Síntese de nanocompósitos a base de nanocelulose bacteriana e nanoestruturas de óxido de nióbio

Abstract

Bacterial colonies on the surfaces can cause health problems and increase antibiotic resistance due to the improper or excessive use of these medications. To minimize these issues, new materials with antimicrobial properties are necessary. Nanostructured materials, such as metal oxides, are of interest for this demand, among which niobium pentoxide (Nb2O5) is a promising material due to its biocompatibility, low cytotoxicity, photocatalytic properties, improved corrosion resistance, increased radiopacity, and enhanced osteoblast adhesion. Another material that has been proven relevant for medical applications is bacterial nanocellulose (BNC), a biodegradable, biocompatible, low-cytotoxicity, and renewable material. Due to its high surface area and hydrophilic groups in its structure, BNC can be used in the production of nanocomposites. The aim of this work is to synthesize nanocomposites composed of bacterial nanocellulose (BNC) and niobium pentoxide nanostructures (Nb2O5) for potential medical applications. BNC was synthesized using the bacteria Komagataeibacter hansenii and subsequently oxidized with 2,2,6,6- tetramethyl-1-piperidinyloxy (TEMPO) to insert COOH groups on its surface (BNCCOOH). Its formation was confirmed through FTIR, and its crystallinity was calculated at 91.7%, with Iβ-type polymorphism. Nb2O5 nanostructures were synthesized using an alkaline hydrothermal method, forming sodium niobate nanowires (NaNbO3) with tetragonal, monoclinic, and orthorhombic crystal phases, average diameters ranging from 284 to 728 nm, and crystallinity of 91.5%. Subsequently, this material was silanized with 3-aminopropyltriethoxysilane (APTES) to insert -Si(CH2)3-NH2 groups on its surface (N130Nb2O5-NH2). This material appeared in the form of nanowires with average diameters of 163 nm and crystallinity of 76.8%, in addition to showing antimicrobial activity with inhibition zones of 20 and 26 mm against Escherichia coli and Staphylococcus aureus, being more effective against bacteria compared to vancomycin, which presented inhibition zones between 15 and 17 mm. Three nanocomposites were synthesized by different methods. Two of them were obtained through adsorption: NCB-COOH/N130Nb2O5-AD, which appeared in the form of a film with 57.1% crystallinity, and NCB-COOH/N130Nb2O5-NH2-AD in proportions of 1:3 and 1:4 (NCB-COOH/N130Nb2O5-NH2), with crystallinities of 51.1% and 68.3%, respectively. The NCB-COOH/N130Nb2O5-NH2 nanocomposite was obtained via the Ugi multicomponent reaction, which involves four components: a carboxylic acid (NCB-COOH), an amine (N130Nb2O5-NH2), an aldehyde (benzaldehyde), and an isocyanide (cyclohexylisocyanide). This reaction is quite promising as it combines four components in a single vessel, saving steps and atoms, offering synthesis efficiency, low energy consumption, and reduced waste generation, as well as ease of replication. The nanocomposites synthesized by Ugi reaction in the proportions of 1:1, 1:3, and 1:4 (NCB-COOH) also appeared as an opaque film and exhibited N130Nb2O5-NH2 nanowires on their surface with average diameters of 252.8, 341.5, and 542.2 nm, respectively. The crystallinity of these nanocomposites was 65%, 70.6%, and 74%, respectively. For both synthesis methods, Escherichia coli and Staphylococcus aureus were resistant to the nanocomposites.