The last decade has witnessed enormous research focused on cationic polymers. Cationic polymers are the subject of intense research as non-viral gene delivery systems, due to their flexible properties, facile synthesis, robustness and proven gene delivery efficiency. Here, we review the most recent scientific advances in cationic polymers and their derivatives not only for gene delivery purposes but also for various alternative therapeutic applications. An overview of the synthesis and preparation of cationic polymers is provided along with their inherent bioactive and intrinsic therapeutic potential. In addition, cationic polymer based biomedical materials are covered. Major progress in the fields of drug and gene delivery as well as tissue engineering applications is summarized in the present review.

In modern society, traffic and transportation and the manufacturing industry and construction industries continuously release large amounts of dust and particles into the atmosphere, which can cause heavy air pollution, leading to health hazards. The haze disaster, a serious problem in developing countries such as China and India, has become one of the main issues of global environmental pollution in recent decades. Many air filtration technologies have been developed. Air filtration using electrospun fibers that intercept fine particles/volatile organic gases/bacterium is a relatively new, but highly promising, technique. Due to their interconnected nanoscale pore structures, highly specific surface areas, fine diameters, and porous structure as well as their ability to incorporate active chemistry on a nanoscale surface, electrospun fibers are becoming a promising versatile platform for air filtration. In this review, following a short introduction concerning the need for air filtration and filtration theory and mechanism, electrospun nanofibers membranes for air filtration have been highlighted, including the preparation (electrospinning process) and the parameters relevant to filtration efficacy. Additionally, various types (function) of the electrospun air filtration membranes have been classified in detail. Furthermore, their potential in the filtration of fine particles and chemical pollutants has been discussed. Finally, the challenges of their practical application and the future prospects have been summarized. Given that some advanced electrospun air filtration nanofibrous membranes exist for treating different contaminants from various types of polluted atmosphere, it is believed that they should make a significant contribution in protection against air pollution.

In gene therapy, endosomal escape represents a major bottleneck since nanoparticles often remain entrapped inside endosomes and are trafficked toward the lysosomes for degradation. A detailed understanding of the endosomal barrier would be beneficial for developing rational strategies to improve transfection and endosomal escape. By visualizing individual endosomal escape events in live cells, we obtain insight into mechanistic factors that influence proton sponge-based endosomal escape. In a comparative study, we found that HeLa cells treated with JetPEI/pDNA polyplexes have a 3.5-fold increased endosomal escape frequency compared to ARPE-19 cells. We found that endosomal size has a major impact on the escape capacity. The smaller HeLa endosomes are more easily ruptured by the proton sponge effect than the larger ARPE-19 endosomes, a finding supported by a mathematical model based on the underlying physical principles. Still, it remains intriguing that even in the small HeLa endosomes, <10% of the polyplex-containing endosomes show endosomal escape. Further experiments revealed that the membrane of polyplex-containing endosomes becomes leaky to small compounds, preventing effective buildup of osmotic pressure, which in turn prevents endosomal rupture. Analysis of H1299 and A549 cells revealed that endosomal size determines endosomal escape efficiency when cells have comparable membrane leakiness. However, at high levels of membrane leakiness, buildup of osmotic pressure is no longer possible, regardless of endosomal size. Based on our findings that both endosomal size and membrane leakiness have a high impact on proton sponge-based endosomal rupture, we provide important clues toward further improvement of this escape strategy.

Laser-assisted photoporation is a promising technique that is receiving increasing attention for the delivery of membrane impermeable nanoscopic substances into living cells. Photoporation is based on the generation of localized transient pores in the cell membrane using continuous or pulsed laser light. Increased membrane permeability can be achieved directly by focused laser light or in combination with sensitizing nanoparticles for higher throughput. Here, we provide a detailed account on the history and current state-ofthe-art of photoporation as a physical nanomaterial delivery technique. We first introduce with a detailed explanation of the mechanisms responsible for cell membrane pore formation, following an overview of experimental procedures for realizing direct laser photoporation. Next, we review the second and most recent method of photoporation that combines laser light with sensitizing NPs. The different mechanisms of pore formation are discussed and an overview is given of the various types of sensitizing nanomaterials. Typical experimental setups to achieve nanoparticlemediated photoporation are discussed as well. Finally, we discuss the biological and therapeutic applications enabled by photoporation and give our current view on this expanding research field and the challenges and opportunities that remain for the near future.

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