Micellar solubilization of tributylphosphate in aqueous solutions of Pluronic block copolymers

HRMAS-NMR and simulation study of the self-assembly of surfactants on carbon nanotubes

Polyethoxylated surfactants, such as those of the Tween and Pluronic series, are commonly used to disperse carbon nanotubes (CNTs) and other nanoparticles. However, the current understanding of the nature of interactions between these surfactants and CNTs is limited. The nature of the interactions between surfactants (Tween-80 [T80] and Pluronic F68 [PF68]) and CNTs was investigated using high-resolution magic angle spinning nuclear magnetic resonance (HRMAS-NMR) and coarse-grained molecular dynamics (MD) simulations. HRMAS-NMR revealed that T80 molecules interact with single-walled CNTs (SWCNTs) and multi-walled CNTs (MWCNTs) via the oleyl chain, whereas PF68 molecules interact with the surface of SWCNTs and MWCNTs via the polypropylene oxide residues. The polyethylene oxide chains were oriented towards the external aqueous environment. The HRMAS-NMR results were supported by MD simulations, and the latter provided further insights into the nature of the interactions.

Tri-block co-polymer nanocarriers for enhancement of oral delivery of felodipine: preparation, in vitro characterization and ex vivo permeation

This study aimed to prepare, optimize and characterize novel felodipine-loaded polymeric nanomicelles, using a pluronic mixture of F127 and P123. Thin-film hydration method was adopted for the preparation of different polymeric nanomicelles (T1-T12) according to a 4¹.3¹ full factorial design. Factors studied were: Pluronic®:drug ratio (P:D ratio) (10, 20, 30 and 40 w/w) and percent of hydrophilic polymer (F127%) (33.33%, 50% and 66.67% w/w). Optimization criteria were to maximize transmittance percent (T%) and entrapment efficiency percent (EE%) and to minimize particle size (PS) and polydispersity index (PDI). The optimized formulation was further characterized by DSC, FTIR and ¹H NMR studies. It was also subjected to stability testing and ex vivo permeation using rabbit intestines. Spherical nanomicelles of particle size ranging from 26.18 to 87.54 nm were successfully obtained. The optimized formulation was found to be the already prepared formulation T12 (P:D ratio of 40 and 66.67% F127) with suitable T% and EE% of 95.12% and 91.75%, respectively. DSC, FTIR and ¹H NMR studies revealed felodipine (FLD) incorporation within T12 nanomicelles. T12 enhanced the ex vivo intestinal permeation of FLD when compared to a drug suspension and showed good stability. Therefore, pluronic nanomicelles could be promising for improved oral delivery of FLD.

Development and optimization of self-assembling nanosystem for intra-articular delivery of indomethacin

Osteoarthritis is a propagated debilitating condition affecting patients' quality of life. Intra-articular injection approach was investigated as a localized treatment strategy providing: site-specific delivery, decreased side effects and, increased patient compliance. A 3² full factorial experimental design was employed to prepare the indomethacin-loaded self-assembling nanosystems (SANS). The surfactant (Poloxamer 407/Tetronic 90R4) ratio and the poly(lactic-co-glycolic acid) (PLGA) concentration significantly affected encapsulation efficiency and drug release (p<0.05). The optimized formula was subjected to modification by addition of different proteoglycans, as a compensatory treatment, to improve its pharmacological properties. The modified SANS, containing glucosamine (150mg), was selected for in-vivo studies as it had a sustained drug release profile and a small particle size (173.90nm). The effect of the optimized SANS, with or without PLGA, was compared with the modified formula containing glucosamine and, with the drug suspension on the arthritic knee joints of rats. It was found that the formulation containing PLGA and glucosamine showed significantly higher reduction in both, knee diameter and TNF-α levels, compared to other groups. Furthermore, all SANS showed histological improvement in the cellularity of the synovial membranes and joints. Our results indicate that SANS containing PLGA and glucosamine is capable of treating arthritic joints.

Tri/tetra-block co-polymeric nanocarriers as a potential ocular delivery system of lornoxicam: in-vitro characterization, and in-vivo estimation of corneal permeation

Polymeric micelles that can deliver drug to intended sites of the eye have attracted much scientific attention recently. The aim of this study was to evaluate the aqueous-based formulation of drug-loaded polymeric micelles that hold significant promise for ophthalmic drug delivery. This study investigated the synergistic performance of mixed polymeric micelles made of linear and branched poly(ethylene oxide)-poly(propylene oxide) for the more effective encapsulation of lornoxicam (LX) as a hydrophobic model drug. The co-micellization process of 10% binary systems combining different weight ratios of the highly hydrophilic poloxamers; Synperonic(®) PE/P84, and Synperonic(®) PE/F127 and the hydrophobic poloxamine counterpart (Tetronic(®) T701) was investigated by means of photon correlation spectroscopy and cloud point. The drug-loaded micelles were tested for their solubilizing capacity towards LX. Results showed a sharp solubility increase from 0.0318 mg/mL up to more than 2.34 mg/mL, representing about 73-fold increase. Optimized formulation was selected to achieve maximum drug solubilizing power and clarity with lowest possible particle size, and was characterized by (1)HNMR analysis which revealed complete encapsulation of the drug within the micelles. Further investigations by histopathological and confocal laser studies revealed the non-irritant nature and good corneal penetrating power of the proposed nano-formulation.

TBP induced double cloud point in aqueous EO13PO30EO13 solutions: investigating the evolution of associated micellar characteristics as a function of temperature

TBP solubilized Pluronic L64 solutions exhibit inter-micellar attraction driven micellar cluster formation upon cooling, which is unique in non-ionic micellar systems.

Brain targeting of olanzapine via intranasal delivery of core-shell difunctional block copolymer mixed nanomicellar carriers: in vitro characterization, ex vivo estimation of nasal toxicity and in vivo biodistribution studies

Olanzapine (OZ) is atypical antipsychotic drug that suffers from low brain permeability due to efflux by P-glycoproteins and hepatic first-pass metabolism. The current work aimed to develop OZ-loaded micellar nanocarriers and investigate their nose-to-brain targeting potential. OZ-loaded (5mg/ml) micelles (F1-F12) were prepared, using a Pluronic(®) mixture of L121 and P123, adopting thin-film hydration method. The micelles were evaluated for turbidity, particle size, morphology, drug-entrapment efficiency (EE%), drug-loading characteristics, in vitro drug release and ex vivo nasal toxicity in sheep. The in vivo biodistribution and pharmacokinetic studies in the brain/blood following intravenous (i.v.) and intranasal (i.n.) administrations of technetium-labeled OZ-loaded micelles and OZ-solution were evaluated in rats. Spherical micelles ranging in size from 18.97 to 380.70 nm were successfully developed. (1)H NMR studies confirmed OZ incorporation into micelle core. At a drug:Pluronic(®) L121:Pluronic(®) P123 ratio of 1:8:32 (F11), the micelles achieved a conciliation between kinetic and thermodynamic stability, high drug-EE%, controlled drug-release characteristics and evoked minor histopathological changes in sheep nasal mucosa. The significantly (P<0.05) higher values for F11 micelles (i.n.); brain/blood ratio (0.92), drug targeting index (5.20), drug targeting efficiency (520.26%) and direct transport percentage (80.76%) confirm the development of a promising non-invasive OZ-loaded nose-to-brain delivery system.

Small-angle neutron scattering study of solubilization of tributyl phosphate in aqueous solutions of L64 Pluronic triblock copolymers

We have studied the solubilization behavior of tributylphosphate (TBP) in aqueous solutions of L64-Pluronics, using light and small angle neutron scattering (SANS). Varying the temperature and the oil content, the system presents a nontrivial phase behavior. In particular, at 308 K, a first solubilization followed by an emulsification failure and a resolubilization is found. We have measured the microstructure by SANS and characterized the microemulsion droplet core size, corona thickness, polydispersity, and interactions. It is shown that at low oil content, the system is made of small swollen micelles. After the phase separation, the resolubilization is carried by larger oil droplets decorated by copolymer. From specific surface measurements at large angles, a surprising change in surfactant conformation is found to accompany this morphological evolution which is also supported by previous results obtained from ¹H NMR experiments. In independent measurements, our structural modeling is confirmed using contrast-variation SANS.