Complexation of graphene oxide (GO) and cetyltrimethylammonium bromide (CTAB), a model amphiphile, was quantitatively studied to elucidate the governing forces and resulting structures of their self-assembly. We systematically varied pertinent self-assembly parameters, including GO size, mixing ratio, salt, and osmotic stress, and quantified the nanoscale structures of GO:CTAB using x-ray diffraction (XRD). Multilamellar stacking of GO and CTAB layers persists in all GO:CTAB assemblies exhibiting structural order. While driven by hydrophobic interactions between the hydrocarbon tails, the CTAB layer displays a series of structural transitions from a bilayer with in-plane ordering to a more fluidic bilayer and to an interdigitated monolayer. Interaction between GO and CTAB layers shows to be dominated by electrostatics, and osmotic stress studies indicate the absence of continuous hydration layers in GO:CTAB assemblies. Adding salt increases the inter-layer spacing by intercalating between GO and CTAB layers, and this ion layer can be expelled by high osmotic stress. These studies provide quantitative knowledge of the structure and interaction of GO:CTAB complexation, which lays foundation for precise control and rational design of their nanoscale self-assemblies.

Purpose: Studies on Lattice radiotherapy (LRT) for breast cancer have been largely lacking. This study investigates the dosimetric feasibility of using Gamma Pod, a stereotactic radiotherapy apparatus originally designed for breast SBRT, to deliver LRT to large, bulky breast tumor as a noninvasive treatment option. Methods: The GammaPod-based LRT was simulated using Geant4 Gate Monte Carlo software. The simulated GammaPod was equipped with 5 mm diameter non-coplanar circular beams that span 28°l atitudinally from 18°to 43°off the horizontal plane. Two degrees longitudinal intervals were used to simulate rotating sources. To simulate the treatments to different breast sizes, three water-equivalent hemisphere volumes with diameters of 10, 15, and 20 cm were analyzed. The lattice was planned by spacing focal points 2 cm apart in the transverse and sagittal planes and 2.5 cm in the coronal plane. This resulted in 22-172 shots for full breast treatment. The maximum dose for each individual shot was 20 Gy. The peak-to-valley dose differences and skin dose were analyzed. To verify the feasibility of delivering LRT, a test plan was created and delivered to a commercial diode array dose verification device using a clinical GammaPod system with 15 mm collimators. Results: The dose profiles showed the average peak-to-valley dose percent differences of 94.10% in the 10 cm hemispherical volume, 88.95% in the 15 cm hemispherical volume, and 83.60% in the 20 cm hemispherical volume. Average skin dose was 1.27, 1.72, and 2.13 Gy for the 10, 15, and 20 cm irradiation volumes, respectively. The LRT plan delivered using a clinical GammaPod system with larger collimators verified the feasibility of LRT plan delivery. Conclusion: GammaPod-based lattice radiotherapy is a viable treatment option and its application can be extended to treating large bulky breast tumors.