Local incomplete combustion emissions define the PM2.5 oxidative potential in Northern India.

The oxidative potential (OP) of particulate matter (PM) is a major driver of PM-associated health effects. In India, the emission sources defining PM-OP, and their local/regional nature, are yet to be established. Here, to address this gap we determine the geographical origin, sources of PM, and its OP at five Indo-Gangetic Plain sites inside and outside Delhi. Our findings reveal that although uniformly high PM concentrations are recorded across the entire region, local emission sources and formation processes dominate PM pollution. Specifically, ammonium chloride, and organic aerosols (OA) from traffic exhaust, residential heating, and oxidation of unsaturated vapors from fossil fuels are the dominant PM sources inside Delhi. Ammonium sulfate and nitrate, and secondary OA from biomass burning vapors, are produced outside Delhi. Nevertheless, PM-OP is overwhelmingly driven by OA from incomplete combustion of biomass and fossil fuels, including traffic. These findings suggest that addressing local inefficient combustion processes can effectively mitigate PM health exposure in northern India.

Major source categories of PM2.5 oxidative potential in wintertime Beijing and surroundings based on online dithiothreitol-based field measurements.

Fine particulate matter (PM2.5) causes millions of premature deaths each year worldwide. Oxidative potential (OP) has been proposed as a better metric for aerosol health effects than PM2.5 mass concentration alone. In this study, we report for the first time online measurements of PM2.5 OP in wintertime Beijing and surroundings based on a dithiothreitol (DTT) assay. These measurements were combined with co-located PM chemical composition measurements to identify the main source categories of aerosol OP. In addition, we highlight the influence of two distinct pollution events on aerosol OP (spring festival celebrations including fireworks and a severe regional dust storm). Source apportionment coupled with multilinear regression revealed that primary PM and oxygenated organic aerosol (OOA) were both important sources of OP, accounting for 41 ± 12 % and 39 ± 10 % of the OPvDTT (OP normalized by the sampled air volume), respectively. The small remainder was attributed to fireworks and dust, mainly resulting from the two distinct pollution events. During the 3.5-day spring festival period, OPvDTT spiked to 4.9 nmol min-1 m-3 with slightly more contribution from OOA (42 ± 11 %) and less from primary PM (31 ± 15 %). During the dust storm, hourly-averaged PM2.5 peaked at a very high value of 548 µg m-3 due to the dominant presence of dust-laden particles (88 % of total PM2.5). In contrast, only mildly elevated OPvDTT values (up to 1.5 nmol min-1 m-3) were observed during this dust event. This observation indicates that variations in OPvDTT cannot be fully explained using PM2.5 alone; one must also consider the chemical composition of PM2.5 when studying aerosol health effects. Our study highlights the need for continued pollution control strategies to reduce primary PM emissions, and more in-depth investigations into the source origins of OOA, to minimize the health risks associated with PM exposure in Beijing.

Correction: Ocular biocompatibility evaluation of POSS nanomaterials for biomedical material applications.

[This corrects the article DOI: 10.1039/C5RA08668J.].

Variability in molecular composition and optical absorption of atmospheric brown carbon aerosols in two contrasting urban areas of China.

Atmospheric brown carbon (BrC) aerosols were investigated at two urban sites in southern (Hefei) and northern (Shijiazhuang) China during summer and winter of 2019-2020 to explore regional variability in their compositional and optical properties. Organic matter in ambient PM2.5 samples were characterized at molecular level using ultrahigh performance liquid chromatography coupled with a diode array detector and an Orbitrap mass spectrometer. Although the molecular composition of organic aerosols varied substantially over different ambient environments, they were mainly composed by CHO and CHON species in positive ionization mode while CHO and CHOS species in negative mode. The mass absorption coefficients of BrC aerosols at wavelength range 250-450 nm were relatively higher for winter samples in both cities and for Shijiazhuang samples in both seasons, partly attributed to the higher concentration levels of anthropogenic air pollutants in these environments. The absorption Ångström exponents further revealed that BrC aerosols in winter seasons and in Shijiazhuang had a greater capacity of absorption at shorter wavelengths. A total of 26 BrC species with strong absorption were unambiguously identified from different environments, which mainly consisted of CHO, CHON, and CHN species and had higher degrees of unsaturation and lower degrees of oxidation. The presence and abundance of these BrC species varied dynamically across the seasons and cities, with a greater number of species presented in the winter of Shijiazhuang. The BrC species together contributed 12-26 % in the total absorbance of light-absorbing organic components at 250-450 nm. This study highlights the regional differences in BrC properties influenced by the sources and atmospheric processes, which should be taken into account to assess their climate impacts.

Expression of Concern: Surface modification of intraocular lenses via photodynamic coating for safe and effective PCO prevention.

Expression of Concern for 'Surface modification of intraocular lenses via photodynamic coating for safe and effective PCO prevention' by Junmei Tang et al., J. Mater. Chem. B, 2021, 9, 1546-1556, https://doi.org/10.1039/D0TB02802A.

Photo-controllable drug releasing bulk polyacrylic intraocular lens material for safer posterior capsular opacification prevention.

Posterior capsular opacification (PCO) is the most common complication that occurs after intraocular lens (IOL) implantation in cataract therapy. In recent years, IOLs have been developed as drug delivery platforms, but concerns over the safety of uncontrolled proliferative drug release have arisen. Therefore, a controlled drug release strategy is needed for safer PCO prevention. In this study, a new monomer contained coumarin group was introduced in material preparation, and poly(ethylene glycol phenyl ether methacrylate-co-2-(2-ethoxyethoxy) ethyl acrylate-co-7-(2-methacryloyloxyethoxy)-4-methylcoumarin) (PEEC) acrylic IOL materials were synthesized. The antiproliferative drug 5-fluorouracil (5-FU) could be chemically grafted to the PEEC IOL materials easily via a light induced [2 + 2] cycloaddition reaction with the coumarin group, getting drug-loaded IOL (PEEC@5-FU IOL). The PEEC@5-FU IOL exhibited excellent optical and mechanical properties and biocompatibility. More importantly, the loaded 5-FU could be easily controlled from release by light irradiation via photo-dissociation of the cyclobutane ring that was obtained by the [2 + 2] cycloaddition reaction of 5-FU and coumarin. The in vitro and in vivo experiments demonstrated that such photo-controllable drug release IOL could effectively prevent PCO after implantation in a safe way.

Expression of concern: Synthesis of MA POSS-PMMA as an intraocular lens material with high light transmittance and good cytocompatibility.

Expression of concern for 'Synthesis of MA POSS-PMMA as an intraocular lens material with high light transmittance and good cytocompatibility' by Bailiang Wang et al., RSC Adv., 2014, 4, 52959-52966, https://doi.org/10.1039/C4RA08060B.

NIR-triggered thermosensitive polymer brush coating modified intraocular lens for smart prevention of posterior capsular opacification.

Posterior capsule opacification (PCO) is the most common complication after cataract surgery. Drug-eluting intraocular lens (IOLs) is a promising concept of PCO treatment in modern cataract surgery. However, the large dose of drugs in IOL leads to uncontrollable and unpredictable drug release, which inevitably brings risks of overtreatment and ocular toxicity. Herein, a low-power NIR-triggered thermosensitive IOL named IDG@P(NIPAM-co-AA)-IOL is proposed to improve security and prevent PCO by synergetic controlled drug therapy and simultaneous photo-therapy. Thermosensitive polymer brushes Poly(N-isopropylacrylamide-co-Acrylic acid) (P(NIPAM-co-AA)) is prepared on IOL via surface-initiated reversible addition-fragmentation chain transfer (SI-RAFT) polymerization. Then, Doxorubicin (DOX) and Indocyanine green (ICG) co-loaded Gelatin NPs (IDG NPs) are loaded in P(NIPAM-co-AA) by temperature control. The IDG NPs perform in suit photodynamic & photothermal therapy (PTT&PDT), and the produced heat also provides a trigger for controllable drug therapy with a cascade effect. Such functional IOL shows excellent synergistic drug-phototherapy effect and NIR-triggered drug release behavior. And there is no obvious PCO occurrence in IDG@P(NIPAM-co-AA) IOL under NIR irradiation compared with control group. This proposed IDG@P(NIPAM-co-AA)-IOL serves as a promising platform that combines phototherapy and drug-therapy to enhance the therapeutic potential and medication safety for future clinical application of PCO treatment.

Expression of concern: In vitro and in vivo evaluation of xanthan gum-succinic anhydride hydrogels for the ionic strength-sensitive release of antibacterial agents.

Expression of concern for 'In vitro and in vivo evaluation of xanthan gum-succinic anhydride hydrogels for the ionic strength-sensitive release of antibacterial agents' by Bailiang Wang et al., J. Mater. Chem. B, 2016, 4, 1853-1861, https://doi.org/10.1039/C5TB02046H.

Accounting for Cloud Nucleation Activation Mechanism of Secondary Organic Matter from α-Pinene Oxidation Using Experimentally Retrieved Water Solubility Distributions.

Activation of cloud droplets of aerosol particles from biogenic precursors plays a critical role in Earth's climate system. However, the molecular-level understanding of the cloud condensation nuclei (CCN) activation process for secondary organic matter (SOM) is still lacking. Here, we reduced the gap by segregating SOM from α-pinene based on water solubility. The chemical composition and CCN activity of the solubility-segregated fractions of SOM were measured. The results demonstrated for the first time by laboratory experiment that highly oxygenated compounds such as hydroperoxides and highly oxygenated organic molecules are important contributors for the CCN activity of α-pinene SOM. Meanwhile, relatively less water-soluble species were also abundant. Analysis based on the Köhler theory demonstrated that less water-soluble compounds in SOM remain undissolved during the cloud activation process, suggesting that the traditional single-parameter parameterization for CCN activation would not be sufficient for representing the process. In combination with the recent developments in SOM formation chemistry, the present study helps in understanding the interactions between the biosphere and climate.

Enhanced Production of Organosulfur Species during a Severe Winter Haze Episode in the Guanzhong Basin of Northwest China.

The molecular composition of organic aerosols in ambient PM2.5 was investigated in an urban area in the Guanzhong basin of northwest China during a severe regional haze episode in the winter of 2018/2019. Organic matter, accounting for 20-35% of PM2.5 mass concentration, was characterized using direct infusion and electrospray ionization coupled with high-resolution Orbitrap mass spectrometry. The number of organic molecular formula assignments was primarily dominated by organosulfur species (OrgS, including CHOS and CHONS) in negative ion mode. The number and peak signal intensity of OrgS distinctly increased during the severe haze episode. Organosulfates and nitrooxy-organosulfates constituted the majority number (72-94%) of OrgS over the entire period. Although the OrgS were mostly present in aliphatic molecular structures, an increase in the number of polycyclic aromatic OrgS on haze days revealed the enhanced contribution from anthropogenic sources. The number of OrgS strongly correlated with ambient relative humidity and the oxidation ratios of sulfur and nitrogen, suggesting the important roles of aqueous phase chemistry and atmospheric oxidation in the formation of OrgS. A thorough understanding of the significance of OrgS will be essential to assess and mitigate the adverse impacts of haze pollution.

Cascade reaction triggering and photothermal AuNPs@MIL MOFs doped intraocular lens for enhanced posterior capsular opacification prevention.

Posterior capsular opacification (PCO) is the most common complication after cataract surgery. Present strategies can't meet the clinical needs of long-term prevention. This research reports a novel intraocular lens (IOL) bulk material with high biocompatibility and synergistic therapy. Gold nanoparticles (AuNPs) doped MIL-101-NH2 metal-organic frameworks (MOFs) (AuNPs@MIL) was firstly fabricated via in situ reductions. Then the functionalized MOFs were uniformly mixed with glycidyl methacrylate (GMA) and 2-(2-ethoxyethoxy) ethyl acrylate (EA) to form the nanoparticle doped polymer (AuNPs@MIL-PGE), and which was used to fabricate IOL bulk materials. The materials' optical and mechanical properties with different mass contents of nanoparticles are investigated. Such bulk functionalized IOL material could efficiently remove residual human lens epithelial cells (HLECs) in the capsular bag in the short term, and can prevent PCO on demand in the long run by near-infrared illumination (NIR) action. In vivo and in vitro experiments demonstrate the biosafety of the material. The AuNPs@MIL-PGE exhibits excellent photothermal effects, which could inhibit cell proliferation under NIR and doesn't cause pathological effects on the surrounding tissues. Such functionalized IOL can not only avoid the side effects of the antiproliferative drugs but also realize the enhanced PCO prevention in clinical practice.

Non-viral gene coating modified IOL delivering PDGFR-α shRNA interferes with the fibrogenic process to prevent posterior capsular opacification.

Posterior capsule opacification (PCO), the most common complication after cataract surgery, is caused by the proliferation, migration and epithelial-mesenchymal transition (EMT) of residual lens epithelial cells in the capsule bag. Although the surface modification and drug loading of intraocular lens (IOLs) have been effective in preventing PCO to some extent, the intraocular safety of anti-proliferative drug application is still a major limitation in clinical application. In this study, we used non-viral gene delivery systems in combination with layer-by-layer (LBL) self-assembly technology, and the modified IOL could effectively prevent the development of PCO by interfering with the EMT process mediated by the platelet-derived growth factor receptor-α (PDGFR-α). Herein, the gene fragments were wrapped by electrostatic conjugation using polyethyleneimine-graft-poly(ethylene glycol) to form gene complexes. Gene complexes were characterized by dynamic light scattering, transmission electron microscopy (TEM) and agarose gel electrophoresis, and evaluated for storage and serum stability. The layer assembly behavior of the IOL surface, changes in optical properties and the release behavior of the gene complexes were characterized using quartz crystal microbalance, UV-vis, contact angle and TEM. In vitro experiments showed that the IOL coating has good bio-compatibility and can achieve the corresponding transfection effect, and the released gene complexes exhibited excellent cell internalization and lysosomal escape behaviors, as well as effective inhibition of PDGFR-α expression and its mediated EMT process. The early PCO prevention effect and bio-compatibility evaluation of the modified IOL in vivo were evaluated by implantation into animal eyes. This study provides a new strategy for the development of surface modifications of small nucleic acid drugs and non-toxic EMT interference therapies for PCO.

Transcriptome-phenotype matching analysis of how nitrogen sources influence Lacticaseibacillus rhamnosus tolerance to heat stress and oxidative stress.

BACKGROUND: Spray drying is the most cost-effective production method for lactic acid bacteria starters, but heat and oxidative stresses result in low survival rates. The heat stress and oxidative stress tolerance of Lacticaseibacillus rhamnosus cultured in tryptone-free MRS (NP-MRS) broth was much stronger than that in MRS or tryptone-free MRS broth supplemented with phenylalanine (Phe-MRS). Here, multiple transcriptome-phenotype matching was performed on cells cultured in NP-MRS, MRS and Phe-MRS broths to reveal the mechanism by which nitrogen sources influence L. rhamnosus tolerance to heat stress and oxidative stress. RESULTS: Compared with cells cultured in NP-MRS broth, 83 overlapping differentially expressed genes (DEGs) were downregulated by either tryptone or phenylalanine. The overlapping DEGs were mainly classified into carbohydrate metabolism and membrane transport pathways, which are often repressed by glucose during carbon catabolite repression (CCR). In the presence of glucose, the heat stress or oxidative stress tolerance of L. rhamnosus hsryfm 1301 was not strengthened by supplementation with secondary carbohydrates. Replacing glucose with mannose, fructose or ribose improved the heat stress and oxidative stress tolerance of L. rhamnosus hsryfm 1301 (5 to 46-fold). CONCLUSIONS: Alleviation of CCR might be a reason for the resistance of L. rhamnosus hsryfm 1301 to heat stress and oxidative stress in a low-nitrogen environment. The survival rate of L. rhamnosus during spray drying will hopefully be improved by relieving CCR. It is a new discovery that nitrogen sources influence CCR in L. rhamnosus.

Correction: Design of foldable, responsively drug-eluting polyacrylic intraocular lens bulk materials for prevention of postoperative complications.

Correction for 'Design of foldable, responsively drug-eluting polyacrylic intraocular lens bulk materials for prevention of postoperative complications' by Yueze Hong et al., J. Mater. Chem. B, 2022, DOI: https://doi.org/10.1039/d2tb01974d.

Design of foldable, responsively drug-eluting polyacrylic intraocular lens bulk materials for prevention of postoperative complications.

Posterior capsular opacification (PCO), resulting from undesired intracapsular cell proliferation, is the most common complication of intraocular lens (IOL) implantation after cataract surgery. In recent years, IOLs have been developed into a drug delivery platform. Compared with traditional eye drops, drug-loaded IOLs have the characteristics of independent patient compliance and no other operation except surgical implantation. In this work, a series of poly(glycidyl methacrylate-co-2-(2-ethoxyethoxy)ethyl acrylate) (PGE) acrylic intraocular lens materials were synthesized as drug delivery platforms. The PGE synthesized with 10% crosslinking agent has excellent optical, foldable, and thermomechanical properties. An aldehyde group was subsequently introduced into the PGE chains, and an antiproliferative drug (doxorubicin) was immobilized onto the PGE chains via an H+-sensitive imine bond. The IOL exhibits H+-dependent Dox release behavior in a simulated pathological environment. The in vitro and in vivo systematical evaluations indicate that such a responsively drug-eluting PGE IOL can effectively prevent PCO.

Influence of nitrogen sources on the tolerance of Lacticaseibacillus rhamnosus to heat stress and oxidative stress.

It has been found that 32 genes related to nitrogen source metabolism in Lacticaseibacillus rhamnosus are downregulated under both heat stress and oxidative stress. In this study, the influence of different nitrogen sources within the growth medium on the tolerance of L. rhamnosus to heat stress and oxidative stress was investigated. Tryptone-free MRS was found to enhance the tolerance of L. rhamnosus hsryfm 1301 to heat stress and oxidative stress during the whole growth period, and this result was universal for all L. rhamnosus species analyzed. The strongest strengthening effect occurred when the OD600 value reached 2.0, at which the survival rates under heat stress and oxidative stress increased 130-fold and 40-fold, respectively. After supplementing phenylalanine, isoleucine, glutamate, valine, histidine, or tryptophan into the tryptone-free MRS, the tolerance of L. rhamnosus to heat stress and oxidative stress exhibited a sharp drop. The spray drying survival rate of L. rhamnosus hsryfm 1301 cultured in the tryptone-free MRS rose to 75% (from 30%), and the spray dried powder also performed better in the experimentally simulated gastrointestinal digestion. These results showed that decreasing the intake of amino acids is an important mechanism for L. rhamnosus to tolerate heat stress and oxidative stress. When L. rhamnosus is cultured for spray drying, the concentration of the nitrogen source's components should be an important consideration.

Seasonal Distribution of Atmospheric Coarse and Fine Particulate Matter in a Medium-Sized City of Northern China.

Atmospheric particulate matter (PM) was measured continuously at an urban site in Baoji city in northern China in 2018 to investigate the seasonal distribution characteristics. Coarse PM (PM2.5-10) was more prevalent in spring, substantially due to the regional transport of dust. High loadings of coarse PM were found at night compared to daytime, which could result from high production and unfavorable dispersion conditions. Fine PM (PM2.5) constituted, on average, 54% of the total PM mass concentration, whereas it contributed more than 97% of the total PM number concentration. The number and mass concentrations of fine PM increased substantially in the winter, which was possibly due to the enhanced production of atmospheric secondary processes and coal combustion. Precursor gaseous pollutants and meteorology greatly influenced the PM distributions. Fine PM was associated more strongly with gas pollutants than coarse PM, which suggested that it largely originated from secondary production and combustion sources. High relative humidity appeared to promote the production of fine PM, whereas it facilitated the removal of coarse PM. This study highlights that different air-pollution control strategies should be used for coarse and fine PM according to the distribution characteristics and influencing factors in similar medium-sized urban areas.