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Biodegradable shape memory polymers (SMPs) have great application prospects in biomedical fields, particularly, those SMPs with the transition temperature of ∼37 °C have attracted keen interests. In this study, poly­(d-lactide) (PDLA) of different molecular weights (5000 or 20 000) was introduced into poly­(l-lactide-co-glycolide) (PLGA) or poly­(l-lactide-co-ε-caprolactone) (PLCL) copolymers at different amounts (5, 10, 15 wt%) to investigate the effect of PLLA/PDLA stereocomplexation (SC-PLA) on the shape memory performance of the blends. The tested copolymers were in different chemical compositions to adjust the lengths of PLLA segments and the glass transition temperatures (T g). Characterizations on crystallization, mechanical properties, shape fixing, and recovery ratios of the blends were conducted, and the results were discussed to correlate the formation of SC-PLA crystals to the shape memory performances of corresponding blends. It was identified that SC-PLA crystals would act as cross-links and had strengthened the stationary phase within the matrixes, which could significantly improve the shape memory performances of PLGA/PDLA and PLCL/PDLA blends if more SC-PLA crystals had formed. Based on the findings, a kind of porous scaffold was prepared using the PLCL(75:25)/PDLA (5k, 10 wt%) blend, which displayed excellent and reproducible compression and recovery behaviors under 37 °C, showing potentials as body temperature triggered SMPs for in vivo applications such as implantable template to facilitate tissue regeneration.

BACKGROUND: Marathon running is an extreme sport with a distance of about 42 kilometers. Its relationship to high-sensitivity cardiac troponin (hs-cTn) remains controversial. OBJECTIVE: As the gold standard for detecting myocardial injury, the trends of hs-cTn before and after a marathon were investigated and analyzed. METHODS: A literature search was conducted in PubMed, EMBASE, and Cochrane Library databases by combing the keywords marathon and troponin, and studies regarding high-sensitivity cardiac troponin I (hs-cTnI) and high-sensitivity cardiac troponin T (hs-cTnT) concentrations before and after marathon running (not for half-marathon and ultra-marathon) were included. “Quality Assessment Tool for Before-After (Pre-Post) Studies With No Control Group” were used to assess the risk of bias. Statistical analysis was performed using Review Manager, presenting data as mean values and 95% confidence intervals (CIs). Sensitivity analysis and subgroup analysis were performed if there was high heterogeneity among studies based on I2 statistic. RESULTS: A total of 13 studies involving 824 marathoners were included in this systematic review and meta-analysis. Both hs-cTnI (MD 68.79 ng/L, [95% CI 53.22, 84.37], p< 0.001) and hs-cTnT (MD 42.91 ng/L, [95% CI 30.39, 55.43], p< 0.001) were elevated after running a marathon, but the concentration of hs-cTnT returned to baseline after 72 to 96 h post-race (MD 0.11 ng/L, [95% CI -1.30, 1.52], p= 0.88). The results of subgroup analysis demonstrated that the 99th percentile upper reference limit of hs-cTnT might be the source of heterogeneity. CONCLUSION: The concentrations of hs-cTnI and hs-cTnT were increased after marathon running, but the change of hs-cTnT is usually not seen as irreversible myocardial injury.