing 2 mM CaCl2, increased Na+ ionic strength (0-100 mM) and temperature (15-55 ◦C) also favored the deposition of COOH-PSNPs. The ability of COOH-PSNPs deposited by four types of clay minerals followed the sequence of kaolinite > Na-montmorillonite > Ca-montmorillonite > illite, which was related to their structural and surface charge properties. This study revealed the deposition behaviors and mechanisms between NPs and clay minerals under environmentally representative conditions, which provided novel insights into the transport and fate of NPs in natural aquatic environments.

Comparative impact of bacitracin and select feed additives in the feeding program of Lohmann LSL-Lite pullets at the onset of lay through to 31 weeks of age.

There are limited investigations on the role of feed additives in easing transition of pullets to egg production phase. We investigated the effects of supplementation of bacitracin methylene disalicylate (BMD) and select feed additives (myristic acid [MA], benzoic acid [BA], and Aspergillus niger probiotic [PRO]) in feeding program for pullets from the onset of lay through to 31 weeks of age (woa). Parameters measured included hen-day egg production (HDEP), feed intake (FI), feed conversion ratio (FCR), egg quality characteristics, ceca microbial activity, apparent retention of components, and plasma metabolites. A total of 1,200 Lohmann LSL Lite pullets were procured at 18 woa and placed in enriched cages (30 birds/cage) based on body weight (BW) and allocated to five diets. The diets were a basal diet formulated to meet specifications or basal mixed with either BMD, MA, BA, or PRO. Birds had free access to feed and water throughout the experiment. Between 18 and 20 woa, birds fed BMD ate a similar (P > 0.05) amount of feed to BA birds, but more (P = 0.0003) than birds fed basal, MA, or PRO diets. Basal birds had lower HDEP (P = 0.001) and lighter eggs (P < 0.0001) than birds fed any of the feed additives between 21 and 31 woa. The basal hens had a higher (P = 0.009) abundance of Escherichia coli than birds fed BMD, BA, and PRO diets. Consequently, BMD, BA, and PRO birds had a higher (P = 0.011) Lactobacilli: E. coli ratio (LER) than hens fed the basal diet. Specifically, relative to basal-fed hens, the LER of the BMD, MA, BA, and PRO hens was higher by 37%, 21%, 26%, and 45%, respectively. Moreover, birds fed PRO tended to have a higher concentration of ceca digesta acetic acid (P = 0.072) and a lower concentration of isobutyric acid (P = 0.096). In conclusion, supplementing pullet diets with broad-spectrum antibiotics or feed additives (MA, BA, and PRO) had a positive impact on FI, and egg production linked to modulation of indices of gut health. The results suggested supplementing feed additives in feeding programs for pullets at the onset of lay can bolster productivity outcomes.

Progress in the applications of atomic force microscope (AFM) for mineralogical research.

Mineral surface properties and mineral-aqueous interfacial reactions are essential factors affecting the geochemical cycle, related environmental impacts, and bioavailability of chemical elements. Compared to macroscopic analytical instruments, an atomic force microscope (AFM) provides necessary and vital information for analyzing mineral structure, especially the mineral-aqueous interfaces, and has excellent application prospects in mineralogical research. This paper presents recent advances in the study of properties of minerals such as surface roughness, crystal structure and adhesion by atomic force microscopy, as well as the progress of application and main contributions in mineral-aqueous interfaces analysis, such as mineral dissolution, redox and adsorption processes. It describes the principles, range of applications, strengths and weaknesses of using AFM in combination with IR and Raman spectroscopy instruments to characterization of minerals. Finally, according to the limitations of the AFM structure and function, this research proposes some ideas and suggestions for developing and designing AFM techniques.

Pharmacokinetics and pharmacodynamics of isopropoxy benzene guanidine against Clostridium perfringens in an intestinal infection model.

This study aimed to evaluate the antibacterial activity of isopropoxy benzene guanidine (IBG) against C. perfringens based on pharmacokinetics/pharmacodynamics (PK/PD) modeling in broilers. The PK parameters of IBG in the plasma and ileal content of C. perfringens-infected broilers following oral administration at 2, 30, and 60 mg/kg body weight were investigated. in vivo PD studies were conducted over oral administration ranging from 2 to 60 mg/kg and repeated every 12 h for 3 days. The inhibitory I max model was used for PK/PD modeling. Results showed that the MIC of IBG against C. perfringens was 0.5-32 mg/L. After oral administration of IBG, the peak concentration (C max ), maximum concentration time (T max ), and area under the concentration-time curve (AUC) in ileal content of broilers were 10.97-1,036.64 mg/L, 2.39-4.27 h, and 38.31-4,266.77 mg·h/L, respectively. After integrating the PK and PD data, the AUC0 - 24h /MIC ratios needed for the bacteriostasis, bactericidal activity, and bacterial eradication were 4.00, 240.74, and 476.98 h, respectively. For dosage calculation, a dosage regimen of 12.98 mg/kg repeated every 12 h for 3 days was be therapeutically effective in broilers against C. perfringens with MIC ≤ 2 mg/L. In addition, IBG showed potent activity against C. perfringens, which may be responsible for cell membrane destruction. These results can facilitate the evaluation of the use of IBG in the treatment of intestinal diseases in broilers caused by C. perfringens.

Enhancement of the oral bioavailability of isopropoxy benzene guanidine though complexation with hydroxypropyl-ß-cyclodextrin.

Isopropoxy benzene guanidine (IBG) is a novel substituted benzene guanidine analogue with antibacterial activity against multidrug-resistant bacteria. However, the bioavailability of IBG is not optimal due to its finite aqueous solubility, thus hampering its potential therapeutic exploitation. In this study, we prepared IBG/hydroxypropyl-ß-CD (IBG/HP-ß-CD) complex, and characterized it by differential scanning calorimetry, Fourier transform infrared spectroscopy, powder X-ray diffraction, and scanning electron microscopy. Physicochemical characterization indicated that the crystal morphology of IBG transformed into an amorphous state, thus forming IBG/HP-ß-CD inclusion complexes. Complexation with HP-ß-CD significantly improve the aqueous solubility, pharmaceutical properties, absorption, and bioavailability of IBG.

Pharmacokinetics and Pharmacodynamics of Colistin Combined With Isopropoxy Benzene Guanidine Against mcr-1-Positive Salmonella in an Intestinal Infection Model.

Plasmid-borne colistin resistance mediated by mcr-1 is a growing problem, which poses a serious challenge to the clinical application of colistin for Gram-negative bacterial infections. Drug combination is one of the effective strategies to treat colistin-resistant bacteria. Here, we found a guanidine compound, namely, isopropoxy benzene guanidine (IBG), which boosted the efficacy of colistin against mcr-1-positive Salmonella. This study aimed to develop a pharmacokinetics/pharmacodynamics (PK/PD) model by combining colistin with IBG against mcr-1-positive Salmonella in an intestinal infection model. Antibiotic susceptibility testing, checkerboard assays and time-kill curves were used to investigate the antibacterial activity of the synergistic activity of the combination. PK studies of colistin in the intestine were determined through oral gavage of single dose of 2, 4, 8, and 16 mg/kg of body weight in broilers with intestinal infection. On the contrary, PD studies were conducted over 24 h based on a single dose ranging from 2 to 16 mg/kg. The inhibitory effect I max model was used for PK/PD modeling. The combination of colistin and IBG showed significant synergistic activity. The AUC0-24h /MIC index was used to evaluate the relationship between PK and PD, and the correlation was >0.9085. The AUC0-24h /MIC targets in combination required to achieve the bacteriostatic action, 3-log10 kill, and 4-log10 kill of bacterial counts were 47.55, 865.87, and 1894.39, respectively. These results can facilitate the evaluation of the use of IBG as a potential colistin adjuvant in the treatment of intestinal diseases in broilers caused by colistin-resistant Salmonella.

Synergistic Effects of Capric Acid and Colistin against Colistin-Susceptible and Colistin-Resistant Enterobacterales.

Colistin is a last-line antibiotic against Gram-negative pathogens. However, the emergence of colistin resistance has substantially reduced the clinical effectiveness of colistin. In this study, synergy between colistin and capric acid was examined against twenty-one Gram-negative bacterial isolates (four colistin-susceptible and seventeen colistin-resistant). Checkerboard assays showed a synergistic effect against all colistin-resistant strains [(FICI, fractional inhibitory concentration index) = 0.02-0.38] and two colistin-susceptible strains. Time-kill assays confirmed the combination was synergistic. We suggest that the combination of colistin and capric acid is a promising therapeutic strategy against Gram-negative colistin-resistant strains.

Isopropoxy Benzene Guanidine Kills Staphylococcus aureus Without Detectable Resistance.

Serious infections caused by multidrug-resistant Staphylococcus aureus clearly urge the development of new antimicrobial agents. Drug repositioning has emerged as an alternative approach that enables us to rapidly identify effective drugs. We first reported a guanidine compound, isopropoxy benzene guanidine, had potent antibacterial activity against S. aureus. Unlike conventional antibiotics, repeated use of isopropoxy benzene guanidine had a lower probability of resistance section. We found that isopropoxy benzene guanidine triggered membrane damage by disrupting the cell membrane potential and cytoplasmic membrane integrity. Furthermore, we demonstrated that isopropoxy benzene guanidine is capable of treating invasive MRSA infections in vivo studies. These findings provided strong evidence that isopropoxy benzene guanidine represents a new chemical lead for novel antibacterial agent against multidrug-resistant S. aureus infections.

Unraveling the Mystery of Stöber Silica's Microporosity.

Puzzling aspects of the microporous structure of Stöber silica, including inconsistencies in the BET specific surface area and the long measurement time required for N2 adsorption, hinder further research on and potential applications of this material. In this work, Stöber silica samples prepared using systematic and detailed post-treatment methods were characterized by N2 adsorption, scanning electron microscopy, transmission electron microscopy, inductively coupled plasma optical emission spectrometry, elemental analysis, and Fourier transform infrared spectroscopy. We have found that the often overlooked sample preparation conditions may be the main causes that perplex the gas adsorption characterization results of Stöber silica samples. The pore-blocking processes associated with a variety of sample treatment methods are discussed in detail. Strong evidence for the particle growth model and pore-blocking mechanism involving ethoxyl groups, Si species, and condensation of silanols is provided. A remarkable result is that the measurement time is shortened from 1 month in our previous work to 2-3 days for samples with large specific surface areas. A suitable post-treatment condition is recommended to obtain microporous Stöber silica with a short measurement time, including water washing, low temperature drying without a vacuum, and a short storage time.

Understanding Stöber silica's pore characteristics measured by gas adsorption.

Controversial reports regarding Stöber silica's microporosity and specific surface area remain in the literature despite decades of widespread applications. In this work, Stöber silica samples prepared under controlled reaction time and postsynthesis washing/drying conditions were characterized by nitrogen adsorption at 77 K, transmission electron microscopy, elemental analysis, Fourier transform infrared spectroscopy, thermal analysis, and evolved gas analysis. Our experimental results demonstrated the important but often overlooked effects of reaction time and postsynthesis treatments on Stöber silica's pore characteristics, as evidenced by the strikingly large range of BET specific surface area (11.3-309.7 m(2)/g). A simple micropore filling and blocking mechanism compatible with an existing Stöber silica growth model incorporating both aggregation and monomer addition steps was proposed to explain all our experimental findings. The carbon and nitrogen contents appear to serve well as the indicative link between our experimental variables and the resulting pore blocking by TEOS and its derivatives. A suitable combination of experimental conditions is recommended in order to make microporous Stöber silica samples with large specific surface area, including a short reaction time, water washing, and drying at moderate temperature preferably under vacuum.

[Purification of immunoglobulin and serum albumin from serum via strong anion exchange chromatography coupled with molecular exclusion chromatography].

The isoelectric points of immunoglobulin (Ig) and serum albumin (SA) in animal serum are about 7.8 and 4.8, respectively. Based on their larger difference of isoelectric points, Q Sepharose-XL strong anion exchange chromatography coupled with molecular exclusion chromatography was used to purify Ig and SA simultaneously from the high immune rabbit serum. After the Q Sepharose-XL strong anion exchange column was equilibrated with 0.02 mol/L Tris-HCl buffer of pH 8.0, a 10-fold dilution sample of rabbit serum was loaded onto the column and the pH gradient elution was performed. With the low flow rate of elution of 0.3 mL/min, the high-purity Ig was obtained when the elution pH was at 6.0. Continuously eluted at pH 4.0 with the same flow rate of elution, the SA was obtained and its purity was greater than 95% after molecular exclusion chromatography through Sephadex G-75. The purified Ig and SA were demonstrated to maintain normal activities by activity analysis. The results of protein content showed that the purification recoveries of Ig and SA were over 95% and 90%, respectively. The method has the advantages of simple operation and rapidity, and the Ig and SA purified simultaneously from the animal serum could maintain normal activities.

Functional characterizations of malonyl-CoA:acyl carrier protein transacylase (MCAT) in Eimeria tenella.

Eimeria tenella, an apicomplexan parasite in chickens, possesses an apicoplast and its associated metabolic pathways including the Type II fatty acid synthesis (FAS II). Malonyl-CoA:acyl-carry protein transacylase (MCAT) encoded by the fabD gene is one of the essential enzymes in the FAS II system. In the present study, the entire E. tenella MCAT gene (EtfabD) was cloned and sequenced. Immunolabeling located this protein in the apicoplast organelle in coccidial sporozoites. Functional replacement of the fabD gene with amber mutation of E. coli temperature-sensitive LA2-89 strain by E. tenella EtMCAT demonstrated that EcFabD and EtMCAT perform the same biochemical function. The recombinant EtMCAT protein was expressed and its general biochemical features were also determined. An alkaloid natural product corytuberine (CAS: 517-56-6) could specifically inhibit the EtMCAT activity (IC(50)=16.47µM), but the inhibition of parasite growth in vitro by corytuberine was very weak (the predicted MIC(50)=0.65mM).

Development and validation of real-time polymerase chain reaction assays specific to four species of Eimeria.

The development of quantitative real-time polymerase chain reaction (PCR) assays specific to Eimeria acervulina, Eimeria maxima, Eimeria necatrix and Eimeria tenella is described and validated. The PCR templates adopted include a fragment of a gene encoding a microneme protein and previously characterized species-specific random amplified polymorphic DNA (RAPD) sequences. The sensitivity of each assay allowed the consistent detection of between one and 10 parasite genomes, equivalent to between one or two sporulated oocysts or a fraction of a single mature schizont, unaffected by the presence of chicken (host) or other Eimeria species DNA. Regression coefficients in excess of 0.99 over linear ranges of at least six orders of magnitude, together with comparable PCR efficiencies, demonstrated the robust reproducibility of each assay and suggest that two or more may be successfully multiplexed. The species-specific assays described here, combined with a previously published generic Eimeria species real-time PCR, provide valuable components in a "tool box" to accurately quantify the presence of specific Eimeria species in environmental or within-host phases of the lifecycle with little specialist knowledge. The application of these assays may benefit chicken husbandry, veterinary practice, quality control of live vaccine production and scientific research.