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Chitosan of high molar mass and with 82% deacetylation was sulfated using two procedures and characterized. In the first method sample chitosan-S1 was produced using chlorosulfonic acid as the sulfating agent and N,N-dimethylformamide as the medium, and in the second method (chitosan-S2) formic acid was also used. The degrees of sulfation were 0.87 (chitosan-S1) and 0.67 (chitosan-S2). FTIR spectra showed bands at 1230, 800 and 580 cm(-1), attributed to sulfation. Moisture content followed the order: chitosan-S-0.87>chitosan-S-0.67>chitosan. Chain depolymerization was verified by GPC. Aqueous solutions showed pseudoplastic behavior and the viscosity at a concentration of 0.3% (w/v) was higher than that of healthy human tears (close to 3 mPas at shear rate 130 s(-1)). Substitutions in the C2NH and in C6OH groups were verified by NMR. Antimicrobial activity against Staphylococcus aureus and Pseudomonas aeruginosa was not observed. Considering that chitosan-S-0.67 had a higher solubility, less chain depolymerization, higher yield and better thermal stability in comparison with chitosan-S-0.87, the derivative with DS 0.67 offered the greatest potential for use in formulations of tear substitutes.

Recebido em 11/12/09; aceito em 4/5/10; publicado na web em 21/9/10 OPHTALMIC VISCOSURGICAL DEVICES: COMPARISON BETWEEN COMMERCIAL AND FORMULATIONS BASED ON Dimorphandra gardneriana GALACTOMANNAN. Ophthalmic viscosurgical devices (OVD) are materials injected in intraocular space during cataract removal to reduce trauma in the patient's eye. Three Brazilian commercially available OVDs (Medilon Ò , Metilcelulose ® and Ofthyal ® ) were evaluated as well as formulations based on Dimorphandra gardneriana galactomannan. Viscosity and viscoelastic parameters, such as viscosity at zero shear, pseudoplasticity index, elastic and viscous moduli, relaxation time, were determined and compared. Characteristics of an effective OVD were proposed. None of the Brazilian devices studied fulfill the rheological requirements. Only the galactomannan at 3% concentration showed potential to be used as effective OVD.Keywords: fava danta rheology; ophthalmic viscosurgical device; cataract. INTRODUÇÃOA catarata é um distúrbio ocular caracterizado pela opacificação parcial ou total do cristalino. Esse distúrbio é a principal causa mundial de cegueira, sendo responsável por 48% dos casos de incapacidade visual.1 No Brasil, a situação é semelhante, sendo a catarata responsável por 40-50% das causas de cegueira em adultos.2 Com o aumento da expectativa de vida e o consequente incremento na população de idosos, prevê-se um aumento de casos. 3A extração do cristalino cataratoso e o implante de uma lente intraocular artificial são altamente eficientes para corrigir o distúrbio visual. A facoemulsificação é a técnica cirúrgica atualmente utilizada pela maioria dos cirurgiões para a remoção da catarata. 4 Ela consiste na fragmentação ultrassônica e emulsificação do núcleo do cristalino opacificado, preservando-se a sua cápsula, mediante uma incisão corneana mínima. Para facilitar o procedimento, substâncias viscoelásticas, conhecidas como dispositivos viscocirúrgicos oftálmicos (ophthalmic viscosurgical device, OVD), são injetadas na câmara anterior do olho. Após a facoemulsificação do núcleo, realiza-se a aspiração do material cortical. Em seguida, implanta-se uma lente intraocular na bolsa formada pela cápsula remanescente do cristalino. Por fim, efetua-se a remoção do fluido viscoelástico injetado. 5,6 Assim, as principais finalidades dos OVDs são auxiliar na manutenção da câmara anterior durante o procedimento cirúrgico, facilitando as manobras operatórias, e proteger os tecidos oculares, sobretudo as células endoteliais da córnea, dos danos causados pelo processo de facoemulsificação. 6Importantes características dos OVDs, adequadas às diferentes etapas do processo cirúrgico são de natureza reológica. Os parâmetros mais significativos são: viscosidade a cisalhamento zero, h 0 , pseudoplasticidade, propriedades viscoelásticas e tempo de relaxação.7 A habilidade do OVD de manter o espaço quando o tecido ocular estiver em repouso é refletida pelo h 0 . A resistência oferecida pelo OVD ao movimento normal dos instrumentos cirúrgicos no olho depe...

Nanomaterials can play an important role in antibacterial applications. Various nanostructured metallic particles have been used for nanocomposite packaging materials. Silver nanoparticles (AgNPs) are regarded as an antibacterial agent for food package. The objective of this study was to prepare antimicrobial nanocomposite films using gelatin and AgNPS. Gelatin was used as a polymer matrix for reduction and stabilization of the silver nanoparticles. Films were characterized by XRD, XRF, UV-Vis, FTIR, and antibacterial activity. Gelatin (3.0 g) was stirred at ~90 °C for 30 min. The pH of the solutions was adjusted to pH 11, then 1 mL of AgNO 3 at various concentrations (0, 45, 90, and 180 mmol.L-1) was added drop-wise into the solution mixtures. The neat gelatin (gel) and gel/AgNPs 45 mmol.L-1 films did not show any UV-Vis absorption peak in ~430 nm, but gel/AgNP 90 mmol.L-1 and gel/180 mmol.L-1 films exhibited a high absorption peak, which is related to the collective oscillations of the surface electrons. All FTIR peaks of the gel control and of the gel/AgNP show similar spectrum. The higher AgNPs concentration in the films, the higher the antibacterial activity against food-borne pathogens. The X-ray diffractograms of films was carried out for identifying crystalline phases by PANalytical X'pert High-Score Plus software, in which, showed the presence the peaks position (2) at 32.2°, 54.7°, 55.5° and 74.6° to gel/AgNPs 90 mmol.L-1 and 11.7°, 28.5°, 50.5° to 180 mmol.L-1 for silver. But wasn´t possible identify to gel/AgNPs 45 mmol.L-1 , because the low concentration. Was possible to produce crystalline silver nanoparticles in the gelatin films and obtain films with antimicrobial activity.