In recent years, there has been an increasing interest in the development of antimicrobial materials for different applications, especially in the biomedical field. In this context, chitosan is one of the most employed materials due to its highly attractive properties, such as biocompatibility, biodegradability, non-toxicity, and antimicrobial activity against gram-negative and gram-positive bacteria and fungi. In this review, we discuss the different methods used to obtain chitosan and point out how they affect the structural and chemical properties of this material, followed by a detailed discussion on how these properties influence its antimicrobial activities. Additionally, we summarize the most accepted antimicrobial mechanisms of action for chitosans. Specifically, we aim to provide a comprehensive overview on the last findings and progress reported in the literature on the factors that influence the antimicrobial activity of chitosan, e.g., polymeric average molecular weight ( M W ¯), average degree of acetylation ( D A ¯), water-soluble derivatization and sample degree of purity. The data available in the literature indicate that in addition to the structural properties, the effectiveness of such antimicrobial activity of chitosan is also dependent on the target microorganisms. This review will help researchers to better understand the mechanism of action of chitosan against microorganisms based on its structural characteristics.

In recent years there has been an increasing interest in the development of nanomaterials with improved properties compared to their counterparts at the micro- and macroscopic scale. In this context, nanofibers obtained by electrospinning technique are highly attractive due to the unique combination of high surface area/volume ratio, porosity, flexibility, mechanical performance, simple processing and relatively low cost. In addition, the possibility to buildup nanofibers with different compositions, structures and properties allows the design of nanostructures for a wide range of applications. In this review, we will discuss the advances of the last decade in the use of the electrospinning to obtain nanofibers with different compositions and morphologies for varied applications. Specifically, we are interested in providing an overview of the state of the art in relation to the application of nanofibers in different areas, including healthcare, environment, sensing and energy. Finally, we will discuss the real perspective in terms of industrial application and future trends that have been pursued to improve the performance of electrospun nanofibers. This review will help researchers to understand the evolution and challenges of the area and will also stimulate even more interest in the development of new devices based on electrospun nanofibers.