The dialysis method was employed to prepare blank and doxorubicin (DOX) loaded micelles formed by temperature- and pH- sensitive polyhistidine-co-polyDL-lactide-co-glycolide-co-polyethyleneglycol-co-polyDL-lactide-co-glycolide-co-polyhistidine (PHis-b-PLGA-b-PEG-b-PLGA-b-PHis). The critical micelle concentrations (CMC) of the copolymers were measured with Pyrene Fluorescent Probe Technique. The temperature- and pH- sensitive properties of the blank micelles solution were investigated by optical transmittance measurement. The morphology and diameter of DOX micelles were characterized by transmission electron microscopy (TEM) and dynamic light scattering (DLS). The entrapment rate and drug-loading rate were determined with dialysis method. The in vitro release study was further performed to examine the temperature- and pH-responsive drug release behavior from DOX-loaded micelles. The results indicated that the CMC, entrapment efficiency and drug-loaded amount of the micelles were 7.5 x 10(-3) g x L(-1), 85.2 +/- 3.1% and 10.4 +/- 4.5%, respectively. The DOX micelle was globular-shaped with a mean diameter of 91.1 +/- 15.8 nm. The transmittance of micelle solution consistently increased with the increasing temperature or decreasing pH. In comparison to the drug release profile at physiological conditions (37 degrees C, pH 7.4), the DOX-loaded micelles showed faster drug release rate at higher temperature (41 degrees C), lower pH (pH 7.0, pH 6.5, pH 5.0) or higher temperature and lower pH (41 degrees C, pH 5.0). This indicated that the micelles showed a temperature and pH-triggered drug release pattern. Base on the above results, it can be concluded that PHis-b-PLGA-b-PEG-b-PLGA-b-PHis block copolymer micelles which respond to temperature and pH stimuli are promising smart carriers for anti-tumor drugs with the advantages of temperature- and pH- triggered drug release.

Amplifying "eat me signal" during tumor immunogenic cell death (ICD) cascade is crucial for tumor immunotherapy. Inspired by the indispensable role of adenosine triphosphate (ATP, a necessary "eat me signal" for ICD), a versatile ICD amplifier was developed for chemotherapy-sensitized immunotherapy. Doxorubicin (DOX), ATP and ferrous ions (Fe²⁺) were co-assembled into nanosized amplifier (ADO-Fe) through π‒π stacking and coordination effect. Meanwhile, phenylboric acid-polyethylene glycol-phenylboric acid (PBA-PEG-PBA) was modified on the surface of ADO-Fe (denoted as PADO-Fe) by the virtue of d-ribose unit of ATP. PADO-Fe could display active targetability against tumor cells via sialic acid/PBA interaction. In acidic microenvironment, PBA-PEG-PBA would dissociate from amplifier. Moreover, high H₂O₂ concentration would induce hydroxyl radical (·OH) and oxygen (O₂) generation through Fenton reaction by Fe²⁺. DOX and ATP would be released from the amplifier, which could induce ICD effect and "ICD adjuvant" to amplify this process. Together with programmed death ligands 1 (PD-L1) checkpoint blockade immunotherapy, PADO-Fe could not only activate immune response against primary tumor, but also strong abscopal effect against distant tumor. Our simple and multifunctional ICD amplifier opens a new window for enhancing ICD effect and immune checkpoint blockade therapy.