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Abstract Combined chemotherapy and targeted therapy holds immense potential in the management of advanced gastric cancer (GC). GC tissues exhibit an elevated expression level of protein kinase B (AKT), which contributes to disease progression and poor chemotherapeutic responsiveness. Inhibition of AKT expression through an AKT inhibitor, capivasertib (CAP), to enhance cytotoxicity of paclitaxel (PTX) toward GC cells is demonstrated in this study. A cathepsin B‐responsive polymeric nanoparticle prodrug system is employed for co‐delivery of PTX and CAP, resulting in a polymeric nano‐drug BPGP@CAP. The release of PTX and CAP is triggered in an environment with overexpressed cathepsin B upon lysosomal uptake of BPGP@CAP. A synergistic therapeutic effect of PTX and CAP on killing GC cells is confirmed by in vitro and in vivo experiments. Mechanistic investigations suggested that CAP may inhibit AKT expression, leading to suppression of the phosphoinositide 3‐kinase (PI3K)/AKT signaling pathway. Encouragingly, CAP can synergize with PTX to exert potent antitumor effects against GC after they are co‐delivered via a polymeric drug delivery system, and this delivery system helped reduce their toxic side effects, which provides an effective therapeutic strategy for treating GC.

Abstract Herein, two water‐soluble PROXYL‐based magnetic resonance imaging (MRI) macromolecular organic contrast agents (mORCAs) are designed and synthesized: linear and cross‐linked PCE‐mPEG‐Ppa‐PROXYL. They are prepared by conjugating linear and cross‐linked poly(carboxylate ester) (PCE) with poly(ethylene glycol) (mPEG2000)‐modified nitroxides (PROXYL), respectively. Both mORCAs form self‐assembled aggregates in an aqueous phase and PROXYL is protected inside a hydrophobic core to achieve great resistance to reduction in the physiological environment, and they have low toxicity. Since cross‐linked PCE‐mPEG‐Ppa‐PROXYL possess a branched architecture, its self‐assembled aggregate is more stable and compact with a greater particle size. Cross‐linked PCE‐mPEG‐Ppa‐PROXYL outperform the linear one in the following aspects: 1) its longitudinal relaxivity (r1 = 0.79 mm−1 s−1) is higher than that of the linear one (r1 = 0.64 mm−1 s−1) and both excel the best mORCA reported so far (r1 = 0.42 mm−1 s−1); 2) its blood retention time (≈48 h) is longer than that of its linear counterpart (≈10 h); 3) cross‐linked PCE‐mPEG‐Ppa‐PROXYL provided better MR imaging contrast resolution in normal organs (liver and kidney) and tumor of mice than the linear one. Overall, cross‐linked PCE‐mPEG‐Ppa‐PROXYL may have great potential to be a novel metal‐free macromolecular contrast agent for MR imaging.

Abstract A stimuli‐responsive polymeric prodrug‐based nanotheranostic system with imaging agents (cyanine5.5 and gadolinium‐chelates) and a therapeutic agent paclitaxel (PTX) is prepared via polymerization and conjugating chemistry. The branched polymeric PTX‐Gd‐based nanoparticles (BP‐PTX‐Gd NPs) demonstrate excellent biocompatibility, and high stability under physiological conditions, but they stimuli‐responsively degrade and release PTX rapidly in a tumor microenvironment. The in vitro behavior of NPs labeled with fluorescent dyes is effectively monitored, and the NPs display high cytotoxicity to 4T1 cells similar to free PTX by impairing the function of microtubules, downregulating anti‐apoptotic protein Bcl‐2, and upregulating the expression of Bax, cleaved caspase‐3, cleaved caspase‐9, cleaved‐PARP, and p53 proteins. Great improvement in magnetic resonance imaging (MRI) is demonstrated by these NPs, and MRI accurately maps the temporal change profile of the tumor volume after injection of NPs and the tumor treatment process is also closely correlated with the T1 values measured from MRI, demonstrating the capability of providing real‐time feedback to the chemotherapeutic treatment effectiveness. The imaging‐guided chemotherapy to the 4T1 tumor in the mice model achieves an excellent anti‐tumor effect. This stimuli‐responsive polymeric nano‐agent opens a new door for efficient breast cancer treatment under the guidance of fluorescence/MRI.