Effect of Particle Size and Viscosity of Suspensions on Topical Ocular Bioavailability of Budesonide, a Corticosteroid.

Purpose: To determine the effect of particle size and viscosity of suspensions on topical ocular bioavailability of budesonide, a corticosteroid drug. Methods: Budesonide microparticle and nanoparticle (MP and NP) suspensions were prepared with or without homogenization and microfluidization. Using different grades of hydroxyl propyl methyl cellulose, low viscosity NP (NP-LV) and low and high viscosity MP (MP-LV and MP-HV) were prepared. Suspensions were characterized for particle size, viscosity, and osmolality. Budesonide suspensions were administered topically to rabbits and aqueous humor was collected and analyzed for budesonide. Budesonide Cmax, tmax, and the area under the concentration time curve (AUC (0-6h)) values were determined. The geometric mean ratio of AUC and bioequivalence was evaluated using a bootstrap method. Results: The particle sizes for NP and MP were ∼700 and 2,000 nm. The viscosities for low and HV formulations were ∼5 and 50 cP. The geometric mean budesonide Cmax values for the suspensions NP-LV, MP-LV, and MP-HV were 0.22, 0.22, and 0.31 µg/g, tmax values were 0.67, 0.60 and 0.53 h, and AUC0-6h values were 0.72, 0.53, and 0.95 µg h/g, respectively. Bootstrap analysis indicated that the 90% confidence intervals of the geometric mean ratio of AUC0-6h values were 1.00-1.74 (MP-HV vs. NP-LV), 0.57-0.96 (MP-LV vs. NP-LV), and 0.45-0.70 (MP-LV vs. MP-HV). Conclusions: The 3 budesonide suspensions assessed in this study were not bioequivalent. Results suggested that an increase in viscosity improves the bioavailability of budesonide from the microsuspension formulation.

Retracted: Self-assembled Phenylalanine-α,ß-dehydrophenylalanine Nanotubes for Sustained Intravitreal Delivery of a Multi-targeted Tyrosine Kinase Inhibitor.

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Investigation Committee of the University of Colorado, Denver, USA, and the Editor. The Committee has come to the conclusion that author Kadam has knowingly and intentionally falsified and/or fabricated results by manipulating LC-MS/MS peak area data to smooth kinetics and/or alter statistical significance for Figure 6. The standard curve for the drug pazopanib was falsified to make it appear linear. In fact, the raw data for the standard curves were highly scattered and non-linear, resulting in an unusable standard curve. As a result, the pazopanib values calculated from the fabricated curve are completely unreliable. The Committee found no evidence that any of the other authors was aware of and/or participated in any activity amounting to Scientific Misconduct.

Self-assembled phenylalanine-α,ß-dehydrophenylalanine nanotubes for sustained intravitreal delivery of a multi-targeted tyrosine kinase inhibitor.

Current standard of care for sustained back of the eye drug delivery is surgical placement or injection of large, slow release implants using a relatively large 22 gauge needle. We designed novel dipeptide (phenylalanine-α,ß-dehydrophenylalanine; Phe-∆Phe) based nanotubes with a diameter of ~15-30 nm and a length of ~1500 nm that could be injected with a 33 gauge needle for sustained intravitreal delivery of pazopanib, a multi-targeted tyrosine kinase inhibitor. The drug could be loaded during nanotube assembly or post-loaded after nanotube formation, with the former being more efficient at 25% w/w pazopanib loading and ~55% loading efficiency. Plain and peptide loaded nanotube were non-cytotoxic to retinal pigment epithelial cells even at a concentration of 200 µg/ml. Following intravitreal injection of fluorescently labeled nanotubes using a 33 gauge needle in a rat model, the nanotube persistence and drug delivery were monitored using noninvasive fluorophotometry, electron microscopy and mass spectrometry analysis. Nanotubes persisted in the vitreous humor during the 15 days study and pazopanib levels in the vitreous humor, retina, and choroid-RPE at the end of the study were 4.5, 5, and 2.5-folds higher, respectively, compared to the plain drug. Thus, Phe-∆Phe nanotubes allow intravitreal injections with a small gauge needle and sustain drug delivery.

Nanoparticles in porous microparticles prepared by supercritical infusion and pressure quench technology for sustained delivery of bevacizumab.

Nanoparticles in porous microparticles (NPinPMP), a novel delivery system for sustained delivery of protein drugs, was developed using supercritical infusion and pressure quench technology, which does not expose proteins to organic solvents or sonication. The delivery system design is based on the ability of supercritical carbon dioxide (SC CO2) to expand poly(lactic-co-glycolic) acid (PLGA) matrix but not polylactic acid (PLA) matrix. The technology was applied to bevacizumab, a protein drug administered once a month intravitreally to treat wet age related macular degeneration. Bevacizumab coated PLA nanoparticles were encapsulated into porosifying PLGA microparticles by exposing the mixture to SC CO2. After SC CO2 exposure, the size of PLGA microparticles increased by 6.9-fold. Confocal and scanning electron microscopy studies demonstrated the expansion and porosification of PLGA microparticles and infusion of PLA nanoparticles inside PLGA microparticles. In vitro release of bevacizumab from NPinPMP was sustained for 4 months. Size exclusion chromatography, fluorescence spectroscopy, circular dichroism spectroscopy, SDS-PAGE, and ELISA studies indicated that the released bevacizumab maintained its monomeric form, conformation, and activity. Further, in vivo delivery of bevacizumab from NPinPMP was evaluated using noninvasive fluorophotometry after intravitreal administration of Alexa Fluor 488 conjugated bevacizumab in either solution or NPinPMP in a rat model. Unlike the vitreal signal from Alexa-bevacizumab solution, which reached baseline at 2 weeks, release of Alexa-bevacizumab from NPinPMP could be detected for 2 months. Thus, NPinPMP is a novel sustained release system for protein drugs to reduce frequency of protein injections in the therapy of back of the eye diseases.

Development and optimization of thiolated dendrimer as a viable mucoadhesive excipient for the controlled drug delivery: an acyclovir model formulation.

In the present study we report the development of novel thiolated dendrimers for mucoadhesive drug delivery. The thiolated dendrimers were synthesized by conjugating PAMAM dendrimer (G3.5)with cysteamine at two different molar ratios, i.e. 1:30 (DCys1) and 1:60 (DCys2). The thiolated dendrimers were further encapsulated with acyclovir (DCys1Ac and DCys2Ac) and the conjugates were characterized for thiol content, drug loading, drug release, and mucoadhesive behavior. The thiolated dendrimer conjugates showed thiol content of 10.56 ± 0.34 and 68.21 ± 1.84 µM/mg of the conjugate for DCys1 and DCys2, respectively. The acyclovir loading was observed to be highest in dendrimer drug conjugate (DAc) compared to other DCys1Ac and DCys2Ac conjugates. The thiolated dendrimers showed sustained release of acyclovir and showed higher mucoadhesion. The in vitro mucoadhesive activity of DCys2Ac was 1.53 and 2.89 fold higher mucoadhesion compared to DCys1Ac and DAc, respectively. These results demonstrated the usefulness of thiolated dendrimers as a mucoadhesive carrier and represent a novel platform for drug delivery. FROM THE CLINICAL EDITOR: This study demonstrates the utility of thiolated dendrimers as mucoadhesive carriers as reported in an acyclovir delivery model system.

Development of sustained-release microspheres for the delivery of SAR 1118, an LFA-1 antagonist intended for the treatment of vascular complications of the eye.

The objective of this study was to design 1, 3, and 6 month sustained-release poly (lactide-co-glycolide) (PLGA) microspheres of SAR 1118, a lymphocyte function-associated antigen-1 antagonist, using Design of Experiments. A full-factorial design was used to identify the polymers suitable for degradation in 1, 3, and 6 months and the Box-Behnken design was used to study the influence of the polymer type, polymer concentration, and drug to polymer ratio on drug loading, burst release, and particle size. From the full-factorial design, PLGA (50:50), PLGA (75:25), and PLGA (85:15) with an inherent viscosity of 0.3-0.5 dL/g were identified as polymers suitable for degradation in 1, 3, and 6 months, respectively. From the Box-Behnken design, the optimized polymer concentration (12% w/v) and drug to polymer ratio (0.15) were identified and used to prepare the SAR 1118-encapsulated microspheres with the above 3 polymers and evaluated for drug loading, burst release, and sustained drug release. The burst release in these 3 batches was less than 20% and the drug loading ranged from 15%-18%. More than 90% of SAR 1118 release from PLGA (50:50), PLGA (75:25), and PLGA (85:15) microspheres occurred in 1, 3, and 6 months, respectively. Thus, the in vitro cumulative release data are remarkably close to the predicted values. The results demonstrated the potential of the Design of Experiments in designing the SAR 1118 microspheres with a high loading efficiency, low burst release, and sustained release for a desired duration.

A novel vitamin B12-nanosphere conjugate carrier system for peroral delivery of insulin.

In spite of great potential, effective oral delivery of many vitamin B(12)-peptide/protein drug conjugates does not occur due to the limited uptake capacity of the VB(12) transport system, loss of bioactivity of native protein and/or intrinsic factor affinity of VB(12) and liability to GI degradation. In order to overcome these shortcomings in a two pronged way, we have endeavoured to develop a VB(12)-Nanoparticles (NPs) system to enhance the uptake capacity of both NPs and VB(12) transport to deliver orally effective insulin. NPs were prepared using different molecular weight dextrans and epichlorohydrin as cross-linker by an emulsion method. NPs surface was modified with succinic anhydride, and conjugated with amino VB(12) derivatives of carbamate linkage. VB(12) attachment was confirmed by IR, XPS analysis, and was quantified by HPLC (4.0 to 4.4% w/w of NPs). The pre-formed NPs conjugates (Zave=160-250 nm; polydisperse) were loaded with 2, 3 and 4% w/w of insulin, and the entrapment was found to be 45-70%. NPs conjugates were found to protect 65-83% of entrapped insulin against in vitro gut proteases. In vitro release studies exhibit an initial burst followed by diffusion controlled first order kinetics with 75-95% release within 48 h. After oral administration of these carriers (20 IU/kg), a nadir of 70-75% reduction in plasma glucose was found in 5 h, reached basal levels in 8-10 h, and a prolonged second phase was found until 54 h. The % pharmacological availability (PA) of 70 K NPs conjugate containing 2, 3 and 4% w/w insulin was 1.1, 1.9 and 2.6 fold higher, respectively compared to NPs without VB(12); consistent with the hypothesis that uptake was mediated by the vitamin B(12) transport. NPs of 70 K dextran showed 1.4 fold PA compared to 10 K while negligible action was observed with 200 K. The potential utilities of VB(12)-NPs carrier as an oral delivery platform of proteins, especially insulin via dextran-coated particles necessities further elaborate investigations.