Cellular Uptake and Intracellular Trafficking of Poly( N-(2-Hydroxypropyl) Methacrylamide)

Transcription factor NAC1 activates expression of peptidase-encoding AtCEPs in roots to limit root hair growth

Plant genomes encode a unique group of papain-type Cysteine EndoPeptidases (CysEPs) containing a KDEL endoplasmic reticulum (ER) retention signal (KDEL-CysEPs or CEPs). CEPs process the cell-wall scaffolding EXTENSIN (EXT) proteins that regulate de novo cell-wall formation and cell expansion. Since CEPs cleave EXTs and EXT-related proteins, acting as cell-wall-weakening agents, they may play a role in cell elongation. The Arabidopsis (Arabidopsis thaliana) genome encodes 3 CEPs (AtCPE1-AtCEP3). Here, we report that the genes encoding these 3 Arabidopsis CEPs are highly expressed in root-hair (RH) cell files. Single mutants have no evident abnormal RH phenotype, but atcep1-3 atcep3-2 and atcep1-3 atcep2-2 double mutants have longer RHs than wild-type (Wt) plants, suggesting that expression of AtCEPs in root trichoblasts restrains polar elongation of the RH. We provide evidence that the transcription factor NAC1 (petunia NAM and Arabidopsis ATAF1, ATAF2, and CUC2) activates AtCEPs expression in roots to limit RH growth. Chromatin immunoprecipitation indicates that NAC1 binds to the promoter of AtCEP1, AtCEP2, and, to a lower extent, AtCEP3 and may directly regulate their expression. Inducible NAC1 overexpression increases AtCEP1 and AtCEP2 transcript levels in roots and leads to reduced RH growth while the loss of function nac1-2 mutation reduces AtCEP1-AtCEP3 gene expression and enhances RH growth. Likewise, expression of a dominant chimeric NAC1-SRDX repressor construct leads to increased RH length. Finally, we show that RH cell walls in the atcep1-3 atcep3-2 double mutant have reduced levels of EXT deposition, suggesting that the defects in RH elongation are linked to alterations in EXT processing and accumulation. Our results support the involvement of AtCEPs in controlling RH polar growth through EXT processing and insolubilization at the cell wall.

The transmission and toxicity of polymer-bound doxorubicin-containing exosomes derived from human adenocarcinoma cells

Background: Exosomes are extracellular vesicles with the ability to encapsulate bioactive molecules, such as therapeutics. This study identified a new exosome mediated route of doxorubicin and poly(N-(2-hydroxypropyl)methacrylamide) (pHPMA)-bound doxorubicin trafficking in the tumor mass. Materials & methods: Exosome loading was achieved via incubation of the therapeutics with an adherent human breast adenocarcinoma cell line and its derived spheroids. Exosomes were characterized using HPLC, nanoparticle tracking analysis (NTA) and western blotting. Results: The therapeutics were successfully loaded into exosomes. Spheroids secreted significantly more exosomes than adherent cells and showed decreased viability after treatment with therapeutic-loaded exosomes, which confirmed successful transmission. Conclusion: To the best of our knowledge, this study provides the first evidence of pHPMA-drug conjugate secretion by extracellular vesicles.

Local detection of pH-induced disaggregation of biocompatible micelles by fluorescence switch ON

Fluorogenic nanoparticles (NPs) able to sense different physiological environments and respond with disaggregation and fluorescence switching OFF/ON are powerful tools in nanomedicine as they can combine diagnostics with therapeutic action. pH-responsive NPs are particularly interesting as they can differentiate cancer tissues from healthy ones, they can drive selective intracellular drug release and they can act as pH biosensors. Controlled polymerization techniques are the basis of such materials as they provide solid routes towards the synthesis of pH-responsive block copolymers that are able to assemble/disassemble following protonation/deprotonation. Ring opening metathesis polymerization (ROMP), in particular, has been recently exploited for the development of experimental nanomedicines owing to the efficient direct polymerization of both natural and synthetic functionalities. Here, we capitalize on these features and provide synthetic routes for the design of pH-responsive fluorogenic micelles via the assembly of ROMP block-copolymers. While detailed photophysical characterization validates the pH response, a proof of concept experiment in a model cancer cell line confirmed the activity of the biocompatible micelles in relevant biological environments, therefore pointing out the potential of this approach in the development of novel nano-theranostic agents.

Intelligent Escape System for the Oral Delivery of Liraglutide: A Perfect Match for Gastrointestinal Barriers

Epithelial cells are known to impede the oral delivery of polypeptides, and the accumulation of mucus and regular dynamic renewal also significantly impede drug absorption. In this work, we prepared a core-shell (COS) nanosystem using poly-N-(2-hydroxypropyl)methacrylamide (pHPMA)/chitosan (CTS). Liraglutide (NN2211) was isolated from the gastrointestinal environment and smoothly passes through the mucous layer. CSKSSDYQC (CSK) peptide and hemagglutinin-2 (HA₂) were introduced into the COS nanosystem to establish a complete path from the oral cavity to the epithelial basal side. The fate of nanocapsules in vivo was studied by fluorescence detection. The results showed that the nanocapsules escaped smoothly from the mucus. Taking into account the characteristics of CSK targeting goblet cells, we conducted cell-level studies, and the results showed that after the modification of CSK and pHPMA, more nanocapsules entered the cells. In vitro and in vivo evaluation results showed that the system successfully established a complete path from mucus to epithelial cells by responding to the gastrointestinal environment multiple times.