Rakesh K. Tekade

Nanocarrier mediated delivery of siRNA/miRNA in combination with chemotherapeutic agents for cancer therapy: Current progress and advances

Chemotherapeutic agents have certain limitations when it comes to treating cancer, the most important being severe side effects along with multidrug resistance developed against them. Tumor cells exhibit drug resistance due to activation of various cellular level processes viz. activation of drug efflux pumps, anti-apoptotic defense mechanisms, etc. Currently, RNA interference (RNAi) based therapeutic approaches are under vibrant scrutinization to seek cancer cure. Especially small interfering RNA (siRNA) and micro RNA (miRNA), are able to knock down the carcinogenic genes by targeting the mRNA expression, which underlies the uniqueness of this therapeutic approach. Recent research focus in the regime of cancer therapy involves the engagement of targeted delivery of siRNA/miRNA in combinations with other therapeutic agents (such as gene, DNA or chemotherapeutic drug) for targeting permeability glycoprotein (P-gp), multidrug resistant protein 1 (MRP-1), B-cell lymphoma (BCL-2) and other targets that are mainly responsible for resistance in cancer therapy. RNAi-chemotherapeutic drug combinations have also been found to be effective against different molecular targets as well and can increase the sensitization of cancer cells to therapy several folds. However, due to stability issues associated with siRNA/miRNA suitable protective carrier is needed and nanotechnology based approaches have been widely explored to overcome these drawbacks. Furthermore, it has been univocally advocated that the co-delivery of siRNA/miRNA with other chemodrugs significantly enhances their capability to overcome cancer resistance compared to naked counterparts. The objective of this article is to review recent nanocarrier based approaches adopted for the delivery of siRNA/miRNA combinations with other anticancer agents (siRNA/miRNA/pDNA/chemodrugs) to treat cancer.

PULMONARY TOXICITY OF CARBON NANOTUBES: A SYSTEMATIC REPORT

UNLABELLED Carbon nanotubes (CNTs) are nanosized cylindrical hollow tubes consisting entirely of the element carbon. Currently, CNTs are playing an important role in drug delivery as a carrier system because of their several unique physical and chemical properties. Studies show that CNTs are toxic and that the extent of that toxicity depends on properties of the CNTs, such as their structure (single wall or multiple wall), length and aspects ratios, surface area, degree of aggregation, extent of oxidation, bound functional group(s), method of manufacturing, concentration, and dose. People could be exposed to CNTs either accidentally by coming in contact with the aerosol form of CNTs during production or by exposure as a result of biomedical use. Numerous in vitro and in vivo studies have shown that CNTs and/or associated contaminants or catalytic materials that arise during the production process may induce oxidative stress, prominent pulmonary inflammation, apoptosis in different cell types, and induction of cytotoxic effects on lungs. Studies on the toxicity of CNTs have mainly focused on the pulmonary effects of intratracheal or pharyngeally administered CNTs. This review examines the potential pulmonary toxicity of CNTs. FROM THE CLINICAL EDITOR Carbon nanotubes are promising drug delivery agents; however, their pulmonary toxicity may represent a substantial limitation to their applicability. This detailed review discusses critical aspects of the above problem.

Dendrimers as therapeutic agents: a systematic review

Objectives Dendrimers by virtue of their therapeutic value have recently generated enormous interest among biomedical scientists. This review describes the therapeutic prospects of the dendrimer system.

Exploring dendrimer towards dual drug delivery: pH responsive simultaneous drug-release kinetics.

A major problem associated with conventional leukaemia chemotherapy is the development of resistance that can be surmounted well by combination chemotherapy. The objective of the present investigation is to report a novel technology to load two anti-leukaemic drugs of choice simultaneously inside the PAMAM dendrimer. Under optimized conditions of pH and dialysis time, one molecule of PAMAM dendrimer was found to be capable of entrapping 27.02 ± 0.51 and 8.00 ± 0.46 molecules of Methotrexate and all-trans Retinoic acid (ATRA), respectively. The simultaneous in-vitro release profiling of the loaded drugs was studied at pH 4, 7.4 and 10. The release kinetics was found to be governed by degree of dendrimer protonation, with more sustained and controlled behaviour at pH 7.4. Terminal loading of dendrimer with less haemolytic bioactive (ATRA) reduced the haemolytic toxicity of the dendrimer formulation. A cytotoxicity study was performed on HeLa cell lines by MTT assay, wherein after 72 h, the dual-drug loaded dendrimer was found to be more efficient (IC50 0.5 µM) as compared to that of the free drug combination (IC50 0.75 µM).

Pharmaceutical and Biomedical Potential of PEGylated Dendrimers

The development of dendritic architecture with well-defined size, shape and controlled exterior functionality holds promise in pharmaceutical applications such as drug delivery, solubilization, DNA transfection and diagnosis. Highly branched, monodisperse, stable molecular level and low polydispersity with micelle-like behavior possessing nano-scale container property distinguish these structures as inimitable and optimum carrier for those applications. However reticuloendothelial system (RES) uptake, drug leakage, immunogenicity, hemolytic toxicity, cytotoxicity, hydrophobicity restrict the use of these nanostructures. PEGylation of dendrimers can generally overcome these shortcomings. Hemolytic and different cell line studies have shown reduced toxicity of PEGylated dendrimers than cationic dendrimers. PEGylation causes increased solubilization of hydrophobic drugs in dendritic framework as well as in PEG layers. PEGylated dendrimers have proved capable of forming stable complex with plasmid DNA and achieved improved gene transfection as compared to non-PEGylated dendrimers. Attachments of targeting moiety on the surface of partially PEGylated dendrimer created much interest as a delivery system for crossing of biological barriers and deliver the bioactive agent near the vicinity of target site. Recent successes also demonstrate potential of PEGylated dendrimers as magnetic resonance imaging contrast agent and in carbonyl metallo immunoassay. This review focuses on the current state of the art in the field and focuses on the potential of PEGylated dendrimers in pharmaceutical and biomedical area.

Cancer targeting potential of some ligand-anchored poly(propylene imine) dendrimers: a comparison

UNLABELLED The present investigation was aimed at developing and comparing the cancer-targeting potential of ligand-anchored dendrimers. Folate-, dextran-, and galactose-anchored poly(propylene imine) dendrimers were synthesized and characterized. Dendritic formulations were evaluated for ex vivo cytotoxicity on HeLa and SiHa cell lines. Flow cytometry studies were performed on the HeLa cell line. An ex vivo MTT assay on HeLa cells indicated IC(50) values of 0.05, 0.2, 0.8, and 0.08 μM for folate, dextran, and galactose formulations, and for free paclitaxel (PTX), respectively. An analogous observation was carried out in SiHa cells, where IC(50) values of 0.6, 0.8, 10, and 6 μM were observed by folate, dextran, and galactose formulations, and free PTX, respectively. The outcome of the MTT assay and flow cytometry suggested the order of targeting potential of various ligands under investigation as folate > dextran > galactose. The outcome is deemed to be of scientific value and is believed to assist drug delivery scientists during selection of targeting ligands. FROM THE CLINICAL EDITOR The cancer targeting potential of folate, dextran and galactose functionalized polypropyleneimine (PPI) dendrimers was studied by this group of investigators, reporting the order of targeting potential as folate > dextran > galactose.

Micro- and nanocarrier-mediated lung targeting.

Importance of the field: Drug delivery to lungs appears to be an attractive proposition on account of the large surface area of the alveolar region; it provides tremendous opportunities to improve drug therapies both systemically and locally using new drug delivery systems. Administration of drugs directly to the lungs is the most appropriate route in the treatment of asthma and other pulmonary diseases such as tuberculosis, chronic obstructive pulmonary disease and lung cancer. Areas covered in this review: This review focuses on the utilization of nano- and microcarriers such as microspheres, nanoparticles, liposomes, niosomes and dendrimers for targeted delivery of bioactive molecules to lungs. What the reader will gain: This review sheds light on the current status of nano- and microcarrier-mediated lung targeting of bioactive compounds. Take home message: The literature review shows that carriers could supplement sustained drug delivery to the lungs, extended duration of action, reduced therapeutic dose, improved patient compliance, and reduced adverse effects of highly toxic drugs. There is still a need to identify more specific receptors that are present exclusively in the lungs. The identification of such receptors may also facilitate drug targeting to further specific parts of the lungs, such as bronchioles and alveoli.

PEGylated PPI dendritic architectures for sustained delivery of H2 receptor antagonist

The present study was aimed at synthesizing and exploring the use of long circulating biocompatible PEGylated PPI 5.0G dendrimers for sustained delivery of a H(2) receptor antagonist, Famotidine. PPI 5.0G dendrimers were synthesized and PEGylated using dicarboxylic acid PEG 2000. PEGylation was confirmed by SEC, IR, NMR and MASS spectroscopies. Famotidine was loaded in PEGylated dendritic system and confirmed by IR and differential scanning calorimetry. The PEGylated dendritic system has shown an increased drug loading capacity, a reduced hemolytic toxicity and demonstrated a suitability of PEGylated PPI 5.0G dendrimer for prolonged delivery of Famotidine during in vitro release, in vivo blood level and tissue distribution studies in albino rats. The ulcer index after 5h of treatment with different formulations was found to be 4.5+/-0.28 in case of plain Famotidine solution, while ulcer index was significantly reduced to 0.5+/-0.13 in case of Famotidine loaded PEGylated PPI 5.0G dendrimers, indicating sustained release of the drug from drug-PEGylated dendrimer complex. The results suggested that such PEGylated dendrimeric systems could serve as nanoparticulate depot for drugs in body.

Surface-engineered dendrimers for dual drug delivery: A receptor up-regulation and enhanced cancer targeting strategy

The present study is aimed at developing and evaluating a combined strategy of dual drug delivery, receptor up-regulation, and drug targeting. The dendritic architectures were synthesized and characterized by IR, 1H-NMR, and 13C-NMR spectroscopy. The pH-responsive simultaneous release behavior of the loaded bioactive from the carrier was also explored. The cell line studies for MTT cytotoxicity, receptor blockade, and receptor up-regulation assays were performed on HeLa cells. Treatment of cells with low concentration of all-trans retinoic acid (ATRA, ∼1 μM) caused a selective up-regulation of folate receptors by 2.21-folds when compared with that of untreated control, after 48 h. ATRA showed a lag phase of 12 h in up-regulating the folate receptors. After 48 h, the IC50 value of naked methotrexate (MTX)–ATRA combination and dendrimer-loaded MTX–ATRA combination were found to be ∼0.1 and 10 μM, respectively, while folate-anchored dendrimer loaded with MTX–ATRA showed a selectively lowered IC50 value of 0.04 μM. It was concluded that in allied ailments like cancer, the proposed dual-drug delivery modality bearing anti-cancer bioactive in conjunction with folate receptor up-regulating cargo may prove to be a promising approach toward the development of a flourishing cancer therapy.

Dendimer-Mediated Solubilization, Formulation Development and in Vitro−in Vivo Assessment of Piroxicam

The present investigation was aimed at exploring dendrimer-mediated solubilization and formulation development followed by in vitro, in vivo assessment of piroxicam (PXM) nanocomposite. For this, two dendrimer generations (3.0G and 4.0G) were synthesized and characterized by IR, (1)H NMR spectroscopic and electron microscopy techniques. The optimized formulations containing 0.2% w/v of PXM loaded PAMAM dendrimer at pH 7.4 referred to as 0.2-D(3)P(7.4) (3.0G) and 0.2-D(4)P(7.4) (4.0G) resulted in significant enhancements of PXM solubility approximately by 107- and 222-fold, respectively. The in vitro release behavior of PXM from the formulation in medium-I (PBS 7.4) and medium-II (PBS with 1% albumin) and stability studies were also favorable. Pharmacokinetic study showed higher area under curve (AUC(0-->t); microg/mL/h) of 293.78 +/- 2.04 and 321.54 +/- 2.37 with optimized 0.2-D(3)P(7.4) and 0.2-D(4)P(7.4) formulations, respectively, as opposed to 279.11 +/- 1.48 with plain PXM. The elimination half-life of the drug encapsulated in the formulation was significantly higher (0.2-D(3)P(7.4), 36.6 and 0.2-D(4)P(7.4), 41.1; h) than that of pure drug (33.7 h; p < 0.005), and the overall elimination rate constant of formulations was also less as compared to free drug (p < 0.005). Pharmacodynamic assessment by rat-paw model of 0.2-D(3)P(7.4) and 0.2-D(4)P(7.4) formulations displayed inhibition levels of 54.21 +/- 1.25% and 59.33 +/- 0.63%, respectively, which are higher than those of plain PXM (41.81 +/- 2.9) formulations, after the sixth hour of administration. The second, fourth and eighth hour organ distribution data showed significantly higher recovery of PXM in rat paw with dendrimer-based formulations in comparison to plain PXM. However, comparison of overall data suggested 4.0G-based formulations to be superior to 3.0G as well as pure PXM.