Sterilization effects on poly(glycerol dodecanedioate): A biodegradable shape memory elastomer for biomedical applications.

Biodegradable shape memory polymers provide unique regenerative medicine approaches in minimally invasive surgeries. Once heated, thermally responsive shape memory polymer devices can be compressed, programmed to fit within a small profile, delivered in the cold programmed state, and expanded when heated to body temperature. We have previously developed a biodegradable shape memory elastomer (SME), poly(glycerol dodecanedioate) (PGD), with transition temperatures near 37°C exhibiting nonlinear elastic properties like numerous soft tissues. Using SMEs in the clinic requires disinfection and sterilization methods that conserve physiochemical, thermomechanical, and shape recovery properties. We evaluated disinfection protocols using 70% ethanol and UV254 nm for research applications and ethylene oxide (EtO) gas sterilization for clinical applications. Samples disinfected with ethanol for 0.5 and 1 min showed no changes in physiochemical material properties, but after 15 min showed slower recovery rates than controls (p < .05). EtO sterilization at 54.4°C decreased transition temperatures and shape recovery rate compared to EtO sterilization at 37.8°C (p < .01) and controls (p < .05). Aging samples for 9 months in a vacuum desiccator significantly reduced shape recovery, and the recovery rate in EtO sterilized samples compared to controls (p < .001). Cytotoxicity testing (ISO-10993.5C:2012) revealed media extractions from EtO sterilized samples, sterilized at 37.8°C, and high-density polyethylene negative control samples exhibit lower cytotoxicity (IC50) than Ethanol 1 min, UV 2 h, and EtO 54.4°C. Cell viability of NIH3T3 fibroblasts on sterilized surfaces was equivalent on EtO 37.7°C, EtO 54.4°C and Ethanol sterilized substrates. Finally, chromogenic bacterial endotoxin testing showed endotoxin levels were below the FDA prescribed levels for devices contacting blood and lymphatic tissues for ethanol 1 min, UV 120 min, EtO 37.7°C, EtO 54.4°C. These findings outline various disinfection and sterilization processes for research and pre-clinical application and provide a pathway for developing custom sterilization cycles for the translation of biomedical devices utilizing PGD shape memory polymers.

DNA methylation and expression of KCNQ3 in bipolar disorder.

OBJECTIVES: Accumulating evidence implicates the potassium voltage-gated channel, KQT-like subfamily, member 2 and 3 (KCNQ2 and KCNQ3) genes in the etiology of bipolar disorder (BPD). Reduced KCNQ2 or KCNQ3 gene expression might lead to a loss of inhibitory M-current and an increase in neuronal hyperexcitability in disease. The goal of the present study was to evaluate epigenetic and gene expression associations of the KCNQ2 and KCNQ3 genes with BPD. METHODS: DNA methylation and gene expression levels of alternative transcripts of KCNQ2 and KCNQ3 capable of binding the ankyrin G (ANK3) gene were evaluated using bisulfite pyrosequencing and the quantitative real-time polymerase chain reaction in the postmortem prefrontal cortex of subjects with BPD and matched controls from the McLean Hospital. Replication analyses of DNA methylation findings were performed using prefrontal cortical DNA obtained from the Stanley Medical Research Institute. RESULTS: Significantly lower expression was observed in KCNQ3, but not KCNQ2. DNA methylation analysis of CpGs within an alternative exonic region of KCNQ3 exon 11 demonstrated significantly lower methylation in BPD, and correlated significantly with KCNQ3 mRNA levels. Lower KCNQ3 exon 11 DNA methylation was observed in the Stanley Medical Research Institute replication cohort, although only after correcting for mood stabilizer status. Mood stabilizer treatment in rats resulted in a slight DNA methylation increase at the syntenic KCNQ3 exon 11 region, which subsequent analyses suggested could be the result of alterations in neuronal proportion. CONCLUSION: The results of the present study suggest that epigenetic alterations in the KCNQ3 gene may be important in the etiopathogenesis of BPD and highlight the importance of controlling for medication and cellular composition-induced heterogeneity in psychiatric studies of the brain.

Direct observation of dynamic mechanical regulation of DNA condensation by environmental stimuli.

Gene delivery is a promising way to treat hereditary diseases and cancer; however, there is little understanding of DNA:carrier complex mechanical properties, which may be critical for the protection and release of nucleic acids. We applied optical tweezers to directly measure single-molecule mechanical properties of DNA condensed using 19-mer poly-L-lysine (PLL) or branched histidine-lysine (HK) peptides. Force-extension profiles indicate that both carriers condense DNA actively, showing force plateaus during stretching and relaxation cycles. As the environment such as carrier concentration, pH, and the presence of zinc ions changes, DNA:HK complexes showed dynamically regulated mechanical properties at multiple force levels. The fundamental knowledge from this study can be applied to design a mechanically tailored complex which may enhance transfection efficiency by controlling the stability of the complex temporally and spatially.