Solid-state Nuclear Magnetic Resonance Studies Research Articles

Enhanced Water Solubility and Oral Bioavailability of Paclitaxel Crystal Powders through an Innovative Antisolvent Precipitation Process: Antisolvent Crystallization Using Ionic Liquids as Solvent.

Paclitaxel (PTX) is a poor water-soluble antineoplastic drug with significant antitumor activity. However, its low bioavailability is a major obstacle for its biomedical applications. Thus, this experiment is designed to prepare PTX crystal powders through an antisolvent precipitation process using 1-hexyl-3-methylimidazolium bromide (HMImBr) as solvent and water as an antisolvent. The factors influencing saturation solubility of PTX crystal powders in water in water were optimized using a single-factor design. The optimum conditions for the antisolvent precipitation process were as follows: 50 mg/mL concentration of the PTX solution, 25 °C temperature, and 1:7 solvent-to-antisolvent ratio. The PTX crystal powders were characterized via scanning electron microscopy, Fourier transform infrared spectroscopy, high-performance liquid chromatography–mass spectrometry, X-ray diffraction, differential scanning calorimetry, thermogravimetric analysis, Raman spectroscopy, solid-state nuclear magnetic resonance, and dissolution and oral bioavailability studies. Results showed that the chemical structure of PTX crystal powders were unchanged; however, precipitation of the crystalline structure changed. The dissolution test showed that the dissolution rate and solubility of PTX crystal powders were nearly 3.21-folds higher compared to raw PTX in water, and 1.27 times higher in artificial gastric juice. Meanwhile, the bioavailability of PTX crystal increased 10.88 times than raw PTX. These results suggested that PTX crystal powders might have potential value to become a new oral PTX formulation with high bioavailability.

Revealing Molecular Mechanisms in Hierarchical Nanoporous Carbon via Nuclear Magnetic Resonance

Author(s): Mao, H; Tang, J; Xu, J; Peng, Y; Chen, J; Wu, B; Jiang, Y; Hou, K; Chen, S; Wang, J; Lee, HR; Halat, DM; Zhang, B; Chen, W; Plantz, AZ; Lu, Z; Cui, Y; Reimer, JA | Abstract: Hierarchical nanoporous carbons combining pore sizes of different length scales are highly important for separation processes. However, critical questions remain regarding the hierarchical structure regulation and the molecular mechanisms of gaseous adsorbate uptake and interactions within the hierarchical nanoporous carbons. These materials present characterization challenges in that there are no experimental techniques that can elucidate the molecular mechanisms of the organic compounds and CO within the materials. We deployed multidimensional solid-state nuclear magnetic resonance (NMR) to generate maps of guest-framework interactions as a function of adsorbate concentrations and adsorption times. The NMR spectra provide insight toward the design of effective hierarchical pore structures. Our materials show a high volatile organic compounds/CO physisorption capacity, which reveals promising application to carbon-capture strategies to mitigate global warming. 2 2

Benzene Adsorbed on Activated Carbon: A Comprehensive Solid-State Nuclear Magnetic Resonance Study of Interactions with the Pore Surface and Molecular Motions

Benzene-d6 and cyclohexane-d12 have been adsorbed on the surface within the pores of high-surface-area activated carbon (AC). Their molecular motions have been characterized by variable-temperature...

New Li10GeP2S12 Structure Ordering and Li-Ion Dynamics Unveiled in Li4GeS4-Li3PS4 Superionic Conductors: A Solid-State Nuclear Magnetic Resonance Study.

The fast Li-ion pathways in crystals contribute to superionic conductivity-extraordinarily high ionic conductivity-of the Li10GeP2S12 (LGPS) structure. Composition tuning is expected to improve the conductivity. The phase behavior, microstructure, and ion dynamics of a series of solid solutions of xLi4GeS4-yLi3PS4 (4/1 ≥ x/y ≥ 1/2) were studied by multiple 7Li and 31P solid-state NMR methods. Li10GeP2S12 (Ge/P = x/y = 1/2) is the smallest x/y of the disordered LGPS structure. When the Ge/P ratio increases, the room-temperature Li ionic conductivity first increases to a maximum around x/y = 1/1.2 and then decreases. Meanwhile, a disordered LGPS structure transforms into an ordered LGPS' structure synchronously with conductivity reduction. The Li4GeS4-Li3PS4 phase diagram with the order-disorder structure transition was reconstructed accordingly. Both ordered LGPS' and disordered LGPS exhibit similar two-dimensional (2D) and one-dimensional (1D) Li diffusion paths. But the disordered LGPS structure is conducive to fast ionic conductivity, rooted in its fast 2D Li+ diffusion in the ab-plane rather than 1D diffusion along the c-axis. Two high-temperature relaxation processes are observed in the LGPS' structure, suggesting heterogeneous 2D jumps of rapid and slow rates, whereas only a single homogeneous 2D jump process was found in the LGPS structure. Our findings provide insight into understanding the relationship between structure order (or disorder) and ionic conductivity of superionic materials, offering guidelines for optimizing ionic conductivity for extensive solid electrolyte materials rather than LGPS materials.

Structural Characterization of Cardiac Ex Vivo Transthyretin Amyloid: Insight into the Transthyretin Misfolding Pathway In Vivo.

Structural characterization of misfolded protein aggregates is essential to understanding the molecular mechanism of protein aggregation associated with various protein misfolding disorders. Here, we report structural analyses of ex vivo transthyretin aggregates extracted from human cardiac tissue. Comparative structural analyses of in vitro and ex vivo transthyretin aggregates using various biophysical techniques revealed that cardiac transthyretin amyloid has structural features similar to those of in vitro transthyretin amyloid. Our solid-state nuclear magnetic resonance studies showed that in vitro amyloid contains extensive nativelike β-sheet structures, while other loop regions including helical structures are disrupted in the amyloid state. These results suggest that transthyretin undergoes a common misfolding and aggregation transition to nativelike aggregation-prone monomers that self-assemble into amyloid precipitates in vitro and in vivo.

Nature of the Surface Intermediates Formed from Methane on Cu-ZSM-5 Zeolite: A Combined Solid-State Nuclear Magnetic Resonance and Density Functional Theory Study

The intermediates formed upon the interaction of methane with Cu-modified ZSM-5 zeolites (Cu/H-ZSM-5) have been analyzed with solid-state NMR spectroscopy and DFT methods. Methane activation by Cu/...

Study of xylan and cellulose interactions monitored with solid-state NMR and QCM-D

Abstract Development of physical properties of bleached eucalyptus kraft pulp is typically based on the refining process. However, many studies have reported that xylan deposition is a viable alternative. As the mechanisms of xylan and cellulose interactions are not clear, the main goal of this study was to achieve a better understanding of these interactions. Considering that a sample of pulp enriched with xylan is a very complex matrix, a model system was developed. Cellulosic thin films were prepared by spincoating and the Langmuir-Schaefer (LS) method from trimethylsilylcellulose (TMSC). Their interactions with xylan were analyzed using the quartz crystal microbalance with dissipation (QCM-D) monitoring technique. The topological changes on cellulose were studied using atomic force microscopy (AFM). For the 13C solid-state nuclear magnetic resonance (NMR) studies, samples were prepared using commercial microcrystalline cellulose (MCC) and xylan. The xylan was extracted from bleached birch kraft pulp using a cold caustic extraction (CCE) method. The QCM-D monitoring showed deposition only with higher concentrations of xylan solution (1 mg · l−1) for the LS method. The AFM images showed that xylan deposits as agglomerates on the cellulose surface, and the NMR experiments showed that there are interactions for the more ordered region of the cellulose fiber and for the less-ordered region.

47,49Ti solid-state NMR and DFT study of Ziegler-Natta catalyst: Adsorption of TiCl4 molecule onto the surface of MgCl2

In Ti-based Ziegler-Natta catalysts (ZNCs), disagreements exist concerning which lateral surface of the MgCl2 support adsorbs Ti species so as to be an active site for the catalysis of polymerization. In the present paper, we investigated the local structure of TiCl4 adsorbed onto the surface of MgCl2 by 47,49Ti solid-state nuclear magnetic resonance (NMR) spectra at 21.8 T along with density functional theory (DFT) calculations. The magic-angle-spinning NMR spectrum of the TiCl4/MgCl2 adduct sample prepared by 20 h of milling, which exhibited broadened and shifted peaks compared to that of the sample without milling, was simulated by a Czjzek model considering the distribution of quadrupole interaction parameters. The electric field gradient and chemical shielding tensors of 49Ti were obtained via DFT calculations for model molecules of TiCl4, 2TiCl4, and Ti2Cl8 adsorbed onto the (110), (104), and (104)-step defect surfaces of MgCl2. By comparing the obtained NMR parameters, the 47,49Ti NMR spectrum of the milled sample was assigned to TiCl4 adsorbed onto the (104) surface of MgCl2, which may not be a principal component of adsorption.

Monomeric Copper(II) Sites Supported on Alumina Selectively Convert Methane to Methanol.

Monomeric CuII sites supported on alumina, prepared using surface organometallic chemistry, convert CH4 to CH3 OH selectively. This reaction takes place by formation of CH3 O surface species with the concomitant reduction of two monomeric CuII sites to CuI , according to mass balance analysis, infrared, solid-state nuclear magnetic resonance, X-ray absorption, and electron paramagnetic resonance spectroscopy studies. This material contains a significant fraction of Cu active sites (22 %) and displays a selectivity for CH3 OH exceeding 83 %, based on the number of electrons involved in the transformation. These alumina-supported CuII sites reveal that C-H bond activation, along with the formation of CH3 O- surface species, can occur on pairs of proximal monomeric CuII sites in a short reaction time.

Solid-state nuclear magnetic resonance study of setting mechanism of β-tricalcium phosphate—inositol phosphate composite cements

Solid-state nuclear magnetic resonance (NMR) spectroscopy is a technique, which can be used to provide insight into the chemical structure of non-crystalline and crystalline materials. Hence, the present study aimed to elucidate the setting mechanism of CPC, which was fabricated using β-tricalcium phosphate (β-TCP)—inositol phosphate (IP6) composite powder using NMR In addition, the effect of IP6 on the local chemical structure of the β-TCP-IP6 composite powder and its hardened cement would also be investigated. The 1H→31P heteronuclear correlation NMR spectrum revealed that an amorphous hydrated layer, along with small amount of hydroxyapatite (HA) was formed on the surface of β-TCP during the ball-milling process. Results demonstrated that the IP6 in the hydrated layer on the surface of β-TCP inhibited the formation of HA. Moreover, the setting reaction of the cement was mainly triggered by the dissolution of the amorphous hydrated layer on β-TCP surface, and subsequent precipitation, followed by the inter-entanglement between the HA crystals on the β-TCP.

NMR Crystallography at Fast Magic-Angle Spinning Frequencies: Application of Novel Recoupling Methods

Chemical characterisation of active pharmaceutical compounds can be challenging, especially when these molecules exhibit tautomeric or desmotropic behaviour. The complexity can increase manyfold if these molecules are not susceptible to crystallisation. Solid-state NMR has been employed effectively for characterising such molecules. However, characterisation of a molecule is just a first step in identifying the differences in the crystalline structure. 1 H solid-state Nuclear Magnetic Resonance (ssNMR) studies on these molecules at fast magic-angle-spinning frequencies can provide a wealth of information and may be used along with ab initio calculations to predict the crystal structure in the absence of X-ray crystallographic studies. In this work, we attempted to use solid-state NMR to measure 1 H - 1 H distances that can be used as restraints for crystal structure calculations. We performed studies on the desmotropic forms of albendazole.

1H and 93Nb Solid-State NMR and IR Study of Acidity of Nanodisperse Nb2O5·nH2O

Niobium oxide hydrate is a promising material for various heterogeneous catalytic processes due to its strong acidity and stability in aqueous medium. While different synthesis conditions may lead to various particle morphologies, the effect of morphology of Nb2O5·nH2O particles on their acidic properties is not fully understood yet. In this paper, we have successfully synthesized and characterized nanodisperse niobium oxide hydrate. Using infrared (IR) spectroscopy, we demonstrated that the sample exhibits strong Bronsted acidity close in strength to sulfuric acid. Furthermore, solid-state nuclear magnetic resonance (NMR) spectroscopy in combination with ab initio calculations gave additional insight into the nature of strong acidic sites and proved to be a useful tool for identification of acidic sites in Nb2O5·nH2O systems. Thus, we have shown that it is not necessary to follow difficult high-temperature solid-state processes or processes with ammonia, which often contaminates the material, to synthesize highly acidic nanodisperse Nb2O5·nH2O.

Labelling strategy and membrane characterization of marine bacteria Vibrio splendidus by in vivo2H NMR

Vibrio splendidus is a marine bacterium often considered as a threat in aquaculture hatcheries where it is responsible for mass mortality events, notably of bivalves' larvae. This bacterium is highly adapted to dynamic salty ecosystems where it has become an opportunistic and resistant species. To characterize their membranes as a first and necessary step toward studying bacterial interactions with diverse molecules, we established a labelling protocol for in vivo2H solid-state nuclear magnetic resonance (SS-NMR) analysis of V. splendidus. 2H SS-NMR is a useful tool to study the organization and dynamics of phospholipids at the molecular level, and its application to intact bacteria is further advantageous as it allows probing acyl chains in their natural environment and study membrane interactions. In this study, we showed that V. splendidus can be labelled using deuterated palmitic acid, and demonstrated the importance of surfactant choice in the labelling protocol. Moreover, we assessed the impact of lipid deuteration on the general fitness of the bacteria, as well as the saturated-to-unsaturated fatty acid chains ratio and its impact on the membrane properties. We further characterize the evolution of V. splendidus membrane fluidity during different growth stages and relate it to fatty acid chain composition. Our results show larger membrane fluidity during the stationary growth phase compared to the exponential growth phase under labelling conditions - an information to take into account for future in vivo SS-NMR studies. Our lipid deuteration protocol optimized for V. splendidus is likely applicable other microorganisms for in vivo NMR studies.

Aluminum Oxide Thin Films from Aqueous Solutions: Insights from Solid-State NMR and Dielectric Response

Here, we employ a combination of 27Al solid-state nuclear magnetic resonance (SSNMR) and conventional spectroscopic and microscopic techniques to investigate the structural evolution of aqueous aluminum precursors to a uniform and smooth aluminum oxide film. The route involves no organic ligands and relies on dehydration, dehydroxylation, and nitrate loss for condensation and formation of the three-dimensional aluminum oxide structure. Local chemical environments are tracked as films evolve over the temperature range 200–1100 °C. 27Al SSNMR reveals that Al centers are predominantly four- and five-coordinate in amorphous films annealed between 200 and 800 °C and four- and six-coordinate in crystalline phases that form above 800 °C. The Al coordination of the aqueous-deposited aluminum oxide films are compared to data from SSNMR studies on vapor-phase-deposited aluminum oxide thin films. Additionally, dielectric constants of aluminum oxide-based capacitors are measured and correlated with the SSNMR results. Aluminum oxide is an important material for protective coatings, catalysis, and microelectronic applications. For the latter application, amorphous materials are preferred, but a lack of long-range order complicates structural characterization and determination of structure–property relationships. Solution deposition approaches are attractive alternatives to traditional vapor-phase deposition methods because precursors are commonly stable in air, and they enable printing and direct lithographic patterning on common semiconductor wafers as well as large-area and flexible substrates—useful for scale-up to applications in windows and photovoltaic devices.

Amyloid-β fibrils assembled on ganglioside-enriched membranes contain both parallel β-sheets and turns

Some protein and peptide aggregates, such as those of amyloid-β protein (Aβ), are neurotoxic and have been implicated in several neurodegenerative diseases. Aβ accumulates at nanoclusters enriched in neuronal lipids called gangliosides in the presynaptic neuronal membrane, and the resulting oligomeric and/or fibrous forms accelerate the development of Alzheimer's disease. Although the presence of Aβ deposits at such nanoclusters is known, the mechanism of their assembly and the relationship between Aβ secondary structure and topography are still unclear. Here, we first confirmed by atomic force microscopy that Aβ40 fibrils can be obtained by incubating seed-free Aβ40 monomers with a membrane composed of sphingomyelin, cholesterol, and the ganglioside GM1. Using Fourier transform infrared (FTIR) reflection-absorption spectroscopy, we then found that these lipid-associated fibrils contained parallel β-sheets, whereas self-assembled Aβ40 molecules formed antiparallel β-sheets. We also found that the fibrils obtained at GM1-rich nanoclusters were generated from turn Aβ40 Our findings indicate that Aβ generally self-assembles into antiparallel β-structures but can also form protofibrils with parallel β-sheets by interacting with ganglioside-bound Aβ. We concluded that by promoting the formation of parallel β-sheets, highly ganglioside-enriched nanoclusters help accelerate the elongation of Aβ fibrils. These results advance our understanding of ganglioside-induced Aβ fibril formation in neuronal membranes and may help inform the development of additional therapies for Alzheimer's disease.

Structural Prediction of the Dimeric Form of the Mammalian Translocator Membrane Protein TSPO: A Key Target for Brain Diagnostics.

Positron emission tomography (PET) radioligands targeting the human translocator membrane protein (TSPO) are broadly used for the investigations of neuroinflammatory conditions associated with neurological disorders. Structural information on the mammalian protein homodimers—the suggested functional state of the protein—is limited to a solid-state nuclear magnetic resonance (NMR) study and to a model based on the previously-deposited solution NMR structure of the monomeric mouse protein. Computational studies performed here suggest that the NMR-solved structure in the presence of detergents is not prone to dimer formation and is furthermore unstable in its native membrane environment. We, therefore, propose a new model of the functionally-relevant dimeric form of the mouse protein, based on a prokaryotic homologue. The model, fully consistent with solid-state NMR data, is very different from the previous predictions. Hence, it provides, for the first time, structural insights into this pharmaceutically-important target which are fully consistent with experimental data.

Probing the structure of Fe-free model basaltic glasses: A view from a solid-state 27Al and 17O NMR study of Na-Mg silicate glasses, Na2O-MgO-Al2O3-SiO2 glasses, and synthetic Fe-free KLB-1 basaltic glasses

The extent of structural disorder in multi-component basaltic (mafic) melts with varying compositions (particularly, Mg content) and the formation depth has not been well understood. Here, we explore the structure of Mg-rich silicate glasses including Na-Mg silicate glasses, NaO-MgO-Al2O3-SiO2 (NMAS) glasses in a nepheline (NaAlSiO4)-forsterite (Mg2SiO4)-quartz (SiO2) eutectic composition, and synthetic equivalents of basaltic glasses generated by partial melting of upper mantle peridotite (KLB-1) in a multi-component CaO-MgO-Na2O-K2O-Al2O3-TiO2-SiO2 system using high-resolution solid-state nuclear magnetic resonance (NMR). The 2-dimensional (2D) 17O 3Q (triple quantum) magic angle spinning (MAS) NMR spectra for those multi-component glasses revealed the nature of diverse aspects of structural disorder. Non-bridging oxygens (NBOs) apparently prefer proximity toward Ca2+ and Mg2+, whereas bridging oxygens (BOs) prefer to be near Na+, confirming a stronger interaction between NBOs and high field-strength cations in multi-component basaltic melts. The changes of oxygen configurations with increasing Mg contents provide implications for the structural evolution of basaltic melts with varying formation depth. Thus, while the pressure effect remains to be explored, considering the changes in melt composition alone, the NBO fraction of the KLB-1 basaltic melts increases with increasing melting depth of KLB-1 peridotite.The 27Al 3QMAS NMR spectra for multi-component KLB-1 basaltic glasses reveal non-negligible fraction of [5]Al that increases with increasing Mg content. The fraction of [5]Al in natural basaltic magma is expected to increase with melting depth of KLB-1 peridotite. The 27Al NMR quadrupolar coupling constant for [4]Al in multi-component silicate glasses systematically increases with Mg content, indicating an increase of the topological distortion (variation of bond angle and length distribution and network distortion) around [4]Al in the basaltic glasses. The observed increase in the extent of structural disorder in basaltic melts with Mg content may increase the overall configurational and topological entropy. While further confirmation is necessary, the changes in melt polymerization observed from 17O NMR spectra and network disorder around Al imply the decrease in melt viscosity in the complex silicate melts with varying formation depth of KLB-1 basaltic melts.

Rubber-Filler Interactions in Polyisoprene Filled with In Situ Generated Silica: A Solid State NMR Study.

In this paper we used high- and low-resolution solid state Nuclear Magnetic Resonance (NMR) techniques to investigate a series of polyisoprene samples filled with silica generated in situ from tetraethoxysilane by sol-gel process. In particular, 1H spin-lattice and spin-spin relaxation times allowed us to get insights into the dynamic properties of both the polymer bulk and the bound rubber, and to obtain a comparative estimate of the amount of bound rubber in samples prepared with different compositions and sol-gel reaction times. In all samples, three fractions with different mobility could be distinguished by 1H T2 and ascribed to loosely bound rubber, polymer bulk, and free chain ends. The amount of bound rubber was found to be dependent on sample preparation, and it resulted maximum in the sample showing the best dispersion of silica domains in the rubber matrix. The interpretation of the loosely bound rubber in terms of “glassy” behaviour was discussed, also on the basis of 1H T1 and T1ρ data.

(Invited) Lithium Ion Conductors – between Model Systems and Battery Materials

Lithium ion conductors continue to attract huge attention mainly due to the need for improved Li ion batteries, although “post-Li” energy storage systems are also being explored. In any case, basic research dealing with, e.g., the elementary ion jump process, the dimensionality of diffusion or the influence of structural disorder – besides being a field in its own right – is indispensable for those applications, too. Here, exemplary results of our group on Li ion conductors are reviewed. Interestingly, materials used as model systems for basic questions quite often are also potential battery materials, i.e. solid electrolytes or electrodes, and vice versa. An early example of a cathode material has been the intercalation compound LixTiS2 which turned out to be a model system for two-dimensional Li diffusion, involving a unique jump process over many decades, as was proven by a combination of nuclear magnetic resonance (NMR) techniques. Besides the layer-structured also the cubic modification as well as nanocrystalline and amorphous forms were examined with respect to dimensionality and disorder effects.. Anode materials studied by us primarily from a fundamental point of view have been Li x C6 (0<x≤1), Li4+x Ti5O12 (0<x<3) and, as one of the silicides, Li12Si7. In Li12Si7 very fast quasi one-dimensional Li diffusion was detected. Among the potential electrolytes for all-solid-state Li ion batteries, Li7La3Zr2O12 was investigated in some detail also with respect to the influence of doping and defects on Li diffusivity. The examples to be presented extensively involve NMR, which now is an established materials science method for Li ion dynamics [1, 2], but also impedance spectroscopy [3], mass spectrometry [4] and neutron reflectometry [5] have been applied in the Li ion transport studies.[1] C. V. Chandran, P. Heitjans, Solid-State NMR Studies of Lithium Ion Dynamics Across Materials Classes, Annual Reports on NMR Spectroscopy 89 (2016) 1-102.[2] K. Volgmann, V. Epp, J. Langer, B. Stanje, J. Heine, S. Nakhal, M. Lerch, M. Wilkening, P. Heitjans, Solid-State NMR to Study Translational Li Ion Dynamics in Solids with Low-Dimensional Diffusion Pathways, Z. Phys. Chem. 231 (2017) 1215–1241. [3] J. Rahn, E. Hüger, L. Dörrer, B. Ruprecht, P. Heitjans, H. Schmid, Li Self-Diffusion in Lithium Niobate Single Crystals at Low Temperatures, Phys. Chem. Chem. Phys. 116 (2012) 2427–2433. [4] A.-M. Welsch, H. Behrens, I. Horn, S. Roß, P. Heitjans, Self-Diffusion of Lithium in LiAlSi2O6 Glasses Studied Using Mass Spectrometry, J. Phys. Chem. A 116 (2012) 309–318. [5] F. Strauß, E. Hüger, P. Heitjans, T. Geue, J. Stahn, H. Schmidt, Li Permeation through Thin Lithium-Silicon Films for Battery Applications Investigated by Neutron Reflectometry, Energy Technology 12 (2016) 1582–1587.

Comparison of the knitted silk vascular grafts coated with fibroin sponges prepared using glycerin, poly(ethylene glycol diglycidyl ether) and poly(ethylene glycol) as porogens

Development of a small-diameter artificial vascular graft is urgent because existing materials often occlude within a short time. We have shown that small-diameter vascular graft using Bombyx mori silk fibroin is a potential candidate. Silk fibroin grafts are fabricated by coating silk fibroin on the knit tube prepared from silk fibroin fibers. However, there is a serious problem that the coated silk fibroin portion hardens when alcohol is used for insolubilization of the coated silk fibroin. This hardening prevents the desired biodegradation of the coated silk fibroin. In this study, we improved the silk fibroin coating method of the knit silk fibroin tube. Namely, the silk fibroin sponge coating was performed using glycerin, poly(ethylene glycol diglycidyl ether) or poly(ethylene glycol). In addition, silk fibroin grafts were prepared avoiding dryness during the coating process and were kept in the hydrated state until implantation into the abdominal aorta was complete. After implantation of the hydrated silk fibroin grafts, grafts were taken out at two weeks or three months, and histopathological examination was performed. The grafts coated with three types of silk fibroin sponges had a higher tissue infiltration rate than alcohol-treated grafts and were superior in the formation of smooth muscle cell and vascular endothelial cell remodeling. Biodegradations of the silk fibroin grafts prepared using the three types of silk fibroin sponge coatings and alcohol-treated silk fibroin grafts were also examined with protease XIV in vitro, and the grafts were observed by scanning electron microscopy before and 24 h after biodegradation. Faster biodegradations were observed for grafts coated with the three types of silk fibroin sponges. 13C solid-state nuclear magnetic resonance studies showed that the conformation of the silk fibroin sponge prepared using porogen was a random coil with high mobility in the hydrated state. We believe that small-diameter silk fibroin vascular grafts coated with quick biodegradable silk fibroin sponges can be developed based on these findings.