Reaching Biocompatibility with Nanoclays: Eliminating the Cytotoxicity of Ir(III) Complexes.

Cyclometalated IrIII complexes are promising candidates for biomedical applications but high cytotoxicity limits their use as imaging and sensing agents. We herein introduce the use of Laponite as carrier for triplet-emitting cyclometalated IrIII complexes. Laponite is a versatile nanoplatform because of its biocompatibility, dispersion stability and large surface area that readily adsorbs functional nonpolar and cationic molecules. These inorganic-organic hybrid nanomaterials mask cytotoxicity, show efficient cell uptake and increase luminescent properties and photostability. By camouflaging intrinsic cytotoxicity, this simple method potentially extends the palette of available imaging and sensing dyes to any metal-organic complexes, especially those that are usually cytotoxic.

Human macrophage responses to metal-oxide nanoparticles: a review.

Nanomaterials have been widely used in our daily lives in medicine, cosmetics, paints, textiles and food products. Many studies aim to determine their biological effects in different types of cells. The interaction of these materials with the immune system leads to reactions by modifying the susceptibility or resistance of the host body which could induce adverse health effects. Macrophages, as specific cells of the innate immune response, play a crucial role in the human defence system to foreign agents. They can be used as a reliable test object for the investigation of immune responses under nanomaterials exposure displayed by expression of a variety of receptors and active secretion of key signalling substances for these processes. This report covers studies of human macrophage behaviours upon exposure of nanomaterials. We focused on their interaction with metal-oxide nanoparticles as these are largely used in medical and cosmetics applications. The discussion and summary of these studies can guide the development of new nanomaterials, which are, at the same time, safe and useful for new purposes, especially for health applications.

Reaction of human macrophages on protein corona covered TiO2 nanoparticles.

The cytokine secretion of primary cells of human macrophages during the interaction of TiO2 nanoparticles (with an average primary size of 100-120 nm) is investigated down to concentration levels suggested to be relevant for in vivo conditions. We find that high TiO2 concentrations induce the cytokines Interleukin IL-1ß, IL-6, and IL-10 secretion, while at low concentrations only IL-6 secretion is observed. To obtain further evidence on in vivo conditions we investigated the development and structure of the protein corona of the nanoparticles. We demonstrated that the surface of TiO2 particles attract preferably secondary modified proteins which then induce cytokine secretion of macrophages. Our results indicate that concentration of corona covered TiO2 particles below 1 µg/ml induce IL-6 secretion which is reported to be responsible for the development of autoimmune diseases as well as for the secretion of acute phase proteins. FROM THE CLINICAL EDITOR: This study investigates the effects of protein corona covered titanium dioxide nanoparticles on human macrophages, concluding that concentration of such particles below 1 µg/ml induces IL-6 secretion, which may be responsible for the development of autoimmune diseases as well as for the secretion of acute phase proteins. This finding has important implications on future applications of such nanoparticles.

Freeze-dried snake antivenoms formulated with sorbitol, sucrose or mannitol: comparison of their stability in an accelerated test.

Freeze-drying is used to improve the long term stability of pharmaceutical proteins. Sugars and polyols have been successfully used in the stabilization of proteins. However, their use in the development of freeze-dried antivenoms has not been documented. In this work, whole IgG snake antivenom, purified from equine plasma, was formulated with different concentrations of sorbitol, sucrose or mannitol. The glass transition temperatures of frozen formulations, determined by Differential Scanning Calorimetry (DSC), ranged between -13.5 °C and -41 °C. In order to evaluate the effectiveness of the different stabilizers, the freeze-dried samples were subjected to an accelerated stability test at 40 ± 2 °C and 75 ± 5% relative humidity. After six months of storage at 40 °C, all the formulations presented the same residual humidity, but significant differences were observed in turbidity, reconstitution time and electrophoretic pattern. Moreover, all formulations, except antivenoms freeze-dried with mannitol, exhibited the same potency for the neutralization of lethal effect of Bothrops asper venom. The 5% (w:v) sucrose formulation exhibited the best stability among the samples tested, while mannitol and sorbitol formulations turned brown. These results suggest that sucrose is a better stabilizer than mannitol and sorbitol in the formulation of freeze-dried antivenoms under the studied conditions.

Freeze-drying microscopy in mathematical modeling of a biomaterial freeze-drying

Transplantation brings hope for many patients. A multidisciplinary approach on this field aims at creating biologically functional tissues to be used as implants and prostheses. The freeze-drying process allows the fundamental properties of these materials to be preserved, making future manipulation and storage easier. Optimizing a freeze-drying cycle is of great importance since it aims at reducing process costs while increasing product quality of this time-and-energy-consuming process. Mathematical modeling comes as a tool to help a better understanding of the process variables behavior and consequently it helps optimization studies. Freeze-drying microscopy is a technique usually applied to determine critical temperatures of liquid formulations. It has been used in this work to determine the sublimation rates of a biological tissue freeze-drying. The sublimation rates were measured from the speed of the moving interface between the dried and the frozen layer under 21.33, 42.66 and 63.99 Pa. The studied variables were used in a theoretical model to simulate various temperature profiles of the freeze-drying process. Good agreement between the experimental and the simulated results was found.

A prática da transplantação traz esperança para muitos pacientes. Uma visão multidisciplinar nessa área visa à produção de tecidos biológicos para serem utilizados como implantes e próteses. A liofilização é um processo de secagem que preserva características essenciais desses materiais, facilitando sua manipulação e armazenamento. A liofilização é um processo que requer muito tempo e energia e sua otimização é muito importante, pois permite reduzir custos de processo melhorando a qualidade do produto. A modelagem matemática é uma ferramenta que permite descrever o comportamento do produto durante o processo e, consequentemente, auxilia os estudos de otimização. Microscopia óptica acoplada à liofilização, uma técnica usualmente aplicada na determinação de temperaturas críticas de formulações líquidas, foi utilizada neste trabalho na determinação de taxas de sublimação da liofilização de um tecido biológico. As taxas de sublimação foram calculadas a partir da velocidade da interface entre a camada seca e congelada, sob pressões de 21,33, 42,66 e 63,99 Pa. As variáveis estudadas foram usadas em um modelo matemático teórico, que simula os perfis de temperatura do produto durante o ciclo de liofilização. Os resultados apresentados demonstraram boa relação entre os dados experimentais e simulados.

Effect of freeze-drying on the mechanical, physical and morphological properties of glutaraldehyde-treated bovine pericardium: evaluation of freeze-dried treated bovine pericardium properties.

PURPOSE: Biomaterials have been widely used in the field of regenerative medicine. Bovine pericardium tissue has been successfully used as a bioprosthetic material in manufacturing heart valves, but studies concerning the tissue are ongoing in order to improve its storage, preservation and transportation. This article provides an overview of the characteristics of bovine pericardium tissue chemically treated after the freeze-drying process. These characteristics are essential to evaluate the changes or damage to the tissue during the process. METHODS: The mechanical properties of the tissue were analyzed by three different methods due to its anisotropic characteristics. The physical properties were analyzed by a colorimetric method, while the morphological properties were evaluated by scanning electron microscopy (SEM). RESULTS: The freeze-dried bovine pericardium showed no significant change in its mechanical properties. There was no significant change in the elasticity of the tissue (p>0.05) and no color change. In addition, SEM analysis showed that the freeze-dried samples did not suffer structural collapse. CONCLUSIONS: It was concluded that glutaraldehyde-treated bovine pericardium tissue showed no significant change in its properties after the freeze-drying process.

The influence of freezing rates on bovine pericardium tissue Freeze-drying

The bovine pericardium has been used as biomaterial in developing bioprostheses. Freeze-drying is a drying process that could be used for heart valve's preservation. The maintenance of the characteristics of the biomaterial is important for a good heart valve performance. This paper describes the initial step in the development of a bovine pericardium tissue freeze-drying to be used in heart valves. Freeze-drying involves three steps: freezing, primary drying and secondary drying. The freezing step influences the ice crystal size and, consequently, the primary and secondary drying stages. The aim of this work was to investigate the influence of freezing rates on the bovine pericardium tissue freeze-drying parameters. The glass transition temperature and the structural behaviour of the lyophilized tissues were determined as also primary and secondary drying time. The slow freezing with thermal treatment presented better results than the other freeze-drying protocols.

O pericárdio bovino é um material utilizado na fabricação de biopróteses. A liofilização é um método de secagem que vem sendo estudado para a conservação de válvulas cardíacas. A preservação das características do biomaterial é de fundamental importância no bom funcionamento das válvulas. Este artigo é a primeira etapa do desenvolvimento do ciclo de liofilização do pericárdio bovino. Liofilização é o processo de secagem no qual a água é removida do material congelado por sublimação e desorção da água incongelável, sob pressão reduzida. O congelamento influencia o tamanho do cristal de gelo e, consequentemente, a secagem primária e secundária. O objetivo deste estudo foi verificar a influência das taxas de congelamento nos parâmetros de liofilização do pericárdio bovino. Determinou-se a temperatura de transição vítrea e o comportamento estrutural do pericárdio bovino liofilizado. Determinou-se o tempo da secagem primária e secundária. O protocolo de liofilização utilizando-se congelamento lento com annealing apresentou os melhores resultados.

Otimização da liofilização do pericárdio bovino com o auxílio de ferramentas matemáticas / Freeze-drying optimization of bovine pericardium by mathematical modelingFreeze-drying optimization of bovine pericardium by mathematical modeling

A liofilização é um método de conservação utilizado para a obtenção de produtos desidratados de alta qualidade. É um processo que requer tempo e energia, podendo levar dias para terminar se o ciclo de liofilização não for otimizado. O objetivo da otimização do processo de liofilização é minimizar o consumo de energia e reduzir o tempo de processo, sem que ocorra a perda na qualidade do produto liofilizado. A utilização de modelos matemáticos que predizem o comportamento do produto durante a liofilização pode reduzir drasticamente o número de experimentos, além de determinar variáveis importantes que não podem ser medidas experimentalmente. Tecidos biológicos são produtos sensíveis que se submetidos à altas temperaturas podem sofrer alterações irreversíveis. O estudo da liofilização do pericárdio bovino tem como objetivo sua conservação, facilitando sua manipulação e armazenamento. O objetivo deste projeto foi o uso da teoria fenomenológica que envolve a liofilização, com a utilização de parâmetros essenciais determinados por experimentos de laboratório, para guiar o desenvolvimento de um modelo matemático capaz de descrever a dinâmica do processo de liofilização do pericárdio bovino para, através de seu estudo e da análise das características do produto liofilizado, alcançar a validação do processo. O estudo do congelamento na liofilização do pericárdio bovino foi feito, determinando-se os tempos de processo e o conteúdo de umidade residual do produto seco. A modelagem matemática do processo foi apresentada a partir da determinação de taxas de sublimação por microscopia óptica acoplada à liofilização, sob diferentes pressões de câmara e taxas de aquecimento de placa. Os produtos liofilizados foram avaliados quanto à manutenção de suas propriedades físicas. Os resultados mostraram que o congelamento lento com tratamento térmico apresentou curto tempo de liofilização e baixo valor de umidade residual do produto final. O modelo matemático demonstrou a...

Freeze-drying is a method of preservation that provides high-quality dehydrated products. It is a process that requires time and energy and it may take days to finish. Freeze-drying optimization is used to minimize the process time keeping the high quality of the product. Mathematical models that predict the behavior of products during freeze-drying can drastically reduce the number of experiments and determine variables in a study that could not be experimentally measured. Biological tissues are sensitive to heat and might be irreversibly modified. The study of bovine pericardium freeze-drying improves its handling and storage. The purpose of this project was to determine key parameters which served to guide the development of a mathematical model able to describe the bovine pericardium freeze-drying process and achieve its validation. The study of the freezing step in the bovine pericardium freeze-drying was done by analyzing the time of the process and the residual moisture content of the dried product. Mathematical modeling of the process was shown from the determination of sublimation rates by freeze-drying microscopy under different chamber pressures and heating rates. The freeze-dried products were evaluated for the maintenance of their physical properties. The results revealed that slow freezing with thermal treatment had short process time and low residual moisture of the final product. The mathematical model demonstrated the bovine pericardium freeze-drying and the product indicated no change in their physical properties after the process. Thus, the freeze-drying microscopy analysis was validated in determining the sublimation rate during the bovine pericardium freeze-drying and the process was endorsed through mathematical modeling