Synthetic and bio-hybrid nanoscale layers with tailored surface functionalities

Abstract We examine the prospective routes for the design of synthetic/biomacromolecular/inorganic film assemblies for photothermal cell based on biomimetic approach. We demonstrate examples of channel proteins immobilized onto surfaces of silicon single crystals modified with Langmuir-Blodgett and self-assembled monolayers. These proteins can be immobilized in intact, closed-pore conformation. Their state within photosensitive monolayers can be controlled by the photoisomerization reaction triggered by UV light

Investigations on the micellization of amphiphilic dendritic copolymers: from unimers to micelles

Since the micellization kinetics is influenced by polymer structure, the spherical three-dimensional topology of amphiphilic dendritic copolymers (ADPs) which hinders the phase separation during micellization is assumed to make the micellization kinetics different. In the literatures, most of the attention has been paid to the morphology transition or the morphology at equilibrium and the micellization kinetics of ADPs is rarely reported. In this study, the micellization processes of amphiphilic dendritic copolymers from unimers to the final equilibrium micelles were monitored by laser light scattering. Based on the closed association mechanism, the thermodynamics of micellization was analysed. The negative thermodynamic quantities indicate that the micellization of ADPs is driven by enthalpy. Based on the change of scattering intensity and hydrodynamic radius (Rh) with time, the detailed micellization kinetics was analysed, which contains two steps. By controlling the temperature and type of solvent, a system in which the concentration has little influence on Rh is obtained. The relaxation times of the two steps decrease with concentration, indicating that at higher concentration the rate of micellization is quicker. With the increasing mass fraction of the hydrophobic part, the relaxation times decrease and the driving force of micellization increases

Attaching DNA to Nanoceria: Regulating Oxidase Activity and Fluorescence Quenching

This document is the Accepted Manuscript version of a Published Work that appeared in final form in Applied Materials and Interfaces copyright © American Chemical Society after peer review and technical editing by publisher. To access the final edited and published work see Pautler, R., Kelly, E. Y., Huang, P.-J. J., Cao, J., Liu, B., & Liu, J. (2013). Attaching DNA to Nanoceria: Regulating Oxidase Activity and Fluorescence Quenching. ACS Applied Materials & Interfaces, 5(15), 6820–6825. https://doi.org/10.1021/am4018863Cerium oxide nanoparticles (nanoceria) have recently emerged as a nanozyme with oxidase activity. In this work, we present a few important interfacial properties of nanoceria. First, the surface charge of nanoceria can be controlled not only by adjusting pH but also by adsorption of simple inorganic anions. Adsorption of phosphate and citrate gives negatively charged surface over a broad pH range. Second, nanoceria adsorbs DNA via the DNA phosphate backbone in a sequence-independent manner; DNA adsorption inhibits its oxidase activity. Other anionic polymers display much weaker inhibition effects. Adsorption of simple inorganic phosphate does not have the inhibition effect. Third, nanoceria is a quencher for many fluorophores. These discoveries provide an important understanding for further use of nanoceria in biosensor development, materials science, and nanotechnology.University of Waterloo || Canadian Foundation for Innovation || Natural Sciences and Engineering Research Council || Ontario Ministry of Research and Innovation |

Cellulose: from biocompatible to bioactive material

International audienceSince the papyri, cellulose has played a significant role in human culture, especially as paper. Nowadays, this ancient product has found new scientific applications in the expanding sector of paper-based technology. Among paper-based devices, paper-based biosensors raise a special interest. The high selectivity of biomolecules for target analytes makes these sensors efficient. Moreover, simple paper-based detection devices do not require hardware or specific technical skill. They are inexpensive, rapid, user-friendly and therefore highly promising for providing resource-limited settings with point-of-care diagnostics. The immobilization of biomolecules onto cellulose is a key step in the development of these sensing devices. Following an overview of cellulose structural features and physicochemical properties, this article reviews current techniques for the immobilization of biomolecules on paper membranes. These procedures are categorized into physical, biological and chemical approaches. There is no universal method for biomolecule immobilization. Thus, for a given paper-based biochip, each strategy can be considered

Whole-cell paper strip biosensors to semi-quantify tetracycline antibiotics in environmental matrices

A novel, low-cost, and portable paper strip biosensor was developed for the detection of tetracycline antibiotics. Escherichia coli/pMTLacZ containing the tetracycline-mediated regulatory gene used as recognition elements with β-galactosidase as the reporter protein was designed and applied to cheap and portable Whatman filter paper as the carrier to prepare this paper strip biosensor. The detection process was optimized by using EDTA and polymyxin B as a sensitizer to improve the accuracy of detection for complicated matrices. The paper strip biosensor was suitable for tetracycline concentrations in the range of 75–10000 μg/L in water and 75–7500 μg/L in soil extracts. Detection limits of 5.23–17.1 μg/L for water and 5.21–35.3 μg/kg for the EDTA soil extracts were achieved at a response time of 90 min. The standard deviation (SD) of detected values by the biosensor paper strip compared to those determined by HPLC was between 13.4 and 59.6% for tetracycline and 2.01–33.5% for oxytetracycline in water and was between 6.22 and 72.8% for tetracycline and 5.90–43.4% for oxytetracycline in soil. This suggests that the paper strip biosensor was suitable for detecting both tetracycline and oxytetracycline in water, and could provide a suitable detection for extractable oxytetracycline in soils. Therefore, this biosensor provides a simple, economical, and portable piece of field kit for on-site monitoring of tetracyclines in a variety of environmental samples, such as pond water and agricultural soil that are susceptible to tetracycline pollution from feed additives and fertilization with livestock manure

Shell design of functional hyperbranched molecules for surface assembly

This study explores possibilities of obtaining of unique self-assembled, nanofibrillar structures from amphiphilic hyperbranched molecules on solid surfaces. To achieve this, we explore the multifunctional properties of hyperbranched polymers which are determined by the nature of the end groups and structure of the chemical composition of the core unit. We established that the combination of hydrophobic interactions and multiple hydrogen bonding events added to the dendritic core structure is responsible for stable assembling into nanofibrillar morphology at the air-water interface at both the nano and at microscales and determined compositional boundaries of this phenomenon;The core-shell architecture of the amphiphilic dendritic molecules suggested here provides exceptional stability of one-dimensional nanofibrillar structures. The critical condition for the formation of the nanofibrillar structures is the presence of both alkyl tails in the outer shell as the hydrophobic component and either amine or carboxyl groups in the shell as the hydrophilic component. The multiple intermolecular hydrogen bonding and polar interactions between flexible cores stabilize these nanofibers and make them robust against surface pressure and solvents. Moreover, discovered assembled nano-fibers formed by hyperbranched polymers have been used for templating of silver nanoparticles via growth from water subphase. We observed that hyperbranched polymers scaffolds can create aligned nanoparticle arrays, and also effectively control size of the particles to about 3 nm.</p

Organic self-assembled monolayers for reconstitution of ion channels on single crystal silicon

"The major goal of this research is to understand design principles of interfaces, suitable for the reconstitution the ion channel membrane proteins. In the present work, we focused on the immobilization of two channel proteins, α-Hemolysin from Staphylococcus aureus and Mechanosensitive Ion Channel of Large Conductance (MscL) from Salmonella typhimurium, onto single crystal silicon substrates (silicon wafers). High-resolution atomic force microscopy (AFM) was utilized as a tool for the monitoring of the molecular conformations of the ion channels after immobilization. As observed, α-Hemolysin was adsorbed onto bare silicon in collapsed state, while adsorption of MscL resulted in unraveling of the protein. LB deposition of proteins embedded in lipid monolayer reduced denaturation of the proteins on silicon surface, due to reduced surface energy. Octadecyltimethoxy silane (ODTMS) self-assembled monolayers (SAMs) were used as a ""buffer layer analog"" of a lipid membrane. MscL was successfully reconstituted in these organic SAMs. Analysis of dimensions of the MscL displayed that the gating state and the molecular conformation of SAM-supported MscL can be controlled by variation of the surface energy of the supporting surface layer. Closed, intermediate, and open states were observed on surfaces with different surface tensions. Obtained results demonstrated an agreement with known molecular modeling data for gating mechanisms of the MscL protein in lipid membrane."</p