1,721,103 research outputs found
Polysaccharides as drug delivery systems for different administration routes
Full text linkPolysaccharides are biocompatible and biodegradable long carbohydrate molecules organized in repeated monosaccharide units interconnected with glycosidic bonds. These polymers constitute a large source of biomaterials for drug vehicles, controlled drug delivery, tissue engineering etc.
The ionic character and the presence of reactive functional group led them to be good candidates for the development of controlled release formulations. They are well tolerated by living tissues and body cavities due to their biocompatibility and biodegradability. In fact, polysaccharides have been widely proposed as drug delivery devices for many administration routes such as oral, parenteral, ophthalmic, nasal and transdermal route.
Furthermore, polysaccharides can be considered appropriate for tissue engineering thanks to their mechanical and biochemical functions and ability to deliver and foster cells.The aim of the present work was the development of polysaccharides based platform formulations as novel and suitable delivery systems of specific drugs into determined anatomical districts
Not only pH. Specific buffer effects in biological systems
No full textThe aim of this work is to overview the specific effect of pH buffers in biological systems. The pH of a buffer solution changes only slightly when a small amount of a strong acid or bases is added to it. This is widely accepted and applied both in chemical and in biological (i.e. enzyme catalysis) systems. Here we show some examples - spanning from pH measurements, enzyme activities, electrophoretic mobilities, antibody aggregation, protein thermal stability - that demonstrate additional roles of buffers. They not only set pH, but also address specific ion effects, in terms of Hofmeister series, when strong electrolytes are also added. From the experimental data referred to some charged biological moieties it emerges that different buffers, at the same nominal pH, can specifically adsorb at the charged surface. Buffer specific adsorption modifies several molecular and macroscopic properties amongst which electrophoretic mobilities, and hence effective surface charges, are particularly significant. More importantly, buffers' weak electrolytes, even at low concentration, are found to compete for the adsorption at the charged surfaces with strong electrolytes, thus modulating Hofmeister effect
Models and mechanisms of Hofmeister effects in electrolyte solutions, and colloid and protein systems revisited
Full text linkSpecific effects of electrolytes have posed a challenge since the 1880's. The pioneering work was that of Franz Hofmeister who studied specific salt induced protein precipitation. These effects are the rule rather the exception and are ubiquitous in chemistry and biology. Conventional electrostatic theories (Debye–Hückel, DLVO, etc.) cannot explain such effects. Over the past decades it has been recognised that additional quantum mechanical dispersion forces with associated hydration effects acting on ions are missing from theory. In parallel Collins has proposed a phenomenological set of rules (the law of matching water affinities, LMWA) which explain and bring to order the order of ion–ion and ion–surface site interactions at a qualitative level. The two approaches appear to conflict. Although the need for inclusion of quantum dispersion forces in one form or another is not questioned, the modelling has often been misleading and inappropriate. It does not properly describe the chemical nature (kosmotropic/chaotropic or hard/soft) of the interacting species. The success of the LMWA rules lies in the fact that they do. Here we point to the way that the two apparently opposing approaches might be reconciled. Notwithstanding, there are more challenges, which deal with the effect of dissolved gas and its connection to ‘hydrophobic’ interactions, the problem of water at different temperatures and ‘water structure’ in the presence of solutes. They take us to another dimension that requires the rebuilding of theoretical foundations
Specific Ion Effects on Adsorption of Lysozyme on Functionalized SBA-15 Mesoporous Silica
No full textOrdered mesoporous materials (OMMs) have a pore size suitable to host proteins. Previous works have shown how to tune the amount of adsorbed protein by changing pH or ionic strength of the adsorbing solution. Here we investigated the adsorption of lysozyme on a functionalized SBA-15 (SBA-15-NH2) as a function of added salts. For the first time, it was ascertained that the amount of adsorbed protein follows a reversed Hofmeister series for anions (sodium salts), SCN- > ClO4 - > Br - > NO3 - > Cl- > SO 4 2-, whereas for cations (chloride salts) the sequence was Na+ > Li+ > K+ > Cs+. These findings not only demonstrate a specific effect of the Na+ SCN- ion pair in favoring the adsorption at a solid surface but confirm also the role of the biologically important sodium ions. In addition, the process was found to be more effective at 0.2 M than at 0.8 M, thus indicating that adsorption also depends on the added salt concentration
Ionic strength affects lysozyme adsorption and release from SBA-15 mesoporous silica
No full textIn the present work we investigated the effect of ionic strength on the adsorption and release of a model therapeutic protein-hen egg white lysozyme (E.C.3.1.1.17)-from SBA-15 mesoporous silica. The biological function of lysozyme is the hydrolysis of polysaccharides constituting bacterial cell walls and, hence, it is a powerful antimicrobial agent. Here, lysozyme adsorption on SBA-15, carried out at different temperatures, showed that the adsorption capacity generally decreases with increasing the temperature, according to an exothermic process. The lysozyme adsorption kinetics on SBA-15 can be described through a pseudo-second order model or, alternatively, with an intraparticle diffusion model. Finally, the sustained release of lysozyme from SBA-15, carried out at 37 °C in a buffer solution at the physiological pH (7.4) and ionic strength (0.15 M NaCl), was measured both in terms of released amount of protein and released enzymatic activity. We found that the ionic strength of the immobilizing solution strongly affects lysozyme release trends. These effects are likely due to the interaction of electrolytes with both the biological and the inorganic surfaces, which results in the modulation of the forces at the basis of adsorption and release processes
Electrosynthesised CdS@ZnS quantum dots decorated multi walled carbon nanotubes for analysis of propranolol in biological fluids and pharmaceutical samples
No full textQuantum dots (QDs) based electrochemical assays have received a great deal of attention. They preserve the outstanding characteristics of electrochemical methodologies with respect to simplicity, ease-of-use, and costeffective instrumentation. In this work, a new challenge was opened up to explore the electrochemical features of CdS@ZnS as two well-known semiconductors for analytical utilizations. Here, CdS@ZnS core-shell QDs have been prepared electrochemically and applied for electrochemical sensor development in this approach. An activated glassy carbon electrode modified with a thin film of multi walled carbon nanotube was coated with CdS@ZnS QDs (activated GCE/MWCNTs/CdS@ZnS) as a thin uniform layer for analysis and monitoring of propranolol (PRO), a non-selective beta-blocker drug. Field emission scanning electron microscopy (FESEM) and energy-dispersive X-ray spectroscopy (EDX) were used to characterize the surface morphology of the developed electrodes. The results demonstrated that CdS@ZnS QDs were well-dispersed on the activated GCE/MWCNTs surface and were able to enhance the number of adsorbed analyte molecules. The electrochemical behavior of the PRO was studied at the modified electrode surface. The kinetic parameters of electron transfer coefficient (alpha) and the catalytic rate constant (kcat) for the electron transfer between PRO and the modified electrode were calculated. The electrochemical oxidation mechanism of PRO was also investigated by square wave voltammetry (SWV). Under optimal conditions, the proposed sensor demonstrated a linear response towards propranolol in the range of 0.06-27 mu mol L-1 and a detection limit of 12 nmol L-1. Furthermore, the analytical performance of the developed sensor was evaluated for measuring propranolol in biological fluids and pharmaceutical samples. The observed promising results confirm the suitability of the developed sensor for applications in measuring complex materials
Wax esters synthesis from heavy fraction of sheep milk fat and cetyl alcohol by immobilised lipases
No full textThe molecular motion of bovine serum albumin under physiological conditions is ion specific
Full text linkSpecific ion effects on the Brownian molecular motion of BSA protein under physiological conditions are investigated. New useful insights into Hofmeister phenomena related to electrolyte-protein interactions are presented
A bienzymatic biocatalyst constituted by glucose oxidase and Horseradish peroxidase immobilized on ordered mesoporous silica
Full text linkIt is presently extremely challenging to realize an active immobilized multi-enzyme biocatalyst which allows to run in vitro multi-step cascade reactions. This work deals with the obtainment of a bienzymatic immobilized biocatalyst constituted by Glucose Oxidase (GOx) and Horseradish Peroxidase (HRP) immobilized onto SBA-15 mesoporous silica. The effect of co-immobilization (GOx/HRP@SBA-15) versus the separated immobilization (GOx@SBA-15/HRP@SBA-15), and the effect of covalent versus physical immobilization, on protein loading and enzymatic activity were investigated. Regardless the different immobilization strategy used, it was found that the catalytic activity could be retained only if the immobilized bienzymatic biocatalyst was kept wet. The obtained wet GOx/HRP@SBA-15 biocatalyst could be recycled 14 times keeping a good activity. Finally, the bienzymatic biocatalyst was tested for the oxidation of two model phenolic (caffeic acid and ferulic acid) pollutants of agricultural wastewaters, as olive mill wastewaters (OMWs). The biocatalyst was able to reach a 70% conversion within 15 min
Novel mannitol based non-ionic surfactants from biocatalysis - part two - Improved synthesis
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