Degradable Polymer-Based Nanoassemblies for Precise Targeting and Drug Delivery to Breast Cancer Cells without Affecting Normal Healthy Cells

Stimuli-responsive amphiphilic polymers are known to be precursors to forming promising nanoarchitectonics with tunable properties for application in biomedical sciences. Currently, self-immolative polymers are widely recognized as an emerging class of responsive materials with excellent degradability, which is one of the crucial criteria for designing a robust drug delivery vehicle. Here, we design an amphiphilic polyurethane endowed with a redox-responsive self-immolative linker and a pH-responsive tertiary amine on the backbone, which forms entropy-driven nanoscale supramolecular assemblies (average hydrodynamic diameter ∼110 nm) and is programmed to disassemble in a redox environment (GSH) due to the degradation of the polymer in a self-immolative fashion. The nanoassembly shows efficient drug sequestration and release in a controlled manner in response to glutathione (10 mM). The tertiary amine residing on the surface of the nanoassembly becomes protonated in the tumor microenvironment (pH ∼ 6.4-6.8) and generates positively charged nanoassembly (ζ-potential = +36 mV), which enhances the cancer cell-selective cellular uptake. The biological evaluation of the drug-loaded nanoassembly revealed triple-negative breast cancer (MDAMB-231) selective internalization and cell death while shielding normal cells (RBCs or PBMCs) from off-targeting toxicity. We envision that polyurethane with a redox-responsive self-immolative linker might open up new opportunities for a completely degradable polyurethane-based nanocarrier for drug delivery and diagnosis applications.

Kinetically stable sub-50 nm fluorescent block copolymer nanoparticles via photomediated RAFT dispersion polymerization for cellular imaging

Self-assembled block copolymer nanoparticles (NPs) have emerged as major potential nanoscale vehicles for fluorescence bioimaging. The preparation of NPs with high yields possessing high kinetic stability to prevent the leakage of fluorophore molecules is crucial to their practical implementation. Here, we report a photomediated RAFT polymerization-induced self-assembly (PISA) yielding uniform and nanosized poly((oligo(ethylene glycol) acrylate)-block-poly(benzyl acrylate) particles (POEGA-b-PBzA) with a concentration of 22 wt%, over 20 times more than with micellization and nanoprecipitation. The spherical diblock copolymer nanoparticles have an average size of 10-50 nm controllable through the degree of polymerization of the stabilizing POEGA block. Subsequent dialysis against water and swelling with Nile red solution led to highly stable fluorescent NPs able to withstand the changes in concentration, ionic strength, pH or temperature. A PBzA/water interfacial tension of 48.6 mN m^-1 hinders the exchange between copolymer chains, resulting in the trapping of NPs in a "kinetically frozen" state responsible for high stability. A spectroscopic study combining fluorescence and UV-vis absorption agrees with a preferential distribution of fluorophores in the outer POEGEA shell despite its hydrophobic nature. Nile red-doped POEGA-b-PBzA micelles without initiator residues and unimers but with high structural stability turn out to be noncytotoxic, and can be used for the optical imaging of cells. Real-time confocal fluorescence microscopy shows a fast cellular uptake using C2C12 cell lines in minutes, and a preferential localization in the perinuclear region, in particular in the vesicles.

pH/Reduction Dual-Stimuli-Responsive Cross-Linked Micelles Based on Multi-Functional Amphiphilic Star Copolymer: Synthesis and Controlled Anti-Cancer Drug Release

Novel approach has been constructed for preparing the amphiphilic star copolymer pH/reduction stimuli-responsive cross-linked micelles (SCMs) as a smart drug delivery system for the well-controlled anti-tumor drug doxorubicin (DOX) release. The SCMs had a low CMC value of 5.3 mg/L. The blank and DOX-loaded SCMs both had a spherical shape with sizes around 100-180 nm. In addition, the good stability and well pH/reduction-sensitivity of the SCMs were determined by dynamic light scattering (DLS) as well. The SCMs owned a low release of DOX in bloodstream and normal tissues while it had a fast release in tumor higher glutathione (GSH) concentration and/or lower pH value conditions, which demonstrates their pH/reduction dual-responsiveness. Furthermore, we conducted the thermodynamic analysis to study the interactions between the DOX and polymer micelles in the DOX release process. The values of the thermodynamic parameters at pH 7.4 and at pH 5.0 conditions indicated that the DOX release was endothermic and controlled mainly by the forces of an electrostatic interaction. At pH 5.0 with 10 mM GSH condition, electrostatic interaction, chemical bond, and hydrophobic interactions contributed together on DOX release. With the low cytotoxicity of blank SCMs and well cytotoxicity of DOX-loaded SCMs, the results indicated that the SCMs could form a smart cancer microenvironment-responsive drug delivery system. The release kinetic and thermodynamic analysis offer a theoretical foundation for the interaction between drug molecules and polymer matrices, which helps provide a roadmap for the oriented design and control of anti-cancer drug release for cancer therapy.

Light-activated "cycle-reversible intramolecular charge transfer" fluorescent probe: monitoring of pHi trace change induced by UV light in programmed cell death

Under the synergistic effects of protonation and deprotonation, a light-activated fluorescent probe (UV-SP) exhibited "cycle-reversible intramolecular charge transfer (ICT)" for different pH after activation by UV light, resulting in emission of multiple ratio fluorescent signals (FI563/FI595 and FI664/FI595). Based on these kinds of response signals, UV-SP can specifically monitor the cycle-reversible trace change of intracellular pH caused by UV radiation. More importantly, according to the stable and invariant multiple ratio fluorescent signals, UV-SP can sort cells entering programmed death.