Stabilization of α-chymotrypsin at air-water interface through surface binding to gold nanoparticle scaffolds

Enzyme-Adsorbed Chitosan Nanogel Particles as Edible Pickering Interfacial Biocatalysts and Lipase-Responsive Phase Inversion of Emulsions

Here, a simple food-grade Pickering emulsion system is prepared and adopted for biphasic biocatalytic reactions. The chitosan nanogels were prepared with strong dispersion of chitosan aggregates approaching neutral pH and then used as the particle emulsifiers to produce oil-in-water Pickering emulsions. The chitosan nanogel exhibited high affinity to negatively charged lipase. As a result of increasing the biphasic interfacial area and loading amount on the oil-water interface, the catalysis activity of lipase and recycling and pH stability were highly enhanced through colorimetric determination of p-nitrophenol (the hydrolysis product of p-nitrophenyl palmitate). A general strategy was proposed to obtain stimulus-responsive Pickering emulsions that can undergo phase inversion. The in situ modification of the wettability of chitosan nanogel could be attributed to the interaction between nanogel and free fatty acids, which was triggered by lipase hydrolysis. This would permit a rapid and controlled release of hydrophobic active components in response to enzymatic triggers.

ation of the igh ensitiv Label-Free

A highly sensitive electrochemical biosensor with a signal amplification platform of electrodeposited gold nanoparticle (AuNP) has been developed and characterized. The sizes of the synthesized AuNP were found to be critical for the performance of biosensor in which the sizes were dependent on HAuCl₄ and acid concentrations; as well as on scan cycles and scan rates in the gold electro-reduction step. Systematic investigations of the adsorption of proteins with different sizes from aqueous electrolyte solution onto the electrodeposited AuNP surface were performed with a potentiometric method and calibrated by design of experiment (DOE). The resulting amperometric glucose biosensors was demonstrated to have a low detection limit (> 50M) and a wide linear range after optimization with AuNP electrodeposition.

Gold nanoparticle-based colorimetric biosensors

Gold nanoparticles (AuNPs) provide excellent platforms for the development of colorimetric biosensors as they can be easily functionalised, displaying different colours depending on their size, shape and state of aggregation. In the last decade, a variety of biosensors have been developed to exploit the extent of colour changes as nano-particles (NPs) either aggregate or disperse, in the presence of analytes. Of critical importance to the design of these methods is that the behaviour of the systems has to be reproducible and predictable. Much has been accomplished in understanding the interactions between a variety of substrates and AuNPs, and how these interactions can be harnessed as colorimetric reporters in biosensors. However, despite these developments, only a few biosensors have been used in practice for the detection of analytes in biological samples. The transition from proof of concept to market biosensors requires extensive long-term reliability and shelf life testing, and modification of protocols and design features to make them safe and easy to use by the population at large. Developments in the next decade will see the adoption of user friendly biosensors for point-of-care and medical diagnosis as innovations are brought to improve the analytical performances and usability of the current designs. This review discusses the mechanisms, strategies, recent advances and perspectives for the use of AuNPs as colorimetric biosensors.

Nanoparticle probes for quantifying supramolecular determinants of biosurface affinity

Interactions between macromolecular systems and biosurfaces are complicated by both the complexity of these multivalent interactions and challenges in quantifying affinities. A library of gold nanoparticles (AuNPs) as multivalent probes is used to quantify biosurface affinity, using hair as a model targeted substrate.

Organic chemistry meets polymers, nanoscience, therapeutics and diagnostics

The atom-by-atom control provided by synthetic organic chemistry presents a means of generating new functional nanomaterials with great precision. Bringing together these two very disparate skill sets is, however, quite uncommon. This autobiographical review provides some insight into how my program evolved, as well as giving some idea of where we are going.

Enzyme-Functionalized PLGA Nanoparticles with Enhanced Mucus Permeation Rate

The surface functionalization of poly(lactide-co-glycolide) (PLGA) nanoparticles (NPs) with various proteolytic enzymes (i.e., trypsin, papain, bromelain) via a two-step carbodiimide coupling method is presented. Depending on the initial Enzyme:NPs ratio, enzyme loadings up to 4.0 wt.%, 4.4 wt.% and 5.34 wt.% were achieved for trypsin, papain and bromelain, respectively. All three conjugated enzymes partially maintained their enzymatic activity after their coupling reaction with the NPs. NPs functionalized with papain and bromelain exhibited a three-fold higher permeability in porcine intestinal mucus compared to nonfunctionalized NPs whereas those conjugated with trypsin showed an almost two-fold higher permeability value. Measurements of the diffusion rates of intestinal mucin, using a nuclear magnetic resonance (NMR) technique, further confirmed these observations, as the enzyme-functionalized NPs were proven to be capable of disrupting the mucin gel structure. According to the reported results, the coupling of proteolytic enzymes to the PLGA NPs' surface largely increases the NPs mucus permeability, thus making it a potentially important mucus permeation strategy.

Proteins at air-water interfaces: a coarse-grained model

We present a coarse-grained model to describe the adsorption and deformation of proteins at an air-water interface. The interface is introduced empirically in the form of a localized field that couples to a hydropathy scale of amino acids. We consider three kinds of proteins: protein G, egg-white lysozyme, and hydrophobin. We characterize the nature of the deformation and the orientation of the proteins induced by their proximity to and association with the interface. We also study protein diffusion in the layer formed at the interface and show that the diffusion slows with increasing concentration in a manner similar to that for a colloidal suspension approaching the glass transition.

Facile co-assembly process to generate core-shell nanoparticles with functional protein corona

A simple and robust protocol to maintain the structural feature of polymer-protein core-shell nanoparticles (PPCS-NPs) is developed based on the synergistic interactions between proteins and functional polymers. Using the self-assembly method, a broad range of proteins can be assembled to the selective water-insoluble polymers containing pyridine groups. The detailed analysis of the PPCS-NPs structure was conducted using FESEM and thin-sectioned TEM. The results illustrated that the protein molecules are located on the corona of the PPCS-NPs. While proteins are displacing between water and polymer to minimize the interfacial energy, the polymer offers a unique microenvironment to maintain protein structure and conformation. The proposed mechanism is based on a fine balance between hydrophobicity and hydrophilicity, as well as hydrogen bonding between proteins and polymer. The PPCS-NPs can serve as a scaffold to incorporate both glucose oxidase (GOX) and horseradish peroxidase (HRP) onto a single particle. Such a GOX-HRP bienzymatic system showed a ~20% increase in activity in comparison to the mixed free enzymes. Our method therefore provides a unique platform to preserve protein structure and conformation and can be extended to a number of biomolecules.

Engineering cytochrome-modified silica nanoparticles to induce programmed cell death

A low native membrane permeability and ineffective access to the cellular cytosol, together with aggressive proteolytic degradation, often severely hampers the practical application of any therapeutic protein or antibody. Through engineering the charging profile of mesoporous silica nanoparticles, cellular uptake and subsequent subcellular distribution can be controlled. We show herein that programmed cell death can subsequently be induced across a population of cancer cells with remarkable efficacy on conjugating a specific caspase-cascade-activating cytochrome to such cytosol-accessing particles.

Interaction of human arylamine N-acetyltransferase 1 with different nanomaterials

Humans are exposed to nanoparticles in the environment as well as those in nanomaterials developed for biomedical applications. However, the safety and biologic effects of many nanoparticles remain to be elucidated. Over the past decade, our understanding of the interaction of proteins with various nanomaterials has grown. The protein corona can determine not only how nanoparticles interact with cells but also their biologic effects and toxicity. In this study, we describe the effects that several different classes of nanoparticles exert on the enzymatic activity of the cytosolic protein human arylamine N-acetyltransferase 1 (NAT1), a drug-metabolizing enzyme widely distributed in the body that is also responsible for the activation and detoxification of known carcinogens. We investigated three metal oxides (zinc oxide, titanium dioxide, and silicon dioxide), two synthetic clay nanoparticles (layered double hydroxide and layered silicate nanoparticles), and a self-assembling thermo-responsive polymeric nanoparticle that differ in size and surface characteristics. We found that the different nanoparticles induced very different responses, ranging from inhibition to marked enhancement of enzyme activity. The layered silicates did not directly inactivate NAT1, but was found to enhance substrate-dependent inhibition. These differing effects demonstrate the multiplicity of nanoparticle-protein interactions and suggest that enzyme activity may be compromised in organs exposed to nanoparticles, such as the lungs or reticulo-endothelial system.

Nano meets biology: structure and function at the nanoparticle interface

Understanding the interactions of nanomaterials with biosystems is a critical goal in both biomedicine and environmental science. Engineered nanoparticles provide excellent tools for probing this interface. In this feature article, we will summarize one of the themes presented in our recent Langmuir lecture discussing the use of monolayer design to understand and control the interactions of nanoparticles with biomolecules and cells.

Beauty is skin deep: a surface monolayer perspective on nanoparticle interactions with cells and bio-macromolecules

Surface recognition of biosystems is a critical component in the development of novel biosensors and delivery vehicles, and for the therapeutic regulation of biological processes. Monolayer-protected nanoparticles present a highly versatile scaffold for selective interaction with bio-macromolecules and cells. Through the engineering of the monolayer surface, nanoparticles can be tailored for surface recognition of biomolecules and cells. This review highlights recent progress in nanoparticle-bio-macromolecule/cellular interactions, emphasizing the effect of the surface monolayer structure on the interactions with proteins, DNA, and cell surfaces. The extension of these tailored interactions to hybrid nanomaterials, biosensing platforms, and delivery vehicles is also discussed.

Synthesis of alpha-chymotrypsin/polymer composites by a reverse micelle/gas antisolvent method

Alpha-chymotrypsin (CT)/polyvinylpyrrolidone (PVP) composites was synthesized by combination of reverse micelles and CO(2). In this method, the two reverse micellar solutions containing CT and PVP, respectively, were first mixed, then compressed CO(2) was used as an antisolvent to precipitate the CT and PVP simultaneously and CT/PVP composites were successfully prepared. The morphology of the obtained CT/PVP composites was characterized by transmission electron microscopy (TEM). The FTIR spectra of the composites showed that there was interaction between CT and PVP. The storage activity of the enzyme immobilized on the polymer by this method was higher than that of the pure enzyme. This method has some advantages and can be easily applied to the synthesis of some other enzyme/polymer composites.