Pharmaceutical Nanotechnology (v.4, #2)

Meet Our Editorial Board Member by Kamla Pathak (85-85).

EDITORIAL by Ijeoma Uchegbu (86-87).

Injectable Liposomal Formulations: Systematic Analysis for Regulatory Purposes by Marcela Castro, Frédéric Frézard (88-108).
Background: Among the drug delivery systems, liposomes stand out for their biocompatible and biodegradable characteristics and high versatility. There are many marketed liposomal drug products, most of them injectables. From a regulatory perspective, some documents were published by FDA and EMA, but a systematic analysis of the factors influencing efficacy, toxicity and stability of injectable liposomal drug products has not yet been carried out in order to identify regulatory relevant items.
Method: We use cause and effect diagrams (Ishikawa) to provide knowledge for regulatory action and to support the development of regulation or guidelines containing specific requirements for injectable liposomal drug products, especially with regard to their quality control and stability.
Result: It was possible to identify the critical quality attributes to the efficacy, safety and stability of injectable liposomal drug products, and some of the tests to be considered in their characterization, quality control and stability. Some important aspects of the main analytical methods used for particle size and electric surface charge determination were described. An analysis of some specific topics related to Good Manufacturing Practices of injectable liposomal drug products is presented.
Conclusion: The documents published by FDA and EMA do not include all the items that need to be assessed for injectable liposomal drug products quality, and do not address analytical methods for quality attributes evaluation. It is urgent to establish regulatory requirements covering these products.

Polymeric Micelles for the Delivery of Diclofenac and Its Ethyl Ester Derivative by Hanan Al-Lawati, Mohammad R. Vakili, Fakhreddin Jamali, Afsaneh Lavasanifar (109-119).
Purpose: This study aimed to develop a polymeric micellar formulation of diclofenac, an NSAID with known cardiovascular (CV) toxicity.
Methods: Diclofenac (DFN) and diclofenac ethyl ester (DFEE) were encapsulated in polymeric micelles prepared from several block copolymers based on methoxy poly(ethylene oxide)-poly(ester)s (PEO-poly(ester)s). Prepared micelles were characterized for their particle size, polydispersity, encapsulation efficiency, drug loading content, and in vitro drug release. The kinetics of enzymatic hydrolysis for DFEE micelles versus free DFEE was then examined at 37±0.5°C in rat plasma.
Results: The DFN and DFEE loaded polymeric micelles exhibited particle size in the range of 27.9-50.3 nm. The slowest release for DFN micelles was achieved with micelles of PEO-block-poly(?-carboxyl-?- caprolactone) with a side chain of N,N-dimethyldipropylenetriamine which showed 71±3.2% drug release in 4 h followed by a sustained drug release reaching 100% within 24 h. The DFEE micelles showed slower release in comparison to DFN, and the optimal results were achieved with PEO-poly(?-caprolactone) micelles with percent release of 7.8±4.0% of DFEE in 4 h and 12.6±2.7% in 24 h. Incubation with plasma of polymeric micellar DFEE for 48 h revealed slow appearance of DFN as compared to that with the free DFEE and a good correlation with in vitro DFEE release data.
Conclusions: The results show a great potential for DFEE polymeric micelles in controlled delivery of diclofenac.

Evaluation of the Stability of Resveratrol Pluronic® Micelles Prepared by Solvent Casting and Simple Equilibrium Methods by Deepa A. Rao, Brianna Cote, Michelle Stammet, Adel M. Al Fatease, Adam W.G. Alani (120-125).
Background: Many different methods have been developed to incorporate hydrophobic compounds into polymeric micelles, including simple equilibrium (SE) and solvent casting (SC). Thus far, no studies have compared the SE and SC methods for drug loading and stability.
Methods: Resveratrol (RES), a model hydrophobic compound, loaded in various Pluronics® (F88, F98, F108, and F127) is used to determine the differences between SE and SC methods.
Results: Micelles prepared by SE method demonstrated RES loading in proportion to their respective CMC values with F127 having the lowest CMC and highest loading at Day 14 of 5.39±0.19 mg/mL, followed by F98 at 3.65±0.13 mg/mL, F108 at 3.29±0.06, and F88 at 2.35±0.05 mg/mL. Initial RES loading in SC method approaches 10 mg/mL in all the polymers, however, the micelles are unable to retain RES at this concentration for more than a few hours to a day. At the lower loading of 5 mg/mL a higher stability is seen in the Pluronic® micelles. In all micelles prepared by SC method, whether high or low loading, over a 14 day period the RES concentration in the micelles approached the equilibrium RES solubility.
Conclusion: Our results demonstrate that micelles prepared by SC result in meta-stable micelles when the amount of the compound loaded exceeds the equilibrium loading and the rate at which the compound in the micelles approaches equilibrium solubility is determined by the hydrophobicity of the compound and the hydrophile- lipophile balance (HLB) of the polymer.

Stable Indomethacin Dispersions in Water from Drug, Ethanol, Cationic Lipid and Carboxymethyl-Cellulose by Eliete G. Lima, Luciano R. Gomes, Ana M. Carmona-Ribeiro (126-135).
Background: The problem of formulating hydrophobic drugs in aqueous solutions is addressed from the point of view of nanotechnology. Nanoparticles (NPs) can incorporate high drug-to-carrier molar ratios with optimal drug dispersion and colloidal stabilization in water solution, especially when a biocompatible and hydrophilic polymer acts as an outer stabilizing layer. The hydrophobic drug indomethacin (IN) and the cationic lipid dioctadecyldimethylammonium bromide (DODAB) are soluble in ethanol (ET) and this property is useful to formulate the drug.
Objective: This work aims at optimal colloidal stability for aqueous IN dispersions employing IN/DODAB ethanolic solutions dispersed in water solutions of carboxy-methyl-cellulose (CMC).
Method: Photographs, dynamic light scattering for sizing, zeta-potential and polydispersity analysis are determined as a function of time for one week and scanning electron microscopy (SEM) for dried dispersions.
Results: Over a range of (CMC), NPs with good colloidal stability and absence of sedimentation were obtained both over a low or high (CMC) for (IN): (DODAB) around 1. Only around zero of zeta -potential there is precipitation with poor colloidal stabilization. The data point out a remarkable colloidal stability for IN/ET/DODAB/CMC NPs over a range of (CMC) (0.01-1 mg/mL). ET harmonizes lipid and drug imparting a good colloidal stability over the long run. The self-assembled NPs obtained in aqueous solution disassemble upon drying with appearance of fibers and aggregates reminiscent of NPs that occurred in water.
Conclusion: The co-solubilization /nanoprecipitation process is a powerful strategy to disperse hydrophobic drugs as nanoparticles in water solution of biocompatible hydrophilic polymers.

Microemulsion Based Hydrogel of Tacrolimus for the Treatment of Atopic Dermatitis by Geetanjali, Dilpreet Singh, Neena Bedi (136-154).
Objective: The aim of the present investigation was to develop microemulsionbased hydrogel of tacrolimus for topical application for the treatment of atopic dermatitis.
Methods: Microemulsion containing tacrolimus was developed by water titration method and was successfully incorporated into freshly prepared 1% carbopol 940 gels. Preformulation studies such as preparation of standard curve by HPLC, solubility studies and construction of phase diagrams were carried out. Lauroglycol was selected as oil, Labrasol and Tween 80 (1:1) as surfactant blend and Transcutol P as co-surfactant, on the basis of solubility of tacrolimus in the above constituents. The optimized microemulsion formulation and microemulsion based hydrogel were characterized for various parameters and were evaluated for the efficiency to treat atopic dermatitis induced by 2,4-dinitrochlorobenzene in BALB/c mice.
Results: The pH value and percent transmittance of microemulsion formulation were found to be 5.9 and 99.2%, respectively. Microemulsion did not show phase separation in centrifugation study. Transmission Electron Microscopy illustrated that the droplets of the microemulsion possessed spherical shape. The microemulsion based gel system possessed good spreadability and 83.31±1.148 % drug content. In vitro permeation studies showed that the permeation rate of both tacrolimus loaded microemulsions as well as microemulsion based hydrogel was observed to be higher than the drug solution and marketed ointment formulation. Histopathological analysis revealed that the microemulsion based hydrogel was more effective than the microemulsion and marketed ointment.
Conclusion: The results indicated that the formulated microemulsion based hydrogel is promising vehicle for topical delivery of tacrolimus for the treatment of atopic dermatitis.