Activatable fluorescent probes for real-time imaging-guided tumor therapy.

Surgery and drug therapy are the two principal options for cancer treatment. However, their clinical benefits are hindered by the difficulty of accurate location of the tumors and timely monitoring of the treatment efficacy of drugs, respectively. Rapid development of imaging techniques provides promising tools to address these challenges. Compared with conventional imaging techniques such as magnetic resonance imaging and computed tomography etc., fluorescence imaging exhibits high spatial resolution, real-time imaging capability, and relatively low costs devices. The advancements in fluorescent probes further accelerate the implementation of fluorescence imaging in tumor diagnosis and treatment monitoring. In particular, the emergence of site-specifically activatable fluorescent probes fits the demands of tumor delineation and real-time feedback of the treatment efficacy. A variety of small molecule probes or nanoparticle-based probes have been developed and explored for the above-mentioned applications. This review will discuss recent advances in fluorescent probes with a special focus on activatable nanoprobes and highlight the potential implementation of activatable nanoprobes in fluorescence imaging-guided surgery as well as imaging-guided drug therapy.

Delivery of tacrolimus with cationic lipid-assisted nanoparticles for ulcerative colitis therapy.

Oral drug delivery with nanoparticles has demonstrated great potential for drugs with poor bioavailability. Efficient delivery is possible by overcoming both the mucus and epithelial barrier of the gastrointestinal tract (GIT). Cationic lipid-assisted nanoparticles (CLANs), which are composed of amphiphilic block copolymers and cationic lipids, have been well studied and have been proved beneficial for drug delivery. In this study, CLANs prepared by poly(ethylene glycol)-block-poly(lactic acid) (PEG-b-PLA) and 1,2-dioleoyl-3-trimethylammonium-propanechloride (DOTAP) or N,N-bis(2-hydroxyethyl)-N-methyl-N-(2-cholesteryloxycarbonyl aminoethyl)ammoniumbromide (BHEM-Chol) were used for oral delivery of tacrolimus (FK506) for ulcerative colitis treatment. The average size of these nanoparticles is around 110 nm and the zeta-potential is 35 mV. These nanoparticles maintained their size in buffer solutions of pH 1.2 and 6.8, and slowly release the encapsulated drug. CLANs can be accumulated in the colon and transported through the epithelium in the colitis model by dextran sulfate sodium salt (DSS), leading to attenuation of DSS-induced colitis.

Tumor extracellular acidity-activated nanoparticles as drug delivery systems for enhanced cancer therapy.

pH-responsive nanoparticles (NPs) are currently under intense development as drug delivery systems for cancer therapy. Among various pH-responsiveness, NPs that are designed to target slightly acidic extracellular pH environment (pHe) of solid tumors provide a new paradigm of tumor targeted drug delivery. Compared to conventional specific surface targeting approaches, the pHe-targeting strategy is considered to be more general due to the common occurrence of acidic microenvironment in solid tumors. This review mainly focuses on the design and applications of pHe-activated NPs, with special emphasis on pHe-activated surface charge reversal NPs, for drug and siRNA delivery to tumors. The novel development of NPs described here offers great potential for achieving better therapeutic effects in cancer treatment.

Surface charge switchable nanoparticles based on zwitterionic polymer for enhanced drug delivery to tumor.

Two faced nanoparticles: A zwitterionic polymer-based nanoparticle with response to tumor acidity is developed for enhanced drug delivery to tumors. The nanoparticles are neutrally charged at physiological conditions and show prolonged circulation time; after leaking into tumor sites, in the acidic extracellular tumor environment (pH(e) ), nanoparticles are activated and become positively charged and are therefore efficiently taken up by tumor cells, leading to enhanced therapeutic effects in cancer treatment.

Two consecutive click reactions as a general route to functional cyclic polyesters.

A simple and universal route to functional cyclic polyesters has been demonstrated, combining two consecutive click reactions of azide-alkyne cycloaddition of linear hetero-bifunctional precursors and thiol-ene coupling for post cyclization functionalizations. Functional cationic and thermo-responsive cyclic polyphosphoesters have been synthesized to demonstrate the efficiency of the procedures.

Micelle-to-vesicle morphological transition via light-induced rapid hydrophilic arm detachment from a star polymer.

Micelle-to-vesicle morphological transition has been achieved by light-induced rapid hydrophilic arm detachment from a star polymer. This provides a remote and clean method to control morphology transition of polymeric assemblies.

Temperature-induced morphological change of ABC 3-miktoarm star terpolymer assemblies in aqueous solution.

This work reports temperature-induced morphological change of ABC 3-miktoarm star terpolymer assemblies in aqueous solution. The terpolymer (MPEG)(PCL)(PPE) is composed of hydrophilic monomethoxy poly(ethylene glycol) (MPEG), hydrophobic poly(ɛ-caprolactone) (PCL) and thermosensitive polyphosphoester (PPE) chains, emanating from a central junction point. It is thermosensitive in aqueous solution, forming spherical micelles at lower temperature, which transition to short nano-rod morphology at temperature higher than the cloud point. The temperature induced morphological transition of this biodegradable miktoarm star terpolymer shows that it has potential in stimulus-controlled drug delivery applications.

Engineering nanoscopic hydrogels via photo-crosslinking salt-induced polymer assembly for targeted drug delivery.

We report the preparation of biodegradable nanoscopic hydrogels and their application for targeted drug delivery. The nanogel is synthesized in a template-free method by photo-crosslinking salt-induced polymer assemblies. With convenient incorporation of targeted lactosyl moieties, the nanogels efficiently deliver doxorubicin to HepG2 cells through receptor-mediated internalization.

Recent progress in polyphosphoesters: from controlled synthesis to biomedical applications.

Polyphosphoesters (PPEs) with repeating phosphoester bonds in the backbone are structurally versatile, biocompatible, and biodegradable through hydrolysis as well as enzymatic digestion under physiological conditions. They are appealing for biological applications because of their potential functionality, biocompatibility, and similarity to biomacromolecules such as nucleic acids. The expanding scope of PPEs in materials science, especially as biomaterials, is described in this review. We mainly focus on controlled synthetic methods of PPEs, which provide access to novel and complex polymer structures, especially for block copolymers. The hydrolytic and enzymatic degradation of PPEs, thermoresponsive PPEs, and biomedical applications have also been discussed.

Gold nanoparticles stabilized by thermosensitive diblock copolymers of poly(ethylene glycol) and polyphosphoester.

Aqueous dispersions of thermosensitive gold nanoparticles protected by diblock copolymers of poly(ethylene glycol) and polyphosphoester were prepared and studied. Diblock copolymers MPEG-b-P(EEP-co-PEP) with different compositions that are composed of monomethoxy poly(ethylene glycol), random copolymer of ethyl ethylene phosphate (EEP), and isopropyl ethylene phosphate (PEP) were synthesized by ring-opening polymerization in bulk. Thioctic acid was then conjugated to the terminal hydroxyl group of the polyphosphoester block by esterification. Gold nanoparticles were then prepared by a one-step method and showed core-shell structure with an average gold core diameter of about 10 nm surrounded by a MPEG-b-P(EEP-co-PEP) shell with a thickness of about 30 nm. These polymer stabilized gold nanoparticles are reversibly thermosensitive in aqueous medium, exhibiting tunable collapse temperatures which are dependent on the composition of the diblock copolymers. Methyl tetrazolium (MTT) assay against HEK 293 cells demonstrated that these gold nanoparticles are with good biocompatibility. These gold nanoparticles protected by thermosensitive diblock copolymers with tunable collapse temperature are expected to be useful for biomedical applications.