Cell-penetrating peptides (CPPs), also known as protein transduction domains, are a class of diverse amino acid sequences with the ability to cross cellular membranes. CPPs can deliver several bioactive cargos, including proteins, peptides, nucleic acids and chemotherapeutics, into cells. Ever since their discovery, synthetic and natural CPPs have been utilized in therapeutics delivery, gene editing and cell imaging in fundamental research and clinical experiments. Over the years, CPPs have gained significant attention due to their low cytotoxicity and high transduction efficacy. In the last decade, multiple investigations demonstrated the potential of CPPs as carriers for the delivery of therapeutics to treat various types of cancer. Besides their remarkable efficacy owing to fast and efficient delivery, a crucial benefit of CPP-based cancer treatments is delivering anticancer agents selectively, rather than mediating toxicities toward normal tissues. To obtain a higher therapeutic index and to improve cell and tissue selectivity, CPP-cargo constructions can also be complexed with other agents such as nanocarriers and liposomes to obtain encouraging outcomes. This review summarizes various types of CPPs conjugated to anticancer cargos. Furthermore, we present a brief history of CPP utilization as delivery systems for anticancer agents in the last decade and evaluate several reports on the applications of CPPs in basic research and preclinical studies.

Background Green synthesis of nanoparticles by plant extracts plays a significant role in different applications. Recently, several studies were conducted on the use of nanoparticles as adjuvant. The main aim of this study was to evaluate green synthesized silver nanoparticles (AgNPs) as adjuvant in rabies veterinary vaccine and compare the results with the existing commercially available alum adjuvant. Materials and methods In the current study, AgNPs were prepared by the reduction of aqueous silver nitrate by leaf extract of Eucalyptus procera . The formation of AgNPs was confirmed by ultraviolet (UV)–visible spectrophotometer, scanning electron microscopy, dynamic light scattering, and X-ray diffraction analysis. Then, different amounts of AgNPs (200 µg, 400 µg, 600 µg, and 800 µg) were added to 1 mL of inactivated rabies virus. The loaded vaccines (0.5 mL) were injected intraperitoneally into six Naval Medical Research Institute mice in each group on days 1 and 7. On the 15th day, the mice were intracerebrally challenged with 0.03 mL of challenge rabies virus (challenge virus strain-11, 20 lethal dose [20 LD 50 ]), and after the latency period of rabies disease in mice (5 days), the mice were monitored for 21 days. Neutralizing antibodies against rabies virus were also investigated using the rapid fluorescent focus inhibition test method. The National Institutes of Health test was performed to determine the potency of optimum concentration of AgNPs as adjuvant. In vitro toxicity of AgNPs was assessed in L929 cell line using MTT assay. In addition, in vivo toxicity of AgNPs and AgNPs-loaded vaccine was investigated according to the European Pharmacopeia 8.0. Results AgNPs were successfully synthesized, and the identity was confirmed by UV–visible spectrophotometry and X-ray diffraction analysis. The prepared AgNPs were spherical in shape, with an average size of 60 nm and a negative zeta potential of −14 mV as determined by dynamic light scattering technique. The highest percentage of viability was observed at 15 mg/kg and 20 mg/kg of AgNPs-loaded vaccine concentrations after injecting into the mice. The calculated potencies for alum-containing vaccine and AgNPs-loaded vaccine (dose 15 mg/kg) were 1.897 and 1.303, respectively. MTT assay demonstrated that alum at the concentration of 10 mg/mL was toxic, but AgNPs were not toxic. The in vivo toxicity also elucidated the safety of AgNPs and AgNPs-loaded vaccine in mice and dogs, respectively. Conclusion In the current study, for the first time, the adjuvanticity effect of green synthesized AgNPs on veterinary rabies vaccine potency with no in vivo toxicity was elucidated according to the European Pharmacopeia 8.0.

No abstract

For induction of an appropriate immune response, especially in the case of an inactivated vaccine, the use of an adjuvant is crucial. In this study, adjuvanticity effect of G2 dendrimer in veterinary rabies vaccine has been investigated. A nonlinear globular G2 dendrimer comprising citric acid and polyethylene glycol 600 (PEG-600) was synthesized and the toxicity was studied in vitro on the J774A.1 cell line. The adjuvanticity effect of the dendrimer was then investigated on rabies virus in NMRI mice as a model. Different concentrations of dendrimer were used to determine the best formulation for the survival of the mice after virus challenge. The rise of neutralizing antibody was also checked by rapid fluorescent focus inhibition test (RFFIT). The relative potency of the prepared formulation was finally calculated using standard NIH test and the results were compared (and discussed) with the commercially available rabies vaccine. The accuracy of dendrimer synthesis was confirmed using Fourier transform infrared (FT-IR), size, and zeta potential analysis. The in vitro toxicity assay revealed that no significant toxic effect is observed in cells when data are compared with the control group. The in vivo assay showed that a higher survival rate in the mice received a special formulation due to adjuvanticity effect of dendrimer, which is also confirmed by RFFIT. However, the relative potency of that formulation does not give expected results when compared with the alum-containing rabies vaccine. In the current investigation, the adjuvanticity effect of G2 dendrimer was demonstrated for the first time in rising of neutralizing antibodies against rabies virus. Our data confirm that nanoparticles can enhance immune responses in an appropriate manner. Moreover, engineered nanoparticles will enable us to develop novel potent multivalent adjuvants in vaccine technology.