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ABSTRACT: Polysaccharides have shown ideal features for their application in nanomedicine as nanoparticulated systems. Nanoparticles based on mixtures of alginate and chitosan (A/Q-50/50, formed by 50% alginate and 50% chitosan, and A/Q-70/30, formed by 70% alginate and 30% alginate) have been synthesised by an emulsification method and stabilised by amide bond formation. Tamoxifen (TMX) was loaded into these systems, and they were assayed as controlled delivery formulations. Results showed the formation of spherical nanoparticles with very small size (19-28 nm). The presence of amide bonds was determined by FT-IR and confirmed by Thermogravimetric analysis studies. TMX incorporation was achieved successfully (2-3 µg TMX per mg NP), and maximum TMX release took place between 8 and 24 h. This study shows that interaction between TMX and the system was dependent on nanoparticle composition, being the composition with higher proportion of alginate the one which showed the best release control of the drug.
Journal of Microencapsulation 03/2013; · 1.55 Impact Factor
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ABSTRACT: Tamoxifen (TMX) is the most common clinical choice for the treatment of advanced or metastatic estrogen-dependent breast cancer. However, research on new challenging therapies is necessary due to its undesirable side effects and the limitation of the treatment only to the oral route. In this study, the antitumor activity of TMX-loaded nanoparticles based on different mixtures of alginate-cysteine and disulfide bond reduced bovine serum albumin was tested in vivo in MCF-7 nude mice xenograft model. These systems showed an enhancement of the TMX antitumor activity, since lower tumor evolutions and lower tumor growth rates were observed in mice treated with them. Moreover, histological and immunohistochemical studies revealed that treatments with TMX-loaded nanoparticles showed the most regressive and less proliferative tumor tissues. TMX biodistribution studies determined that TMX-loaded nanoparticles caused more accumulation of the drug into the tumor site with undetectable levels of TMX in plasma, reducing the possibility of delivering TMX to other not-targeted organs and, consequently, developing possible side effects. Thus, these TMX nanoparticulate systems are expected to provide a novel approach to the treatment of breast cancer in the future.
International journal of pharmaceutics 07/2012; 436(1-2):574-81. · 2.96 Impact Factor
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ABSTRACT: Nanoparticles based on disulfide bond reduced bovine serum albumin and thiolated alginate (alginate-cysteine conjugate) have been prepared by coacervation method and have been loaded with tamoxifen (TMX). The TMX load into the nanoparticles was optimized (4-6 μg/mg NP) by freeze-drying the systems before the loading procedure. Maximum TMX release (45-52%) took place between 2 and 25 h. Cytotoxicity of unloaded nanoparticles in MCF-7 and HeLa cells was not observed, although a small decrease in viability took place at very high concentration. Cell uptake of nanoparticles occurred in both cell types and the presence of polysaccharide in the nanoparticle composition allowed a better interaction with cells. The administration of 10 μM TMX by TMX-nanoparticles was effective in both cellular lines, and the effect of the drug-loaded systems on MCF-7 cell cycle showed the efficacy of the TMX-loaded nanoparticles.
Journal of Biomedical Materials Research Part A 03/2012; 100(6):1467-76. · 2.63 Impact Factor
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ABSTRACT: Paclitaxel (PTX), an antimicrotubular agent used in the treatment of ovarian and breast cancer, was encapsulated in nanoparticles (NPs) of poly(lactide-co-glycolide) (PLGA) and poly(ε-caprolactone) (PCL) polymers using the spray-drying technique. Morphology, size distribution, drug encapsulation efficiency, thermal degradation and drug release were characterized. MCF7 cells were employed to evaluate the efficacy of the systems on cell cycle and cytotoxicity. The particle size was in the range 0.8-1 µm. The incorporation efficiency of PTX was more than 80% in all NPs obtained. In vitro drug release took place during 35 days, and drug release rates were in the order PCL > PLGA 50:50 > PLGA 75:25. Unloaded NPs showed to be cytocompatible at MCF7 cells. PTX-loaded NPs demonstrated the release of the drug block cells in the G2/M phase. All PTX-loaded formulations showed their efficacy in killing MCF7 cells, mainly PTX-loaded PLGA 50:50 and PLGA 75:25 that cause a decrease in cell viability lower than 20%.
Journal of Microencapsulation 01/2011; 28(5):417-29. · 1.55 Impact Factor
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ABSTRACT: The interaction between nickel and yeast hexokinase was studied. The binding of nickel showed a positive cooperativity, and saturation was not reached. The nickel binding induced modifications in the secondary structure of the protein; thus, a lost of alpha helix and beta turns, as well as an increase of the random structure and beta sheet was observed. The monomer/dimmer equilibrium of the protein was modified in the presence of nickel, and the monomer state was mainly obtained at the highest nickel concentrations studied. These changes on the protein structure caused a decrease in the enzyme activity. According to kinetic studies, nickel caused a non-competitive inhibition when glucose was the variable substrate and a linear competitive inhibition when ATP was the variable substrate.
Journal of Inorganic Biochemistry 01/2006; 99(12):2395-402. · 3.35 Impact Factor
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ABSTRACT: 5-Fluorouracil (5-FU), a hydrosoluble anti-neoplastic drug, was encapsulated in microspheres of poly(D,L-lactide) (PLA) and poly(lactide-co-glycolide) (PLGA) polymers using the spray-drying technique, in order to obtain small size microspheres with a significant drug entrapment efficiency. Drug-loaded microspheres included between 47 +/- 11 and 67 +/- 12 microg 5-FU mg(-1) microspheres and the percentage of entrapment efficiency was between 52 +/- 12 and 74 +/- 13. Microspheres were of small size (average diameter: 0.9 +/- 0.4-1.4 +/- 0.8 microm microspheres without drug; 1.1 +/- 0.5-1.7 +/- 0.9 microm 5-FU-loaded microspheres) and their surface was smooth and slightly porous, some hollows or deformations were observed in microspheres prepared from polymers with larger Tg. A fractionation process of the raw polymer during the formation of microspheres was observed as an increase of the average molecular weight and also of Tg of the polymer of the microspheres. The presence of 5-FU did not modify the Tg values of the microspheres. Significant interactions between the drug and each one of the polymers did not take place and total release of the included drug was observed in all cases. The time needed for the total drug release (28-129 h) was in the order PLA > PLGA 75/25 > PLGA 50/50. A burst effect (17-20%) was observed during the first hour and then a period of constant release rate (3.52 +/- 0.82-1.46 +/- 0.26 microg 5-FU h(-1) per milligram of microspheres) up to 8 or 13 h, depending on the polymer, was obtained.
Journal of Microencapsulation 09/2005; 22(6):671-82. · 1.55 Impact Factor
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ABSTRACT: Cytarabine (ara-C) was included in albumin microspheres and these microspheres were immersed in a poly(lactide-co-glycolide) (PLGA) film to constitute a comatrix system to develop a prolonged form of release. Cytarabine-loaded albumin microspheres were synthesized by emulsion, and 25 or 50 mg of drug were included in the disperse phase. Thus, microspheres with 46+/-4 microg drug/mg microspheres and 50+/-5 microg drug/mg microspheres were obtained, which means a percentage of incorporation efficiency of 42+/-4% and 25+/-2%, respectively. These cytarabine-loaded microspheres were used to prepare PLGA-comatrices. Kinetic release studies indicated that total cytarabine release only takes place in the presence of protease, probably due to the fact that glutaraldehyde establishes covalent links with the amine side group of the drug and cross-links it with the protein matrix. A slower kinetic release of the drug was obtained from PLGA-comatrices, although only 80% of the included cytarabine was released on day 7. The comatrices were subcutaneously implanted in the back of rats and in both cases the ara-C administered dose was 36 mg of ara-C per kg of body weight. The drug was detected in plasma 10 days. The mean residence time (MRT) of the drug administered by these comatrices was 87-91 times larger when compared to the value obtained when the drug was administered in solution by intraperitoneal injection. The histological studies show that a degradative process of the comatrices takes place. The comatrices do not damage surrounding tissue; a normal regeneration of the implanted zone was observed.
European Journal of Pharmaceutics and Biopharmaceutics 04/2004; 57(2):225-33. · 4.27 Impact Factor
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ABSTRACT: Chitosan beads loaded with bupivacaine (16+/-3 microg of drug per milligram of beads) were prepared by cross-linking with glutaraldehyde. In vitro drug release at pH and temperature conditions similar to those of the biological systems were studied. Maximum release of bupivacaine was obtained between 100 and 120 h, depending on the presence of lysozyme in the release medium, since the enzyme facilitates the release process. A constant release rate of the drug, between 11 and 15 microg/h, was observed for 30 h. In order to prolong bupivacaine release, the drug-loaded chitosan beads were coated with a poly(DL-lactide-co-glycolide) film. The resulting device allows the drug to be released in a sustained form; a constant release rate between 28.5 and 29.5 microg/h was obtained for 3 days, and the maximum release of bupivacaine took place at day 9. The in vitro results indicate a possible application of these bupivacaine loaded chitosan systems as drug release devices with an analgesic action. Thus, they could be used in the treatment of dental pain in the buccal cavity, where drug release would be made easier by lysozyme of the saliva.
Il Farmaco 12/2003; 58(11):1187-91.
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ABSTRACT: Bupivacaine, an amide local anaesthetic agent of long-acting and intense anaesthesia, was incorporated into poly(acrylamide(A)-co-monomethyl itaconate (MMI)) hydrogels. The swelling behaviour of two gel compositions, without drug, 75A/25MMI and 60A/40MMI, through rabbit ear skin, mounted on a modified Franz diffusion cell, was studied. Both gel compositions reach the equilibrium swelling degree (88.9+/-0.7 wt.% for 75A/25MMI and 92.5+/-0.1 wt.% for 60A/40MMI). The swelling kinetics was in accordance with the second Fick's Law; diffusion coefficients indicate faster swelling for gels with lower amount of monomethyl itaconic acid. The skin flux of bupivacaine solution through rabbit ear skin was 105+/-24 microg/cm(2)/h, the effective permeability coefficient was 26 x 10(-3)+/-9 x 10(-3)cm/h, and 77+/-15% of bupivacaine was permeated. Bupivacaine-loaded gels allow the drug was permeated through the skin. 47+/-4% and 36+/-3% of the drug amount included in 75A/25MMI and 60A/40MMI hydrogels, respectively, was permeated. The skin flux of the drug was between 90+/-5 and 16+/-7 microg/cm(2)/h depending on the amount of bupivacaine included in the gel and the gel composition. Skin flux increases with the drug load of the gels. Furthermore, as more MMI in the gel slower skin flux of the drug due to bupivacaine-gel interactions.
International Journal of Pharmaceutics 05/2003; 255(1-2):99-107. · 3.35 Impact Factor
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ABSTRACT: Poly(epsilon-caprolactone) microspheres containing bupivacaine were prepared by the spray-drying process. The average size of drug loaded microspheres was less than 3 microm in diameter, and the percentage of entrapment efficiency was 91 +/- 3%. In vitro drug release kinetic in phosphate buffer at 37 degrees C showed a hyperbolic profile, with a burst-effect during the first hour. Subcutaneous injection of bupivacaine-loaded microspheres in the back of rats caused an increase in drug concentration in plasma. Maximum bupivacaine concentration in plasma was 237 +/- 58 ng/ml at 105 h, and drug was detected in plasma for 16 days. The half-life time of the drug was increased by more than 125 times with regard to that of the drug administered in a solution by intraperitoneal injection. After 30 days of injection, a mass formed by microspheres surrounded by a thin fibrous capsule was observed. Small blood vessels and multinucleate foreign body giant cells with macrophagic function around microspheres were detected. After 60 days of injection a subcutaneous mass was also observed, which was formed of more degraded dispersed microspheres in conjunctive tissue, which had a normal structure. Thus, bupivacaine-loaded poly(epsilon-caprolactone) microspheres could be considered as a device to be used in the treatment of severe pain that is not responsive to opioids for example in cancer-related syndromes or in intractable herpetic neuralgia.
European Journal of Pharmaceutics and Biopharmaceutics 04/2003; 55(2):229-36. · 4.27 Impact Factor
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ABSTRACT: Copolymeric hydrogels of poly(acrylamide-co-monomethyl itaconate) (A/MMI) crosslinked with N,N′-methylenbisacrylamide (NBA) were synthesized as devices for the controlled release of bupivacaine (Bp). Two compositions of the copolymer, 60A/40MMI and 75A/25MMI, were studied. A local anesthetic was included in the feed mixture of polymerization (2–8 mg Bp/tablet) and by immersion of the copolymeric tablets in an aqueous solution of the drug. A very large amount of Bp (36–38 mg Bp/tablet) was included in the gels by sorption due to interactions between the drug and the side groups of the hydrogels. Swelling and drug release were in accordance with the second Fick's law at the first stages of the processes. The swelling behavior of these copolymers depended on the pH of the medium. The equilibrium swelling degree (W∞) was larger at pH 7.5 (W∞ ≈ 90 wt %) than at pH 1.5 (W∞ ≈ 52–64 wt %) due to the ionization of the side groups of the copolymer. Release of the drug also depended on the pH of the swelling medium; at pH 7.5, about 60% of the included drug was released, and at pH 1.5, about 80% was released. Bp release was controlled by the comonomer composition of the gels, their drug-load, and the pH of the swelling medium. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 327–334, 2002
Journal of Applied Polymer Science 07/2002; 86(2):327 - 334. · 1.29 Impact Factor
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ABSTRACT: The interaction between lead and yeast hexokinase has been studied. Lead provokes a large variation in the aggregation state of the protein, forming bigger structures of high molecular mass. This phenomenon is characterized by a small modification in the tridimensional structure and a great variation in the secondary structure. There is a loss in -helix which is compensated by an enhancement in β-sheet. The polypeptide chain is more stable in the β-sheet structure corresponding to the aggregate forms. During this change the enzyme maintains a high level of activity in the monomer and also in the aggregate form. This implies that the enzyme function is not greatly affected by the change, and active sites are retained without important modifications. According to kinetic measurements the ATP site is more affected than the glucose site. There is a mixed type inhibition with a main competitive component when glucose acts as a variable substrate.© 2001 Society of Chemical Industry
Polymer International 06/2001; 50(7):822 - 827. · 1.90 Impact Factor
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ABSTRACT: Structural variations of lysozyme as a consequence of its interaction with CdAc2, as well as the implications on the protein functionality have been studied. Variations in the conformation of the macromolecule are seen, however these changes are not reflected on the secondary structure. The interaction of the salt with the polypeptide chain is weak and thermodynamically unfavourable. Molecular aggregates (dimer forms) are observed at the highest salt concentrations. This interaction causes an inhibitory effect on lysozyme, the activity loss being 50% at the highest salt concentration studied. The inhibition is of mixed type with an uncompetitive component. Thus cadmium does not bind to the active site of the enzyme which is in accordance with the not very large activity loss observed. The substrate inhibition of lysozyme is favoured in the presence of the salt, so interaction with the macromolecule is at low affinity sites.
Journal of enzyme inhibition 02/2001; 16(1):65-80.
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ABSTRACT: Poly(2-hydroxyethyl methacrylate-co-acrylamide) hydrogels crosslinked with ethylen glycol dimethacrylate were used as devices for the in-vivo drug release of 5-fluorouracil (5-FU). Drug-loaded hydrogels were subcutaneously implanted in the back of Wistar rats. All hydrogel discs reached an equilibrium swelling degree, which was slightly larger than that determined in-vitro. After 30 days of implantation, the hydrogel discs were transparent, and without fracture or apparent degradation. In addition, a fibrous capsule was not detected around the hydrogels that had greater hydration degrees. Release of 5-FU from these hydrogels allows the drug to remain in the plasma from 1 to 5 days, in spite of its short plasma half-life (15 min). This was an improvement of up to 98-times compared with the intraperitoneal drug administration. Administration of 5-FU by implantation of 2-hydroxyethylmethacrylate-co-acrylamide copolymeric hydrogels seems to be a good candidate for 5-FU therapy, since the drug released results in a therapeutically suitable plasma concentration of 5-FU for an extended period of time, despite the short half-life of the drug.
Journal of Pharmacy and Pharmacology 12/2000; 52(11):1319-25. · 2.17 Impact Factor
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ABSTRACT: Cytarabine was included in chitosan microspheres and several of these microspheres were embedded in a poly(lactide-co-glycolide) (PLG) film to constitute a comatrix system, to develop a prolonged release form. Chitosan microspheres, in the range of 92+/-65 microm, having good spherical geometry and a smooth surface incorporating cytarabine, were prepared. The cytarabine amount included in chitosan microspheres was 43.7 microg of ara-C per milligram microsphere. The incorporation efficiency of the cytarabine in microspheres was 70.6%. Total cytarabine release from microspheres in vitro was detected at 48 h. Inclusion of cytarabine-loaded microspheres in poly(lactide-co-glycolide) film initiated a slower release of the drug and, in this way, the maximum of cytarabine released (80%) took place in vitro at 94.5 h. Comatrices, with 8.7 mg of cytarabine, signifying a dose of 34.5 microg/kg, were subcutaneously implanted in the back of rats. Maximum plasma cytarabine concentration was 18.5+/-1.5 microg/ml, 48 h after the device implantation and the drug was detected in plasma for 13 days. The histological studies show a slow degradative process. After 6 months of implantation, most of the microspheres of the matrix seemed to be intact, the comatrix appeared surrounded by conjunctive tissue and small blood vessels and nerve packets were detected in the periphery of the implant.
International Journal of Pharmaceutics 08/2000; 202(1-2):29-39. · 3.35 Impact Factor
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ABSTRACT: The aluminum and yeast hexokinase interaction was studied. Structural changes were correlated with variations in protein functionality. Results show two different behaviors: At low metal concentrations preferential adsorption of metal (and water exclusion) induces aggregate formation. No significant changes in the protein structure occur, but there is a continuous loss of activity (from the first concentration). At large salt concentrations a monomerization process and a conformational change in the secondary structure as well as in the three-dimensional structure take place. This change reduces the percentage of alpha-helix conformation, gives thermal stability to the protein, and allows the exposure of some tryptophan residue and hydrophobic regions. The protein inhibition increases. Conformational change and monomerization may allow access of the metal to the substrate site, mainly the ATP site. The inhibition in any case is of mixed type with a competitive component.
Journal of Protein Chemistry 05/2000; 19(3):199-208.
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ABSTRACT: Bupivacaine-loaded comatrix, formed by bupivacaine-loaded microspheres included in a poly(lactide-co-glycolide) film, was assayed for the controlled release of the drug 'in vivo'. The comatrix, with 66.37 microg of bupivacaine, signifying a dose of 265.5 microg/kg, was subcutaneously implanted in the back of rats. Maximum plasma bupivacaine concentration was 147.6 +/- 5.0 ng/ml 95 h after the device implantation, and the drug was detected in plasma for 17 days. The half-life time of bupivacaine improves by more than 50 times with regard to that of the drug administered in a solution by intraperitoneal injection. After 15 days of implantation the comatrix was included in a thin fibrous capsule and degradation of the microspheres was observed. The histological studies show good biocompatibility of this comatrix. After 50 days the comatrix was degraded and its remains were almost indistinguishable from the surrounding tissue. Small number of microspheres was observed and they were surrounded by conjunctive tissue. Nerve packets and small blood vessels were also observed in the periphery of the implant.
Biomaterials 11/1999; 20(20):1919-24. · 7.40 Impact Factor
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ABSTRACT: Poly(N-vinyl-2-pyrrolidone) (PVP) [2]/water [1]/VOSO4 [3] ternary system interactions have been studied by viscometric and densitometric techniques. Preferential water absorption inside the macromolecular coil and preferential salt interaction with the polymer external domain were observed. The unperturbed dimensions of the macromolecule increased with the salt concentration up to 75mM VOSO4, a point where the intrinsic viscosity was also a maximum and a conformational transition could be produced. The polymer– solvent interaction became worse with salt concentration and VOSO4 behaved as a salting-in agent for the polymer, the binary solvent mixture being thermodynamically unfavourable. © of SCI.
Polymer International 03/1999; 42(3):245 - 250. · 1.90 Impact Factor
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ABSTRACT: This study has tested the application of three different copolymeric poly(acrylamide-co-monoethyl itaconate; A/MEI) hydrogels, 90A/10MEI, 75A/25MEI and 60A/40MEI, on the release of cytarabine (ara-C). The drug was incorporated in gels by placing it in the polymerization feed mixture and discs loaded with 5-50 mg ara-C were obtained. The amount of swelling at equilibrium in saline solution (NaCl, 0.9% w/w) was between 78 and 82% w/w, depending on the composition of the copolymer. The diffusion studies followed Fick's second law. The diffusion coefficients for swelling of the gels were between 9.30 x 10(-11) m2 s(-1) and 37.42 x 10(-11) m2 s(-1); those for release of ara-C were between 3.42 x 10(-11) m2 s(-1) and 10.25 x 10(-11) m2 s(-1). The activation energies for swelling were in the range 16.60 +/- 2.59-21.85 +/- 1.78 kJ mol(-1); those for ara-C release were 28.13 +/- 3.1-29.7 +/- 4.6 kJ mo(-1). To determine the applicability of these copolymers, 75A/25MEI gel was subcutaneously implanted in rats and the plasma concentration of the drug was determined by high-performance liquid chromatography. The concentration of ara-C in plasma (range 17.67 +/- 5.68-10.76 +/- 2.15 microg mL(-1)) was maintained during the first stages (2-8 h) and no drug was detected after 32 h. This route of administration was compared with intraperitoneal injection of the drug. In conclusion, ara-C can be incorporated in hydrogels and released in a pharmacologically active form. The concentration of ara-C in plasma is maintained for long enough to improve therapeutic results.
Journal of Pharmacy and Pharmacology 08/1998; 50(7):703-12. · 2.17 Impact Factor
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ABSTRACT: The aim of this study is to examine the influence of crosslinking density on 5-Fluorouracil release from poly(2-hydroxyethyl
methacrylate) (PHEMA) hydrogels crosslinked with 1,1,1-trimethylolpropane trimethacrylate (TPT).
PHEMA hydrogels were synthesized by bulk polymerization with different proportions of TPT (1–10 wt%) as crosslinker agent
and ammonium persulphate as initiator, enabling polymerization in the feed mixture in the presence of water. As a result,
5-FU could be trapped by including it as a sodium salt in the feed mixture of polymerization. Discs with 5-FU loads between
1–16mg/disc were obtained.
Swelling and 5-FU release kinetics studies were carried out in saline solution at 310K. The diffusion studies were in accordance
with Fick’s second law during the initial stages, enabling the diffusion coefficients of the process to be determined. The
time required for discs to reach total 5-FU release was between 35h and 160h and was a function of crosslinking density of
the gels and 5-FU load of the discs.
Polymer Bulletin 04/1997; 38(1):55-62. · 1.53 Impact Factor
