pH Changes Research Articles

Development of a novel colorimetric pH-indicator film based on CMC/flaxseed gum/betacyanin from beetroot peels: A powerful tool to monitor the beef meat freshness

A novel indicator film based on carboxymethyl-cellulose (CMC)/flaxseed gum (FG) was developed by introducing betacyanin (BC) from beetroot peel extract. Remarkably, CMC/FG/BC film exhibited a dynamic color transition from pink to yellow in response to pH changes from 1 to 12. Beyond its pH sensitivity, the newly developed film demonstrated exceptional sensitivity to ammonia solution concentrations, detecting variation from 0.125 to 0.5 mg/mL with a significant ΔE (P < 0.05) change when a concentration of 0.5 mg/mL was added. Moreover, the inclusion of BC not only heightened the film's colorimetric capabilities but also enhanced the antioxidant, physical (moisture content, swelling index, thickness and biodegradability), and mechanical (elongation at break) properties. On the other hand, the CMC/FG/BC film's ability to provide real-time monitoring of minced beef meat quality was examined during 14 days of storage at 4 °C. The CMC/FG/BC film displayed a distinctive color change (from light pink to purple) corresponding to changes in meat samples' total volatile basic nitrogen (TVB-N) and microbial count (aerobic plate, psychrotrophic total and Enterobacteriaceae counts) during the storage period. The CMC/FG/BC film could be considered as a novel colorimetric pH indicator to monitor meat and meat derivatives' freshness. Its multifaceted properties make it valuable as an intelligent packaging used in food quality control, offering real-time insights into both pH changes and the freshness of stored meat products.

Effect of Allium Jesdianum's extract on the physicochemical, antioxidant, antimicrobial and sensory properties of Sausage characteristics

The study investigated the use of Allium Jesdianum plant extract as a natural preservative in sausage dough at varying concentrations. After preparation, chemical and microbial tests were conducted on the samples at zero, 14, 28, and 42 days. The study found no significant changes in pH, moisture, fat, or protein content, but the control samples consistently had the highest total volatile nitrogen (TVN) levels. The peroxide test revealed a significant difference between the control and extract samples. Sensory analysis indicated a significant difference between the control and the 200 and 300 ppm extracts (P < 0.05). Addition of Jesdianum extract significantly reduced the total viable count and psychrophilic bacteria compared to the control, subsequently extending the shelf-life of the product to over 42 days. Overall, Allium Jesdianum extract, with its antioxidant and antimicrobial properties, is beneficial in preserving sausage products and can be recommended as a nitrite substitute.

Boosting peroxymonosulfate activation with a composite of highly dispersed FeS2 nanoparticles anchored on N-doped biochar for efficient tetracycline degradation

The rational design of inexpensive peroxymonosulfate (PMS) activators with high efficiencies is still in high demand. Herein, a composite with highly dispersed FeS2 anchored on nitrogen-doped biochar (FeS2@NBC) was prepared via a hydrothermal process and used for PMS activation to degrade the pollutant tetracycline (TC). Benefiting from in situ growth of FeS2 on the NBC surface, FeS2@NBC alleviated the side effects caused by FeS2 agglomeration, and the synergistic catalytic effect of the FeS2 nanoparticles and N-doped biochar resulted in excellent performance. The optimal FeS2@NBC/PMS system could degrade 87.6% of TC within 10min, and it exhibited adaptability to pH changes and the presence of common inorganic anions. A comprehensive study involving radical scavenging experiments, electron paramagnetic resonance (EPR) spectroscopy, electrochemical tests and XPS analyses revealed that the singlet oxygen (1O2) and hydroxyl radical (•OH) were the dominant reactive oxygen species (ROS), the sulfate radical (SO4•−) and electron transfer were involved in the TC degradation process. Moreover, three degradation pathways were indicated by LC−MS detection, and the toxicities of the degradation intermediates were predicted and evaluated. Finally, FeS2@NBC showed excellent reusability and stability after five cycles of TC degradation. This work provides a reference for designing efficient catalysts that can be combined with metal sulfides and biochar for efficient PMS activation.

Theranostic antibacterial hydrogel based on biopolymers cross-linked and doped with phytic acid from rice bran for wound healing

Theranostic antibacterial wound dressing is highly recommended in practical applications. The conventional methods of integrating diagnostic and therapeutic functions have the disadvantages of complicated preparation, mutual interference, inability to effectively broad spectrum antibacterial property, and easy to induce drug-resistant bacteria. Herein, a pH and light-responsive theranostic antibacterial hydrogel is developed by biopolymers polyvinyl alcohol (PVA) and polyaniline (PANI), and cross-linking with phytic acid (PA), which is widely present in rice bran. The biological polymer-based conductive hydrogel enables timely diagnosis and photothermal sterilization in-situ for wound healing. Because PANI is highly sensitive to pH changes in the bacterial microenvironment, the hydrogel can detect bacterial infections at concentrations as low as 103 CFU/mL. Subsequently, PANI absorbs near-infrared light to achieve on-demand exothermic sterilization (under 808 nm irradiation for 20 min, the killing ratios for Staphylococcus aureus and Escherichia coli reached almost 100 %). In addition, the hydrogel can monitor the intensity of joint movement to avoid wound re-tearing sensitively. In vitro cytotoxicity and hemocompatibility experiments and in vivo full-thickness infected wound model indicate that the hydrogel has good biocompatibility, antibacterial ability, and can accelerate the wound healing effectively. This work will promote the development of wearable electronic devices and precision medicine.

The long-term leaching behavior of heavy metals in geopolymers and Portland cement bricks containing MSWI fly ash: a comparative study

Geopolymers was considered as an ideal alternative to cement solidification/stabilization for municipal solid waste incineration fly ash (MSWI FA). However, the long-term leaching behavior of heavy metals in geopolymers had attracted less attention. In this study, the long-term leaching behavior of heavy metals in geopolymers containing MSWI FA was investigated and compared with Portland cement bricks under various corrosion scenarios. The findings revealed a consistent trend of "slowly increasing - slowly decreasing - gradually stabilizing" in the pH changes in the effluent of all samples and the absence of corrosive risk in the utilization of geopolymers. The maximum pH values of the effluent were G2 (12.00) > G1 (11.90) > G3 (10.83) > C1 (9.67), suggesting that geopolymers were not corrosive in resource utilization. The long-term leaching behavior of heavy metals under different corrosion conditions could be divided into two stages, which included quick release in stage Ⅰ and gradual stabilization in stage Ⅱ. Compared with Portland cement bricks, the cumulative leaching concentration of heavy metals in geopolymers was lower, indicating less environmental risk. Due to the strongest corrosiveness from simulated acid rain (SAR), C2 and G2 exhibited significant compressive strength loss rates of 20.2% and 9.25%, respectively. In the leaching of CO2-saturated water (CSW), the leaching behavior of heavy metals was mainly regulated by the nucleation-dissolution trade-off of carbonates, however the dissolution mechanism of heavy metals in SAR could be summarized as follows: (1) corrosion/replacement of H+, and (2) counter-ion effect. this study will promote the resource utilization of MSWI FA. In a word, this work systematically studied the long-term environmental risk of geopolymers, which was beneficial to the resource utilization of MSWI FA.

Comprehensive Review on Polymers Used in Insitu Gelling System

Abstract: In situ gelling formulations are drug delivery systems which typically exist in a liquid form at room temperature and change into gel state after application to the body in response to various stimuli such as changes in temperature, pH and ionic composition.[1] In situ gels have become one of the most prominent and accessible systems. These systems have several advantages like simple manufacturing, easy to use, improved adherence, and patient comfort by minimizing drug administration frequency by its unique characteristic features of sol to gel transition. In the 'sol-gel' method, the precursor goes through hydrolysis and polymerization or condensation to produce a colloidal suspension or solution. As they can administer in solution form, these in situ gelling systems undergo gelation at the achievement site. Some researchers recently developed in situ gelling systems of liposomes, microspheres, nanoemulsions, nanospheres, etc. This review mainly focused on the introduction, advantages, disadvantages, types of polymers, and suitable characteristics for preparing in situ gels.

Screening of phosphate solubilizing Aspergillus spp. from soil samples

Phosphorus (P) is a naturally existing element crucial for plant growth among the 17 essential elements. It's integral to various biomolecules like nucleic acids, coenzymes, phosphoproteins, and phospholipids, playing key roles in cellular processes and structural integrity. Its presence is fundamental for sustaining healthy plant growth and ecosystem balance. Rhizosphere soil samples from medicinal plants at Shree Shivaji College Akola were collected aseptically. Phosphate Solubilizing Fungi (PSF) were isolated using Pikovskya’s agar medium, characterized microscopically, and screened for phosphate solubilization potentials. % Solubilization Efficiency was determined, and quantitative estimation of phosphate solubilization was conducted by ammonium molybdate method by using KH2PO4 as standard for determination. Fourteen Aspergillus spp. isolates from soil were screened for phosphate solubilization on PVK medium. Results showed varied solubilization indices and efficiencies across different time intervals, with pH changes observed during solubilization. Optical density measurements provided insights into concentration variations among isolates.

Phenylacetic acid, an anti-vaginitis metabolite produced by the vaginal symbiotic bacterium Chryseobacterium gleum

The human microbiome contains genetic information that regulates metabolic processes in response to host health and disease. While acidic vaginal pH is maintained in normal conditions, the pH level increases in infectious vaginitis. We propose that this change in the vaginal environment triggers the biosynthesis of anti-vaginitis metabolites. Gene expression levels of Chryseobacterium gleum, a vaginal symbiotic bacterium, were found to be affected by pH changes. The distinctive difference in the metabolic profiles between two C. gleum cultures incubated under acidic and neutral pH conditions was suggested to be an anti-vaginitis molecule, which was identified as phenylacetic acid (PAA) by spectroscopic data analysis. The antimicrobial activity of PAA was evaluated in vitro, showing greater toxicity toward Gardnerella vaginalis and Candida albicans, two major vaginal pathogens, relative to commensal Lactobacillus spp. The activation of myeloperoxidase, prostaglandin E2, and nuclear factor-κB, and the expression of cyclooxygenase-2 were reduced by an intravaginal administration of PAA in the vaginitis mouse model. In addition, PAA displayed the downregulation of mast cell activation. Therefore, PAA was suggested to be a messenger molecule that mediates interactions between the human microbiome and vaginal health.

Leaching and cytotoxicity of bismuth oxide in ProRoot MTA - A laboratory investigation.

The present study examined the leaching and cytotoxicity of bismuth from ProRoot MTA and aimed to identify whether bismuth leaching was affected by the cement base and the immersion regime used. The leaching profile of bismuth was examined from ProRoot MTA and compared with hydroxyapatite containing 20% bismuth oxide as well as hydroxyapatite and tricalcium silicate to investigate whether bismuth release changed depending on the cement base. Bismuth leaching was determined after 30 and 180 days of ageing immersed in Dulbecco's modified Eagle's medium (DMEM) using mass spectroscopy (ICP-MS). The media were either unchanged or regularly replenished. The pH, surface microstructure and phase changes of aged materials were assessed. Wistar rat femoral bone marrow stromal cells (BMSCs) and cutaneous fibroblasts were isolated, cultured and seeded for cell counting (trypan blue live/dead) after exposure to non-aged, 30- and 180-days-aged samples in regularly replenished DMEM. Aged DMEM in contact with materials was also used to culture BMSCs to investigate the effect of material leachates on the cells. Gene expression analysis was also carried out after direct exposure of cells to non-aged materials. Differences between groups were statistically tested at a significance level of 5%. All materials exhibited alterations after immersion in DMEM and this increased with longer exposure times. The bismuth leached from ProRoot MTA as detected by ICP-MS. Aged ProRoot MTA samples exhibited a black discolouration and surface calcium carbonate deposition. ProRoot MTA influenced cell counts after direct exposure and its 180-days leachates reduced BMSC viability. After direct BMSC contact with non-aged ProRoot MTA an upregulation of metallothionein (MT1 and MT2A) expression and down-regulation of collagen-1a (Col-1a) and bone sialoprotein (BSP) expression was identified. Bismuth leaching was observed throughout 180-days observation period from all materials containing bismuth oxide. This negatively influenced cell viability and gene expression associated with bismuth exposure. This is the first study to report that metallothionein gene expression was influenced by exposure to ProRoot MTA.

Dynamic Release from Acetalated Dextran Nanoparticles for Precision Therapy of Inflammation.

Polymer-based nanoparticles (NPs) that react to altered physiological characteristics have the potential to enhance the delivery of therapeutics to a specific area. These materials can utilize biochemical triggers, such as low pH, which is prone to happen locally in an inflammatory microenvironment due to increased cellular activity. This reduced pH is neutralized when inflammation subsides. For precise delivery of therapeutics to match this dynamic reaction, drug delivery systems (DDS) need to not only release the drug (ON) but also stop the release (OFF) autonomously. In this study, we use a systematic approach to optimize the composition of acetalated dextran (AcDex) NPs to start (ON) and stop (OFF) releasing model cargo, depending on local pH changes. By mixing ratios of AcDex polymers (mixed NPs), we achieved a highly sensitive material that was able to rapidly release cargo when going from pH 7.4 to pH 6.0. At the same time, the mix also offered a stable composition that enabled a rapid ON/OFF/ON/OFF switching within this narrow pH range in only 90 min. These mixed NPs were also sensitive to biological pH changes, with increased release in the presence of inflammatory cells compared to healthy cells. Such precise and controllable characteristics of a DDS position mixed NPs as a potential treatment platform to inhibit disease flare-ups, reducing both systemic and local side effects to offer a superior treatment option for inflammation compared to conventional systems.

Establishment of an artificial urine model in vitro and rat or pig model in vivo to evaluate urinary crystal adherence

The current study aimed to establish an experimental model in vitro and in vivo of urinary crystal deposition on the surface of ureteral stents, to evaluate the ability to prevent crystal adhesion. Non-treated ureteral stents were placed in artificial urine under various conditions in vitro. In vivo, ethylene glycol and hydroxyproline were administered orally to rats and pigs, and urinary crystals and urinary Ca were investigated by Inductively Coupled Plasma-Optical Emission Spectrometer. in vitro, during the 3- and 4-week immersion periods, more crystals adhered to the ureteral stent in artificial urine model 1 than the other artificial urine models (p < 0.01). Comparing the presence or absence of urea in the composition of the artificial urine, the artificial urine without urea showed less variability in pH change and more crystal adhesion (p < 0.05). Starting the experiment at pH 6.3 resulted in the highest amount of crystal adhesion to the ureteral stent (p < 0.05). In vivo, urinary crystals and urinary Ca increased in rat and pig experimental models. This experimental model in vitro and in vivo can be used to evaluate the ability to prevent crystal adhesion and deposition in the development of new ureteral stents to reduce ureteral stent-related side effects in patients.

Time-Separated Pulse Release-Activation of an Enzyme from Alginate-Polyethylenimine Hydrogels Using Electrochemically Generated Local pH Changes.

β-Glucosidase (EC 3.2.1.21) from sweet almond was encapsulated into pH-responsive alginate-polyethylenimine (alginate-PEI) hydrogel. Then, electrochemically controlled cyclic local pH changes resulting from ascorbate oxidation (acidification) and oxygen reduction (basification) were used for the pulsatile release of the enzyme from the composite hydrogel. Activation of the enzyme was controlled by the very same pH changes used for β-glucosidase release, separating these two processes in time. Importantly, the activity of the enzyme, which had not been released yet, was inhibited due to the buffering effect of PEI present in the gel. Thus, only a portion of the released enzyme was activated. Both enzymatic activity and release were monitored by confocal fluorescence microscopy and regular fluorescent spectroscopy. Namely, commercially available very little or nonfluorescent substrate 4-methylumbelliferyl-β-d-glucopyranoside was hydrolyzed by β-glucosidase to produce a highly fluorescent product 4-methylumbelliferone during the activation phase. At the same time, labeling of the enzyme with rhodamine B isothiocyanate was used for release observation. The proposed work represents an interesting smart release-activation system with potential applications in biomedical field.

Relationship between soil factors with Helicotylenchus pseudorobustus isolated from tomato fields in Limpopo Province, South Africa

Helicotylenchus pseudorobustus is one of the tomato fields' most important plant-parasitic nematodes. In this study, the soil was sampled in 2023. The identification and determination of nematodes was made in the Aquaculture Research Unit at the University of Limpopo. During the investigation of this nematode in the Tzaneen region, the properties of soils infected with this nematode, including pH and EC, were investigated. The population of H. pseudorobustus was counted in 100 grams of soil in each season, and soil characteristics were also analysed at the same time. The results in different seasons of the year showed that the range of pH changes during the year of investigation was between 5.2 and 6.6, and the range of EC changes was between 2.9 and 4.3 mS. A comparison of EC and pH changes with population changes showed that the population increased approximately in the months when soil salinity decreased. In addition, soil structure (71.9% sand, 8.0% silt, and 20.1% clay) didn't influence the H. pseudorobustus population. However, the results showed no significant relationship between soil factors and the population dynamic of H. pseudorobustus nematode throughout the year.

Investigation on the population dynamics of Helicotylenchus pseudorobustus and its relationship with soil factors in tomato fields

Tomato (Solanum lycopersicum L.) is one of the premier vegetables in the world and is widely cultivated globally. As it is a relatively short-duration crop with a high yield, it is economically attractive, and the area under cultivation is increasing. Plant-parasitic nematodes are some of the most important plant pathogens in tomato farms. Helicotylenchus pseudorobustus is one of the most important plant-parasitic nematodes in tomato fields. Therefore, understanding the population dynamics of H. pseudorobustus on the tomato field assists the farmer in managing them and having better yields. In this study, the soil was sampled in 2022. Identification and determination of nematodes were made in the Aquaculture Research Unit, University of Limpopo. The properties of soils infected with this nematode, including pH and EC, were investigated during the investigation of this nematode in the Dalmatia region. The population of H. pseudorobustus was counted in 100 grams of soil in each season, and soil characteristics were also analyzed at the same time. The results in different seasons of the year showed that the range of pH changes during the years of investigation was between 7.5 and 7.7, and the range of EC changes was between 1.3 and 2.0 dS/m. A comparison of EC and pH changes with population changes showed that the population increased approximately in the months when soil salinity decreased. In addition, as the pH increases, the population of H. pseudorobustus also increases. However, no significant relationship was found between the values of pH, EC, and changes in the population of H. pseudorobustus nematode throughout the year.

Quantifying Variability in Zebrafish Larvae Locomotor Behavior across Experimental Conditions: A Learning-Based Tracker

This study investigated the effects of environmental changes on zebrafish larval behavior, using single-factor and orthogonal experiments to assess locomotion during temperature and pH changes. In single-factor experiments, zebrafish larvae were exposed to variations in temperature (22 to 30 °C) and pH levels (6.0, 7.0, 9.0). The simultaneous temperature and pH changes were investigated by orthogonal tests. In both experiments, each zebrafish larva was recorded in three 5 min videos at different stages (before exposure, during short-term exposure (10 min), and after long-term exposure (60 min)). You Look Only Once (YOLOv5) and Deep Simple Online Real Time Tracking (DeepSORT) models were adopted to develop a zebrafish larva tracking system, and YOLOv5 was improved in two aspects of anchor clustering and network structure. The tracking accuracy of the tracking system for small targets effectively improved, reaching more than 98% MOTA (Multiple Object Tracking Accuracy). Principal Component Analysis (PCA) was employed to extract three behavioral features from 13 motion parameters, namely motion activity, edge behavior, and motion direction preference. Our findings reveal that lower temperatures and acidic conditions both led to a decrease in motion behavioral activity, and the former also increased edge behavior. Conversely, elevated temperatures and alkaline conditions had a muted impact on these behaviors. Interestingly, concurrent changes in temperature and pH significantly altered directional preference. Additionally, we observed that lower temperatures elicited distinct temporal behavioral patterns at a constant pH level. In summary, we recommend the precise control and explicit reporting of ambient temperature and pH in both breeding devices and experimental wells to minimize the environmental impact on zebrafish behavior and enhance experiment repeatability and reliability.

Insights into the Correlation between Microbial Community Succession and Pericarp Degradation during Pepper (Piper nigrum L.) Peeling Process via Retting

White pepper, used both as a seasoning in people’s daily diets and as a medicinal herb, is typically produced by removing the pericarp of green pepper through the retting process. However, the mechanism of the retting process for peeling remains unclear. Therefore, this study aimed to investigate the changes in physicochemical factors, microbial community succession effects, and metabolites of the pepper pericarp during the pepper peeling process. The findings indicated that pre-treatment involving physical friction before the retting process effectively reduced the production time of white pepper. During the retting process, the pectinase activity increased, leading to a decrease in the pectin content in the pepper pericarp. There was a significant correlation observed between the changes in pH, pectin content, and peeling rate and the Shannon diversity index of bacteria and fungi. Prevotella, Lactococcus, and Candida were the dominant microbial genera during the retting. The functional predictions suggested that the monosaccharides degraded from the pepper pericarp could have been utilized by microbes through sugar metabolism pathways. Metabolomic analysis showed that the metabolic pathways of carbohydrates and amino acids were the main pathways altered during the pepper peeling process. The verification experiment demonstrated that the degradation of pectin into galacturonic acid by polygalacturonase was identified as the key enzyme in shortening the pepper peeling time. The structure of the pepper pericarp collapsed after losing the support of pectin, as revealed by scanning electron microscopy. These results suggest that the decomposition of the pepper pericarp was driven by key microbiota. The succession of microbial communities was influenced by the metabolites of the pepper pericarp during retting. These findings provide new insights into the retting process and serve as an important reference for the industrial production of white pepper.

Harnessing endocytic pH gradients for cascaded formation of intracellular condensates to inhibit autophagy: A pathway to cancer therapy

Cancer cells rely on autophagy to degrade damaged organelles and survive in the harsh environment for progression and metastasis. Autophagy inhibition can improve the efficacy of anticancer therapy because many anticancer drugs can induce protective autophagy in cancer cells. However, current clinically available autophagy inhibitors are rare and have adverse effects with limited selectivity. This work develops an intracellular biomolecular condensate for autophagy inhibition to kill cancer without apparent side effects. A modularly designed amphiphilic peptide (PNP) can self-assemble to form toxic nanofibrous condensates successively from nanoparticles with the pH changes of the endocytic pathway. Mechanistic studies by CLSM and FRAP demonstrate that the PNP finally forms solid nanofibrous condensates in the lysosome after cell endocytosis. Bio-EM and cell transfection with adenovirus expressing mCherry-GFP-LC3B fusion protein (autophagy marker) experiments indicate the autophagy inhibition by PNP nanofibrous condensates. In vitro experiments show that PNP can significantly boost the activity of the clinical drug by 150-fold against drug-resistant lung cancer cells by inducing G2/M phase arrest of the cell cycle. Furthermore, PNPs demonstrate effective tumor targeting and permeability in vivo, inhibiting tumor growth and reducing the side effects of clinical chemotherapy drugs. Overall, this work provides a simple and feasible strategy for designing intracellular condensates to inhibit autophagy for cancer therapy.

Effect of nutrient reductions on dissolved oxygen and pH: a case study of Narragansett bay

To assess the consequences of nutrient reduction strategies on water quality under climate change, we investigated the long-term dynamics of dissolved oxygen (DO) and pH in Narragansett Bay (NB), a warming urbanized estuary in Rhode Island, where nitrogen loads have declined due to extensive wastewater treatment plant upgrades. We use 15 years (January 2005-December 2019) of measurements from the Narragansett Bay Fixed Site Monitoring network. Nutrient-enhanced phytoplankton growth can increase DO in the upper water column while subsequent respiration can reduce water column DO and enhance bottom water acidification, and vice-versa. We observed significant decreases in surface DO levels, concurrent with a significant increase in bottom DO, associated with the nitrogen load reduction. Surface DO decline was primarily attributed to reduced intensity of primary productivity, supported by a concurrent decrease in surface chlorophyll concentrations. Meanwhile, the influence of reduced organic matter respiration led to the increase of bottom DO levels by 9 µmol kg-1 (approximately 0.2 mg L-1 for typical summer temperature and salinity) over a 15-year period, which overcame the opposite influence of oxygen reduction from solubility decreases due to warming temperatures. In contrast, long-term changes in surface pH have not exhibited discernible trends beyond natural variability, likely due to the complex and sometimes opposing influences of biological activity and changing river flow conditions. We observed a slight increase in bottom pH, associated with the increase in DO in bottom water. Notably, future variations in freshwater discharge, particularly linked to extreme precipitation events, may further influence water carbonate chemistry and thereby impact pH dynamics. This study highlights the necessity of long-term time series measurements in helping understand the impacts of environmental management practices in improving water quality in coastal regions during a changing climate.

Nanoparticles of Zinc Oxides Mitigated N2O Emissions in Tea Plantation Soil

The excessive application of nitrogen in tea plantations leads to severe soil acidification and N2O emission boosting. To promote sustainable agriculture, nanoparticles (NPs) have emerged as alternative fertilizers, but their effects on soil nitrification and greenhouse gas emissions in tea plantations remain unclear. In this study, the effects of NP type (ZnO-NPs and Fe2O3-NPs) and dose (0, 1, 10, and 100 mg·kg⁻1) on soil N2O emissions were investigated via a lab incubation trial. Soil pH, ammonium, and nitrate changes were also monitored during the incubation period. The abundance of functional genes related to nitrification and denitrification processes was analyzed as well. The results showed that ZnO-NPs led to a decrease in N2O emissions. The reduction effect was stronger with increasing dose and resulted in a 33% reduction at an addition rate of 100 mg·kg−1. The cumulative N2O emissions had significantly positive correlations with NH4+-N and NO3−-N. ZnO-NP addition showed a significantly negative effect on Ammonia-Oxidizing Archaea (AOA) but a positive effect on Ammonia-Oxidizing Bacteria (AOB) gene abundance. In contrast, Fe2O3-NPs showed an insignificant impact on N2O emissions and soil N content, as well as nitrification–denitrification gene abundance, regardless of different doses. These results imply that the application of ZnO-NPs may inhibit nitrification through the retarding of AOA activity. This study provided us with a potential practice to reduce N2O emissions in tea plantations by applying ZnO-NPs, but the efficiency of this reduction needs further examination under ambient conditions before field application.

Naturally biocompatible melanin based iron-complex nanoparticles for pH-responsive magnetic resonance imaging

The sensitivity and diagnostic accuracy of magnetic resonance imaging mainly depend on the relaxation capacity of contrast agents (CAs) and their accumulated amount at the pathological region. Due to the better biocompatibility and high-spin capacity, Fe-complexes have been studied widely as an alternative to replace popular Gd-based CAs associated with potential biotoxicity. Compared with a variety of Fe complex-based CAs, such as small molecular, macrocyclic, multinuclear complexes, the form of nanoparticle exhibits outstanding longitudinal relaxation, but the clinical transformation was still limited by the inconspicuous difference of contrast between tumor and normal tissue. The enhanced effect of contrast is a positive relation as relaxation of CAs and their concentration in desired region. To specifically improve the amount of CAs accumulated in the tumor, pH-responsive polymer poly(2-ethyl-2-oxazoline) (PEOz) was modified on melanin, a ubiquitous natural pigment providing much active sites for chelating with Fe(III). The Fe(III)-Mel-PEOz we prepared could raise the tumor cell endocytosis efficiency via switching surface charge from anion to cation with the stimuli of the decreasing pH of tumor microenvironment. The change of pH has negligible effect on the r 1 of Fe(III)-Mel-PEOz, which is always maintained at around 1.0 mM−1s−1 at 0.5 T. Moreover, Fe(III)-Mel-PEOz exhibited low cytotoxicity, and satisfactory enhancement of positive contrast effect in vivo. The excellent biocompatibility and stable relaxation demonstrate the high potential of Fe(III)-Mel-PEOz in the diagnosis of tumor.