A novel and easy to prepare azo-based bioreductive linker and its application in hypoxia-sensitive cationic liposomal doxorubicin: Synthesis, characterization, in vitro and in vivo studies in mice bearing C26 tumor.

This study designed and synthesized a cost-effective azo-based hypoxia-sensitive linker (AHSL) using commercially accessible, inexpensive raw materials and simple methods to apply in cationic nanoliposomes. Then, AHSL was post-inserted into the cationic liposome (Cat-lip), and PEG-Azo-Cat-lip was prepared and characterized using DLS. The decrease in the zeta-potential of formulation from + 18.4 mV for Cat-lip to + 6.1 mV and the increase in the size of the PEG-Azo-Cat-lip indicated the successful post insertion of AHSL into the liposomes. The Doxorubicin (Dox) release study showed that PEGylation results in a more stable PEG-Azo-Cat-lip than the Cat-lip. The increased cytotoxicity of the PEG-Azo-Cat-lip in the hypoxic condition also indicated the cleavage of the AHSL in the hypoxic environment. In vivo biodistribution using animal imaging has shown higher tumor accumulation of the MPEG-Azo-Cat-lip than Cat-lip during the 120 h of the study. The results of anti-tumor activities and biosafety of the formulations also showed the higher efficiency of the MPEG-Azo-Cat-lip compared with the Cat-lip. The results of this study indicated the antitumor efficacy of this hypoxia-sensitive which merits further investigation.

Improving anti-tumour efficacy of PEGylated liposomal doxorubicin by dual targeting of tumour cells and tumour endothelial cells using anti-p32 CGKRK peptide.

The aim of this study was to surface-functionalize PEGylated liposomal doxorubicin (PLD) using anti-p32 CGKRK peptide to evaluate its anti-angiogenic and anti-tumour activities. CGKRK was conjugated to DSPE-mPEG2000-maleimide and post-inserted into PLD at 25, 50, 100, 200 and 400 peptides per each liposome and characterised for their size, zeta potential, drug loading, release properties; and cell binding, cell uptake and cytotoxicity on three C26, 4T1 and human umbilical vein endothelial cell (HUVEC) cell lines. The in vitro results indicated the better efficiency of the PLD-100 (PLD with 100 CGKRK) formulation on 4T1 and HUVEC cell lines. The results of anti-tube formation and spheroid assay indicated the efficiencies of the PLD-100 formulation compared with Caelyx®in vitro. The in vivo studies indicated the higher tumour accumulation of PLD-100 formulation in comparison with Caelyx® which also implied the higher survival rates in mice treated with PLD-100 formulation. Histological evaluations demonstrated that PLD-100 had no side-effects on major organs. In conclusion, the results of this study indicated that PLD-CGKRK- could efficiently target endothelial and tumour parenchymal cells which enhance the therapeutic efficacy of PLD and merits further investigation.

Redox-sensitive nanoscale drug delivery systems for cancer treatment.

Pharmaceutical nanotechnology introduces novel strategies in designing smart nanoscale drug delivery systems (NDDSs) capable of responding to specific conditions. These smart responsive NDDSs respond to specific conditions already established in the tumor microenvironment (TME) resulting in greater drug release following accumulation through enhanced permeation and retention (EPR) effect. Among various specific conditions, reactive oxygen species (ROS) and glutathione (GSH) have been extensively used to improve tumor targeting. While cells of the tumor microenvironment including immune cells, cancer-associated fibroblasts, endothelial cells and tumor invasive cells are responsible for the production and elevation of ROS levels, high levels of GSH inside tumor cells establish highly reducing environment, which in turn maintain cell survival. Abnormal ROS generation in the tumor microenvironment helps with designing highly specific ROS-sensitive NDDSs with the potential to release the payload next to the tumor cells. On the other hand, elevated levels of tumor GSH allows for designing NDDSs bearing reductively cleavable linkage to enhance drug release exploiting the dramatic higher intracellular GSH. The aim of the current review is to emphasize the requirements for developing various NDDSs including liposomes, polymeric nanoparticles, micelles, mesoporous silica nanoparticles, nanogels and prodrugs, capable of responding to TME using their Redox-sensitive moieties.

Endogenous stimuli-responsive linkers in nanoliposomal systems for cancer drug targeting.

There are various drug delivery systems (DDSs) among which nanoliposomal formulations are among the most prominent. Despite the superiority of nanoliposomal DDSs compared to conventional drug delivery methods, recent reports have claimed that they can deliver small amounts of the injected dose to target site by passive targeting. However, our understanding of tumor microenvironment features, including dysregulation of pH, the high intracellular concentration of glutathione, change in the amount and expression of some enzymes, reactive oxygen species, hypoxia, and ATP concentrations, has driven the scope of research into the use of these endogenous stimuli for a design of smart linkers. These linkers optimize the release of payloads in favorable target sites and avoid premature releasing in non-favorable off-target sites. In this review, we discuss particular linkers, which are able to respond to the specific endogenous conditions, and could be used in nanoliposomal DDSs, based on pathophysiological changes that occur in tumors. Furthermore, structural and chemical properties of these linkers and other potential linkers, which could be used in nanoliposomal DDSs, have been reviewed.

Electrochemical-based biosensors for detection of Mycobacterium tuberculosis and tuberculosis biomarkers.

Early detection of tuberculosis (TB) reduces the interval between infection and the beginning of treatment. However, commercially available tests cannot discriminate between BCG-vaccinated healthy persons and patients. Also, they are not suitable to be used for immunocompromised persons. In recent years, biosensors have attracted great attention due to their simple utility, accessibility, and real-time outputs. These sensors are increasingly being considered as pioneering tools for point-of-care diagnostics in communities with a high burden of TB and limited accessibility to reference laboratories. Among other types of biosensors, the electrochemical sensors have the advantages of low-cost operation, fast processing, simultaneous multi-analyte analyzing, operating with turbid samples, comparable sensitivity and readily available miniaturization. Electrochemical biosensors are sub-divided into several categories including: amperometric, impedimetric, potentiometric, and conductometric biosensors. The biorecognition element in electrochemical biosensors is usually based on antibodies (immunosensors), DNAs or PNAs (genosensors), and aptamers (aptasensors). In either case, whether an interaction of the antigen-antibody/aptamer or the hybridization of probe with target mycobacterial DNA is detected, a change in the electrical current occurs that is recorded and displayed as a plot. Therefore, impedimetric-based methods evaluate resistance to electron transfer toward an electrode by a Nyquist plot and amperometric/voltammetric-based methods weigh the electrical current by means of cyclic voltammetry, square wave voltammetry, and differential pulse voltammetry. Electrochemical biosensors provide a promising scope for the new era of diagnostics. As a consequence, they can improve detection of Mycobacterium tuberculosis traces even in attomolar scales.