Abstract
Hydrogels have become a promising research focus because of their potential for biomedical application. Here we explore the long-range, electrostatic interactions by following the effect of trans-acting (pH) and cis-acting factors (peptide mutation) on the formation of Au-phage hydrogels. These bioinorganic hydrogels can be generated from the bottom-up assembly of Au nanoparticles (Au NP) with either native or mutant bacteriophage (phage) through electrostatic interaction of the phage pVIII major capsid proteins (pVIII). The cis-acting factor consists of a peptide extension displayed on the pVIII that mutates the phage. Our results show that pH can dictate the direct-assembly and stability of Au-phage hydrogels in spite of the differences between the native and the mutant pVIII. The first step in characterizing the interactions of Au NP with phage was to generate a molecular model that identified the charge distribution and structure of the native and mutant pVIII. This model indicated that the mutant peptide extension carried a higher positive charge relative to the native pVIII at all pHs. Next, by monitoring the Au-phage interaction by means of optical microscopy, elastic light scattering, fractal dimension analysis as well as Uv-vis and surface plasmon resonance spectroscopy, we show that the positive charge of the mutant peptide extension favors the opposite charge affinity between the phage and Au NP as the pH is decreased. These results show the versatility of this assembly method, where the stability of these hydrogels can be achieved by either adjusting the pH or by changing the composition of the phage pVIII without the need of phage display libraries.
Highlights
Bottom-up nanoparticle assembly has recently been considered as a model for the development of enabling technologies in bioengineering and biomedical research [1,2]
Phage charge computation Because many of the phage physical-chemical properties are defined by the structure and charge of the pVIII displayed peptides, the first step in characterizing the Au nanoparticles (Au NP) interaction with phage was to generate a molecular model which identified the charge distribution and structure of the native and mutant pVIII protein (Fig. 2A and B)
(Fig. 2B) is in qualitative agreement with the charge estimated from the primary sequence of the peptide extension (Fig. 2A)
Summary
Bottom-up nanoparticle assembly has recently been considered as a model for the development of enabling technologies in bioengineering and biomedical research [1,2]. An alternative approach to the controlled assembly of nanoparticles onto phage has been presented in which peptide selection for metal binding is performed through display on the pIII minor capsid protein (pIII) followed by genetic manipulation of the phage’s pVIII to display the selected peptide [4,5] Both the native pVIII and the library-selected amino acid sequences of the metal-binding peptides show a low frequency of the typical amino acids that have the highest affinity for metals [8,9], such as histidines and cysteines [10,11,12]. By adjusting the pH, differences between native or mutant major capsid can be offset assuring hydrogel assembly with either phage system
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
