Study of the controlled radicalar polymerization mediated by nitroxides (NMRP) in emulsion for the production of microparticles with biomedical aplication

Abstract

It is called embolism or blockage of a vessel by a thrombus to shift the site of obstruction (then calling himself thromboembolism), adipose tissue (fat embolism), air (air embolism) or a foreign body (such as iatrogenic embolism by tips Catheter). The vessel obstruction can lead to complications downstream most evident in the case of emboli upstream artery or, in the case of involvement of veins or lymphatic vessels. The most common and preventable cause of death in hospitalized patients is pulmonary thromboembolism. In some cases, embolization is intentionally caused by the use of radiological technique, obstructing a blood vessel. Regarding technical aspects, the two most important variables during embolization are embolizing material choice and the end point of embolization. While a number of materials have already been employed as embolic agents, polymeric particles are one of the most widely used materials today. Studying the properties of controlled release of a microencapsulated chemotherapy in renal arteries of dogs, KATO and colleagues found that the therapeutic effect of the infusion of these microcapsules was a result of joint action by the local release of the drug and the vessel embolization. This led the authors to postulate the term chemoembolization, which consists in combining intra-arterial infusion of a chemotherapeutic agent to the vascular embolization. Over the past 30 years, several studies were conducted with the aim of developing embolic agents and load them with medication to be used in transarterial chemoembolization. Among the embolizing agents available today, there is a DC Bead ® (Biocompatibles, Surrey, UK) which are non-biodegradable microspheres of PVA modified with sulphonate groups, which allows this device to "hijack" drugs of opposite charge and release them in a controlled manner. The technology of controlled release of drugs represents one of the frontiers of science, which involves different aspects multidisciplinary and can contribute greatly to the advancement of human health. The delivery systems often described as "drug delivery systems", offer numerous advantages when compared to other conventional dosage. Some of these advantages are listed below:i. Greater therapeutic efficacy, with gradual and controlled release of the drug from the matrix degradation; ii. Significant decrease toxicity and increased length of stay in the circulation; iii. Nature and composition of vehicles varied and, contrary to what one might expect, there was a predominance of instability and decomposition mechanisms of drug (bio premature inactivation); iv. Secure administration (without local inflammatory reactions) and convenient (fewer doses); v. Targeting specific targets without significant immobilization of bioactive species; vi. Both lipophilic hydrophilic substances as may be incorporated;Before considering the use, development and variety of nanoparticles applied to these systems, which involve devices directed at specific targets in the body, it is necessary to evaluate the motivation that led to its use. This work will also show and discuss new developments in this area, by using nanoparticles as carriers and prospects for the future, along with proper critical assessment. The production of embolic agents morphology of the core-shell type PVA / PVAc was more efficient than the use of particles with irregular morphology of PVA. Obtaining these particles is made from a process of free radical polymerization in suspension and subsequent modification of the obtained polymer. However, as the polymerization reaction is carried from free radical reactions, it is possible to control the core architecture, which restricts the "quality" of the final particle obtained. Once the polymerization NMRP allows fairly precise control polymer formation, suggests the use of this technique in producing spherical core-shell type for use in vascular embolization.