Purification of Drug Loaded Liposomal Formulations by a Novel Stirred Cell Ultrafiltration Technique.

BACKGROUND: Presently reported methods for purification of liposomal formulations at laboratory scale have drawbacks of adversely affecting critical quality attributes (CQAs) of liposomes such as particle size, PDI, drug entrapment efficiency, etc., and are also not amenable for large scale processing. OBJECTIVE: The present study was aimed to explore stirred cell ultrafiltration technique as a novel liposome purification method for removal of unentrapped free drug and excess external aqueous fluid, maintaining the physical integrity of liposomes. METHODS: Purification of brimonidine loaded liposomes (model formulation) was performed by stirred cell ultrafiltration method, and its functional performance and impact on liposomal particle size, PDI, and entrapment efficiency were compared with two widely used laboratory scale methods, i.e., ultracentrifugation and centrifugal ultrafiltration. RESULTS: The novel stirred cell ultrafiltration method demonstrated liposomal purification within ~30 min with complete liposomal recovery showing minimal processing impact, i.e., ˂0.25 fold rise in particle size, ~0.5 fold rise in PDI, and ~4% loss in % entrapment efficiency, respectively. Whereas ultracentrifugation and centrifugal ultrafiltration methods resulted in ~4 fold and ˃2 fold rise in particle size, ˃10 fold and ˃5 fold rise in PDI, and ˃25% and ~6% loss in entrapment efficiency, respectively. CONCLUSION: The unique and product-friendly operational features of stirred cell ultrafiltration method demonstrated simple, rapid, and efficient liposomal purification without affecting CQAs of liposomal vesicles. This method was also evidently found to be product-friendly, rugged, versatile, and scalable up to large production batch processing, overcoming major drawbacks of presently used methods.

Formulation design and optimization of cationic-charged liposomes of brimonidine tartrate for effective ocular drug delivery by design of experiment (DoE) approach.

OBJECTIVE: The present study was aimed to design and optimize brimonidine tartrate (BRT) loaded cationic-charged liposome formulation with enhanced trans-corneal drug permeation, prolonged corneal residence, and sustained drug release for effective ocular delivery. METHODS: Design of experiment (DoE) based formulation optimization was done by three-factor, three-level Box-Behnken design selecting lipid, cholesterol, and drug content as independent variables and particle size (PS), polydispersity index (PDI), zeta potential (ZP), entrapment efficiency (EE%), and cumulative % drug release (CDR) as response variables. The optimized formulation consisting of 79.2 mM lipid, 36.2 mM cholesterol, and 15.8 mg/mL drug was prepared by thin film hydration-sonication method using EPCS:DOTAP (1:1) as lipid component and characterized for all desired critical quality attributes (CQAs), drug release kinetics, TEM, DSC, XRD analysis, ex vivo trans-corneal drug permeation, and physical stability studies. RESULTS: The optimized liposome formulation exhibited experimentally observed responses close to predicted values having 150.4 nm (PS), 0.203 (PDI), 30.62 mV (ZP), and 55.17% (EE). The observed CDR (%) was 36.15% at 1 h and 91.13% at 12 h exhibiting sustained drug release profile and followed Higuchi drug release kinetics. The TEM, DSC, and XRD studies revealed spherical, nanosized, small unilamellar vesicles effectively entrapping BRT in liposomes. The ex vivo permeation study across goat cornea recorded apparent permeability (Papp) 1.011 ± 0.07 cm.min-1 and steady-state flux (Jss) 17.63 ± 1.22 µg.cm-2.min-1 showing >2-fold enhanced drug permeation as compared to BRT solution. CONCLUSION: The developed liposomal formulation possessed all recommended CQAs in optimal range with enhanced trans-corneal drug permeation and remained physically stable in 3 months stability study.

Purification of Drug Loaded PLGA Nanoparticles Prepared by Emulsification Solvent Evaporation Using Stirred Cell Ultrafiltration Technique.

PURPOSE: The emulsifiers in an exceedingly higher level are used in the preparation of drug loaded polymeric nanoparticles prepared by emulsification solvent evaporation method. This creates great problem to the formulator due to their serious toxicities when it is to be administered by parenteral route. The final product is therefore required to be freed from the used surfactants by the conventional purification techniques which is a cumbersome job. METHODS: The solvent resistant stirred cell ultrafiltration unit (Millipore) was used in this study using polyethersulfone ultrafiltration membrane (Biomax®) having pore size of NMWL 300 KDa as the membrane filter. The purification efficiency of this technique was compared with the conventional centrifugation technique. RESULTS: The flow rate of ultrafiltration was optimized for removal of surfactant (polyvinyl alcohol) impurities to the acceptable levels in 1-3.5 h from the nanoparticle dispersion of tamoxifen prepared by emulsification solvent evaporation method. CONCLUSIONS: The present investigations demonstrate the application of solvent resistant stirred cell ultrafiltration technique for removal of toxic impurities of surfactant (PVA) from the polymeric drug nanoparticles (tamoxifen) prepared by emulsification solvent evaporation method. This technique offers added benefit of producing more concentrated nanoparticles dispersion without causing significant particle size growth which is observed in other purification techniques, e.g., centrifugation and ultracentrifugation.

Hydroxypropyl- ß -cyclodextrin: A Novel Transungual Permeation Enhancer for Development of Topical Drug Delivery System for Onychomycosis.

The treatment of onychomycosis is a challenging task because of unique barrier properties of the nail plate which hampers the passage of antifungal drugs in a concentration required to eradicate the deeply seated causative fungi in the nail bed. In present investigation, application of hydroxypropyl-ß-cyclodextrin (HP-ß-CD) was established as an effective and nail friendly transungual drug permeation enhancer especially for poorly water soluble drugs using terbinafine hydrochloride as a poorly soluble drug. HP-ß-CD significantly improves hydration of nail plates and increases solubility of terbinafine hydrochloride in the aqueous environment available therein, which leads to uninterrupted drug permeation through water filled pores of hydrogel-like structure of hydrated nail plates. A nail lacquer formulation was designed with an objective to deliver the drug in an effective concentration across nail plates, using HP-ß-CD as a permeation enhancer. The formulations containing HP-ß-CD showed higher flux than the control formulation in in vitro drug permeation study. The formulation containing 10% w/v of HP-ß-CD showed maximum flux of 4.586 ± 0.08 µg/mL/cm(2) as compared to the control flux of 0.868 ± 0.06 µg/mL/cm(2). This finding supports application of HP-ß-CD as an effective permeation enhancer for transungual delivery of terbinafine hydrochloride and possibly other poorly water soluble drugs where HP-ß-CD can act as a solubilizer.

Hydration of nail plate: a novel screening model for transungual drug permeation enhancers.

Drug delivery by topical route for the treatment of onychomycosis, a nail fungal infection, is challenging due to the unique barrier properties of the nail plate which imparts high resistance to the passage of antifungal drugs. Permeation enhancers are used in transungual formulations to improve the drug flux across the nail plate. Selection of the effective permeation enhancer among the available large pool of permeation enhancers is a difficult task. Screening the large number of permeation enhancers using conventional Franz diffusion cells is laborious and expensive. The objective of present study was to evolve a simple, accurate and rapid method for screening of transungual drug permeation enhancers based on the principle of hydration of nail plate. The permeation enhancer which affects the structural or physicochemical properties of nail plate would also affect their hydration capacity. Two screening procedures namely primary and secondary screenings were evolved wherein hydration and uptake of ciclopirox olamine by nail plates were measured. Hydration enhancement factor, HEF(24) and drug uptake enhancement factor, UEF(24) were determined for screening of 23 typical permeation enhancers. The Pearson's correlation coefficient between HEF(24) and UEF(24) was determined. A good agreement between the HEF(24) and UEF(24) data proved the validity of the proposed nail plate hydration model as a screening technique for permeation enhancers.

Formulation optimization of long-acting depot injection of aripiprazole by using D-optimal mixture design.

Non-adherence to medication specifications is a major cause for poor outcomes in the therapy of schizophrenia. In situ implantable preparation of aripiprazole, an atypical antipsychotic drug, was intended with the aim to improve the patient compliance and to offer an effective antipsychotic drug therapy. D-optimal mixture design was employed to design and optimize long-acting depot injection of aripiprazole using polylactide-co-glycolide (PLGA) 50:50, 75:25, 85:15, and cholesterol as release rate-retarding material. Desirability technique was used for the optimization of formulation. Predicted optimized formulation was experimentally validated, and it was found that the developed formulation releases the drug for a 14-day time period. The optimized formulation showed that the cholesterol-containing formulation exhibits a better drug release profile. The pharmacokinetic studies confirmed that the developed cholesterol-based depot formulation was capable of releasing the drug for a time period of more than 14 days. The implant formulation was sterilized by gamma radiation and ethylene oxide sterilization method. The D-optimal mixture design was proved to be an efficient technique for the formulation optimization.

Optimization of formulation variables for the development of long acting microsphere based depot injection of olanzapine.

This work was aimed to optimize the composition of microspheres of olanzapine to design long acting depot injection for the treatment of psychosis. Solvent evaporation method was used for the fabrication of microspheres. Different formulation variables for the solvent evaporation method, viz., effect of theoretical drug loading, type of surfactant and its concentration, temperature, volume of external phase and presence of salt in external aqueous phase, conditions and time of solvent evaporation and drying methodology were optimized. The microspheres were characterized for encapsulation efficiency, particle size, surface morphology, residual solvent content, drug release profile and drug release kinetics. The optimized formulation showed consistent drug release for upto 14 days time period.

Formulation development and release studies of indomethacin suppositories.

Indomethacin suppositories were prepared by using water-soluble and oil soluble suppository bases, and evaluated for in vitro release by USP I and modified continuous flow through bead bed apparatus. Effect of the Tween 80 (1% and 5%) was further studied on in vitro release of the medicament. Release rate was good in water-soluble suppositories bases in comparison to oil soluble suppositories bases. Release was found to be greater in modified continuous flow through bead bed apparatus. When surfactant was used in low concentration then release rate was much greater, as compared to high concentration. When stability studies were performed on the prepared indomethacin suppositories it was found that suppositories made by water-soluble base had no significant changes while suppositories prepared by oil soluble bases, had some signs of instability.