Marcela A. Moretton

New old challenges in tuberculosis: potentially effective nanotechnologies in drug delivery.

Tuberculosis (TB) is the second most deadly infectious disease. Despite potentially curative pharmacotherapies being available for over 50 years, the length of the treatment and the pill burden can hamper patient lifestyle. Thus, low compliance and adherence to administration schedules remain the main reasons for therapeutic failure and contribute to the development of multi-drug-resistant (MDR) strains. Pediatric patients constitute a high risk population. Most of the first-line drugs are not commercially available in pediatric form. The design of novel antibiotics attempts to overcome drug resistance, to shorten the treatment course and to reduce drug interactions with antiretroviral therapies. On the other hand, the existing anti-TB drugs are still effective. Overcoming technological drawbacks of these therapeutic agents as well as improving the effectiveness of the drug by targeting the infection reservoirs remains the central aims of Pharmaceutical Technology. In this framework, nanotechnologies appear as one of the most promising approaches for the development of more effective and compliant medicines. The present review thoroughly overviews the state-of-the-art in the development of nano-based drug delivery systems for encapsulation and release of anti-TB drugs and discusses the challenges that are faced in the development of a more effective, compliant and also affordable TB pharmacotherapy.

Molecular implications in the nanoencapsulation of the anti-tuberculosis drug rifampicin within flower-like polymeric micelles

Tuberculosis (TB) is the second most deadly infectious disease behind the Human Immunodeficiency Virus (HIV). An effective pharmacotherapy has been available for more than 5 decades. However, the length of the treatment and the pill burden result in low patient compliance and adherence to the regimens. Nanotechnologies can overcome these basic technological drawbacks. The present work explored the molecular implications governing the encapsulation and water solubilization of RIF within flower-like micelles of poly(epsilon-caprolactone)-b-poly(ethylene glycol)-poly(epsilon-caprolactone) (PCL-PEG-PCL) block copolymers. Ten derivatives of different molecular weight and hydrophobic/hydrophilic caprolactone/ethylene oxide ratio (CL/EO) were synthesized by a fast and high-yield Microwave-Assisted Polymer Synthesis (MAPS) technique; CL/EO values are determined by taking the ratios of the number of repeating units in the PCL and the PEG segments. The aggregation behavior of the copolymers was thoroughly investigated by means of surface tension (critical micellar concentration), dynamic light scattering (size, size distribution and zeta potential) and transmission electron microscopy (morphology). In general, the greater the central PEG segment, the larger the micelles formed. The physical stability was intimately associated with the molecular weight and the composition. Then, the encapsulation of RIF in the different copolymer families was evaluated, and the physical stability of the drug-loaded aggregates characterized. The micellar size appears as the most crucial property, this phenomenon being primarily controlled by the molecular weight of the PEG central block. Having expressed this, sufficiently high CL/EO ratios (and long PCL segments) are also demanded to attain stable micellar systems with cores that are large enough to host the bulky RIF molecule.

Polymeric mixed micelles as nanomedicines: Achievements and perspectives

During the past few decades, polymeric micelles have raised special attention as novel nano-sized drug delivery systems for optimizing the treatment and diagnosis of numerous diseases. These nanocarriers exhibit several in vitro and in vivo advantages as well as increased stability and solubility to hydrophobic drugs. An interesting approach for optimizing these properties and overcoming some of their disadvantages is the combination of two or more polymers in order to assemble polymeric mixed micelles. This review article gives an overview on the current state of the art of several mixed micellar formulations as nanocarriers for drugs and imaging probes, evaluating their ongoing status (preclinical or clinical stage), with special emphasis on type of copolymers, physicochemical properties, in vivo progress achieved so far and toxicity profiles. Besides, the present article presents relevant research outcomes about polymeric mixed micelles as better drug delivery systems, when compared to polymeric pristine micelles. The reported data clearly illustrates the promise of these nanovehicles reaching clinical stages in the near future.

Novel Soluplus®—TPGS mixed micelles for encapsulation of paclitaxel with enhanced in vitro cytotoxicity on breast and ovarian cancer cell lines

The aim of this work was to develop mixed micelles based on two biocompatible copolymers of polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol (Soluplus(®)) and D-α-tocopheryl polyethylene-glycol 1000 succinate (TPGS), to improve the aqueous solubility and the in vitro anti-tumor activity of paclitaxel (PTX). Pure and mixed nanomicelles were prepared by solvent evaporation method and characterized by transmission electron microscopy (TEM) and dynamic light scattering (DLS). Solubility of PTX was increased 60,000 and 38,000 times, when it was formulated in pure Soluplus(®) micelles and in mixed micelles (Soluplus(®):TPGS; 4:1 ratio), respectively. The in vitro PTX release profile from micellar systems was characterized employing the dialysis membrane method where all drug-loaded formulations showed a sustained and slow release of PTX. In vitro assays were conducted on human cancer cell lines including ovarian cancer cells SKOV-3, breast cancer cells MCF-7 and triple negative breast cancer cells MDA-MB-231. Cytotoxicity studies showed that mixed micelles exhibited better antitumor activity compared to PTX solution against the three cell lines. Furthermore mixed micelles showed a significant increase on PTX cellular uptake in comparison with pure Soluplus(®) micelles and free drug in all cell lines assayed. More important, blank mixed micelles have shown cytotoxic activity due to the ability of TPGS to induce apoptosis in cancer cells. This effect was associated with the expression levels of cleaved-PARP, an apoptosis-related protein. On the basis of these results, the mixed micelles developed in this study might be a potential nano-drug delivery system for cancer chemotherapy.

Doxorubicin: nanotechnological overviews from bench to bedside

Doxorubicin (DOX) is considered one of the most effective chemotherapeutic agents, used as a first-line drug in numerous types of cancer. Nevertheless, it exhibits serious adverse effects, such as lethal cardiotoxicity and dose-limiting myelosuppression. In this review, we focus on the description and the clinical benefits of different DOX-loaded nanotechnological platforms, not only those commercially available but also the ones that are currently in clinical phases, such as liposomes, polymeric nanoparticles, polymer-drug conjugates, polymeric micelles and ligand-based DOX-loaded nanoformulations. Although some DOX-based nanoproducts are currently being used in the clinical field, it is clear that further research is necessary to achieve improvements in cancer therapeutics.

Cryoprotection-lyophilization and physical stabilization of rifampicin-loaded flower-like polymeric micelles.

Rifampicin-loaded poly(ε-caprolactone)–b-poly(ethylene glycol)–poly(ε-caprolactone) flower-like polymeric micelles display low aqueous physical stability over time and undergo substantial secondary aggregation. To improve their physical stability, the lyoprotection–lyophilization process was thoroughly characterized. The preliminary cryoprotectant performance of mono- and disaccharides (e.g. maltose, glucose), hydroxypropyl-β-cyclodextrin (HPβCD) and poly(ethylene glycol) (PEG) of different molecular weights was assessed in freeze–thawing assays at −20°C, −80°C and −196°C. The size and size distribution of the micelles at the different stages were measured by dynamic light scattering (DLS). A cryoprotectant factor (fc) was determined by taking the ratio between the size immediately after the addition of the cryoprotectant and the size after the preliminary freeze–thawing assay. The benefit of a synergistic cryoprotection by means of saccharide/PEG mixtures was also assessed. Glucose (1 : 20), maltose (1 : 20), HPβCD (1 : 5) and glucose or maltose mixtures with PEG3350 (1 : 20) (copolymer:cryoprotectant weight ratio) were the most effective systems to protect 1 per cent micellar systems. Conversely, only HPβCD (1 : 5) cryoprotected more concentrated drug-loaded micelles (4% and 6%). Then, those micelle/cryoprotectant systems that displayed fc values smaller than 2 were freeze-dried. The morphology of freeze-dried powders was characterized by scanning electron microscopy and atomic force microscopy and the residual water content analysed by the Karl Fisher method. The HPβCD-added lyophilisates were brittle porous cakes (residual water was between 0.8% and 3%), easily redispersable in water to form transparent systems with a minimal increase in the micellar size, as determined by DLS.

Paclitaxel: What has been done and the challenges remain ahead

In recent years, the nanotechnology has offered researchers the opportunity to solve the problems caused by the vehicle of the standard and first formulation of paclitaxel (Taxol®), while maximizing the proven antineoplastic activity of the drug against many solid tumors. Hence, different types of nanocarriers have been employed to improve the efficacy, safety, physicochemical properties and pharmacokinetic/pharmacodynamic profile of this drug. To date, paclitaxel is the unique drug that is marketed in three different nanoplatforms for its parenteral delivery: polymeric nanoparticles (Abraxane®), liposomes (Lipusu®), and polymeric micelles (Genexol®, Nanoxel® and Paclical®). Indeed, a fourth nanocarrier might be available soon, because phase III studies of Opaxio™, a polymeric-conjugated, are near completion. Furthermore, other several nanoformulations are currently in various stages of clinical trials. Therefore, it is only through the critical analysis of clinical evidence from these studies that we can get a more concrete idea of what has been achieved with pharmaceutical nanotechnology so far. This review attempts to summarize current information available regarding the clinical status and the physicochemical characteristic of different nanocarriers for paclitaxel delivery in cancer therapy. We present an overview of the preclinical and clinical data of these systems including their pharmacokinetics, dose and administration, adverse events and clinical efficacy.

Novel nelfinavir mesylate loaded d-α-tocopheryl polyethylene glycol 1000 succinate micelles for enhanced pediatric anti HIV therapy: In vitro characterization and in vivo evaluation

Worldwide more than 35 million people are living with Human Immunodeficiency Virus (HIV) where 3.3 million are children. This translates in approximately 700 new daily infections in children only in 2012. Prolonged High Activity Antiretroviral Therapy (HAART) regimes could present low-patient compliance, especially in children, affecting therapeutic success. Nelfinavir mesylate (NFV) is a non-peptidic HIV-1 protease inhibitor (IP) which was the first IP recommended for pediatric use (>2 years-old). It exhibits pH-dependant aqueous solubility which results highly restricted at physiological pH values. The former represents a main clinical limitation due to the reduction on drug absorption along the small intestine after an oral administration, leading to unpredictable drug bioavailability. Moreover a liquid formulation of NFV is not available worldwide, preventing appropriate dose adjustment and more convenient administration. In this framework, the present investigation reports the development of a NFV highly concentrated aqueous formulation for a more appropriate management of pediatric anti-HIV therapy. The aim was to encapsulate NFV within D-α-tocopheryl polyethylene glycol 1000 succinate micelles to improve its aqueous solubility and its oral pharmacokinetic parameters. Results show that NFV aqueous solubility was increased up to 80.3 mg/mL. NFV-loaded micelles exhibited a hydrodynamic diameter of 5.6 nm and a spherical morphology as determined by dynamic light scattering and transmission electronic microscopy, respectively. In vitro NFV release profile demonstrated a cumulative drug release of 56% at 6 h. Finally, in vivo data showed a significant (p<0.01) increase of Area-Under-the-Curve between 0 and 24 h for NFV encapsulated in micelles in comparison with a NFV suspension prepared with glycerin 20% v/v and carboxymethylcellulose sodium 0.5% w/v, representing an increment on drug oral relative bioavailability of 1.71-fold. Thereby, this formulation represents an innovative nanotechnological platform to improve pediatric HIV pharmacotherapy.

Enhanced oral bioavailability of nevirapine within micellar nanocarriers compared with Viramune(

In this work, Nevirapine (NVP) was encapsulated within three derivatives of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) block copolymers (Tetronic(®) 904, 1107 and Pluronic(®) F127) with and without the addition of three pharmaceutical cosolvents (glycerin, propylene glycol and polyethylene glycol 400) over a wider range of concentrations (0-40% v/v). Also, we evaluated the effect of addition of the cosolvents on the micellar size as determined by dynamic light scattering (DLS) measurements and transmission electron microscopy (TEM). The solubilization capacity of the systems was investigated by UV-spectrophotometry (282nm) and the systems stability was evaluated for 1 month at 25°C. Finally, oral bioavailability of the NVP-loaded micellar systems (2mg/mL) was assessed in male Wistar rats (8mg/kg) and compared with a pediatric commercially available formulation (Viramune(®)). The present study demonstrates that PEO-PPO-PEO polymeric micelles were able to enhance apparent aqueous solubility of NVP with the addition of cosolvents. Moreover, micellar nanocarriers significantly (p<0.05) improved the oral bioavailability of the drug versus Viramune(®). Overall results support the suitability of the strategy toward the development of an optimized NVP aqueous formulation to prevent HIV/AIDS mother-to-child transmission.

Novel carvedilol paediatric nanomicelle formulation: in-vitro characterization and in-vivo evaluation.

Carvedilol (CAR) is a poorly water‐soluble beta‐blocker. Its encapsulation within nanomicelles (NMs) could improve drug solubility and its oral bioavailability, allowing the development of a paediatric liquid CAR formulation with commercially available copolymers: D‐α‐tocopheryl polyethylene glycol 1000 succinate (TPGS) and poly(vinyl caprolactam)‐poly(vinyl acetate)‐poly(ethylene glycol) (Soluplus®).