Grafting of Poly(methyl methacrylate) Brushes from Magnetite Nanoparticles Using a Phosphonic Acid Based Initiator by Ambient Temperature Atom Transfer Radical Polymerization (ATATRP)

Poly(methyl methacrylate) in the brush form is grown from the surface of magnetite nanoparticles by ambient temperature atom transfer radical polymerization (ATATRP) using a phosphonic acid based initiator. The surface initiator was prepared by the reaction of ethylene glycol with 2-bromoisobutyrl bromide, followed by the reaction with phosphorus oxychloride and hydrolysis. This initiator is anchored to magnetite nanoparticles via physisorption. The ATATRP of methyl methacrylate was carried out in the presence of CuBr/PMDETA complex, without a sacrificial initiator, and the grafting density is found to be as high as 0.90 molecules/nm2. The organic–inorganic hybrid material thus prepared shows exceptional stability in organic solvents unlike unfunctionalized magnetite nanoparticles which tend to flocculate. The polymer brushes of various number average molecular weights were prepared and the molecular weight was determined using size exclusion chromatography, after degrafting the polymer from the magnetite core. Thermogravimetric analysis, X-ray photoelectron spectra and diffused reflection FT-IR were used to confirm the grafting reaction

Change in Hippocampus Volume as a Function of Radiation Dose: Early Results From a Prospective Trial with Standardized Imaging and Morphometric Evaluation

Pediatric brain tumor patients are at high risk of developing neurocognitive deficits following treatment. The perihippocampal subventricular zone contains a niche of radiosensitive neural progenitor cells linked to memory development, and radiotherapy (RT) to this brain substructure has been associated with neurocognitive impairment in randomized trials. In this prospective study, 3D volumetric MRIs were obtained in pediatric brain tumor patients at baseline and during follow-up to measure volumetric changes in multiple brain substructures along with neurocognitive, endocrine, quality-of-life, and exploratory biomarker assessments. In this planned interim analysis, we model early outcomes for change in hippocampal volume at 6 months following RT. As of 2/26/2021, 47 patients had enrolled on this prospective study and 36 had completed their 6-month follow-up assessments after fractionated intensity-modulated proton therapy (IMPT) for primary brain and skull base tumors. Left and right hippocampus volumes were independently measured on T1 sagittal precontrast MRI using automated software at baseline and 6-months after RT and were compared to manual physician contours. The relationship between mean hippocampus dose and change in volume was assessed by Pearson's correlation coefficient. The effect of mean hippocampus dose on change in volume was assessed for mean doses < 10 Gy and ≥10 Gy by t-test. A linear mixed-effects (LME) model was applied to evaluate other predictors associated with change in hippocampus volume, assuming random effects of subjects. Potential factors considered were age, gender, tumor location, focal vs. whole brain RT, prior craniotomy, and chemotherapy. Mean hippocampus dose was strongly correlated with change in hippocampus volume at 6 months following RT (r = −0.727, 95% CI [-0.820 -0.596], P < 0.001). Hippocampus volumes and observed changes over time were similar between the software and physician-delineated contours. A significant reduction in hippocampus volume was observed for mean doses ≥10 Gy (mean Δ -10.8% ± 5.5%, P < 0.001), while no significant change in volume was observed for mean doses < 10 Gy (mean Δ +0.7% ± 3.9%). The LME model demonstrated that only mean hippocampus dose was significantly associated with change in hippocampus volume (P < 0.001). The final model predicted a -3.4% change in hippocampus volume for every 10 Gy increase in mean dose. Regression diagnostics showed no evidence of lack-of-fit and no patterns in residuals. Change in hippocampus volume was correlated with hippocampus mean dose at 6 months following RT. A significant reduction in hippocampus volume was observed for mean doses ≥10 Gy compared to no significant change at mean doses < 10 Gy. Future analyses from this study will assess volume change in this and other brain substructures over time as a function of radiation dose and will correlate these findings with measured neurocognitive and other late effects

A scalable manufacturing process for flexible active-matrix e-paper displays

A scalable manufacturing process for fabricating active-matrix backplanes on low-cost flexible substrates, a key enabler for electronic-paper displays, is presented. This process is based on solution processing, ink-jet printing, and laser patterning. A multilayer architecture is employed to enable high aperture ratio and array performance. These backplanes were combined with E Ink electrophoretic media to create high-performance displays that have high contrast, are bistable, and can be flexed repeatedly to a radius of curvature of 5 mm