ZIF-8 degrades in cell media,serum, and some—but not all—common laboratory buffers

ABSTRACT

Drug delivery using metal-organic frameworks (MOF) has elicited interest in their biocompatibility; however, few studies have been conducted on their stability in common buffers, cell media, and blood proteins. In particular, the use of ZIF-8, a MOF interconnected by Zn and methylimidazole, has been frequently employed. In this study, we tested single crystals of ZIF-8 with common laboratory buffers, cell media, and serum, and noted several issues. Buffers containing phosphate and bicarbonate alter the appearance and composition of ZIF-8; however, these buffers do not appear to cause cargo to leak out even when the ZIF-8 itself is displaced by phosphates. On the other hand, serum dissolves ZIF-8, causing premature cargo release. Our results show that ZIF-8 undergoes surface chemistry changes that may affect the interpretation of cellular uptake and cargo release data. On the other hand, it provides a rational explanation as to how ZIF-8 neatly dissolves in vivo.     

Regularity of Local Times Associated with Volterra–Lévy Processes and Path-Wise Regularization of Stochastic Differential Equations

Journal of Theoretical Probability - We investigate the space-time regularity of the local time associated with Volterra–Lévy processes, including Volterra processes driven by $$\alpha...     

Strong vertex corrections from weak disorder in 2D d-wave superconductors

We show that weak static random potentials have pronounced effects on the quasiparticle states of a 2Dd-wave superconductor close to a node. We prove that the vertex correction coming from the simplest crossed diagram is important even for a nonmagnetic potential. The leading frequency and momentum dependent logarithmic singularities in the self-energy are calculated exactly to second order in perturbation theory. The self-energy corrections lead to a modified low energy density of states which depends strongly on the type of random potential and which can be measured in experiments. There is an exceptional case for a potential with extremely local scatterers and opposite nodes separated by (, ) where an exact cancelation takes place eliminating the leading frequency dependent singularity in the simplest crossed diagram. A comparison of the perturbative results with a self-consistent CPA (coherent potential approximation) for the nonmagnetic disorder reveals qualitative differences in the self-energy at the smallest energies which are due to the neglectance of vertex corrections in CPA.     

The Radical Anions of N,N′-Dicyanoquinone Diimines,a New Class of Electron Acceptors

The radical anions of 12 N,N′-dicyanoquinone diimines, a new class of electron acceptors, hace been characterized by their hyperfine data with the use of ESR and ENDOR spectroscopy. The largest coupling constant (0.30–0.45 mT), due to the two ¹⁴N nuclei in the exocyclic positions, gives rise to a conspicuous broadening of the peripheral ESR lines by an incomplete averaging of the hyperfine anisotropy. The most plausible interpretation of the experimental results for the radical anions of N,N′-dicyano- 1,4-benzoquinone diimine ( 1 ) and N,N′-Dicyano-9,10-anthraquinone diimine ( 9 ) is in terms of both ‘syn’- and ‘anti’-configurations contributing to the ESR and ENDOR spectra and having equal proton- and ¹⁴N-coupling constants. The π-spin distribution in the radical anions of N,N′-dicyanoquinone diimines is compared with those in the analogous ions of tetracyanoquinodimethanes and quinones.     

LCAO-MO-berechnungen an schwefelhaltigen π-elektronensystemen—XXXIV : Nichtbindende S,S-wechselwirkung in polymethinfarbstoffen

Sulfur-containing polymethine dyes exhibit anomalous chromophoric properties. The vinylene shift of the first two homologues is often considerably larger or smaller than the shift between higher members of the series. Moreover, the absorption wavelengths of non-symmetrical dyes with sulfur-containing groups, as calculated by the mean value rule differ from the experimental data, but not in the predicted manner.This deviation is caused by an interannular no-bond SS-interaction in the monomethine ion. This conclusion is supported by the spectra of appropriately-substituted dyes and is substantiated by theoretical considerations. Starting from the well-known symmetry properties of polymethine MO's the simple PMO-method reproduces correctly the effects of the p_π-type overlap between atomic orbitals of adjacent S atoms at long wavelength absorptions: The SS-interactions lead to a hypsochromic shift in monomethines with (4N + 2)π-electrons (N = 1,2…) and to a bathochromic shift in monomethines with (4N)π-electrons.     

Strukturuntersuchungen an 4-methyl-6-phenyl-2-(thiobenzoylmethylen)-2H-thiapyran

The structure of 4-methyl-6-phenyl-2-(thiobenzoylmethylene)-2H-thiapyran (1) was investigated by ESCA, X-ray analysis and quantum chemical calculations. The no-bond interaction between the sulphur atoms (R_s…s = 3.000(1) Å) is caused by π-type interaction rather than by Coulomb-type interaction.     

The Radical Cations of 4,5,7,13,15,16-Hexamethyl- and 4,5,7,8,12,13,15,16-Octamethyl [2.2]paracyclophane

4,5,7,13,15,16-Hexamethyl- (3) and 4,5,7,8,12,13,15,16-octamethyl[2.2]paracyclophane (4) have been oxidized to their radical cations in solution under relatively mild conditions. Substantial hyperfine splittings in the ESR. spectra of 3⊕. and 4⊕. arise from the methyl protons, whereas those from methylene protons are very small. This result indicates that the ethano bridges, unlike the methyl substituents, are rather ineffective in delocalizing the positive charge in 3⊕. and 4⊕. It is in line with the interpretation proposed previously to rationalize the gas-phase ionization potentials of multiply bridged [2_N]cyclophanes and methyl derivatives of [2.2]paracyclophane. The π-spin distributions in 3⊕. and 4⊕. are discussed in terms of a simple model in which the singly occupied orbitals are represented as the antibonding combinations of two benzene HOMO's.