Cicatrização da musculatura reto-abdominal em coelhos submetidos à laparorrafia com fios de sutura à base de quitosana, categute cromado e poliglactina 910 / [Healing of the rectus abdominis muscle in rabbits submitted to laparorrhaphy with suture-based chitosan, chromic catgut and polyglactin 910]

Objetivou-se, com este estudo, avaliar o processo de cicatrização da musculatura reto-abdominal em coelhos submetidos à laparorrafia, utilizando-se o fio de sutura à base de quitosana, comparando-o aos fios de categute cromado e poliglactina 910. Foram utilizados 24 coelhos adultos, divididos aleatoriamente em quatro grupos: quitosana e categute 15 dias (QC-15dias), quitosana e categute 30 dias (QC-30 dias), quitosana e poliglactina 910 15 dias (QP-15 dias) e quitosana e poliglactina 910 30 dias (QP-30 dias). Cada grupo foi composto por seis coelhos, nos quais foram realizadas duas incisões, uma do lado direito e outra do lado esquerdo e, posteriormente, a laparorrafia, com o fio de quitosana de um lado e o categute cromado ou poliglactina 910 do outro. Realizou-se análise clínico-cirúrgica, histológica e avaliação de achados de necropsia, além de testes de citotoxicidade e de mecânica no fio de quitosana. Ele apresentou baixa resistência mecânica e citotóxica. O fio de quitosana não proporcionou uma cicatrização satisfatória em coelhos, pois desencadeou uma resposta inflamatória acentuada.(AU)

The objective of this study was to evaluate the healing process of the recto-abdominal muscles in rabbits submitted to laparorrhaphy using chitosan-based suture yarn, comparing it to chrome catgut and polyglactin 910 yarns. Twenty-four adult rabbits were divided in to four random groups: chitosan and polyglactin 910 15 days (QP-15 days) and chitosan and polyglactin 910 30 days (QC-30 days), chitosan and polyglactin 910 15 days (QP-15 days) QP-30 days). Each group consisted of six rabbits, in which two incisions were made, one on the right side and one on the left side, and later the laparorraphy with the chitosan yarn on one side and chromed catgut or polyglactin 910 on the other. Clinical-surgical, histological and necropsy findings were evaluated, as well as cytotoxicity and mechanical tests on the chitosan wire. It presented low mechanical and cytotoxic resistance. Chitosan thread did not provide satisfactory healing in rabbits, as it triggered a marked inflammatory response.(AU)

Small angle neutron scattering studies on the internal structure of poly(lactide-co-glycolide)-block-poly(ethylene glycol) nanoparticles as drug delivery vehicles.

Poly(lactide-co-glycolide)-block-poly(ethylene glycol) (PLGA-PEG) nanoparticles are commonly used as drug carriers in controlled drug release and targeting. To achieve predictable and clinically relevant volumes of drug distribution, nanoparticle size, surface charge, and especially composition and structure must be controlled. Understanding the internal structures within the particles is fundamentally important to explain differences in drug loading and variations in drug release rate. We prepared nanoparticles from ester-terminated PLGA-PEG polymers via nanoprecipitation, and studied the effects of altering the solvent-water miscibility (THF, acetone, and acetonitrile). Morphology, size, polydispersity, and ζ-potential of PLGA-PEG nanoparticles were characterized. Small angle neutron scattering measurements and fitted models revealed the internal nanoparticle structure: PLGA blocks of 7-9 nm are encapsulated inside a fairly dense PEG/water network in a fractal geometry. Particles with a larger PLGA block volume and higher PEG volume fraction in the particle interior result in greater retention of the hydrophilic anticancer drug carboplatin.

Sondas biodegradables para la prevención de las fístulas de hipospadias. Estudio preliminar experimental / Biodegradable catheters for fistula prevention in hypospadias. Experimental preliminary study

INTRODUCCIÓN: Las continuas innovaciones técnicas no acaban de solucionar la alta incidencia de fístulas tras la reparación del hipospa-dias. Una sonda-tutor hecha de un biomaterial polimérico reabsorbible (BPR) que pudiera dejarse in situ el tiempo suficiente podría disminuir las complicaciones.Objetivo. Investigar en un modelo animal diferentes BPR para su uso en urología.Material y métodos. Ratas Wistar macho (N= 45) divididas en 5 grupos en función de los polímeros empleados: polilactida; copolímero láctico-coprolactona; copolímero láctico-glicólico; simulado; control de silicona. Se sacrificaron 3 individuos por grupo a las 4, 10 y 16 semanas. A todos los animales (excepto al grupo simulado) se les fijó el material a la pared vesical por laparotomía. Los animales perma-necieron en alojamiento individual, con control diario de hematuria y control semanal de peso y de orina para pH y lactato. Al sacrificio, se recogió el material remanente para estudio químico y tejido vesical para valoración histológica.Resultados. No hubo mortalidad, hematuria ni otros signos clí-nicos. La pared vesical presentó una leve reacción a cuerpo extraño. Los valores de pH y lactato en orina no alcanzaron niveles tóxicos. El láctico-glicólico se reabsorbió totalmente a la 10ª semana y el polilactida y el láctico-coprolactona permanecieron íntegros. El polilactida tuvo alto grado de calcificaciones a partir de la 16ª semana.Conclusiones. Este modelo ha demostrado su utilidad para el es-tudio de la degradación del BPR. Los polímeros estudiados tardan de-masiado tiempo en reabsorberse por lo que habrá que investigar nuevos compuestos

INTRODUCTION: Continuous technical innovations are not enough to resolve the high incidence of fistula after hypospadias repair. A urethral catheter-tutor made of reabsorbable polymeric biomaterial (RPB) which could be left in situ long enough could reduce the complications.Target. To investigate in an animal model differents RPB to be used in urology.Methodology. CRL Wistar rats, males, divided into 5 equal groups according to the used polymers: polylactide; lactic-coprolactone co-polymer; lactic-glycolic copolymer; simulated; control silicones. Three individuals were sacrificed per group at 4th, 10th and 16th week. In all animals (exceptuating the simulated group), biomaterial was fixed to the bladder wall by laparotomy. Animals remained in individual hous-ing and kept under daily control of hematuria during the first 15 days and weekly weight and urine control for pH and lactate. After being slaughtered, remaining polymer was collected for chemical analysis and bladder tissue for hystologic study.Results. There was no mortality, hematuria nor other clinical signs. The bladder wall showed a mild foreign body reaction. The values of lactate and pH in urine did not reach toxic levels. Lactic-glycolic was totally reabsorbed by the 10th week and had the lowest degree of calci-fication. Polylactide and lactic-coprolactone remained intact.Conclusion. The model of urinary bladder has proven useful for studying the degradation of bioresorbable polymers. The analyzed poly-mers have spent long time to be reabsorbed, so we will have to study new others

Thermal Characterizations of silver-containing bioactive glass-coated Sutures.

This study utilized and compared a number of thermal analysis methods to characterize the thermal properties of commercial sutures with and without antimicrobial coatings of silver-doped bioactive glass (AgBG) interlocking particulates. The effect of a slurry dipping technique used to coat resorbable Vicryl (polyglactin 910) and non-resorbable Mersilk surgical sutures with AgBG was investigated using conventional differential scanning calorimetry (DSC), high speed calorimetry (or HYPERDSC), and modulated temperature DSC (MTDSC). These methods were compared in terms of their ability to resolve the thermal transitions of the types of suture materials. Differential thermal analysis (DTA) and thermogravimetric analysis (TGA) were used to verify the thermal degradation temperatures of these materials and to quantify the AgBG coatings on the sutures. The use of complementary thermal analysis techniques enabled the understanding of the effect of the AgBG coating technique on the morphological properties of the sutures. The slurry dipping technique had no significant effect on the thermal transitions of both types of materials. The use of high speed calorimetry through DSC offered better resolution for the transitions that appeared to be weak through conventional heating regimes, and was able to separate broad double transitions. Furthermore, it was shown not to compromise either the melting temperature or the enthalpy of melting. Therefore this method allows for the accurate determination of thermal transitions through much shorter experimental times thus allowing for an increased sample throughput. The combined DTA and TGA indicated that a greater AgBG coating was obtained in the case of the Mersilk sutures.

Carbon dioxide extraction of residual solvents in poly(lactide-co-glycolide) microparticles.

A process for the reduction of residual solvents in spray-dried poly(lactide-co-glycolide) (PLGA)-darbepoetin alfa microparticles was developed using carbon dioxide (CO(2)) as an extraction solvent. CO(2) was investigated in two phase states, liquid and gas. Detrimental effects on encapsulated protein integrity and microparticle morphology were observed with liquid CO(2) exposure. Extraction with CO(2) gas at <100 psig reduced residual solvent concentration and particle agglomeration was limited. Extraction rates and particle agglomeration increased with higher CO(2) gas pressures. The CO(2) pressures below which particles of polylactide (PLA) and PLGA microparticles significantly agglomerated were determined and the data used to develop extraction cycles. Extraction cycles were developed in which CO(2) gas pressure was increased as residual solvent concentration decreased in order to keep extraction rates high throughout the cycle. Spray dried darbepoetin alfa-PLGA microparticles were extracted with CO(2) gas and characterized for residual solvent concentration, process yield, particle size distribution, morphology, and protein integrity. The results indicated CO(2) gas may be used to reduce residual solvent to approximately 200 ppm with no significant detrimental effects on protein integrity or microparticle morphology.

Determination of copolymer ratios of poly(lactide-co-glycolide) using near-infrared spectroscopy.

The near infrared (NIR) spectroscopic technique was used to determine copolymer ratios of polylactide-co-glycolide samples. Appropriate quantities of DL-polylactic acid and lactic-co-glycolic acid polymers with 86:14, 75:25, 64:36 and 52:48 lactide to glycolide ratios were dissolved in methylene chloride to obtain 5% (w/w) solutions. NIR spectra of the samples were obtained from the solutions using a Polyol Analyzer operated in the transmittance mode. Linear regression calibration models were generated at 2130 and 2288 nm from the second derivative spectral data obtained from the NIR technique. The lowest and highest standard errors of calibration (SEC) at 2130 nm were 1.29 and 1.63%, whereas those obtained from the calibration models generated at 2288 nm were 2.00 and 2.03%, respectively. Partial least squares (PLS) calibration models were also generated from the second derivative spectral data from 1100 to 2500 nm. The lowest and the highest SEC for the models were 1.46 and 1.53%, respectively. The calibration models were then used to predict the lactide contents of the unknown (test) samples. The highest percent error of prediction was 2.56% for samples with 86% lactide content when the linear regression calibration at 2130 nm was used, whereas the highest percent error of prediction was 1.56% for samples with 64% lactide content when the linear regression calibration at 2288 nm was used. The highest percent error of prediction was 1.73% for samples with 75% lactide content when the two-factor PLS calibration model was used.

Estudo comparativo da resposta tecidual frente a fios de sutura de poliglactina 910 e poliglecaprone em subcutâneo de ratos / Comparative study of tissue response to polyglactin 910 and polyglecapron 25 suture materials in rats

Avaliou-se a resposta tecidual, em regiäo subcutânea de ratos, frente a fios de sutura: poliglactina 910 e poliglecaprone. Para tanto foram utilizados 20 ratos albinos, nos quais praticaram-se dois pontos de sutura em planos profundos na regiäo dorsal, com os dois diferentes materiais. Após períodos de 1, 2, 7, e 10 dias, grupos de cinco animais foram sacrificados para obtençäo de espécimes que foram processados e corados pela hematoxilina e eosina. Após análise dos resultados histológicos pôde-se verificar uma resposta tecidual mais favorável ao fio de poliglecaprone 25 com menor fase exsudativa e mais precoce proliferaçäo celular

Estudo comparativo da resposta tecidual frente a fios de sutura de catgut, poliglactina 910 e poliglecaprone 25 em tecido subcutâneo de ratos / Comparative study of tissue ensver front of sutura of catgut, poliglactina 910 and poliglecaprone 25 in subcutaneous tissues in rats

Avaliou-se a resposta tecidual na regiäo subcutânea de ratos frente aos fios de sutura: catgut, poliglactina 910 e poliglecaprone 25. Para tanto foram utilizados 20 ratos albinos, nos quais praticaram-se três pontos de sutura em planos profundos na regiäo dorsal com os três diferentes materiais. Após períodos de 1, 2, 7 e 10 dias, grupos de cinco animais foram sacrificados para obtençäo de espécimes que foram processados e corados pela hematoxilina e eosina. Após a análise dos resultados histológicos pode-se verificar uma resposta tecidual mais favorável aos fios sintéticos que ao catgut, com menor fase exsudativa e mais precoce proliferaçäo celular. Entre estes, o fio de poliglecaprone permitiu uma melhor organizaçäo do tecido conjuntivo circunvizinho, com menor infiltrado inflamatório

High-performance liquid chromatographic determination of some of the hydrolytic decomposition products of poly(alpha-hydroxyacid)s.

An HPLC procedure is described for the separation and identification of some hydrosoluble by-products resulting from the hydrolytic degradation of poly(alpha-hydroxyacid)s having biomedical interest: poly(L-lactide), poly(DL-lactide), poly-(glycolide) and poly(lactide-co-glycolide). Peak identification was performed by comparing the respective retention times with those of pure standards. It was observed that optimum shape and separation of peaks are considerably affected by the composition of the mobile phase, consisting of acetonitrile (A) and a 0.006 M K2HPO4 buffer (B), and, in particular, its pH and A:B ratio, which had to be adjusted to around 5.8 and 75:25 (v/v), respectively. Under the investigated experimental conditions (aqueous suspension, 100 degrees C for 12 h under stirring), poly(L-lactide) is quite stable, poly(glycolide) degrades easily to glycolic acid, whereas poly(DL-lactide) and poly(DL-lactide-co-glycolide) exhibit intermediate behaviour. Upon hydrolytic decomposition, these poly(alpha-hydroxyacid)s yield not only the corresponding acids, but also their linear dimers and, possibly, trimers, tetramers and higher oligomers.

Anticoagulant hydrogels derived from crosslinked dextran. Part I: Synthesis, characterization and antithrombic activity.

Hydrogels have been prepared by binding various amino acids to Sephadex derivatives bearing carboxymethyl and sulphonated benzylamide groups. Depending on the chemical nature and content of the amino acid substituent, these insoluble strongly hydrophilic materials may absorb 7 to 19 volumes of buffer per volume of dry material. These hydrogels present antithrombic activity in relation to their swelling ratio. The adsorption of thrombin might partially explain the anticoagulant effect as shown by the evaluated affinity constants between the hydrogels and the enzyme i.e. 1 to 2 X 10(6) I/M.

Observações clínicas sobre o emprego de poliglactina 910 (Polyvicryl) em suturas intrabucais

São tecidas considerações sobre o emprego do fio de poliglactina 910 (Polyvicryl) em suturas de alguns casos de apicectomias, extração de retidos, biópsias e fechamento de comunicação buco-sinusal. As observações clínicas evidenciam tratar-se de um fio adequado para suturas intrabucais