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1.
Lasers Med Sci ; 39(1): 112, 2024 Apr 24.
Artigo em Inglês | MEDLINE | ID: mdl-38656634

RESUMO

PURPOSE: To measure the dynamic characteristics of the flow field in a complex root canal model activated by two laser-activated irrigation (LAI) modalities at different activation energy outputs: photon-induced photoacoustic streaming (PIPS) and microshort pulse (MSP). METHODS: A phase-locked micro-scale Particle Image Velocimetry (µPIV) system was employed to characterise the temporal variations of LAI-induced velocity fields in the root canal following a single laser pulse. The wall shear stress (WSS) in the lateral root canal was subsequently estimated from the phase-averaged velocity fields. RESULTS: Both PIPS and MSP were able to generate the 'breath mode' of the irrigant current under all tested conditions. The transient irrigation flush in the root canal peaked at speeds close to 6 m/s. However, this intense flushing effect persisted for only about 2000 µs (or 3% of a single laser-pulse activation cycle). For MSP, the maximum WSS magnitude was approximately 3.08 Pa at an activation energy of E = 20 mJ/pulse, rising to 9.01 Pa at E = 50 mJ/pulse. In comparison, PIPS elevated the WSS to 10.63 Pa at E = 20 mJ/pulse. CONCLUSION: Elevating the activation energy can boost the peak flushing velocity and the maximum WSS, thereby enhancing irrigation efficiency. Given the same activation energy, PIPS outperforms MSP. Additionally, increasing the activation frequency may be an effective strategy to improve irrigation performance further.


Assuntos
Reologia , Humanos , Cavidade Pulpar/efeitos da radiação , Irrigação Terapêutica/métodos , Irrigação Terapêutica/instrumentação , Lasers , Irrigantes do Canal Radicular , Técnicas Fotoacústicas/métodos , Preparo de Canal Radicular/métodos , Preparo de Canal Radicular/instrumentação
2.
Angew Chem Int Ed Engl ; 63(9): e202317613, 2024 Feb 26.
Artigo em Inglês | MEDLINE | ID: mdl-38195970

RESUMO

Most of the anticancer compounds synthesized by chemists are primarily evaluated for their direct cytotoxic effects at the cellular level, often overlooking the critical role of the immune system. In this study, we developed a patient-derived, T-cell-retaining tumor organoid model that allows us to evaluate the anticancer efficacy of chemical drugs under the synergistic paradigm of antigen-specific T-cell-dependent killing, which may reveal the missed drug hits in the simple cytotoxic assay. We evaluated clinically approved platinum (Pt) drugs and a custom library of twenty-eight PtIV compounds. We observed low direct cytotoxicity of Pt drugs, but variable synergistic effects in combination with immune checkpoint inhibitors (ICIs). In contrast, the majority of PtIV compounds exhibited potent tumor-killing capabilities. Interestingly, several PtIV compounds went beyond direct tumor killing and showed significant immunosynergistic effects with ICIs, outstanding at sub-micromolar concentrations. Among these, Pt-19, PtIV compounds with cinnamate axial ligands, emerged as the most therapeutically potent, demonstrating pronounced immunosynergistic effects by promoting the release of cytotoxic cytokines, activating immune-related pathways and enhancing T cell receptor (TCR) clonal expansion. Overall, this initiative marks the first use of patient-derived immunocompetent tumor organoids to explore and study chemotherapy, advancing their path toward more effective small molecule drug discovery.


Assuntos
Antineoplásicos , Humanos , Linhagem Celular Tumoral , Antineoplásicos/farmacologia , Antineoplásicos/química , Platina/química , Linfócitos T , Organoides
3.
Cell Death Dis ; 14(12): 800, 2023 12 07.
Artigo em Inglês | MEDLINE | ID: mdl-38062004

RESUMO

Ferroptosis is an iron-dependent form of regulated cell death driven by the lethal lipid peroxides. Previous studies have demonstrated that inducing ferroptosis holds great potential in cancer therapy, especially for patients with traditional therapy failure. However, cancer cells can acquire ferroptosis evasion during progression. To date, the therapeutic potential of inducing ferroptosis in bladder cancer (BCa) remains unclear, and whether a ferroptosis escape mechanism exists in BCa needs further investigation. This study verified that low pathological stage BCa cells were highly sensitive to RSL3-induced ferroptosis, whereas high pathological stage BCa cells exhibited obviously ferroptosis resistance. RNA-seq, RNAi-mediated loss-of-function, and CRISPR/Cas9 experiments demonstrated that ALOX5 deficiency was the crucial factor of BCa resistance to ferroptosis in vitro and in vivo. Mechanistically, we found that ALOX5 deficiency was regulated by EGR1 at the transcriptional level. Clinically, ALOX5 expression was decreased in BCa tissues, and its low expression was associated with poor survival. Collectively, this study uncovers a novel mechanism for BCa ferroptosis escape and proposes that ALOX5 may be a valuable therapeutic target and prognostic biomarker in BCa treatment.


Assuntos
Ferroptose , Neoplasias da Bexiga Urinária , Humanos , Ferroptose/genética , Neoplasias da Bexiga Urinária/genética , Neoplasias da Bexiga Urinária/patologia , Araquidonato 5-Lipoxigenase/genética
4.
Heliyon ; 9(3): e13661, 2023 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-36873527

RESUMO

Objectives: To analyze the correlations between the expression and effect of DNA damage repair genes and the immune status and clinical outcomes of urothelial bladder cancer (BLCA) patients. In addition, we evaluate the efficacy and value of utilizing the DNA damage repair genes signature as a prognosis model for BLCA. Methods: Two subtype groups (C1 and C2) were produced based on the varied expression of DNA damage repair genes. Significantly differentiated genes and predicted enriched gene pathways were obtained between the two subtypes. Seven key genes were obtained from the DNA damage repair-related genes and a 7-gene signature prognosis model was established based on the key genes. The efficacy and accuracy of this model in prognosis prediction was evaluated and verified in two independent databases. Also, the difference in biological functions, drug sensitivity, immune infiltration and affinity between the high-risk group and low-risk group was analyzed. Results: The DNA damage repair gene signature could significantly differentiate the BLCA into two molecular subgroups with varied genetic expression and enriched gene pathways. Seven key genes were screened out from the 232 candidate genes for prognosis prediction and a 7-gene signature prognosis model was established based on them. Two independent patient cohorts (TCGA cohort and GEO cohort) were utilized to validate the efficacy of the prognosis model, which demonstrated an effective capability to differentiate and predict the overall survival of BLCA patients. Also, the high-risk group and low-risk group derived from the 7-gene model exhibited significantly differences in drug sensitivity, immune infiltration status and biological pathways enrichment. Conclusions: Our established 7-gene signature model based on the DNA damage repair genes could serve as a novel prognosis predictive tool for BLCA. The differentiation of BLCA patients based on the 7-gene signature model may be of great value for the appropriate selection of specific chemotherapy agents and immune-checkpoint blockade therapy administration.

5.
Front Genet ; 13: 919829, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36246597

RESUMO

Bladder cancer (BLCA) is one of the most common malignant tumors of the urinary system, but the current therapeutic strategy based on chemotherapy and immune checkpoint inhibitor (ICI) therapy cannot meet the treatment needs, mainly owing to the endogenous or acquired apoptotic resistance of cancer cells. Targeting necroptosis provides a novel strategy for chemotherapy and targeted drugs and improves the efficacy of ICIs because of strong immunogenicity of necroptosis. Therefore, we systemically analyzed the necroptosis landscape on therapy and prognosis in BLCA. We first divided BLCA patients from The Cancer Genome Atlas (TCGA) database into two necroptosis-related clusters (C1 and C2). Necroptosis C2 showed a significantly better prognosis than C1, and the differential genes of C2 and C1 were mainly related to the immune response according to GO and KEGG analyses. Next, we constructed a novel necroptosis-related gene (NRG) signature consisting of SIRT6, FASN, GNLY, FNDC4, SRC, ANXA1, AIM2, and IKBKB to predict the survival of TCGA-BLCA cohort, and the accuracy of the NRG score was also verified by external datasets. In addition, a nomogram combining NRG score and several clinicopathological features was established to more accurately and conveniently predict the BLCA patient's survival. We also found that the NRG score was significantly related to the infiltration levels of CD8 T cells, NK cells, and iDC cells, the gene expression of CTLA4, PD-1, TIGIT, and LAG3 of TME, and the sensitivity to chemotherapy and targeted agents in BLCA patients. In conclusion, the NRG score has an excellent performance in evaluating the prognosis, clinicopathologic features, tumor microenvironment (TME), and therapeutic sensitivity of BLCA patients, which could be utilized as a guide for chemotherapy, ICI therapy, and combination therapy.

6.
Molecules ; 27(17)2022 Sep 05.
Artigo em Inglês | MEDLINE | ID: mdl-36080477

RESUMO

The Rat Sarcoma (RAS) family (NRAS, HRAS, and KRAS) is endowed with GTPase activity to regulate various signaling pathways in ubiquitous animal cells. As proto-oncogenes, RAS mutations can maintain activation, leading to the growth and proliferation of abnormal cells and the development of a variety of human cancers. For the fight against tumors, the discovery of RAS-targeted drugs is of high significance. On the one hand, the structural properties of the RAS protein make it difficult to find inhibitors specifically targeted to it. On the other hand, targeting other molecules in the RAS signaling pathway often leads to severe tissue toxicities due to the lack of disease specificity. However, computer-aided drug design (CADD) can help solve the above problems. As an interdisciplinary approach that combines computational biology with medicinal chemistry, CADD has brought a variety of advances and numerous benefits to drug design, such as the rapid identification of new targets and discovery of new drugs. Based on an overview of RAS features and the history of inhibitor discovery, this review provides insight into the application of mainstream CADD methods to RAS drug design.


Assuntos
Desenho Assistido por Computador , Neoplasias , Animais , Biologia Computacional , Desenho de Fármacos , Humanos , Neoplasias/patologia , Proteínas/química
7.
Lasers Surg Med ; 2020 Sep 10.
Artigo em Inglês | MEDLINE | ID: mdl-32964491

RESUMO

BACKGROUND AND OBJECTIVES: Photon-induced photoacoustic streaming (PIPS) and shockwave-enhanced emission photoacoustic streaming (SWEEPS) are two promising laser-activated irrigation (LAI) methods for root canal irrigation. Their performance in driving irrigant flush in a complex root canal system will be evaluated by microscale particle image velocimetry (µPIV) measurement and will be compared with that of ultrasonic-activated irrigation (UAI). STUDY DESIGN/MATERIALS AND METHODS: A µPIV system with 7 µm fluorescent tracer particles was adopted to measure two-dimensional (2D) velocity fields around the junction region, with a size of 1.8 mm × 1.5 mm, between one main canal and one lateral canal in an endodontic training block, which was driven by SWEEPS (Er:YAG laser) operating at 15 Hz and 20 mJ. The flow field driven by PIPS (Er:YAG laser) at the same frequency and energy, as well as by UAI (with non-cutting insert) operating at 40% unit power, was also measured for a direct comparison. RESULTS: It was found that both SWEEPS and PIPS can activate a so-called "breath mode" during the irrigation. Namely, the induced irrigant flush presented a back-and-forth oscillation along both the main canal and the lateral one. The maximum flow speed in the lateral canal was observed to be up to 10 m/s in the SWEEPS modality, while reduced to around 7 m/s in the PIPS modality. The penetration length in the lateral canal in both modalities was estimated to be larger than 1 mm. In comparison, the flow field induced by UAI was characterized as irregular vortical structures, the maximum flow speed in the lateral canal was 0.15 m/s and significantly lower than LAI (P < 0.01), and the penetration length was less than 300 µm and lower than LAI (P < 0.05). CONCLUSION: Compared to UAI, PIPS, and SWEEPS are more capable of delivering the irrigant deeper into the lateral canal. Furthermore, the back-and-forth flush in the breath mode is ideal for removing debris during irrigation. Lasers Surg. Med. © 2020 Wiley Periodicals LLC.

8.
Sensors (Basel) ; 20(17)2020 Sep 02.
Artigo em Inglês | MEDLINE | ID: mdl-32887418

RESUMO

Secure grasping of fragile fruits and other agricultural products without potential slip and damage is still a challenge due to the size and shape varying, bruise susceptible, as well as hardness changing during fruit and vegetable maturation. In the robotic grasping process, the mechanical damage mainly depends upon the aggressiveness of the gripper and the sensitivity of the product to the damage. In this study, a flexible gripper integrated with multi-sensor network is designed and tested. The network proposed includes three kinds of sensors that enable the gripper to grasp various products with the sense of touch and visual perception. Particular attention has been attached to the sensors applied between the fingers, and this makes sensing and grasping capabilities improved. To create an accurate grasping system, a grasping algorithm and the force control model are proposed for any bending state based on Cosserat theory. The boundary detection is included in the grasping algorithm, detecting the shape edge by some certain point calculation. The created grasping system guarantees mechanical compliance by evaluating and adjusting the finger status including force, angle, and direction. Multi-group tests have been done on grasping several objects of different sizes and materials in daily life. The relationship between force, bending, and surface material is also analyzed and compared under different conditions. The numerical comparisons related to the measurement error are analyzed based on their standard deviations. Experimental results indicate that this flexible manipulator with proposed system and strategy has better grasping ability for fragile fruits with its good flexibility and dexterity.


Assuntos
Frutas , Robótica , Estudos de Viabilidade , Força da Mão
9.
ACS Appl Mater Interfaces ; 11(29): 26460-26466, 2019 Jul 24.
Artigo em Inglês | MEDLINE | ID: mdl-31267730

RESUMO

Negative exchange bias is usually discovered in ferromagnetic (FM)/antiferromagnetic (AFM) heterostructures after a field-cooling (FC) process. Relatively, positive exchange bias (PEB) is a rarely observed phenomenon. So far, almost all of the models for PEB whether undergoing FC or zero-field-cooling (ZFC) treatment have been explained by an interaction of strong AFM coupling at the interface. In this work, by selecting a special material of SrFeO3-x as the AFM layer, coupled with FM-La0.7Sr0.3MnO3 (LSMO), we obtain a novel PEB effect of the bilayer after ZFC measurement, of which the shift directions are unfixable and dependent on the initial magnetization direction. Based on a transient magnetic field to control the remanence (Mr) direction of LSMO at room temperature and then cooling below the TN of SrFeO3-x without any magnetic field disturbance, the shift direction can be locked only toward the transient magnetic field. Combined with experimental results and first-principles calculations, we propose that the above phenomena are explained as the field-induced AFM phase of SrFeO3-x transforming into the FM phase at an FM coupling bilayer interface. Thus, our finding may provide a new approach to realize and tune the zero-field-cooling PEB with FM coupling heterostructures.

10.
J Periodontol ; 90(4): 391-399, 2019 04.
Artigo em Inglês | MEDLINE | ID: mdl-30378773

RESUMO

BACKGROUND: Human periodontal ligament fibroblasts (HPDLFs) represent the first line of defense against pathogens in the periodontal tissue. Porphyromonas gingivialis (P. gingivalis) has been known to be most strongly associated with periodontitis. MicroRNA (miR)-146a is involved in the inflammatory regulation of periodontitis. However, the regulatory mechanism of miR-146a on in P. gingivalis-induced inflammation response in HPDLFs was still unclear. The aim of this study was to investigate whether miR-146a plays a key role in P. gingvalis-induced inflammation responses through regulation of TRAF6 in HPDLFs. METHODS: MiR-146a expression was measured by real-time polymerase chain reaction (PCR) in HPDLFs stimulated with P. gingivalis and its lipopolysaccharide (LPS). IL-1ß, IL-6, and IL-8 were determined by enzyme-linked immunosorbent assay (ELISA) in the culture supernatants of HPDLFs after transfected with miR-146a mimic or inhibitor. Meanwhile, the expression of TRAF6 was measured by real-time PCR and Western blot. Then, we used luciferase reporter assay to detect whether miR-146a binds to the 3'-UTR of TRAF6. By using small interfering RNA (siRNA) of TRAF6, the phosphorylation of p38 mitogen-activated protein kinase (MAPK) was measured by Western blot. Finally, after inhibition of TRAF6 and p38 in HPDLFs, we analyzed the expression of miR-146a upon P. gingivalis challenge. RESULTS: P. gingivalis and its LPS significantly induced miR-146a expression in HPDLFs. Overexpression of miR-146a significantly suppressed the IL-1ß, IL-6 and IL-8 secretion, TRAF6 expression, and p38 phosphorylation. In contrast, the levels of these indexes significantly increased by inhibition of miR-146a. Furthermore, MiR-146a directly binds to the 3'-UTR of TRAF6 in P. gingivalis-induced HPDLFs, but not in P. gingivalis LPS stimulation. Suppression of TRAF6 could inhibit the phosphorylation of p38. Finally, inhibition of TRAF6 and p38 significantly abolished P. gingivalis-induced miR-146a upregulation in HPDLFs. CONCLUSIONS: MiR-146a contribute to negative regulation of P. gingivalis-induced proinflammatory cytokines secretion in HPDLFs though TRAF6/p38 MAPK pathway. Maintaining miR-146a homeostasis plays a key role in controlling inflammatory response in periodontal tissues.


Assuntos
MicroRNAs , Fator 6 Associado a Receptor de TNF , Células Cultivadas , Fibroblastos , Humanos , Lipopolissacarídeos , Ligamento Periodontal , Porphyromonas gingivalis
11.
ACS Appl Mater Interfaces ; 9(45): 39855-39862, 2017 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-29057645

RESUMO

Paramagnetic LaNiO3 (LNO)-based heterostructures have been attracting the attention of researches, especially since the interesting exchange bias (EB) effect has been observed in (111)-oriented LaMnO3 (LMO)/LNO superlattices (SLs). However, this effect is not expected to occur in the (001) direction SLs. In this paper, we report the observation of an unexpected EB effect in (001)-oriented (LMO)3/(LNO)t SLs. The orbits of interfacial Mn/Ni ions preferentially occupy the strain-stabilized x2 - y2 in ultrathin LNO layers [t ≤ 4 unit cells (u.c.)]. Conversely, as the LNO layer becomes thicker (t ≥ 6 u.c.), the EB effect is absent, and the orbits are reconstructed to form the 3z2 - r2 preferential occupancy. The absence of the EB in thicker LNO-based SLs is attributed to the interfacial charge transfer suppressed by orbital reconstruction as a consequence of the increasing LNO thickness. In the thinner LNO-based SLs, the larger charge transfer results in stronger localized magnetic moments for the cause of the EB effect. These results provide a useful interpretation of the relationship between macroscopic magnetic properties and the microscopic electronic structure in oxide-based heterostructures.

12.
Sci Rep ; 7(1): 10557, 2017 09 05.
Artigo em Inglês | MEDLINE | ID: mdl-28874786

RESUMO

With the goal of observing and explaining the unexpected exchange bias effect in paramagnetic LaNiO3-based superlattices, a wide range of theoretical and experimental research has been published. Within the scope of this work, we have grown high-quality epitaxial LaMnO3(n)-LaNiO3(n) (LMO/LNO) superlattices (SLs) along (001)-, (110)-, and (111)-oriented SrTiO3 substrates. The exchange bias effect is observed in all cases, regardless of growth orientation of the LMO/LNO SLs. As a result of a combination of a number of synchrotron based x-ray spectroscopy measurements, this effect is attributed to the interfacial charge transfer from Mn to Ni ions that induces localized magnetic moments to pin the ferromagnetic LMO layer. The interaction per area between interfacial Mn and Ni ions is nearly consistent and has no effect on charge transfer for different orientations. The discrepant charge transfer and orbital occupancy can be responsible for the different magnetic properties in LMO/LNO superlattices. Our experimental results present a promising advancement in understanding the origin of magnetic properties along different directions in these materials.

13.
Nanoscale Res Lett ; 12(1): 330, 2017 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-28476085

RESUMO

We study the magnetic properties of an epitaxial growth bilayer composed of ferromagnetic La0.7Sr0.3MnO3 (LSMO) and paramagnetic LaNiO3 (LNO) on SrTiO3 (STO) substrates. We find that the stack order of the bilayer heterostructure plays a key role in the interfacial coupling strength, and the coupling at the LSMO(top)/LNO(bottom) interface is much stronger than that at the LNO(top)/LSMO(bottom). Moreover, a strong spin glass state has been observed at the LSMO/LNO interface, which is further confirmed by two facts: first, that the dependence of the irreversible temperature on the cooling magnetic field follows the Almeida-Thouless line and, second, that the relaxation of the thermal remnant magnetization can be fitted by a stretched exponential function. Interestingly, we also find an exchange bias effect at the LSMO/LNO bilayer below the spin glass freezing temperature, indicating that the exchange bias is strongly correlated with the spin glass state at its interface.

14.
Photodiagnosis Photodyn Ther ; 18: 119-127, 2017 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-28188919

RESUMO

PURPOSE: To evaluate the clinical efficacy of photodynamic therapy (PDT) adjunctive to scaling and root planing (SRP) in patients with untreated chronic periodontitis based on up-to-date evidence. METHODS: MEDLINE and the Cochrane Library were systematically searched to identify eligible randomized controlled trials (RCTs), supplemented by a manual literature search. Mean differences (MD) and the corresponding 95% confidence intervals (CI) of probing depth (PD) reduction and clinical attachment level (CAL) gain were synthesized. The I2 test and Q statistics were used to determine the inter-study heterogeneity. Subgroup analysis based on smoking status was performed. RESULTS: Eleven RCTs with a total of 243 subjects were included. Significant improvement in PD reduction (MD=0.13, CI:0.02-0.24, p=0.02) and marginal significant improvement in CAL gain (MD=0.18, CI:-0.005-0.363, p=0.056) were observed in favor of SRP+PDT at 3months. When evaluated at 6months after baseline, the association of PDT with SRP resulted in a significant benefit in PD reduction (MD=0.40, CI:0.05-0.74, p=0.03), but not in CAL gain (MD=0.37, CI:-0.18-0.93, p=0.18). Subgroup analysis revealed that the combined therapy produced no significant improvements in PD and CAL at neither 3months nor 6months for studies with smokers. No treatment-related adverse events or side effects had been reported by the included studies. CONCLUSIONS: Pooled analysis suggests a short-term benefit of PDT as an adjunct to SRP in clinical outcome variables. However, evidence regarding its long-term efficacy is still insufficient and no significant effect has been confirmed in terms of CAL gain at 6months. Future clinical trials of high methodological quality are needed to establish the optimal combination of photosensitizer and laser configuration.


Assuntos
Terapia Combinada/estatística & dados numéricos , Raspagem Dentária/estatística & dados numéricos , Periodontite/epidemiologia , Periodontite/terapia , Fotoquimioterapia/estatística & dados numéricos , Fármacos Fotossensibilizantes/administração & dosagem , Aplainamento Radicular/estatística & dados numéricos , Adolescente , Adulto , Idoso , Doença Crônica , Medicina Baseada em Evidências , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Periodontite/diagnóstico , Prevalência , Fatores de Risco , Resultado do Tratamento , Adulto Jovem
15.
ACS Appl Mater Interfaces ; 9(3): 3156-3160, 2017 Jan 25.
Artigo em Inglês | MEDLINE | ID: mdl-28067035

RESUMO

Artificial heterostructures based on LaNiO3 (LNO) have been widely investigated with the aim to realize the insulating antiferromagnetic state of LNO. In this work, we grew [(La0.7Sr0.3MnO3)5-(LaNiO3)n]12 superlattices on (001)-oriented SrTiO3 substrates by pulsed laser deposition and observed an unexpected exchange bias effect in field-cooled hysteresis loops. Through X-ray absorption spectroscopy and magnetic circular dichroism experiments, we found that the charge transfer at the interfacial Mn and Ni ions can induce a localized magnetic moment. A remarkable increase of exchange bias field and a transition from metal to insulator were simultaneously observed upon decreasing the thickness of the LNO layer, indicating the antiferromagnetic insulator state in 2 unit cells LNO ultrathin layers. The robust exchange bias of 745 Oe in the superlattice is caused by an interfacial localized magnetic moment and an antiferromagnetic state in the ultrathin LNO layer, pinning the ferromagnetic La0.7Sr0.3MnO3 layers together. Our results demonstrate that artificial interface engineering is a useful method to realize novel magnetic and transport properties.

16.
Macromol Rapid Commun ; 38(13)2017 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-27778422

RESUMO

Carbon dioxide (CO2 )-responsive polymer nano-objects are prepared by photoinitiated reversible addition-fragmentation chain transfer dispersion polymerization of 2-hydroxypropyl methacrylate and 2-(dimethylamino)ethyl methacrylate (DMAEMA) in water at room temperature using a poly(poly(ethylene glycol) methyl ether methacrylate) macromolecular chain transfer agent. Kinetic studies confirm that full monomer conversions are achieved in all cases within 10 min of visible-light irradiation (405 nm, 0.5 mW cm-2 ). The effect of DMAEMA on the polymerization is studied in detail, and pure higher order morphologies (worms and vesicles) are prepared by this particular formulation. Finally, CO2 -responsive property of the obtained vesicles is investigated by dynamic light scattering, visual appearance, and transmission electron microscope.


Assuntos
Dióxido de Carbono/química , Fotoquímica , Polimerização , Polímeros/síntese química , Cinética , Luz , Metacrilatos/química , Polimerização/efeitos da radiação
17.
Sci Rep ; 6: 31934, 2016 09 02.
Artigo em Inglês | MEDLINE | ID: mdl-27585644

RESUMO

Combining resistive switching and magnetoresistance in a system exhibits great potential for application in multibit nonvolatile data storage. It is in significance and difficulty to seek a material with resistances that can be stably switched at different resistance states modulated by an electrical field and a magnetic field. In this paper, we propose a novel electrode/ZnO/ZnO-Co/electrode device in which the storage layer combines a nanostructured ZnO-Co layer and a ZnO layer. The device exhibits bipolar resistive switching characteristics, which can be explained by the accumulation of oxygen vacancies due to the migration of oxygen ions by external electrical stimuli and the contribution of Co particles in the ZnO-Co layer. Moreover, the magnetoresistance effect at room temperature can be observed in the device at high and low resistance states. Therefore, through electrical and magnetic control, four resistance states are achieved in this system, presenting a new possibility towards enhancing data densities by many folds.

18.
Macromol Rapid Commun ; 37(17): 1434-40, 2016 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-27439569

RESUMO

Photoinitiated reversible addition-fragmentation chain transfer (RAFT) dispersion polymerization of 2-hydroxypropyl methacrylate is conducted in water at low temperature using thermoresponsive copolymers of 2-(2-methoxyethoxy) ethyl methacrylate and oligo(ethylene glycol) methacrylate (Mn = 475 g mol(-1) ) as the macro-RAFT agent. Kinetic studies confirm that quantitative monomer conversion is achieved within 15 min of visible-light irradiation (405 nm, 0.5 mW cm(-2) ), and good control is maintained during the polymerization. The polymerization can be temporally controlled by a simple "ON/OFF" switch of the light source. Finally, thermoresponsive diblock copolymer nano-objects with a diverse set of complex morphologies (spheres, worms, and vesicles) are prepared using this particular formulation.


Assuntos
Nanoestruturas/química , Polímeros/síntese química , Temperatura , Substâncias Macromoleculares/síntese química , Substâncias Macromoleculares/química , Estrutura Molecular , Tamanho da Partícula , Processos Fotoquímicos , Polimerização , Polímeros/química , Propriedades de Superfície , Água/química
19.
ACS Macro Lett ; 5(8): 894-899, 2016 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-35607218

RESUMO

We report a fast alcoholic photoinitiated polymerization-induced self-assembly (photo-PISA) formulation via photoinitiated RAFT dispersion polymerization of isobornyl acrylate (IBOA) in an ethanol/water mixture at 40 °C using a monomethoxy poly(ethylene glycol) (mPEG) based chain transfer agent. Polymerization proceeded rapidly via the exposure to visible light irradiation (405 nm, 0.5 mW/cm2), and high monomer conversion (>95%) was achieved within 30 min. Kinetic studies confirmed that good control was maintained during the photo-PISA process, and the polymerization can be activated or deactivated by light. Finally, we demonstrated that a diverse set of complex morphologies (spheres, worms, or vesicles) could be achieved by varying reaction parameters, and a phase diagram was constructed.

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