MOF catalysis in relation to their homogeneous counterparts and conventional solid catalysts

Metal-organic frameworks have recently attracted attention as heterogeneous catalysts due to their high content of metal centres and large surface area and pore volume, along with their impressive topological richness. Therefore, many studies describing the use of MOFs as heterogeneous Lewis acid catalysts have been published. In this regard, these efforts have been directed towards probing the catalytic activity. Further information is required in terms of kinetic parameters and comparison of performance with their homogeneous counterparts, or other conventional heterogeneous catalysts. Here we have attempted to put MOFs into perspective with respect to their homogeneous counterparts and more conventional heterogeneous catalysts to show their advantages and limitations. We have exemplified a number of reactions reported in the literature wherein MOFs have been used as catalysts, and we have carried them out using homogeneous counterparts, i.e. benzoates and acetates, and other well defined conventional solid catalysts. The activities and selectivities of the catalysts are compared and then put into perspective on the basis of kinetic parameters, such as turnover numbers and turnover frequencies. Additionally, we illustrate using selected examples what the potential advantages of MOF catalysts could be, and how they may outperform the potential of other solid catalysts.This work was supported by the Spanish Government (Consolider Ingenio 2010-MULTICAT (CSD2009-00050) and MAT2011-29020-C02-01). P.G.-G. thanks ITQ for a contract. M.M. thanks the Alexander von Humboldt Foundation for a Feodor Lynen Postdoctoral Scholarship. The Severo Ochoa program is gratefully acknowledged.García García, P.; Müller, M.; Corma Canós, A. (2014). MOF catalysis in relation to their homogeneous counterparts and conventional solid catalysts. Chemical Science. 5(8):2979-3007. https://doi.org/10.1039/c4sc00265bS297930075

25th anniversary article: Engineering hydrogels for biofabrication

With advances in tissue engineering, the possibility of regenerating injured tissue or failing organs has become a realistic prospect for the first time in medical history. Tissue engineering - the combination of bioactive materials with cells to generate engineered constructs that functionally replace lost and/or damaged tissue - is a major strategy to achieve this goal. One facet of tissue engineering is biofabrication, where three-dimensional tissue-like structures composed of biomaterials and cells in a single manufacturing procedure are generated. Cell-laden hydrogels are commonly used in biofabrication and are termed bioinks. Hydrogels are particularly attractive for biofabrication as they recapitulate several features of the natural extracellular matrix and allow cell encapsulation in a highly hydrated mechanically supportive three-dimensional environment. Additionally, they allow for efficient and homogeneous cell seeding, can provide biologically-relevant chemical and physical signals, and can be formed in various shapes and biomechanical characteristics. However, despite the progress made in modifying hydrogels for enhanced bioactivation, cell survival and tissue formation, little attention has so far been paid to optimize hydrogels for the physico-chemical demands of the biofabrication process. The resulting lack of hydrogel bioinks have been identified as one major hurdle for a more rapid progress of the field. In this review we summarize and focus on the deposition process, the parameters and demands of hydrogels in biofabrication, with special attention to robotic dispensing as an approach that generates constructs of clinically relevant dimensions. We aim to highlight this current lack of effectual hydrogels within biofabrication and initiate new ideas and developments in the design and tailoring of hydrogels. The successful development of a printable hydrogel that supports cell adhesion, migration, and differentiation will significantly advance this exciting and promising approach for tissue engineering.</p

Effects of once-weekly exenatide on cardiovascular outcomes in type 2 diabetes

BACKGROUND: The cardiovascular effects of adding once-weekly treatment with exenatide to usual care in patients with type 2 diabetes are unknown. METHODS: We randomly assigned patients with type 2 diabetes, with or without previous cardiovascular disease, to receive subcutaneous injections of extended-release exenatide at a dose of 2 mg or matching placebo once weekly. The primary composite outcome was the first occurrence of death from cardiovascular causes, nonfatal myocardial infarction, or nonfatal stroke. The coprimary hypotheses were that exenatide, administered once weekly, would be noninferior to placebo with respect to safety and superior to placebo with respect to efficacy. RESULTS: In all, 14,752 patients (of whom 10,782 [73.1%] had previous cardiovascular disease) were followed for a median of 3.2 years (interquartile range, 2.2 to 4.4). A primary composite outcome event occurred in 839 of 7356 patients (11.4%; 3.7 events per 100 person-years) in the exenatide group and in 905 of 7396 patients (12.2%; 4.0 events per 100 person-years) in the placebo group (hazard ratio, 0.91; 95% confidence interval [CI], 0.83 to 1.00), with the intention-to-treat analysis indicating that exenatide, administered once weekly, was noninferior to placebo with respect to safety (P<0.001 for noninferiority) but was not superior to placebo with respect to efficacy (P=0.06 for superiority). The rates of death from cardiovascular causes, fatal or nonfatal myocardial infarction, fatal or nonfatal stroke, hospitalization for heart failure, and hospitalization for acute coronary syndrome, and the incidence of acute pancreatitis, pancreatic cancer, medullary thyroid carcinoma, and serious adverse events did not differ significantly between the two groups. CONCLUSIONS: Among patients with type 2 diabetes with or without previous cardiovascular disease, the incidence of major adverse cardiovascular events did not differ significantly between patients who received exenatide and those who received placebo