RESUMEN

Branched polyesters of the general structure poly[vinyl-3-(dialkylamino)alkylcarbamate-co-vinyl acetate-co-vinyl alcohol]-graft-poly(D,L-lactide-co-glycolide) have shown potential for nano- and micro-scale drug delivery systems. Here the in vitro degradation behaviour with a special emphasis on elucidating structure-property relationships is reported. Effects of type and degree of amine substitution as well as PLGA side chain length were considered. In a first set of experiment, the weight loss of solvent cast films of defined size from 19 polymers was measured as a function of incubation in phosphate buffer (pH 7.4) at 37 degrees C over a time of 21 days. A second study was initiated focusing on three selected polymers in a similar set up, but with additional observation of pH influences (pH 2 and pH 9) and determination of water uptake (swelling) and molecular weights during degradation. Scanning electron micrographs have been recorded at selected time points to characterize film specimens morphologically after degradation. Our investigations revealed the potential to influence the degradation of this polymer class by the degree of amine substitution, higher degrees leading to faster erosion. The erosion rate could further be influenced by the type of amine functionality, DEAPA-modified polyesters degrading as fast as or slightly faster than DMAPA-modified polyesters and these degrading faster than DEAEA-PVA-g-PLGA. As a third option the degradation rate could be modified by the PLGA side chain length, shorter side chains leading to faster erosion. As compared to linear PLGA, remarkably shorter degradation times could be achieved by grafting short PLGA side chains onto amine-modified PVA backbones. Erosion times from less than 5 days to more than 4 weeks could be realized by selecting the type of amine functionality, the degree of amine substitution and the PLGA side chain length at the time of synthesis. In addition, the pathway of hydrolytic degradation can be tuned to be either mainly bulk or surface erosion.

Asunto(s)

Ácido Láctico/química , Poliésteres/química , Ácido Poliglicólico/química , Polivinilos/química , Espectroscopía de Resonancia Magnética , Microscopía Electrónica de Rastreo , Poliglactina 910/análogos & derivados , Poliglactina 910/química , Copolímero de Ácido Poliláctico-Ácido Poliglicólico , Alcohol Polivinílico/química

RESUMEN

Catheter-based local delivery of biodegradable nanoparticles (NP) with sustained release characteristics represents a therapeutic approach to reduce restenosis. Paclitaxel-loaded NP consisting of poly(vinyl alcohol)-graft-poly(lactide-co-glycolide) (PVA-g-PLGA) with varying PLGA chain length as well as poly(lactide-co-glycolide) (PLGA), were prepared by a solvent evaporation technique. NP of <180 nm in diameter characterized by photon correlation spectroscopy (PCS), scanning electron microscopy (SEM), and atomic force microscopy (AFM) are spherical and show smooth surfaces. Yields typically range from 80 to 95% with encapsulation efficiencies between 77 and 87%. The extent of initial in vitro paclitaxel release was affected by the PVA-g-PLGA composition. Blank nanoparticles from PVA(300)-g-PLGA(30) and PVA(300)-g-PLGA(15) showed excellent biocompatibility in rabbit vascular smooth muscle cells (RbVSMC) at polymer concentrations of 0.37 mg/ml. Paclitaxel-loaded NP have an increased antiproliferative effect on cells in comparison to free drug. Confocal laser scanning microscopy of RbVSMC confirmed cellular uptake of nanoparticles composed of fluorescently labeled PVA(300)-g-PLGA(15) loaded with Oregon Green labeled paclitaxel. Cells showed a clearly increased fluorescence activity with a co-localization of paclitaxel and polymer nanoparticles during incubation with particle suspension. To evaluate the antirestenotic effect in vivo, paclitaxel-loaded nanoparticles were administered locally to the wall of balloon-injured rabbit iliac arteries using a porous balloon catheter. As a result a 50% reduction in neointimal area in vessel segments treated with paclitaxel-loaded nanoparticles compared to control vessel segments could be observed (local paclitaxel nanoparticle treated segments 0.80+/-0.19 mm(2), control segments 1.58+/-0.6 mm(2); p<0.05).

Asunto(s)

Constricción Patológica/tratamiento farmacológico , Sistemas de Liberación de Medicamentos/métodos , Ácido Láctico/administración & dosificación , Nanopartículas/administración & dosificación , Paclitaxel/administración & dosificación , Ácido Poliglicólico/administración & dosificación , Polímeros/administración & dosificación , Animales , Células Cultivadas , Constricción Patológica/metabolismo , Oclusión de Injerto Vascular/tratamiento farmacológico , Oclusión de Injerto Vascular/metabolismo , Arteria Ilíaca/efectos de los fármacos , Arteria Ilíaca/metabolismo , Ácido Láctico/farmacocinética , Masculino , Paclitaxel/farmacocinética , Ácido Poliglicólico/farmacocinética , Copolímero de Ácido Poliláctico-Ácido Poliglicólico , Polímeros/farmacocinética , Conejos

RESUMEN

Non-parenteral insulin delivery by the oral route is limited by epithelial barriers and enzymatic degradation. Nanosized insulin-complexes based on amine modified comb-like polyesters were designed to overcome these barriers. Protection of insulin in nanocomplexes (NC) from enzymatic degradation was investigated. The interaction with enterocyte-like Caco-2 cells in terms of cytotoxicity, transport through and uptake in the cell layers was evaluated by measuring transepithelial electrical resistance (TEER), release of lactate dehydrogenase (LDH) and insulin transport. The protection capacity of NC and their interaction with Caco-2 cells varied strongly as a function of lactide-grafting (hydrophobicity). With increasing lactide-grafting (P(26) < or = P(26)-1(LL) < or = P(26)-2(LL)) NC protected up to 95% of the insulin against degradation by trypsin. Transport and uptake into cell monolayers increased with higher l-lactid grafting. About 25% of a 1.25mg/ml TRITC-insulin NC dispersion with P(26)-2(LL) was recovered in Caco-2 cells after 90 min. A concentration dependent cytotoxicity profile was observed showing elevated LDH release and decreased TEER values. The cytotoxicity correlates with the surfactant like character of the polymers, decreasing the surface tension to 46 mN/m for the amphiphilic P(26)-2(LL). The observed TEER decrease was reversible after 20 h, suggesting that the biodegradable comb-polyesters offer a promising approach to overcome mucosal barriers.

Asunto(s)

Portadores de Fármacos , Hipoglucemiantes/metabolismo , Insulina/metabolismo , Absorción Intestinal , Mucosa Intestinal/metabolismo , Nanopartículas , Poliésteres/química , Células CACO-2 , Membrana Celular/metabolismo , Supervivencia Celular/efectos de los fármacos , Química Farmacéutica , Relación Dosis-Respuesta a Droga , Composición de Medicamentos , Estabilidad de Medicamentos , Impedancia Eléctrica , Humanos , Hipoglucemiantes/química , Insulina/química , Mucosa Intestinal/efectos de los fármacos , L-Lactato Deshidrogenasa/metabolismo , Poliésteres/síntesis química , Poliésteres/toxicidad , Factores de Tiempo , Tripsina/metabolismo

RESUMEN

DNA nano-carriers were formulated relying on biodegradable polyesters consisting of amine-modified poly(vinyl alcohol) (PVAL) backbones grafted with PLGA, based on the Marangoni effect thus avoiding detrimental shear or ultrasonic forces. These amine modified high molecular weight biodegradable polyesters combine specific characteristics, such as electrostatic interactions between DNA and cationic branched polyesters facilitating loading of NP with DNA. The resulting DNA containing NP showed hydrodynamic diameters in the range of 175-285 nm and highly positive xi-potentials, depending on the nitrogen to phosphate (N/P) ratio used for the particle formation. Atomic force microscopy (AFM) demonstrated well-defined spherical particle morphologies. DNA was released from NP upon incubation in PBS buffer in its intact supercoiled form. Agarose gel electrophoresis demonstrated that DNA within the NP was protected from enzyme degradation. The biological efficiency of the DNA delivery by this nano-carrier was demonstrated by an in vitro transfection assay using four cell lines. Reporter gene delivery of the amine-modified polymers was higher than naked DNA (Control) and raised with increasing degree of amine substitution. Also type of amine and distance of cationic charge from the backbone play an important role. Further, this feature was shown by Luciferase expression of the pCMV-Luc plasmid with PEI 25 kDa/DNA polyplexes and NP prepared with amine modified polyesters with a grafted PLGA chain length of 10 monomers compared at equal N/P ratios. DNA loaded NP from P(68)-10 showed 8x higher transfection efficiencies than the PEI 25 kDa at an N/P ratio of 9 for both preparations. These novel DNA nano-carriers merit further investigations in particular for DNA vaccination under in vivo conditions.

Asunto(s)

ADN/química , Portadores de Fármacos/química , Nanopartículas , Poliésteres/química , Aminas/química , Animales , Cationes , Desoxirribonucleasas , Humanos , Ácido Láctico/química , Ratones , Células 3T3 NIH , Ácido Poliglicólico/química , Copolímero de Ácido Poliláctico-Ácido Poliglicólico , Polímeros/química , Alcohol Polivinílico/química , Conejos , Solventes , Propiedades de Superficie , Transfección

RESUMEN

Although substantial progress in catheter and stent design has contributed to the success of percutaneous transluminal angioplasty (PTA) of atherosclerotic disease, the incidence of restenosis caused by in-stent neointimal hyperplasia remains a serious problem. Therefore, stents with a non-degradable polymer coating showing controlled release of active ingredients have become an attractive option for the site-specific delivery of anti-restenotic agents. Biodegradable coatings using polyesters, namely poly(lactic-co-glycolic acid) (PLGA) and different poly(vinyl alcohol)-graft-poly(lactic-co-glycolic acid) (PVA-g-PLGA) as paclitaxel-eluting stent coating materials were investigated here to evaluate their influence on the release kinetic. Whereas PLGA showed sigmoid release behavior, the paclitaxel release from PVA-g-PLGA films was continuous over 40 days without initial drug burst. Wide angle X-ray diffraction confirmed that paclitaxel is dissolved in the polymer matrix. Paclitaxel crystallization can be observed at a drug load of > or =10%. The effect of drug loading on polymer degradation was studied in films prepared from PVA300-g-PLGA30 with paclitaxel loadings of 5% and 15% over a time period of 6 weeks. The results suggest a surface-like erosion mechanism in films. A model stent (Jostent peripheral) coated with Parylene N, a poly(p-xylylene) (PPX) derivate, was covered with a second layer of PVA300-g-PLGA15, and PVA300-g-PLGA30 by using airbrush method. Morphology of coated stents, and film integrity after expansion from 3.12 to 5 mm was investigated by scanning electron microscopy (SEM). The devices resisted mechanical stress during stent expansion and merit further investigation under in vivo conditions.

Asunto(s)

Portadores de Fármacos/química , Ácido Láctico/química , Paclitaxel/farmacocinética , Ácido Poliglicólico/química , Polímeros/química , Alcohol Polivinílico/química , Stents , Antineoplásicos Fitogénicos/química , Antineoplásicos Fitogénicos/farmacocinética , Materiales Biocompatibles/química , Biodegradación Ambiental , Portadores de Fármacos/síntesis química , Microscopía Electrónica de Rastreo , Paclitaxel/química , Copolímero de Ácido Poliláctico-Ácido Poliglicólico , Tecnología Farmacéutica/instrumentación , Tecnología Farmacéutica/métodos , Factores de Tiempo , Difracción de Rayos X

RESUMEN

Novel, multifunctional polymers remain an attractive objective for drug delivery, especially for hydrophilic macromolecular drugs candidates such as peptides, proteins, RNA, and DNA. To facilitate intracellular delivery of DNA, new amine-modified poly(vinyl alcohol)s (PVAs) were synthesized by a two-step process using carbonyl diimidazole activated diamines to produce PVAs with different degrees of amine substitution. The resulting polymers were characterized using NMR, thermogravimetric analysis (TGA), and gelpermation chromatography (GPC). Atomic force microscopy (AFM), dynamic light scattering photon correlation spectroscopy (PCS), and zeta-potential were used to investigate polyplexes of DNA with PVA copolymers. These studies suggest an influence of the polycation structure on the morphology of condensed DNA in polyplexes. Significant differences were observed by changing both the degrees of amine substitution and the structure of the PVA backbone, demonstrating that both electrostatic and hydrophobic interactions affect DNA condensation. DNA condensation measured by an ethidium bromide intercalation assay showed a higher degree of condensation with pDNA with increasing degrees of amine substitution and more hydrophobic functional groups. These findings are in line with transfection experiments, in which a good uptake of these polymer DNA complexes was noted, unfortunately, with little endosomal escape. Co-administration of chloroquine resulted in increased endosomal escape and higher transfection efficiencies, due to disruption of the endosomal membrane. In this study, the structural requirements for DNA complexation and condensation were characterized to provide a basis for rational design of nonviral gene delivery systems.

Asunto(s)

Aminas , Plásmidos/administración & dosificación , Alcohol Polivinílico/farmacocinética , Transfección/métodos , Células 3T3 , Animales , Supervivencia Celular , Cloroquina/farmacología , Endosomas/efectos de los fármacos , Endosomas/metabolismo , Ratones , Plásmidos/farmacocinética , Alcohol Polivinílico/química , Alcohol Polivinílico/toxicidad , Relación Estructura-Actividad

RESUMEN

PURPOSE: The bioavailability and local tolerability of insulin containing nanocomplexes from amine-modified poly(vinyl alcohol)-graft-poly(L-lactide) were studied in rats. Histology of the nasal epithelium was studied to document integrity of the mucosa. METHODS: Nanocomplexes (NC) were prepared by spontaneous self-assembly of insulin and the water-soluble amphiphilic polymer. Changes in blood glucose and insulin blood concentration were monitored in anesthetized rats using a glucose meter and enzyme-linked immunosorbent assay, respectively. Histological sections of the nasal cavity were examined after H&E staining by light microscopy. RESULTS: NC reduced blood glucose level in fasted healthy rats by 20% after 50-80 min and in streptozotocin induced diabetic rats by 30% within 75-95 min compared to basal levels. In both animal models significant concentrations of human insulin were detected, with relative bioavailabilities F(rel) of 2.8 up to 8.3%. The more hydrophobic, lactic acid grafted polyester were more effective at a threefold higher polymer concentration, increasing the relative bioavailability F(rel) of a 5 IU/kg dose from 2.8 to 5.7%. Histological examination of the nasal mucosa after 4 h showed no signs of toxicity at the site of nasal administration. CONCLUSIONS: These results demonstrate that the NC significantly enhanced insulin absorption, suggesting that amphiphilic biodegradable comb-polymers offer a promising approach for nasal peptide delivery.

Asunto(s)

Sistemas de Liberación de Medicamentos , Insulina/administración & dosificación , Insulina/farmacocinética , Nanoestructuras/química , Mucosa Nasal/efectos de los fármacos , Administración Intranasal , Animales , Disponibilidad Biológica , Diabetes Mellitus Experimental/tratamiento farmacológico , Masculino , Mucosa Nasal/patología , Poliésteres/química , Alcohol Polivinílico/química , Ratas , Ratas Wistar , Estreptozocina

RESUMEN

PEGylated trimethyl chitosan (TMC) copolymers were synthesized in an attempt to both increase the solubility of chitosan in water, and improve the biocompatibility of TMC. A series of copolymers with different degrees of substitution were obtained by grafting activated poly(ethylene glycol)s (PEG) of different MW onto TMC via primary amino groups. Structure of the copolymers was characterized using 1H, 13C NMR spectroscopy and GPC. Solubility experiments demonstrated that PEG-g-TMC copolymers were completely water-soluble over the entire pH range of 1-14 regardless of the PEG MW, even when the graft density was as low as 10%. Using the methyl tetrazolium (MTT) assay, the effect of TMC molecular weight, PEGylation ratio, PEG and TMC molecular weight in the copolymers, and complexation with insulin on the cytotoxicity of TMC was examined, and IC50 values were calculated with L929 cell line. All polymers exhibited a time- and dose-dependent cytotoxic response that increased with molecular weight. PEGylation can decrease the cytotoxicity of TMC to a great extent in the case of low molecular weight TMCs. According to the cytotoxicity results, PEG 5 kDa is superior for PEGylation when compared to PEG 550 Da at similar graft ratios. Complexation with insulin further increased cell viability. In addition, Lactate dehydrogenase (LDH) assays were performed to quantify the membrane-damaging effects of the copolymers, which is in line with the conclusion drawn from MTT assay. Moreover, the safety of the copolymers was corroborated by observing the morphological change of the cells with inverted phase contrast microscopy. Based upon these results PEG-g-TMC merits further investigations as a drug delivery vehicle.

Asunto(s)

Materiales Biocompatibles/química , Quitosano/química , Portadores de Fármacos/química , Fibroblastos/citología , Fibroblastos/fisiología , Polietilenglicoles/química , Animales , Línea Celular , Difusión , Insulina/química , Ensayo de Materiales , Ratones , Solubilidad , Propiedades de Superficie , Agua/química

RESUMEN

Branched polyesters consisting of poly (vinyl alcohol) (PVA) grafted with chains of poly (lactic-co-glycolic acid) (PLGA) represent a new class of biodegradable polymers showing significant potential for the development of a variety of drug delivery vehicles. The amphiphilic character and the resulting increase in hydrophilicity of this class of polymers provide advantages when packaging sensitive drug molecules, such as proteins, peptides or DNA. Furthermore, the PVA backbone can be modified, for example, with sulfobutyl moieties or amine structures, to create polymers with negative or positive charges. The ability to modify not only the backbone but also the length of the PLGA side chains results in an extremely flexible polymer system, which can be adapted to meet the needs of almost any drug substance. Further, the rate of biodegradation may also be manipulated through polymer modification to achieve half-lives ranging from several hours to several weeks. This review provides an overview of the three major groups of branched polyesters based upon poly (vinyl alcohol)-grafted poly (lactic-co-glycolic acid) (PVA-g-PLGA), namely, the neutrally charged PVA-g-PLGA, the negatively charged sulfobutyl-modified PVA-g-PLGA and the positively charged amine-modified PVA-g-PLGA, as well as their use in various drug delivery systems.

Asunto(s)

Sistemas de Liberación de Medicamentos , Poliésteres/administración & dosificación , Ácido Láctico/administración & dosificación , Pulmón/metabolismo , Vehículos Farmacéuticos , Ácido Poliglicólico/administración & dosificación , Copolímero de Ácido Poliláctico-Ácido Poliglicólico , Polímeros/administración & dosificación , Alcohol Polivinílico/administración & dosificación , Proteínas/administración & dosificación , Toxoide Tetánico/administración & dosificación , Vacunas de ADN/administración & dosificación

RESUMEN

PURPOSE: The purpose of this study was the design of a polymeric platform for effective gene delivery using DNA-loaded nanoparticles. METHODS: The polymers were synthesized by carbonyldiimidazole (CDI)-mediated coupling of diamines diethylaminopropylamine (DEAPA), dimethylaminopropylamine (DMAPA) or diethylaminoethylamine (DEAEA) to poly(vinyl alcohol) (PVA) with subsequent grafting of D,L-lactide and glycolide (1:1) in the stoichiometric ratios of 1:10 and 1:20 (free hydroxyl groups/monomer units). The polymers were characterized by 1H-NMR, gel permeation chromatography-multiple-angle laser-light-scattering, and differential scanning calorimetry. DNA-loaded nanoparticles prepared by a modified solvent displacement method were characterized with regard to their zeta (zeta)-potential and size. The transfection efficiency was assessed with the plasmid DNA pCMV-luc in L929 mouse fibroblasts. RESULTS: The polymers were composed of highly branched, biodegradable cationic polyesters exhibiting amphiphilic properties. The amine modification enhanced the rapid polymer degradation and resulted in the interaction with DNA during particle preparation. The nanoparticles exhibited positive zeta-potentials up to +42 mV and high transfection efficiencies, comparable to polyethylenimine (PEI) 25 kDa/DNA complexes at a nitrogen to phosphate ratio of 5. CONCLUSIONS: The polymers combined amine-functions and short poly(D,L-lactic-co-glycolic acid) (PLGA) chains resulting in water-insoluble polymers capable of forming biodegradable DNA nanoparticles through coulombic interactions and polyester precipitation in aqueous medium. The high transfection efficiency was based on fast polymer degradation and the conservation of DNA bioactivity.

Asunto(s)

Péptidos Catiónicos Antimicrobianos/clasificación , ADN/administración & dosificación , Diseño de Fármacos , Técnicas de Transferencia de Gen , Nanotecnología/métodos , Animales , Péptidos Catiónicos Antimicrobianos/química , Péptidos Catiónicos Antimicrobianos/metabolismo , Materiales Biocompatibles/administración & dosificación , Materiales Biocompatibles/síntesis química , Materiales Biocompatibles/metabolismo , Materiales Biocompatibles/farmacocinética , Cápsulas , Química Farmacéutica/métodos , ADN/genética , ADN/farmacocinética , Fibroblastos/efectos de los fármacos , Fibroblastos/metabolismo , Alemania , Ácido Láctico/administración & dosificación , Ácido Láctico/síntesis química , Ácido Láctico/farmacocinética , Ratones , Tamaño de la Partícula , Plásmidos/genética , Poliésteres/química , Poliésteres/clasificación , Poliésteres/metabolismo , Ácido Poliglicólico/administración & dosificación , Ácido Poliglicólico/síntesis química , Ácido Poliglicólico/farmacocinética , Copolímero de Ácido Poliláctico-Ácido Poliglicólico , Polímeros/administración & dosificación , Polímeros/síntesis química , Polímeros/farmacocinética

RESUMEN

Nanoparticles may be effective drug delivery systems for use in various pulmonary therapeutic schemes. This study investigated the effect of nebulization technology and nanoparticle characteristics on the features of aerosol generation. Suspensions of biodegradable nanoparticles consisting of commercially available poly(lactide-co-glycolide) and novel comb polymers were nebulized with a jet, ultrasonic, and piezo-electric crystal nebulizer. The effects of the nanoparticle suspensions on the aerosol droplet size, as well as the nanoparticle size before and after nebulization, were characterized via laser diffraction. While the individual nanoparticle suspensions showed no clinically relevant influence on aerosol droplet size, as compared to control experiments, an enhanced nanoparticle aggregation within the droplets was observed. This aggregation was further characterized by fluorescence and scanning electron microscopy. Dependency of aggregation on nebulizer technology and nanoparticle characteristics was noted. Nanoparticles exhibiting the highest surface hydrophobicity were particularly susceptible to aggregation when nebulized with a jet nebulizer. Aggregation was reduced with nanoparticles exhibiting a more hydrophilic surface or when using ultrasonic nebulizers. We conclude that the biodegradable nanoparticles contained in the suspensions did not affect the aerosol droplet size in a clinically relevant manner; however, both the nanoparticle characteristics and the technique of aerosol generation influence nanoparticle aggregation occurring during aerosolization.

Asunto(s)

Aerosoles/química , Nanotecnología/métodos , Nebulizadores y Vaporizadores/estadística & datos numéricos , Microesferas , Nanotecnología/estadística & datos numéricos , Nebulizadores y Vaporizadores/normas