Protein corona: Friend or foe? Co-opting serum proteins for nanoparticle delivery.

For systemically delivered nanoparticles to reach target tissues, they must first circulate long enough to reach the target and extravasate there. A challenge is that the particles end up engaging with serum proteins and undergo immune cell recognition and premature clearance. The serum protein binding, also known as protein corona formation, is difficult to prevent, even with artificial protection via "stealth" coating. Protein corona may be problematic as it can interfere with the interaction of targeting ligands with tissue-specific receptors and abrogate the so-called active targeting process, hence, the efficiency of drug delivery. However, recent studies show that serum protein binding to circulating nanoparticles may be actively exploited to enhance their downstream delivery. This review summarizes known issues of protein corona and traditional strategies to control the corona, such as avoiding or overriding its formation, as well as emerging efforts to enhance drug delivery to target organs via nanoparticles. It concludes with a discussion of prevailing challenges in exploiting protein corona for nanoparticle development.

Fibroblast activation protein-α-adaptive micelles deliver anti-cancer drugs and reprogram stroma fibrosis.

Cancer-associated fibroblasts (CAFs) are the majority cell population of tumor stroma, and they not only play important roles in tumor growth and metastasis, but they also form a protective physical barrier for cancer cells. Herein, we designed a fibroblast activation protein-α (FAP-α)-adaptive polymeric micelle based on hyaluronic acid and curcumin conjugates. The polymeric micelle is composed of a CD44-targeting shell and a FAP-α-cleavable polyethylene glycol (PEG) coating. When FAP-α is encountered on the surface of CAFs in the tumor microenvironment, the PEG layer is released, hyaluronic acid is recovered on the surface of nanoparticles, and the nanoparticles effectively inhibit the growth of tumor cells and CAFs through CD44-mediated endocytosis. The FAP-α-adaptive polymeric micelle exhibited potent anti-cancer efficacy by enhancing CAF apoptosis and reducing collagen in tumor tissues. Collectively, FAP-α-adaptive nanoparticles may be a promising method for antitumor anticancer treatments via reprogramming of stroma fibrosis.

Doxorubicin delivered by redox-responsive Hyaluronic Acid-Ibuprofen prodrug micelles for treatment of metastatic breast cancer.

During the process of cancer metastasis, various enzymes, cytokines, and factors were involved, and upregulated cyclooxygenase-2(COX-2) in tumor cells led to proliferation and invasion of various tumors. Many nonsteroidal anti-inflammatory drugs (NSAIDs) were used as an anticancer adjuvant in chemotherapy, such as ibuprofen (BF) and celecoxib. NSAIDs could effectively inhibit local inflammation and decreased COX-2 expression. However, most of them have serious toxicity issues due to their limit selectivity against cancer and poor water solubility. Thus hyaluronic acid-ibuprofen (HA-ss-BF), which was sensitive to the reducing environment, was prepared by binding ibuprofen (BF) to the hyaluronic acid backbone through a disulfide bond, and the HA-ss-BF polymer could self-assemble into micelles and serve as carriers to delivery doxorubicin. These redox-sensitive prodrug polymeric micelles hold multiple therapeutic advantages, including on-demand BF release and disassembling micelles responding to redox stimuli, as well as desirable cellular uptake and favorable biodistribution. These advantages indicated the redox-responsive hyaluronic acid-ibuprofen prodrug could be a promising delivery system for metastatic breast cancer treatment.

Desirable PEGylation for improving tumor selectivity of hyaluronic acid-based nanoparticles via low hepatic captured, long circulation times and CD44 receptor-mediated tumor targeting.

PEG coating was regarded as one effective method to improve the tumor-targeting efficiency of hyaluronic acid-based nanoparticles (HBN). However, the research of interaction between PEG coating and different receptors such as stabilin-2 and CD44 was limited. Herein, we synthesized a series of PEGylated hyaluronic acid with Curcumin (PHCs) to evaluate the role of PEG coating density in the interaction between HA and its receptors, which influenced tissues targeting activity, pharmacokinetic profiles and therapeutic efficacy of HBN. Compared with other counterparts, PHC HBN with about 5% PEG coating density preferably accumulated in the tumor mass, rather than in the liver, and hold desirable anti-cancer effect. These results indicated that to obtain optimized anticancer effect of HBN, the cellular uptake efficiency between different types of the cells should be carefully balanced by different PEG densities.

Glycyrrhetinic acid-modified TPGS polymeric micelles for hepatocellular carcinoma-targeted therapy.

In this study, glycyrrhetinic acid (GA)-modified D-α-tocopheryl polyethylene glycol 1000 succinate (TPGS) polymeric micelles (TGA PMs) were developed for the delivery of etoposide (ETO) to hepatoma cells. GA was incorporated as a ligand because of its high affinity to the hepatocytes, while TPGS functioned as a P-gp inhibitor to reverse multidrug resistance. ETO-loaded TGA PMs (ETO-TGA PMs) displayed a mean particle size of 133.6±1.2nm with a low poly-dispersity index (0.224±0.013) and negative zeta potential (-16.30mV). The drug loading and entrapment efficiency of ETO-TGA PMs were 10.4% and 79.8%, respectively. ETO-TGA PMs also exhibited faster drug release behavior at pH 5.8 and relatively stable drug release at pH 7.4. Confocal laser scanning microscope (CLSM) observations and in vivo imaging studies revealed that TGA PMs displayed higher cellular uptake and selective accumulation at the tumor site, indicating good tumor targetability. Furthermore, ETO-TGA PMs displayed significant cytotoxicity towards HepG2 cells and higher anti-tumor efficacy (75.96%), compared to the control group. This could be due to TGA-mediated targeted drug delivery to the hepatocytes as well as P-gp inhibition. These findings suggest that TGA PMs have the potential to be used as a targeted drug delivery system for hepatic cancer therapy.

Chitosan nanoparticles and their Tween 80 modified counterparts disrupt the developmental profile of zebrafish embryos.

Chitosan nanoparticles (CS-NPs) and their Tween 80 modified counterparts (TmCS-NPs) are among the most commonly used brain-targeted vehicles. However, their potential developmental toxicity is poorly understood. In this study, zebrafish embryos are introduced as an in vivo platform. Both NPs showed a dose-dependent increase in developmental toxicity (decreased hatching rate, increased mortality and incidences of malformation). Neurobehavioral changes included decreased spontaneous movement in TmCS-NP treated embryos and hyperactive effect in CS-NP treated larvae. Both NPs remarkably inhibited axonal development of primary and secondary motor neurons, and affected the muscle structure. Overall, this study demonstrated that CS-NPs and TmCS-NPs could affect embryonic development, disrupt neurobehavior of zebrafish larvae and affect muscle and neuron development, suggesting more attention on biodegradable chitosan nanoparticles.

Brain Localization and Neurotoxicity Evaluation of Polysorbate 80-Modified Chitosan Nanoparticles in Rats.

The toxicity evaluation of inorganic nanoparticles has been reported by an increasing number of studies, but toxicity studies concerned with biodegradable nanoparticles, especially the neurotoxicity evaluation, are still limited. For example, the potential neurotoxicity of Polysorbate 80-modified chitosan nanoparticles (Tween 80-modified chitosan nanoparticles, TmCS-NPs), one of the most widely used brain targeting vehicles, remains unknown. In the present study, TmCS-NPs with a particle size of 240 nm were firstly prepared by ionic cross-linking of chitosan with tripolyphosphate. Then, these TmCS-NPs were demonstrated to be entered into the brain and specially deposited in the frontal cortex and cerebellum after systemic injection. Moreover, the concentration of TmCS-NPs in these two regions was found to decrease over time. Although no obvious changes were observed for oxidative stress in the in vivo rat model, the body weight was found to remarkably decreased in a dose-dependent manner after exposure to TmCS-NPs for seven days. Besides, apoptosis and necrosis of neurons, slight inflammatory response in the frontal cortex, and decrease of GFAP expression in the cerebellum were also detected in mouse injected with TmCS-NPs. This study is the first report on the sub-brain biodistribution and neurotoxicity studies of TmCS-NPs. Our results provide new insights into the toxicity evaluation of nanoparticles and our findings would help contribute to a better understanding of the neurotoxicity of biodegradable nanomaterials used in pharmaceutics.

Gene recombinant bone marrow mesenchymal stem cells as a tumor-targeted suicide gene delivery vehicle in pulmonary metastasis therapy using non-viral transfection.

One of the main limitations of anti-tumor gene therapy is the lack of an effective way to deliver therapeutic genes to tumor sites. Bone marrow mesenchymal stem cells (BMSCs) have been proposed as cellular delivery vehicles to tumor sites in tumor-targeted cancer gene therapy. Here, we investigated the therapeutic effects of cytomegalovirus-thymidine kinase expressing BMSCs (TK-BMSCs) on pulmonary melanoma metastasis combined with prodrug ganciclovir. BMSCs were successfully engineered through a non-viral gene vector. The gene recombinant BMSCs migrated to the pulmonary area and were found to have the tendency to target tumor nodules after systemic delivery. In vitro results demonstrate that the engineered BMSCs have significant suicide effects in the presence of ganciclovir in a dose-dependent manner and can exert a sufficient bystander effect on B16F10 tumor cells in co-culture experiments. In vivo studies confirmed the therapeutic effects of TK-BMSCs/ganciclovir on the metastasis tumor model. FROM THE CLINICAL EDITOR: This study investigates the possibility of gene transfer via bone marrow mesenchymal stem cells in anti-cancer gene therapy using a metastatic melanoma model and cytomegalovirus-thymidine kinase expressing stem cells, demonstrating clear therapeutic effects.