We investigated the effect of chain length on the cytotoxicity and endocytosis of rhodamine B end-labeled cationic linear poly(2-(
N,N
-dimethylamino)ethyl methacrylate) (RhB-PDMAEMA) polymers [M
w = (1.1−4.8) × 104 g/mol and M
w/M
n ∼ 1.2], which were synthesized via atom transfer radical polymerization by using rhodamine B-based initiator. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), lactate dehydrogenase (LDH), and caspase-3/7 assays revealed that the cytotoxicity and cellular membrane disruption of HepG2 cells induced by PDMAEMA depend on both the polymer concentration and chain length, and the apoptosis depends on chain length at the concentration of 37.6 μg/mL. In the concentration range 10−110 μg/mL, PDMAEMA chains with different lengths are cytotoxic to HepG2 cells by different mechanisms. Namely, (1) for short PDMAEMA chains [M
w = (1.1−1.7) × 104 g/mol], the cytotoxicity, membrane disruption, and apoptosis are very low, independent of the chain length; (2) in the medium range (1.7 × 104 < M
w < 3.9 × 104 g/mol), the cytotoxicity increases with the chain length and polymer concentration, mainly due to the cooperative effect of membrane disruption and apoptosis; and (3) for long chains [M
w = (3.9−4.8) × 104 g/mol], they are very disruptive to the cellular membrane, pro-apoptotic, and able to enter the cytoplasm and nucleus faster than short chains, as revealed by the real-time confocal laser scanning microscopy images, and their much higher cytotoxicity is independent of the PDMAEMA chain length.
Multiple emulsions are complex polydispersed systems in which both oil-in-water (O/W) and water-in-oil (W/O) emulsion exists simultaneously. They are often prepared accroding to a two-step process and commonly stabilized using a combination of hydrophilic and hydrophobic surfactants. Recently, some reports have shown that multiple emulsions can also be produced through one-step method with simultaneous occurrence of catastrophic and transitional phase inversions. However, these reported multiple emulsions need surfactant blends and are usually described as transitory or temporary systems. Herein, we report a one-step phase inversion process to produce water-in-oil-in-water (W/O/W) multiple emulsions stabilized solely by a synthetic diblock copolymer. Unlike the use of small molecule surfactant combinations, block copolymer stabilized multiple emulsions are remarkably stable and show the ability to separately encapsulate both polar and nonpolar cargos. The importance of the conformation of the copolymer surfactant at the interfaces with regards to the stability of the multiple emulsions using the one-step method is discussed.
We report stretchable metal-mesh transparent electrodes (TEs) with excellent electrical conductivity (<2 Ω/sq) and optical transparency (>80%) under up to 55% strain. The figures of merit on these electrodes, as defined as the ratio between electrical conductivity and optical conductivity, are among the highest reported for stretchable TEs under moderate stretching. Moreover, we demonstrate their application in a stretchable electroluminescent (EL) light-emitting film as top and bottom electrodes. EL lighting devices require low-resistance electrodes to unleash their potential for large-area low-power-consumption applications, in which our highly conductive and transparent stretchable TEs provide an edge on other competitor approaches. Importantly, our stretchable metal-mesh electrodes are fabricated through a vacuum-free solution-processed approach that is scalable for cost-effective mass production. We also investigate the fracture and fatigue mechanisms of stretchable metal-mesh electrodes with various mesh patterns and observe different behaviors under one-time and cyclic stretching conditions. Our solution-processed fabrication method, failure mechanism investigation, and device demonstration for metal-mesh stretchable TEs will facilitate the adoption of this promising high-performance approach in stretchable and wearable electronics applications.
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