In situ gelling systems based on Pluronic F127/Pluronic F68 formulations for ocular drug delivery

This study evaluated the use of Pluronic F127 and Pluronic F68 as excipients for formulating in situ gelling systems for ocular drug delivery. Thermal transitions have been studied in aqueous solutions of Pluronic F127, Pluronic F68 as well as their binary mixtures using differential scanning calorimetry, rheological measurements, and dynamic light scattering. It was established that the formation of transparent gels at physiologically relevant temperatures is observed only in the case of 20 wt % of Pluronic F127. The addition of Pluronic F68 to Pluronic F127 solutions increases the gelation temperature of binary formulation to above physiological range of temperatures. The biocompatibility evaluation of these formulations using slug mucosa irritation assay and bovine corneal erosion studies revealed that these polymers and their combinations do not cause significant irritation. In vitro drug retention study on glass surfaces and freshly excised bovine cornea showed superior performance of 20 wt % Pluronic F127 compared to other formulations. In addition, in vivo studies in rabbits demonstrated better retention performance of 20 wt % Pluronic F127 compared to Pluronic F68. These results confirmed that 20 wt % Pluronic F127 offers an attractive ocular formulation that can form a transparent gel in situ under physiological conditions with minimal irritation.

Relationship between composition and organizational levels of nanostructured systems formed by Oleth 10 and PPG-5-Ceteth-20 for potential drug delivery

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Microemulsions Containing Medium-Chain Glycerides as Transdermal Delivery Systems for Hydrophilic and Hydrophobic Drugs

We evaluated the ability of microemulsions containing medium-chain glycerides as penetration enhancers to increase the transdermal delivery of lipophilic (progesterone) and hydrophilic (adenosine) model drugs as well as the effects of an increase in surfactant blend concentration on drug transdermal delivery. Microemulsions composed of polysorbate 80, medium-chain glycerides, and propylene glycol (1:1:1, w/w/w) as surfactant blend, myvacet oil as the oily phase, and water were developed. Two microemulsions containing different concentrations of surfactant blend but similar water/oil ratios were chosen; ME-lo contained a smaller concentration of surfactant than ME-hi (47:20:33 and 63:14:23 surfactant/oil/water, w/w/w). Although in vitro progesterone and adenosine release from ME-lo and ME-hi was similar, their transdermal delivery was differently affected. ME-lo significantly increased the flux of progesterone and adenosine delivered across porcine ear skin (4-fold or higher, p < 0.05) compared to progesterone solution in oil (0.05 +/- 0.01 mu g/cm(2)/h) or adenosine in water (no drug was detected in the receptor phase). The transdermal flux of adenosine, but not of progesterone, was further increased (2-fold) by ME-hi, suggesting that increases in surfactant concentration represent an interesting strategy to enhance transdermal delivery of hydrophilic, but not of lipophilic, compounds. The relative safety of the microemulsions was assessed in cultured fibroblasts. The cytotoxicity of ME-lo and ME-hi was significantly smaller than sodium lauryl sulfate (considered moderate-to-severe irritant) at same concentrations (up to 50 mu g/mL), but similar to propylene glycol (regarded as safe), suggesting the safety of these formulations.

Lipid, sugar and liposaccharide based delivery systems

Although there are formidable barriers to the oral delivery of biologically active drugs, considerable progress in the field has been made, using both physical and chemical strategies of absorption enhancement. A possible method to enhance oral absorption is to exploit the phenomenon of lipophilic modification and mono and oligosaccharide conjugation. Depending on the uptake mechanism targeted, different modifications can be employed. To target passive diffusion, lipid modification has been used, whereas the targeting of sugar transport systems has been achieved through drugs conjugated with sugars. These drug delivery units can be specifically tailored to transport a wide variety of poorly absorbed drugs through the skin, and across the barriers that normally inhibit absorption from the gut or into the brain. The delivery system can be conjugated to the drug in such a way as to release the active compound after it has been absorbed (i.e. the drug becomes a prodrug), or to form a biologically stable and active molecule (i.e. the conjugate becomes a new drug moiety). Examples where lipid, sugar and lipid-sugar conjugates have resulted in enhanced drug delivery will be highlighted in this review.

Gold nanoparticulate systems for new anticancer compounds delivery

My master studies have resulted in the following publication: Martins P, Rosa D, Fernandes AR, Baptista PV. 2014. Nanoparticle Drug Delivery Systems: Recent Patents and Applications in Nanomedicine. Recent Patents in Nanomedicine. 3(2):105-118.

Silica nanoparticles as dexamethasone delivery systems able to induce the osteogenic differentiation of human bone marrow-derived mesenchymal stem cells

Bioactive glasses, especially silica-based materials, are reported to pres- ent osteoconductive and osteoinductive properties, fundamental char- acteristics in bone regeneration [1,2]. Additionally, dexamethasone (Dex) is one of the bioactive agents able to induce the osteogenic differ- entiation of mesenchymal stem cells by increasing the alkaline phos- phatase activity, and the expression levels of Osteocalcin and Bone Sialoprotein [3]. Herein, we synthesised silica (SiO2) nanoparticles (that present inherent bioactivity and ability to act as a sustained drug delivery system), and coated their surface using poly-L-lysine (PLL) and hyaluronic acid (HA) using the layer-by-layer processing technique. Further on, we studied the influence of these new SiO2-polyelectrolyte coated nanoparticles as Dex sustained delivery systems. The SiO2 nanoparticles were loaded with Dex (SiO2-Dex) and coated with PLL and HA (SiO2-Dex-PLL-HA). Their Dex release profile was evaluated and a more sustained release was obtained with the SiO2-Dex-PLL-HA. All the particles were cultured with human bone marrow-derived mes- enchymal stem cells (hBMSCs) under osteogenic differentiation culture conditions. hBMSCs adhered, proliferated and differentiated towards the osteogenic lineage in the presence of SiO2 (DLS 174nm), SiO2-Dex (DLS 175nm) and SiO2-Dex-PLL-HA (DLS 679nm). The presence of these materials induced the overexpression of osteogenic transcripts, namely of Osteocalcin, Bone Sialoprotein and Runx2. Scanning Elec- tron Microscopy/Electron Dispersive Spectroscopy analysis demon- strated that hBMSCs synthesised calcium phosphates when cultured with SiO2-Dex and SiO2-Dex-PLL-HA nanoparticles. These results indi- cate the potential use of these SiO2-polyelectrolytes coated nanoparti- cles as dexamethasone delivery systems capable of promoting osteogenic differentiation of hBMSCs.

Colloidal systems for the delivery of cyclosporin A to the anterior segment of the eye.

Due to the eye's specific anatomical and physiological conformation, the treatment of eye diseases is a real challenge for pharmaceutical therapy. The presence of efficient protective barriers (i.e., the conjunctival and corneal membranes) and protective mechanisms (i.e., blinking and nasolachrymal drainage) makes this organ particularly impervious to local drug therapy. To overcome these issues, numerous strategies have been envisioned using pharmaceutical technology. Many formulations currently on the market or still under development are emulsions or colloidal systems intended to enhance precorneal residence time and corneal penetration, causing a consequent increase in drug bioavailability after instillation. After a review of some recent developments in the field of cyclosporin A formulations for the eye, a novel micellar formulation of cyclosporine A based on a diblock methoxy-poly(ethylene glycol)-hexysubstituted poly(lactides) (MPEG-hexPLA) is described.

The use of protein structure/activity relationships in the rational design of stable particulate delivery systems

The recombinant heat shock protein (18 kDa-hsp) from Mycobacterium leprae was studied as a T-epitope model for vaccine development. We present a structural analysis of the stability of recombinant 18 kDa-hsp during different processing steps. Circular dichroism and ELISA were used to monitor protein structure after thermal stress, lyophilization and chemical modification. We observed that the 18 kDa-hsp is extremely resistant to a wide range of temperatures (60% of activity is retained at 80ºC for 20 min). N-Acylation increased its ordered structure by 4% and decreased its ß-T1 structure by 2%. ELISA demonstrated that the native conformation of the 18 kDa-hsp was preserved after hydrophobic modification by acylation. The recombinant 18 kDa-hsp resists to a wide range of temperatures and chemical modifications without loss of its main characteristic, which is to be a source of T epitopes. This resistance is probably directly related to its lack of organization at the level of tertiary and secondary structures.

Polysaccharide-based Polyion Complex Micelles as New Delivery Systems for Hydrophilic Cationic Drugs

Les micelles polyioniques ont émergé comme des systèmes prometteurs de relargage de médicaments hydrophiles ioniques. Le but de cette étude était le développement des micelles polyioniques à base de dextrane pour la relargage de médicaments hydrophiles cationiques utilisant une nouvelle famille de copolymères bloc carboxymethyldextran-poly(éthylène glycol) (CMD-PEG). Quatre copolymères CMD-PEG ont été préparés dont deux copolymères identiques en termes de longueurs des blocs de CMD et de PEG mais différent en termes de densité de charges du bloc CMD; et deux autres copolymères dans lesquels les blocs chargés sont les mêmes mais dont les blocs de PEG sont différents. Les propriétés d’encapsulation des micelles CMD-PEG ont été évaluées avec différentes molécules cationiques: le diminazène (DIM), un médicament cationique modèle, le chlorhydrate de minocycline (MH), un analogue semi-synthétique de la tétracycline avec des propriétés neuro-protectives prometteuses et différents antibiotiques aminoglycosidiques. La cytotoxicité des copolymères CMD-PEG a été évaluée sur différentes lignées cellulaires en utilisant le test MTT et le test du Bleu Alamar. La formation de micelles des copolymères de CMD-PEG a été caractérisée par différentes techniques telles que la spectroscopie RMN 1H, la diffusion de la lumière dynamique (DLS) et la titration calorimétrique isotherme (ITC). Le taux de relargage des médicaments et l’activité pharmacologique des micelles contenant des médicaments ont aussi été évalués. Les copolymères CMD-PEG n'ont induit aucune cytotoxicité dans les hépatocytes humains et dans les cellules microgliales murines (N9) après 24 h incubation pour des concentrations allant jusqu’à 15 mg/mL. Les interactions électrostatiques entre les copolymères de CMD-PEG et les différentes drogues cationiques ont amorcé la formation de micelles polyioniques avec un coeur composé du complexe CMD-médicaments cationiques et une couronne composée de PEG. Les propriétés des micelles DIM/CMDPEG ont été fortement dépendantes du degré de carboxyméthylation du bloc CMD. Les micelles de CMD-PEG de degré de carboxyméthylation du bloc CMD ≥ 60 %, ont incorporé jusqu'à 64 % en poids de DIM et ont résisté à la désintégration induite par les sels et ceci jusqu'à 400 mM NaCl. Par contre, les micelles de CMD-PEG de degré de carboxyméthylation ~ 30% avaient une plus faible teneur en médicament (~ 40 % en poids de DIM) et se désagrégeaient à des concentrations en sel inférieures (∼ 100 mM NaCl). Le copolymère de CMD-PEG qui a montré les propriétés micellaires les plus satisfaisantes a été sélectionné comme système de livraison potentiel de chlorhydrate de minocycline (MH) et d’antibiotiques aminoglycosidiques. Les micelles CMD-PEG encapsulantes de MH ou d’aminoglycosides ont une petite taille (< 200 nm de diamètre), une forte capacité de chargement (≥ 50% en poids de médicaments) et une plus longue période de relargage de médicament. Ces micelles furent stables en solution aqueuse pendant un mois; après lyophilisation et en présence d'albumine sérique bovine. De plus, les micelles ont protégé MH contre sa dégradation en solutions aqueuses. Les micelles encapsulant les drogues ont maintenu les activités pharmacologiques de ces dernières. En outre, les micelles MH réduisent l’inflammation induite par les lipopolysaccharides dans les cellules microgliales murines (N9). Les micelles aminoglycosides ont été quant à elles capable de tuer une culture bactérienne test. Toutefois les micelles aminoglycosides/CMDPEG furent instables dans les conditions physiologiques. Les propriétés des micelles ont été considérablement améliorées par des modifications hydrophobiques de CMD-PEG. Ainsi, les micelles aminoglycosides/dodecyl-CMD-PEG ont montré une taille plus petite et une meilleure stabilité aux conditions physiologiques. Les résultats obtenus dans le cadre de cette étude montrent que CMD-PEG copolymères sont des systèmes prometteurs de relargage de médicaments cationiques.

Self-immolative linkers in polymeric delivery systems

There has been significant interest in the methodologies of controlled release for a diverse range of applications spanning drug delivery, biological and chemical sensors, and diagnostics. The advancement in novel substrate-polymer coupling moieties has led to the discovery of self-immolative linkers. This new class of linker has gained popularity in recent years in polymeric release technology as a result of stable bond formation between protecting and leaving groups, which becomes labile upon activation, leading to the rapid disassembly of the parent polymer. This ability has prompted numerous studies into the design and development of self-immolative linkers and the kinetics surrounding their disassembly. This review details the main concepts that underpin self-immolative linker technologies that feature in polymeric or dendritic conjugate systems and outlines the chemistries of amplified self-immolative elimination.

Nanotechnological delivery systems for the oral administration of active molecules: Polymeric microparticles and microemulsions applied to anti-inflammatory and anti-infectious drugs

This thesis was devoted to the development of innovative oral delivery systems for two different molecules. In the first part, microparticles (MPs) based on xylan and Eudragit® S- 100 were produced and used to encapsulate 5-aminosalicylic acid for colon delivery. Xylan was extracted from corn cobs and characterized in terms of its physicochemical, rheological and toxicological properties. The polymeric MPs were prepared by interfacial cross-linking polymerization and spray-drying and characterized for their morphology, mean size and distribution, thermal stability, crystallinity, entrapment efficiency and in vitro drug release. MPs with suitable physical characteristics and satisfactory yields were prepared by both methods, although the spray-dried systems showed higher thermal stability. In general, spraydried MPs would be preferable systems due to their thermal stability and absence of toxic agents used in their preparation. However, drug loading and release need to be optimized. In the second part of this thesis, oil-in-water microemulsions (O/W MEs) based on mediumchain triglycerides were formulated as drug carriers and solubility enhancers for amphotericin B (AmB). Phase diagrams were constructed using surfactant blends with hydrophiliclipophilic balance values between 9.7 and 14.4. The drug-free and drug-loaded MEs presented spherical non-aggregated droplets around 80 and 120 nm, respectively, and a low polydispersity index. The incorporation of AmB was high and depended on the volume fraction of the disperse phase. These MEs did not reduce the viability of J774.A1 macrophage-like cells for concentrations up to 25 μg/mL of AmB. Therefore, O/W MEs based on propylene glycol esters of caprylic acid may be considered as suitable delivery systems for AmB

Modeling a system of phosphated cross-linked high amylose for controlled drug release. Part 2: Physical parameters, cross-linking degrees and drug delivery relationships

High amylose cross-linked to different degrees with sodium trimetaphosphate by varying base strength (2% or 4%) and contact time (0.5-4 h) was evaluated as non-compacted systems for sodium diclophenac controlled release. The physical properties and the performance of these products for sodium diclophenac controlled release from non-compacted systems were related to the structures generated at each cross-linking degree. For samples at 2% until 2 h the swelling ability, G' and eta* values increased with the cross-linking degree, because the longer polymer chains became progressively more entangled and linked. This increases water uptake and holding, favoring the swelling and resulting in systems with higher viscosities. Additionally, the increase of cross-linking degree should contribute for a more elastic structure. The shorter chains with more inter-linkages formed at higher cross-linking degrees (2%4h and 4%) make water caption and holding difficult, decreasing the swelling, viscosity and elasticity. For 2% samples, the longer drug release time exhibited for 2%4h sample indicates that the increase of swelling and viscosity contribute for a more sustained drug release, but the mesh size of the polymeric network seems to be determinant for the attachment of drug molecules. For the 4% samples, smaller meshes size should determine less sustained release of drug. (C) 2008 Elsevier B.V. All rights reserved.

In vitro characterization of coevaporates containing chitosan for colonic drug delivery

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Magnetic multiparticulate colonic delivery systems evaluated by AC Biosusceptometry

The biomagnetic technique called Alternate Current Biosusceptometry (ACB) is a proposal to evaluate a multiparticulate drug delivery system in the human gastrointestinal tract. Results show that ACB was able to quantify the gastrointestinal transit and spreading of the magnetic material and is an attractive tool for pharmaceutical research. © 2007.

Cyclodextrin Inclusion Complexes Loaded in Particles as Drug Carrier Systems

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)