Comparative efficacy and safety of late surfactant preparations: a retrospective study.

OBJECTIVE: Characterize the use, efficacy, and safety of poractant alfa and calfactant surfactants compared to beractant in preterm infants receiving late surfactant. STUDY DESIGN: We included infants <37 weeks gestational age (GA) discharged from Pediatrix Medical Group-managed neonatal intensive care units (1997-2017). Efficacy and safety outcomes of interest were analyzed. RESULTS: Of 184,770 infants administered surfactant at any time, 7846 (4.23%) received late surfactant at a median (25th, 75th percentile) PNA of 8 days (3, 22); specifically, 2976 received poractant alfa (38%), 2890 beractant (37%), and 1936 calfactant (25%). We identified no significant differences in composite efficacy or safety outcomes between surfactants in the primary analysis, but 33-36 week GA infants administered poractant alfa had significantly greater odds of developing a safety event. CONCLUSIONS: Compared to beractant, there is no evidence of overall superior efficacy or safety of poractant alfa.

Silicones for Stretchable and Durable Soft Devices: Beyond Sylgard-184.

This paper identifies and characterizes silicone elastomers that are well-suited for fabricating highly stretchable and tear-resistant devices that require interfacial bonding by plasma or UV ozone treatment. The ability to bond two or more pieces of molded silicone is important for creating microfluidic channels, chambers for pneumatically driven soft robotics, and other soft and stretchable devices. Sylgard-184 is a popular silicone, particularly for microfluidic applications. However, its low elongation at break (∼100% strain) and moderate tear strength (∼3 N/mm) make it unsuitable for emerging, mechanically demanding applications of silicone. In contrast, commercial silicones, such as Dragon Skin, have excellent mechanical properties yet are difficult to plasma-bond, likely because of the presence of silicone oils that soften the network yet migrate to the surface and interfere with plasma bonding. We found that extracting silicone oligomers from these soft networks allows these materials to bond but only when the Shore hardness exceeds a value of 15 A. It is also possible to mix highly stretchable silicones (Dragon Skin and Ecoflex) with Sylgard-184 to create silicones with intermediate mechanical properties; interestingly, these blends also only bond when the hardness exceeds 15 A. Eight different Pt-cured silicones were also screened; again, only those with Shore hardness above 15 A plasma-bond. The most promising silicones from this study are Sylgard-186 and Elastosil-M4130 and M4630, which exhibit a large deformation (>200% elongation at break), high tear strength (>12 N/mm), and strong plasma bonding. To illustrate the utility of these silicones, we created stretchable electrodes by injecting a liquid metal into microchannels created using such silicones, which may find use in soft robotics, electronic skin, and stretchable energy storage devices.