Phage display for detection of biological threat agents

Phage Display's Prospects for Early Diagnosis of Prostate Cancer

Prostate cancer (PC) is the second most diagnosed cancer among men. It was observed that early diagnosis of disease is highly beneficial for the survival of cancer patients. Therefore, the extension and increasing quality of life of PC patients can be achieved by broadening the cancer screening programs that are aimed at the identification of cancer manifestation in patients at earlier stages, before they demonstrate well-understood signs of the disease. Therefore, there is an urgent need for standard, sensitive, robust, and commonly available screening and diagnosis tools for the identification of early signs of cancer pathologies. In this respect, the "Holy Grail" of cancer researchers and bioengineers for decades has been molecular sensing probes that would allow for the diagnosis, prognosis, and monitoring of cancer diseases via their interaction with cell-secreted and cell-associated PC biomarkers, e.g., PSA and PSMA, respectively. At present, most PSA tests are performed at centralized laboratories using high-throughput total PSA immune analyzers, which are suitable for dedicated laboratories and are not readily available for broad health screenings. Therefore, the current trend in the detection of PC is the development of portable biosensors for mobile laboratories and individual use. Phage display, since its conception by George Smith in 1985, has emerged as a premier tool in molecular biology with widespread application. This review describes the role of the molecular evolution and phage display paradigm in revolutionizing the methods for the early diagnosis and monitoring of PC.

Investigation of Peptides for Molecular Recognition of C-Reactive Protein-Theoretical and Experimental Studies

We investigate the interactions between C-reactive protein (CRP) and new CRP-binding peptide materials using experimental (biological and physicochemical) methods with the support of theoretical simulations (computational modeling analysis). Three specific CRP-binding peptides (P2, P3, and P9) derived from an M13 bacteriophage have been identified using phage-display technology. The binding efficiency of the peptides exposed on phages toward the CRP protein was demonstrated via biological methods. Fibers of the selected phages/peptides interact differently due to different compositions of amino acid sequences on the exposed peptides, which was confirmed by transmission electron microscopy. Numerical and experimental studies consistently showed that the P3 peptide is the best CRP binder. A combination of theoretical and experimental methods demonstrates that identifying the best binder can be performed simply, cheaply, and fast. Such an approach has not been reported previously for peptide screening and demonstrates a new trend in science where calculations can replace or support laborious experimental techniques. Finally, the best CRP binder─the P3 peptide─was used for CRP recognition on silicate-modified indium tin oxide-coated glass electrodes. The obtained electrodes exhibit a wide range of operation (1.0-100 μg mL-1) with a detection limit (LOD = 3σ/S) of 0.34 μg mL-1. Moreover, the dissociation constant Kd of 4.2 ± 0.144 μg mL-1 (35 ± 1.2 nM) was evaluated from the change in the current. The selectivity of the obtained electrode was demonstrated in the presence of three interfering proteins. These results prove that the presented P3 peptide is a potential candidate as a receptor for CRP, which can replace specific antibodies.

Recombinant antibodies by phage display for bioanalytical applications

Antibody phage display, aimed at preparing antibodies to defined antigens, is a useful replacement for hybridoma technology. The phage system replaces all work stages that follow animal immunization with simple procedures for manipulating DNA and bacteria. It enables the time needed to generate stable antibody-producing clones to be shortened considerably, making the process noticeably cheaper. Antibodies prepared by phage display undergo several affinity selection steps and can be used as selective receptors in biosensors. This article briefly describes the techniques used in the making of phage antibodies to various antigens. The possibilities and prospects are discussed of using phage antibodies as selective agents in analytical systems, including biosensors.

Phage-Displayed Mimotopes of SARS-CoV-2 Spike Protein Targeted to Authentic and Alternative Cellular Receptors

The evolution of the SARS-CoV-2 virus during the COVID-19 pandemic was accompanied by the emergence of new heavily mutated viral variants with increased infectivity and/or resistance to detection by the human immune system. To respond to the urgent need for advanced methods and materials to empower a better understanding of the mechanisms of virus’s adaptation to human host cells and to the immuno-resistant human population, we suggested using recombinant filamentous bacteriophages, displaying on their surface foreign peptides termed “mimotopes”, which mimic the structure of viral receptor-binding sites on the viral spike protein and can serve as molecular probes in the evaluation of molecular mechanisms of virus infectivity. In opposition to spike-binding antibodies that are commonly used in studying the interaction of the ACE2 receptor with SARS-CoV-2 variants in vitro, phage spike mimotopes targeted to other cellular receptors would allow discovery of their role in viral infection in vivo using cell culture, tissue, organs, or the whole organism. Phage mimotopes of the SARS-CoV-2 Spike S1 protein have been developed using a combination of phage display and molecular mimicry concepts, termed here “phage mimicry”, supported by bioinformatics methods. The key elements of the phage mimicry concept include: (1) preparation of a collection of p8-type (landscape) phages, which interact with authentic active receptors of live human cells, presumably mimicking the binding interactions of human coronaviruses such as SARS-CoV-2 and its variants; (2) discovery of closely related amino acid clusters with similar 3D structural motifs on the surface of natural ligands (FGF1 and NRP1), of the model receptor of interest FGFR and the S1 spike protein; and (3) an ELISA analysis of the interaction between candidate phage mimotopes with FGFR3 (a potential alternative receptor) in comparison with ACE2 (the authentic receptor).

Improved Light Harvesting of Fiber-Shaped Dye-Sensitized Solar Cells by Using a Bacteriophage Doping Method

Fiber-shaped solar cells (FSCs) with flexibility, wearability, and wearability have emerged as a topic of intensive interest and development in recent years. Although the development of this material is still in its early stages, bacteriophage-metallic nanostructures, which exhibit prominent localized surface plasmon resonance (LSPR) properties, are one such material that has been utilized to further improve the power conversion efficiency (PCE) of solar cells. This study confirmed that fiber-shaped dye-sensitized solar cells (FDSSCs) enhanced by silver nanoparticles-embedded M13 bacteriophage (Ag@M13) can be developed as solar cell devices with better PCE than the solar cells without them. The PCE of FDSSCs was improved by adding the Ag@M13 into an iodine species (I⁻/I₃⁻) based electrolyte, which is used for redox couple reactions. The optimized Ag@M13 enhanced FDSSC showed a PCE of up to 5.80%, which was improved by 16.7% compared to that of the reference device with 4.97%.

Modernization of Control of Pathogenic Micro-Organisms in the Food-Chain Requires a Durable Role for Immunoaffinity-Based Detection Methodology-A Review

Food microbiology is deluged by a vastly growing plethora of analytical methods. This review endeavors to color the context into which methodology has to fit and underlines the importance of sampling and sample treatment. The context is that the highest risk of food contamination is through the animal and human fecal route with a majority of foodborne infections originating from sources in mass and domestic kitchens at the end of the food-chain. Containment requires easy-to-use, failsafe, single-use tests giving an overall risk score in situ. Conversely, progressive food-safety systems are relying increasingly on early assessment of batches and groups involving risk-based sampling, monitoring environment and herd/flock health status, and (historic) food-chain information. Accordingly, responsible field laboratories prefer specificity, multi-analyte, and high-throughput procedures. Under certain etiological and epidemiological circumstances, indirect antigen immunoaffinity assays outperform the diagnostic sensitivity and diagnostic specificity of e.g., nucleic acid sequence-based assays. The current bulk of testing involves therefore ante- and post-mortem probing of humoral response to several pathogens. In this review, the inclusion of immunoglobulins against additional invasive micro-organisms indicating the level of hygiene and ergo public health risks in tests is advocated. Immunomagnetic separation, immunochromatography, immunosensor, microsphere array, lab-on-a-chip/disc platforms increasingly in combination with nanotechnologies, are discussed. The heuristic development of portable and ambulant microfluidic devices is intriguing and promising. Tant pis, many new platforms seem unattainable as the industry standard. Comparability of results with those of reference methods hinders the implementation of new technologies. Whatever the scientific and technological excellence and incentives, the decision-maker determines this implementation after weighing mainly costs and business risks.

Viruses Masquerading as Antibodies in Biosensors: The Development of the Virus BioResistor

The 2018 Nobel Prize in Chemistry recognized in vitro evolution, including the development by George Smith and Gregory Winter of phage display, a technology for engineering the functional capabilities of antibodies into viruses. Such bacteriophages solve inherent problems with antibodies, including their high cost, thermal lability, and propensity to aggregate. While phage display accelerated the discovery of peptide and protein motifs for recognition and binding to proteins in a variety of applications, the development of biosensors using intact phage particles was largely unexplored in the early 2000s. Virus particles, 16.5 MDa in size and assembled from thousands of proteins, could not simply be substituted for antibodies in any existing biosensor architectures.Incorporating viruses into biosensors required us to answer several questions: What process will allow the incorporation of viruses into a functional bioaffinity layer? How can the binding of a protein disease marker to a virus particle be electrically transduced to produce a signal? Will the variable salt concentration of a bodily fluid interfere with electrical transduction? A completely new biosensor architecture and a new scheme for electrical transduction of the binding of molecules to viruses were required.This Account describes the highlights of a research program launched in 2006 that answered these questions. These efforts culminated in 2018 in the invention of a biosensor specifically designed to interface with virus particles: the Virus BioResistor (VBR). The VBR is a resistor consisting of a conductive polymer matrix in which M13 virus particles are entrained. The electrical impedance of this resistor, measured across 4 orders of magnitude in frequency, simultaneously measures the concentration of a target protein and the ionic conductivity of the medium in which the resistor is immersed. Large signal amplitudes coupled with the inherent simplicity of the VBR sensor design result in high signal-to-noise ratio (S/N > 100) and excellent sensor-to-sensor reproducibility. Using this new device, we have measured the urinary bladder cancer biomarker nucleic acid deglycase (DJ-1) in urine samples. This optimized VBR is characterized by extremely low sensor-to-sensor coefficients of variation in the range of 3-7% across the DJ-1 binding curve down to a limit of quantitation of 30 pM, encompassing 4 orders of magnitude in concentration.

CRP-binding bacteriophage as a new element of layer-by-layer assembly carbon nanofiber modified electrodes

Recently, bacteriophage particles have started to be applied as a new biomaterial for developing sensing platforms. They can be used as both a recognition element or/and as building blocks, template/scaffold. In this paper, we studied a bacteriophage selected through phage-display technology. The chosen bacteriophage acted as a building block for creating a carbon nanofiber-based electrode and as a new receptor/binding element that recognizes C-reactive protein (CRP) - one of the markers of inflammatory processes in the human body. The binding efficiency of the selected phage towards CRP is two orders of magnitude higher than in the wild type. We demonstrate that the phage-based sensor is selective against other proteins. Finally, we show that layer-by-layer methods are suitable for deposition of negatively charged phages (wild or CRP-binding) with positively charged carbon nanofibers for electrode surface modification. A three-layered electrode was successfully used for molecular recognition of CRP, and the molecular interactions were studied using electrochemical, biological, and optical methods, including microscopic and spectroscopic analyses.

Phage-Based Sensors in Medicine: A Review

Bacteriophages are interesting entities on the border of biology and chemistry. In nature, they are bacteria parasites, while, after genetic manipulation, they gain new properties, e.g., selectively binding proteins. Owing to this, they may be applied as recognition elements in biosensors. Combining bacteriophages with different transducers can then result in the development of innovative sensor designs that may revolutionize bioanalytics and improve the quality of medical services. Therefore, here, we review the use of bacteriophages, or peptides from bacteriophages, as new sensing elements for the recognition of biomarkers and the construction of the highly effective diagnostics tools.

Surface Display Technology for Biosensor Applications: A Review

Surface display is a recombinant technology that expresses target proteins on cell membranes and can be applied to almost all types of biological entities from viruses to mammalian cells. This technique has been used for various biotechnical and biomedical applications such as drug screening, biocatalysts, library screening, quantitative assays, and biosensors. In this review, the use of surface display technology in biosensor applications is discussed. In detail, phage display, bacterial surface display of Gram-negative and Gram-positive bacteria, and eukaryotic yeast cell surface display systems are presented. The review describes the advantages of surface display systems for biosensor applications and summarizes the applications of surface displays to biosensors.

Hierarchical Cluster Analysis of Medical Chemicals Detected by a Bacteriophage-Based Colorimetric Sensor Array

M13 bacteriophage-based colorimetric sensors, especially multi-array sensors, have been successfully demonstrated to be a powerful platform for detecting extremely small amounts of target molecules. Colorimetric sensors can be fabricated easily using self-assembly of genetically engineered M13 bacteriophage which incorporates peptide libraries on its surface. However, the ability to discriminate many types of target molecules is still required. In this work, we introduce a statistical method to efficiently analyze a huge amount of numerical results in order to classify various types of target molecules. To enhance the selectivity of M13 bacteriophage-based colorimetric sensors, a multi-array sensor system can be an appropriate platform. On this basis, a pattern-recognizing multi-array biosensor platform was fabricated by integrating three types of sensors in which genetically engineered M13 bacteriophages (wild-, RGD-, and EEEE-type) were utilized as a primary building block. This sensor system was used to analyze a pattern of color change caused by a reaction between the sensor array and external substances, followed by separating the specific target substances by means of hierarchical cluster analysis. The biosensor platform could detect drug contaminants such as hormone drugs (estrogen) and antibiotics. We expect that the proposed biosensor system could be used for the development of a first-analysis kit, which would be inexpensive and easy to supply and could be applied in monitoring the environment and health care.

Bio-hybrid gold nanoparticles as SERS probe for rapid bacteria cell identification

This study reports the utilization of engineered molecular networks between bacteriophage (or phage) and gold nanoparticles (AuNPs) prepared ablating a high purity gold target in water by nanosecond laser source. Gold colloids are assembled with P9b phage clone, displaying the specific peptide (QRKLAAKLT), able to bind P. aeruginosa. The single components and assembled systems were characterized by spectroscopic and electronic techniques, such as the conventional optical absorption and micro-Raman spectroscopies as well as the Dynamic Light Scattering (DLS) and Scanning Transmission Electron Microscopy (STEM) techniques. The performance of the AuNPs-phage assembly as substrate for Surface-Enhanced Raman Spectroscopy (SERS) was tested against the detection of the characteristics Raman vibrational features of the Pseudomonas aeruginosa bacteria.

Elastic continuum stiffness of contractile tail sheaths from molecular dynamics simulations

Contractile tails are key components of the biological nanomachinery involved in cell membrane puncturing, where they provide a means to deliver molecules and ions inside cells. Two intriguing examples of contractile tails are those from bacteriophage T4 and R2-pyocin. Although the two systems are different in terms of biological activity, they share a fascinatingly similar injection mechanism, during which the tail sheaths of both systems contract from a so-called extended state to around half of their length (the contracted state), accompanied by release of elastic energy originally stored in the sheath. Despite the great prevalence and biomedical importance of contractile delivery systems, many fundamental details of their injection machinery and dynamics are still unknown. In this work, we calculate the bending and torsional stiffness constants of a helical tail sheath strand of bacteriophage T4 and R2-pyocin, in both extended and contracted states, using molecular dynamics simulations of about one-sixth of the entire sheath. Differences in stiffness constants between the two systems are rationalized by comparing their all-atom monomer structures, changes in sheath architecture on contraction, and differences in interstrand interactions. The calculated coefficients indicate that the T4 strand is stiffer for both bending and torsion than the corresponding R2-pyocin strands in both extended and contracted conformations. The sheath strands also have greater stiffness in the contracted state for both systems. As the main application of this study, we describe how the stiffness constants can be incorporated in a model to simulate the dynamics of contractile nanoinjection machineries.

Highly ordered protein cage assemblies: A toolkit for new materials

Protein capsids are specialized and versatile natural macromolecules with exceptional properties. Their homogenous, spherical, rod-like or toroidal geometry, and spatially directed functionalities make them intriguing building blocks for self-assembled nanostructures. High degrees of functionality and modifiability allow for their assembly via non-covalent interactions, such as electrostatic and coordination bonding, enabling controlled self-assembly into higher-order structures. These assembly processes are sensitive to the molecules used and the surrounding conditions, making it possible to tune the chemical and physical properties of the resultant material and generate multifunctional and environmentally sensitive systems. These materials have numerous potential applications, including catalysis and drug delivery. This article is categorized under: Biology-Inspired Nanomaterials > Protein and Virus-Based Structures.

Phage-Based Artificial Niche: The Recent Progress and Future Opportunities in Stem Cell Therapy

Self-renewal and differentiation of stem cells can be the best option for treating intractable diseases in regenerative medicine, and they occur when these cells reside in a special microenvironment, called the "stem cell niche." Thus, the niche is crucial for the effective performance of the stem cells in both in vivo and in vitro since the niche provides its functional cues by interacting with stem cells chemically, physically, or topologically. This review provides a perspective on the different types of artificial niches including engineered phage and how they could be used to recapitulate or manipulate stem cell niches. Phage-based artificial niche engineering as a promising therapeutic strategy for repair and regeneration of tissues is also discussed.

Phage-based assay for rapid detection of bacterial pathogens in blood by Raman spectroscopy

Sepsis is a systemic inflammatory response ensuing from presence and persistence of microorganisms in the bloodstream. The possibility to identify them at low concentrations may improve the problem of human health and therapeutic outcomes. So, sensitive and rapid diagnostic systems are essential to evaluate bacterial infections during the time, also reducing the cost. In this study, from random M13 phage display libraries, we selected phage clones that specifically bind surface of Staphyloccocus aureus, Pseudomonas aeruginosa and Escherichia coli. Then, commercial magnetic beads were functionalized with phage clones through covalent bond and used as capture and concentrating of pathogens from blood. We found that phage-magnetic beads complex represents a network which enables a cheap, high sensitive and specific detection of the bacteria involved in sepsis by micro-Raman spectroscopy. The enter process required 6 h and has the limit of detection of 10 Colony Forming Units on 7 ml of blood (CFU/7 ml).

Computational Models for Trapping Ebola Virus Using Engineered Bacteria

The outbreak of the Ebola virus in recent years has resulted in numerous research initiatives to seek new solutions to contain the virus. A number of approaches that have been investigated include new vaccines to boost the immune system. An alternative post-exposure treatment is presented in this paper. The proposed approach for clearing the Ebola virus can be developed through a microfluidic attenuator, which contains the engineered bacteria that traps Ebola flowing through the blood onto its membrane. The paper presents the analysis of the chemical binding force between the virus and a genetically engineered bacterium considering the opposing forces acting on the attachment point, including hydrodynamic tension and drag force. To test the efficacy of the technique, simulations of bacterial motility within a confined area to trap the virus were performed. More than 60 percent of the displaced virus could be collected within 15 minutes. While the proposed approach currently focuses on in vitro environments for trapping the virus, the system can be further developed into a future treatment system whereby blood can be cycled out of the body into a microfluidic device that contains the engineered bacteria to trap viruses.

Rapid and Sensitive Detection of Staphylococcal Enterotoxin B by Recombinant Nanobody Using Phage Display Technology

Staphylococcal enterotoxin B, from Staphylococcus aureus (S. aureus), is one of the most potent bacterial superantigens with profound toxic effects on the immune system. It is associated with food poisoning, toxic shock, atopic dermatitis, asthma, and nasal polyps in humans. The current diagnostic methods for staphylococcal enterotoxin are mainly based on traditional monoclonal antibodies which hardly meet the requirements for clinical applications, and hybridoma clones lose their ability to secrete antibodies during time. The present study investigates the development of a novel, highly specific, low-cost, and sensitive nanobody capable of being used in immunoassays for Staphylococcal enterotoxin B (SEB) detection in suspicious foods. For this purpose, Camelus dromedarius was immunized against SEB toxin. After obtaining acceptable titration, a high-quality phage display nanobody library (4 × 10¹⁰ PFU/ml) was constructed. High-affinity SEB-specific nanobodies were retrieved from constructed libraries. After phage rescue and five round of biopanning, clone screening was performed by phage ELISA. Recombinant nanobodies which were expressed from C7 and C21 clone showed the highest affinity for SEB. The presence of high quality and pure nanobody band at ~ 15 kDa was confirmed by SDS-PAGE and western blotting. The affinity constant which was measured by ELISA was calculated to be around 10^-9 M. The results suggest that the proposed detection method by nanobodies is an alternative diagnostic tool enabling a rapid, inexpensive, and specific detection of the SEB.

Landscape Phage: Evolution from Phage Display to Nanobiotechnology

The development of phage engineering technology has led to the construction of a novel type of phage display library-a collection of nanofiber materials with diverse molecular landscapes accommodated on the surface of phage particles. These new nanomaterials, called the "landscape phage", serve as a huge resource of diagnostic/detection probes and versatile construction materials for the preparation of phage-functionalized biosensors and phage-targeted nanomedicines. Landscape-phage-derived probes interact with biological threat agents and generate detectable signals as a part of robust and inexpensive molecular recognition interfaces introduced in mobile detection devices. The use of landscape-phage-based interfaces may greatly improve the sensitivity, selectivity, robustness, and longevity of these devices. In another area of bioengineering, landscape-phage technology has facilitated the development and testing of targeted nanomedicines. The development of high-throughput phage selection methods resulted in the discovery of a variety of cancer cell-associated phages and phage proteins demonstrating natural proficiency to self-assemble into various drug- and gene-targeting nanovehicles. The application of this new "phage-programmed-nanomedicines" concept led to the development of a number of cancer cell-targeting nanomedicine platforms, which demonstrated anticancer efficacy in both in vitro and in vivo experiments. This review was prepared to attract the attention of chemical scientists and bioengineers seeking to develop functionalized nanomaterials and use them in different areas of bioscience, medicine, and engineering.

Identification of a peptide for folate receptor alpha by phage display and its tumor targeting activity in ovary cancer xenograft

The expression level of folate receptor alpha (FRα) is located highly rate in ovarian cancer though it is remained absent in normal tissues. This highly tumor restricted expression profile makes FRα a promising target for tumor therapy and diagnosis. In this research we report a FRα binding peptide C7(Met-His-Thr-Ala-Pro-Gly-Trp-Gly-Tyr-Arg-Leu-Ser) discovered by phage display and this peptide showed specific binding to FRα expressing cells by cell ELISA and flow cytometry. Tumor targeting ability of C7 was proved in vivo by both phage homing experiment and fluorescence imaging. C7 can be internalized by SKOV3 cells and its affinity to FRα was determined by MST. The molecular recognition was revealed by structure modeling, suggesting its binding mode with FRα.

Autonomous self-navigating drug-delivery vehicles: from science fiction to reality

Low efficacy of targeted nanomedicines in biological experiments enforced us to challenge the traditional concept of drug targeting and suggest a paradigm of ‘addressed self-navigating drug-delivery vehicles,’ in which affinity selection of targeting peptides and vasculature-directed in vivo phage screening is replaced by the migration selection, which explores ability of ‘promiscuous’ phages and their proteins to migrate through the tumor-surrounding cellular barriers, using a ‘hub and spoke’ delivery strategy, and penetrate into the tumor affecting the diverse tumor cell population. The ‘self-navigating’ drug-delivery paradigm can be used as a theoretical and technical platform in design of a novel generation of molecular medications and imaging probes for precise and personal medicine.

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Bacteriophages: the possible solution to treat infections caused by pathogenic bacteria

Since their discovery in 1915, bacteriophages have been used to treat bacterial infections in animals and humans because of their unique ability to infect their specific bacterial hosts without affecting other bacterial populations. The research carried out in this field throughout the 20th century, largely in Georgia, part of USSR and Poland, led to the establishment of phage therapy protocols. However, the discovery of penicillin and sulfonamide antibiotics in the Western World during the 1930s was a setback in the advancement of phage therapy. The misuse of antibiotics has reduced their efficacy in controlling pathogens and has led to an increase in the number of antibiotic-resistant bacteria. As an alternative to antibiotics, bacteriophages have become a topic of interest with the emergence of multidrug-resistant bacteria, which are a threat to public health. Recent studies have indicated that bacteriophages can be used indirectly to detect pathogenic bacteria or directly as biocontrol agents. Moreover, they can be used to develop new molecules for clinical applications, vaccine production, drug design, and in the nanomedicine field via phage display.

Dynamic Model Exposes the Energetics and Dynamics of the Injection Machinery for Bacteriophage T4

Bacteriophage T4 infects the bacterial host (Escherichia coli) using an efficient genomic delivery machine that is driven by elastic energy stored in a contractile tail sheath. Although the atomic structure of T4 is largely known, the dynamics of its fascinating injection machinery is not understood. This article contributes, to our knowledge, the first predictions of the energetics and dynamics of the T4 injection machinery using a novel dynamic model. The model employs an atomistic (molecular dynamics) representation of a fraction of the sheath structure to generate a continuum model of the entire sheath that also couples to a model of the viral capsid and tail tube. The resulting model of the entire injection machine reveals estimates for the energetics, timescale, and pathway of the T4 injection process as well as the force available for cell rupture. It also reveals the large and highly nonlinear conformational changes of the sheath whose elastic energy drives the injection process.

Discovery of a polystyrene binding peptide isolated from phage display library and its application in peptide immobilization

Phage peptide display is a powerful technique for discovery of various target-specific ligands. However, target-unrelated peptides can often be obtained and cause ambiguous results. Peptide PB-TUP has been isolated repeatedly in our laboratory on different targets and we conducted a research on PB-TUP phage to investigate their binding properties and rate of propagation. ELISA and phage recovery assay demonstrated that PB-TUP phage had a significant superior affinity to polystyrene solid surface compared with control phage clones. In this study, some incidental bindings are excluded like blocking agents and non-specific binding of secondary antibodies. Propagation rate assays of the selected phage clones showed that the growth rate of PB-TUP phage was not superior to the control phages. Furthermore, the binding of PB-TUB to polystyrene was concentration dependent and varied with solution pH. Molecular modeling revealed that stable structures of α-helix and β-turn may contribute to the binding of PB-TUP to polystyrene plate. The PB-TUP sequence was fused to the N-terminus of peptide P2 and the fusion peptide significantly increased the binding affinity to polystyrene. The fusion peptide also enhanced the cell adhesion ability of peptide P2 with human umbilical vein endothelial cell (HUVEC). The addition of the polystyrene binding peptide provided a convenient method for peptide immobilization.

Antibody Engineering for Pursuing a Healthier Future

Since the development of antibody-production techniques, a number of immunoglobulins have been developed on a large scale using conventional methods. Hybridoma technology opened a new horizon in the production of antibodies against target antigens of infectious pathogens, malignant diseases including autoimmune disorders, and numerous potent toxins. However, these clinical humanized or chimeric murine antibodies have several limitations and complexities. Therefore, to overcome these difficulties, recent advances in genetic engineering techniques and phage display technique have allowed the production of highly specific recombinant antibodies. These engineered antibodies have been constructed in the hunt for novel therapeutic drugs equipped with enhanced immunoprotective abilities, such as engaging immune effector functions, effective development of fusion proteins, efficient tumor and tissue penetration, and high-affinity antibodies directed against conserved targets. Advanced antibody engineering techniques have extensive applications in the fields of immunology, biotechnology, diagnostics, and therapeutic medicines. However, there is limited knowledge regarding dynamic antibody development approaches. Therefore, this review extends beyond our understanding of conventional polyclonal and monoclonal antibodies. Furthermore, recent advances in antibody engineering techniques together with antibody fragments, display technologies, immunomodulation, and broad applications of antibodies are discussed to enhance innovative antibody production in pursuit of a healthier future for humans.

Paradigm shift in bacteriophage-mediated delivery of anticancer drugs: from targeted 'magic bullets' to self-navigated 'magic missiles'

INTRODUCTION

New phage-directed nanomedicines have emerged recently as a result of the in-depth study of the genetics and structure of filamentous phage and evolution of phage display and phage nanobiotechnology. This review focuses on the progress made in the development of the cancer-targeted nanomaterials and discusses the trends in using phage as a bioselectable molecular navigation system. Areas covered: The merging of phage display technologies with nanotechnology in recent years has proved promising in different areas of medicine and technology, such as medical diagnostics, molecular imaging, vaccine development and targeted drug/gene delivery, which is the focus of this review. The authors used data obtained from their research group and sourced using Science Citation Index (Web of Science) and NCBI PubMed search resources. Expert opinion: First attempts of adapting traditional concepts of direct targeting of tumor using phage-targeted nanomedicines has shown minimal improvements. With discovery and study of biological and technical barriers that prevent anti-tumor drug delivery, a paradigm shift from traditional drug targeting to nanomedicine navigation systems is required. The advanced bacteriophage-driven self-navigation systems are thought to overcome those barriers using more precise, localized phage selection methods, multi-targeting 'promiscuous' ligands and advanced multifunctional nanomedicine platforms.

Phage-Enabled Nanomedicine: From Probes to Therapeutics in Precision Medicine

Both lytic and temperate bacteriophages (phages) can be applied in nanomedicine, in particular, as nanoprobes for precise disease diagnosis and nanotherapeutics for targeted disease treatment. Since phages are bacteria-specific viruses, they do not naturally infect eukaryotic cells and are not toxic to them. They can be genetically engineered to target nanoparticles, cells, tissues, and organs, and can also be modified with functional abiotic nanomaterials for disease diagnosis and treatment. This Review will summarize the current use of phage structures in many aspects of precision nanomedicine, including ultrasensitive biomarker detection, enhanced bioimaging for disease diagnosis, targeted drug and gene delivery, directed stem cell differentiation, accelerated tissue formation, effective vaccination, and nanotherapeutics for targeted disease treatment. We will also propose future directions in the area of phage-based nanomedicines, and discuss the state of phage-based clinical trials.

Virus-Enabled Biosensor for Human Serum Albumin

The label-free detection of human serum albumin (HSA) in aqueous buffer is demonstrated using a simple, monolithic, two-electrode electrochemical biosensor. In this device, both millimeter-scale electrodes are coated with a thin layer of a composite containing M13 virus particles and the electronically conductive polymer poly(3,4-ethylenedioxy thiophene) or PEDOT. These virus particles, engineered to selectively bind HSA, serve as receptors in this biosensor. The resistance component of the electrical impedance, Zre, measured between these two electrodes provides electrical transduction of HSA binding to the virus-PEDOT film. The analysis of sample volumes as small as 50 μL is made possible using a microfluidic cell. Upon exposure to HSA, virus-PEDOT films show a prompt increase in Zre within 5 s and a stable Zre signal within 15 min. HSA concentrations in the range from 100 nM to 5 μM are detectable. Sensor-to-sensor reproducibility of the HSA measurement is characterized by a coefficient-of-variance (COV) ranging from 2% to 8% across this entire concentration range. In addition, virus-PEDOT sensors successfully detected HSA in synthetic urine solutions.

Phage as a Genetically Modifiable Supramacromolecule in Chemistry, Materials and Medicine

Filamentous bacteriophage (phage) is a genetically modifiable supramacromolecule. It can be pictured as a semiflexible nanofiber (∼900 nm long and ∼8 nm wide) made of a DNA core and a protein shell with the former genetically encoding the latter. Although phage bioengineering and phage display techniques were developed before the 1990s, these techniques have not been widely used for chemistry, materials, and biomedical research from the perspective of supramolecular chemistry until recently. Powered by our expertise in displaying a foreign peptide on its surface through engineering phage DNA, we have employed phage to identify target-specific peptides, construct novel organic-inorganic nanohybrids, develop biomaterials for disease treatment, and generate bioanalytical methods for disease diagnosis. Compared with conventional biomimetic chemistry, phage-based supramolecular chemistry represents a new frontier in chemistry, materials science, and medicine. In this Account, we introduce our recent successful efforts in phage-based supramolecular chemistry, by integrating the unique nanofiber-like phage structure and powerful peptide display techniques into the fields of chemistry, materials science, and medicine: (1) successfully synthesized and assembled silica, hydroxyapatite, and gold nanoparticles using phage templates to form novel functional materials; (2) chemically introduced azo units onto the phage to form photoresponsive functional azo-phage nanofibers via a diazotization reaction between aromatic amino groups and the tyrosine residues genetically displayed on phage surfaces; (3) assembled phage into 2D films for studying the effects of both biochemical (the peptide sequences displayed on the phages) and biophysical (the topographies of the phage films) cues on the proliferation and differentiation of mesenchymal stem cells (MSCs) and induced pluripotent stem cells (iPSCs) and identified peptides and topographies that can induce their osteogenic differentiation; (4) discovered that phage could induce angiogenesis and osteogenesis for MSC-based vascularized bone regeneration; (5) identified novel breast cancer cell-targeting and MSC-targeting peptides and used them to significantly improve the efficiency of targeted cancer therapy and MSC-based gene delivery, respectively; (6) employed engineered phage as a probe to achieve ultrasensitive detection of biomarkers from serum of human patients for disease diagnosis; and (7) constructed centimeter-scale 3D multilayered phage assemblies with the potential application as scaffolds for bone regeneration and functional device fabrication. Our findings demonstrated that phage is indeed a very powerful supramacromolecule suitable for not only developing novel nanostructures and biomaterials but also advancing important fields in biomedicine, including molecular targeting, cancer diagnosis and treatment, drug and gene delivery, stem cell fate direction, and tissue regeneration. Our successes in exploiting phage in chemistry, materials, and medicine suggest that phage itself is nontoxic at the cell level and can be safely used for detecting biomarkers in vitro. Moreover, although we have demonstrated successful in vivo tissue regeneration induced by phage, we believe future studies are needed to evaluate the in vivo biodistribution and potential risks of the phage-based biomaterials.

Advance in phage display technology for bioanalysis

Phage display technology has emerged as a powerful tool for target gene expression and target-specific ligand selection. It is widely used to screen peptides, proteins and antibodies with the advantages of simplicity, high efficiency and low cost. A variety of targets, including ions, small molecules, inorganic materials, natural and biological polymers, nanostructures, cells, bacteria, and even tissues, have been demonstrated to generate specific binding ligands by phage display. Phages and target-specific ligands screened by phage display have been widely used as affinity reagents in therapeutics, diagnostics and biosensors. In this review, comparisons of different types of phage display systems are first presented. Particularly, microfluidic-based phage display, which enables screening with high throughput, high efficiency and integration, is highlighted. More importantly, we emphasize the advances in biosensors based on phages or phage-derived probes, including nonlytic phages, lytic phages, peptides or proteins screened by phage display, phage assemblies and phage-nanomaterial complexes. However, more efficient and higher throughput phage display methods are still needed to meet an explosion in demand for bioanalysis. Furthermore, screening of cyclic peptides and functional peptides will be the hotspot in bioanalysis.

Engineering bacteriophage for a pragmatic low-resource setting bacterial diagnostic platform

Bacteriophages represent multifaceted building blocks that can be incorporated as substitutes for, or in unison with other detection methods, to create powerful new diagnostics for the detection of bacteria. The ease of phage manipulation, production, and detection speed clearly highlights that there remains unrealized opportunities to leverage these phage-based components in diagnostics amenable to resource-limited settings. The passage of regulations like the Food Safety Modernization act, and the ever increasing extent of global trade and travel, will create further demand for these types of diagnostics. While phage-based diagnostics have begun to entering the market place, further research is needed to ensure the potential benefits of phage-based technologies for public health are fully realized. We are just beginning to explore the possibilities that phage-based detection can offer us in the future. The combination of engineered phages as well as engineered enzymes could result in ultrasensitive detection systems for low-resource settings. Because the reporter enzyme is synthesized in vivo, we need to consider the options outside of normal enzyme reporters. In this case, common enzyme issues such as purification and long-term stability are less important. Phage-based diagnostics were conceptualized from out-of-the box thinking and the evolution of these systems should be as well.

Effects of an amyloid-beta 1-42 oligomers antibody screened from a phage display library in APP/PS1 transgenic mice

We screened anti-Aβ1-42 antibodies from a human Alzheimer's disease (AD) specific single chain variable fragment (scFv) phage display library and assessed their effects in APP/PS1 transgenic mice. Reverse transcription-PCR was used to construct the scFv phage display library, and screening identified 11A5 as an anti-Aβ1-42 antibody. We mixed 11A5 and the monoclonal antibody 6E10 with Aβ1-42 and administered the mixture to Sprague-Dawley rats via intracerebroventricular injection. After 30 days, rats injected with the antibody/Aβ1-42 mixture and those injected with Aβ1-42 alone were tested on the Morris water maze. We also injected 11A5 and 6E10 into APP/PS1 transgenic mice and assessed the concentrations of Aβ in brain and peripheral blood by ELISA at 1-month intervals for 3 months. Finally we evaluated behavior changes in the Morris water maze. Rats injected with Aβ1-42 and mixed antibodies showed better performance in the Morris water maze than did rats injected with Aβ1-42 alone. In APP/PS1 transgenic mice, Aβ concentration was lower in the brains of the antibody-treated group than in the control group, but higher in the peripheral blood. The antibody-treated mice also exhibited improved behavioral performance in the Morris water maze. In conclusion, anti-Aβ1-42 antibodies (11A5) screened from the human scFv antibody phage display library promoted the efflux or clearance of Aβ1-42 and effectively decreased the cerebral Aβ burden in an AD mouse model.

A Label-Free Electrochemical Impedance Cytosensor Based on Specific Peptide-Fused Phage Selected from Landscape Phage Library

One of the major challenges in the design of biosensors for cancer diagnosis is to introduce a low-cost and selective probe that can recognize cancer cells. In this paper, we combined the phage display technology and electrochemical impedance spectroscopy (EIS) to develop a label-free cytosensor for the detection of cancer cells, without complicated purification of recognition elements. Fabrication steps of the cytosensing interface were monitored by EIS. Due to the high specificity of the displayed octapeptides and avidity effect of their multicopy display on the phage scaffold, good biocompatibility of recombinant phage, the fibrous nanostructure of phage, and the inherent merits of EIS technology, the proposed cytosensor demonstrated a wide linear range (2.0 × 10(2) - 2.0 × 10(8) cells mL(-1)), a low limit of detection (79 cells mL(-1), S/N = 3), high specificity, good inter-and intra-assay reproducibility and satisfactory storage stability. This novel cytosensor designing strategy will open a new prospect for rapid and label-free electrochemical platform for tumor diagnosis.

Modern affinity reagents: Recombinant antibodies and aptamers

Affinity reagents are essential tools in both basic and applied research; however, there is a growing concern about the reproducibility of animal-derived monoclonal antibodies. The need for higher quality affinity reagents has prompted the development of methods that provide scientific, economic, and time-saving advantages and do not require the use of animals. This review describes two types of affinity reagents, recombinant antibodies and aptamers, which are non-animal technologies that can replace the use of animal-derived monoclonal antibodies. Recombinant antibodies are protein-based reagents, while aptamers are nucleic-acid-based. In light of the scientific advantages of these technologies, this review also discusses ways to gain momentum in the use of modern affinity reagents, including an update to the 1999 National Academy of Sciences monoclonal antibody production report and federal incentives for recombinant antibody and aptamer efforts. In the long-term, these efforts have the potential to improve the overall quality and decrease the cost of scientific research.

Epidemiology of <i>Salmonella</i> and <i>Salmonellosis</i>

The prevalence of enteritis and its accompanying diarrheal and other health challenges linked to infections with Salmonella has continuously plagued sub Saharan Africa. In Nigeria, typhoid fever is among the major widespread diseases affecting both young and old as a result of many interrelated factors such as inadequate sanitaion, indiscriminate use of antibiotics and fecal contamination of water sources. Morbidity associated with illness due to Salmonella continues to increase with untold fatal consequences, often resulting in death. An accurate figure of cases is difficult to arrive at because only large outbreaks are mostly investigated whereas sporadic cases are under-reported. A vast majority of rural dwellers in Africa often resort to self-medication or seek no treatment at all, hence serving as carries of this disease. Non typhoidal cases of salmonellosis account for about 1.3 billion cases with 3 million deaths annually. Given the magnitude of the economic losses incurred by African nations in the battle against salmonella and salmonellosis, this article takes a critical look at the genus Salmonella, its morphology, isolation, physiological and biochemical characteristics, typing methods, methods of detection, virulence factor, epidemiology and methods of spread within the environment.

Identification of Soft Matter Binding Peptide Ligands Using Phage Display

Phage display is a powerful tool for the selection of highly affine, short peptide ligands. While originally primarily used for the identification of ligands to proteins, the scope of this technique has significantly expanded over the past two decades. Phage display nowadays is also increasingly applied to identify ligands that selectively bind with high affinity to a broad range of other substrates including natural and biological polymers as well as a variety of low-molecular-weight organic molecules. Such peptides are of interest for various reasons. The ability to selectively and with high affinity bind to the substrate of interest allows the conjugation or immobilization of, e.g., nanoparticles or biomolecules, or generally, facilitates interactions at materials interfaces. On the other hand, presentation of peptide ligands that selectively bind to low-molecular-weight organic materials is of interest for the development of sensor surfaces. The aim of this article is to highlight the opportunities provided by phage display for the identification of peptide ligands that bind to synthetic or natural polymer substrates or to small organic molecules. The article will first provide an overview of the different peptide ligands that have been identified by phage display that bind to these "soft matter" targets. The second part of the article will discuss the different characterization techniques that allow the determination of the affinity of the identified ligands to the respective substrates.

Phage-AgNPs complex as SERS probe for U937 cell identification

The early diagnosis of malignancy is the most critical factor for patient survival and the treatment of cancer. In particular, leukemic cells are highly heterogeneous, and there is a need to develop new rapid and accurate detection systems for early diagnosis and monitoring of minimal residual disease. This study reports the utilization of molecular networks consisting of entire bacteriophage structure, displaying specific peptides, directly assembled with silver nanoparticles as a new Surface Enhanced Raman Spectroscopy (SERS) probe for U937 cells identification in vitro. A 9-mer pVIII M13 phage display library is screened against U937 to identify peptides that selectively recognize these cells. Then, phage clone is assembled with silver nanoparticles and the resulting network is used to obtain a SERS signal on cell-type specific molecular targets. The proposed strategy could be a very sensitive tool for the design of biosensors for highly specific and selective identification of hematological cancer cells and for detection of minimal residual disease in a significant proportion of human blood malignancy.

Integration of genetically modified virus-like-particles with an optical resonator for selective bio-detection

A novel virus-like particle (TMV-VLP) receptor layer has been integrated with an optical microdisk resonator transducer for biosensing applications. This bioreceptor layer is functionalized with selective peptides that encode unique recognition affinities. Integration of bioreceptors with sensor platforms is very challenging due their very different compatibility regimes. The TMV-VLP nanoreceptor exhibits integration robustness, including the ability for self-assembly along with traditional top-down microfabrication processes. An optical microdisk resonator has been functionalized for antibody binding with this receptor, demonstrating resonant wavelength shifts of (Δλo) of 0.79 nm and 5.95 nm after primary antibody binding and enzyme-linked immunosorbent assay (ELISA), respectively, illustrating label-free sensing of this bonding event. This demonstration of label-free sensing with genetically engineered TMV-VLP shows the flexibility and utility of this receptor coating when considering integration with other existing transducer platforms.

Advances in Anthrax Detection: Overview of Bioprobes and Biosensors

Anthrax is an infectious disease caused by Bacillus anthracis. Although anthrax commonly affects domestic and wild animals, it causes a rare but lethal infection in humans. A variety of techniques have been introduced and evaluated to detect anthrax using cultures, polymerase chain reaction, and immunoassays to address the potential threat of anthrax being used as a bioweapon. The high-potential harm of anthrax in bioterrorism requires sensitive and specific detection systems that are rapid, field-ready, and real-time monitoring. Here, we provide a systematic overview of anthrax detection probes with their potential applications in various ultra-sensitive diagnostic systems.

Current approaches in SELEX: An update to aptamer selection technology

Systematic evolution of ligands by exponential enrichment (SELEX) is a well-established and efficient technology for the generation of oligonucleotides with a high target affinity. These SELEX-derived single stranded DNA and RNA molecules, called aptamers, were selected against various targets, such as proteins, cells, microorganisms, chemical compounds etc. They have a great potential in the use as novel antibodies, in cancer theragnostics and in biomedical research. Vast interest in aptamers stimulated continuous development of SELEX, which underwent numerous modifications since its first application in 1990. Novel modifications made the selection process more efficient, cost-effective and significantly less time-consuming. This article brings a comprehensive and up-to-date review of recent advances in SELEX methods and pinpoints advantages, main obstacles and limitations. The post-SELEX strategies and examples of application are also briefly outlined in this review.

Production of recombinant scFv against p24 of human immunodeficiency virus type 1 by phage display technology

Phage display has a fundamental role in protein isolation and engineering. Isolated proteins produced with this method can be modified for specific binding and affinity. P24 is the most produced protein during human immune deficiency virus (HIV) replication; especially in the early steps of HIV-1 infection, its evaluation may have diagnostic values. To test the HIV-1 infection, p24 antigen assay appears to be a very promising alternative to RNA assays. In this study, we have generated a recombinant mouse single chain antibody fragment against p24 of the HIV-1 with the use of phage display technology. After isolation of antibody variable-region (V) gene of B cells extracted from the spleen of an immunized mouse, a library of single chain Fv fragments (scFv) was constructed. The library was used in a series of bio-panning processes against recombinant p24 protein expressed from Escherichia coli. The isolated scFv antibody specifically recognizes the HIV-1 capsid protein p24. The affinity constant of the isolated scFv antibody (MF85) was found to be 2×10(-9) M. Our studies showed that the MF85 scFV antibody has similar properties as that of monoclonal antibodies produced by the hybridoma technology.