Targeted delivery of miR-34a-5p by phenylborate-coupled polyethylenimide nanocarriers for anti-KSHV treatment

Endo-lysosomal escape strategies of cationic polymer-mediated gene delivery at a glance. The targeted and efficiency-oriented delivery of (therapeutic) nucleic acids raises hope for successful gene therapy, i.e. , for the local and individual treatment of acquired and inherited genetic disorders. Despite promising achievements in the field of polymer-mediated gene delivery, the efficiency of the non-viral vectors remains orders of magnitude lower than viral-mediated ones. Several obstacles on the molecular and cellular level along the gene delivery process were identified, starting from the design and formulation of the nano-sized carriers up to the targeted release to their site of action. In particular, the efficient escape from endo-lysosomal compartments was demonstrated to be a major barrier and its exact mechanism still remains unclear. Different hypotheses and theories of the endosomal escape were postulated. The most popular one is the so-called “proton sponge” hypothesis, claiming an escape by rupture of the endosome through osmotic swelling. It was the first effort to explain the excellent transfection efficiency of poly(ethylene imine). Moreover, it was thought that a unique mechanism based on the ability to capture protons and to buffer the endosomal pH is the basis of endosomal escape. Recent theories deal with the direct interaction of the cationic polyplex or free polymer with the exoplasmic lipid leaflet causing membrane destabilization, permeability or polymer-supported nanoscale hole formation. Both escape strategies are more related to viral-mediated escape compared to the “proton sponge” effect. This review addresses the different endosomal release theories and highlights their key mechanism.

The past few decades have witnessed an evolution of nanomedicine from biologically inert entities to more smart systems, aimed at advancing in vivo functionality. However, we should recognize that most systems still rely on reasonable explanation-including some over-explanation-rather than definitive evidence, which is a watershed radically determining the speed and extent of advancing nanomedicine. Probing nano-bio interactions and desirable functionality at the tissue, cellular, and molecular levels is most frequently overlooked. Progress toward answering these questions will provide instructive insight guiding more effective chemo-physical strategies. Thus, in the next generation, we argue that much effort should be made to provide definitive evidence for proof-of-mechanism, in lieu of creating many new and complicated systems for similar proof-of-concept.

Multifunctional nanomaterials with efficient tumor-targeting and high antitumor activity are highly anticipated in the field of cancer therapy. In this work, a synergetic tumor-targeted, chemo-photothermal combined therapeutic nanoplatform based on a dynamically PEGylated, borate-coordination-polymer-coated polydopamine nanoparticle (PDA@CP-PEG) is developed. PEGylation on the multifunctional nanoparticles is dynamically achieved via the reversible covalent interaction between the surface phenylboronic acid (PBA) group and a catechol-containing poly(ethylene glycol) (PEG) molecule. Due to the acid-labile PBA/catechol complex and the weak-acid-stable PBA/sialic acid (SA) complex, the nanoparticles can exhibit a synergetic targeting property for the SA-overexpressed tumor cells, i.e., the PEG-caused "passive targeting" and PBA-triggered "active targeting" under the weakly acidic tumor microenvironment. In addition, the photothermal effect of the polydopamine core and the doxorubicin-loading capacity of the porous coordination polymer layer endow the nanoparticles with the potential for chemo-photothermal combination therapy. As expected, the in vitro and in vivo studies both verify that the multifunctional nanoparticles possess relatively lower systematic toxicity, efficient tumor targeting ability, and excellent chemo-photothermal activity for tumor inhibition. It is believed that these multifunctional nanoparticles with synergetic tumor targeting property and combined therapeutic strategies would provide an insight into the design of a high-efficiency antitumor nanoplatform for potential clinical applications.