Interactions of proteins with metal-based nanoparticles from a point of view of analytical chemistry - Challenges and opportunities

Interactions of proteins with nanomaterials draw attention of many research groups interested in fundamental phenomena. However, alongside with valuable information regarding physicochemical aspects of such processes and their mechanisms, they more and more often prove to be useful from a point of view of bioanalytics. Deliberate use of processes based on adsorption of proteins on nanoparticles (or vice versa) allows for a development of new analytical methods and improvement of the existing ones. It also leads to obtaining of nanoparticles of desired properties and functionalities, which can be used as elements of analytical tools for various applications. Due to interactions with nanoparticles, proteins can also gain new functionalities or lose their interfering potential, which from perspective of bioanalytics seems to be very inviting and attractive. In the framework of this article we will discuss the bioanalytical potential of interactions of proteins with a chosen group of nanoparticles, and implementation of so driven processes for biosensing. Moreover, we will show both positive and negative (opportunities and challenges) aspects resulting from the presence of proteins in media/samples containing metal-based nanoparticles or their precursors.

A Facile Colorimetric Sensor for 6-Mercaptopurine Based on Silver Nanoparticles

A facile colorimetric method was developed for detecting 6-mercaptopurine (6-MP) using silver nanoparticles (AgNPs). The addition of 6-MP to AgNPs led to the aggregation of AgNPs with a color change from yellow to brown. The ratio between the absorbance at 394 and 530 nm (A394/A530) was used for a quantitative analysis of 6-MP. A linear range of 0 - 0.5 μM was obtained with a detection limit of 10 nM. The developed method is cost-effective and simple.

Screening and characterisation of CdTe/CdS quantum dot-binding peptides for material surface functionalisation

Quantum dots (QDs) are promising nanomaterials due to their unique photophysical properties. For them to be useful in biological applications, the particle surface generally needs to be conjugated to biological molecules, such as antibodies. In this study, we screened CdTe/CdS QD-binding peptides from a phage display library as linkers for simple and bio-friendly QD modification. Among five QD-binding peptide candidates, a series of truncated peptides designed from two high-affinity peptides were subjected to an array-based binding assay with QDs to assess their functional core sequences and characteristics. Linking these isolated, shortened peptides (PWSLNR and SGVYK) with an antibody-binding peptide (NKFRGKYK) created dual-functional peptides that are capable of QD surface functionalisation by antibodies. Consequently, the dual-functional peptides could mediate anti-CD9 antibody functionalisation onto CdTe/CdS QD surface; CD9 protein imaging of cancer cells was also demonstrated. Our proposed peptides offer an effective vehicle for QD surface functionalisation in biological applications.

Rational screening of biomineralisation peptides for colour-selected one-pot gold nanoparticle syntheses

Biomineralisation peptides that facilitate the one-pot synthesis of gold nanoparticles (AuNPs) with selected optical properties, were screened using a coherent peptide-spotted array consisting of a AuNP binding peptide library. As the biomineralised AuNPs were captured on each peptide spot, analysis of the images provided information on their collective optical properties.

Highly sensitive detection of antibodies in a soft bioactive three-dimensional bioorthogonal hydrogel

This three-dimensional detection method of antibodies offers a high sensitivity and good biomolecule stability for new biosensing devices.

Multi-coloration of Calixarene-coated Silver Nanoparticles for the Visual Discrimination of Metal Elements

Upon mixing with metal ions such as Cd^II, Tb^III, Cu^II, Ni^II, Pb^II, Zn^II, and Co^II at pH 10.0, solutions of silver nanoparticles (AgNPs) coated with calix[4]arene-p-tetrasulfonate (CAS-AgNP) exhibited multi-coloration from yellow to orange, violet, and green, depending on the metal elements present, which allowed for visual discrimination of the ions. This is contrary to the AgNP sensors exhibiting a uniform color change from yellow to red upon binding of a receptor molecules at the surface of AgNPs to an analyte. The TEM images of the samples obtained from the resultant solution showed two regions. First, a region where CAS-AgNPs assembled on the surface of the metal hydroxides. The size of the hydroxide crystals varied from 50 to 200 nm with the type of metal element present, and roughly correlated with the extinction band of the aggregated AgNPs. Second, the amorphous region in which CAS-AgNPs dispersed randomly. The difference in the amount of the crystal region and the area seemed to lead to the multi-coloration.