ACS Omega最新文献

Microsuspension polymerization was used to create multihollow polymer particles. First, a block copolymer of poly(2-(dimethylamino)ethyl methacrylate)-block-poly(methyl methacrylate-3-(trimethoxysilyl) propyl methacrylate) (PDMAEMA-b-P(MMA-MPS)) was synthesized by using a solution iodine transfer polymerization (solution ITP). This block copolymer was then used as a porogen in microsuspension polymerization of ethylene glycol dimethacrylate (EGDMA) and hydroxyethyl methacrylate (HEMA) to create multihollow structures of P(EGDMA-HEMA) particles. The polymerization process was smooth, achieving 99% monomer conversion within 24 h. Scanning electron microscopy (SEM) confirmed the multihollow structure, while surface area analysis (BET) showed well-defined porosity. Moreover, a positive charge might have been derived from the PDMAEMA segment, verifying that the particles contained the PDMAEMA-b-P(MMA-MPS) block copolymer. Dye adsorption studies in both water and oil confirmed that the particles successfully formed multihollow structures. Moreover, the multihollow P(EGDMA-HEMA) particles maintained over 80% adsorption efficiency even after being reused ten times. This procedure is both basic and versatile, offering an effective means to produce multihollow polymer particles utilizing block copolymers as porogens, making it highly promising for various applications.

Disrupted folate metabolism related to high synthetic folic acid (FA) intake is a matter of contention. FA and its metabolites play a critical role in DNA synthesis and methylation, and inadequate or imbalanced folate status is strongly associated with neural tube defects and other adverse health outcomes. We determined different folate forms using the LC/MS-MS method in maternal blood, cord blood, and breast milk of women (n = 50) following the National Iron-Folic Acid (FA) Supplementation Program. High concentrations of 5-formyltetrahydrofolate (5-formyl-THF) (range: 40.9–222.7 nmol/L) were observed throughout pregnancy, in cord serum, and breast milk. Levels of 5-formyl-THF rapidly increased (mean difference: 181.6 nmol/L) after 4–6 weeks of supplementation with 1 mg of FA/day and subsequently decreased (mean difference: 139.8 nmol/L) upon continuous supplementation at 400 μg of FA/day. The rapid increase in 5-formyl-THF following supplementation was higher (p < 0.001) in women with methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism. 5-methyl-THF (range: 11.4–56.8 nmol/L) and FA (range: 26.8–39.6 nmol/L) were detected only in breast milk. MTHFR 677CT/TT genotypes were associated with lower 5-methyl-THF (p < 0.001) and higher (p < 0.001) 5-formyl-THF in breast milk. At baseline, 48% had low (<340 nmol/L) RBC folate, but the concentrations continuously increased (p < 0.001) across pregnancy despite the different FA doses. The unusual observation of high 5-formyl-THF, the futile folate form, and its modulation with FA dose and genetic polymorphism merit further investigation to elucidate the population dynamics and possible physiological/clinical significance while questioning the utility of RBC folate as a biomarker of usable folate forms.

Surface-enhanced Raman scattering (SERS) pushes the boundaries of Raman spectroscopy as an analytical technique, allowing improved sensitivity and high discriminatory ability in analyte detection. Here, we introduce a SERS substrate using reduced graphene oxide aerogels as scaffolds. Reduced graphene oxide aerogels are hydrophobic, electrically conductive, and easily formable, providing a versatile platform for silver dendritic nanostructure growth via electrochemical deposition. We show that the electrochemical growth conditions (applied voltage, reduction time) have a significant effect on both the morphology and coverage of the silver nanostructures, which in turn have a strong effect on the SERS performance of the substrate. The importance of Ag dendrite morphology to the SERS substrate’s performance is also confirmed by finite-difference time-domain simulations. Under silver growth conditions of 10 V applied voltage at 10 Hz for 120 min, we obtained a limit of detection of 3.16 × 10^–5 ppm for thiram, which is lower than the testing requirements set by food and environmental regulatory agencies. Moreover, the substrates showed high silver coverage (85.6%), reproducibility (relative standard deviation ∼6% for substrates produced under the same conditions), and relative stability (∼20% change) of the obtained signal over one month. In view of their SERS capabilities and relative ease of preparation, we consider this new class of substrates a strong candidate for meeting detection and quantification challenges for a broad spectrum of analytes.

Remote ischemic postconditioning (RIPostC), administered after the onset of local ischemia, has been shown to have beneficial effects on neurological, vascular, and motor functions in animal models. However, the precise mechanisms and interactions underlying these functional improvements remain unclear. Our study aimed to determine whether RIPostC exerts protective effects on the neurovascular units (NVU) and to investigate whether this protection is mediated by hypoxia-inducible factor-1α (HIF-1α). We used left middle cerebral artery occlusion and reperfusion (MCAO/r) to induce ischemic stroke in rats and applied RIPostC. YC-1 was used to inhibit the activity of HIF-1α. Following the 12-day RIPostC treatment, MRI scans showed a significant reduction in infarct volume in the affected area, accompanied by an increase in HIF-1α protein levels and its downstream angiogenic factors in the ischemic zone. Additionally, RIPostC promoted angiogenesis in the ischemic penumbra, which, in turn, reduced neuronal loss and astrocyte activation. Behavioral assessments further indicated that RIPostC treatment partially restored the motor function in MCAO/r rats. However, the therapeutic effects of RIPostC were counteracted by the addition of YC-1, suggesting that the protective effects of RIPostC against NVU are mediated through HIF-1α. Overall, our research demonstrates that RIPostC is an effective rehabilitative intervention for protecting NVU in MCAO/r rats through the HIF-1α-mediated pathway.

Brazil plays an important role in coffee quality assessment since it is the top producer and exporter. New technologies must be developed to increase production and ensure product quality. Thus, this study presents an application of laser-assisted rapid evaporative ionization mass spectrometry (LA-REIMS) to fingerprint more than 800 Arabica coffee samples. These samples were divided into six sensory classes by professional tasters according to the Brazilian official classification. Machine learning algorithms were applied for a better understanding of complex fingerprints, and their performances were compared. Partial least-squares discriminant analysis (PLS-DA) was inferior in its predictive capability compared to support vector machines (SVM) and artificial neural networks (ANN), which achieved up to 100% accuracy. The high sensitivity to distinct sensory classes enabled a tentative identification of spectral signals, such as fatty acids, chlorogenic acids, and phospholipids, which are likely being related to these properties in Arabica coffee for the first time.

Menaquinone-7 (MK-7) plays a key role in bone and cardiovascular health, and it is often included in multivitamin supplements and functional foods. The aim of this study is the development and validation, according to ICH guidelines, of a fast, highly sensitive, and reliable reverse-phase HPLC-UV quantification of vitamin K₂ as MK-7 in a common biological matrix sample, such as fermentation broth medium from Bacillus subtilis, with the advantage of single-step extraction and short analysis time. MK-7 was successfully isolated from the fermentation broth and its interfering residues by thermo-acidic extraction using 5% H₂SO₄ and ethanol, without derivatization, and was retained using a C8 column. The isocratic elution and UV detection at 268 nm within a 3-min run time allowed quantification over a wide accuracy range of 0.10–18.00 μg/mL, with an LOQ value of 0.10 μg/mL and an LOD value of 0.03 μg/mL. The method was found to be precise, accurate, and reliable, with RSD% lower than 5% and recoveries varying between 96.0% and 108.9%. The proposed method unlocks the opportunity to be suitable for routine analysis in the screening of bacterial strains producing MK-7, as well as to be successfully employed in manufacturing processes in the nutraceutical and food industries where complex matrices are involved.

DNA is held together by hydrogen bonding between nucleobases (adenine-thymine, guanine-cytosine) and van der Waals interactions between adjacent base pairs’ π orbitals. Intercalating molecules with quasiplanar structures utilize van der Waals interactions to bind between DNA base pairs. Experimental studies have shown that Cryptolepine preferentially intercalates between nonalternating cytosine and guanine base pairs. However, an atomic-scale mechanism that can explain the selective intercalation is still missing. Using molecular dynamics and density functional theory, we demonstrate how Cryptolepine binds to DNA base pairs, rationalizing its selectivity by analyzing the intermolecular bonding strength predicted by Umbrella Sampling and Free Energy Perturbation calculations. Cryptolepine is stable in all DNA base conformations studied, and the binding is a combination of van der Waals interactions with the nucleobases surrounding its π system and hydrogen bonds with the DNA backbone and nucleobases. Our model predicts a preference for cytosine and guanine base pairs with a more prominent preference for alternating cytosine and guanine base pairs. These findings illustrate Cryptolepine’s binding mechanism to DNA and highlight the importance of hydrogen bonds and van der Waals interactions.

Covalent organic frameworks (COFs) with a two-dimensional (2D) topology have recently emerged as promising catalyst systems for the electrosynthesis of hydrogen peroxide (H₂O₂) from oxygen (O₂). However, designing 2D catalysts to achieve higher H₂O₂ selectivity presents a significant challenge because of the extensive layer stacking and the aggregated active sites located in the basal planes. It results in lower atom utilization, which requires attention. In this study, we present two functionally similar COFs: one with a 2D rhombus topology (2D@BT_TPA-COF) and another with a three-dimensional (3D) noninterpenetrated pts topology (3D@BT_TPA-COF). Both COFs were utilized for the 2e^– oxygen reduction reaction (2e^– ORR). Tunning the dimensionality from 2D to 3D resulted in an increase in H₂O₂ selectivity from approximately ∼56% to approximately ∼96% (at 0.4 V) and a rise in the turnover frequency (TOF) from 0.05 to 0.08 s^–1 at 0.3 V. Nonaggregated active site distribution over 3D topology, featuring higher active site exposure, provides better access to the O₂/electrolyte and facilitates electron transfer leading to higher 2e^– ORR activity and selectivity compared to the 2D counterpart.

Natural products represent a vital source of chemical entities for the development of anti-infective agents. Insects face constant threats from pathogens and have evolved diverse mechanisms of the infection response. Among various insect species, the chemical protection provided by Galleria mellonella eggs against microorganisms remains poorly understood. This study aimed to investigate whether G. mellonella produces chemical compounds that could serve as anti-infective agents against clinically important bacteria. Additionally, the study examined the effects of larval exposure to bacterial antigens from multidrug-resistant Staphylococcus aureus, Klebsiella pneumoniae, and Pseudomonas aeruginosaon the chemical composition, morphology, and anti-infective properties of the eggs. Larvae were challenged with antigens derived from multidrug-resistant Gram-positive and Gram-negative bacteria. Eggs from intragroup mating were collected and analyzed by using histological and physicochemical techniques, including field-emission gun scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Fourier-transform infrared spectroscopy. Antibacterial and antibiofilm activities of the egg extracts were assessed using broth microdilution and crystal violet assays, respectively. The volatile compound profile of the extracts was characterized by gas chromatography–mass spectrometry. This pioneering study demonstrates the broad-spectrum antibacterial activity of G. mellonella eggs against clinically relevant bacteria. Notably, the antibacterial efficacy of the mucous layer extract was significantly enhanced when larvae were exposed to Gram-positive bacterial antigens. Dotriacontane and tetracontane were identified as the predominant volatile compounds. These findings highlight G. mellonella eggs as a promising source of bioactive compounds and underscore the potential of long-chain hydrocarbons in the development of novel antibacterial agents.

Selenium (Se)-enriched soils in southern Anhui Province, eastern China, exhibit significantly elevated geochemical backgrounds of heavy metals (HMs). However, the enrichment characteristics and sources of these HMs require further elucidation. This study conducted comprehensive geochemical analyses on soils and underlying bedrocks to investigate the enrichment and sources of eight HMs including As, Cd, Cr, Cu, Mo, Pb, Zn, and Ni. The concentrations of HMs in Se-enriched soils generally exceed regional background values and even surpass risk screening thresholds in China, particularly for As, Cd, and Mo. Sequential extraction analysis reveals that As, Pb, and Cr in Se-enriched soils are predominantly associated with the residual fraction (>50%). In contrast, Cd is characterized by high bioavailability, with 29.85% found in the exchangeable fraction and 14.01% in the carbonates fraction. Pb isotope tracing indicates that the sources of Pb in soils derive from the weathering of underlying bedrocks (34.59%), coal combustion (34.21%), and vehicle exhaust (31.20%). Using the positive matrix factorization (PMF) model, four primary sources of HMs in these soils were identified: (1) mining and smelting activities associated with coal combustion (Cd, Cr, Zn); (2) weathering of the underlying bedrocks; (3) leaching from Mo-rich ores in bedrocks; and (4) traffic emissions and agricultural inputs. These findings establish a scientific basis for the effective utilization and management of Se-enriched soils.