Safety assessment of polymeric micelles as an ophthalmic drug delivery system for intravitreal administration of dasatinib.

BACKGROUND AND AIMS: Ocular safety/biocompatibility is an essential element of ophthalmic drug delivery. We previously applied poly(ethylene glycol)-block-poly(ɛ-caprolactone) (PEG-b-PCL) micelles to deliver dasatinib for the management of proliferative vitreoretinopathy (PVR) in vitro. Herein, we seek to ascertain the ocular safety/compatibility of blank and dasatinib loaded PEG-b-PCL micelles, which will set the stage for the future in vivo efficacy evaluations and/or clinical translation for PVR or other eye diseases. METHODS: To access the safety of blank and dasatinib loaded micelles, in vitro cell based assays (LDH cell membrane damage test, SRB cytotoxicity, TEER and permeability of RPE tight junctions), in vivo slit lamp biomicroscopy and optical coherence tomography, Ex vivo histology (H&E staining, GFAP immunofluorescence staining and TUNEL assay) were undertaken. RESULTS: Both blank and dasatinib loaded micelles showed remarkable safety profiles at cellular levels. They also caused negligible ocular toxicity/abnormalities up to 28 days post-intravitreal injection in mice. The micelles did not insult the cornea, as demonstrated by slit-lamp biomicroscopy. Ex vivo histology and in vivo optical coherence tomography revealed a normal retinal structure with minimal apoptosis and stresses. CONCLUSION: Taken together, both blank and dasatinib loaded micelles appear to be safe and their applications in drug delivery for eye diseases should be explored.

Oral delivery of paclitaxel by polymeric micelles: A comparison of different block length on uptake, permeability and oral bioavailability.

Drug solubility and permeability are two major challenges affecting oral delivery, the most popular route of drug administration. Polymeric micelles is an emerging technology for overcoming the current oral drug delivery hurdles. Previous study primarily focused on developing new polymers or new micellar systems and a systematic investigation of the impact of the polymer block length on solubility and permeability enhancement; and their subsequent effect on oral bioavailability is lacking. Herein, by using paclitaxel, a poorly soluble P-glycoproteins (P-gp) substrate, as a model, we aim to assess and compare the drug-loaded micelles prepared with two different molecular weight of poly(ethylene glycol)-block-poly(ε-caprolactone) (PEG-b-PCL), with the ultimate goal of establishing a strong scientific rationale for proper design of formulations for oral drug delivery. PEG-b-PCL (750:570) (PEG17-b-PCL5) and PEG-b-PCL (5k:10k) (PEG114-b-PCL88) effectively enhanced the solubility of paclitaxel compared to the free drug. PEG-b-PCL (750:570) increased both P-gp and non P-gp substrate cellular uptake and increased the apparent permeability coefficient of a P-gp substrate. In vivo animal study showed that PEG-b-PCL micelles efficiently enhanced the oral bioavailability of paclitaxel. In addition to solubility enhancement, polymer choice also plays a pivotal role in determining the oral bioavailability improvement, probably via permeation enhancement. In conclusion, the knowledge gained in this study enables rational design of polymeric micelles to overcome the current challenges of oral drug delivery and it also provides a basis for future clinical translation of the technology.

Orally-dissolving film for sublingual and buccal delivery of ropinirole.

Ropinirole is a very important treatment option for Parkinson's disease (PD), a major threat to the aging population. However, this drug undergoes extensive first-pass metabolism, resulting in a low oral bioavailability. Moreover, the necessity of frequent administration due to the short half-life of ropinirole may jeopardize patient compliance. Indeed, taking this drug in solid oral dosage forms (e.g. Tablet) can be a challenge because of the tremor, rigidity, limited mobility, and impaired drug absorption experienced by PD patients. In light of these, there is a pressing need to devise formulations for the delivery of ropinirole that allow simple and easy administration and fast drug action, as well as avoidance of first-pass metabolism and overcoming the challenge of impaired absorption due to gastrointestinal dysfunctions, etc. Herein, we seek to overcome all these challenges via sublingual or buccal delivery of orally-dissolving films. Accordingly, we aimed to fabricate and characterize orally-dissolving films of ropinirole and assess their in vivo pharmacokinetics after sublingual and buccal administration. The ropinirole oral film was non-toxic and exhibited fast disintegration and dissolution and was physically stable for at least 28 days. Upon buccal/sublingual administration of the oral films, ropinirole reached the systemic circulation within 15 min and bioavailability was significantly improved, which may be attributable to avoidance of first-pass metabolism via absorption through the oral cavity. In conclusion, our ropinirole oral film improved bioavailability after sublingual or buccal administration. This formulation potentially overcomes biopharmaceutical challenges and provide a convenient means of administration of ropinirole or other anti-PD drugs.

Oligonucleotide-conjugated nanoparticles for targeted drug delivery via scavenger receptors class A: An in vitro assessment for proof-of-concept.

Spherical nucleic acid gold nanoparticles represent a unique nanotechnology in which the spherical arrangement of oligonucleotides enables the nanoparticles to be efficiently internalized into cells expressing scavenger receptors class A (SR-A). Herein, we seek to replace the gold core with a biodegradable polymeric construct and explore their potential applications in targeted drug delivery. Oligonucleotide-conjugated poly(ethylene glycol)-block-poly(ε-caprolactone) was synthesized and characterized by 1H NMR and gel electrophoresis. This polymer was applied to fabricate micellar nanoparticles (OLN-NPs) by an anti-solvent method. These nanoparticles have a mean particle size about 58.1nm with a narrow size distribution (PDI <0.2) and they were also non-cytotoxic. Relative to non-targeted NPs, OLN-NPs exhibited substantially better uptake (3.94×) in a mouse endothelial cell line (C166), attributing to lipid-raft-mediated endocytosis via SR-A. To explore the potential applications of OLN-NPs as drug carriers, paclitaxel, a poorly soluble anti-angiogenic compound, was selected as the model. OLN-NPs increased the solubility of paclitaxel by at least 300×. The boosted drug solubility in conjunction with improved cellular uptake translated into enhanced in vitro efficacy in the inhibition of angiogenesis. In conclusions, OLN-NPs show considerable promise in targeted drug delivery and their potential applications should be further investigated.

Effect of Alkylation on the Cellular Uptake of Polyethylene Glycol-Coated Gold Nanoparticles.

Alkyl groups (CnH2n+1) are prevalent in engineered bionanomaterials used for many intracellular applications, yet how alkyl groups dictate the interactions between nanoparticles and mammalian cells remains incomprehensively investigated. In this work, we report the effect of alkylation on the cellular uptake of densely polyethylene glycol-coated nanoparticles, which are characterized by their limited entry into mammalian cells. Specifically, we prepare densely PEGylated gold nanoparticles that bear alkyl chains of varying carbon chain lengths (n) and loading densities (termed "alkyl-PEG-AuNPs"), followed by investigating their uptake by Kera-308 keratinocytes. Strikingly, provided a modest alkyl mass percentage of 0.2% (2 orders of magnitude lower than that of conventional lipid-based NPs) in their PEG shells, dodecyl-PEG-AuNPs (n = 12) and octadecyl-PEG-AuNPs (n = 18) can enter Kera-308 cells 30-fold more than methoxy-PEG-AuNPs (no alkyl groups) and hexyl-PEG-AuNPs (n = 6) after 24 h of incubation. Such strong dependence on n is valid for all serum concentrations considered (even under serum-free conditions), although enhanced serum levels can trigger the agglomeration of alkyl-PEG-AuNPs (without permanent aggregation of the AuNP cores) and can attenuate their cellular uptake. Additionally, alkyl-PEG-AuNPs can rapidly enter Kera-308 cells via the filipodia-mediated pathway, engaging the tips of membrane protrusions and accumulating within interdigital folds. Most alkyl-PEG-AuNPs adopt the "endo-lysosomal" route of trafficking, but ∼15% of them accumulate in the cytosol. Regardless of intracellular location, alkyl-PEG-AuNPs predominantly appear as individual entities after 24 h of incubation. Our work offers insights into the incorporation of alkyl groups for designing bionanomaterials for cellular uptake and cytosolic accumulation with intracellular stability.

Micellar delivery of dasatinib for the inhibition of pathologic cellular processes of the retinal pigment epithelium.

The objective of this study was to fabricate dasatinib-loaded nanoparticles and evaluate their efficacy in inhibiting cellular processes of the retinal pigment epithelium (RPE) related to proliferative vitreoretinopathy (PVR), for which there are no approved pharmacological approaches. We successfully encapsulated dasatinib, a poorly soluble multi-targeted tyrosine kinase inhibitor which has great potential for the treatment of PVR, into nanoparticles prepared from micellation of PEG-b-PCL. The size of the nanomicelles was approximately 55nm with a narrow distribution. They increased the solubility of dasatinib by 475× and provided a sustained drug release. ARPE-19, an immortal RPE cell line, was used to assess the in vitro efficacy of micellar dasatinib because the RPE is believed to play a key role in the pathogenesis of PVR. Three cell-based assays, namely, proliferation, adhesion and migration, which represent three important PVR-related cellular changes of the RPE, were conducted and the cytotoxicity of micelles was also evaluated. Both blank and dasatinib-loaded micelles were non-cytotoxic towards ARPE-19 cells. Micellar dasatinib significantly inhibited cell proliferation, adhesion and migration compared to the free drug; this might be attributable to enhanced solubility. PEG-b-PCL micelles were taken up into the ARPE-19 cells by an energy-dependent clatharin and caveolae-mediated endocytosis. Our results indicated that cellular uptake and the anti-proliferation effect of drugloaded micelles were linearly correlated. Drug loading appears to be a critical parameter for cellular uptake which in turn impacts the in vitro bioactivities of polymeric micelles. Our results clearly demonstrated that dasatinib-encapsulated micelles offer considerable promise in the management of PVR.

Regioselective acceptorless dehydrogenative coupling of N-heterocycles toward functionalized quinolines, phenanthrolines, and indoles.

A new strategy has been developed for the oxidant- and base-free dehydrogenative coupling of N-heterocycles at mild conditions. Under the action of an iridium catalyst, N-heterocycles undergo multiple sp(3) CH activation steps, generating a nucleophilic enamine that reacts in situ with various electrophiles to give highly functionalized products. The dehydrogenative coupling can be cascaded with Friedel-Crafts addition, resulting in a double functionalization of the N-heterocycles.

A simple iridicycle catalyst for efficient transfer hydrogenation of N-heterocycles in water.

A cyclometalated iridium complex is shown to catalyse the transfer hydrogenation of various nitrogen heterocycles, including but not limited to quinolines, isoquinolines, indoles and pyridinium salts, in an aqueous solution of HCO2H/HCO2Na under mild conditions. The catalyst shows excellent functional-group compatibility and high turnover number (up to 7500), with catalyst loadings as low as 0.01 mol % being feasible. Mechanistic investigation of the quinoline reduction suggests that the transfer hydrogenation proceeds via both 1,2- and 1,4-addition pathways, with the catalytic turnover being limited by the step of hydride transfer.

A unified lead-oriented synthesis of over fifty molecular scaffolds.

Controlling the properties of lead molecules is critical in drug discovery, but sourcing large numbers of lead-like compounds for screening collections is a major challenge. A unified synthetic approach is described that enabled the synthesis of 52 diverse lead-like molecular scaffolds from a minimal set of 13 precursors. The divergent approach exploited a suite of robust, functional group-tolerant transformations. Crucially, after derivatisation, these scaffolds would target significant lead-like chemical space, and complement commercially-available compounds.

A convergent rhodium-catalysed asymmetric synthesis of tetrahydroquinolines.

Rh-catalysed conjugate additions of 2-aminophenyl boronic acid derivatives were exploited in diastereoselective and asymmetric syntheses of tetrahydroquinolines. In both cases, combinatorial variation of the substitution of the tetrahydroquinoline ring system was possible.