Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 20 de 67
Filter
1.
Nanoscale ; 16(7): 3534-3548, 2024 Feb 15.
Article in English | MEDLINE | ID: mdl-38285061

ABSTRACT

Blood clotting disorders consisting of unwanted blood clot formation or excessive bleeding are some of the main causes of death worldwide. However, there are significant limitations in the current methods used to clinically monitor the dynamics of clot formation in human whole blood ex vivo. Here a new magnetic coagulometry platform for testing ex vivo coagulation is described. This platform exploits the sensitivity of the out-of-phase component of alternating current (AC) magnetic susceptibility (χ'') to variations in mobility and agglomeration of magnetic nanoparticles when trapped during blood clot formation. By labelling human whole blood with magnetic nanoparticles, the out-of-phase component of AC magnetic susceptibility shows that the dynamics of blood clot formation correlates with a decrease in the out-of-phase component χ'' over time activation of coagulation. This is caused by a rapid immobilisation of nanoparticles upon blood coagulation and compaction. In contrast, this rapid fall in the out-of-phase component χ'' is significantly slowed down when blood is pre-treated with three different anticoagulant drugs. Remarkably, the system showed sensitivity towards the effect of clinically used direct oral anticoagulation (DOAC) drugs in whole blood coagulation, in contrast to the inability of clinical routine tests prothrombin time (PT) and partial thromboplastin time (PTT) to efficiently monitor this effect. Translation of this nanomagnetic approach into clinic can provide a superior method for monitoring blood coagulation and improve the efficiency of the current diagnostic techniques.


Subject(s)
Blood Coagulation , Thrombosis , Humans , Blood Coagulation/physiology , Blood Coagulation Tests/methods , Prothrombin Time , Magnetic Phenomena
2.
Nanoscale ; 14(44): 16639-16646, 2022 Nov 17.
Article in English | MEDLINE | ID: mdl-36321630

ABSTRACT

Metal alloy nanoparticles, and, in particular, permalloy, still hold an untapped potential in nanotechnology, although their poor stability against oxidation due to environmental exposure limits their use in many technological applications, and even more in life sciences. We propose a scalable single-step microwave-assisted method to produce water suspensions of Ni1-xFex nanoparticles without the need for an inert atmosphere, either organic solvents or any type of post-processing. We use hydrazine as a reducer, iron(II), iron(III) and nickel(II) chloride as precursors, 1,12-dodecanediol as a surfactant and water as a reaction medium. The mixture is heated at 160 °C for 10 minutes to obtain uniform alloy nanoparticles with sizes of around 24.5 nm for Ni (0% Fe) and 5.5 nm for 35% Fe that are forming uniform aggregates with sizes between 200 nm for Ni and 65 nm for iron oxide NPs. A linear increase of saturation magnetization is observed with an Fe content of up to 25%, whereas for larger percentages a sudden drop takes place due to the formation of iron oxides. X-ray diffraction measurements rule out the formation of any oxides after more than one year of storage at 4 °C, surely due to the presence of 1,12-dodecanediol at the surface, as evidenced by infrared spectroscopy.

3.
Materials (Basel) ; 14(4)2021 Feb 03.
Article in English | MEDLINE | ID: mdl-33546176

ABSTRACT

The scientific community has made great efforts in advancing magnetic hyperthermia for the last two decades after going through a sizeable research lapse from its establishment. All the progress made in various topics ranging from nanoparticle synthesis to biocompatibilization and in vivo testing have been seeking to push the forefront towards some new clinical trials. As many, they did not go at the expected pace. Today, fruitful international cooperation and the wisdom gain after a careful analysis of the lessons learned from seminal clinical trials allow us to have a future with better guarantees for a more definitive takeoff of this genuine nanotherapy against cancer. Deliberately giving prominence to a number of critical aspects, this opinion review offers a blend of state-of-the-art hints and glimpses into the future of the therapy, considering the expected evolution of science and technology behind magnetic hyperthermia.

4.
Arthroplast Today ; 6(4): 866-871, 2020 Dec.
Article in English | MEDLINE | ID: mdl-33163601

ABSTRACT

We present a case report of a patient with osteopetrosis and refractory bilateral knees osteoarthritis who underwent bilateral total knee arthroplasties (TKAs). After conservative management has failed, surgical treatment with arthroplasty is an excellent alternative with satisfactory outcomes. TKA in patients with osteopetrosis has only been described in 6 other case studies, none of which underwent bilateral TKA. To perform this procedure, additional attention should be directed toward the presurgical planning because of the amplified difficulty of the procedure and the altered bone biology that increases the risks of intraoperative fractures and markedly extends the time of surgery. This report describes a case of osteopetrosis with refractory osteoarthritis managed with bilateral TKA, the surgical technique and special considerations, complications, and future recommendations.

5.
P R Health Sci J ; 39(3): 254-259, 2020 09.
Article in English | MEDLINE | ID: mdl-33031693

ABSTRACT

OBJECTIVE: Objectively evaluate the incidence of sciatic nerve injury after a total hip arthroplasty (THA) performed through a posterolateral approach. METHODS: Patients scheduled to undergo THA were evaluated preoperatively and postoperatively with electrophysiologic studies, the Western Ontario and McMaster Universities Osteoarthritis index (WOMAC) questionnaire and other methods described in the study. Patients older than 21 years with any of the following preoperative diagnoses: primary or secondary osteoarthritis, aseptic avascular necrosis, rheumatoid arthritis, and posttraumatic arthritis were included. Variables used for analysis were sex, age, and body mass index (BMI). The Mann-Whitney U and Wilcoxon tests and, Pearson and Spearman correlation statistics were used for analysis of categorical and continuous data respectively. RESULTS: Electrodiagnostic data showed alterations in 17 patients (70.8%). No signs of sciatic nerve injury. The mean preoperative and postoperative WOMAC scores were 40 and 74, respectively (p = 0.0001). Statistical differences were noted in sural sensory amplitude (SSA) and distal amplitude of the tibialis motor nerve in the female group (p=0.007; p=0.036, respectively). The SSA also demonstrated differences in the obese group (p=0.008). In terms of age, both the SSA (Pearson p=0.010 and Spearman p=0.024) and the proximal latency of the peroneal motor nerve (Pearson p=0.026 and Spearman p=0.046) demonstrated a decrease in amplitude and an increase in latency that was inversely related with age. CONCLUSION: According to our subclinical electrophysiological findings, surgeons that use the posterolateral approach in THA procedures must be conscious of the sciatic nerve's vulnerability to reduce possible clinical complications.


Subject(s)
Arthroplasty, Replacement, Hip/adverse effects , Electrodiagnosis , Postoperative Complications/diagnosis , Sciatic Nerve/injuries , Sciatic Neuropathy/diagnosis , Adult , Age Factors , Aged , Arthroplasty, Replacement, Hip/methods , Body Mass Index , Female , Humans , Incidence , Male , Middle Aged , Obesity/complications , Postoperative Complications/epidemiology , Postoperative Complications/etiology , Prospective Studies , Sciatic Neuropathy/epidemiology , Sciatic Neuropathy/etiology , Sural Nerve/physiopathology , Surveys and Questionnaires , Tibial Nerve/physiopathology
6.
J Synchrotron Radiat ; 27(Pt 5): 1415-1429, 2020 Sep 01.
Article in English | MEDLINE | ID: mdl-32876619

ABSTRACT

BioMAX is the first macromolecular crystallography beamline at the MAX IV Laboratory 3 GeV storage ring, which is the first operational multi-bend achromat storage ring. Due to the low-emittance storage ring, BioMAX has a parallel, high-intensity X-ray beam, even when focused down to 20 µm × 5 µm using the bendable focusing mirrors. The beam is tunable in the energy range 5-25 keV using the in-vacuum undulator and the horizontally deflecting double-crystal monochromator. BioMAX is equipped with an MD3 diffractometer, an ISARA high-capacity sample changer and an EIGER 16M hybrid pixel detector. Data collection at BioMAX is controlled using the newly developed MXCuBE3 graphical user interface, and sample tracking is handled by ISPyB. The computing infrastructure includes data storage and processing both at MAX IV and the Lund University supercomputing center LUNARC. With state-of-the-art instrumentation, a high degree of automation, a user-friendly control system interface and remote operation, BioMAX provides an excellent facility for most macromolecular crystallography experiments. Serial crystallography using either a high-viscosity extruder injector or the MD3 as a fixed-target scanner is already implemented. The serial crystallography activities at MAX IV Laboratory will be further developed at the microfocus beamline MicroMAX, when it comes into operation in 2022. MicroMAX will have a 1 µm × 1 µm beam focus and a flux up to 1015 photons s-1 with main applications in serial crystallography, room-temperature structure determinations and time-resolved experiments.

7.
Patient Prefer Adherence ; 13: 981-992, 2019.
Article in English | MEDLINE | ID: mdl-31417243

ABSTRACT

Purpose: Effective health care and patient adherence to their prescribed regimens relies on successful communication between patients and their providers. This study examined mechanisms for optimizing patient-physician communication in subjects with type 2 diabetes, with a focus on optimizing the incorporation of e-clinical technology to improve engagement and communication. Methods: A total of 105 subjects with type 2 diabetes participating in a large US mode equivalency study were surveyed independently of this trial. In addition to demographic information, each subject was queried on their familiarity with and preference for e-clinical technologies. Survey questions focused on mobile technology use, perceptions, and preferences for improving communication and interactions with health care providers. Results: Subjects were diverse in age, sex, education, and ethnicity. Forty nine percent owned a smartphone, and 64% had a computer at home. Most subjects (81%) were interested in using electronic methods (eg, app on a smartphone, email, or text messages) to interact more with physicians between visits. The majority of subjects were interested in using technology to help manage their type 2 diabetes, including 62% favoring communicating with their health-care providers via email and a considerable fraction interested in using smartphones to be provided medication reminders (56%), clinical visit scheduling (55%), and text messaging (49%). Conclusion: Subjects are interested in using electronic methods to increase communication with their physicians and manage their type 2 diabetes. Health-care providers should consider engaging patients with e-clinical technology to increase patient-physician communication and for the ultimate goal of improved health care.

8.
J Synchrotron Radiat ; 26(Pt 2): 393-405, 2019 Mar 01.
Article in English | MEDLINE | ID: mdl-30855248

ABSTRACT

MXCuBE2 is the second-generation evolution of the MXCuBE beamline control software, initially developed and used at ESRF - the European Synchrotron. MXCuBE2 extends, in an intuitive graphical user interface (GUI), the functionalities and data collection methods available to users while keeping all previously available features and allowing for the straightforward incorporation of ongoing and future developments. MXCuBE2 introduces an extended abstraction layer that allows easy interfacing of any kind of macromolecular crystallography (MX) hardware component, whether this is a diffractometer, sample changer, detector or optical element. MXCuBE2 also works in strong synergy with the ISPyB Laboratory Information Management System, accessing the list of samples available for a particular experimental session and associating, either from instructions contained in ISPyB or from user input via the MXCuBE2 GUI, different data collection types to them. The development of MXCuBE2 forms the core of a fruitful collaboration which brings together several European synchrotrons and a software development factory and, as such, defines a new paradigm for the development of beamline control platforms for the European MX user community.

9.
Dalton Trans ; 48(13): 4218-4227, 2019 Mar 26.
Article in English | MEDLINE | ID: mdl-30843571

ABSTRACT

Helical aluminium complexes [Al2X4(µ-nbptam)] (X = Me 1, Et 2), [Al2X4(µ-fbpam)] (R = Me 3, Et 4), [Al3X7(µ-nbptam)] (X = Me 5, Et 6) and [Al3X7(µ-fbpam)] (X = Me 7, Et 8) have been prepared by treatment of scorpionate ligand precursors with two or three equivalents of the corresponding trialkylaluminium derivative. The structures of these complexes have been determined by spectroscopic methods and the X-ray crystal structure of complex 1 has also been established. These complexes have been studied as catalysts for the chemical fixation of carbon dioxide into cyclic carbonates displaying good catalytic activity. When cyclohexene oxide was used as a substrate, polyether-polycarbonate was obtained in a ratio which is highly dependent on the cocatalyst and the catalyst to cocatalyst ratio used.

10.
Inorg Chem ; 58(5): 3396-3408, 2019 Mar 04.
Article in English | MEDLINE | ID: mdl-30735040

ABSTRACT

New bifunctional aluminum complexes have been prepared with the aim of studying the effect of a counterion on the synthesis of cyclic carbonates from epoxides and carbon dioxide (CO2). Neutral ligand 1 was used as a precursor to obtain four novel mesylate, chloride, bromide, and iodide zwitterionic NNO ligands (2-5). The reaction of these ligands with 1 or 2 equiv of AlR3 (R = Me, Et) allowed the synthesis of mono- and bimetallic bifunctional aluminum complexes [AlR2(κ2-mbpzappe)]X [X = Cl, R = Me (6), Et (7); X = Br, R = Me (8), Et (9); X = I, R = Me (10), Et (11)] and [{AlR2(κ2-mbpzappe)}(µ-O){AlR3}]X [X = MeSO3, R = Me (12), Et (13); X = Cl, R = Me (14), Et (15); X = Br, R = Me (16), Et (17); X = I, R = Me (18), Et (19)] via alkane elimination. These complexes were studied as catalysts for the synthesis of cyclic carbonates from epoxides and CO2. Iodide complex 11 showed to be the most active catalyst for terminal epoxides, whereas bromide complex 9 was found to be the optimal catalyst when internal epoxides were used, showing the importance of the nucleophile cocatalyst on the catalytic activity.

11.
Int J Pharm ; 558: 110-119, 2019 Mar 10.
Article in English | MEDLINE | ID: mdl-30639216

ABSTRACT

Bare polycaprolactones with controlled molar mass and dispersity were employed to manufacture biodegradable devices, which were applied for doxorubicin delivery in glioblastoma. Micro- and nanoscale devices were prepared by emulsion formation or by a combination of precipitation and hydrolysis. The carriers were characterized by scanning electron microscopy, dynamic light scattering techniques, thermogravimetric analysis and differential scanning calorimetry. The encapsulation parameters and drug-release profiles are discussed in order to evaluate the influence of different fundamental parameters, such as molar mass and dispersity value, pH, morphology or crystallinity, on the efficiency of the doxorubicin delivery systems. The ability of doxorubicin-loaded micro- and nanoscale devices to induce cellular toxicity in glioblastoma cells was also explored. A cell viability assay against C6 cells of doxorubicin-loaded nanocarriers showed higher cytotoxicity than doxorubicin-loaded microcarriers. In addition, doxorubicin-loaded nanocarriers also showed good antitumor profile in human tumoral cells and improved the security profile in relation to free doxorubicin in non-tumoral cells. Consistent with the assessment study described in this manuscript, the results provide a proof of concept for the suitability of the approach, based on bare polycaprolactone, to local controlled-sustained release of doxorubicin for the treatment of glioblastoma.


Subject(s)
Antibiotics, Antineoplastic/administration & dosage , Central Nervous System Neoplasms/drug therapy , Doxorubicin/administration & dosage , Drug Delivery Systems , Glioblastoma/drug therapy , Polyesters/administration & dosage , Animals , Antibiotics, Antineoplastic/chemistry , Cell Survival/drug effects , Cells, Cultured , Doxorubicin/chemistry , Female , Humans , Macrophages, Peritoneal/drug effects , Mice, Inbred C57BL , Nanoparticles/administration & dosage , Nanoparticles/chemistry , Polyesters/chemistry , Rats, Sprague-Dawley
12.
Inorg Chem ; 58(1): 900-908, 2019 Jan 07.
Article in English | MEDLINE | ID: mdl-30540186

ABSTRACT

A new coordination mode for the hybrid scorpionate/cyclopentadienyl ligand bpzcp, [bpzcp = 2,2-bis(3,5-dimethylpyrazol-1-yl)-1,1-diphenylethylcyclopentadienyl] is observed in iridium complexes. The reaction of the lithium precursor, [Li(bpzcp)(THF)], with a range of [IrCl(diene)]2 compounds leads to an unprecedented binding mode of the hybrid scorpionate/cyclopentadienyl ligand as η5-Cp-coordinated and the formation of Ir(I) derivatives [Ir(η5-Cp-bpzcp)(η4-cod)] (1), [Ir(η5-Cp-bpzcp){η4-CH2═C(Me)C(Me)═CH2}] (2), [Ir(η5-Cp-bpzcp)(η2-coe)2] (3), and [Ir(η5-Cp-bpzcp)(η2-CH2═CH2)2] (4). The Ir(I) complex 4 reacts with CO or bromine to afford the compound [Ir(η5-Cp-bpzcp)(CO)2] (5) and the 18e- Ir(III) complex [Ir(κ-N-η5-Cp-bpzcpBr2)Br2] (6), respectively. Reaction of the iridium compounds (2-4) with CuI or [PdCl2(CH3CN)2] yields the heterobimetallic iridium-copper or iridium-palladium complexes [Ir(η5-Cp-bpzcp){η4-CH2═C(Me)C(Me)═CH2}(µ-bpzcp){CuI(κ2-NN-bpzcp)}] (7), [Ir(η5-Cp-bpzcp)(η2-coe)2}(µ-bpzcp){CuI(κ2-NN-bpzcp)}] (8), [Ir(η5-Cp-bpzcp)(η2-CH2═CH2)2}(µ-bpzcp){CuI(κ2-NN-bpzcp)}] (9), [Ir(η5-Cp-bpzcp)(coe)2}(µ-bpzcp){PdCl2(κ2-NN-bpzcp)}] (10), and [Ir(η5-Cp-bpzcp)(η2-CH2═CH2)2(µ-bpzcp){PdCl2(κ2-NN-bpzcp)}] (11). All products were characterized by spectroscopic methods and the X-ray crystal structures of 1, 2, 3, 4, and 6 were also established.

13.
Dalton Trans ; 47(43): 15391-15398, 2018 Nov 21.
Article in English | MEDLINE | ID: mdl-30306985

ABSTRACT

The titanium complex [TiCp*(thiosal)(thiosalH)] (1) has been synthesised by reaction of [TiCp*Me3], Cp* = η5-C5Me5, with thiosalicylic acid (H2thiosal). Complex 1 reacts with [M(µ-OH)(COD)]2 (M = Rh, Ir) to yield the corresponding early-late heterobimetallic complexes [TiCp*(thiosal)2M(COD)] (M = Rh (2); Ir (3)). Carbon monoxide replaces the COD ligand in 2 and 3 leading to the respective dicarbonyl complexes [TiCp*(thiosal)2M(CO)2] (M = Rh (4); Ir (5)). Compound 4 reacts with PPh3 to yield the monocarbonyl derivative [TiCp*(thiosal)2Rh(CO)(PPh3)] (6). The reaction of compound 1 with LinBu yields the tetrametallic complex [{TiCp*(thiosal)2Li}2(THF)3(H2O)] (7). Compound 7 reacts with [RuCp*Cl(COD)] yielding the heterometallic complex [TiCp*(thiosal)2RuCp*] (8). The molecular structures of compounds 4, 5 and 7 have been studied by X-ray diffraction. From cyclic voltammetric (CV) and square wave voltammetric (SWV) experiments, we observed that attachment of the titanium moiety of precursor 1 to a late transition metal moiety through the sulfur atoms has a significant influence on the reduction behaviour of the Ti(iv) metal centre. Thus, monometallic 1 exhibits an irreversible reduction process at -1.15 V vs. SCE, whereas the CVs of heterobimetallic compounds 2-6 are characterized by the reversible or quasi-reversible one-electron reduction of the Ti(iv)/Ti(iii) system, suggesting a significant stabilization of the Ti(iii) reduced species. Likewise, substitution of the M(COD) diolefin fragment in 2 and 3 by the M(CO)2 carbonyl-containing moiety (in compounds 4 and 5) leads to a significant anodic shift in the titanium E1/2 reduction redox potentials.

14.
Inorg Chem ; 57(19): 12132-12142, 2018 Oct 01.
Article in English | MEDLINE | ID: mdl-30212185

ABSTRACT

The reaction of the highly sterically demanding NNN'-heteroscorpionate protioligands pbptamd-H, tbptamd-H, and phbptamd-H (a) and the low sterically hindered analogs pbpamd-H, tbpamd-H, and phbpamd-H (b), with 1 equiv of AlR3 (R = Me, Et) proceed in high yields to give two families of complexes: the mononuclear dialkyl aluminum bidentate-acetamidinates [AlR2(κ2- N' N')] (κ2- N' N' = pbptamd, R = Me 1, Et 2; tbptamd, R = Me 3, Et 4; phbptamd, R = Me 5, Et 6) and the monodentate-acetamidinates [AlR2(κ2- NN')] (κ2- NN' = tbpamd, R = Me 7; phbpamd, R = Me 8, Et 9). In complexes 7-9, the presence of two possible CH-NH tautomers as low extended π-N-C-N'(sp2)-Al and high extended π-HN-C2-N'(sp2)-Al complexes, respectively, could be identified. Moreover, the reaction of aluminum dimethyls 7 and 8 with ZnMe2 afforded the isolation of the more stable scorpionate zinc monoalkyls [Zn(Me)(κ3- NNN')] ( NNN' = tbpamd 10 and phbpamd 11), through a very unusual ligand exchange process, involving a zinc-to-aluminum transmetalation of an alkyl group. The X-ray crystal structures of 1, 3, 7, and 8, as well as that of 11, confirmed unambiguously the different κ2-arrangements proposed for bi- or monodentate acetamidinate dialkyls 1-6 and 7-9, respectively, the presence of NH tautomer in 7 and 8, and a κ3- NNN' coordination in monoalkyl 11. Density functional theory calculations were used to explore the three different favored κ2-arrangements found in acetamidinate aluminum dialkyls 1-9, the relative stability of both CH-NH tautomers, and the ligand transfer reaction leading to the formation of κ3- NNN' zinc monoalkyls 10 and 11. Interestingly, dialkyls 1, 5, 7, and 8 can act as highly efficient single-component living initiators for the ring-opening polymerization of ε-caprolactone and rac-lactide in mild conditions after hours. These initiators efficiently mediated the immortal polymerization in the presence of excess of benzyl alcohol (up to 20 equiv), as evidenced by the narrow dispersity values and the good agreement between the experimental Mn values and monomer/benzyl alcohol ratios. In addition, the most sterically hindered initiator, 5, exhibits enhanced levels of heteroselectivity on the produced PLAs, reaching Ps values up to 0.70.

15.
ACS Omega ; 3(12): 17581-17589, 2018 Dec 31.
Article in English | MEDLINE | ID: mdl-31458360

ABSTRACT

The optimization of an organoaluminum catalytic system for the copolymerization of epoxides and anhydrides is presented. For this purpose, the influence of different variables in the process, such as catalysts, cocatalyst, solvent, or substrates, has been analyzed. Kinetic studies, a proposal for the catalytic mechanism, and full characterization of the copolymers obtained are also discussed. Finally, a new copolymer, poly(limonene succinate), obtained by the optimized catalytic system is reported.

16.
Dalton Trans ; 46(43): 15107-15117, 2017 Nov 07.
Article in English | MEDLINE | ID: mdl-29068018

ABSTRACT

The preparation of new chiral bis(pyrazol-1-yl)methane-based N,N,O-donor scorpionate ligands in the form of the alcohol compounds bpzampeH (1) {2,2-bis(3,5-dimethylpyrazol-1-yl)-1-[4-(dimethylamino)phenyl]ethanol}, bpzaepeH (2) {2,2-bis(3,5-dimethylpyrazol-1-yl)-1-[4-(diethylamino)phenyl]ethanol}, and bpzimeH (3) {2,2-bis(3,5-dimethylpyrazol-1-yl)-1-[1-methyl-1H-imidazol-2-yl]ethanol} has been carried out by the 1,2-addition reactions of a series of aldehydes. These new chiral heteroscorpionate ligands reacted with [ZnR2] (R = Me, Et, CH2SiMe3) in a 1 : 1 molar ratio in toluene to give the mononuclear monoalkyl zinc complexes [Zn(R)(κ3-NNO)] (4-12). When these reactions were carried out in a 1 : 2 molar ratio the binuclear trisalkyls [Zn(R)(κ2-NNµ-O)Zn(R)2] (13-18) were obtained. The structures of these complexes were elucidated by 1H and 13C{1H} NMR spectroscopy and the X-ray crystal structures of 4 and 5 were also established. Interestingly, alkyl-containing zinc complexes 4-13, 15 and 17 act as efficient single-component initiators for the ring-opening polymerization of rac-lactide at 20 °C to afford PLA materials with low molecular weights in a few hours. The dinuclear trisalkyls showed higher activity in comparison with the mononuclear zinc counterparts, suggesting a cooperative effect of the two remote metals. The narrow dispersity ranges (Mw/Mn = 1.05) of the isolated polymers in conjunction with the linear nature of the number average molecular weight versus conversion plot provided evidence for living behavior. Inspection of the kinetic parameters showed that the propagations have the usual pseudo-first-order dependence on rac-lactide and catalyst concentration. End-group analysis and MALDI-TOF mass spectrometry confirmed that the initiation occurs through nucleophilic attack of the alkyl on the lactide monomer. Microstructural analysis of poly(rac-lactide)s revealed that the most sterically hindered ligand on the alkoxide fragment exerts a moderate influence on the degree of stereoselectivity, with heteroenriched-PLAs (Ps = 0.68) produced at room temperature.


Subject(s)
Coordination Complexes/chemistry , Dioxanes/chemistry , Zinc/chemistry , Catalysis , Crystallography, X-Ray , Ligands , Magnetic Resonance Spectroscopy , Molecular Conformation , Polyesters/chemistry , Polymerization , Stereoisomerism
17.
ChemSusChem ; 10(14): 2886-2890, 2017 07 21.
Article in English | MEDLINE | ID: mdl-28598575

ABSTRACT

A new lanthanum heteroscorpionate complex has shown exceptional catalytic activity for the synthesis of cyclic carbonates from epoxides and carbon dioxide. This catalyst system also promotes the reaction of bio-based epoxides to give an important class of bis(cyclic carbonates) that can be further used for the production of bio-derived non-isocyanate polyurethanes. The catalytic process requires low catalyst loading and mild reaction conditions for the synthesis of a wide range of cyclic carbonates.


Subject(s)
Carbon Dioxide/chemistry , Carbonates/chemistry , Lanthanum/chemistry , Organometallic Compounds/chemistry , Catalysis , Epoxy Compounds/chemistry
18.
Dalton Trans ; 46(20): 6654-6662, 2017 May 23.
Article in English | MEDLINE | ID: mdl-28474015

ABSTRACT

A series of enantiopure alkoxide and thioalkoxide zirconium derivatives [Zr(ER)3(κ3-R,R-fbpza)] (1-6) (E = O, R = CHMe21, CHMeEt 2, CH2SiMe33, 2,6-C6H3Me24, 4-tBuPh 5; E = S, R = 4-tBuPh 6) has been prepared for use as thermally stable and robust initiators in the ROP of rac-lactide. The compounds were prepared by alcoholysis or thioalcoholysis of the tris(amide) precursor [Zr(NMe2)3(κ3-R,R-fbpza)] [R,R-fbpzaH = N-p-fluorophenyl-(1R)-1-[(1R)-6,6-dimethylbicyclo[3.1.1]-2-hepten-2-yl]-2,2-bis(3,5-dimethylpyrazol-1-yl)ethylamine] with ROH and ArEH (E = O, S) in a 1 : 3 molar ratio. The structures of the different compounds were determined by spectroscopic methods and, in addition, the X-ray crystal structure of 6 was also established. Interestingly, the tris(amide) precursor and complexes 2, 5, and 6 act as single-site living initiators for the well-controlled ring-opening polymerization of rac-lactide both in solution and in the melt. These processes produce polymers with medium molecular weights in good agreement with theoretical values and with narrow dispersity ranges. The activity of all initiators increased markedly with temperature and, more importantly, complex 2 exhibits the highest activity reported to date for a group 4-based initiator in the ROP of rac-LA under the industrially preferred melt and solvent-free conditions. Surprisingly, complex 2 is still highly active in the melt when using an unpurified monomer and it shows an unprecedented tolerance to water and impurities (49% conv., 15 min, 130 °C). Microstructural analysis of the poly(rac-lactide)s revealed a moderate heteroactivity in solution, with a Ps value of up to 0.70.

19.
ChemSusChem ; 10(6): 1175-1185, 2017 03 22.
Article in English | MEDLINE | ID: mdl-27863128

ABSTRACT

New neutral and zwitterionic chiral NNO-donor scorpionate ligands 1 and 2 were designed to obtain new mononuclear and dinuclear NNO-heteroscorpionate aluminum complexes. Reaction of 1 with [AlR3 ] (R=Me, Et) in a 1:1 or 1:2 molar ratio afforded the neutral mononuclear alkyl complexes [AlR2 (κ2 -bpzappe)] {R=Me (3), Et (4); bpzappeH=2,2-bis(3,5-dimethylpyrazol-1-yl)-1-[4-(dimethylamino)phenyl]-1-phenylethanol} and bimetallic complexes [{AlR2 (κ2 -bpzappe)}(µ-O){AlR3 }] [R=Me (5), Et (6)]. By reaction of complexes 3-6 with PhCH2 Br, mononuclear and dinuclear cationic aluminum complexes [AlR2 (κ2 -bbpzappe)]Br {R=Me (7), Et (8); bbpzappeH=N-benzyl-4-[2,2-bis(3,5-dimethyl-1H-pyrazol-1-yl)-1-hydroxy-1-phenylethyl]-N,N-dimethylbenzenaminium bromide} and [{AlR2 (κ2 -bbpzappe)}(µ-O){AlR3 }]Br [R=Me (9), Et (10)] were synthesized. Both neutral aluminum complexes in the presence of Bu4 NBr and cationic aluminum complexes were investigated as catalysts for cyclic carbonate formation from epoxides and carbon dioxide. Amongst them, complex 10 was found to be an efficient one-component catalyst for the synthesis of cyclic carbonates from both monosubstituted and internal epoxides and was shown to have broad substrate scope.


Subject(s)
Aluminum/chemistry , Carbon Dioxide/chemistry , Carbonates/chemistry , Epoxy Compounds/chemistry , Hydrocarbons, Chlorinated/chemistry , Carbonates/chemical synthesis , Catalysis , Models, Molecular , Molecular Conformation , Stereoisomerism
20.
Patient Prefer Adherence ; 10: 2171-2179, 2016.
Article in English | MEDLINE | ID: mdl-27822018

ABSTRACT

OBJECTIVES: Electronic data capture is increasingly used to improve collection of patient-reported outcome measures in clinical trials and care. The validation of electronic patient-reported outcome devices requires information on patient preference and ease of use. This study conducted usability testing for a General Symptom Questionnaire and Medication Module™ on a handheld device for subjects with osteoarthritis (OA) to determine whether subjects can report on their symptoms and medication use using an electronic diary. METHODS: Nine subjects with OA participating in a large US mode equivalency study were surveyed independently in this study. Subjects completed a General Symptom Questionnaire and Medication Module™ using the LogPad® LW handheld device. Demographic and technology use information was collected, and the subjects were queried on device usability. RESULTS: Subjects reported that the handheld device was easy to use and that they were able to complete a General Symptom Questionnaire and Medication Module™ with little or no assistance. They did not report any issues with the screen or size of the device. Subjects were willing to travel with the device to complete electronic diaries at home or in public. Participants indicated that they would be able to use the handheld device to answer questions during a clinical trial. Subjects with OA experienced no physical discomfort during completion of either questionnaire. CONCLUSION: The General Symptom Questionnaire and Medication Module™ were usable and acceptable to subjects with OA on a handheld device. This was consistent regardless of previous experience and confidence with technology, despite the potential physical restrictions for an OA cohort.

SELECTION OF CITATIONS
SEARCH DETAIL
...