Immobilization of Aspergillus niger lipase on chitosan-coated magnetic nanoparticles using two covalent-binding methods.

Aspergillus niger lipase immobilization by covalent binding on chitosan-coated magnetic nanoparticles (CMNP), obtained by one-step co-precipitation, was studied. Hydroxyl and amino groups of support were activated using glycidol and glutaraldehyde, respectively. Fourier transform infrared spectrometry, high-resolution transmission electron microscopy and thermogravimetric analysis confirmed reaction of these coupling agents with the enzyme and achievement of a successful immobilization. The derivatives showed activities of 309.5 ± 2.0 and 266.2 ± 2.8 U (g support)(-1) for the CMNP treated with glutaraldehyde and with glycidol, respectively. Immobilization enhanced the enzyme stability against changes of pH and temperature, compared to free lipase. Furthermore, the kinetic parameters K m and V max were determined for the free and immobilized enzyme. K m value quantified for enzyme immobilized by means of glutaraldehyde was 1.7 times lowers than for free lipase. High storage stability during 50 days was observed in the immobilized derivatives. Finally, immobilized derivatives retained above 80% of their initial activity after 15 hydrolytic cycles. The immobilized enzyme can be applied in various biotechnological processes involving magnetic separation.

Multivariate Optimization of Electrochemical Biosensors for the Determination of Compounds Related to Food Safety-A Review.

We summarize the application of multivariate optimization for the construction of electrochemical biosensors. The introduction provides an overview of electrochemical biosensing, which is classified into catalytic-based and affinity-based biosensors, and discusses the most recent published works in each category. We then explore the relevance of electrochemical biosensors for food safety analysis, taking into account analytes of different natures. Then, we describe the chemometrics tools used in the construction of electrochemical sensors/biosensors and provide examples from the literature. Finally, we carefully discuss the construction of electrochemical biosensors based on design of experiments, including the advantages, disadvantages, and future perspectives of using multivariate optimization in this field. The discussion section offers a comprehensive analysis of these topics.

Estudio prospectivo del uso de heparina intraocular: en cirugía reconstructiva y aceite de silicona / Prospective study of the use of intraocular heparin in vitreoretinal surgery and silicone oil

Los autores reportan los resultados de un estudio prospectivo sobre el uso de la heparina intraocular como agente antiproliferativo en cirugía vitreorretiniana y aceite de silicona, realizado en 51 pacientes (ojos), intervenidos en la Fundación Oftalmológica Nacional de Bogotá, Colombia, entre 1990 y 1992. Se realiza una comparación entre el grupo heparina y un grupo control en cuanto a la agudeza visual, seguimiento, reintervenciones, intervalo entre cirugías, éxito anatómico y complicaciones. No encontramos una diferencia estadísticamente significativa