RESUMO
In this paper we report on the production of microbioreactors using ionically cross-linked gellan containing immobilized yeast cells with potential application in glucose fermentation. Cross-linking was achieved through a novel extrusion process in capillary by ionotropic gelation under the action of magnesium acetate. Compared to commonly used methods, this provides a host of practical advantages. The particles were physico-chemically and morphologically characterized as their mechanical stability, behavior in aqueous media, and bio-catalytic activity are influenced by the amount of cross-linker used. This demonstrated their ability to be reused in a large number of fermentation cycles without losing their bio-catalytic activity. Our results are wholly comparable with the behavior of free yeast. We show that fermentation cycles can succeed either immediately or at variable intervals, ensuring high yields of glucose transformation, comparable-if not superior-to results currently obtained using free yeast.
Assuntos
Reatores Biológicos/microbiologia , Magnésio/química , Polissacarídeos Bacterianos/química , Saccharomyces cerevisiae/citologia , Saccharomyces cerevisiae/metabolismo , Acetatos/química , Sobrevivência Celular , Células Imobilizadas/citologia , Células Imobilizadas/metabolismo , Fermentação , Glucose/metabolismoRESUMO
The aim of the present study is to obtain, for the first time, polymer magnetic nanoparticles based on the chitosan-maltose derivative and magnetite. By chemically modifying the chitosan, its solubility in aqueous media was improved, which in turn facilitates the nanoparticles' preparation. Resulting polymers exhibit enhanced hydrophilia, which is an important factor in increasing the retention time of nanoparticles in the blood flow. The preparation of nanoparticles relied on the double crosslinking technique (ionic and covalent) in reverse emulsion which ensures the mechanical stability of the polymer carrier. The characterization of both the chitosan derivative and nanoparticles was accomplished by Fourier Transform Infrared Spectroscopy, Nuclear Magnetic Resonance Spectroscopy, Scanning Electron Microscopy, Transmission Electron Microscopy, Atomic Force Microscopy, Vibrating Sample Magnetometry, and Thermogravimetric Analysis. The evaluation of morphological, dimensional, structural, and magnetical properties, as well as thermal stability and swelling behavior of nanoparticles was made from the point of view of the polymer/magnetite ratio. The study of 5-Fluorouracil loading and release kinetics as well as evaluating the cytotoxicity and hemocompatibility of nanoparticles justify their adequate behavior in their potential use as devices for targeted transport of antitumor drugs.
Assuntos
Antineoplásicos/farmacologia , Quitosana/química , Sistemas de Liberação de Medicamentos/métodos , Nanopartículas de Magnetita/química , Maltose/química , Animais , Morte Celular/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Fluoruracila/farmacologia , Hemólise/efeitos dos fármacos , Humanos , Cinética , Nanopartículas de Magnetita/ultraestrutura , Microscopia de Força Atômica , Espectroscopia de Prótons por Ressonância Magnética , Coelhos , Espectroscopia de Infravermelho com Transformada de Fourier , Suspensões , Temperatura , TermogravimetriaRESUMO
In this review, we will summarize the particularities of each of the following barriers from the point of view of drugs passing across them; blood brain barrier, ocular barriers, skin and mucosal barriers. Also, for each biological barrier the most representative examples of polysaccharides and cyclodextrins nanoformulations are presented.
