We monitored the viability and morphology of mouse fibroblast cells cultured on PDMS substrates with different degrees of polymer stiffness. The stiffness was controlled by varying the ratio between base and crosslinker agent during mixing. Although the standard PDMS mixing ratio is 10 : 1 (base to crosslinker; Young's modulus, E= =580 kPa), we found that a PDMS substrate with a high stiffness (mixing ratio of 5 : 1, E= =1,000 kPa) was more favorable as a substrate for fibroblast cell growth. It is important to note that an extracellular matrix coating was not applied to the PDMS so that the effect of stiffness on cell growth could be studied in isolation. A stiffness reduction of 40% (from a mixing ratio of 5 : 1 to 10 : 1) produced a significant reduction in survival rate (viability was reduced by 15%), and viability worsened (was reduced by 45%) for a substrate stiffness of 280 kPa (a mixing ratio of 20 : 1). The rate of spreading for the cells was measured to show that stiffer materials promoted more prolific fibroblast growth. These results provide PDMS stiffness guidelines for cell culture substrates.
BackgroundRisk factors associated with opioid-induced adverse reactions (OIARs) in the elderly population have not been well defined. The objective of this study was to determine effects of various risk factors on incidence of OIARs in male elderly patients.MethodsA retrospective cohort study in Korea Veterans Hospital was performed. Data were analyzed in male patients aged 65 years and older who received morphine, oxycodone, or codeine. Binomial variables describing patient-related and drug-related characteristics were constructed. Associations between these variables and frequency of OIARs were determined. Odds ratio (OR) and adjusted odds ratio (AOR) were calculated from univariate and multivariable analyses, respectively. Attributable risk was obtained by (1–1/OR)*100%.ResultsOf 316 patients, 28% experienced at least one adverse event. The most common adverse events were gastrointestinal problems (n = 59) and central nerve system adverse effects (n = 20). The odds of OIARs in patients with opioid use ≥12 weeks was increased by 80% compared to those with opioid use < 12 weeks. Attributable risk of GABA analogues was 64~78% in constructed Models. Compared to codeine users, patients using morphine and oxycodone had 653 and 473% increased odds for OIARs, respectively. MME ≥ 60 mg/day had a 317% increased odds for OIARs (95% CI: 1.92–9.04) compared to MME < 60 mg/day. Opioid combination therapy had a 139% increased odds for OIARs compared to monotherapy.ConclusionsThese findings have significant implications for clinical use of opioid in elderly patients. Our study suggests that low dose short-term use will pose less risk of OIARs for the elderly, whereas concomitant use of GABA analogues, strong opioids and dual-opioid therapy may increase the risk of OIARs. Therefore, clinician should carefully monitor patients when starting opioid therapy in older population.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.