Diselenide-containing nonionic gemini polymeric micelles as a smart redox-responsive carrier for potential programmable drug release

Doxorubicin-loaded Polymeric Biotin-PEG-SeSe-PBLA Micelles with surface Binding of Biotin-Mediated Cancer Cell Targeting and Redox-Responsive Drug release for enhanced anticancer efficacy

Biotin receptors are overexpressed in various cancer cell types, essential in tumor development, metabolism, and metastasis. Chemotherapeutic agents may be more effective and have fewer adverse effects if they specifically target the biotin receptors on cancer cells. Polymeric micelles (PMs) with nanoscale size via the EPR effect to accumulate near tumor tissue. We utilized the solvent exchange technique to crate polymeric Biotin-PEG-SeSe-PBLA micelles. This underwent self-assembly to create uniformly dispersed PMs with a hydrodynamic diameter of 81.54 ± 0.23 nm. The resulting PMs characterized by 1HNMR, 13CNMR, FTIR, and Raman spectroscopy. PMs exhibited a high efficacy of Doxorubicin encapsulation (EE) and loading content (DLC), with values of 5.93 wt% and 74.32 %, respectively. DOX@Biotin-PEG-SeSe-PBLA micelles showed optimal DOX release, around 89 % and 74 % in 10 mM glutathione and 0.1 % H2O2, respectively, within 72 hours, in the simulated cancer redox pool. Fascinatingly, the blank Biotin-PEG-SeSe-PBLA micelles did not affect the HaCaT or HeLa cell lines; approximately 85 % of the cells were metabolically active. Contrarily, at a 5 μg/ml concentration, DOX@Biotin-PEG-SeSe-PBLA specifically inhibited the proliferation of roughly 76 % of HeLa cells and 11 % of HaCaT cells. The fluorescence microscopy results demonstrated that biotin-decorated micelles were more successfully internalized by HeLa cells, which overexpress the biotin receptor, than by non-targeted micelles in vitro. In summary, the diselenide-linked Biotin-PEGSeSe-PBLA formed smart PMs that could offer DOX specific to cancer cells with precision and are physiologically durable.

Redox-Responsive Comparison of Diselenide and Disulfide Core-Cross-Linked Micelles for Drug Delivery Application

In this study, diselenide (Se–Se) and disulfide (S–S) redox-responsive core-cross-linked (CCL) micelles were synthesized using poly(ethylene oxide)2k-b-poly(furfuryl methacrylate)1.5k (PEO2k-b-PFMA1.5k), and their redox sensitivity was compared. A single electron transfer-living radical polymerization technique was used to prepare PEO2k-b-PFMA1.5k from FMA monomers and PEO2k-Br initiators. An anti-cancer drug, doxorubicin (DOX), was incorporated into PFMA hydrophobic parts of the polymeric micelles, which were then cross-linked with maleimide cross-linkers, 1,6-bis(maleimide) hexane, dithiobis(maleimido) ethane and diselenobis(maleimido) ethane via Diels–Alder reaction. Under physiological conditions, the structural stability of both S–S and Se–Se CCL micelles was maintained; however, treatments with 10 mM GSH induced redox-responsive de-cross-linking of S–S and Se–Se bonds. In contrast, the S–S bond was intact in the presence of 100 mM H2O2, while the Se–Se bond underwent de-crosslinking upon the treatment. DLS studies revealed that the size and PDI of (PEO2k-b-PFMA1.5k-Se)2 micelles varied more significantly in response to changes in the redox environment than (PEO2k-b-PFMA1.5k-S)2 micelles. In vitro release studies showed that the developed micelles had a lower drug release rate at pH 7.4, whereas a higher release was observed at pH 5.0 (tumor environment). The micelles were non-toxic against HEK-293 normal cells, which revealed that they could be safe for use. Nevertheless, DOX-loaded S–S/Se–Se CCL micelles exhibited potent cytotoxicity against BT-20 cancer cells. Based on these results, the (PEO2k-b-PFMA1.5k-Se)2 micelles can be more sensitive drug carriers than (PEO2k-b-PFMA1.5k-S)2 micelles.

Flame-Retardant and Self-Healing Waterborne Polyurethane Based on Organic Selenium

Waterborne polyurethane has drawn extensive attention due to its environmental friendliness and is widely used in many areas. However, it is still a great challenge to synthesize waterborne polyurethanes with flame retardancy and fast room-temperature self-healing ability, along with excellent mechanical performance and emulsion stability due to the mutually contradictory nature of these properties. Herein, waterborne polyurethanes containing organic selenium (SWPU-x) from 0.67 to 3.28 wt % were synthesized, which could simultaneously realize flame retardancy and self-healing ability based on the ability to scavenge active free radicals at high temperature and the dynamic switch of diselenide. All these SWPU-x films self-extinguished within 1 s after the ignition in the vertical combustion tests. The limiting oxygen index of SWPU-4 was improved to 28.5% with excellent UL-94 level (V-0) and self-healing efficiency (91.25%, after being healed in the photoreactor for 30 min at room temperature), together with high mechanical properties (tensile strength was 18.5 MPa and elongation at break was 869.63%), and the total heat release (THR) for SWPU-4 (49.28 MJ/m²) could decrease to 23.80% of the THR for the original waterborne polyurethane WPU (64.67 MJ/m²). This work discovered a new flame-retardant element (organic selenium) and studied its flame-retardant behaviors and self-healing function simultaneously, which would extremely extend the application of waterborne polyurethanes.

Smart Polymeric Micelles for Anticancer Hydrophobic Drugs

Cancer has become one of the deadliest diseases in our society. Surgery accompanied by subsequent chemotherapy is the treatment most used to prolong or save the patient's life. Still, it carries secondary risks such as infections and thrombosis and causes cytotoxic effects in healthy tissues. Using nanocarriers such as smart polymer micelles is a promising alternative to avoid or minimize these problems. These nanostructured systems will be able to encapsulate hydrophilic and hydrophobic drugs through modified copolymers with various functional groups such as carboxyls, amines, hydroxyls, etc. The release of the drug occurs due to the structural degradation of these copolymers when they are subjected to endogenous (pH, redox reactions, and enzymatic activity) and exogenous (temperature, ultrasound, light, magnetic and electric field) stimuli. We did a systematic review of the efficacy of smart polymeric micelles as nanocarriers for anticancer drugs (doxorubicin, paclitaxel, docetaxel, lapatinib, cisplatin, adriamycin, and curcumin). For this reason, we evaluate the influence of the synthesis methods and the physicochemical properties of these systems that subsequently allow an effective encapsulation and release of the drug. On the other hand, we demonstrate how computational chemistry will enable us to guide and optimize the design of these micelles to carry out better experimental work.

Redox-responsive carrier based on fluorinated gemini amphiphilic polymer for combinational cancer therapy

Polymeric micelle has emerged as an efficient implement to overcome the shortcomings of conventional cancer chemotherapy due to its superior solubility of hydrophobic drugs and less side effects of drugs. However, insufficient dilution resistance and ordinary therapeutic effect severely restrict the further translation of current drug-loaded polymeric micelles. Here, we showed that well-defined G-Fn (n = 5, 9, 13) polymeric micelles possessed excellent capabilities as a drug carrier in light of high drug loading content, high stability and precise drug release combined with wonderful endocytosis efficiency to tumors. The representative G-F13 exhibited an excellent dilution resistance, outstanding high drug loading content (22 wt%) and drug loading efficiency (82%), which might be attributed to the extremely low critical micelle concentration conferred by its special Gemini structure and the superhydrophobicity of the fluorocarbon chain. Furthermore, the "cross-linked" internal fluoride membrane consisted of the two chains of the Gemini structure made G-F13 stable even after 24 h of incubation in 10% fetal bovine serum (FBS). The camptothecin (CPT) release was selectively triggered by glutathione (GSH) and H₂O₂, reaching 75% and 85% after 24 h respectively, in which only 15% of drugs leak under physiological conditions. The CCK-8 assays of Hela cells showed that CPT-loaded G-F13 micelles had high cell compatibility (200 μg/mL, 93% cell viability, 48 h) and high cancer cytotoxicity (IC50 0.1 μg/mL). Notably, a tenfold lower dosage of loaded CPT had an higher tumor growth inhibition than the free CPT. This result was attributed to the combined treatment of fluorinated drug carriers were more likely to penetrate the cell membrane to enter tumor cells, the cytotoxicity of selenic acid generated after the oxidation of G-F13 and the large amounts of CPT after redox release. Excellent physical and chemical properties as well as good therapeutic effects reveal that G-F13 can act as a promising drug carrier to widely use in cancer chemotherapy.

An Integrated Tumor Microenvironment Responsive Polymeric Micelle for Smart Drug Delivery and Effective Drug Release

Tumor microenvironment (TME) responsive polymeric micelles are promising carriers for drug delivery. In order to meet the needs of various applications, multifarious TME-responsive switches are used to construct smart polymeric micelles, which causes the complexity and corpulence of the polymeric micelle system and increases the difficulty of preparation. In this study, we designed and synthesized an ingenious TME-responsive switch through grafting disulfide bond-modified piperidinepropionic acid (CPA) on copolymer poly(ethylene glycol)-b-poly(aspartate)(PEG-b-PAsp) and built a novel pH/reduction-responsive PEG-b-PAsp-g-CPA polymeric micelle delivery system. The CPA-pendants can reverse the surface charge of the polymeric micelle from negative to positive at pH 6.5 because of the protonation of piperidine groups, thereby enhancing the internalization of cell. Subsequently, more piperidine groups are protonated at pH 5.0 which will increase the hydrophilicity of polymeric micelles and cause the hydrophobic core to swell, thus making the disulfide bonds packed in the core to be more easily broken by GSH. With the synergistic effect of the pH-triggered protonation of piperidine groups and reduction triggered break of disulfide bonds, the polymeric micelles will disintegrate and achieve efficient intracellular drug release. The TME-responsive polymeric micelles exhibited good biological safety, enhanced internalization, and rapid intracellular doxorubicin (DOX) release in vitro. Moreover, the PEG-b-PAsp-g-CPA/DOX polymeric micelles showed excellent antitumor efficacy and low systemic toxicity in lung tumor-bearing BALB/C mice. These results indicated that the novel integrated TME-responsive switch CPA helps the PEG-b-PAsp-g-CPA polymeric micelles to obtain excellent TME-responsiveness and antitumor drug delivery capabilities, while it also makes the preparation of TME-responsive polymeric micelles simpler and more convenient. This work provides a new idea for the architecture of TME-responsive polymeric micelles.

Recent developments in selenium-containing polymeric micelles: prospective stimuli, drug-release behaviors, and intrinsic anticancer activity

Selenium is capable of forming a dynamic covalent bond with itself and other elements and can undergo metathesis and regeneration reactions under optimum conditions. Its dynamic nature endows selenium-containing polymers with striking sensitivity towards some environmental alterations. In the past decade, several selenium-containing polymers were synthesized and used for the preparation of oxidation-, reduction-, and radiation-responsive nanocarriers. Recently, thioredoxin reductase, sonication, and osmotic pressure triggered the cleavage of Se-Se bonds and swelling or disassembly of nanostructures. Moreover, some selenium-containing nanocarriers form oxidation products such as seleninic acids and acrylates with inherent anticancer activities. Thus, selenium-containing polymers hold promise for the fabrication of ultrasensitive and multifunctional nanocarriers of radiotherapeutic, chemotherapeutic, and immunotherapeutic significance. Herein, we discuss the most recent developments in selenium-containing polymeric micelles in light of their architecture, multiple stimuli-responsive properties, emerging immunomodulatory activities, and future perspectives in the delivery and controlled release of anticancer agents.