Optimization of PTFE Coating on PDMS Surfaces for Inhibition of Hydrophobic Molecule Absorption for Increased Optical Detection Sensitivity.

Polydimethylsiloxane (PDMS) is a polymer widely used for fabrication and prototyping of microfluidic chips. The porous matrix structure of PDMS allows small hydrophobic molecules including some fluorescent dyes to be readily absorbed to PDMS and results in high fluorescent background signals, thereby significantly decreasing the optical detection sensitivity. This makes it challenging to accurately detect the fluorescent signals from samples using PDMS devices. Here, we have utilized polytetrafluoroethylene (PTFE) to inhibit absorption of hydrophobic small molecules on PDMS. Nile red was used to analyze the effectiveness of the inhibition and the absorbed fluorescence intensities for 3% and 6% PTFE coating (7.7 ± 1.0 and 6.6 ± 0.2) was twofold lower compared to 1% and 2% PTFE coating results (17.2 ± 0.5 and 15.4 ± 0.5). When compared to the control (55.3 ± 1.6), it was sevenfold lower in background fluorescent intensity. Furthermore, we validated the optimized PTFE coating condition using a PDMS bioreactor capable of locally stimulating cells during culture to quantitatively analyze the lipid production using Chlamydomonas reinhardtii CC-125. Three percent PTFE coating was selected as the optimal concentration as there was no significant difference between 3% and 6% PTFE coating. Intracellular lipid contents of the cells were successfully stained with Nile Red inside the bioreactor and 3% PTFE coating successfully minimized the background fluorescence noise, allowing strong optical lipid signal to be detected within the PDMS bioreactor comparable to that of off-chip, less than 1% difference.

Adverse childhood experiences and preschool suspension expulsion: A population study.

BACKGROUND: Preschool suspension and expulsion rates are typically based on teacher reports, and don't simultaneously account for adverse childhood experiences (ACEs). OBJECTIVE: To examine estimates in the United States of parent-reported preschool suspension and expulsion rates, in the context of ACEs. PARTICIPANTS AND SETTING: Parents of children aged 3-5 years old (N = 6,100) in the 2016 National Survey of Children's Health dataset. METHOD: We reported the prevalence estimates of preschool suspension and expulsion, and estimated the unique variance of ACEs as risk factors using weighted sequential logistic regression. RESULTS: An estimated 174,309 preschoolers (2.0%) were suspended, and 17,248 (0.2%) children were expelled annually. If divided by 36 school weeks, the instances of weekly suspension and expulsion were at least 4,842 and 479 respectively. Controlling for previous risk factors (i.e., age, gender, race, ethnicity), the odds ratio increased by 80% for every unit of ACEs increment. Children were more likely to be suspended or expelled if they had domestic violence (OR = 10.6, p <  .001), living with mental illness (OR = 9.8, p <  .001), adult substance abuse (OR = 4.8, p <  .001), and victim of violence (OR = 4.5, p =  .004), living in high poverty (OR = 3.9, p =  .001), divorced parents (OR = 3.3, p =  .001), and parent incarceration (OR = 3.0, p =  .009). CONCLUSION: The alarming suspension and expulsion rates call for more comprehensive outreach prevention and response efforts in preschool settings. Cross system collaboration and family support are essential to this work.