Introduction

The discussion about cancer treatment has a long history. Chemotherapy, one of the promising approaches in cancer therapy, is limited in the clinic as plenty of factors evolve and prevent appropriate therapeutic response to drugs. Multi-drug resistance (MDR), which is mostly P-glycoprotein-mediated, is described as the most well-known impediment in this contribution. It extrudes several agents out of cells, arising MDR and decreasing the bioavailability of drugs. Hence, cancer cells become insensitive to chemotherapy.

Areas covered

Many agents have been developed to reverse MDR, but it is difficult to deliver them into cancer sites and cancer cells. The emerging nano-based drug delivery systems have been more effective to overcome P-glycoprotein-mediated MDR by increasing the intracellular delivery of these agents. Here, we represent systems including siRNA-targeted inhibition of P-gp, monoclonal antibodies, natural extracts, conventional inhibitors, hard nanoparticles and soft nanoparticles as delivery systems in addition to a novel approach applying cell penetrating peptides.

Expert opinion

Overcoming cancer drug resistance using innovative nanotechnology is being increasingly used and developed. Among resistance mechanisms, drug efflux transporter inhibitors and MDR gene expression silencing are among the those being investigated. In the near future, it seems some of these nanomedical approaches might become the mainstay of effective treatment of important human conditions like cancer.

Nanotechnology increasingly plays a significant role in modern medicine development. The clear benefits of using nanomaterials in various biomedical applications are often challenged by concerns about the lack of adequate data regarding their toxicity. Two decades of nanotoxicology research have shown that the interactions between nanoparticles (NPs) and biosystem are remarkably complex. This complexity derives from NPs' ability to bind and interact with biological cells and change their surface characteristics. One area of interest involves the interactions between NPs and the immune component. Immune system's function in the maintenance of tissue homeostasis is to protect the host from unfamiliar agents. This is done through effective surveillance and elimination of foreign substances and abnormal self cells from the body. Research shows that nanomaterials can stimulate and/or suppress the immune responses, and that their compatibility with the immune system is largely determined by their surface properties. NP size, shape, composition, protein binding and administration routes seem to be the main factors that contribute to the interactions of NPs with the immune system. In the present article, we focus on the relationship between effective physiochemical properties of NPs and their immunogenic effects. In addition, we review more details about immunological responses of different types of NPs. Understanding the interactions of nanomaterials with the immune system is essential for the engineering of new NP-based systems for medical applications.

Objectives

Doxorubicin (Dox) is one of the most well-known chemotherapeutics that are commonly applied for a wide range of cancer treatments. However, in most cases, efflux pumps like P-glycoprotein (P-gp), expel the taken drugs out of the cell and decrease the Dox bioavailability. Expression of P-gp is associated with elevated mRNA expression of the ATP-binding cassette B1 (ABCB1) gene.

Materials and methods

In the current study, different sequences of cell-penetrating peptides (CPPs) containing tryptophan, lysine, and arginine and their nano-complexes were synthesized and their impact on the expression and activity of the ABCB1 gene was evaluated in the A549 lung carcinoma cell line. Furthermore, the cellular uptake of designed CPPs in the A549 cell line was assessed.

Results

The designed peptides, including [W4K4], [WR]3-QGR, R10, and K10 increased Dox cytotoxicity after 48 hr. Furthermore, arginine-rich peptides showed higher cellular uptake. Rhodamin123 accumulation studies illustrated that all the obtained peptides could successfully inhibit the P-gp pump. The designed peptides inhibited the ABCB1 gene expression, of which, [W4K4] resulted in the lowest expression ratio.

Conclusion

[W4K4], [WR]3-QGR, R10, and K10 could successfully increase the Dox cytotoxicity by decreasing the efflux pump gene expression.

PURPOSE:To assess the effect of "N-Acetylation and C-Amidation" on the cellular uptake, cytotoxicity and performance of amphiphilic cell penetrating peptides (CPP) loaded with methotrexate (MTX). METHODS:Several CPPs were synthesized by solid phase peptide synthesis method. Some of these sequences were modified with pyroglutamic acid at N-terminus and benzylamine or memantine at C-terminus. The resultant nanomaterials were prepared due to the physical linkage between CPPs and MTX. The internalization and cytotoxicity of both CPP-MTX bioconjugates and unmodified CPPs against MCF-7 human breast adenocarcinoma cells was evaluated. RESULTS:N-l and C-terminal modification did not alter the toxicity of CPPs. Physical linkage of CPPs with MTX resulted in a lower drug loading efficiency in comparison with chemically conjugated CPP-MTX bio-conjugates. Both nano-complexes increase the toxic effect of MTX on MCF-7 cells. Furthermore, N- and C-terminal modification may cause a tangible reduction in cellular uptake of CPPs. CONCLUSION:In conclusion, it was shown that cytotoxicity of modified peptides which were physically linked with MTX, considerably higher than both physically loaded unmodified peptides and chemically conjugated peptides with MTX. Also, cell internalization was reduced after peptide end-protection. These findings confirmed the effectiveness of N- and C-terminal modifications on cell viability and CPPs internalization.

Methotrexate (MTX) is one of the most effective therapeutics to treat different types of solid tumors; however, it suffers low permeability limiting its bioavailability and cellular uptake. To tackle this, we aim to design and fabricate different types of cell-penetrating peptides (CPPs) to improve the intracellular uptake of MTX without causing any immunogenic response. CPPs were synthesized by the solid-phase peptide synthesis method. Peptide-MTX conjugates were prepared via covalent binding of peptide and drug molecule. CPPs and peptide-E₈ nanoparticles were characterized using zeta-sizer and scanning electron microscopy. Cytotoxicity of CPPs and peptide-MTX conjugates was evaluated by MTT assay. An enzyme-linked immunosorbent assay was employed to assess the IL-6 and TNF-α cytokine release profile. Amongst all sequences, W₄R₄-MTX possessed the highest loading efficiency (97%) and drug to peptide percentage (24.02%). The lowest loading efficiency (36%) and drug to peptide percentage (8.76%) were seen for NGRWK-MTX conjugates. The NGRWR peptide and NGRWR-E₈ nanoparticles had acceptable size (~100 nm) with spherical and rod-like structures, respectively. The selected CPPs and peptide-MTX conjugates did not show any cytotoxicity or immunogenicity. The fabricated peptides are represented as promising carriers to improve the intracellular delivery of MTX to cancer cells with low immunogenic and cytotoxic effects on normal cells.