Non-Clinical Investigation of Tuberculosis Drugs: Conjugated Norbornene- Based Nanocarriers Toxic Impacts on Zebrafish

INTRODUCTION:

Rifampicin conjugated (R-CP), and rifampicin -isoniazid dual conjugated (RI-CP) norbornene-derived nanocarriers are newly designed for pH stimuli-responsive delivery of tuberculosis (TB) drugs. Its biosafety level is yet to be well established.

OBJECTIVES:

To assess the impacts of the nanocarriers on liver cells using zebrafish animal model and human liver cell line model (HepG2).

METHODS:

Initially, lethal dose concentration for the norbornene-derived nanocarrier systems in zebrafish was determined. The toxic effects were analysed at the sub-lethal drug concentration by histopathological study, total GSH level, gene expression and DNA damage in zebrafish liver cells. Fish erythrocyte nuclear abnormalities were also evaluated. Cell viability and oxidative stress level (ROS generation) after exposure to the nanoconjugates was determined using HepG2 cell in the in vitro study.

RESULTS:

In vivo studies of both R-CP and RI-CP showed 100% mortality at 96 hours for exposure concentration >100mg/l and showed toxic changes in zebrafish liver histology, GSH, and DNA damage levels. A noticeable upregulated PXR, CYP3A and cyp2p6 genes was observed in RI-CP exposure than in RIF or R-CP molecules. The in vitro study revealed a dose-dependent effect on cell viability and ROS generation for RIF, R-CP and RI-CP exposures in HepG2 cells.

CONCLUSION:

The current study reports that the rifampicin conjugated (R-CP) and rifampicin-isoniazid conjugated (RI-CP) norbornene derived nanocarriers exhibit enhanced toxic responses in both adult zebrafish and HepG2 cells. The pH-sensitive norbornene derived nanocarriers on conjugation with different drugs exhibited varied impacts on hepatic cells. Hence the present investigation recommends a complete metabolomics analysis and norbornene carrier-drug interaction study to be performed for each drug conjugated norbornene nanocarrier to ensure its biosafety.

Near-Infrared Fluorescent Micelles from Poly(norbornene) Brush Triblock Copolymers for Nanotheranostics

This contribution describes the design and synthesis of multifunctional micelles based on amphiphilic brush block copolymers (BBCPs) for imaging and selective drug delivery of natural anticancer compounds. Well-defined BBCPs were synthesized via one-pot multi-step sequential grafting-through ring-opening metathesis polymerization (ROMP) of norbornene-based macroinitiators. The norbornenes employed contain a poly(ethylene glycol) methyl ether chain, an alkyl bromide chain, and/or a near-infrared (NIR) fluorescent cyanine dye. After block copolymerization, post-polymerization transformations using bromide-azide substitution, followed by the strain-promoted azide-alkyne cycloaddition (SPAAC) allowed for the functionalization of the BBCPs with the piplartine (PPT) moiety, a natural product with well-documented cytotoxicity against cancer cell lines, via an ester linker between the drug and the polymer side chain. The amphiphilic BBCPs self-assembled in aqueous media into nano-sized spherical micelles with neutral surface charges, as confirmed by dynamic light scattering analysis and transmission electron microscopy. During self-assembly, paclitaxel (PTX) could be effectively encapsulated into the hydrophobic core to form stable PTX-loaded micelles with high loading capacities and encapsulation efficiencies. The NIR fluorescent dye-containing micelles exhibited remarkable photophysical properties, excellent colloidal stability under physiological conditions, and a pH-induced disassembly under slightly acidic conditions, allowing for the release of the drug in a controlled manner. The in vitro studies demonstrated that the micelles without the drug (blank micelles) are biocompatible at concentrations of up to 1 mg mL^-1 and present a high cellular internalization capacity toward MCF-7 cancer cells. The drug-functionalized micelles showed in vitro cytotoxicity comparable to free PPT and PTX against MCF-7 and PC3 cancer cells, confirming efficient drug release into the tumor environment upon cellular internalization. Furthermore, the drug-functionalized micelles exhibited higher selectivity than the pristine drugs and preferential cellular uptake in human cancer cell lines (MCF-7 and PC3) when compared to the normal breast cell line (MCF10A). This study provides an efficient strategy for the development of versatile polymeric nanosystems for drug delivery and image-guided diagnostics. Notably, the easy functionalization of BBCP side chains via SPAAC opens up the possibility for the preparation of a library of multifunctional systems containing other drugs or functionalities, such as target groups for recognition.

Efficient Design to Monitor the Site-specific Sustained Release of a Non-Emissive Anticancer Drug

A pH-responsive smart nanocarrier with significant components was synthesized by conjugating the non-emissive anticancer drug methyl orange and polyethylene glycol derived folate moiety to the backbone of polynorbornene. Complete synthesis procedure and characterization methods of three monomers included in the work: norbornene-derived Chlorambucil (Monomer 1), norbornene grafted with polyethylene glycol, and folic acid (Monomer 2) and norbornene attached methyl orange (Monomer 3) connected to the norbornene backbone through ester linkage were clearly discussed. Finally, the random copolymer CHO PEG FOL METH was synthesized by ring-opening metathesis polymerization (ROMP) using Grubbs' second-generation catalyst. Advanced polymer chromatography (APC) was used to find the final polymer's molecular weight and polydispersity index (PDI). Dynamic light scattering, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were utilized to explore the prodrug's size and morphology. Release experiments of the anticancer drug, Chlorambucil and the coloring agent, methyl orange, were performed at different pH and time. Cell viability assay was carried out for determining the rate of survived cells, followed by the treatment of our final polymer named CHO PEG FOL METH.

Recent Progress and Advances in Stimuli-Responsive Polymers for Cancer Therapy

The conventional chemotherapeutic agents, used for cancer chemotherapy, have major limitations including non-specificity, ubiquitous biodistribution, low concentration in tumor tissue, and systemic toxicity. In recent years, owing to their unique features, polymeric nanoparticles have been widely used for the target-specific delivery of drugs in the body. Although polymeric nanoparticles have addressed a number of important issues, the bioavailability of drugs at the disease site, and especially upon cellular internalization, remains a challenge. A polymer nanocarrier system with a stimuli-responsive property (e.g., pH, temperature, or redox potential), for example, would be amenable to address the intracellular delivery barriers by taking advantage of pH, temperature, or redox potentials. With a greater understanding of the difference between normal and pathological tissues, there is a highly promising role of stimuli-responsive nanocarriers for drug delivery in the future. In this review, we highlighted the recent advances in different types of stimuli-responsive polymers for drug delivery.

Engineering Camptothecin-Derived Norbornene Polymers for Theranostic Application

A multifunctional stimuli-responsive nanotheranostic agent provides huge benefits in nanomedicine by combining both the diagnostic agent and the drug molecule in a single system. This nanosystem is capable of doing multiple tasks, for example, diagnosis, drug delivery, and monitoring the therapeutic response. Hence, theranostic agents are expected to play a significant role in personalized medicine. Herein, a new class of nanotheranostic agents, Pnr-Cbt-Cpt-Pg-Bn, is proposed for the effective delivery of camptothecin. This new class of polymer has been functionalized with a superparamagnetic norbornene cobalt unit for its use in magnetic resonance imaging (MRI). The NMR one-dimensional image confirms the MRI capability of this nanotheranostic agent. This is further modified with the poly(ethylene glycol)-biotin moiety for biocompatibility and site-specificity. The uniqueness of the design is confirmed by an in vitro study where a greater uptake of the nanotheranostic agent is observed when compared with free drugs. Hence, this new class of copolymer shows improved potential as nanotheranostic agents in drug delivery.

Multiple cross-linked hydroxypropylcellulose–succinate–salicylate: prodrug design, characterization, stimuli responsive swelling–deswelling and sustained drug release

Multiple cross-linked hydroxypropylcellulose–succinate–salicylate.