Bioscreening specific peptide-expressing phage and its application in sensitive dual-mode immunoassay of SARS-CoV-2 spike antigen

Biorecognition components with high affinity and selectivity are vital in bioassay to diagnose and treat epidemic disease. Herein a phage display strategy of combining single-amplification-panning with non-amplification-panning was developed, by which a phage displaying cyclic heptapeptide ACLDWLFNSC (peptide J4) with good affinity and specificity to SARS-CoV-2 spike protein (SP) was identified. Molecular docking suggests that peptide J4 binds to S2 subunit by hydrogen bonding and hydrophobic interaction. Then the J4-phage was used as the capture antibody to establish phage-based chemiluminescence immunoassay (CLIA) and electrochemical impedance spectroscopy (EIS) analytical systems. The as-proposed dual-modal immunoassay platform exhibited good sensitivity and reliability in SARS-CoV-2 SP and pseudovirus assay. The limit of detection for SARS-CoV-2 SP by EIS immunoassay is 0.152 pg/mL, which is dramatically lower than that of 42 pg/mL for J4-phage based CLIA. Further, low to 40 transducing units (TU)/mL, 10 TU/mL SARS-CoV-2 pseudoviruses can be detected by the proposed J4-phage based CLIA and electrochemical immunosensor, respectively. Therefore, the as-developed dual mode immunoassays are potential methods to detect SARS-CoV-2. It is also expected to explore various phages with specific peptides to different targets for bioanalysis.

Nanoparticles for imaging-guided photothermal therapy of colorectal cancer

Colorectal cancer (CRC) is one of the most common malignancies with a high mortality rate worldwide. While surgery, chemotherapy, and radiotherapy have shown some effectiveness in improving survival rates, they come with drawbacks such as side effects and harm to healthy tissues. The theranostic approach, which integrates the processes of cancer diagnosis and treatment, can minimize biological side effects. Photothermal therapy (PTT) is an emerging treatment method that usages light-sensitive agents to generate heat at the tumor site and induce thermal erosion. The development of nanotechnology for CRC treatment using imaging-guided PTT has garnered significant. Nanoparticles with suitable physical and chemical properties can enhance the efficiency of cancer diagnosis and PTT. This approach enables the monitoring of cancer treatment progress and safeguards healthy tissues. In this article, we concisely introduce the application of metal nanoparticles, polymeric nanoparticles, and carbon nanoparticles in imaging-guided PTT of colorectal cancer.

Sensitive Lateral Flow Immunoassay Based on Specific Peptide and Superior Oxidase Mimics with a Universal Dual-Mode Significant Signal Amplification

Rapid and sensitive antigen detection using a lateral flow immunoassay (LFIA) is crucial for diagnosing infectious diseases due to its simplicity, speed, and user-friendly features. However, it remains a critical issue to explore specific biorecognition elements and powerful signal amplification. In this study, taking SARS-CoV-2 as a proof of concept, a specific peptide, WFLNDSELIML, binding to the SARS-CoV-2 spike (S) antigen was identified by a nonamplified biopanning method, which exhibited high affinity to the target, with a dissociation constant of 9.29 ± 1.55 nM. Molecular docking analysis reveals that this peptide binds to the N-terminal domain of the SARS-CoV-2 S antigen. Then, using this peptide as a capture probe and angiotensin-converting enzyme 2 as a detection probe, a peptide-based lateral flow immunoassay (pLFIA) for the sensitive detection of the SARS-CoV-2 S antigen without any antibody was developed, for which a polydopamine nanosphere (PDA)@MnO2 nanocomposite with excellent oxidase-like activity was used as a colorimetric label, exhibiting dual-mode remarkable signal amplification of natural melanin and on-demand nanozyme catalytic enhancement. The PDA@MnO2-based pLFIA is capable of detecting the SARS-CoV-2 S antigen with a limit of detection of 8.01 pg/mL, which is 18.7 times lower than that of a conventional pLFIA tagged with gold nanoparticles. Additionally, the as-proposed PDA@MnO2-based pLFIA can detect up to 150 transduction units/mL SARS-CoV-2 pseudoviruses spiked in saliva samples. Given the outstanding analytical performance, the proposed PDA@MnO2-based pLFIA may offer a reliable option for the rapid diagnosis of SARS-CoV-2.

An ultrasensitive ELISA to assay femtomolar level SARS-CoV-2 antigen based on specific peptide and tyramine signal amplification

The SARS-CoV-2 spreading rapidly has aroused catastrophic public healthcare issues and economy crisis worldwide. It plays predominant role to rapidly and accurately diagnose the virus for effective prevention and treatment. As an abundant transmembrane protein, spike protein (SP) is one of the most valuable antigenic biomarkers for diagnosis of COVID-19. Herein a phage expression of WNLDLSQWLPPM peptide specific to SARS-CoV-2 SP was screened. Molecular docking revealed that the isolated peptide binds to major antigenic epitope locating at S2 subunit with hydrogen bonding. Taking the specific peptide as antigen sensing probe and tyramine signal amplification (TSA), an ultrasensitive "peptide-antigen-antibody" ELISA (p-ELISA) was explored, by which the limit of detection (LOD) was 14 fM and 2.8 fM SARS-CoV-2 SP antigen for first TSA and secondary TSA, respectively. Compared with the LOD by the p-ELISA by direct mode, the sensitivity with 2nd TSA enhanced 100 times. Further, the proposed p-ELISA method can detect SARS-CoV-2 pseudoviruses down to 10 and 3 TCID₅₀/mL spiked in healthy nasal swab sample with 1st TSA and 2nd TSA, separately. Thus, the proposed p-ELISA method with TSA is expected to be a promising ultrasensitive tool for rapidly detecting SARS-CoV-2 antigen to help control the infectious disease.

Biopanning of specific peptide for SARS-CoV-2 nucleocapsid protein and enzyme-linked immunosorbent assay-based antigen assay

The ongoing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has rapidly spread worldwide which triggered serious public health issues. The search for rapid and accurate diagnosis, effective prevention, and treatment is urgent. The nucleocapsid protein (NP) of SARS-CoV-2 is one of the main structural proteins expressed and most abundant in the virus, and is considered a diagnostic marker for the accurate and sensitive detection of SARS-CoV-2. Herein, we report the screening of specific peptides from the pIII phage library that bind to SARS-CoV-2 NP. The phage monoclone expressing cyclic peptide N1 (peptide sequence, ACGTKPTKFC, with C&C bridged by disulfide bonding) specifically recognizes SARS-CoV-2 NP. Molecular docking studies reveal that the identified peptide is bound to the "pocket" region on the SARS-CoV-2 NP N-terminal domain mainly by forming a hydrogen bonding network and through hydrophobic interaction. Peptide N1 with the C-terminal linker was synthesized as the capture probe for SARS-CoV-2 NP in ELISA. The peptide-based ELISA was capable of assaying SARS-CoV-2 NP at concentrations as low as 61 pg/mL (∼1.2 pM). Furthermore, the as-proposed method could detect the SARS-CoV-2 virus at limits as low as 50 TCID₅₀ (median tissue culture infective dose)/mL. This study demonstrates that selected peptides are powerful biomolecular tools for SARS-CoV-2 detection, providing a new and inexpensive method of rapidly screening infections as well as rapidly diagnosing coronavirus disease 2019 patients.

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.

An ultrasensitive label-free electrochemical impedimetric immunosensor for vascular endothelial growth factor based on specific phage via negative pre-screening

As a vascular growth regulator, vascular endothelial growth factor (VEGF) exerts significant biological roles through specific binding to its receptors on the vascular endothelial cells. VEGF165 is generally referenced as a potential therapeutic target of many malignant tumors. In this study, a negative pre-screening strategy with structurally analogous members of VEGF121, VEGFC and VEGFD was first proposed for VEGF165 biopanning, aiming at significantly improving the specificity of the selected phage monoclones. Indirect ELISA experiment showed that the phage monoclone expressing peptide SPFLLRM demonstrates excellent affinity and specificity. Then a VEGF165 electrochemical impedimetric spectroscopy (EIS) immunosensor was constructed by above specific phage modified electrode. After optimizing the experimental conditions, the as-explored EIS immunosensor had a linear range of 0.5-1000 pg/mL with the limit of detection of 0.15 pg/mL VEGF165. In addition, the developed phage-based EIS immunosensor was applied to satisfactorily detect VEGF165 in human serum samples. Considering its ultra-sensitivity, good selectivity, batch reproducibility and stability, the screened selective phage-based EIS sensor is envisioned potential application in diagnosis and therapy.

Gold nanotheranostics: future emblem of cancer nanomedicine

Cancer nanotheranostics aims at providing alternative approaches to traditional cancer diagnostics and therapies. In this context, plasmonic nanostructures especially gold nanostructures are intensely explored due to their tunable shape, size and surface plasmon resonance (SPR), better photothermal therapy (PTT) and photodynamic therapy (PDT) ability, effective contrast enhancing ability in Magnetic Resonance imaging (MRI) and Computed Tomography (CT) scan. Despite rapid breakthroughs in gold nanostructures based theranostics of cancer, the translation of gold nanostructures from bench side to human applications is still questionable. The major obstacles that have been facing by nanotheranostics are specific targeting, poor resolution and photoinstability during PTT etc. In this regard, various encouraging studies have been carried out recently to overcome few of these obstacles. Use of gold nanocomposites also overcomes the limitations of gold nanostructure probes and emerged as good nanotheranostic probe. Hence, the present article discusses the advances in gold nanostructures based cancer theranostics and mainly emphasizes on the importance of gold nanocomposites which have been designed to decipher the past questions and limitations of in vivo gold nanotheranostics.

Gold nanoplates with superb photothermal efficiency and peroxidase-like activity for rapid and synergistic antibacterial therapy

Gold nanoplates exhibit 68.5% photothermal conversion efficiency and peroxidase-like activity, and AuNPTs (50 μg mL⁻¹)/H₂O₂ (0.1 mM)/NIR (1 W cm⁻², 3 min) show excellent synergistic antibacterial ability and promote MRSA-infected wound healing in vivo.

pH-Responsive Cascaded Nanocatalyst for Synergistic Like-Starvation and Chemodynamic therapy

A tumor microenvironment (TME) responsive cascade nanocatalyst was built based on copper-embedded hollow mesoporous silica (HMSN-Cu) decorated with glucose oxidase (GOD) on the surface, realizing tumor-selected cascade catalyst for elegant combination of starving therapy and chemodynamic therapy. Specifically, benefited from the strong demand for glucose metabolism in tumor cells, this HMSN-Cu-GOD could catalyze rich glucose into H2O2 in the presence of O2, along with localized declined pH in situ to in turn degrade HMSN-Cu and thus release Cu2+/Cu+. Importantly, abound hydroxyl radical (•OH) with high oxidative activity generated in the Fenton reaction between H2O2 and Cu2+/Cu+. Interesting, the high-expressed GSH and exacerbated hypoxia in tumor cells, will facilitate accumulation of Cu+ with much higher reaction efficiency, further enhanced Chemodynamic therapy (CDT) efficiency. Compared with monotherapy, in vitro and vivo tumor inhibition experiments demonstrated the superior synergistic effect of CDT and starving therapy based on a simple but effective biodegradable nanosystem.

Colorimetric Assay of Bacterial Pathogens Based on Co3O4 Magnetic Nanozymes Conjugated with Specific Fusion Phage Proteins and Magnetophoretic Chromatography

It is important to detect pathogens rapidly, sensitively, and selectively for clinical medicine, homeland security, food safety, and environmental control. We report here a specific and sensitive colorimetric assay that incorporated a bovine serum albumin-templated Co₃O₄ magnetic nanozyme (Co₃O₄ MNE) with a novel specific fusion phage protein and magnetophoretic chromatography to detect Staphylococcus aureus. The Co₃O₄ MNE was conjugated to S. aureus-specific fusion-pVIII (Co₃O₄ MNE@fusion-pVIII), screened from the S. aureus-specific phage AQTFLGEQD (the phage monoclone is denoted by the peptide sequence). The as-prepared triple-functional Co₃O₄ MNE@fusion-pVIII particles were capable of capturing S. aureus in sterile milk, which were then isolated from milk magnetically. Assisted by polyethylene glycol, the Co₃O₄ MNE@fusion-pVIII@S. aureus complex was separated from the free Co₃O₄ MNE@fusion-pVIII by magnetophoretic chromatography in an external magnetic field. After transferring the isolated Co₃O₄ MNE@fusion-pVIII@S. aureus complexes into a 96-well plate, diammonium salt of 2,2'-azino-bis(3-ethylbenzo-thiazoline-6-sulfonic acid) and H₂O₂ were added to develop color because of the peroxidase mimetics activity of the Co₃O₄ MNE. A S. aureus concentration within 10-10,000 cfu/mL in milk can be detected (detection limit: 8 cfu/mL). The as-developed method is simple, cost-efficient, and sensitive, which is useful for rapidly diagnosing pathogenic bacteria and helpful to prevent disease outbreaks induced by pathogens in developing countries.

Optical-Based (Bio) Sensing Systems Using Magnetic Nanoparticles

In recent years, various reports related to sensing application research have suggested that combining the synergistic impacts of optical, electrical or magnetic properties in a single technique can lead to a new multitasking platform. Owing to their unique features of the magnetic moment, biocompatibility, ease of surface modification, chemical stability, high surface area, high mass transference, magnetic nanoparticles have found a wide range of applications in various fields, especially in sensing systems. The present review is comprehensive information about magnetic nanoparticles utilized in the optical sensing platform, broadly categorized into four types: surface plasmon resonance (SPR), surface-enhanced Raman spectroscopy (SERS), fluorescence spectroscopy and near-infrared spectroscopy and imaging (NIRS) that are commonly used in various (bio) analytical applications. The review also includes some conclusions on the state of the art in this field and future aspects.

Iron oxide nanoparticles for targeted imaging of liver tumors with ultralow hepatotoxicity

Even though iron oxide (Fe₃O₄) nanoparticles are promising materials for magnetic resonance imaging (MRI) contrast agents, their biocompatibility and targeting efficacy still need to be improved. Herein, we modified glycyrrhetinic acid (GA) groups on Fe₃O₄ nanoparticles (Fe₃O₄@cGlu-GA) for liver tumor-targeted imaging. To evaluate the biocompatibility of these nanoparticles, we studied their cytotoxicity, hemolysis, and hepatotoxicity. We measured the uptake of Fe₃O₄@cGlu-GA nanoparticles in normal and liver tumor cells, then we investigated the specificity of Fe₃O₄@cGlu-GA nanoparticles in mouse models bearing subcutaneous and orthotopic liver tumors. With good biocompatibility and targeting efficacy both in vitro and in vivo, the Fe₃O₄@cGlu-GA nanoparticles are promising MRI contrast agents with ultralow hepatotoxicity and show great improvement on existing Fe₃O₄-based nanoparticles.

Iron Oxide Nanoparticles in Photothermal Therapy

Photothermal therapy is a kind of therapy based on increasing the temperature of tumoral cells above 42 °C. To this aim, cells must be illuminated with a laser, and the energy of the radiation is transformed in heat. Usually, the employed radiation belongs to the near-infrared radiation range. At this range, the absorption and scattering of the radiation by the body is minimal. Thus, tissues are almost transparent. To improve the efficacy and selectivity of the energy-to-heat transduction, a light-absorbing material, the photothermal agent, must be introduced into the tumor. At present, a vast array of compounds are available as photothermal agents. Among the substances used as photothermal agents, gold-based compounds are one of the most employed. However, the undefined toxicity of this metal hinders their clinical investigations in the long run. Magnetic nanoparticles are a good alternative for use as a photothermal agent in the treatment of tumors. Such nanoparticles, especially those formed by iron oxides, can be used in combination with other substances or used themselves as photothermal agents. The combination of magnetic nanoparticles with other photothermal agents adds more capabilities to the therapeutic system: the nanoparticles can be directed magnetically to the site of interest (the tumor) and their distribution in tumors and other organs can be imaged. When used alone, magnetic nanoparticles present, in theory, an important limitation: their molar absorption coefficient in the near infrared region is low. The controlled clustering of the nanoparticles can solve this drawback. In such conditions, the absorption of the indicated radiation is higher and the conversion of energy in heat is more efficient than in individual nanoparticles. On the other hand, it can be designed as a therapeutic system, in which the heat generated by magnetic nanoparticles after irradiation with infrared light can release a drug attached to the nanoparticles in a controlled manner. This form of targeted drug delivery seems to be a promising tool of chemo-phototherapy. Finally, the heating efficiency of iron oxide nanoparticles can be increased if the infrared radiation is combined with an alternating magnetic field.