Cyclo- and Polyphosphazenes for Biomedical Applications

Cyclic and polyphosphazenes are extremely interesting and versatile substrates characterized by the presence of -P=N- repeating units. The chlorine atoms on the P atoms in the starting materials can be easily substituted with a variety of organic substituents, thus giving rise to a huge number of new materials for industrial applications. Their properties can be designed considering the number of repetitive units and the nature of the substituent groups, opening up to a number of peculiar properties, including the ability to give rise to supramolecular arrangements. We focused our attention on the extensive scientific literature concerning their biomedical applications: as antimicrobial agents in drug delivery, as immunoadjuvants in tissue engineering, in innovative anticancer therapies, and treatments for cardiovascular diseases. The promising perspectives for their biomedical use rise from the opportunity to combine the benefits of the inorganic backbone and the wide variety of organic side groups that can lead to the formation of nanoparticles, polymersomes, or scaffolds for cell proliferation. In this review, some aspects of the preparation of phosphazene-based systems and their characterization, together with some of the most relevant chemical strategies to obtain biomaterials, have been described.

Antimicrobial and physicochemical characterization of 2,3-dialdehyde cellulose-based wound dressings systems

Biobased and biodegradable films were prepared by physically mixing 2,3-dialdehyde cellulose (DAC) with two other biopolymers, zein and gelatin, in three different proportions. The antimicrobial activities of the composite blends against Gram-positive and Gram-negative bacteria increase with the increase of DAC content. Cell viability tests on mammalian cells showed that the materials were not cytotoxic. In addition, DAC and gelatin were able to promote thermal degradation of the blends. However, DAC increased the stiffness and decreased the glass transition temperature of the blends, while gelatin was able to decrease the stiffness of the film. Morphological analysis showed the effect of DAC on the surface smoothness of the blends. The contact angle confirmed that all blends were within the range of hydrophilic materials. Although all the blends showed impressive performance for wound dressing application, the blend with gelatin might be more suitable for this purpose due to its better mechanical performance and antibacterial activity.

Analysis of Polycaprolactone Microfibers as Biofilm Carriers for Biotechnologically Relevant Bacteria

Polymeric electrospun fibers are becoming popular in microbial biotechnology because of their exceptional physicochemical characteristics, biodegradability, surface-to-volume ratio, and compatibility with biological systems, which give them a great potential as microbial supports to be used in production processes or environmental applications. In this work, we analyzed and compared the ability of Escherichia coli, Pseudomonas putida, Brevundimonas diminuta, and Sphingobium fuliginis to develop biofilms on different types of polycaprolactone (PCL) microfibers. These bacterial species are relevant in the production of biobased chemicals, enzymes, and proteins for therapeutic use and bioremediation. The obtained results demonstrated that all selected species were able to attach efficiently to the PCL microfibers. Also, the ability of pure cultures of S. fuliginis (former Flavobacterium sp. ATCC 27551, a very relevant strain in the bioremediation of organophosphorus compounds) to form dense biofilms was observed for the first time, opening the possibility of new applications for this microorganism. This material showed to have a high microbial loading capacity, regardless of the mesh density and fiber diameter. A comparative analysis between PCL and polylactic acid (PLA) electrospun microfibers indicated that both surfaces have a similar bacterial loading capacity, but the former material showed higher resistance to microbial degradation than PLA.