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1.
Small ; 20(23): e2309180, 2024 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-38148304

RESUMEN

Stroke is the second leading cause of death worldwide, and hypoxia is a major crisis of the brain after stroke. Therefore, providing oxygen to the brain microenvironment can effectively protect neurons from damage caused by cerebral hypoxia. However, there is a lack of timely and effective means of oxygen delivery clinically to the brain for acute cerebral hypoxia. Here, a phase-change based nano oxygen carrier is reported, which can undergo a phase change in response to increasing temperature in the brain, leading to oxygen release. The nano oxygen carrier demonstrate intracerebral oxygen delivery capacity and is able to release oxygen in the hypoxic and inflammatory region of the brain. In the acute ischemic stroke mouse model, the nano oxygen carrier can effectively reduce the area of cerebral infarction and decrease the level of inflammation triggered by cerebral hypoxia. By taking advantage of the increase in temperature during cerebral hypoxia, phase-change oxygen carrier proposes a new intracerebral oxygen delivery strategy for reducing acute cerebral hypoxia.


Asunto(s)
Oxígeno , Animales , Oxígeno/química , Oxígeno/metabolismo , Ratones , Hipoxia Encefálica/metabolismo , Masculino , Encéfalo/metabolismo , Encéfalo/patología , Modelos Animales de Enfermedad , Transición de Fase
2.
Small ; 20(23): e2307669, 2024 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-38168885

RESUMEN

The unique anionic redox mechanism provides, high-capacity, irreversible oxygen release and voltage/capacity degradation to Li-rich cathode materials (LRO, Li1.2Mn0.54Co0.13Ni0.13O2). In this study, an integrated stabilized carbon-rock salt/spinel composite heterostructured layers (C@spinel/MO) is constructed by in situ self-reconstruction, and the generation mechanism of the in situ reconstructed surface is elucidated. The formation of atomic-level connections between the surface-protected phase and bulk-layered phase contributes to electrochemical performance. The best-performing sample shows a high increase (63%) of capacity retention compared to that of the pristine sample after 100 cycles at 1C, with an 86.7% reduction in surface oxygen release shown by differential electrochemical mass spectrometry. Soft X-ray results show that Co3+ and Mn4+ are mainly reduce in the carbothermal reduction reaction and participate in the formation of the spinel/MO rock-salt phase. The results of oxygen release characterized by Differential electrochemical mass spectrometry (DEMS) strongly prove the effectiveness of surface reconstruction.

3.
Small ; 20(35): e2400827, 2024 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-38660701

RESUMEN

The first example of a material capable of spatiotemporal catch and release of singlet oxygen (1O2) in gel phase is presented. Several low molecular weight organogelators based around an oxotriphenylhexanoate (OTHO) core are developed and optimized with regard to; their gelation properties, and ability of releasing 1O2 upon thermal and/or photochemical external stimuli, in both gel phase and solution. Remarkably, reversible phase transitioning between the gel and solution phase are also demonstrated. Taken together two complementary modes of releasing 1O2, one thermally controlled over time, and one rapid release by means of photochemical stimuli is disclosed. These findings represent the first phase reversible system where function and aggregation properties can be controlled independently, and thus pave the way for novel applications in material sciences as well as in life sciences.

4.
Nano Lett ; 22(20): 8372-8380, 2022 Oct 26.
Artículo en Inglés | MEDLINE | ID: mdl-36149367

RESUMEN

LiCoO2 has suffered from poor stability under high voltage as a result of insufficient Co-O bonding that causes lattice oxygen release and lattice distortions. Herein, we fabricated a high-voltage LiCoO2 at 4.6 V by doping with Ni/Mn atoms, which are obtained from spent LiNi0.5Mn0.3Co0.2O2 cathode materials. The as-prepared high-voltage LiCoO2 with Ni/Mn substitutional dopants in the Co layer enhances Co-O bonding that suppresses oxygen release and harmful phase transformation during delithiation, thus stabilizing the layered structure and leading to a superior electrochemical performance at 4.6 V. The pouch cell of modified LiCoO2 exhibits a capacity retention of 85.1% over 100 cycles at 4.5 V (vs graphite). We found that our strategy is applicable for degraded LiCoO2, and the regenerated LiCoO2 using this strategy exhibits excellent capacity retention (84.1%, 100 cycles) at 4.6 V. Our strategy paves the way for the direct conversion of spent batteries into high-energy-density batteries.

5.
Photosynth Res ; 151(3): 205-211, 2022 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-34558039

RESUMEN

This paper is a tribute to a great scientist and an authentic "honest man" that was Jean Lavorel (1928-2021). He was a pioneer in research on the primary events of photosynthesis in algae, plants, and photosynthetic bacteria. He focused his attention on chlorophyll fluorescence and luminescence, and also on oxygen evolution, both experimentally (with laboratory-built refined apparatus) and theoretically. Many of his results are classical now. Besides a survey of his main achievements, most of them obtained by him alone, different reminiscences on the researcher and the person he was illustrate the rich personality of Jean Lavorel.


Asunto(s)
Fotosíntesis , Plantas , Clorofila , Historia del Siglo XXI , Humanos , Oxígeno
6.
Int J Mol Sci ; 23(15)2022 Aug 06.
Artículo en Inglés | MEDLINE | ID: mdl-35955898

RESUMEN

Myoglobin (Mb), besides its roles as an oxygen (O2) carrier/storage protein and nitric oxide NO scavenger/producer, may participate in lipid trafficking and metabolite binding. Our recent findings have shown that O2 is released from oxy-Mb upon interaction with lactate (LAC, anerobic glycolysis end-product). Since pyruvate (PYR) is structurally similar and metabolically related to LAC, we investigated the effects of PYR (aerobic glycolysis end-product) on Mb using isothermal titration calorimetry, circular dichroism, and O2-kinetic studies to evaluate PYR affinity toward Mb and to compare the effects of PYR and LAC on O2 release kinetics of oxy-Mb. Similar to LAC, PYR interacts with both oxy- and deoxy-Mb with a 1:1 stoichiometry. Time-resolved circular dichroism spectra revealed that there are no major conformational changes in the secondary structures of oxy- or deoxy-Mb during interactions with PYR or LAC. However, we found contrasting results with respect to binding affinities and substrate preference, where PYR has higher affinity toward deoxy-Mb when compared with LAC (which prefers oxy-Mb). Furthermore, PYR interaction with oxy-Mb releases a significantly lower amount of O2 than LAC. Taken together, our findings support the hypothesis that glycolytic end-products play a distinctive role in the Mb-rich tissues by serving as novel regulators of O2 availability, and/or by impacting other activities related to oxy-/deoxy-Mb toggling in resting vs. exercised or metabolically activated conditions.


Asunto(s)
Mioglobina , Oxígeno , Cinética , Mioglobina/química , Oxígeno/metabolismo , Ácido Pirúvico , Relación Estructura-Actividad , Termodinámica
7.
Int J Mol Sci ; 23(9)2022 Apr 26.
Artículo en Inglés | MEDLINE | ID: mdl-35563138

RESUMEN

Myoglobin (Mb)-mediated oxygen (O2) delivery and dissolved O2 in the cytosol are two major sources that support oxidative phosphorylation. During intense exercise, lactate (LAC) production is elevated in skeletal muscles as a consequence of insufficient intracellular O2 supply. The latter results in diminished mitochondrial oxidative metabolism and an increased reliance on nonoxidative pathways to generate ATP. Whether or not metabolites from these pathways impact Mb-O2 associations remains to be established. In the present study, we employed isothermal titration calorimetry, O2 kinetic studies, and UV-Vis spectroscopy to evaluate the LAC affinity toward Mb (oxy- and deoxy-Mb) and the effect of LAC on O2 release from oxy-Mb in varying pH conditions (pH 6.0-7.0). Our results show that LAC avidly binds to both oxy- and deoxy-Mb (only at acidic pH for the latter). Similarly, in the presence of LAC, increased release of O2 from oxy-Mb was detected. This suggests that with LAC binding to Mb, the structural conformation of the protein (near the heme center) might be altered, which concomitantly triggers the release of O2. Taken together, these novel findings support a mechanism where LAC acts as a regulator of O2 management in Mb-rich tissues and/or influences the putative signaling roles for oxy- and deoxy-Mb, especially under conditions of LAC accumulation and lactic acidosis.


Asunto(s)
Mioglobina , Oxígeno , Cinética , Ácido Láctico , Mioglobina/química , Oxígeno/metabolismo , Consumo de Oxígeno/fisiología , Análisis Espectral , Termodinámica
8.
Int J Mol Sci ; 23(12)2022 Jun 20.
Artículo en Inglés | MEDLINE | ID: mdl-35743287

RESUMEN

Oxygen-generating materials have been used in several tissue engineering applications; however, their application as in situ oxygen supply within bioprinted constructs has not been deeply studied. In this study, two oxygen-generating materials, sodium percarbonate (SPO) and calcium peroxide (CPO), were studied for their oxygen release kinetics under a 0.1% O2 condition. In addition, a novel cell-culture-insert setup was used to evaluate the effects of SPO and CPO on the viability of skeletal muscle cells under the same hypoxic condition. Results showed that SPO had a burst oxygen release, while CPO had a more stable oxygen release than SPO. Both SPO and CPO reduced cell viability when used alone. The addition of catalase in SPO and CPO increased the oxygen release rate, as well as improving the viability of skeletal muscle cells; however, CPO still showed cytotoxicity with catalase. Additionally, the utilization of 1 mg/mL SPO and 20 U catalase in a hydrogel for bioprinting significantly enhanced the cell viability under the hypoxic condition. Moreover, bioprinted muscle constructs could further differentiate into elongated myotubes when transferring back to the normoxic condition. This work provides an excellent in vitro model to test oxygen-generating materials and further discover their applications in bioprinting, where they represent promising avenues to overcome the challenge of oxygen shortage in bioprinted constructs before their complete vascularization.


Asunto(s)
Bioimpresión , Ingeniería de Tejidos , Carbonatos , Catalasa , Humanos , Hipoxia , Cinética , Oxígeno , Peróxidos , Impresión Tridimensional , Ingeniería de Tejidos/métodos , Andamios del Tejido
9.
Angew Chem Int Ed Engl ; 60(52): 27102-27112, 2021 Dec 20.
Artículo en Inglés | MEDLINE | ID: mdl-34668282

RESUMEN

High-voltage LiCoO2 delivers a high capacity but sharp fading is a critical issue, and the capacity decay mechanism is also poorly understood. Herein, we clarify that the escape of surface oxygen and Li-insulator Co3 O4 formation are the main causes for the capacity fading of 4.6 V LiCoO2 . We propose the inhibition of the oxygen escape for achieving stable 4.6 V LiCoO2 by tailoring the Co3d and O2p band center and enlarging their band gap with MgF2 doping. This enhances the ionicity of the Co-O bond and the redox activity of Co and improves cation migration reversibility. The inhibition of oxygen escape suppresses the formation of Li-insulator Co3 O4 and maintains the surface structure integrity. Mg acts as a pillar, providing a stable and enlarged channel for fast Li+ intercalation/extraction. The modulated LiCoO2 shows almost zero strain and achieves a record capacity retention at 4.6 V: 92 % after 100 cycles at 1C and 86.4 % after 1000 cycles at 5C.

10.
Mol Pharm ; 16(8): 3703-3710, 2019 08 05.
Artículo en Inglés | MEDLINE | ID: mdl-31276423

RESUMEN

Photodynamic therapy (PDT) utilizing light-induced singlet oxygen has achieved attractive results in anticancer fields; however, its development is hindered by limited light penetration depth, skin phototoxicity, tumor hypoxia, and PDT-induced hypoxia. Inspired by our previous research work and the limitations of PDT, we introduce a small-molecule-targeted drug erlotinib into the singlet-oxygen chemical source endoperoxide to achieve an EGFR-targeted PDT-mimetic sensitizer (Y3-1) for anticancer therapy. We demonstrated the erlotinib-based precise delivery of the singlet-oxygen chemical source (in vitro photosensitization) to EFGR-overexpressing tumor cells and tissues. Moreover, the anticancer assays validated that the enhanced anticancer efficacy (in vitro and in vivo) of Y3-1 was due to reversible singlet-oxygen thermal release. This study is expected to provide a smart strategy to break through the current roadblock in targeted PDT and achieve a more efficient anticancer therapy model.


Asunto(s)
Portadores de Fármacos/farmacología , Neoplasias/tratamiento farmacológico , Fotoquimioterapia/métodos , Fármacos Fotosensibilizantes/administración & dosificación , Oxígeno Singlete/administración & dosificación , Animales , Línea Celular Tumoral/trasplante , Preparaciones de Acción Retardada/administración & dosificación , Preparaciones de Acción Retardada/farmacocinética , Modelos Animales de Enfermedad , Ensayos de Selección de Medicamentos Antitumorales , Receptores ErbB/antagonistas & inhibidores , Receptores ErbB/metabolismo , Clorhidrato de Erlotinib/farmacología , Femenino , Humanos , Inyecciones Intravenosas , Ratones , Neoplasias/patología , Fármacos Fotosensibilizantes/farmacocinética , Oxígeno Singlete/farmacocinética
11.
Nano Lett ; 18(5): 3241-3249, 2018 05 09.
Artículo en Inglés | MEDLINE | ID: mdl-29667835

RESUMEN

Chemical and mechanical properties interplay on the nanometric scale and collectively govern the functionalities of battery materials. Understanding the relationship between the two can inform the design of battery materials with optimal chemomechanical properties for long-life lithium batteries. Herein, we report a mechanism of nanoscale mechanical breakdown in layered oxide cathode materials, originating from oxygen release at high states of charge under thermal abuse conditions. We observe that the mechanical breakdown of charged Li1- xNi0.4Mn0.4Co0.2O2 materials proceeds via a two-step pathway involving intergranular and intragranular crack formation. Owing to the oxygen release, sporadic phase transformations from the layered structure to the spinel and/or rocksalt structures introduce local stress, which initiates microcracks along grain boundaries and ultimately leads to the detachment of primary particles, i.e., intergranular crack formation. Furthermore, intragranular cracks (pores and exfoliations) form, likely due to the accumulation of oxygen vacancies and continuous phase transformations at the surfaces of primary particles. Finally, finite element modeling confirms our experimental observation that the crack formation is attributable to the formation of oxygen vacancies, oxygen release, and phase transformations. This study is designed to directly observe the chemomechanical behavior of layered oxide cathode materials and provides a chemical basis for strengthening primary and secondary particles by stabilizing the oxygen anions in the lattice.

12.
J Environ Manage ; 246: 157-163, 2019 Sep 15.
Artículo en Inglés | MEDLINE | ID: mdl-31176180

RESUMEN

The radial oxygen loss (ROL) of wetland plants is a crucial factor that can influence the efficiency required for nitrogen (N) removal and microbial activities responsible for N removal in constructed wetlands (CWs). However, the shift of microbial community in different niches in response to ROL has been rarely studied. This study aims to unravel the link between the ROL and microbial response in sediment, water and rhizoplane by a surface flow CW planted with Myriophyllum aquaticum for treating high-strength swine wastewater. Ti3+-citrate colorimetric method demonstrated that M. aquaticum was a wetland species with a ROL of 0.019 mg/h/plant. Using quantitative polymerase chain reactions (qPCR) and high-throughput sequencing of microbial 16S rRNA gene, we demonstrated that the abundance of facultative anaerobic denitrifiers in the rhizoplane was the most of the three niches, that in the water (5-10 cm) was the less and that in the sediment was the least. Acinetobacter was enriched and dominated amongst denitrifiers in the water. Denitrifiers in the rhizoplane were mainly dominated by enriched Pseudomonas, Aeromonas, and Acinetobacter. The theoretical calculation of oxygen sources and consumptions indicated that water reaeration should support the oxygen demands for nitrification in the aerobic layer (0-5 cm), and the ROL could stimulate the growth of facultative anaerobic denitrifiers in the rhizoplane and water (5-10 cm) to achieve denitrification within CW systems.


Asunto(s)
Oxígeno , Humedales , Anaerobiosis , Animales , Desnitrificación , Nitrógeno , ARN Ribosómico 16S , Porcinos , Aguas Residuales
13.
Proc Natl Acad Sci U S A ; 112(45): E6139-47, 2015 Nov 10.
Artículo en Inglés | MEDLINE | ID: mdl-26508637

RESUMEN

Photosynthetic water oxidation is catalyzed by the Mn4CaO5 cluster of photosystem II. Recent studies implicate an oxo bridge atom, O5, of the Mn4CaO5 cluster, as the "slowly exchanging" substrate water molecule. The D1-V185N mutant is in close vicinity of O5 and known to extend the lag phase and retard the O2 release phase (slow phase) in this critical last [Formula: see text] transition of water oxidation. The pH dependence, hydrogen/deuterium (H/D) isotope effect, and temperature dependence on the O2 release kinetics for this mutant were studied using time-resolved O2 polarography, and comparisons were made with WT and two mutants of the putative proton gate D1-D61. Both kinetic phases in V185N are independent of pH and buffer concentration and have weaker H/D kinetic isotope effects. Each phase is characterized by a parallel or even lower activation enthalpy but a less favorable activation entropy than the WT. The results indicate new rate-determining steps for both phases. It is concluded that the lag does not represent inhibition of proton release but rather, slowing of a previously unrecognized kinetic phase involving a structural rearrangement or tautomerism of the S3 (+) ground state as it approaches a configuration conducive to dioxygen formation. The parallel impacts on both the lag and O2 formation phases suggest a common origin for the defects surmised to be perturbations of the H-bond network and the water cluster adjacent to O5.


Asunto(s)
Modelos Moleculares , Oxígeno/metabolismo , Complejo de Proteína del Fotosistema II/química , Complejo de Proteína del Fotosistema II/metabolismo , Agua/metabolismo , Materiales Biomiméticos , Cinética , Oxidación-Reducción , Oxígeno/química , Conformación Proteica , Energía Solar , Tilacoides/metabolismo
14.
Nano Lett ; 17(4): 2165-2171, 2017 04 12.
Artículo en Inglés | MEDLINE | ID: mdl-28230376

RESUMEN

Thermal runaways triggered by the oxygen release from oxide cathode materials pose a major safety concern for widespread application of lithium ion batteries. Utilizing in situ aberration-corrected scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS) at high temperatures, we show that oxygen release from LixCoO2 cathode crystals is occurring at the surface of particles. We correlated this local oxygen evolution from the LixCoO2 structure with local phase transitions spanning from layered to spinel and then to rock salt structure upon exposure to elevated temperatures. Ab initio molecular dynamics simulations (AIMD) results show that oxygen release is highly dependent on LixCoO2 facet orientation. While the [001] facets are stable at 300 °C, oxygen release is observed from the [012] and [104] facets, where under-coordinated oxygen atoms from the delithiated structures can combine and eventually evolve as O2. The novel understanding that emerges from the present study provides in-depth insights into the thermal runaway mechanism of Li-ion batteries and can assist the design and fabrication of cathode crystals with the most thermally stable facets.

15.
New Phytol ; 205(3): 1264-1276, 2015 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-25367685

RESUMEN

Seagrass is constantly challenged with transporting sufficient O2 from above- to belowground tissue via aerenchyma in order to maintain aerobic metabolism and provide protection against phytotoxins. Electrochemical microsensors were used in combination with a custom-made experimental chamber to analyse the belowground biogeochemical microenvironment of Zostera muelleri under changing environmental conditions. Measurements revealed high radial O2 release of up to 500 nmol O2 cm(-2) h(-1) from the base of the leaf sheath, maintaining a c. 300-µm-wide plant-mediated oxic microzone and thus protecting the vital meristematic regions of the rhizome from reduced phytotoxic metabolites such as hydrogen sulphide (H2S). H2S intrusion was prevented through passive diffusion of O2 to belowground tissue from leaf photosynthesis in light, as well as from the surrounding water column into the flow-exposed plant parts during darkness. Under water column hypoxia, high belowground H2S concentrations at the tissue surface correlated with the inability to sustain the protecting oxic microshield around the meristematic regions of the rhizome. We also found increased pH levels in the immediate rhizosphere of Z. muelleri, which may contribute to further detoxification of H2S through shifts in the chemical speciation of sulphide. Zostera muelleri can modify the geochemical conditions in its immediate rhizosphere, thereby reducing its exposure to H2S.


Asunto(s)
Sedimentos Geológicos/química , Sulfuro de Hidrógeno/toxicidad , Oxígeno/metabolismo , Zosteraceae/metabolismo , Concentración de Iones de Hidrógeno , Modelos Biológicos , Complejo de Proteína del Fotosistema II/metabolismo , Brotes de la Planta/efectos de los fármacos , Brotes de la Planta/metabolismo , Teoría Cuántica , Rizoma/efectos de los fármacos , Rizoma/metabolismo , Rizosfera , Espectrometría de Fluorescencia
16.
ACS Appl Mater Interfaces ; 16(8): 9626-9639, 2024 Feb 28.
Artículo en Inglés | MEDLINE | ID: mdl-38372238

RESUMEN

The hypoxic microenvironment in osteosarcoma inevitably compromises the antitumor effect and local bone defect repair, suggesting an urgent need for sustained oxygenation in the tumor. The currently reported oxygen-releasing materials have short oxygen-releasing cycles, harmful products, and limited antitumor effects simply by improving hypoxia. Therefore, the PCL/nHA/MgO2/PDA-integrated oxygen-releasing scaffold with a good photothermal therapy effect was innovatively constructed in this work to achieve tumor cell killing and bone regeneration functions simultaneously. The material distributes MgO2 powder evenly on the scaffold material through 3D printing technology and achieves the effect of continuous oxygen release (more than 3 weeks) through its slow reaction with water. The in vitro and in vivo results also indicate that the scaffold has good biocompatibility and sustained-release oxygen properties, which can effectively induce the proliferation and osteogenic differentiation of bone mesenchymal stem cells, achieving excellent bone defect repair. At the same time, in vitro cell experiments and subcutaneous tumorigenesis experiments also confirmed that local oxygen supply can promote osteosarcoma cell apoptosis, inhibit proliferation, and reduce the expression of heat shock protein 60, thereby enhancing the photothermal therapy effect of polydopamine and efficiently eliminating osteosarcoma. Taken together, this integrated functional scaffold provides a unique and efficient approach for antitumor and tumor-based bone defect repair for osteosarcoma treatment.


Asunto(s)
Neoplasias Óseas , Compuestos de Magnesio , Osteosarcoma , Peróxidos , Humanos , Andamios del Tejido , Osteogénesis , Oxígeno/farmacología , Óxido de Magnesio , Regeneración Ósea , Osteosarcoma/terapia , Neoplasias Óseas/tratamiento farmacológico , Impresión Tridimensional , Terapia Combinada , Microambiente Tumoral
17.
J Conserv Dent Endod ; 27(3): 337-341, 2024 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-38634020

RESUMEN

Context: External inflammatory root resorption has rapid onset and progresses aggressively. It leads to cementum loss, which allows communication between the infected pulp and the periodontium through the denuded dentinal tubules. Primary management strategy includes adequate chemomechanical debridement and lesion arrest for which maintaining alkaline pH and aerobic conditions is essential for healing and repair of the resorption defect. Aims: The aim of this study is to evaluate rise in pH and oxygen release at the site of simulated external root resorption cavities using different oxygen-releasing biomaterials. Materials and Methods: In 40 extracted single-rooted teeth access opening and chemomechanical debridement were done. Cavities simulating resorption defect are prepared on the roots. The samples are divided into four groups (n = 10) based on the biomaterial used. After placing the biomaterial, the root apices were sealed. Half of the samples from each group were tested for oxygen release using dissolved oxygen meter and the other half for rise in pH using pH meter at 7, 14, 21, and 28 days. Statistical Analysis: The pH values were analyzed using Friedman 2-way analysis of variance (ANOVA) and Kruskal-Wallis test. Oxygen release was measured using the two-way and repeated-measures ANOVA. Results: Calcium peroxide group showed the highest mean pH and oxygen release than other groups at any given point of time. Conclusions: Incorporating oxygen-releasing biomaterials such as calcium peroxide and perfluorodecalin into intracanal medicaments, such as calcium hydroxide, creates an alkaline and oxygen-enriched milieu in the periapical tissues.

18.
Int J Pharm ; 651: 123760, 2024 Feb 15.
Artículo en Inglés | MEDLINE | ID: mdl-38163525

RESUMEN

Designing biodegradable microparticles with finely controlled release properties for tissue engineering systems remains a significant scientific challenge. This study introduces a novel approach by fabricating urethane-linked PLA/PGS microparticles loaded with magnesium peroxide. The microparticles offer potential applications in bone tissue engineering due to their ability to provide a controlled release of oxygen and magnesium ions while maintaining physiological pH. The PGS pre-polymer was synthesized via polycondensation and characterized using FTIR, 1H NMR, and GPC. Microparticle morphology transformed from smooth to raspberry-like upon incorporation of PGS, as observed by SEM. Microparticle size was tuned by varying PGS and PLA concentrations. FTIR analysis confirmed the successful formation of urethane links within the microparticles. MgO2-loaded PLA/PGS microparticles exhibited sustained release of dissolved oxygen and magnesium ions for 21 days while maintaining physiological pH better than PLA microparticles. Cell viability assays confirmed microparticle cytocompatibility, and ALP and Alizarin red assays demonstrated their ability to induce osteogenic differentiation. These findings highlight the potential of pH-controlled MgO2-loaded microparticles as an effective system for bone tissue engineering. In conclusion, this study presents a novel approach to designing biodegradable microparticles with adjustable release properties for bone tissue engineering. The urethane-based MgO2-loaded microparticles provide controlled release of oxygen and magnesium ions and regulate the environment's pH, making them a promising system for bone tissue engineering applications.


Asunto(s)
Osteogénesis , Rubus , Ingeniería de Tejidos , Magnesio/química , Preparaciones de Acción Retardada , Uretano , Óxido de Magnesio , Iones , Poliésteres/química
19.
Sci Rep ; 14(1): 6967, 2024 03 23.
Artículo en Inglés | MEDLINE | ID: mdl-38521805

RESUMEN

In this study, the ecological impact of human activities and the space occupied by construction and arable land on the Tibetan Plateau were examined, focusing on changes in the net primary productivity (NPP) as a key indicator of ecological health. With the utilization of land use data and multiyear average NPP data from 2002 to 2020, we analyzed the effects of the conversion of zonal vegetation into construction and arable land on carbon sequestration and oxygen release in Chengguan District, Lhasa city. Our findings indicated a marked spatial difference in the NPP among different land types. Regarding the original zonal vegetation, the NPP ranged from 0.2 to 0.3 kg/m2. Construction land showed a decrease in the NPP, with values ranging from 0.16 to 0.26 kg/m2, suggesting a decrease in ecological productivity. Conversely, arable land exhibited an increase in the NPP, with average values exceeding 0.3 kg/m2. This increase suggested enhanced productivity, particularly in regions where the original zonal vegetation provided lower NPP values. However, this enhanced productivity may not necessarily indicate a positive ecological change. In fact, such increases could potentially disrupt the natural balance of ecosystems, leading to unforeseen ecological consequences. The original zonal vegetation, with NPP values ranging from 0.12 to 0.43 kg/m2, exhibited higher ecological stability and adaptability than the other land types. This wider NPP range emphasizes the inherent resilience of native vegetation, which could sustain diverse ecological functions under varying environmental conditions. These findings demonstrate the urgent need for sustainable land use management on the Tibetan Plateau. This study highlights the importance of considering the ecological impact of land use changes in regional development strategies, ensuring the preservation and enhancement in the unique and fragile plateau ecosystem.


Asunto(s)
Ecosistema , Modelos Teóricos , Humanos , Tibet , Ciudades , Actividades Humanas , China , Cambio Climático
20.
J Colloid Interface Sci ; 674: 238-248, 2024 Nov 15.
Artículo en Inglés | MEDLINE | ID: mdl-38936080

RESUMEN

The voltage decay of Li-rich layered oxide cathode materials results in the deterioration of cycling performance and continuous energy loss, which seriously hinders their application in the high-energy-density lithium-ion battery (LIB) market. However, the origin of the voltage decay mechanism remains controversial due to the complex influences of transition metal (TM) migration, oxygen release, indistinguishable surface/bulk reactions and the easy intra/inter-crystalline cracking during cycling. We investigated the direct cause of voltage decay in micrometer-scale single-crystal Li1.2Mn0.54Ni0.13Co0.13O2 (SC-LNCM) cathode materials by regulating the cut-off voltage. The redox of TM and O2- ions can be precisely controlled by setting different voltage windows, while the cracking can be restrained, and surface/bulk structural evaluation can be monitored because of the large single crystal size. The results show that the voltage decay of SC-LNCM is related to the combined effect of cation rearrangement and oxygen release. Maintaining the discharge cutoff voltage at 3 V or the charging cutoff voltage at 4.5 V effectively mitigates the voltage decay, which provides a solution for suppressing the voltage decay of Li-rich and Mn-based layered oxide cathode materials. Our work provides significant insights into the origin of the voltage decay mechanism and an easily achievable strategy to restrain the voltage decay for Li-rich and Mn-based cathode materials.

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