Assembly of nitroreductase and layered double hydroxides toward functional biohybrid materials.

The development of new multifunctional materials integrating catalytically active and selective biomolecules, such as enzymes, as well as easily removable and robust inorganic supports that allow their use and reuse, is a subject of ongoing attention. In this work, the nitroreductase NfrA2/YncD (NR) from Bacillus megaterium Mes11 strain was successfully immobilized by adsorption and coprecipitation on layered double hydroxide (LDH) materials with different compositions (MgAl-LDH and ZnAl-LDH), particle sizes and morphologies, and using different enzyme/LDH mass ratios (Q). The materials were characterized and the immobilization and catalytic performance of the biohybrids were studied and optimized. The nitroreductase-immobilized on the nanosized MgAl-LDH displayed the best catalytic performance with 42-46% of catalytic retention and>80% of immobilization yield at saturation values of enzyme loading Cs ≈ 0.6 g NR/g LDH (Q = 0.8). The adsorption process displayed high enzyme-LDH affinity interactions yielding to a stable biohybrid material. The increase in the amount of enzyme loading favoured the catalytic performance of the biohybrid due to the better preservation of the native conformation. The biohybrid was reused several times with partial activity retention after 4 cycles. In addition, the biohybrid was successfully dried maintaining the catalytic activity for several weeks when it was stored in its dry form. Finally, thin films of NR@LDH biohybrid deposited on glassy carbon electrodes were evaluated as a modified electrode applied for nitro-compound detection. The results show that these biohybrids can be used in biotechnology applications to efficiently detect compounds such as dinitrotoluene. The search for new non-hazardous chemical designs preventing or reducing the use of aggressive chemical processes for human being and the environment is the common philosophy within sustainable chemistry.

Interactions between Biological Cells and Layered Double Hydroxides: Towards Functional Materials.

This review highlights the current research on the interactions between biological cells and Layered Double Hydroxides (LDH). The as-prepared biohybrid materials appear extremely attractive in diverse fields of application relating to health care, environment and energy production. We describe how thanks to the main features of biological cells and LDH layers, various strategies of assemblies can be carried out for constructing smart biofunctional materials. The interactions between the two components are described with a peculiar attention to the adsorption, biocompatibilization, LDH layer internalization, antifouling and antimicrobial properties. The most significant achievements including authors' results, involving biological cells and LDH assemblies in waste water treatment, bioremediation and bioenergy generation are specifically addressed.

Prevalência de lesões ateroscleróticas na artéria torácica interna esquerda, evidenciadas pelos achados de angiografia seletiva / Prevalenve of atherosclerotic lesions in the left internal thoracic artery, evidenced by selective angiographic findings

Background: By observing the high prevalence of failures in the surgical treatment of myocardial revascularization (MR), with the use of the Left Internal Thoracic Artery (LITA) as a graft, evidenced by the international literature, it was sought to demonstrate the prevalence of lesions that would not allow the use of LITA as a graft in myocardial revascularization surgery, with possible alteration in the surgical management performed by the cardiac surgeon, and reduction of the morbimortality of these patients. Objectives: To evaluate the prevalence of atherosclerotic lesions of the LITA, through selective preoperative angiography, in patients submitted to coronary angiography and indicated for myocardial revascularization. We also analyzed other lesions that made the use of LITA unfeasible as a main graft in cases of myocardial revascularization surgery (MRS). Methods: This was a cross-sectional, prevalence study that evaluated, through selective angiography, the LITA of 39 patients with a median age of 63 years, submitted to coronary angiography, with indication of Coronary Artery Bypass Graft (CABG). Categorical variables were compared by chi-square test and Fisher's exact test. The single continuous variable, age, was tested for normality by the Kolmogorov-Smirnov test, described in median (P25; P75) and the groups compared with the Mann-Whitney test. The level of statistical significance adopted was p < 0.05. The analyzes were performed in SPSS ® software version 20. Results: It was identified the presence of 7.7% of disorders in the LITA that made it unfeasible to be used. In all of the patients there was no specific symptomatology evidencing the lesion. No variable was shown as a predictor for the occurrence of the outcomes. Conclusion: The prevalence of the lesions found in the study was significant, indicating that a preoperative evaluation of LITA could bring future benefits to the patients submitted to CABG

Fundamento: Pela observação da alta prevalência de falhas no tratamento cirúrgico da revascularização do miocárdio (RM), com o uso da Artéria Torácica Interna Esquerda (ATIE) como enxerto, evidenciadas pela literatura internacional, buscou-se demonstrar a prevalência de lesões que inviabilizem o uso da ATIE como enxerto na cirurgia de revascularização do miocárdio, com possível alteração na conduta cirúrgica tomada pelo cirurgião cardíaco, e redução da morbimortalidade destes pacientes. Objetivos: Avaliar a prevalência de lesões ateroscleróticas da ATIE, por meio da angiografia seletiva, pré - operatória, em pacientes submetidos à cinecoronariografia e com indicação de revascularização cirúrgica do miocárdio. Também foram analisadas outras lesões que inviabilizam o uso da ATIE como enxerto principal em casos de necessidade da cirurgia de revascularização do miocárdio (CRM). Métodos: Estudo analítico, transversal, de prevalência, que avaliou por meio da angiografia seletiva, a ATIE de 39 pacientes com mediana de idade de 63 anos, submetidos ao exame de cinecoronariografia, com indicação de CRM. As variáveis categóricas foram comparadas pelo teste do qui-quadrado e exato de Fisher. A única variável contínua, a idade, foi testada para normalidade pelo teste de Kolmogorov-Smirnov, descrita em mediana (P25; P75) e os grupos comparados com teste de Mann-Whitney. O nível de significância estatística adotado foi p < 0,05. As análises foram realizadas no software SPSS ® versão 20. Resultados: Foi identificada a presença de 7,7% de alterações na ATIE que inviabilizam sua utilização. Em todos os pacientes inexistiu a presença de qualquer sintomatologia especifica que evidencia a lesão. Nenhuma variável se mostrou como fator preditor para ocorrência dos desfechos. Conclusão: A prevalência das lesões encontradas no estudo mostrou-se significativa, indicando que uma avaliação pré-operatória de ATIE possa trazer benefícios futuros aos pacientes submetido à CRM

Starch Biocatalyst Based on α-Amylase-Mg/Al-Layered Double Hydroxide Nanohybrids.

The design of new biocatalysts through the immobilization of enzymes, improving their stability and reuse, plays a major role in the development of sustainable methodologies toward the so-called green chemistry. In this work, α-amylase (AAM) biocatalyst based on Mg3Al-layered double-hydroxide (LDH) matrix was successfully developed with the adsorption method. The adsorption process was studied and optimized as a function of time and enzyme concentration. The biocatalyst was characterized, and the mechanism of interaction between AAM and LDH, as well as the immobilization effects on the catalytic activity, was elucidated. The adsorption process was fast and irreversible, thus yielding a stable biohybrid material. The immobilized AAM partially retained its enzymatic activity, and the biocatalyst rapidly hydrolyzed starch in an aqueous solution with enhanced efficiency at intermediate loading values of ca. 50 mg/g of AAM/LDH. Multiple attachments through electrostatic interactions affected the conformation of the immobilized enzyme on the LDH surface. The biocatalyst was successfully stored in its dry form, retaining 100% of its catalytic activity. The results reveal the potential usefulness of a LDH compound as a support of α-amylase for the hydrolysis of starch that may be applied in industrial and pharmaceutical processes as a simple, environmentally friendly, and low-cost biocatalyst.

The effect of interlayer anion on the reactivity of Mg-Al layered double hydroxides: improving and extending the customization capacity of anionic clays.

Layered double hydroxides (LDHs) reactivity and interfacial behavior are closely interconnected and control particle properties relevant to the wide range of these solids' applications. Despite their importance, their relationship has been hardly described. In this work, chloride and dodecylsulfate (DDS(-)) intercalated LDHs are studied combining experimental data (electrophoretic mobility and contact angle measurements, hydroxyl and organic compounds uptake) and a simple mathematical model that includes anion-binding and acid-base reactions. This approach evidences the anion effect on LDHs interfacial behavior, reflected in the opposite particle charge and the different surface hydrophobic/hydrophilic character. LDHs reactivity are also determined by the interlayer composition, as demonstrated by the cation uptake capability of the DDS(-) intercalated sample. Consequently, the interlayer anion modifies the LDHs interfacial properties and reactivity, which in turn extends the customization capacity of these solids.