Performance characterization and biocompatibility assessment of silicone polyurethanes for polymer heart valve applications.

Silicone polyurethanes have gained widespread application in the biomedical field due to their excellent biocompatibility. This study comprehensively investigates four silicone polyurethane materials suitable for polymer heart valves, each exhibiting distinct chemical compositions and structural characteristics, leading to significant differences, particularly in mechanical performance and biocompatibility. Surface analysis reveals an elevated surface silicon element content in all materials compared to the bulk, indicating a migration of silicon elements towards the surface, providing a structural basis for enhancing biological stability and biocompatibility. However, higher silicon content leads to a decrease in mechanical performance, potentially resulting in mechanical failure and rupture in artificial heart valves. Concerning biocompatibility, an increase in silicone content diminishes the material's adsorption capability for cells and proteins, consequently improving its biocompatibility and biological stability. In summary, while high silicone content leads to a reduction in mechanical performance, the formation of a "silicon protective layer" on the material surface mitigates cell and protein adsorption, thereby enhancing biocompatibility and biological stability. Through comprehensive testing of the four silicone polyurethane materials, this study aims to provide insightful perspectives and methods for selecting materials suitable for polymer heart valves. Additionally, the thorough performance exploration of these materials serves as a crucial reference for the performance assessment and biocompatibility research of polymeric artificial heart valve materials.

Optimal treatment of tannic acid for the anti-calcification of bovine jugular veins and the underlying mechanism.

OBJECTIVES: To evaluate the effects of combined treatment with tannic acid and ferric ions on the biomechanical and anti-calcification properties of glutaraldehyde-fixed bovine jugular veins after xenografting. METHODS: Two-point bending test and uniaxial tensile test were used to evaluate the flexural and biomechanical properties; Subcutaneous implantation in rat and right ventricular outflow tract reconstruction of sheep were used to evaluate the anti-calcification effects; The performance of the graft in sheep models was evaluated every month after the surgery with echocardiography examination. Markers of macrophages, T lymphocytes, smooth muscle cell osteogenic differentiation and matrix metalloproteinases in sheep explants were detected by immunohistochemistry. RESULTS: The flexibility of the bovine jugular veins cotreated with ferric ions-tannic acid was improved while maintaining biomechanical properties and excellent anti-calcification effects. Echocardiography results showed that the grafts functioned well in the animals without stenosis or reflux of the valve. Immunohistochemical studies showed that the osteogenic differentiation marker (Runx2) was detected in calcified regions and colocalised with the SMC marker (α-SMA). Compared to the glutaraldehyde-treated samples, T-cell marker (CD3), matrix metalloproteinase-2 and 9 expressions were reduced in the ferric ions-tannic acid treated group. CONCLUSION: Ferric ions-tannic acid treatment can give the conduits better flexibility with excellent biomechanical properties and anti-calcification effects, making it a promising bovine jugular veins processing method.

[Value of endoscopic ultrasound-guided fine needle aspiration in pretest prediction and diagnosis of pancreatic ductal adenocarcinoma].

OBJECTIVE: To identify the predictive factors for differentiating pancreatic ductal adenocarcinoma (PDAC) from other neoplastic solid pancreatic lesions and assess the accuracy of endoscopic ultrasound-guided fine needle aspiration (EUS-FNA) for diagnosis of PDAC. METHODS: We retrospectively analyzed the clinical data of patients referred for EUS-FNA evaluation of pancreatic lesions in the Digestive Endoscopic Center of Nanfang Hospital between January, 2009 and May, 2016. The cases with unknown diagnosis, missing data, repeated punctures, cystic lesions and benign lesions were excluded from the analysis. The positivity rates of EUS-FNA were compared between patients with PDAC and those with non-PDAC lesions, and the sensitivity, specificity, positive predictive value, negative predictive value and accuracy of EUS-FNA were assessed in the diagnosis of PDAC. Univariate and multivariate logistic regression analyses were used to identify the factors for differentiating PDAC from non-PDAC lesions based on the demographic characteristics, clinical presentations, laboratory data, and endoscopic ultrasonography imaging features of the patients. RESULTS: Among the 75 patients with solid neoplastic pancreatic lesions, 54 (72.0%) were found to have PDAC and 21 (28.0%) had non-PDAC lesions. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of EUS-FNA for the diagnosis of PDAC were 77.8%, 100.0%, 100.0%, 63.6% and 84.0%, respectively. No significant difference was found in the positivity rate of EUS-FNA between patients with PDAC and those with non-PDAC lesions (77.8% vs 76.2%, P > 0.05). Multivariate regression analysis identified abdominal pain (OR=5.163, 95%CI: 1.093-24.389, P=0.038), lesion size (OR=0.926, 95%CI: 0.877-0.978, P=0.006), characteristics of the solid lesions (OR=7.105, 95%CI: 1.440-35.043, P=0.016), and evidence of metastases (OR=6.165, 95%CI: 1.332-28.533, P=0.020) as the independent factors for predicting PDAC. CONCLUSIONS: The pretest characteristics including abdominal pain, evidence of metastases, and lesion size and lesion characteristics defined by endoscopic ultrasonography findings can reliably predict a diagnosis of PDAC. EUS-FNA has a high sensitivity and a high specificity for the diagnosis of PDAC.

Genotoxicity of 1-methylpyrene and 1-hydroxymethylpyrene in Chinese hamster V79-derived cells expressing both human CYP2E1 and SULT1A1.

1-Methylpyrene (1-MP) is a widespread pollutant that is carcinogenic in animals following metabolic activation. Previous studies have shown that benzylic hydroxylation of 1-MP, catalyzed by multiple CYP isoforms, gives rise to 1-hydroxymethylpyrene (1-HMP), which becomes bioreactive following further metabolism by various sulfotransferase (SULT) isoforms. However, the mutagenic and chromosome damaging effects of 1-MP and 1-HMP in mammalian cells have not been investigated. In this study a Chinese hamster V79-derived cell line expressing both human CYP2E1 and human SULT1A1 was used to investigate the ability of 1-MP and 1-HMP to induce cytotoxicity (using the CCK-8 assay), micronuclei and Hprt gene mutations. The role of each enzyme was investigated through co-exposure in the presence of an enzyme inhibitor. We found that at concentrations of 0.5-4 µM and 5-20 µM, under conditions where no reduction in cell viability/growth occurred, 1-HMP and 1-MP induced micronuclei in V79-hCYP2E1-hSULT1A1 cells in a concentration-dependent manner; however, both compounds were inactive in V79 cells. Similarly, they both caused an increase in Hprt mutant frequency in V79-hCYP2E1-hSULT1A1 cells in these concentration ranges, with 1-MP impairing cell viability/growth at 10 µM and above in the mutagenicity assay. The compounds were again both inactive in V79 cells. The effects of 1-HMP in V79-hCYP2E1-hSULT1A1 cells were blocked or reduced by addition of pentachlorophenol (PCP), a SULT1 inhibitor; the genotoxicity of 1-MP was significantly reduced by either 1-aminobenotrazole, a CYP2E1 inhibitor, or PCP. The results suggest that human CYP2E1 and SULT1A1 cooperate to activate 1-MP and cause genotoxicity in mammalian cells.