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Controlling poly(ethylene glycol) (PEG) shielding/deshielding at the desired site of action exhibits great advantages for nanocarrier-based on-demand drug delivery in vivo. However, the current PEG deshielding strategies were mainly designed for anticancer drug delivery; even so, their applications are also limited by tumor heterogeneity. As a proof-of-concept, we explored a photoinduced PEG deshielding nanocarrier TK-NP Ce6&PTX to circumvent the aforementioned challenge. The TK-NP Ce6&PTX encapsulating chlorin e6 (Ce6) and paclitaxel (PTX) was self-assembled from an innovative thioketal (TK) linkage-bridged diblock copolymer of PEG with poly(d,l-lactic acid) (PEG-TK-PLA). We demonstrated that the high PEGylation of TK-NP Ce6&PTX in blood helps the nanocarrier efficiently avoid rapid clearance and consequently prolongs its circulation time. At the desired site (tumor), 660-nm red light irradiation led to ROS generation in situ, which readily cleaved the TK linkage, resulting in PEG deshielding. Such photoinduced PEG deshielding at the desired site significantly enhances the cellular uptake of the nanocarriers, achieving on-demand drug delivery and superior therapeutic efficacy. More importantly, this strategy of photoinducing PEG deshielding of nanocarriers could potentially extend to a variety of therapeutic agents beyond anticancer drugs for on-demand delivery., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Theranostic polymeric nanomaterials are of special important in cancer treatment. Here, novel galactose targeted pH-responsive amphiphilic multiblock copolymer conjugated with both drug and near-infrared fluorescence (NIR) probe has been designed and prepared by a four-steps process: (1) ring-opening polymerization (ROP) of N-carboxy anhydride (NCA) monomers using propargylamine as initiator; (2) reversible addition-fragmentation chain transfer (RAFT) polymerization of oligo(ethylene glycol) methacrylate (OEGMA) and gal monomer by an azido modified RAFT agent; (3) combing the obtained two polymeric segments by click reaction; (4) NIR copolymer prodrug was synthesized by chemical linkage of both cyanine dye and anticancer drug doxorubicin to the block copolymer via amide bond and hydrazone, respectively. The obtained NIRF copolymers were characterized by nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), and its was measured by means of micelles dynamic light scattering (DLS), field emission transmission electron microscopy (FETEM), and UV-vis and fluorescence spectrophotometry. The prodrug has strong fluorescence in the near-infrared region, and a pH sensitive drug release was confirmed at pH of 5.4 via an in vitro drug release experiment. Confocal laser scanning microscopy (CLSM) and flow cytometry experiments of the prodrug on both HepG2 and NIH3T3 cells reveal that the galactose targeted polymeric prodrug shows a fast and enhanced endocytosis due to the specific interaction for HepG2 cells, indicating the as-prepared polymer is a candidate for theranosis of liver cancer.

Biodegradable hollow capsules encapsulating protein drugs were prepared via layer-by-layer assembly of water-soluble chitosan and dextran sulfate on protein-entrapping amino-functionalized silica particles and the subsequent removal of the silica. In order to enhance the encapsulated efficiency and decrease its burst release, we designed this new system to fulfill these two goals. Bovine serum albumin (BSA), which was used as model protein, was entrapped in the nanocapsules. This system demonstrated a good capacity for the encapsulation and loading of BSA. The burst release was decreased to less than 10% in phosphate-buffered saline within 2h. No significant conformation change was noted from the released BSA in comparison with native BSA by using circular dichroism spectroscopy. Cell viability study suggested that the nanocapsules had good biocompatibility. The drug release kinetics mechanism is Fickian diffusion. These kinds of novel composite nanocapsules may offer a promising delivery system for water-soluble proteins and peptides.

Abstract Minimizing drug leakage at off-target sites and triggering sufficient drug release in tumor tissue are major objectives for effective nanoparticle (NP)-based cancer therapy. The current covalent and cleavable drug-NP conjugation strategy is promising but lacks high controllability to realize tumor-specific release. As a proof-of-concept, the reactive oxygen species (ROS)-activatable thioketal (TK) bond was explored as the linkage between doxorubicin (DOX) and polyphosphoester (PPE- TK -DOX). The Ce6@PPE- TK -DOX NPs constructed by co-self-coassembly of PPE- TK -DOX and the photosensitizer Ce6 efficiently prevented premature drug leakage in the off-target tissue and cells because of the high stability of the TK bond under physiological conditions. Once circulating into the tumor site, the 660-nm red light was precisely employed to irradiate the tumor area under the guidance of fluorescence/magnetic resonance (MR) dual-model imaging, which can induce localized ROS generation, resulting in rapid cleavage of the TK bond. Consequently, the DOX prodrug was locoregionally released and activated, achieving tumor-specific drug delivery with high controllability by light. Such phototriggered prodrug release and activation at the desired site significantly enhanced the therapeutic efficacy and minimized the side effect, providing new avenues to develop drug delivery systems for remote on-demand drug delivery in vivo. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]