Table 6.
Examples of Selenium-Based Oxidation-Responsive Systems
| Polymer structure | Formulation | Oxidant | Response to oxidation | Evidence of degradation | Ref. |
|---|---|---|---|---|---|
| SeQTAPEG43-b-PAA153 | Polymeric superamphi-phile micelles | 0.1% H2O2 (∼30 mM) | Disassembly of micelles after oxidation of selenide groups into hydrophilic selenoxide | TEM, micelles disappeared in 1 h | (81) |
| Release of FluNa over ∼11 h, control not shown | |||||
| PEG-b-PUSe-b-PEG | 71 nm block copolymer aggregates | 0.1% H2O2 (∼30 mM) | Dissociation due to oxidation of selenides into hydrophilic selenoxide or selenone groups | TEM, aggregates disappear in 5 h | (121) |
| XPS, selenoxide, and selenone formation | |||||
| Greater dox release (10 h) than from polysulfide analogs (72% vs. 42%) | |||||
| PEG-b-PUSeSe-b-PEG | 67 nm micellar aggregates | γ radiation (5 and 50 Gy) | Oxidation of diselenide groups into seleninic acid by the oxidative species (HO•, •HO2, and H2O2) generated by water during γ-radiation | FTIR, appearance of seleninide acid | (123) |
| TEM, swollen micelles (5 Gy) Collapsed irregular aggregates (50 Gy) |
|||||
| Diselenide bonds cleavage induces partial disassembly and drug release | Dox release in 8 h, 72% (50 Gy) 43% (5 Gy) 0% (0 Gy) |
||||
| PEG-b-PUSeSe-b-PEG | 76 nm micellar aggregates | 0.1% H2O2 (∼30 mM) | Se-Se bonds are cleaved and oxidized to seleninic acid | NMR, appearance of seleninide acid | (122) |
| TEM, micelle disassembly in 5 h in 0.1% H2O2 | |||||
| 0.01% H2O2 (∼3 mM) | Diselenide bonds cleavage induces complete disassembly and drug release | RB release within 5 h in 0.01 and 0.1% H2O2; no release in absence of H2O2 | |||
| PEO-b-PAA-Se-64a | 33 nm micellar aggregates | 0.1% H2O2 (∼30 mM) | Structural dissociation due to the oxidation of side-chain selenide groups into hydrophilic selenoxide groups | TEM, disassembly of the micelles in 8 h | (150) |
| NMR and FTIR of a model compound; selenoxide appearance | |||||
| NR quenching within 25 h; control not shown |
a
Grafting ratio.
SeQTA, selenium-containing surfactant; XPS, X-ray photoelectron spectroscopy; FluNa, fluorescein sodium; Dox, doxorubicin, FTIR, Fourier transform infrared spectroscopy; RB, Rhodamine B.