RESUMEN
The successful fabrication of biosensors is greatly limited by the immobilization of their bioreceptor, thus we propose a facile and reproducible two-step method to modify graphite electrodes with a bacterial laccase, relying on a fast and controllable potentiostatic process to coat graphite surfaces with biomolecule-compatible thin films of polynorepinephrine (ePNE) and polydopamine (ePDA). Both polymers, synthesized with a similar thickness, were functionalized with bacterial laccase, displaying distinct electrochemical transducing behaviours at pH 5.0 and 7.0. ePNE layer enables adequate electron transfer of anionic and cationic species in acidic and neutral media, whereas transduction across ePDA strongly depends on pH and redox probe charge. ePNE stands out by improving the amperometric responses of the biosensing interface towards a phenolic acid (gallic acid) and a flavonoid (catechin), in respect to ePDA. The optimal graphite/ePNE/laccase interface outperforms biosensing interfaces based on fungal laccases at neutral pH, displaying detection sensitivities of 104 and 14.4 µA cm-2 mM-1for gallic acid and catechin, respectively. The fine synthetic control of the ePNE bio-inspired transduction layer and the use of an alkaliphilic bacterial laccase enabled the construction of an amperometric biosensing interface with extended pH range of polyphenols detection present in food products and agro-industrial waste.
RESUMEN
Topochemical engineering of hybrid materials is an efficient way of synthesizing hydrophobic and highly tensile fiber composites by utilizing the intermolecular hydrogen bonds in natural materials. These materials include wood pulp fibers, abietic acid (resin acid) and inexpensive metal salts. In this work, a hybrid composite was created using bleached and unbleached kraft pulp fibers as cellulose platform. In situ co-precipitation of layered double hydroxide (LDH) was performed to grow LDH crystals on the surface of the cellulose fibers, followed by the immobilization of abietic acid (AA) on LDH-grafted cellulose. Here we aimed to benefit from the hydrogen bonding between -OH groups of cellulose and LDH, and the -COOH groups of AA to obtain charge-directed assembly of one material on the other material. Thus, composite hybrid fibers (C-HF) were produced and then characterized by optical (CAM), spectroscopic (XRD, IR) and microscopic techniques (SEM) to determine their average length and distribution, structure and purity, bonding, and morphology. These fibers further were tested for water contact angle (hydrophobicity), oil absorption (lipophilicity), tensile strength and ISO brightness measurements. The performance of C-HF was compared with unmodified reference fibers (REF), fibers composed with only AA (C-F) and LDH-hybridized fibers (HF). The results revealed a variety of correlations between materials and their properties due to characteristic surface morphology, functional groups, hydrogen bonding and natural co-materials such as lignin and hemicelluloses. Attractive and repulsive van der Waals forces between material entities play a crucial role in the resulting properties.
