Quantitative Characterization of Inorganic Pores in Sinian Doushantou Dolomitic Shale Based on FIB-SEM in Western Hubei Province, China.

Unlike traditional shale gas reservoirs, where organic matter pores dominate, inorganic pores are the primary reservoir space in the Sinian (Ediacaran) high-maturity Doushantou dolomitic shale in western Hubei Province, China. The inorganic pore characteristics of Doushantuo shale and its influence on shale gas aggregation were investigated by examining the TOC content, thermal maturity, mineralogical composition, and field-emission scanning electron microscopy (SEM) and focused ion beam scanning electron microscopy (FIB-SEM) of drill cores. The results show that the shale mineral composition in the study area is primarily dolomite and plate-shaped interparticle-intercrystalline pores associated with dolomite are widespread inorganic pores in dolomitic shale. Interparticle-intercrystalline pores account for 75% of the total pores, with a pore size distribution mainly between 50 and 300 nm, as extracted from the 3D pore network model (PNM). Compared with organic pores, interparticle-intercrystalline pores provide greater space for gas storage and have a strong coupling relationship with the hydrocarbon generation and evolution of organic matter. Therefore, the inorganic pores in the Doushantuo Formation play a vital role in the enrichment and accumulation of shale gas. This study aims to establish a scientific basis for understanding the enrichment mechanism of shale gas in Doushantuo dolomitic shale and other inorganic pore-dominated shales in southern China.

Hybrid interpenetrating network of polyester coronary stent with tunable biodegradation and mechanical properties.

Poly(l-lactide) (PLLA) is an important candidate raw material of the next-generation biodegradable stent for percutaneous coronary intervention, yet how to make a polyester stent with sufficient mechanical strength and relatively fast biodegradation gets to be a dilemma. Herein, we put forward a hybrid interpenetrating network (H-IPN) strategy to resolve this dilemma. As such, we synthesize a multi-functional biodegradable macromer of star-like poly(d,l-lactide-co-ɛ-caprolactone) with six acrylate end groups, and photoinitiate it, after mixing with linear PLLA homopolymer, to trigger the free radical polymerization. The resultant crosslinked polymer blend is different from the classic semi-interpenetrating network, and partial chemical crosslinking occurs between the linear polymer and the macromer network. Combined with the tube blow molding and the postprocessing laser cutting, we fabricate a semi-crosslinked-polyester biodegradable coronary stent composed of H-IPN, which includes a physical network of polyester spherulites and a chemical crosslinking network of copolyester macromers and a part of homopolymers. Compared with the currently main-stream PLLA stent in research, this H-IPN stent realizes a higher and more appropriate biodegradation rate while maintaining sufficient radial strength. A series of polymer chemistry, polymer physics, polymer processing, and in vitro and in vivo biological assessments of medical devices have been made to examine the H-IPN material. The interventional implanting of the H-IPN stent into aorta abdominalis of rabbits and the follow-ups to 12 months have confirmed the safety and effectiveness.

Preliminary studies on intimal injury related to stent retrieval in a canine model.

OBJECTIVE: This pilot study aimed to observe intimal injuries related to stent retrieval in the iliac artery of a canine. BACKGROUND: In-stent restenosis remains challenging owing to permanent stent implantation. A retrievable stent may be alternative for intervention without permanent residue. METHODS: Five retrievable stents with point-to-point overlapped double-layer scaffolds were deployed into the iliac arteries and retrieved on days 14, 21, 28, 35, and 42 from five canines. RESULTS: Arterial diameter decreased by 9-10% before retrieval and 15% on day 14 after retrieval. In the 14-day-stent, the stent surface was clean without visible fibrin. In the 28-day-stent, the overlay was mainly composed of fibrin and fibroblasts. The proliferation of smooth muscle cells has not yet been observed with α-smooth muscle actin staining. In the 42-day-stent, endothelial and smooth muscle cells decreased under the struts, and the internal elastic lamina was interrupted segmentally. Neointima formation involves fibroblasts and smooth muscle cells. Neointimal thickness was negatively correlated with strut space. Stent traces on the artery wall tended to be flat at a follow-up14 days after retrieval. The primary intima was completely covered by neointima. Two stents could not be retrieved because of in-stent thrombosis or capture loss. CONCLUSIONS: The stent was covered mainly by depositional fibrin after 28 days and by typical neointima after 42 days. The stent retrieval procedure did not induce injury to vascular smooth muscle, and the intima repair was performed 14 days after stent retrieval.

A Biodegradable Metal-Polymer Composite Stent Safe and Effective on Physiological and Serum-Containing Biomimetic Conditions.

The new-generation coronary stents are expected to be biodegradable, and then the biocompatibility along with biodegradation becomes more challenging. It is a critical issue to choose appropriate biomimetic conditions to evaluate biocompatibility. Compared with other candidates for biodegradable stents, iron-based materials are of high mechanical strength, yet have raised more concerns about biodegradability and biocompatibility. Herein, a metal-polymer composite strategy is applied to accelerate the degradation of iron-based stents in vitro and in a porcine model. Furthermore, it is found that serum, the main environment of vascular stents, ensured the safety of iron corrosion through its antioxidants. This work highlights the importance of serum, particularly albumin, for an in vitro condition mimicking blood-related physiological condition, when reactive oxygen species, inflammatory response, and neointimal hyperplasia are concerned. The resultant metal-polymer composite stent is implanted into a patient in clinical research via interventional treatment, and the follow-up confirms its safety, efficacy, and appropriate biodegradability.

Research and clinical translation of trilayer stent-graft of expanded polytetrafluoroethylene for interventional treatment of aortic dissection.

The aortic dissection (AD) is a life-threatening disease. The transcatheter endovascular aortic repair (EVAR) affords a minimally invasive technique to save the lives of these critical patients, and an appropriate stent-graft gets to be the key medical device during an EVAR procedure. Herein, we report a trilayer stent-graft and corresponding delivery system used for the treatment of the AD disease. The stent-graft is made of nitinol stents with an asymmetric Z-wave design and two expanded polytetrafluoroethylene (ePTFE) membranes. Each of the inner and outer surfaces of the stent-graft was covered by an ePTFE membrane, and the two membranes were then sintered together. The biological studies of the sintered ePTFE membranes indicated that the stent-graft had excellent cytocompatibility and hemocompatibility in vitro. Both the stent-graft and the delivery system exhibited satisfactory mechanical properties and operability. The safety and efficacy of this stent-graft and the corresponding delivery system were demonstrated in vivo. In nine canine experiments, the blood vessels of the animals implanted with the stent-grafts were of good patency, and there were no thrombus and obvious stenosis by angiography after implantation for 6 months. Furthermore, all of the nine clinical cases experienced successful implantation using the stent-graft and its postrelease delivery system, and the 1-year follow-ups indicated the preliminary safety and efficacy of the trilayer stent-graft with an asymmetric Z-wave design for interventional treatment.

Diabetes results in structural alteration of chondroitin sulfate in the urine.

PURPOSE: The assessment of the clinical significance of chondroitin sulfate in patients with type 2 diabetes mellitus (T2DM) and diabetic nephropathy (DN) for the detection of the relationship between chondroitin sulfate (CS) structure and disease. METHODS: Healthy control (n=15), type 2 diabetic patients with normalbuminuria (n=12), and patients with microalbuminuria (n=13) were enrolled in the study. Total sulfated glycosaminoglycans (GAGs) concentration in the first morning urine was evaluated by 1,9-dimethylmethylene blue method and the composition was determined by agarose gel electrophoresis. Urinary chondroitin sulfate was quantified by a combination of treatment with specific lyase digestions and separation of products by SAX-HPLC. RESULTS: GAGs concentration significantly increased in diabetic patients with microalbuminuria compared to diabetic patients with normalbuminuria. Qualitative analysis of urinary GAGs revealed the presence of chondroitin sulfate, heparan sulfate, and low-sulphated chondroitin sulphate-protein complex (LSC-PG). There was a decrease in CS and an increase in LSC-PG in the urine of patients with diabetes compared to healthy controls. Moreover, in diabetic patients, chondroitin sulfate contains more 6-sulfated disaccharide and less 4-sulfated disaccharide. There was a statistically significant difference in ratio of 6-sulfated disaccharide to 4-sulfated disaccharide among the three groups. CONCLUSIONS: GAGs were significantly increased in diabetic patients with microalbuminuria. The levels of urinary GAGs, ratio of LSC-PG/CS, as well as ratio of 6-sulfated to 4-sulfated disaccharides could be useful markers for diagnosis of patients with diabetic nephropathy.

[Experimental study of saikosaponin-D (SSd) on lipid peroxidation of hepatic fibrosis on rat].

OBJECTIVE: To study the effect of SSd on lipid peroxidation during experimental hepatic fibrosis progression. METHOD: The experimental models of hepatic fibrosis were induced by intraperitoneal injection of dimethylnitrosamine (DMN) on rats. SSd was administered by intraperitoneal injection for 4 weeks. Serum was analyzed for alanine and aspartate aminotransferase (ALT and AST), hyaluronic acid (HA), laminin (LN), collagen IV (IV-C), malonaldehyde (MDA) and superoxide dismutase (SOD) activities. Liver samples were measured for MDA contents and SOD activities in normal group, model group and SSd group. RESULT: SSd significantly decreased ALT and AST activities and lowered HA, LN and IV-C contents. It enhanced SOD activities in liver, while reduced MDA contents both in serum and liver. CONCLUSION: SSd has obvious effects of protecting hepatocytes and resisting hepatic fibrosis, and the mechanism may be associated with its anti-lipid peroxidation effect.