Formation and composition of adsorbates on hydrophobic carbon surfaces from aqueous laccase-maltodextrin mixture suspension

Abstract

A robust procedure for the surface bio-functionalization of carbon surfaces was developed. It consists on the modification of carbon materials in contact with an aqueous suspension of the enzyme laccase from Trametes versicolor and the lyophilization agent maltodextrin, with the pH value adjusted close to the isoelectric point of the enzyme. We report in-situ investigations applying Quartz Crystal Microbalance with Dissipation (QCM-D) for carbon-coated sensor surfaces and, moreover, ex-situ measurements with static contact angle measurements, X-ray Photoelectron Spectroscopy (XPS) and Scanning Force Microscopy (SFM) for smooth Highly Oriented Pyrolytic Graphite (HOPG) substrates, for contact times between the enzyme formulation and the carbon material surface ranging from 20 s to 24 h. QCM-D studies reveals the formation of rigid layer of biomaterial, a few nanometers thin, which shows a strongly improved wettability of the substrate surface upon contact angle measurements. Following spectroscopic characterization, these layers are composed of mixtures of laccase and maltodextrin. The formation of these adsorbates is attributed to attractive interactions between laccase, the maltodextrin-based lyophilization agent and the hydrophobic carbon surfaces; a short-term contact between the aqueous laccase mixture suspension and HOPG surfaces is shown to merely result in de-wetting patterns influencing the results of contact angle measurements. The new enzyme-based surface modification of carbon-based materials is suggested to be applicable for the improvement of not only the wettability of low energy substrate surfaces with fluid formulations like coatings or adhesives, but also their adhesion in contact with hardened polymers

Functionalization of hydrophobic surfaces with antimicrobial peptides immobilized on a bio-interfactant layer

“…The peak at 286.3 AE 0.1 eV is associated with amine-like C*-N; the signal related to C*-O from alcohol/alkoxy groups is characterized by a 0.5 eV higher binding energy; the peak centered at 288.2 AE 0.1 eV is characteristic of amide groups (-NH-C*]O); and, nally, the peak at 289.0 AE 0.1 eV is correlated with carboxyl groups. 25 The layer thickness calculated following the protocol described by Corrales et al is approximately 1 nm and 2.7 nm for LM and LM/Tet-124-G-BrPh-DOPA-G layers on PS, respectively. 25 Surface topography and roughness of layers were studied using AFM.…”

“…25 The layer thickness calculated following the protocol described by Corrales et al is approximately 1 nm and 2.7 nm for LM and LM/Tet-124-G-BrPh-DOPA-G layers on PS, respectively. 25 Surface topography and roughness of layers were studied using AFM. Initially, molecular dimensions of the laccase and peptide measured upon adsorption on HOPG as a model hydrophobic at surface.…”

Extracellular micro and nanostructures forming the velvet worm solidified adhesive secretion

“…Therefore, it shows the nanoparticles forming globules and fibres. Phase changes could be associated with differences in composition, adhesion, friction, and viscoelasticity properties, with respect to the surrounding matrix [37]. Figures S11(C) and (D) shows agglomeration of this globules after adding water.…”

“…The nanometric particles arrangement observed in figure 8(D) could suggest an organization in a 2D crystal like structure (XY); forming a high density coverage film. Some proteins as hydrophobin can form crystalline structure and organize preferentially in 2D arrangements [37]. Figure S10 shows an AFM cross-section of the globular particles that are more exposed to the surface; the nano-roughness produced by the nanoparticles and the amorphous matrix is 2.9 ± 0.8 nm.…”

Bio-interfactants as double-sided tapes for graphene oxide

“…The adaptable nature of the selected bio-interfactants allows an essentially physical coupling of GO during the immobilisation on several distinct substrates, such as fused quartz, borosilicate glass, and polyimide (PI). The bio-interfactants used in this study were strategically selected in view of their versatile adsorption under diverse conditions [39][40][41][42][43][44][45][46][47] and their potential key interactions with GO. 35 They play an important role in the dynamics of thermal reduction of GO by allowing chemical selectivity during decomposition and anchoring of the rGO, and resulting in a peculiar rippled topography, following the classification used by Deng et al 48 The goal of this work is to explore the advantages of using bio-interfactants to attach graphene oxide in a coplanar arrangement on surfaces and investigate the processes that allow this nanoassembly configuration before and after the thermal reduction towards graphene.…”