Proanthocyanidins (PAs) possess superior antioxidant properties and nutritious value, however, low bioavailability and stability limit their applications. Here, we developed a novel method to encapsulate PA dimers successfully into horse spleen apoferritin (apoHSF) using a disassembly/reassembly method based on pH change. The PA-HSF nanoparticles were characterized using fluorescence spectroscopy, transmission electron microscopy, circular dichroism, and high-performance liquid chromatography. One apoferritin cage could approximately encapsulate 25.6 molecules of the PA dimer. The results showed that the encapsulation of the PA dimers protected it from the damage of oxidants and temperature below room temperature would be an appropriate condition for HSF-578 solution storage. Moreover, HepG2 cell monolayer absorption and adhesion analyses indicated that the PA dimers encapsulated within apoHSF cages were more efficient in transport. In addition, it was indicated that the PA-HSF nanoparticles had higher cellular antioxidant activity. The novel strategy provided in this study indicates that the protein cage structures like ferritin have potential to be applied in the field of food nutrition.

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As a natural sesquiterpene compound with numerous biological activities, α-santalene has extensive applications in the cosmetic and pharmaceutical industries. Although several α-santalene-producing microbial strains have been constructed, low productivity still hampers large-scale fermentation. Herein, we present a case of engineered sesquiterpene biosynthesis where the insufficient downstream pathway capacity limited high-level α-santalene production in Escherichia coli. The initial strain was constructed, and it produced 6.4 mg/L α-santalene. To increase α-santalene biosynthesis, we amplified the flux toward farnesyl diphosphate (FPP) precursor by screening and choosing the right FPP synthase and reprogrammed the rate-limiting downstream pathway by generating mutations in santalene synthase (Clausena lansium; ClSS). Santalene synthase was engineered by site-directed mutagenesis, resulting in the improved soluble expression of ClSS and an α-santalene titer of 887.5 mg/L; the α-santalene titer reached 1078.8 mg/L after adding a fusion tag to ClSS. The most productive pathway, which included combining precursor flux amplification and mutant synthases, conferred an approximate 169-fold increase in α-santalene levels. Maximum titers of 1272 and 2916 mg/L were achieved under shake flask and fed-batch fermentation, respectively, and were among the highest levels reported using E. coli as the host.

The application of drug delivery systems based on ferritin nanocarrier has been developed as a potential strategy in cancer therapy. The limited permeability of ferritin remains a challenge for drug penetration into the deeper tumor tissues. CendR peptides have been reported to bear tumor-specific penetration by recognizing neuropilin (NRP-1) receptor that overexpressed on a wide range of cancer cells. Herein, we modified CendR peptide L(RGERPPR), its retro-inverso peptide D(RPPREGR), and inverso peptide D(RGERPPR) on the outer surface of human H chain ferritin by sulfhydryl-maleimide coupling reaction. Approximately 45 paclitaxel (PTX) molecules could be loaded into each ferritin inner cavity by a thermal-triggered method at a specific ionic strength. The penetration ability of three peptide-modified ferritin constructs showed that D(RGERPPR)-modified HFtn was able to be engulfed by A549 and MCF-7 tumor cells and spheroids at the highest level. Due to the dual-targeting effect of ferritin and modified peptides, the PTX-loaded nanocomposites could effectively enter the cells with high expression of TfR1 and NRP-1 receptors and enhanced the cytotoxicity against tumor cells. Remarkably, H-D(RGE)-PTX displayed a superior tumor growth suppression efficacy in A549 tumor-bearing nude mice. The inverso CendR peptide-modified HFtn nanocarrier was first generated and could provide an effective dual-targeting platform for treatment of cancers.

The biocompatible protein nanocarrier with homogeneous particle size is a promising candidate material for the delivery of targeted drugs to tumors. Doxorubicin (DOX) is a commonly prescribed anthracycline antitumor drug, although it may cause nephrotoxicity and cardiotoxicity. The Chinese herbal remedy ursolic acid (UA), a pentacyclic triterpenoid with anticancer action, has been used as a potential drug sensitizer to increase the effectiveness of chemotherapy and pharmacological therapy. Therefore, the dose of DOX can be reduced by compatibility with UA to lower its side effects. Ferritin binds to tumor cells through an interaction with the transferrin receptor 1 (TfR1), which is overexpressed in human cancer cells. In this study, the hydrophobic drug UA and the hydrophilic drug DOX were successfully encapsulated into the ferritin inner cavity using the thermal treatment method incubated at 60 °C for 4 h. The results demonstrated that loaded ferritin could specifically enter breast cancer cells MCF-7 and non-small-cell lung cancer cells A549 in comparison with free UA and DOX, enhancing their therapeutic effects. The loading ratio of two drugs was optimized in the constructed nanocarriers, and the effectiveness of the constructed nanodrugs in inhibiting tumor proliferation was verified by cell apoptosis and three-dimensional (3D) tumor spheroids studies. For the first time, the hydrophilic and hydrophobic drugs were loaded simultaneously within unmodified ferritin without other addition of additives, which would reduce the toxic side effects of DOX and enhance its therapeutic effect. This study also showed that the ferritin-based nanocarrier has potential for drug delivery to tumors.