Molecular Imaging of Lymphoma: Future Directions and Perspectives

More than 250,000 patients die from Hodgkin or non-Hodgkin lymphoma each year. Currently, molecular imaging with ¹⁸F-FDG-PET/CT is the standard of care for lymphoma staging and therapy response assessment. In this review, we will briefly summarize the role of molecular imaging for lymphoma diagnosis, staging, outcome prediction, and prognostication. We discuss future directions in response assessment and surveillance with quantitative PET parameters, the utility of interim assessment, and the differences with response assessment to immunomodulatory therapy. Lastly, we will cover innovations in the field regarding novel tracers and artificial intelligence.

Abstract LB560: Engineering genetically-encoded synthetic biomarkers for breath-based cancer detection

Background: Breath analysis holds great promise for rapid and noninvasive early cancer detection. However, clinical implementation of endogenous volatile organic compound (VOC) signatures in breath is limited by low signal from nascent tumors and high background expression by nonmalignant tissues. By engineering tumors to express synthetic reporters that are not naturally produced in the human body, background signal from healthy tissues can be minimized, thereby maximizing sensitivity and specificity for tumor detection. Humans and plants share a common cholesterol biosynthesis (mevalonate) pathway, but in plants this pathway also generates volatile secondary metabolites (e.g. that attract pollinators). We therefore hypothesized that cancer cells could be coaxed to produce plant VOCs by genetically introducing the appropriate plant enzymes, and that these VOCs would be detectable in the breath as unique biomarkers of cancer.

Aims: 1) To express the citrus VOC, limonene, in a cultured human cancer cell line; 2) To determine the smallest tumor size at which exhaled limonene can be detected in mice implanted with limonene-expressing tumor cells.

Methods: HeLa cervical cancer cells were stably transfected with DNA vectors encoding limonene synthase (LS) alone or in combination with a truncated version of HMG-CoA reductase (HMGR), a key regulatory enzyme of the mevalonate pathway. Truncation of HMGR (tHMGR) by deletion of its regulatory domain renders it insensitive to feedback inhibition, augmenting flux through the mevalonate pathway and increasing limonene precursors. Cell culture headspace was analyzed using solid phase microextraction (SPME) and gas chromatography-mass spectrometry (GC-MS), confirming the presence of limonene. A xenograft murine tumor model was created by subcutaneously implanting HeLa-LS, HeLa-LS-tHMGR, or untransfected control HeLa cells in both flanks of 10-week-old athymic nude mice. For weekly VOC measurements, mice (n = 12) were placed in 1-liter chambers with continuous flow of highly pure air, and VOCs were collected using Tenax sorbent tubes, which were subsequently analyzed by GC-MS.

Results: Limonene production in HeLa-LS-tHMGR cells was double that of HeLa-LS cells (11.0 vs. 5.6 fg/cell/day) with LODs of 107,000 and 360,000 cells, respectively, and was undetectable in untransfected HeLa cells. In xenograft mice, tumor detection improved proportionally with breath sampling time: a 10-fold increase in sampling duration resulted in 9.4-fold greater limonene production (94 ng vs. 10 ng), and dynamic headspace sampling was ~100-fold more sensitive than static sampling. Importantly, limonene was a sensitive volatile reporter, permitting detection of tumors as small as 5 mm, and increased linearly with tumor size (R2 = 0.97), demonstrating strong utility for monitoring tumor progression. Pharmacokinetic modeling of tumor-derived limonene predicts detection of tumors as small as 7 mm in humans, equivalent to the detection limit of PET imaging, yet far more economical. In future work, this strategy will be incorporated into an inhalable nonviral vector formulation with a tumor-activatable promoter (e.g. survivin) for safe, non-invasive in vivo gene delivery and tumor-specific expression of limonene for breath-based early detection of non-small cell lung cancer.

Citation Format: Ophir Vermesh, Aloma D'Souza, Israt Alam, Mirwais Wardak, Theresa McLaughlin, Fadi El Rami, Ataya Sathirachinda, John Bell, Sharon Pitteri, Michelle James, Sharon Hori, Eric Gross, Sanjiv Gambhir. Engineering genetically-encoded synthetic biomarkers for breath-based cancer detection [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr LB560.

A miniaturized optoelectronic biosensor for real-time point-of-care total protein analysis

A miniaturized optoelectronic sensor is demonstrated that measures total protein concentration in serum and urine with sensitivity and accuracy comparable to gold-standard methods. The sensor is comprised of a vertical cavity surface emitting laser (VCSEL), photodetector and other custom optical components and electronics that can be hybrid packaged into a portable, handheld form factor. In conjunction, a custom fluorescence assay has been developed based on the protein-induced fluorescence enhancement (PIFE) phenomenon, enabling real-time sensor response to changes in protein concentration. Methods are described for the following:•

Standard curves: Used to determine the sensitivity, dynamic range, and linearity of the VCSEL biosensor/PIFE assay system in buffer as well as in human blood and urine samples.

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Comparison of VCSEL biosensor performance with a benchtop fluorimetric microplate reader.

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Accuracy of the VCSEL biosensor/PIFE assay system: Evaluated by comparing sensor measurements with gold-standard clinical laboratory measurements of total protein in serum and urine samples from patients with diabetes.

Continuous health monitoring: An opportunity for precision health

Continuous health monitoring and integrated diagnostic devices, worn on the body and used in the home, will help to identify and prevent early manifestations of disease. However, challenges lie ahead in validating new health monitoring technologies and in optimizing data analytics to extract actionable conclusions from continuously obtained health data.

Real-time point-of-care total protein measurement with a miniaturized optoelectronic biosensor and fast fluorescence-based assay

Measurement of total protein in urine is key to monitoring kidney health in diabetes. However, most total protein assays are performed using large, expensive laboratory chemistry analyzers that are not amenable to point-of-care analysis or home monitoring and cannot provide real-time readouts. We developed a miniaturized optoelectronic biosensor using a vertical cavity surface-emitting laser (VCSEL), coupled with a fast protein assay based on protein-induced fluorescence enhancement (PIFE), that can dynamically measure protein concentrations in protein-spiked buffer, serum, and urine in seconds with excellent sensitivity (urine LOD = 0.023 g/L, LOQ = 0.075 g/L) and over a broad range of physiologically relevant concentrations. Comparison with gold standard clinical assays and standard fluorimetry tools showed that the sensor can accurately and reliably quantitate total protein in clinical urine samples from patients with diabetes. Our VCSEL biosensor is amenable to integration with miniaturized electronics, which could afford a portable, low-cost, easy-to-use device for sensitive, accurate, and real-time total protein measurements from small biofluid volumes.

Molecular Imaging of Chimeric Antigen Receptor T Cells by ICOS-ImmunoPET

PURPOSE

Immunomonitoring of chimeric antigen receptor (CAR) T cells relies primarily on their quantification in the peripheral blood, which inadequately quantifies their biodistribution and activation status in the tissues. Noninvasive molecular imaging of CAR T cells by PET is a promising approach with the ability to provide spatial, temporal, and functional information. Reported strategies rely on the incorporation of reporter transgenes or ex vivo biolabeling, significantly limiting the application of CAR T-cell molecular imaging. In this study, we assessed the ability of antibody-based PET (immunoPET) to noninvasively visualize CAR T cells.

EXPERIMENTAL DESIGN

After analyzing human CAR T cells in vitro and ex vivo from patient samples to identify candidate targets for immunoPET, we employed a syngeneic, orthotopic murine tumor model of lymphoma to assess the feasibility of in vivo tracking of CAR T cells by immunoPET using the 89Zr-DFO-anti-ICOS tracer, which we have previously reported.

RESULTS

Analysis of human CD19-CAR T cells during activation identified the Inducible T-cell COStimulator (ICOS) as a potential target for immunoPET. In a preclinical tumor model, 89Zr-DFO-ICOS mAb PET-CT imaging detected significantly higher signal in specific bone marrow-containing skeletal sites of CAR T-cell-treated mice compared with controls. Importantly, administration of ICOS-targeting antibodies at tracer doses did not interfere with CAR T-cell persistence and function.

CONCLUSIONS

This study highlights the potential of ICOS-immunoPET imaging for monitoring of CAR T-cell therapy, a strategy readily applicable to both commercially available and investigational CAR T cells.See related commentary by Volpe et al., p. 911.

Visualization of Activated T Cells by OX40-ImmunoPET as a Strategy for Diagnosis of Acute Graft-versus-Host Disease

Graft-versus-host disease (GvHD) is a major complication of allogeneic hematopoietic cell transplantation (HCT), mediated primarily by donor T cells that become activated and attack host tissues. Noninvasive strategies detecting T-cell activation would allow for early diagnosis and possibly more effective management of HCT recipients. PET imaging is a sensitive and clinically relevant modality ideal for GvHD diagnosis, and there is a strong rationale for the use of PET tracers that can monitor T-cell activation and expansion with high specificity. The TNF receptor superfamily member OX40 (CD134) is a cell surface marker that is highly specific for activated T cells, is upregulated during GvHD, and mediates disease pathogenesis. We recently reported the development of an antibody-based activated T-cell imaging agent targeting OX40. In the present study, we visualize the dynamics of OX40 expression in an MHC-mismatch mouse model of acute GvHD using OX40-immunoPET. This approach enabled visualization of T-cell activation at early stages of disease, prior to overt clinical symptoms with high sensitivity and specificity. This study highlights the potential utility of the OX40 PET imaging as a new strategy for GvHD diagnosis and therapy monitoring. SIGNIFICANCE: OX40-immunoPET imaging is a promising noninvasive strategy for early detection of GvHD, capable of detecting signs of GvHD pathology even prior to the development of overt clinical symptoms.

Low-frequency ultrasound-mediated cytokine transfection enhances T cell recruitment at local and distant tumor sites

Robust cytotoxic T cell infiltration has proven to be difficult to achieve in solid tumors. We set out to develop a flexible protocol to efficiently transfect tumor and stromal cells to produce immune-activating cytokines, and thus enhance T cell infiltration while debulking tumor mass. By combining ultrasound with tumor-targeted microbubbles, membrane pores are created and facilitate a controllable and local transfection. Here, we applied a substantially lower transmission frequency (250 kHz) than applied previously. The resulting microbubble oscillation was significantly enhanced, reaching an effective expansion ratio of 35 for a peak negative pressure of 500 kPa in vitro. Combining low-frequency ultrasound with tumor-targeted microbubbles and a DNA plasmid construct, 20% of tumor cells remained viable, and ∼20% of these remaining cells were transfected with a reporter gene both in vitro and in vivo. The majority of cells transfected in vivo were mucin 1+/CD45- tumor cells. Tumor and stromal cells were then transfected with plasmid DNA encoding IFN-β, producing 150 pg/106 cells in vitro, a 150-fold increase compared to no-ultrasound or no-plasmid controls and a 50-fold increase compared to treatment with targeted microbubbles and ultrasound (without IFN-β). This enhancement in secretion exceeds previously reported fourfold to fivefold increases with other in vitro treatments. Combined with intraperitoneal administration of checkpoint inhibition, a single application of IFN-β plasmid transfection reduced tumor growth in vivo and recruited efficacious immune cells at both the local and distant tumor sites.

Toward achieving precision health

Health care systems primarily focus on patients after they present with disease, not before. The emerging field of precision health encourages disease prevention and earlier detection by monitoring health and disease based on an individual's risk. Active participation in health care can be encouraged with continuous health-monitoring devices, providing a higher-resolution picture of human health and disease. However, the development of monitoring technologies must prioritize the collection of actionable data and long-term user engagement.

Photoacoustic clinical imaging

Photoacoustic is an emerging biomedical imaging modality, which allows imaging optical absorbers in the tissue by acoustic detectors (light in - sound out). Such a technique has an immense potential for clinical translation since it allows high resolution, sufficient imaging depth, with diverse endogenous and exogenous contrast, and is free from ionizing radiation. In recent years, tremendous developments in both the instrumentation and imaging agents have been achieved. These opened avenues for clinical imaging of various sites allowed applications such as brain functional imaging, breast cancer screening, diagnosis of psoriasis and skin lesions, biopsy and surgery guidance, the guidance of tumor therapies at the reproductive and urological systems, as well as imaging tumor metastases at the sentinel lymph nodes. Here we survey the various clinical and pre-clinical literature and discuss the potential applications and hurdles that still need to be overcome.

An intravascular magnetic wire for the high-throughput retrieval of circulating tumour cells in vivo

The detection and analysis of rare blood biomarkers is necessary for early diagnosis of cancer and to facilitate the development of tailored therapies. However, current methods for the isolation of circulating tumour cells (CTCs) or nucleic acids present in a standard clinical sample of only 5-10 ml of blood provide inadequate yields for early cancer detection and comprehensive molecular profiling. Here, we report the development of a flexible magnetic wire that can retrieve rare biomarkers from the subject's blood in vivo at a much higher yield. The wire is inserted and removed through a standard intravenous catheter and captures biomarkers that have been previously labelled with injected magnetic particles. In a proof-of-concept experiment in a live porcine model, we demonstrate the in vivo labelling and single-pass capture of viable model CTCs in less than 10 s. The wire achieves capture efficiencies that correspond to enrichments of 10-80 times the amount of CTCs in a 5-ml blood draw, and 500-5,000 times the enrichments achieved using the commercially available Gilupi CellCollector.

Abstract 3031: Positron emission tomography imaging of activated T cells by targeting OX40 reveals spatiotemporal immune dynamics and predicts response to in situ tumor vaccination

Clinical success of cancer immunotherapies has renewed interest in imaging the behavior of immune cells. Due to the spatiotemporally varying signatures of immune response, it has been difficult to monitor and predict patient outcomes using traditional clinical tests. ImmunoPET, defined herein as positron emission tomography utilizing radiolabeled antibodies, has the potential to enable noninvasive, sensitive and longitudinal interrogation of immune cell subset and state. Cell states including activation, anergy, and exhaustion may be more prognostic of disease outcome than the presence of tumor-infiltrating immune cells alone. In particular, T cell activation is thought to be critical to treatment success across many classes of cancer immunotherapy. In this work, we present the first radionuclide imaging of OX40, a novel and specific biomarker of activated antigen-specific T cells. Activation dependent and T cell restricted expression of OX40 was validated in vitro via flow cytometric analysis. Cell uptake studies with radiolabeled 64Cu-DOTA-AbOX40 demonstrated ~11 fold [p < .0001] higher uptake in dyna-bead activated T cells compared to resting. The tracer showed negligible nonspecific uptake in OX40 blocked or OX40-/- T cells and low background levels across a panel of 5 cancer cell lines tested. In vivo, ImmunoPET imaging revealed new insights into response following in situ tumor vaccination with CpG, an adjuvant immunotherapy currently in clinical trials. Balb-C mice bearing dual A20 lymphoma tumors were administered low dose CPG directly in the left tumor (n=7-10), while vehicle control mice received PBS (n=7-10). Early after vaccination, imaging revealed increased OX40 radiotracer uptake in the CPG treated tumor (TT) [~37%; p<0.05] confirmed by immunofluorescent staining. ViSNE, a visualization technique for high-dimensional cytometry data, classified OX40+ single cells in a cluster associated with a nonregulatory, activated CD4 T cell phenotype. CPG treatment led to local expansion of this unique OX40 cell population [~63%; p<0.05]. By late time points, a full systemic response emerged as evidenced by increased Luminex cytokine measurements in the plasma of CPG-treated mice. Unsupervised hierarchical clustering based on radiotracer or cytokine measurements correctly assigned mice into CPG-treated or vehicle cohorts, with few exceptions. More remarkably, a generalized linear regression model indicated early PET signal (mean %ID/g) in the local tumor environment to be highly predictive of response outcomes at late timepoints [r2=0.746]. OX40 ImmunoPET provides a readily translatable approach for monitoring activated T cells with high sensitivity and specificity. In this instance, integration of molecular imaging and computational immunology enabled systems-level interrogation of vaccine response.

Citation Format: Aaron T. Mayer, Israt S. Alam, Idit Sagiv-Barfi, Kezheng Wang, Ophir Vermesh, Debra K. Czerwinski, Emily M. Johnson, Michelle L. James, Ronald Levy, Sanjiv S. Gambhir. Positron emission tomography imaging of activated T cells by targeting OX40 reveals spatiotemporal immune dynamics and predicts response to in situ tumor vaccination [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3031.

Imaging activated T cells predicts response to cancer vaccines

In situ cancer vaccines are under active clinical investigation, given their reported ability to eradicate both local and disseminated malignancies. Intratumoral vaccine administration is thought to activate a T cell-mediated immune response, which begins in the treated tumor and cascades systemically. In this study, we describe a PET tracer (64Cu-DOTA-AbOX40) that enabled noninvasive and longitudinal imaging of OX40, a cell-surface marker of T cell activation. We report the spatiotemporal dynamics of T cell activation following in situ vaccination with CpG oligodeoxynucleotide in a dual tumor-bearing mouse model. We demonstrate that OX40 imaging was able to predict tumor responses on day 9 after treatment on the basis of tumor tracer uptake on day 2, with greater accuracy than both anatomical and blood-based measurements. These studies provide key insights into global T cell activation following local CpG treatment and indicate that 64Cu-DOTA-AbOX40 is a promising candidate for monitoring clinical cancer immunotherapy strategies.

The Exosome Total Isolation Chip

Circulating tumor-derived extracellular vesicles (EVs) have emerged as a promising source for identifying cancer biomarkers for early cancer detection. However, the clinical utility of EVs has thus far been limited by the fact that most EV isolation methods are tedious, nonstandardized, and require bulky instrumentation such as ultracentrifugation (UC). Here, we report a size-based EV isolation tool called ExoTIC (exosome total isolation chip), which is simple, easy-to-use, modular, and facilitates high-yield and high-purity EV isolation from biofluids. ExoTIC achieves an EV yield ∼4-1000-fold higher than that with UC, and EV-derived protein and microRNA levels are well-correlated between the two methods. Moreover, we demonstrate that ExoTIC is a modular platform that can sort a heterogeneous population of cancer cell line EVs based on size. Further, we utilize ExoTIC to isolate EVs from cancer patient clinical samples, including plasma, urine, and lavage, demonstrating the device's broad applicability to cancers and other diseases. Finally, the ability of ExoTIC to efficiently isolate EVs from small sample volumes opens up avenues for preclinical studies in small animal tumor models and for point-of-care EV-based clinical testing from fingerprick quantities (10-100 μL) of blood.

Abstract 3796: An intravascular magnetic wire for high-throughput in vivo enrichment of rare circulating cancer biomarkers

Background: Liquid biopsies have long promised to enable earlier cancer diagnosis and tailored therapy. However, circulating tumor cells (CTCs) are extremely rare (1-10 cells per mL blood), limiting their clinical utility. There are too few CTCs in a standard 5-10 mL blood sample for culture and drug susceptibility testing, or for comprehensively profiling a molecularly heterogeneous cancer and its metastases for drug resistance mutations. To achieve large-scale CTC enrichment, new strategies are needed that can rapidly and effectively interrogate large blood volumes.

Aim: To design a flexible magnetic wire capable of high-throughput intravascular enrichment and retrieval of rare biomarkers, including CTCs, from the entire circulating blood volume to attain a much higher biomarker yield for earlier cancer detection and personalized treatment.

Methods: We present a promising platform for in vivo enrichment of rare biomarkers, the Magnetic Wire for Intravascular Retrieval and Enrichment (MagWIRE): a flexible, self-contained magnetic wire consisting of a string of small magnets with alternating polarities, achieving high local field gradients along its entire length to capture magnetically labeled targets from a large surrounding volume. The platform is proposed to work as follows: Blood biomarkers are immunomagnetically labeled by injecting a patient with antibody-coated magnetic particles (MPs), similar to FDA-approved Feraheme®. The MagWIRE is then inserted through a standard IV catheter into a superficial vein in the arm or through an existing chemotherapy port to magnetically capture passing MP-bound biomarkers. Within an hour, ~5 liters has circulated through a 2-3-mm-diameter human vein, allowing most of the patient’s blood volume to be sampled. The magnets can then be displaced from the MagWIRE sheath to elute the bound targets into buffer for downstream analysis. We performed proof-of-concept demonstrations in: 1) a closed-loop blood circulation system consisting of a pump, tubing, and a blood reservoir, and 2) in vivo within a porcine ear vein model. To model CTC capture, we targeted H1650 lung cancer cells with 1-μm superparamagnetic iron oxide particles coated with antibodies against epithelial cell adhesion molecule (EpCAM), a commonly used CTC marker. We couple the MagWIRE with a unique approach for rapid (<10 seconds) magnetic labeling of CTCs in flow for immediate downstream capture by the wire on a single pass.

Results: Considerable gains are achievable by sampling from large volumes, even at relatively low capture efficiencies. In our closed-loop setup, the MagWIRE demonstrated capture efficiencies in whole blood of 56.14+/-15.80% for pre-labeled cells and 10.17+/-5.41% for cells labeled in flow. In a porcine ear model, we captured cells with efficiencies up to 8%, corresponding to 80-fold enrichment when integrated over a 5-liter blood volume compared with a 5 mL blood draw.

Citation Format: Ophir Vermesh, Amin Aalipour, Tianjia J. Ge, Yamil Saenz, Yue Guo, Seung-min Park, Yoshiaki Mitsutake, Michael Bachmann, Chin Chun Ooi, Kerstin Mueller, Hamed Arami, Alfredo Green, Shan X. Wang, Sanjiv S. Gambhir. An intravascular magnetic wire for high-throughput in vivo enrichment of rare circulating cancer biomarkers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3796. doi:10.1158/1538-7445.AM2017-3796

Towards clinically translatable in vivo nanodiagnostics

Nanodiagnostics as a field makes use of fundamental advances in nanobiotechnology to diagnose, characterize and manage disease at the molecular scale. As these strategies move closer to routine clinical use, a proper understanding of different imaging modalities, relevant biological systems and physical properties governing nanoscale interactions is necessary to rationally engineer next-generation bionanomaterials. In this Review, we analyse the background physics of several clinically relevant imaging modalities and their associated sensitivity and specificity, provide an overview of the materials currently used for in vivo nanodiagnostics, and assess the progress made towards clinical translation. This work provides a framework for understanding both the impressive progress made thus far in the nanodiagnostics field as well as presenting challenges that must be overcome to obtain widespread clinical adoption.

Targeted superparamagnetic iron oxide nanoparticles for early detection of cancer: Possibilities and challenges

Nanomedicine, the integration of nanotechnological tools in medicine demonstrated promising potential to revolutionize the diagnosis and treatment of various human health conditions. Nanoparticles (NPs) have shown much promise in diagnostics of cancer, especially since they can accommodate targeting molecules on their surface, which search for specific tumor cell receptors upon injection into the blood stream. This concentrates the NPs in the desired tumor location. Furthermore, such receptor-specific targeting may be exploited for detection of potential metastases in an early stage. Some NPs, such as superparamagnetic iron oxide NPs (SPIONs), are also compatible with magnetic resonance imaging (MRI), which makes their clinical translation and application rather easy and accessible for tumor imaging purposes. Furthermore, multifunctional and/or theranostic NPs can be used for simultaneous imaging of cancer and drug delivery. In this review article, we will specifically focus on the application of SPIONs in early detection and imaging of major cancer types.

FROM THE CLINICAL EDITOR

Super-paramagnetic iron oxide nanoparticles (SPIONs) have been reported by many to be useful as an MRI contrast agent in the detection of tumors. To further enhance the tumor imaging, SPIONs can be coupled with tumor targeting motifs. In this article, the authors performed a comprehensive review on the current status of using targeted SPIONS in tumor detection and also the potential hurdles to overcome.

Sol-gel synthesis and electrospraying of biodegradable (P2O5)55-(CaO)30-(Na2O)15 glass nanospheres as a transient contrast agent for ultrasound stem cell imaging

Ultrasound imaging is a powerful tool in medicine because of the millisecond temporal resolution and submillimeter spatial resolution of acoustic imaging. However, the current generation of acoustic contrast agents is primarily limited to vascular targets due to their large size. Nanosize particles have the potential to be used as a contrast agent for ultrasound molecular imaging. Silica-based nanoparticles have shown promise here; however, their slow degradation rate may limit their applications as a contrast agent. Phosphate-based glasses are an attractive alternative with controllable degradation rate and easily metabolized degradation components in the body. In this study, biodegradable P2O5-CaO-Na2O phosphate-based glass nanospheres (PGNs) were synthesized and characterized as contrast agents for ultrasound imaging. The structure of the PGNs was characterized using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), (31)P magic angle spinning nuclear magnetic resonance ((31)P MAS NMR), and Fourier transform infrared (FTIR) spectroscopy. The SEM images indicated a spherical shape with a diameter size range of 200-500 nm. The XRD, (31)P NMR, and FTIR results revealed the amorphous and glassy nature of PGNs that consisted of mainly Q(1) and Q(2) phosphate units. We used this contrast to label mesenchymal stem cells and determined in vitro and in vivo detection limits of 5 and 9 μg/mL, respectively. Cell counts down to 4000 could be measured with ultrasound imaging with no cytoxicity at doses needed for imaging. Importantly, ion-release studies confirmed these PGNs biodegrade into aqueous media with degradation products that can be easily metabolized in the body.

A self-powered, one-step chip for rapid, quantitative and multiplexed detection of proteins from pinpricks of whole blood

We describe an automated, self-powered chip based on lateral flow immunoassay for rapid, quantitative, and multiplex protein detection from pinpricks of whole blood. The device incorporates on-chip purification of blood plasma by employing inertial forces to focus blood cells away from the assay surface, where plasma proteins are captured and detected on antibody "barcode" arrays. Power is supplied from the capillary action of a piece of adsorbent paper, and sequentially drives, over a 40 minute period, the four steps required to capture serum proteins and then develop a multiplex immunoassay. An 11 protein panel is assayed from whole blood, with high sensitivity and high reproducibility. This inexpensive, self-contained, and easy to operate chip provides a useful platform for point-of-care diagnoses, particularly in resource-limited settings.

Self-powered microfluidic chips for multiplexed protein assays from whole blood

We report herein on a self-powered, self-contained microfluidic-based chip designed to separate plasma from whole blood, and then execute an assay of a multiplexed panel of plasma biomarker proteins. The power source is based upon a chemical reaction that is catalytically triggered by the push of a button on the chip. We demonstrate assays of a dozen blood-based protein biomarkers using this automated, self-contained device. This platform can potentially permit high throughput, accurate, multiplexed blood diagnostic measurements in remote locations and by minimally trained individuals.

Fast nonlinear ion transport via field-induced hydrodynamic slip in sub-20-nm hydrophilic nanofluidic transistors

Electrolyte transport through an array of 20 nm wide, 20 microm long SiO(2) nanofluidic transistors is described. At sufficiently low ionic strength, the Debye screening length exceeds the channel width, and ion transport is limited by the negatively charged channel surfaces. At source-drain biases >5 V, the current exhibits a sharp, nonlinear increase, with a 20-50-fold conductance enhancement. This behavior is attributed to a breakdown of the zero-slip condition. Implications for energy conversion devices are discussed.

Integrated barcode chips for rapid, multiplexed analysis of proteins in microliter quantities of blood

As the tissue that contains the largest representation of the human proteome, blood is the most important fluid for clinical diagnostics. However, although changes of plasma protein profiles reflect physiological or pathological conditions associated with many human diseases, only a handful of plasma proteins are routinely used in clinical tests. Reasons for this include the intrinsic complexity of the plasma proteome, the heterogeneity of human diseases and the rapid degradation of proteins in sampled blood. We report an integrated microfluidic system, the integrated blood barcode chip that can sensitively sample a large panel of protein biomarkers over broad concentration ranges and within 10 min of sample collection. It enables on-chip blood separation and rapid measurement of a panel of plasma proteins from quantities of whole blood as small as those obtained by a finger prick. Our device holds potential for inexpensive, noninvasive and informative clinical diagnoses, particularly in point-of-care settings.

Integrated barcode chips for rapid, multiplexed analysis of proteins in microliter quantities of blood

As the tissue that contains the largest representation of the human proteome, blood is the most important fluid for clinical diagnostics. However, although changes of plasma protein profiles reflect physiological or pathological conditions associated with many human diseases, only a handful of plasma proteins are routinely used in clinical tests. Reasons for this include the intrinsic complexity of the plasma proteome, the heterogeneity of human diseases and the rapid degradation of proteins in sampled blood. We report an integrated microfluidic system, the integrated blood barcode chip that can sensitively sample a large panel of protein biomarkers over broad concentration ranges and within 10 min of sample collection. It enables on-chip blood separation and rapid measurement of a panel of plasma proteins from quantities of whole blood as small as those obtained by a finger prick. Our device holds potential for inexpensive, noninvasive and informative clinical diagnoses, particularly in point-of-care settings.

Toward Large Arrays of Multiplex Functionalized Carbon Nanotube Sensors for Highly Sensitive and Selective Molecular Detection

Arrays of electrical devices with each comprising multiple single-walled carbon nanotubes (SWNT) bridging metal electrodes are obtained by chemical vapor deposition (CVD) of nanotubes across prefabricated electrode arrays. The ensemble of nanotubes in such a device collectively exhibits large electrical conductance changes under electrostatic gating, owing to the high percentage of semiconducting nanotubes. This leads to the fabrication of large arrays of low-noise electrical nanotube sensors with 100% yield for detecting gas molecules. Polymer functionalization is used to impart high sensitivity and selectivity to the sensors. Polyethyleneimine coating affords n-type nanotube devices capable of detecting NO₂ at less than 1 ppb (parts-per-billion) concentrations while being insensitive to NH₃. Coating Nafion (a polymeric perfluorinated sulfonic acid ionomer) on nanotubes blocks NO₂ and allows for selective sensing of NH₃. Multiplex functionalization of a nanotube sensor array is carried out by microspotting. Detection of molecules in a gas mixture is demonstrated with the multiplexed nanotube sensors.