Cristian A. Acevedo

The effect of an autologous cellular gel-matrix integrated implant system on wound healing

BackgroundThis manuscript reports the production and preclinical studies to examine the tolerance and efficacy of an autologous cellular gel-matrix integrated implant system (IIS) aimed to treat full-thickness skin lesions.MethodsThe best concentration of fibrinogen and thrombin was experimentally determined by employing 28 formula ratios of thrombin and fibrinogen and checking clot formation and apparent stability. IIS was formed by integrating skin cells by means of the in situ gelification of fibrin into a porous crosslinked scaffold composed of chitosan, gelatin and hyaluronic acid. The in vitro cell proliferation within the IIS was examined by the MTT assay and PCNA expression. An experimental rabbit model consisting of six circular lesions was utilized to test each of the components of the IIS. Then, the IIS was utilized in an animal model to cover a 35% body surface full thickness lesion.ResultsThe preclinical assays in rabbits demonstrated that the IIS was well tolerated and also that IIS-treated rabbit with lesions of 35% of their body surface, exhibited a better survival rate (p = 0,06).ConclusionIIS should be further studied as a new wound dressing which shows promising properties, being the most remarkable its good biological tolerance and cell growth promotion properties.

Simultaneous heat and mass transfer applied to non-respiring foods packed in modified atmosphere

A mathematical model to predict heat and mass transport phenomena in non-respiring food packed in modified atmosphere (MAP) was developed and validated. The model incorporates simultaneous gas convection, sorption, diffusion, heat convection and conduction. The model was applied to MAP systems containing CO2 ,O 2 ,N 2 and H2O. Validation test was done with gelatin. The average errors between experimental and simulated values were low: <0.6 (C) for the temperatures, 3% for relative humidity and <1.43% for the headspace gas composition. Model predictions during heating and cooling phases indicate that temperature modification of the packaged product can be quite slow, reflecting the relevance of proper chilling in the packaging, transport and storage processes of MAP products. The model applied to shelf-life studies, for specific products, can be utilized to identify facility and product handling improvements to generate the greater positive impact on product quality. The development of this or similar mathematical tools would allow for more technical and informed management decisions. 2003 Elsevier Ltd. All rights reserved.

Volatile organic compounds produced by human skin cells.

Skin produces volatile organic compounds (VOCs) released to the environment with emission patterns characteristic of climatic conditions. It could be thought that these compounds are intermediaries in cell metabolism, since many intermediaries of metabolic pathways have a volatile potential. In this work, using gas chromatography, we answered the question of whether VOC profiles of primary cultures of human dermal fibroblasts were affected by the type of culture conditions. VOCs were determined for different types of culture, finding significant differences between skin cells grown in classical monolayer culture -2D- compared with 3D matrix immobilized cultures. This indicates that VOC profiles could provide information on the physiological state of skin cells or skin.

Volatile profiles of human skin cell cultures in different degrees of senescence

It is known that skin releases volatile organic compounds to the environment, and also that its emission pattern changes with aging of the skin. It could be considered, that these compounds are intermediaries in cell metabolism, since many intermediaries of metabolic pathways have a volatile potential. In this work, a simple and non-destructive method consisting of SPME sampling and GC/MS analysis was developed to identify volatile organic emanations from cell cultures. This technique, applied to skin cells culture, indicates that the cells or cell metabolism produce several skin emissions. Chemometric analysis was performed in order to explore the relationship between a volatile profile and the senescence of cell cultures. Volatile profiles were different for cell cultures in different degrees of senescence, indicating that volatile compound patterns could be used to provide information about the age of skin cells.

Using RGB Image Processing for Designing an Alginate Edible Film

The use of edible films to coat food products is a technique that allows for an extended shelf-life. One of the most widely used polymers is calcium alginate. However, this polymer can modify the original food color and the perception by consumers. The objective was to design an alginate film based principally on color changes using a RGB color model. Edible films were prepared with sodium alginate and glycerol as plasticizer, cross-linking the polymer with calcium. Dry and hydrated states of the edible films were studied. Film thickness was directly proportional to surface concentration and increased with hydration. There is a zone in which the color does not change with alginate surface concentration and another where the color is directly proportional to it. This latter scenario is not a consequence of structural changes or the degree of hydration. Results showed a range where the color was not modified by the alginate concentration; hence, an optimal surface concentration was determined as a design parameter. Edible films made using the optimal surface concentration would not mask microbial contamination and have good physical properties (water vapor transmission and swelling) compared with other surface concentrations. In addition, it was possible to model alginate surface concentration as a function of surface color using mathematical tools (clustering, linear regression, and support vector machine), allowing one to study the optimal use of the edible films.

A Comparative Study of Stout Beer Batch Fermentation Using Free and Microencapsulated Yeasts

Because many questions arise regarding the use of immobilization technology to consistently produce a high quality beer, this work focuses on the effects of using an immobilization matrix in the fermentation process. The aim of this study was to explore the feasibility and potential uses of immobilization on sensorial characteristics such as color, flavor, and headspace compounds of stout beer, when using batch fermentation. Batch production of beer was conducted as a standard ale process for stout beer production. For the immobilized yeasts fermentation, cells were microencapsulated in alginate, by using the Thiele modulus procedure for microcapsule design. Glucose concentration, cell multiplication, cell viability, specific gravity, pH, Brix, and ethanol were monitored throughout the fermentation process. Both, sensorial analysis (statistic triangle tests) and instrumental methods (gas chromatography to measure headspace compounds and visible spectrophotometer to quantify the color) were used to evaluate characteristics of the beer that was produced from immobilized and free yeast fermentations. Free and immobilized yeasts fermentation showed no significant difference (p > 0.05) for all variables of interest. The profile of headspace compounds was different, perhaps because of changes in yeast’s behavior and the presence of secondary metabolites. However, immobilization did not have a significant impact on the beer flavor, as detected by the sensorial triangle test.

Modeling Volatile Organic Compounds Released by Bovine Fresh Meat Using an Integration of Solid Phase Microextraction and Databases

The influence of volatile organic compounds is often regarded as a critical factor of food flavor quality. Nevertheless, information about the biochemical origin of odorants is not totally available. Quantification of volatile compounds in meat is not easy, but a new approach that helps is the use of GC/MS–SPME. This technique can generate large-scale data sets that allow for the development of computational technologies for better integration and biochemical interpretation. Volatile organic compounds of bovine fresh meat samples were measured by GC/MS–SPME, using four SPME fibers. The compounds were analyzed using an integration of chemical and biological database systems (NIST and KEGG, respectively). Twelve metabolic pathways were identified. A metabolic network model was constructed using graph elements, linking pathways through a central branch mediated by glycolysis. Experimental data indicated that post-mortem glycolysis is associated with the release of volatile compounds in fresh meat. The proposed technique could be used to study possible sources of biochemical compounds in meat to be applied in food analysis.

Designing a gelatin/chitosan/hyaluronic acid biopolymer using a thermophysical approach for use in tissue engineering.

Cell culture on biopolymeric scaffolds has provided treatments for tissue engineering. Biopolymeric mixtures based on gelatin (Ge), chitosan (Ch) and hyaluronic acid (Ha) have been used to make scaffolds for wound healing. Thermal and physical properties of scaffolds prepared with Ge, Ch and Ha were characterized. Thermal characterization was made by using differential scanning calorimetry (DSC), and physical characterization by gas pycnometry and scanning electron microscopy. The effects of Ge content and cross-linking on thermophysical properties were evaluated by means of a factorial experiment design (central composite face centered). Gelatin content was the main factor that affects the thermophysical properties (microstructure and thermal transitions) of the scaffold. The effect of Ge content of the scaffolds for tissue engineering was studied by seeding skin cells on the biopolymers. The cell attachment was not significantly modified at different Ge contents; however, the cell growth rate increased linearly with the decrease of the Ge content. This relationship together with the thermophysical characterization may be used to design scaffolds for tissue engineering.

Growth factor production from fibrin-encapsulated human keratinocytes.

Fibrin has been used extensively in cell encapsulation because it has important biological properties. Keratinocyte encapsulation in fibrin is a widely used technique in skin tissue engineering. The production of growth factors (EGF, TGF-β1 and PDGF-BB) was evaluated when keratinocytes are encapsulated in fibrin. Secretions of TGF-β1 and PDGF-BB increased more than five times compared to monolayer cultures. Encapsulated cells secreted about 80% active form of TGF-β1 (monolayer cells only secreted inactive form). An enhanced secretion of TGF-β1 and PDGF-BB was found in encapsulated cells, showing that fibrin capsules are favourable for the production of these growth factors.

Prediction correlation of vapor pressure for methyl jasmonate

Abstract A vapor pressure correlation based on Antoine’s equation was proposed for methyl jasmonate. Equilibrium data was obtained in the range of 3–100 °C and analyses were performed with GC–MS by solid phase microextraction technique. The correlation gives an acceptable extrapolation for the boiling point at atmospheric pressure, allowing evaluation of vapor pressure at temperatures usually found in food and agricultural process applications.