Aging rate, environmental risk and production efficiency of the low-density polyethylene (LDPE) films with contrasting thickness in irrigated region.

Physical thickness of low-density polyethylene (LDPE) films might determine the release rate of phthalic acid esters (PAEs) & structural integrity and affect production efficiency. However, this critical issue is still unclear and little reported. Aging effects were evaluated in LDPE films with the thickness of 0.006, 0.008, 0.010 and 0.015 mm in a maize field of irrigation region. The Scanning electron microscope (SEM) results showed that the proportion of damaged area (Dam) to total area of LDPE films was massively lowered with increasing thickness after aging. The highest and lowest Dam was 32.2% and 3.5% in 0.006 and 0.015 mm films respectively. Also, the variations in peak intensity of asymmetric & symmetrical stretching vibrations (ASVI & SSVI) were detected using Fourier transform infrared spectrum (FTIR), indicating that the declines in peak intensity tended to be slower with thickness. Interestingly, the declines in physical integrity were tightly associated with increasing exhalation rate of PAEs. Average releasing rate of PAEs was 38.2%, 31.4%, 31.5% and 19.7% in LDPE films from 0.006 to 0.015 mm respectively. Critically, thicker film mulching can lead to greater soil water storage at plough layer (SWS-PL) and better thermal status, accordingly harvesting higher economic benefit. Therefore, LDPE film thickening may be a solution to reduce environmental risk but improve production efficiency in arid region.

Naringin-loaded polymeric micelles as buccal tablets: formulation, characterization, in vitro release, cytotoxicity and histopathology studies.

Naringin (NG) has been proved to have numerous notable biological effects, including anti-inflammatory effect, anti-cancer effect, and anti-ulcer effect, yet there are no clinical preparations of naringin due to its poor solubility and low dissolution rate after oral administration. In this study, in order to overcome these problems, NG was encapsulated into MPEG-PCL micelles (NGMs) by using a thin-film hydration method. NMGs were in a typical core-shell structure, with a mall particle size (23.95 ± 0.51 nm), high drug loading, and encapsulation efficiency. In vitro release of NGMs indicated that the dissolution of NG was increased after being encapsulated in the micelles. NGMs were nontoxic in the cytotoxicity and histopathology studies. Furthermore, when the freeze-dried NGMs were compressed into buccal tablets (NGBTs) by direct compression, the release speed of NG under simulated oral cavity condition from NGBTs was higher than the control tablets, with the accumulated dissolution at 93.13% in 8 hours. In conclusion, NGMs and NGBTs represent a promising drug delivery system for NG, which has the potential to improve the current treatment of oral diseases.

Plant biomass mediates the decomposition of polythene film-sourced pollutants in soil through plastisphere bacteria island effect.

The polyethylene (PE) film mulching as a water conservation technology has been widely used in dryland agriculture, yet the long-term mulching has led to increasing accumulation of secondary pollutants in soils. The decomposition of PE film-sourced pollutants is directly associated with the enrichment of specific bacterial communities. We therefore hypothesized that plant biomass may act as an organic media to mediate the pollutant decomposition via reshaping bacterial communities. To validate this hypothesis, plant biomass (dried maize straw and living clover) was embedded at the underlying surface of PE film, to track the changes in the composition and function of bacterial communities in maize field across two years. The results indicated that both dry crop straw and alive clover massively promoted the α-diversity and abundance of dominant bacteria at plastisphere, relative to bulk soil. Bacterial communities tended to be clustered at plastisphere, forming the bacteria islands to enrich pollutant-degrading bacteria, such as Sphingobacterium, Arthrobacter and Paracoccus. As such, plastisphere bacteria islands substantially enhanced the degradation potential of chloroalkene and benzoate (p < 0.05). Simultaneously, bacterial network became stabilized and congregated at plastisphere, and markedly improved the abundance of plastisphere module hubs and connectors bacteria via stochastic process. Particularly, bacterial community composition and plastic film-sourced pollutants metabolism were evidently affected by soil pH, carbon and nitrogen sources that were mainly derived from the embedded biomass. To sum up, plant biomass embedding as a nature-based strategy (NbS) can positively mediate the decomposition of plastic-sourced pollutants through plastisphere bacteria island effects.

Thickness effects of polyethylene and biodegradable film residuals on soil properties and dryland maize productivity.

Plastic film residuals are increasingly remaining in cultivated lands. However, it is a critical issue how residual plastic type and thickness affect soil properties and crop yield. To address this issue, in situ landfill was conducted using thick polyethylene (PEt1), thin polyethylene (PEt2), thick biodegradable (BIOt1), thin biodegradable (BIOt2) residues, and CK (control) with no residues landfill in a semiarid maize field. The findings demonstrated that the impact of various treatments on soil characteristics and maize yield varied considerably. Soil water content decreased by 24.82% in PEt1 and 25.43% in PEt2, compared to BIOt1 and BIOt2, respectively. BIOt2 treatment increased soil bulk density by 1.31 g cm-3 and lowered soil porosity by 51.11%, respectively; it also elevated the silt/clay proportion by 49.42% relative to CK. In contrast, microaggregate composition in PEt2 was higher (43.02%). Moreover, BIOt2 lowered soil nitrate (NO3-) and ammonium (NH4+) content. Compared with other treatments, BIOt2 resulted in significantly higher soil total nitrogen (STN) and lower SOC/STN. Finally, BIOt2 exhibited the lowest water use efficiency (WUE) (20.57 kg ha-1 mm-1) and yield (6896 kg ha-1) among all the treatments. Therefore, BIO film residues exhibited detrimental impacts on soil quality and maize productivity compared to PE film ones. Considering film thickness, thin residual films more evidently influenced soil quality and maize productivity than thick film ones.

Polyethylene film mulching enhances the microbial carbon-use efficiency, physical and chemical protection of straw-derived carbon in an Entisol of the Loess Plateau.

The global use of agricultural polyethylene mulches has emerged as a widespread farming practice, however, its effects on the fate and dynamics of crop straw-derived C in soil microbial biomass C (MBC), aggregate-associated and chemical recalcitrance-related C fractions are rarely assessed in situ. A two-year field experiment using 13C-labeled maize stem was carried out to quantify the allocation and dynamics of straw-C in an Entisol with and without plastic mulching. The results indicated that across the treatments, from 49.2% to 56.4% of straw-13C was released as CO2-C, from 34.9% to 43.1% was sequestrated as SOC pool, and from 6.7% to 9.7% remained undecomposed at the end of the experiment. Compared to non-mulching, plastic mulching significantly decreased the straw-derived CO2-C emissions by 14.6%, partially owing to the increased incorporation of straw-C into SOC pool. Across the treatments, the straw-derived MBC ranged from 14.4 to 147.9 mg 13C kg-1; and plastic mulching increased straw-derived MBC and microbial C use efficiency (CUE) of straw residue by 41.2% and 35.2% compared with non-mulching, respectively. The allocation dynamics of straw-C in each soil aggregate followed a sustained upward trend with time, while a significantly higher straw-C was incorporated into both macro- (> 0.25 mm) and micro-aggregates (0.25-0.053 mm) with plastic mulching. Compared to the non-mulching, plastic mulching enhanced the inclusion of straw-13C in the chimerically more stable C fraction, especially at the late experimental period. We conclude that crop straw return combined with plastic mulching could improve SOC sequestration by enhancing microbial CUE, physical and chemical protection of straw-derived C in this dryland cropping system.

Preparation, characterization, and evaluation of amphotericin B-loaded MPEG-PCL-g-PEI micelles for local treatment of oral Candida albicans.

Fatal Candida albicans infections in the mucosal system can occur in association with immune-compromised diseases and dysbacteriosis. Currently, amphotericin B (AmB) is considered to be the most effective antibiotic in the treatment of C. albicans infections, but its clinical application is limited by side effects and poor bioavailability. In order to use AmB in the local treatment of oral C. albicans infections, AmB/MPEG-PCL-g-PEI (monomethoxy poly(ethylene glycol)-poly(epsilon-caprolactone)-graft-polyethylenimine, MPP) micelles were prepared. A series of characterizations were performed. The micelles allowed a sustained in vitro release in both normal oral conditions (pH 6.8) and C. albicans infection conditions (pH 5.8). Then, buccal tablets containing freeze-dried powder of AmB/MPP micelles were produced by direct compression process and evaluated as regards to weight variation, hardness, and friability. In vitro drug release of the buccal tablets was measured in both the United States Pharmacopeia dissolution apparatus and the dissolution rate test apparatus, which was previously designed for simulating in vivo conditions of the oral cavity. The buccal tablets could sustainably release within 8 h and meet the antifungal requirements. Regarding safety assessment of AmB/MPP micelles, in vivo histopathological data showed no irritation toward buccal mucosa of the rats in both optical microscopy and ultrastructure observation of the tissues. MTT experiment proved that AmB/MPP micelles reduced the cytotoxicity of AmB. The micelles delivered through the gastrointestinal route were also found to be non-systemic toxicity by liquid chromatography-mass spectrometry analysis. Furthermore, the antifungal action of AmB/MPP micelles was evaluated. Although AmB/MPP had no obvious improvement as compared to AmB alone in the antifungal effect on planktonic C. albicans, the micelles significantly enhanced the antifungal activity against the biofilm state of C. albicans. Thus, it was concluded that AmB/MPP micelles represent a promising novel drug delivery system for the local treatment of oral C. albicans infections.

Dendrobium candidum extract increases the expression of aquaporin-5 in labial glands from patients with Sjögren's syndrome.

This study aimed to investigate the mechanism of Dendrobium candidum extract in promoting expression of aquaporin-5 for treatment of Sjögren's syndrome (SS). Sixteen patients with SS suffered from deficient secretion of saliva due to an autoimmune destruction of salivary glands leading to dry mouth symptoms (xerostomia). However, glandular dysfunction also occurred without destruction. Based upon its abnormal distribution in SS salivary glands, a potential role of the water channel protein aquaporin-5 (AQP-5) in the pathogenesis of SS was proposed. After oral administration of D. candidum extracted liquid (DCEL) for 1 week, saliva and salivary gland biopsies from labial glands of patients were collected and examined by employing immunoreactivity and immunohistochemistry techniques. Results showed that salivary secretion increased by about 65% in patients treated with DCEL as compared with the control group. Higher labeling indices (percentage of acinus area immunoreactive for AQP-5) in the biopsies were found in SS patients who had taken DCEL. This study demonstrated that D. candidum would regulate the expression of AQP-5 in labial glands of SS patients and thereby promoted secretion of saliva to improve dry mouth symptoms.

Novel thymopentin release systems prepared from bioresorbable PLA-PEG-PLA hydrogels.

Copolymers were synthesized by ring opening polymerization of l- or d-lactide in the presence of dihydroxyl PEG with molar mass of 6000, 12,000 and 20,000, using zinc lactate as catalyst. Bioresorbable hydrogels were obtained by mixing PLLA-PEG-PLLA and PDLA-PEG-PDLA aqueous solutions due to stereocomplexation between PLLA and PDLA chains. Rheological measurements show that the hydrogels present typical viscoelastic behaviors, although degradation could occur during the gelation process. Thymopentin was taken as a model drug to evaluate the potential of PLA-PEG-PLA hydrogels as carrier of hydrophilic drugs. Various parameters such as copolymer concentration, drug load, copolymer composition and the difference between sol and gel were considered. The release profiles are characterized by an initial burst followed by slower release. Higher copolymer concentration leads to slower release rate and less burst effect due to more compact structure which disfavors drug diffusion. Similarly, higher molar mass of the copolymers disfavors the release of TP5, and hydrogels composed of both PLLA/PEG and PDLA/PEG present slower release rates than single copolymer solutions. In contrast, drug load exhibits little influence on the release profiles due to the high water solubility of TP5. In all cases, nearly 80% of TP5 is released. In vivo studies proved the potential of TP5 containing hydrogels, especially those with a concentration of 25%. Both the CD4(+)/CD8(+) ratio and the morphology of thymus indicate the immunization efficacy of the TP5 release systems based on PLA/PEG hydrogels.