A cleavable peptide adapter augments the activity of targeted toxins in combination with the glycosidic endosomal escape enhancer SO1861.

BACKGROUND: Treatment with tumor-targeted toxins attempts to overcome the disadvantages of conventional cancer therapies by directing a drug's cytotoxic effect specifically towards cancer cells. However, success with targeted toxins has been hampered as the constructs commonly remain bound to the outside of the cell or, after receptor-mediated endocytosis, are either transported back to the cell surface or undergo degradation in lysosomes. Hence, solutions to ensure endosomal escape are an urgent need in treatment with targeted toxins. In this work, a molecular adapter that consists of a cell penetrating peptide and two cleavable peptides was inserted into a targeted toxin between the ribosome-inactivating protein dianthin and the epidermal growth factor. Applying cell viability assays, this study examined whether the addition of the adapter further augments the endosomal escape enhancement of the glycosylated triterpenoid SO1861, which has shown up to more than 1000-fold enhancement in the past. RESULTS: Introducing the peptide adapter into the targeted toxin led to an about 12-fold enhancement in the cytotoxicity on target cells while SO1861 caused a 430-fold increase. However, the combination of adapter and glycosylated triterpenoid resulted in a more than 4300-fold enhancement and in addition to a 51-fold gain in specificity. CONCLUSIONS: Our results demonstrated that the cleavable peptide augments the endosomal escape mediated by glycosylated triterpenoids while maintaining specificity. Thus, the adapter is a promising addition to glycosylated triterpenoids to further increase the efficacy and therapeutic window of targeted toxins.

Magnetic Nanoparticle-Based Dianthin Targeting for Controlled Drug Release Using the Endosomal Escape Enhancer SO1861.

Targeted tumor therapy can provide the basis for the inhibition of tumor growth. However, a number of toxin-based therapeutics lack efficacy because of insufficient endosomal escape after being internalized by endocytosis. To address this problem, the potential of glycosylated triterpenoids, such as SO1861, as endosomal escape enhancers (EEE) for superparamagnetic iron oxide nanoparticle (SPION)-based toxin therapy was investigated. Herein, two different SPION-based particle systems were synthesized, each selectively functionalized with either the targeted toxin, dianthin-epidermal growth factor (DiaEGF), or the EEE, SO1861. After applying both particle systems in vitro, an almost 2000-fold enhancement in tumor cell cytotoxicity compared to the monotherapy with SPION-DiaEGF and a 6.7-fold gain in specificity was observed. Thus, the required dose of the formulation was appreciably reduced, and the therapeutic window widened.

Optimizing Circulating Tumor Cells' Capture Efficiency of Magnetic Nanogels by Transferrin Decoration.

Magnetic nanogels (MNGs) are designed to have all the required features for their use as highly efficient trapping materials in the challenging task of selectively capturing circulating tumor cells (CTCs) from the bloodstream. Advantageously, the discrimination of CTCs from hematological cells, which is a key factor in the capturing process, can be optimized by finely tuning the polymers used to link the targeting moiety to the MNG. We describe herein the relationship between the capturing efficiency of CTCs with overexpressed transferrin receptors and the different strategies on the polymer used as linker to decorate these MNGs with transferrin (Tf). Heterobifunctional polyethylene glycol (PEG) linkers with different molecular weights were coupled to Tf in different ratios. Optimal values over 80% CTC capture efficiency were obtained when 3 PEG linkers with a length of 8 ethylene glycol (EG) units were used, which reveals the important role of the linker in the design of a CTC-sorting system.

Near Infrared Dye Conjugated Nanogels for Combined Photodynamic and Photothermal Therapies.

There is a need for new and smart formulations that will help overcome the limitations of organic dyes used in photodynamic (PDT) and photothermal (PTT) therapy and significantly accelerate their clinical translation. Therefore the aim of this work was to create a responsive nanogel scaffold as a smart vehicle for dye administration. We developed a methodology that enables the conjugation of organic dyes to thermoresponsive nanogels and yields biocompatible, nanometer-sized products with low polydispersity. The potential of the dye-nanogel conjugate as a photothermal and photodynamic agent has been demonstrated by an in vitro evaluation with a model human carcinoma cell line. Additionally, confocal cell images showed their cellular uptake profile and their potential for bioimaging and intracellular drug delivery. These conjugates are a promising scaffold as a theranostic agents and will enable further applications in combination with controlled drug release.

Effects of thermoresponsivity and softness on skin penetration and cellular uptake of polyglycerol-based nanogels.

Nanogels are water soluble cross-linked polymer networks with nanometer size dimensions that can be designed to incorporate different types of compounds and are promising carrier systems for drugs and biological molecules. In this study, the interactions of thermoresponsive nanogels (tNGs) with the human skin barrier and underlying epidermis cells were investigated with the aim of using such macromolecules to improve dermal and transdermal drug delivery. The investigated tNGs were made of acrylated dendritic polyglycerol, as water soluble cross-linker, and of oligo ethylene glycol methacrylate (OEGMA) as subunit conferring thermoresponsive properties. tNGs with different polymer transition temperatures were tagged with Rhodamine B (RhdB) and analyzed for their physicochemical properties. We found that tNGs with cloud point temperatures (Tcps) of 38 °C (tNG-RhdB-T38) lost softness (measured by PeakForce quantitative nanomechanics, QNM) and aggregated to bigger sized particles (measured as increase of particle average size by dynamic light scattering, DLS) when temperature changed from 15 to 37 °C. On the contrary, at the same conditions, tNGs with higher Tcps (tNG-RhdB-T55) did not show any significant changes of these characteristics. Applied on excised human skin, both tNGs penetrated deep in the stratum corneum (SC). Small amounts of tNGs were detected also in cells of the viable epidermis. Interestingly, whereas tNG softness correlated with higher penetration in SC, a better cellular uptake was observed for the thermoresponsive tNG-RhdB-T38. We conclude that soft nanocarriers possess a high SC penetration ability and that thermoresponsive nanogels are attractive carrier systems for the targeting of drugs to epidermis cells.

Transferrin Decorated Thermoresponsive Nanogels as Magnetic Trap Devices for Circulating Tumor Cells.

A rational design of magnetic capturing nanodevices, based on a specific interaction with circulating tumor cells (CTCs), can advance the capturing efficiency and initiate the development of modern smart nanoformulations for rapid isolation and detection of these CTCs from the bloodstream. Therefore, the development and evaluation of magnetic nanogels (MNGs) based on magnetic nanoparticles and linear thermoresponsive polyglycerol for the capturing of CTCs with overexpressed transferrin (Tf(+) ) receptors has been presented in this study. The MNGs are synthesized using a strain-promoted "click" approach which has allowed the in situ surface decoration with Tf-polyethylene glycol (PEG) ligands of three different PEG chain lengths as targeting ligands. An optimal value of around 30% of cells captures is achieved with a linker of eight ethylene glycol units. This study shows the potential of MNGs for the capture of CTCs and the necessity of precise control over the linkage of the targeting moiety to the capturing device.

Stimuli-responsive nanogel composites and their application in nanomedicine.

Nanogels are nanosized crosslinked polymer networks capable of absorbing large quantities of water. Specifically, smart nanogels are interesting because of their ability to respond to biomedically relevant changes like pH, temperature, etc. In the last few decades, hybrid nanogels or composites have been developed to overcome the ever increasing demand for new materials in this field. In this context, a hybrid refers to nanogels combined with different polymers and/or with nanoparticles such as plasmonic, magnetic, and carbonaceous nanoparticles, among others. Research activities are focused nowadays on using multifunctional hybrid nanogels in nanomedicine, not only as drug carriers but also as imaging and theranostic agents. In this review, we will describe nanogels, particularly in the form of composites or hybrids applied in nanomedicine.