br Acknowledgements The research work has been fully support

Acknowledgements The research work has been fully supported by the Higher Education Commission, Pakistan with Support initiative Grant No. IRSIP 21 Ps 04. I would like to thank the Department of Applied sciences of UWE, Bristol,UK for providing access to their lab facilities.
Introduction The controlled assembly of bio-hybrid nanostructured materials is an emerging research area due to their potential applications in bioengineering, biosensing and biomedical research. Among the wide variety of biological scaffolds, filamentous bacteriophages have recently attracted much attention for the development of accurately positioned nano-biotemplates, since the phage particle can be modified to form hetero-complexes with organic or inorganic nanomaterials. Ultimately, filamentous bacteriophage M13 represent attractive alternatives to antibodies or synthetic peptides, for developing new nanobiohybrid materials [1–4], due to their robustness, resistance to heat and to many organic solvent (such as 50% methanol [5] and 30% DMSO [6]) buy Tenofovir Disoproxil and alkali as well as a low-cost production [7,8]. Phage display is a high-throughput biotechnique that allows the presentation of exogenous peptides on the surface of one filamentous phage. This technology involves the introduction of exogenous peptide sequences into a location in the genome of the phage capsid proteins such as pVIII and pIII [9]. Thus, the main advantage of phage display is the enormous diversity of variant peptides that can be represented. Random phage libraries, in fact, include billion phage clones expressing on their surface more than 1012–1014 different peptides [10]. The library is used to select specific phage clones that interact with particular targets, generating molecular probes with high affinity and selectivity [11–14]. More recently, novel strategies were developed to functionalize gold and silver nanoparticles with different Raman reporter molecules for targeting specific ligands such as peptides, proteins, antibodies, Deoxyribonucleic acid (DNA) and antibody fragments [15–19]. Nevertheless, some drawback still remain such as the availability to identify selectively and with high reproducibility probes that can act like SERS nanotags for the recognition of target cells. Taking into account the above described properties, phage-metallic nanoparticles networks are considered appropriate systems to integrate the unique signal-reporting properties of the metallic nanoparticles while preserving the biological properties of phages [20]. The surface of each filamentous bacteriophage M13 virus consists of about 2700 copies of a major coat protein which package a single-stranded circular viral DNA into a rod with a total length of 880nm and a diameter of 6.6nm [21]. This major coat protein is a charged α-helix consisting of 50 residues, and constitutes the bulk of the total charge on the virus [22]. Approximately six of the 50 residues (and the amino terminus) are solution accessible and contribute to the surface charge on M13. By changing the pH, change the protonation states of the amino acids on the virus major coat protein, thereby modifying the surface charge density [21]. Clearly the coat protein has the ability to adopt its conformation, which allows the protein to exist in distinctly different environments, such as the phage filament, the I form phage, the S-form phage, and the membrane-bound form [23]. This is possible because of the amphipathic nature of the coat protein so that it can have both hydrophobic and hydrophilic interactions with its environment. This property gives the protein a large conformational space that allows very flexible protein aggregational schemes.
Materials and methods
Conclusions M13 bacteriophage can serve as a versatile and multifunctional material building block due to the ease of its genetic manipulation and its monodisperse filamentous shape. We have investigated some of the variables that influence the organization and assembly of phage with silver nanoparticles. Our result suggests that, the AgNPs-phage assembly are not only directed by opposite-charge interaction, but a significant role is played by the pH and the ion-type buffer solution. We found that the organization and assembly of laser prepared AgNPs and phage was favorite significantly at pH above the phage pI and using saline buffer (with presences of Na+ and Cl−) that form saline bridge between AgNPs and phage. The streamlined methodology, reported in this study, may serve as a complementary approach to understand and to gain control on the assembly of active phage-nanoparticles system. These networks could find application in the biomedical field of advanced biosensing, tissue engineering, bioelectronic systems and targeted gene and drug delivery.