Noninvasive In Vivo Imaging of T-Cells during Cancer Immunotherapy Using Rare-Earth Nanoparticles

Only a minority of patients respond positively to cancer immunotherapy, and addressing this variability is an active area of immunotherapy research. Infiltration of tumors by immune cells is one of the most significant prognostic indicators of response and disease-free survival. However, the ability to noninvasively sample the tumor microenvironment for immune cells remains limited. Imaging in the near-infrared-II region using rare-earth nanocrystals is emerging as a powerful imaging tool for high-resolution deep-tissue imaging. In this paper, we demonstrate that these nanoparticles can be used for noninvasive in vivo imaging of tumor-infiltrating T-cells in a highly aggressive melanoma tumor model. We present nanoparticle synthesis and surface modification strategies for the generation of small, ultrabright, and biocompatible rare-earth nanocrystals necessary for deep tissue imaging of rare cell types. The ability to noninvasively monitor the immune contexture of a tumor during immunotherapy could lead to early identification of nonresponding patients in real time, leading to earlier interventions and better outcomes.

STING Protein-Based In Situ Vaccine Synergizes CD4+ T, CD8+ T, and NK Cells for Tumor Eradication

Stimulator of interferon genes (STING) signaling is a promising target in cancer immunotherapy, with many ongoing clinical studies in combination with immune checkpoint blockade (ICB). Existing STING-based therapies largely focus on activating CD8+ T cell or NK cell-mediated cytotoxicity, while the role of CD4+ T cells in STING signaling has yet to be extensively studied in vivo. Here, a distinct CD4-mediated, protein-based combination therapy of STING and ICB as an in situ vaccine, is reported. The treatment eliminates subcutaneous MC38 and YUMM1.7 tumors in 70-100% of mice and protected all cured mice against rechallenge. Mechanistic studies reveal a robust TH 1 polarization and suppression of Treg of CD4+ T cells, followed by an effective collaboration of CD4+ T, CD8+ T, and NK cells to eliminate tumors. Finally, the potential to overcome host STING deficiency by significantly decreasing MC38 tumor burden in STING KO mice is demonstrated, addressing the translational challenge for the 19% of human population with loss-of-function STING variants.

Engineering a Two-Component Hemostat for the Treatment of Internal Bleeding through Wound-Targeted Crosslinking

Primary hemostasis (platelet plug formation) and secondary hemostasis (fibrin clot formation) are intertwined processes that occur upon vascular injury. Researchers have sought to target wounds by leveraging cues specific to these processes, such as using peptides that bind activated platelets or fibrin. While these materials have shown success in various injury models, they are commonly designed for the purpose of treating solely primary or secondary hemostasis. In this work, a two-component system consisting of a targeting component (azide/GRGDS PEG-PLGA nanoparticles) and a crosslinking component (multifunctional DBCO) is developed to treat internal bleeding. The system leverages increased injury accumulation to achieve crosslinking above a critical concentration, addressing both primary and secondary hemostasis by amplifying platelet recruitment and mitigating plasminolysis for greater clot stability. Nanoparticle aggregation is measured to validate concentration-dependent crosslinking, while a 1:3 azide/GRGDS ratio is found to increase platelet recruitment, decrease clot degradation in hemodiluted environments, and decrease complement activation. Finally, this approach significantly increases survival relative to the particle-only control in a liver resection model. In light of prior successes with the particle-only system, these results emphasize the potential of this technology in aiding hemostasis and the importance of a holistic approach in engineering new treatments for hemorrhage.

A Machine Learning-optimized system for on demand, pulsatile, photo- and chemo-therapeutic treatment using near-infrared responsive MoS 2 -based microparticles in a breast cancer model

Cancer therapy research is of high interest because of the persistence and mortality of the disease and the side effects of traditional therapeutic methods, while often multimodal treatments are necessary based on the patient's needs. The development of less invasive modalities for recurring treatment cycles is thus of critical significance. Herein, a light-activatable microparticle system was developed for localized, pulsatile delivery of anticancer drugs with simultaneous thermal ablation, by applying controlled ON-OFF thermal cycles using near-infrared laser irradiation. The system is composed of poly(caprolactone) microparticles of 200 μm size with incorporated molybdenum disulfide (MoS ₂ ) nanosheets as the photothermal agent and hydrophilic doxorubicin or hydrophobic violacein, as model drugs. Upon irradiation the nanosheets heat up to ≥50 °C leading to polymer matrix melting and release of the drug. MoS ₂ nanosheets exhibit high photothermal conversion efficiency and allow for application of low power laser irradiation for the system activation. A Machine Learning algorithm was applied to acquire optimal laser operation conditions; 0.4 W/cm ² laser power at 808 nm, 3-cycle irradiation, for 3 cumulative minutes. In a mouse subcutaneous model of 4T1 triple-negative breast cancer, 25 microparticles were intratumorally administered and after 3-cycle laser treatment the system conferred synergistic phototherapeutic and chemotherapeutic effect. Our on-demand, pulsatile synergistic treatment resulted in increased median survival up to 40 days post start of treatment compared to untreated mice, with complete eradication of the tumors at the primary site. Such a system could have potential for patients in need of recurring cycles of treatment on subcutaneous tumors.

GRAPHICAL ABSTRACT

Abstract 820: Photo-activatable ON-OFF microparticles for on-demand pulsatile drug delivery in a breast cancer model

The ability to treat tumors with high efficacy in a local microenvironment, while mitigating the side effects of systemic toxicity is an area of active investigation. Towards this goal, designing a minimally-invasive local therapeutic modality, with a controlled, pulsatile drug release mechanism is an attractive proposition.

In this study, a near-infrared (NIR) photo-activatable microparticle was developed for localized, pulsatile delivery of encapsulated anticancer drugs into the tumor with simultaneous thermal ablation, with controlled ON-OFF thermal cycles using NIR laser irradiation. The microparticles were fabricated using a poly(caprolactone) (PCL) matrix, containing 2D molybdenum disulfide (MoS2) nanosheets as the NIR-responsive photothermal agent, and doxorubicin or violacein, as hydrophilic and hydrophobic model anticancer drugs, respectively. Cubic microparticles of 200 µm size were fabricated by casting a polymer-MoS2-drug film on PDMS mold with loading efficiency of 2 μg MoS2 per particle, and 0.2-8 μg of drug per particle. A cytotoxicity assay was performed to test the efficacy of the loaded microparticles in reducing the viability of 4T1 murine-derived cell culture, using the ON-OFF laser switch mechanism. In order to select a suitable laser power and duration of treatment for in vivo studies, a Machine Learning algorithm based on a Random Forest classifier was trained, to arrive at the optimal treatment conditions: 0.4-0.5 W/cm2 of laser power at 808 nm, for 3 cumulative minutes of laser irradiation, to reach the target temperature of 50 °C, which activates PCL melting and subsequent drug release.

The effect of pulsatile treatment was studied in vivo in a murine-derived 4T1 subcutaneous mouse model of breast cancer, using this photo-activatable ON-OFF switch mechanism, for up to 3 cycles of laser irradiation. As control groups, tumor only (no treatment), laser only (no drug or microparticle), drug only (no laser or microparticle), microparticles only (no drug or laser), and microparticles with laser (no drug) were studied. The cohorts receiving the photo-activated 3-cyclic treatment for both drugs showed increased median survival up to 40 days post tumor induction, compared to a median survival of 16 days for the control groups. Although one laser cycle was enough to trigger drug release, there was a significant shrinkage in the tumor volume noticed with 3 cycles, with eventual scarring and shedding of the tissue with no evidence of residual tumor at the primary site.

While this cyclic drug release modality is very effective at treating the primary site, subsequent histopathology revealed that the aggressive tumor in some animals had metastasized to the liver and other organs. More work is ongoing to design better targeted approaches to deliver the drug-loaded microparticles to the site of metastatic tumors, to increase the survival prospects of this disease.

Citation Format: Maria Kanelli, Neelkanth M. Bardhan, Morteza Sarmadi, Shahad Alsaiari, William Rothwell, Apurva Pardeshi, Angela M. Belcher, Ana Jaklenec, Robert S. Langer. Photo-activatable ON-OFF microparticles for on-demand pulsatile drug delivery in a breast cancer model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 820.

A new label-free optical imaging method for the lymphatic system enhanced by deep learning

Our understanding of the lymphatic vascular system lags far behind that of the blood vascular system, limited by available imaging technologies. We present a label-free optical imaging method that visualizes the lymphatic system with high contrast. We developed an orthogonal polarization imaging (OPI) in the shortwave infrared range (SWIR) and imaged both lymph nodes and lymphatic vessels of mice and rats in vivo through intact skin, as well as human mesenteric lymph nodes in colectomy specimens. By integrating SWIR-OPI with U-Net, a deep learning image segmentation algorithm, we automated the lymph node size measurement process. Changes in lymph nodes in response to cancer progression were monitored in two separate mouse cancer models, through which we obtained insights into pre-metastatic niches and correlation between lymph node masses and many important biomarkers. In a human pilot study, we demonstrated the effectiveness of SWIR-OPI to detect human lymph nodes in real time with clinical colectomy specimens.

One Sentence Summary

We develop a real-time high contrast optical technique for imaging the lymphatic system, and apply it to anatomical pathology gross examination in a clinical setting, as well as real-time monitoring of tumor microenvironment in animal studies.

Phage Particles of Controlled Length and Genome for In Vivo Targeted Glioblastoma Imaging and Therapeutic Delivery

M13 bacteriophage (phage) are versatile, genetically tunable nanocarriers that have been recently adapted for use as diagnostic and therapeutic platforms. Applying p3 capsid chlorotoxin fusion with the "inho" circular single-stranded DNA (cssDNA) gene packaging system, we produced miniature chlorotoxin inho (CTX-inho) phage particles with a minimum length of 50 nm that can target intracranial orthotopic patient-derived GBM22 glioblastoma tumors in the brains of mice. Systemically administered indocyanine green conjugated CTX-inho phage accumulated in brain tumors, facilitating shortwave infrared detection. Furthermore, we show that our inho phage can carry cssDNA that are transcriptionally active when delivered to GBM22 glioma cells in vitro. The ability to modulate the capsid display, surface loading, phage length, and cssDNA gene content makes the recombinant M13 phage particle an ideal delivery platform.

Surface Plasmon Enhanced Upconversion Fluorescence in Short-Wave Infrared for In Vivo Imaging of Ovarian Cancer

Short-wave infrared (SWIR; 850-1700 nm) upconversion fluorescence enables "autofluorescence-free" imaging with minimal tissue scattering, yet it is rarely explored due to the lack of strongly emissive SWIR upconversion fluorophores. In this work, we apply SWIR upconversion fluorescence for in vivo imaging with exceptional image contrast. Gold nanorods (AuNRs) are used to enhance the SWIR upconversion emission of small organic dyes, forming a AuNR-dye nanocomposite (NC). A maximal enhancement factor of ∼1320, contributed by both excitation and radiative decay rate enhancement, is achieved by varying the dye-to-AuNR ratio. In addition, the upconversion emission intensity of both free dyes and AuNR-dye NCs depends linearly on the excitation power, indicating that the upconversion emission mechanism remains unchanged upon enhancement, and it involves one-photon absorption. Moreover, the SWIR upconversion emission shows a significantly higher signal contrast than downconversion emission in the same emission window in a nonscattering medium. Finally, we apply the surface plasmon enhanced SWIR upconversion fluorescence for in vivo imaging of ovarian cancer, demonstrating high image contrast and low required dosage due to the suppressed autofluorescence.

Peptide-Based Cancer Vaccine Delivery via the STINGΔTM-cGAMP Complex

With the advent of bioinformatic tools in efficiently predicting neo-antigens, peptide vaccines have gained tremendous attention in cancer immunotherapy. However, the delivery of peptide vaccines remains a major challenge, primarily due to ineffective transport to lymph nodes and low immunogenicity. Here, a strategy for peptide vaccine delivery is reported by first fusing the peptide to the cytosolic domain of the stimulator of interferon genes protein (STINGΔTM), then complexing the peptide-STINGΔTM protein with STING agonist 2'3' cyclic guanosine monophosphate-adenosine monophosphate (cGAMP). The process results in the formation of self-assembled cGAMP-peptide-STINGΔTM tetramers, which enables efficient lymphatic trafficking of the peptide. Moreover, the cGAMP-STINGΔTM complex acts not only as a protein carrier for the peptide, but also as a potent adjuvant capable of triggering STING signaling independent of endogenous STING protein-an especially important attribute considering that certain cancer cells epigenetically silence their endogenous STING expression. With model antigen SIINFEKL, it is demonstrated that the platform elicits effective STING signaling in vitro, draining lymph node targeting in vivo, effective T cell priming in vivo as well as antitumoral immune response in a mouse colon carcinoma model, providing a versatile solution to the challenges faced in peptide vaccine delivery.

A particulate saponin/TLR agonist vaccine adjuvant alters lymph flow and modulates adaptive immunity

[Figure: see text].

Graphene, Carbon Nanotube and Plasmonic Nanosensors for Detection of Viral Pathogens: Opportunities for Rapid Testing in Pandemics like COVID-19

With the emergence of global pandemics such as the Black Death (Plague), 1918 influenza, smallpox, tuberculosis, HIV/AIDS, and currently the COVID-19 outbreak caused by the SARS-CoV-2 virus, there is an urgent, pressing medical need to devise methods of rapid testing and diagnostics to screen a large population of the planet. The important considerations for any such diagnostic test include: 1) high sensitivity (to maximize true positive rate of detection); 2) high specificity (to minimize false positives); 3) low cost of testing (to enable widespread adoption, even in resource-constrained settings); 4) rapid turnaround time from sample collection to test result; and 5) test assay without the need for specialized equipment. While existing testing methods for COVID-19 such as RT-PCR (real-time reverse transcriptase polymerase chain reaction) offer high sensitivity and specificity, they are quite expensive – in terms of the reagents and equipment required, the laboratory expertise needed to run and interpret the test data, and the turnaround time. In this review, we summarize the recent advances made using carbon nanotubes for sensors; as a nanotechnology-based approach for diagnostic testing of viral pathogens; to improve the performance of the detection assays with respect to sensitivity, specificity and cost. Carbon nanomaterials are an attractive platform for designing biosensors due to their scalability, tunable functionality, photostability, and unique opto-electronic properties. Two possible approaches for pathogen detection using carbon nanomaterials are discussed here: 1) optical sensing, and 2) electrochemical sensing. We explore the chemical modifications performed to add functionality to the carbon nanotubes, and the physical, optical and/or electronic considerations used for testing devices or sensors fabricated using these carbon nanomaterials. Given this progress, it is reason to be cautiously optimistic that nanosensors based on carbon nanotubes, graphene technology and plasmonic resonance effects can play an important role towards the development of accurate, cost-effective, widespread testing capacity for the world’s population, to help detect, monitor and mitigate the spread of disease outbreaks.

Surface Plasmon-Enhanced Short-Wave Infrared Fluorescence for Detecting Sub-Millimeter-Sized Tumors

Short-wave infrared (SWIR, 900-1700 nm) enables in vivo imaging with high spatiotemporal resolution and penetration depth due to the reduced tissue autofluorescence and decreased photon scattering at long wavelengths. Although small organic SWIR dye molecules have excellent biocompatibility, they have been rarely exploited as compared to their inorganic counterparts, mainly due to their low quantum yield. To increase their brightness, in this work, the SWIR dye molecules are placed in close proximity to gold nanorods (AuNRs) for surface plasmon-enhanced emission. The fluorescence enhancement is optimized by controlling the dye-to-AuNR number ratio and up to ≈45-fold enhancement factor is achieved. In addition, the results indicate that the highest dye-to-AuNR number ratio gives the highest emission intensity per weight and this is used for synthesizing SWIR imaging probes using layer-by-layer (LbL) technique with polymer coating protection. Then, the SWIR imaging probes are applied for in vivo imaging of ovarian cancer and the surface coating effect on intratumor distribution of the imaging probes is investigated in two orthotopic ovarian cancer models. Lastly, it is demonstrated that the plasmon-enhanced SWIR imaging probe has great potential for fluorescence imaging-guided surgery by showing its capability to detect sub-millimeter-sized tumors.

Simulating selective binding of a biological template to a nanoscale architecture: a core concept of a clamp-based binding-pocket-favored N-terminal-domain assembly

The biological template and its mutants have vital significance in next generation remediation, electrochemical, photovoltaic, catalytic, sensing and digital memory devices. However, a microscopic model describing the biotemplating process is generally lacking on account of modelling complexity, which has prevented widespread commercial use of biotemplates. Here, we demonstrate M13-biotemplating kinetics in atomic resolution by leveraging large-scale molecular dynamics (MD) simulations. The model reveals the assembly of gold nanoparticles on two experimentally-based M13 phage types using full M13-capsid structural models and with polarizable gold nanoparticles in explicit solvent. Both mechanistic and structural insights into the selective binding affinity of the M13 phage to gold nanoparticles are obtained based on a previously unconsidered clamp-based binding-pocket-favored N-terminal-domain assembly and also on surface-peptide flexibility. These results provide a deeper level of understanding of protein sequence-based affinity and open the route for genetically engineering a wide range of 3D electrodes for high-density low-cost device integration.

Virus-Templated Nickel Phosphide Nanofoams as Additive-Free, Thin-Film Li-Ion Microbattery Anodes

Transition metal phosphides are a new class of materials generating interest as alternative negative electrodes in lithium-ion batteries. However, metal phosphide syntheses remain underdeveloped in terms of simultaneous control over phase composition and 3D nanostructure. Herein, M13 bacteriophage is employed as a biological scaffold to develop 3D nickel phosphide nanofoams with control over a range of phase compositions and structural elements. Virus-templated Ni₅ P₄ nanofoams are then integrated as thin-film negative electrodes in lithium-ion microbatteries, demonstrating a discharge capacity of 677 mAh g^-1 (677 mAh cm^-3 ) and an 80% capacity retention over more than 100 cycles. This strong electrochemical performance is attributed to the virus-templated, nanostructured morphology, which remains electronically conductive throughout cycling, thereby sidestepping the need for conductive additives. When accounting for the mass of additional binder materials, virus-templated Ni₅ P₄ nanofoams demonstrate the highest practical capacity reported thus far for Ni₅ P₄ electrodes. Looking forward, this synthesis method is generalizable and can enable precise control over the 3D nanostructure and phase composition in other metal phosphides, such as cobalt and copper.

M13 Virus-Based Framework for High Fluorescence Enhancement

Fluorescence imaging is a powerful tool for studying biologically relevant macromolecules, but its applicability is often limited by the fluorescent probe, which must demonstrate both high site-specificity and emission efficiency. In this regard, M13 virus, a versatile biological scaffold, has previously been used to both assemble fluorophores on its viral capsid with molecular precision and to also target a variety of cells. Although M13-fluorophore systems are highly selective, these complexes typically suffer from poor molecular detection limits due to low absorption cross-sections and moderate quantum yields. To overcome these challenges, a coassembly of the M13 virus, cyanine 3 dye, and silver nanoparticles is developed to create a fluorescent tag capable of binding with molecular precision with high emissivity. Enhanced emission of cyanine 3 of up to 24-fold is achieved by varying nanoparticle size and particle-fluorophore separation. In addition, it is found that the fluorescence enhancement increases with increasing dye surface density on the viral capsid. Finally, this highly fluorescent probe is applied for in vitro staining of E. coli. These results demonstrate an inexpensive framework for achieving tuned fluorescence enhancements. The methodology developed in this work is potentially amendable to fluorescent detection of a wide range of M13/cell combinations.

Creating fluorescent quantum defects in carbon nanotubes using hypochlorite and light

Covalent doping of single-walled carbon nanotubes (SWCNTs) can modify their optical properties, enabling applications as single-photon emitters and bio-imaging agents. We report here a simple, quick, and controllable method for preparing oxygen-doped SWCNTs with desirable emission spectra. Aqueous nanotube dispersions are treated at room temperature with NaClO (bleach) and then UV-irradiated for less than one minute to achieve optimized O-doping. The doping efficiency is controlled by varying surfactant concentration and type, NaClO concentration, and irradiation dose. Photochemical action spectra indicate that doping involves reaction of SWCNT sidewalls with oxygen atoms formed by photolysis of ClO^- ions. Variance spectroscopy of products reveals that most individual nanotubes in optimally treated samples show both pristine and doped emission. A continuous flow reactor is described that allows efficient preparation of milligram quantities of O-doped SWCNTs. Finally, we demonstrate a bio-imaging application that gives high contrast short-wavelength infrared fluorescence images of vasculature and lymphatic structures in mice injected with only ~100 ng of the doped nanotubes.

Real-Time Single-Walled Carbon Nanotube-Based Fluorescence Imaging Improves Survival after Debulking Surgery in an Ovarian Cancer Model

Improved cytoreductive surgery for advanced stage ovarian cancer (OC) represents a critical challenge in the treatment of the disease. Optimal debulking reaching no evidence of macroscopic disease is the primary surgical end point with a demonstrated survival advantage. Targeted molecule-based fluorescence imaging offers complete tumor resection down to the microscopic scale. We used a custom-built reflectance/fluorescence imaging system with an orthotopic OC mouse model to both quantify tumor detectability and evaluate the effect of fluorescence image-guided surgery on post-operative survival. The contrast agent is an intraperitoneal injectable nanomolecular probe, composed of single-walled carbon nanotubes, coupled to an M13 bacteriophage carrying a modified peptide binding to the SPARC protein, an extracellular protein overexpressed in OC. The imaging system is capable of detecting a second near-infrared window fluorescence (1000-1700 nm) and can display real-time video imagery to guide intraoperative tumor debulking. We observed high microscopic tumor detection with a pixel-limited resolution of 200 μm. Moreover, in a survival-surgery orthotopic OC mouse model, we demonstrated an increased survival benefit for animals treated with fluorescence image-guided surgical resection compared to standard surgery.

Deep-tissue optical imaging of near cellular-sized features

Detection of biological features at the cellular level with sufficient sensitivity in complex tissue remains a major challenge. To appreciate this challenge, this would require finding tens to hundreds of cells (a 0.1 mm tumor has ~125 cells), out of ~37 trillion cells in the human body. Near-infrared optical imaging holds promise for high-resolution, deep-tissue imaging, but is limited by autofluorescence and scattering. To date, the maximum reported depth using second-window near-infrared (NIR-II: 1000–1700 nm) fluorophores is 3.2 cm through tissue. Here, we design an NIR-II imaging system, “Detection of Optically Luminescent Probes using Hyperspectral and diffuse Imaging in Near-infrared” (DOLPHIN), that resolves these challenges. DOLPHIN achieves the following: (i) resolution of probes through up to 8 cm of tissue phantom; (ii) identification of spectral and scattering signatures of tissues without apriori knowledge of background or autofluorescence; and (iii) 3D reconstruction of live whole animals. Notably, we demonstrate noninvasive real-time tracking of a 0.1 mm-sized fluorophore through the gastrointestinal tract of a living mouse, which is beyond the detection limit of current imaging modalities.

Highly adjustable 3D nano-architectures and chemistries via assembled 1D biological templates

Porous metal nanofoams have made significant contributions to a diverse set of technologies from separation and filtration to aerospace. Nonetheless, finer control over nano and microscale features must be gained to reach the full potential of these materials in energy storage, catalytic, and sensing applications. As biologics naturally occur and assemble into nano and micro architectures, templating on assembled biological materials enables nanoscale architectural control without the limited chemical scope or specialized equipment inherent to alternative synthetic techniques. Here, we rationally assemble 1D biological templates into scalable, 3D structures to fabricate metal nanofoams with a variety of genetically programmable architectures and material chemistries. We demonstrate that nanofoam architecture can be modulated by manipulating viral assembly, specifically by editing the viral surface coat protein, as well as altering templating density. These architectures were retained over a broad range of compositions including monometallic and bi-metallic combinations of noble and transition metals of copper, nickel, cobalt, and gold. Phosphorous and boron incorporation was also explored. In addition to increasing the surface area over a factor of 50, as compared to the nanofoam's geometric footprint, this process also resulted in a decreased average crystal size and altered phase composition as compared to non-templated controls. Finally, templated hydrogels were deposited on the centimeter scale into an array of substrates as well as free standing foams, demonstrating the scalability and flexibility of this synthetic method towards device integration. As such, we anticipate that this method will provide a platform to better study the synergistic and de-coupled effects between nano-structure and composition for a variety of applications including energy storage, catalysis, and sensing.

Thermally robust solvent-free biofluids of M13 bacteriophage engineered for high compatibility with anhydrous ionic liquids

Soft materials typically lack structural complexity. Chemically modifying viruses can produce biomaterials with added functionality that overcome this limitation.

DNA Origami and G-Quadruplex Hybrid Complexes Induce Size Control of Single-Walled Carbon Nanotubes via Biological Activation

DNA self-assembly has enabled the programmable fabrication of nanoarchitectures, and these nanoarchitectures combined with nanomaterials have provided several applications. Here, we develop an approach for cutting single-walled carbon nanotubes (SWNTs) of predetermined lengths, using DNA origami and G-quadruplex hybrid complexes. This approach is based on features of DNA: (1) wrapping SWNTs with DNA to improve the dispersibility of SWNTs in water; (2) using G-quadruplex DNA to confine hemin in close proximity to SWNTs and enhance the biological activation of hydrogen peroxide by hemin; and (3) forming DNA origami platforms to allow for the precise placement of G-quadruplexes, enabling size control. These integrated features of DNA allow for temporally efficient cutting of SWNTs into desired lengths, thus expanding the availability of SWNTs for applications in the fields of nanoelectronics, nanomedicine, nanomaterials, and quantum physics, as well as in fundamental studies.

Harnessing the hygroscopic and biofluorescent behaviors of genetically tractable microbial cells to design biohybrid wearables

Cells' biomechanical responses to external stimuli have been intensively studied but rarely implemented into devices that interact with the human body. We demonstrate that the hygroscopic and biofluorescent behaviors of living cells can be engineered to design biohybrid wearables, which give multifunctional responsiveness to human sweat. By depositing genetically tractable microbes on a humidity-inert material to form a heterogeneous multilayered structure, we obtained biohybrid films that can reversibly change shape and biofluorescence intensity within a few seconds in response to environmental humidity gradients. Experimental characterization and mechanical modeling of the film were performed to guide the design of a wearable running suit and a fluorescent shoe prototype with bio-flaps that dynamically modulates ventilation in synergy with the body's need for cooling.

Enhanced Cell Capture on Functionalized Graphene Oxide Nanosheets through Oxygen Clustering

With the global rise in incidence of cancer and infectious diseases, there is a need for the development of techniques to diagnose, treat, and monitor these conditions. The ability to efficiently capture and isolate cells and other biomolecules from peripheral whole blood for downstream analyses is a necessary requirement. Graphene oxide (GO) is an attractive template nanomaterial for such biosensing applications. Favorable properties include its two-dimensional architecture and wide range of functionalization chemistries, offering significant potential to tailor affinity toward aromatic functional groups expressed in biomolecules of interest. However, a limitation of current techniques is that as-synthesized GO nanosheets are used directly in sensing applications, and the benefits of their structural modification on the device performance have remained unexplored. Here, we report a microfluidic-free, sensitive, planar device on treated GO substrates to enable quick and efficient capture of Class-II MHC-positive cells from murine whole blood. We achieve this by using a mild thermal annealing treatment on the GO substrates, which drives a phase transformation through oxygen clustering. Using a combination of experimental observations and MD simulations, we demonstrate that this process leads to improved reactivity and density of functionalization of cell capture agents, resulting in an enhanced cell capture efficiency of 92 ± 7% at room temperature, almost double the efficiency afforded by devices made using as-synthesized GO (54 ± 3%). Our work highlights a scalable, cost-effective, general approach to improve the functionalization of GO, which creates diverse opportunities for various next-generation device applications.

Abstract 4196: Real-time single-walled nanotube (SWNT)-based imaging system improves tumor detection and survival in ovarian cancer animal model

Residual tumor detection in advanced stage ovarian cancer (OC) represents a critical challenge in the treatment of this disease. Optimal abdominal cytoreduction to reduce tumor to no evidence of macroscopic disease is the main endpoint of tumor debulking surgery, with demonstrated survival advantages, but the current clinically available imaging modalities have shown low tumor detection sensitivity of tumors smaller than 10 mm diameter. Instead, targeted molecule-based imaging systems offer higher detection rate and are likely to extend the aim of complete resection to the microscopic scale. We applied a custom designed imaging system to a preclinical ovarian cancer tumor model and observed higher microscopic tumor detection accuracy and survival advantage compared to non-image guided debulking surgery.

A two component imaging system was developed. The contrast agent is an intra-peritoneal injectable nanomolecular probe, composed of a single walled carbon nanotube (SWNT) coupled with an engineered M13-bacteriophage carrying a modified peptide targeting secreted protein, acidic and rich in cysteine (SPARC), extracellular protein overexpressed in OC. The imaging device system is capable of detecting SWNT inherent fluorescence in near-infrared second window (NIR2) and of displaying real-time images to guide the intraoperative tumor debulking.

In an orthotopic ovarian cancer animal model, the imaging system detected microscopic tumors in the millimeter and sub-millimeter scale resolution with a mean tumor diameter of 2.1 vs 3.6 mm (p< 0.01) compared to eye detected tumors. The imaging system demonstrated sensitivity of 97.2% and specificity of 69.7%, and a Receiver Operator Area under the Curve of 0.85 + 0.05. In a survival surgery animal model, the imaging guided resection surgery compared to non guided surgery showed a survival advantage for the experimental arm, with median survival time of 41.0 days vs 28.5 days, respectively (HR 0.22, 95% CI of ratio 0.04 to 1.08 Log Rank test: p: 0.063).

The accuracy of the imaging system and its survival advantage are promising. The survival outcome improvement in this preclinical model supports the translation to first-in-human investigation. Moreover, the imaging system accuracy suggests further exploitation in targeted delivery therapies.

Citation Format: Lorenzo Ceppi, YoungJeong Na, Neelkanth M. Bardhan, Andrew Siegel, Nandini Rajan, Angela M. Belcher, Michael J. Birrer. Real-time single-walled nanotube (SWNT)-based imaging system improves tumor detection and survival in ovarian cancer animal model. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4196.

Enhanced energy transport in genetically engineered excitonic networks

One of the challenges for achieving efficient exciton transport in solar energy conversion systems is precise structural control of the light-harvesting building blocks. Here, we create a tunable material consisting of a connected chromophore network on an ordered biological virus template. Using genetic engineering, we establish a link between the inter-chromophoric distances and emerging transport properties. The combination of spectroscopy measurements and dynamic modelling enables us to elucidate quantum coherent and classical incoherent energy transport at room temperature. Through genetic modifications, we obtain a significant enhancement of exciton diffusion length of about 68% in an intermediate quantum-classical regime.

Delayed emergence of methamphetamine's enhanced cardiovascular effects in nonhuman primates during protracted methamphetamine abstinence

BACKGROUND

Methamphetamine abuse is linked with brain abnormalities, but its peripheral effects constitute an integral aspect of long-term methamphetamine use.

METHODS

Eight male rhesus monkeys with long histories of intravenous methamphetamine self-administration were evaluated 1 day, and 1, 4, 12, 26, and 52 weeks after their last methamphetamine self-administration session. On test days, isoflurane-anesthetized animals received a 0.35 mg/kg IV methamphetamine challenge. A control group consisted of 10 age and gender matched drug naïve monkeys. Cardiovascular responses to methamphetamine were followed for 2.5h. Echocardiograms were acquired at 3 and 12 months of abstinence and in the control animals.

RESULTS

No pre-methamphetamine baseline differences existed among 7 physiological measures across all conditions and controls. As expected, methamphetamine increased heart rate and blood pressure in controls. However, immediately following the self-administration period, the blood pressure response to methamphetamine challenge was reduced when compared to control monkeys. The peak and 150-min average heart rate increases, as well as peak blood pressure increases following methamphetamine were significantly elevated between weeks 12 to 26 of abstinence. These data indicate the development of tolerance followed by sensitization to methamphetamine cardiovascular effects. Echocardiography demonstrated decreased left ventricular ejection fraction and cardiac output at 3 months of abstinence. Importantly, both cardiovascular sensitization and cardiotoxicity appeared to be reversible as they returned toward control group levels after 1 year of abstinence.

CONCLUSIONS

Enhanced cardiovascular effects may occur after prolonged abstinence in addicts relapsing to methamphetamine and may underlie clinically reported acute cardiotoxic events.

Graphene Oxide Nanosheets Modified with Single-Domain Antibodies for Rapid and Efficient Capture of Cells

Peripheral blood can provide valuable information on an individual's immune status. Cell-based assays typically target leukocytes and their products. Characterization of leukocytes from whole blood requires their separation from the far more numerous red blood cells.1 Current methods to classify leukocytes, such as recovery on antibody-coated beads or fluorescence-activated cell sorting require long sample preparation times and relatively large sample volumes.2 A simple method that enables the characterization of cells from a small peripheral whole blood sample could overcome limitations of current analytical techniques. We describe the development of a simple graphene oxide surface coated with single-domain antibody fragments. This format allows quick and efficient capture of distinct WBC subpopulations from small samples (∼30 μL) of whole blood in a geometry that does not require any specialized equipment such as cell sorters or microfluidic devices.

Improving the capacity of sodium ion battery using a virus-templated nanostructured composite cathode

In this work we investigated an energy-efficient biotemplated route to synthesize nanostructured FePO4 for sodium-based batteries. Self-assembled M13 viruses and single wall carbon nanotubes (SWCNTs) have been used as a template to grow amorphous FePO4 nanoparticles at room temperature (the active composite is denoted as Bio-FePO4-CNT) to enhance the electronic conductivity of the active material. Preliminary tests demonstrate a discharge capacity as high as 166 mAh/g at C/10 rate, corresponding to composition Na0.9FePO4, which along with higher C-rate tests show this material to have the highest capacity and power performance reported for amorphous FePO4 electrodes to date.

Carbon nanotube–polyaniline core–shell nanostructured hydrogel for electrochemical energy storage

Highly porous three-dimensional core (carbon nanotube)–shell (polyaniline) conductive hydrogels synergize the advantageous features of hydrogels and conductive materials, showing enhanced electrical conductivity and electrochemical activity.

Versatile de novo enzyme activity in capsid proteins from an engineered M13 bacteriophage library

Biocatalysis has grown rapidly in recent decades as a solution to the evolving demands of industrial chemical processes. Mounting environmental pressures and shifting supply chains underscore the need for novel chemical activities, while rapid biotechnological progress has greatly increased the utility of enzymatic methods. Enzymes, though capable of high catalytic efficiency and remarkable reaction selectivity, still suffer from relative instability, high costs of scaling, and functional inflexibility. Herein, we developed a biochemical platform for engineering de novo semisynthetic enzymes, functionally modular and widely stable, based on the M13 bacteriophage. The hydrolytic bacteriophage described in this paper catalyzes a range of carboxylic esters, is active from 25 to 80 °C, and demonstrates greater efficiency in DMSO than in water. The platform complements biocatalysts with characteristics of heterogeneous catalysis, yielding high-surface area, thermostable biochemical structures readily adaptable to reactions in myriad solvents. As the viral structure ensures semisynthetic enzymes remain linked to the genetic sequences responsible for catalysis, future work will tailor the biocatalysts to high-demand synthetic processes by evolving new activities, utilizing high-throughput screening technology and harnessing M13's multifunctionality.

Assembly of viral hydrogels for three-dimensional conducting nanocomposites

M13 bacteriophages act as versatile scaffolds capable of organizing single-walled carbon nanotubes and fabricating three-dimensional conducting nanocomposites. The morphological, electrical, and electrochemical properties of the nanocomposites are presented, as well as its ability to disperse and utilize single-walled carbon nanotubes effectively.

M13 virus-directed synthesis of nanostructured metal oxides for lithium-oxygen batteries

Transition metal oxides are promising electrocatalysts for both water oxidations and metal-air batteries. Here, we report the virus-mediated synthesis of cobalt manganese oxide nanowires (NWs) to fabricate high capacity Li-O2 battery electrodes. Furthermore, we hybridized Ni nanoparticles (NPs) on bio Co3O4 NWs to improve the round trip efficiency as well as the cycle life of Li-O2 batteries. This biomolecular directed synthesis method is expected to provide a selection platform for future energy storage electrocatalysts.

M13 virus based detection of bacterial infections in living hosts

We report a first method for using M13 bacteriophage as a multifunctional scaffold for optically imaging bacterial infections in vivo. We demonstrate that M13 virus conjugated with hundreds of dye molecules (M13-Dye) can target and distinguish pathogenic infections of F-pili expressing and F-negative strains of E. coli. Further, in order to tune this M13-Dye complex suitable for targeting other strains of bacteria, we have used a 1-step reaction for creating an anti-bacterial antibody-M13-Dye probe. As an example, we show anti-S. aureus-M13-Dye able to target and image infections of S. aureus in living hosts, with a 3.7× increase in fluorescence over background.

Assembly of a bacteriophage-based template for the organization of materials into nanoporous networks

M13 bacteriophages are assembled via a covalent layer-by-layer process to form a highly nanoporous network capable of organizing nanoparticles and acting as a scaffold for templating metal-oxides. The morphological and optical properties of the film itself are presented as well as its ability to organize and disperse metal nanoparticles.

Orthogonal labeling of M13 minor capsid proteins with DNA to self-assemble end-to-end multiphage structures

M13 bacteriophage has been used as a scaffold to organize materials for various applications. Building more complex multiphage devices requires precise control of interactions between the M13 capsid proteins. Toward this end, we engineered a loop structure onto the pIII capsid protein of M13 bacteriophage to enable sortase-mediated labeling reactions for C-terminal display. Combining this with N-terminal sortase-mediated labeling, we thus created a phage scaffold that can be labeled orthogonally on three capsid proteins: the body and both ends. We show that covalent attachment of different DNA oligonucleotides at the ends of the new phage structure enables formation of multiphage particles oriented in a specific order. These have potential as nanoscale scaffolds for multi-material devices.

Versatile three-dimensional virus-based template for dye-sensitized solar cells with improved electron transport and light harvesting

By genetically encoding affinity for inorganic materials into the capsid proteins of the M13 bacteriophage, the virus can act as a template for the synthesis of nanomaterial composites for use in various device applications. Herein, the M13 bacteriophage is employed to build a multifunctional and three-dimensional scaffold capable of improving both electron collection and light harvesting in dye-sensitized solar cells (DSSCs). This has been accomplished by binding gold nanoparticles (AuNPs) to the virus proteins and encapsulating the AuNP-virus complexes in TiO2 to produce a plasmon-enhanced and nanowire (NW)-based photoanode. The NW morphology exhibits an improved electron diffusion length compared to traditional nanoparticle-based DSSCs, and the AuNPs increase the light absorption of the dye-molecules through the phenomenon of localized surface plasmon resonance. Consequently, we report a virus-templated and plasmon-enhanced DSSC with an efficiency of 8.46%, which is achieved through optimizing both the NW morphology and the concentration of AuNPs loaded into the solar cells. In addition, we propose a theoretical model that predicts the experimentally observed trends of plasmon enhancement.

Biologically enhanced cathode design for improved capacity and cycle life for lithium-oxygen batteries

Lithium-oxygen batteries have a great potential to enhance the gravimetric energy density of fully packaged batteries by two to three times that of lithium ion cells. Recent studies have focused on finding stable electrolytes to address poor cycling capability and improve practical limitations of current lithium-oxygen batteries. In this study, the catalyst electrode, where discharge products are deposited and decomposed, was investigated as it has a critical role in the operation of rechargeable lithium-oxygen batteries. Here we report the electrode design principle to improve specific capacity and cycling performance of lithium-oxygen batteries by utilizing high-efficiency nanocatalysts assembled by M13 virus with earth-abundant elements such as manganese oxides. By incorporating only 3-5 wt% of palladium nanoparticles in the electrode, this hybrid nanocatalyst achieves 13,350 mAh g(-1)(c) (7,340 mAh g(-1)(c+catalyst)) of specific capacity at 0.4 A g(-1)(c) and a stable cycle life up to 50 cycles (4,000 mAh g(-1)(c), 400 mAh g(-1)(c+catalyst)) at 1 A g(-1)(c).

Refactored M13 bacteriophage as a platform for tumor cell imaging and drug delivery

M13 bacteriophage is a well-characterized platform for peptide display. The utility of the M13 display platform is derived from the ability to encode phage protein fusions with display peptides at the genomic level. However, the genome of the phage is complicated by overlaps of key genetic elements. These overlaps directly couple the coding sequence of one gene to the coding or regulatory sequence of another, making it difficult to alter one gene without disrupting the other. Specifically, overlap of the end of gene VII and the beginning of gene IX has prevented the functional genomic modification of the N-terminus of p9. By redesigning the M13 genome to physically separate these overlapping genetic elements, a process known as "refactoring," we enabled independent manipulation of gene VII and gene IX and the construction of the first N-terminal genomic modification of p9 for peptide display. We demonstrate the utility of this refactored genome by developing an M13 bacteriophage-based platform for targeted imaging of and drug delivery to prostate cancer cells in vitro. This successful use of refactoring principles to re-engineer a natural biological system strengthens the suggestion that natural genomes can be rationally designed for a number of applications.

M13-templated magnetic nanoparticles for targeted in vivo imaging of prostate cancer

Molecular imaging allows clinicians to visualize the progression of tumours and obtain relevant information for patient diagnosis and treatment. Owing to their intrinsic optical, electrical and magnetic properties, nanoparticles are promising contrast agents for imaging dynamic molecular and cellular processes such as protein-protein interactions, enzyme activity or gene expression. Until now, nanoparticles have been engineered with targeting ligands such as antibodies and peptides to improve tumour specificity and uptake. However, excessive loading of ligands can reduce the targeting capabilities of the ligand and reduce the ability of the nanoparticle to bind to a finite number of receptors on cells. Increasing the number of nanoparticles delivered to cells by each targeting molecule would lead to higher signal-to-noise ratios and would improve image contrast. Here, we show that M13 filamentous bacteriophage can be used as a scaffold to display targeting ligands and multiple nanoparticles for magnetic resonance imaging of cancer cells and tumours in mice. Monodisperse iron oxide magnetic nanoparticles assemble along the M13 coat, and its distal end is engineered to display a peptide that targets SPARC glycoprotein, which is overexpressed in various cancers. Compared with nanoparticles that are directly functionalized with targeting peptides, our approach improves contrast because each SPARC-targeting molecule delivers a large number of nanoparticles into the cells. Moreover, the targeting ligand and nanoparticles could be easily exchanged for others, making this platform attractive for in vivo high-throughput screening and molecular detection.

M13 bacteriophage display framework that allows sortase-mediated modification of surface-accessible phage proteins

We exploit bacterial sortases to attach a variety of moieties to the capsid proteins of M13 bacteriophage. We show that pIII, pIX, and pVIII can be functionalized with entities ranging from small molecules (e.g., fluorophores, biotin) to correctly folded proteins (e.g., GFP, antibodies, streptavidin) in a site-specific manner, and with yields that surpass those of any reported using phage display technology. A case in point is modification of pVIII. While a phage vector limits the size of the insert into pVIII to a few amino acids, a phagemid system limits the number of copies actually displayed at the surface of M13. Using sortase-based reactions, a 100-fold increase in the efficiency of display of GFP onto pVIII is achieved. Taking advantage of orthogonal sortases, we can simultaneously target two distinct capsid proteins in the same phage particle and maintain excellent specificity of labeling. As demonstrated in this work, this is a simple and effective method for creating a variety of structures, thus expanding the use of M13 for materials science applications and as a biological tool.

Virus-templated iridium oxide-gold hybrid nanowires for electrochromic application

A highly porous electrode comprised of biologically templated iridium oxide-gold (IrO(2)-Au) hybrid nanowires is introduced for electrochromic applications. A filamentous M13 virus is genetically engineered to display IrO(2)-binding peptides on the viral surface and used as a template for the self-assembly of IrO(2) nanoclusters into a nanowire. The open porous morphology of the prepared nanowire film facilitates ion transport. Subsequently, the redox kinetics of the IrO(2) nanowires seems to be limited by the electric resistance of the nanowire film. To increase the electron mobility in the nanowires, gold nanoparticles are chemically linked to the virus prior to the IrO(2) mineralization, forming a gold nanostring structure along the long axis of the virus. The resulting IrO(2)-Au hybrid nanowires exhibit a switching time of 35 ms for coloration and 25 ms for bleaching with a transmission change of about 30.5% at 425 nm. These values represent almost an order of magnitude faster switching responses than those of an IrO(2) nanowire film having the similar optical contrast. This work shows that genetically engineered viruses can serve as versatile templates to co-assemble multiple functional molecules, enabling control of the electrochemical properties of nanomaterials.

Biotemplated synthesis of perovskite nanomaterials for solar energy conversion

A synthetic method of using genetically engineered M13 virus to mineralize perovskite nanomaterials, particularly strontium titanate (STO) and bismuth ferrite (BFO), is presented. Genetically engineered viruses provide effective templates for perovskite nanomaterials. The virus-templated nanocrystals are small in size, highly crystalline, and show photocatalytic and photovoltaic properties.

Abstract 4287: M13-stabilized single-walled carbon nanotubes as nanoprobes for second near-infrared window fluorescent imaging of targeted tumors

Second near-infrared (NIR) window light (950-1,400 nm) is attractive for in vivo fluorescence imaging due to its deep penetration depth in tissues and low tissue autofluorescence. Here we show genetically engineered multifunctional M13 phage can assemble fluorescent single-walled carbon nanotubes (SWNTs) and ligands for targeted fluorescence imaging of tumors. M13-SWNT probe is detectable in deep tissues even at a low dosage of 2 μg/mL and up to 2.5 cm in tissue-like phantoms. Moreover, targeted probes show specific and four-fold improved uptake in prostate specific membrane antigen positive prostate tumors compared to control non-targeted probes. This M13 phage-based second NIR window fluorescence imaging probe has great potential for specific detection and therapy monitoring of hard-to-detect areas.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4287. doi:1538-7445.AM2012-4287

Graphene sheets stabilized on genetically engineered M13 viral templates as conducting frameworks for hybrid energy-storage materials

Utilization of the material-specific peptide-substrate interactions of M13 virus broadens colloidal stability window of graphene. The homogeneous distribution of graphene is maintained in weak acids and increased ionic strengths by complexing with virus. This graphene/virus conducting template is utilized in the synthesis of energy-storage materials to increase the conductivity of the composite electrode. Successful formation of the hybrid biological template is demonstrated by the mineralization of bismuth oxyfluoride as a cathode material for lithium-ion batteries, with increased loading and improved electronic conductivity.

Highly efficient plasmon-enhanced dye-sensitized solar cells through metal@oxide core-shell nanostructure

We have investigated the effects of localized surface plasmons (LSPs) on the performance of dye-sensitized solar cells (DSSCs). The LSPs from Ag nanoparticles (NPs) increase the absorption of the dye molecules, allowing us to decrease the thickness of photoanodes, which improves electron collection and device performance. The plasmon-enhanced DSSCs became feasible through incorporating core-shell Ag@TiO(2) NPs into conventional TiO(2) photoanodes. The thin shell keeps the photoelectrons from recombining on the surface of metal NPs with dye and electrolyte and improves the stability of metal NPs. With 0.6 wt % Ag@TiO(2) NPs, the power conversion efficiency of DSSCs with thin photoanodes (1.5 μm) increases from 3.1% to 4.4%. Moreover, a small amount of Ag@TiO(2) NPs (0.1 wt %) improves efficiency from 7.8% to 9.0% while decreasing photoanode thickness by 25% for improved electron collection. In addition, plasmon-enhanced DSSCs require 62% less material to maintain the same efficiency as conventional DSSCs.

Fast and easy protocol for the purification of recombinant S-layer protein for synthetic biology applications

A goal of synthetic biology is to make biological systems easier to engineer. One of the aims is to design, with nanometer-scale precision, biomaterials with well-defined properties. The surface-layer protein SbpA forms 2D arrays naturally on the cell surface of Lysinibacillus sphaericus, but also as the purified protein in solution upon the addition of divalent cations. The high propensity of SbpA to form crystalline arrays, which can be simply controlled by divalent cations, and the possibility to genetically alter the protein, make SbpA an attractive molecule for synthetic biology. To be a useful tool, however, it is important that a simple protocol can be used to produce recombinant wild-type and modified SbpA in large quantities and in a biologically active form. The present study addresses this requirement by introducing a mild and non-denaturing purification protocol to produce milligram quantities of recombinant, active SbpA.

Virus-templated self-assembled single-walled carbon nanotubes for highly efficient electron collection in photovoltaic devices

The performance of photovoltaic devices could be improved by using rationally designed nanocomposites with high electron mobility to efficiently collect photo-generated electrons. Single-walled carbon nanotubes exhibit very high electron mobility, but the incorporation of such nanotubes into nanocomposites to create efficient photovoltaic devices is challenging. Here, we report the synthesis of single-walled carbon nanotube-TiO(2) nanocrystal core-shell nanocomposites using a genetically engineered M13 virus as a template. By using the nanocomposites as photoanodes in dye-sensitized solar cells, we demonstrate that even small fractions of nanotubes improve the power conversion efficiency by increasing the electron collection efficiency. We also show that both the electronic type and degree of bundling of the nanotubes in the nanotube/TiO(2) complex are critical factors in determining device performance. With our approach, we achieve a power conversion efficiency in the dye-sensitized solar cells of 10.6%.