Table 7.
Examples of Thioether-Based Oxidation-Responsive Systems
| Polymer structure | Formulation | Oxidant | Response to oxidation | Evidence of degradation | Ref. |
|---|---|---|---|---|---|
| EG16-PS50-EG16 | Triblock macro-amphiphiles unilamellar vesicles; membrane ∼8 nm thick | 0.03%–10% H2O2 (∼9 mM-3 M) | HLB alteration and vesicle disruption due to the oxidation of the hydrophobic PPS blocks into hydrophilic polypropylene sulfoxides and sulfones | OD, clear: 10% H2O2 (10 h), 0.03% (300 h) | (139) |
| TEM, vesicle number, shape change: 10% H2O2 (few min), 0.03% H2O2 (150 min) | |||||
| NMR, appearance of sulfoxides and sulfones | |||||
| Poly(PS74-b-DMA310) | 100 nm micelles | 1.1 mM-1.1 M H2O2, 1–100 μM ONOO−, or 1–100 mM SIN-1 | PPS oxidation causes micelles disassembly into unimeric polymers and cargo release | NMR, sulfone formation in H2O2 | (76) |
| DLS+TEM, disruption, 1.1 M H2O2 | |||||
| NR or DiO release correlating to H2O2, ONOO−, or SIN-1 conc. | |||||
| Disulfide cross-linked PPS | 25–225 nm Pluronic F127-stabilized PPS NP | 5%–10% H2O2 (∼1.5–3 M) | Swelling and solubilization after conversion to hydrophilic polypropylene sulfoxides and sulfones | OD, loss of turbidity: 5% H2O2 (30 h), 10% H2O2 (95 h) | (149) |
| PPS | 150 nm Pluronic F127-stabilized PPS NP | 25–200 ppm | PPS oxidation causes swelling and cargo release | OD, transmittance incr. | (3) |
| NaOCl | Reichardt's dye release, 98%, 5 min (2000 ppm NaOCl) | ||||
| CPO and hMPO+200 mM NaCl, 500 μM H2O2 | NR: transmittance incr. 17%, fluor. decr. 70% (CPO); transm. incr. 10%, fluor. decr. 80% (hMPO) | ||||
| PPADT | 600 nm NP | KO2 (unknown level) | Cleavage of thioketal linkages on oxidation | GPC, PPADT degradation in 8 h (high or low pH, no change) | (196) |
| Poly(thio-ether ketal) | 200 nm NP | 100 mM H2O2 | Dual response: thioether oxidation into sulfoxides produces more swollen and hydrophilic particles, enabling ketal hydrolysis and payload release |
DLS, NP degradation, pH 5/100 mM H2O2, 15 h | (125) |
| pH: 5, 6.5, and 7.4 | NMR, complete hydrolysis in 2 d | ||||
| NR quenching: >80% in 25 h, 100 mM H2O2 (pH 5 or pH 7); <30% in abs. | |||||
| OVA release: ∼100% in 100 mM H2O2 (pH 6.5); <20% without H2O2 |
DLS, dynamic light scattering; EG, ethylene glycol; GPC, gel permeation chromatography; HLB, hydrophilic to lipophilic balance; hMPO, human myeloperoxidase; Mn, number average molecular weight; OD, optical density; PPS, poly(propylene sulfide); PS, propylene sulfide; PGSE, pulse gradient spin echo; PPADT, poly-(1,4-phenyleneacetone dimethylene thioketal); poly(PS74-b-DMA310), a diblock polymer of propylene sulfide (PS) and N,N-dimethylacrylamide; DiO, (3,3′-dioctadecyloxacarbocyanine perchlorate); CPO, chloroperoxidase; OVA, ovalbumin Alexa Fluor 594; NMR, nuclear magnetic resonance.