Early Detection of Myeloid-Derived Suppressor Cells in the Lung Pre-Metastatic Niche by Shortwave Infrared Nanoprobes.

Metastatic breast cancer remains a significant source of mortality amongst breast cancer patients and is generally considered incurable in part due to the difficulty in detection of early micro-metastases. The pre-metastatic niche (PMN) is a tissue microenvironment that has undergone changes to support the colonization and growth of circulating tumor cells, a key component of which is the myeloid-derived suppressor cell (MDSC). Therefore, the MDSC has been identified as a potential biomarker for PMN formation, the detection of which would enable clinicians to proactively treat metastases. However, there is currently no technology capable of the in situ detection of MDSCs available in the clinic. Here, we propose the use of shortwave infrared-emitting nanoprobes for the tracking of MDSCs and identification of the PMN. Our rare-earth albumin nanocomposites (ReANCs) are engineered to bind the Gr-1 surface marker of murine MDSCs. When delivered intravenously in murine models of breast cancer with high rates of metastasis, the targeted ReANCs demonstrated an increase in localization to the lungs in comparison to control ReANCs. However, no difference was seen in the model with slower rates of metastasis. This highlights the potential utility of MDSC-targeted nanoprobes to assess PMN development and prognosticate disease progression.

Special Section Guest Editorial: Short Wave Infrared Techniques and Applications in Biomedical Optics.

The editorial introduces the JBO Special Section on Short Wave Infrared Techniques and Applications in Biomedical Optics.

Computational imaging with spectral coding increases the spatial resolution of fiber optic bundles.

Fiber optic bundles are used in narrow-diameter medical and industrial instruments for acquiring images from confined locations. Images transmitted through these bundles contain only one pixel of information per fiber core and fail to capture information from the cladding region between cores. Both factors limit the spatial resolution attainable with fiber bundles. We show here that computational imaging (CI) can be combined with spectral coding to overcome these two fundamental limitations and improve spatial resolution in fiber bundle imaging. By acquiring multiple images of a scene with a high-resolution mask pattern imposed, up to 17 pixels of information can be recovered from each fiber core. A dispersive element at the distal end of the bundle imparts a wavelength-dependent lateral shift on light from the object. This enables light that would otherwise be lost at the inter-fiber cladding to be transmitted through adjacent fiber cores. We experimentally demonstrate this approach using synthetic and real objects. Using CI with spectral coding, object features 5× smaller than individual fiber cores were resolved, whereas conventional imaging could only resolve features at least 1.5× larger than each core. In summary, CI combined with spectral coding provides an approach for overcoming the two fundamental limitations of fiber optic bundle imaging.

Shortwave infrared spatial frequency domain imaging for non-invasive measurement of tissue and blood optical properties.

SIGNIFICANCE: The shortwave infrared (SWIR) optical window (∼900 to 2000 nm) has attracted interest for deep tissue imaging due to the lower scattering of light. SWIR spatial frequency domain imaging (SWIR SFDI) provides wide-field tissue optical property measurements in this wavelength band. Key design and performance characteristics, such as portability, wavelength selection, measurement resolution, and the effect of skin have not yet been addressed for SWIR SFDI. AIM: To fabricate and characterize a SWIR SFDI system for clinical use. APPROACH: The optimal choice of wavelengths was identified based on optical property uncertainty estimates and imaging depth. A compact light-emitting diode-based dual wavelength SWIR SFDI system was fabricated. A two-layer inverse model was developed to account for the layered structure of skin. Performance was validated using tissue-simulating phantoms and in-vivo measurements from three healthy subjects. RESULTS: The SWIR SFDI system had a µs' resolution of at least 0.03 mm - 1 at 880 nm and 0.02 mm - 1 at 1100 nm. The two-layer inverse model reduced the error in deeper layer µs' extractions by at least 24% in the phantom study. The two-layer model also increased the contrast between superficial vessels and the surrounding tissue for in-vivo measurements. CONCLUSION: The clinic-ready SWIR SFDI device is sensitive to small optical property alterations in diffuse media, provides enhanced accuracy in quantifying optical properties in the deeper layers in phantoms, and provided enhanced contrast of subcutaneous blood vessels.

Delivering the Diagnosis: A Practical Approach to a Patient With a Functional Neurological Disorder.

Functional Neurological Disorders are a common and debilitating group of diseases that have been the subject of stigma and confusion across medical history. It is well-documented that prognosis and even possible resolution of symptoms are linked to successful delivery of the diagnosis by the clinician, and correct understanding of diagnosis by the patient. In the following article, we delineate the nature of these disorders and provide an overview to assist providers successfully navigate the communication of these diagnoses to patients and families.

Short-Wave Infrared Emitting Nanocomposites for Fluorescence-Guided Surgery.

Fluorescence-guided surgery (FGS) is an emerging technique for tissue visualization during surgical procedures. Structures of interest are labeled with exogenous probes whose fluorescent emissions are acquired and viewed in real-time with optical imaging systems. This study investigated rare-earth-doped albumin-encapsulated nanocomposites (REANCs) as short-wave infrared emitting contrast agents for FGS. Experiments were conducted using an animal model of 4T1 breast cancer. The signal-to-background ratio (SBR) obtained with REANCs was compared to values obtained using indocyanine green (ICG), a near-infrared dye used in clinical practice. Prior to resection, the SBR for tumors following intratumoral administration of REANCs was significantly higher than for tumors injected with ICG. Following FGS, evaluation of fluorescence intensity levels in excised tumors and at the surgical bed demonstrated higher contrast between tissues at these sites with REANC contrast than ICG. REANCs also demonstrated excellent photostability over 2 hours of continuous illumination, as well as the ability to perform FGS under ambient lighting, establishing these nanocomposites as a promising contrast agent for FGS applications.

Shortwave infrared emitting multicolored nanoprobes for biomarker-specific cancer imaging in vivo.

BACKGROUND: The ability to detect tumor-specific biomarkers in real-time using optical imaging plays a critical role in preclinical studies aimed at evaluating drug safety and treatment response. In this study, we engineered an imaging platform capable of targeting different tumor biomarkers using a multi-colored library of nanoprobes. These probes contain rare-earth elements that emit light in the short-wave infrared (SWIR) wavelength region (900-1700 nm), which exhibits reduced absorption and scattering compared to visible and NIR, and are rendered biocompatible by encapsulation in human serum albumin. The spectrally distinct emissions of the holmium (Ho), erbium (Er), and thulium (Tm) cations that constitute the cores of these nanoprobes make them attractive candidates for optical molecular imaging of multiple disease biomarkers. METHODS: SWIR-emitting rare-earth-doped albumin nanocomposites (ReANCs) were synthesized using controlled coacervation, with visible light-emitting fluorophores additionally incorporated during the crosslinking phase for validation purposes. Specifically, HoANCs, ErANCs, and TmANCs were co-labeled with rhodamine-B, FITC, and Alexa Fluor 647 dyes respectively. These Rh-HoANCs, FITC-ErANCs, and 647-TmANCs were further conjugated with the targeting ligands daidzein, AMD3100, and folic acid respectively. Binding specificities of each nanoprobe to distinct cellular subsets were established by in vitro uptake studies. Quantitative whole-body SWIR imaging of subcutaneous tumor bearing mice was used to validate the in vivo targeting ability of these nanoprobes. RESULTS: Each of the three ligand-functionalized nanoprobes showed significantly higher uptake in the targeted cell line compared to untargeted probes. Increased accumulation of tumor-specific nanoprobes was also measured relative to untargeted probes in subcutaneous tumor models of breast (4175 and MCF-7) and ovarian cancer (SKOV3). Preferential accumulation of tumor-specific nanoprobes was also observed in tumors overexpressing targeted biomarkers in mice bearing molecularly-distinct bilateral subcutaneous tumors, as evidenced by significantly higher signal intensities on SWIR imaging. CONCLUSIONS: The results from this study show that tumors can be detected in vivo using a set of targeted multispectral SWIR-emitting nanoprobes. Significantly, these nanoprobes enabled imaging of biomarkers in mice bearing bilateral tumors with distinct molecular phenotypes. The findings from this study provide a foundation for optical molecular imaging of heterogeneous tumors and for studying the response of these complex lesions to targeted therapy.

Shortwave Infrared-Emitting Theranostics for Breast Cancer Therapy Response Monitoring.

Therapeutic drug monitoring (TDM) in cancer, while imperative, has been challenging due to inter-patient variability in drug pharmacokinetics. Additionally, most pharmacokinetic monitoring is done by assessments of the drugs in plasma, which is not an accurate gauge for drug concentrations in target tumor tissue. There exists a critical need for therapy monitoring tools that can provide real-time feedback on drug efficacy at target site to enable alteration in treatment regimens early during cancer therapy. Here, we report on theranostic optical imaging probes based on shortwave infrared (SWIR)-emitting rare earth-doped nanoparticles encapsulated with human serum albumin (abbreviated as ReANCs) that have demonstrated superior surveillance capability for detecting micro-lesions at depths of 1 cm in a mouse model of breast cancer metastasis. Most notably, ReANCs previously deployed for detection of multi-organ metastases resolved bone lesions earlier than contrast-enhanced magnetic resonance imaging (MRI). We engineered tumor-targeted ReANCs carrying a therapeutic payload as a potential theranostic for evaluating drug efficacy at the tumor site. In vitro results demonstrated efficacy of ReANCs carrying doxorubicin (Dox), providing sustained release of Dox while maintaining cytotoxic effects comparable to free Dox. Significantly, in a murine model of breast cancer lung metastasis, we demonstrated the ability for therapy monitoring based on measurements of SWIR fluorescence from tumor-targeted ReANCs. These findings correlated with a reduction in lung metastatic burden as quantified via MRI-based volumetric analysis over the course of four weeks. Future studies will address the potential of this novel class of theranostics as a preclinical pharmacological screening tool.

Shortwave-infrared meso-patterned imaging enables label-free mapping of tissue water and lipid content.

Water and lipids are key participants in many biological processes, but there are few non-invasive methods that provide quantification of these components in vivo, and none that can isolate and quantify lipids in the blood. Here we develop a new imaging modality termed shortwave infrared meso-patterned imaging (SWIR-MPI) to provide label-free, non-contact, spatial mapping of water and lipid concentrations in tissue. The method utilizes patterned hyperspectral illumination to target chromophore absorption bands in the 900-1,300 nm wavelength range. We use SWIR-MPI to monitor clinically important physiological processes including edema, inflammation, and tumor lipid heterogeneity in preclinical models. We also show that SWIR-MPI can spatially map blood-lipids in humans, representing an example of non-invasive and contact-free measurements of in vivo blood lipids. Together, these results highlight the potential of SWIR-MPI to enable new capabilities in fundamental studies and clinical monitoring of major conditions including obesity, cancer, and cardiovascular disease.

An Experimental Review of Optical Coherence Tomography Systems for Noninvasive Assessment of Hard Dental Tissues.

Optical coherence tomography (OCT) is a noninvasive, high-resolution, cross-sectional imaging technique. To date, OCT has been demonstrated in several areas of dentistry, primarily using wavelengths around 1,300 nm, low numerical aperture (NA) imaging lenses, and detectors insensitive to the polarization of light. The objective of this study is to compare the performance of three commercially available OCT systems operating with alternative wavelengths, imaging lenses, and detectors for OCT imaging of dental enamel. Spectral-domain (SD) OCT systems with (i) 840 nm (Lumedica, OQ LabScope 1.0), (ii) 1,300 nm (Thorlabs, Tel320) center wavelengths, and (iii) a swept-source (SS) OCT system (Thorlabs OCS1300SS) centered at 1,325 nm with optional polarization-sensitive detection were used. Low NA (0.04) and high NA (0.15) imaging lenses were used with system (iii). Healthy in vivo and in vitrohuman enamel and eroded in vitro bovine enamel specimens were imaged. The Tel320 system achieved greater imaging depth than the OQ LabScope 1.0, on average imaging 2.6 times deeper into the tooth (n = 10). The low NA lens provided a larger field of view and depth of focus, while the high NA lens provided higher lateral resolution and greater contrast. Polarization-sensitive imaging eliminated birefringent banding artifacts that can appear in conventional OCT scans. In summary, this study illustrates the performance of three commercially available OCT systems, objective lenses, and imaging modes and how these can affect imaging depth, resolution, field of view, and contrast in enamel. Users investigating OCT for dental applications should consider these factors when selecting an OCT system for clinical or basic science studies.

FRET efficiency measurement in a molecular tension probe with a low-cost frequency-domain fluorescence lifetime imaging microscope.

We demonstrate the possibility of measuring FRET efficiency with a low-cost frequency-domain fluorescence lifetime imaging microscope (FD-FLIM). The system utilizes single-frequency-modulated excitation, which enables the use of cost-effective laser sources and electronics, simplification of data acquisition and analysis, and a dual-channel detection capability. Following calibration with coumarin 6, we measured the apparent donor lifetime in mTFP1-mVenus FRET standards expressed in living cells. We evaluated the system's sensitivity by differentiating the short and long lifetimes of mTFP1 corresponding to the known standards' high and low FRET efficiency, respectively. Furthermore, we show that the lifetime of the vinculin tension sensor, VinTS, at focal adhesions (2.30 ± 0.16 ns) is significantly (p < 10 - 6) longer than the lifetime of the unloaded TSMod probe (2.02 ± 0.16 ns). The pixel dwell time was 6.8 µs for samples expressing the FRET standards, with signal typically an order of magnitude higher than VinTS. The apparent FRET efficiency (EFRETapp) of the standards, calculated from the measured apparent lifetime, was linearly related to their known FRET efficiency by a factor of 0.92 to 0.99 (R2 = 0.98). This relationship serves as a calibration curve to convert apparent FRET to true FRET and circumvent the need to measure multiexponential lifetime decays. This approach yielded a FRET efficiency of 18% to 19.5%, for VinTS, in agreement with published values. Taken together, our results demonstrate a cost-effective, fast, and sensitive FD-FLIM approach with the potential to facilitate applications of FLIM in mechanobiology and FRET-based biosensing.

Computational endoscopy-a framework for improving spatial resolution in fiber bundle imaging.

This Letter presents a framework for computational imaging (CI) in fiber-bundle-based endoscopy systems. Multiple observations are acquired of objects spatially modulated with different random binary masks. Sparse-recovery algorithms then reconstruct images with more resolved pixels than individual fibers in the bundle. Object details lying within the diameter of single fibers are resolved, allowing images with 41,663 resolvable points to be generated through a bundle with 2,420 fibers. Computational fiber bundle imaging of micro- and macro-scale objects is demonstrated using fluorescent standards and biological tissues, including in vivo imaging of a human fingertip. In each case, CI recovers details that conventional endoscopy does not provide.

Surface-Modified Shortwave-Infrared-Emitting Nanophotonic Reporters for Gene-Therapy Applications.

Gene therapy is emerging as the next generation of therapeutic modality with United States Food and Drug Administration approved gene-engineered therapy for cancer and a rare eye-related disorder, but the challenge of real-time monitoring of on-target therapy response remains. In this study, we have designed a theranostic nanoparticle composed of shortwave-infrared-emitting rare-earth-doped nanoparticles (RENPs) capable of delivering genetic cargo and of real-time response monitoring. We showed that the cationic coating of RENPs with branched polyethylenimine (PEI) does not have a significant impact on cellular toxicity, which can be further reduced by selectively modifying the surface characteristics of the PEI coating using counter-ions and expanding their potential applications in photothermal therapy. We showed the tolerability and clearance of a bolus dose of RENPs@PEI in mice up to 7 days after particle injection in addition to the RENPs@PEI ability to distinctively discern lung tumor lesions in a breast cancer mouse model with an excellent signal-to-noise ratio. We also showed the availability of amine functional groups in the collapsed PEI chain conformation on RENPs, which facilitates the loading of genetic cargo that hybridizes with target gene in an in vitro cancer model. The real-time monitoring and delivery of gene therapy at on-target sites will enable the success of an increased number of gene- and cell-therapy products in clinical trials.

Multiscale optical imaging of rare-earth-doped nanocomposites in a small animal model.

Rare-earth-doped nanocomposites have appealing optical properties for use as biomedical contrast agents, but few systems exist for imaging these materials. We describe the design and characterization of (i) a preclinical system for whole animal in vivo imaging and (ii) an integrated optical coherence tomography/confocal microscopy system for high-resolution imaging of ex vivo tissues. We demonstrate these systems by administering erbium-doped nanocomposites to a murine model of metastatic breast cancer. Short-wave infrared emissions were detected in vivo and in whole organ imaging ex vivo. Visible upconversion emissions and tissue autofluorescence were imaged in biopsy specimens, alongside optical coherence tomography imaging of tissue microstructure. We anticipate that this work will provide guidance for researchers seeking to image these nanomaterials across a wide range of biological models.

Assessment of cuspal deflection and volumetric shrinkage of different bulk fill composites using non-contact phase microscopy and micro-computed tomography.

The understanding of cuspal deflection and volumetric shrinkage of resin composites is necessary to assess and improve the placement techniques of resin-based materials. The aim of this study was to investigate the cuspal deflection and its relationship with volumetric polymerization shrinkage of different bulk-fill resin composites. The investigation was conducted using non-contact phase microscopy and micro-computed tomography. Thirty custom-milled aluminum blocks were fabricated for microscopy analysis and thirty-six tooth models with standardized Class I cavities were used for micro-computed tomography analysis. Results showed that high-viscosity composites present higher cuspal deflection compared to bulk-fill composites. The filler loading of resin composites seems to have an effect on cusp deflection, since the higher the filler content percentage, the higher the cusp deflection. On the other hand, it seems to have an opposite effect on volumetric shrinkage, since higher filler loadings produced lower volumetric shrinkage percentages.

Optical Projection Tomography with a Tissue Clearing Agent for Developmental and Reproductive Toxicology Studies.

BACKGROUND: Developmental and reproductive toxicology (DART) testing represents an expensive and time-consuming stage in determining the toxicological profile of new chemical entities. Within DART studies, morphological evaluation of fetal skeletons for developmental abnormalities typically requires 7 to 14 days. Current processing techniques involve digestion of soft tissue using a strong base (KOH), followed by qualitative assessment of the remaining skeletal tissue by a fetal morphologist. Micro-computed tomography (micro-CT) has been proposed as a nondestructive image-based alternative for quantitative assessment of skeletal morphology. Such methods eliminate the need for extensive tissue processing and can be paired with quantitative analysis algorithms. However, due to the significant capital and operational expenses required for micro-CT imaging, this approach has yet to gain widespread traction and regulatory acceptance. METHODS: A novel tissue clearing agent was used in 1-week-old rats to render soft tissue optically transparent. Alizarin red was used to stain the skeleton. High dynamic range optical trans-illumination images were then acquired with an optical-CT imaging system and rendered as three-dimensional images of skeletal structure. RESULTS: High dynamic range-based optical-CT imaging of chemically cleared tissues can rapidly generate high resolution (50-250 µm) reconstructions of whole skeletons. CONCLUSION: In summary, this study demonstrates that the combination of tissue clearing, optical imaging, and novel reconstruction algorithms may present a new paradigm for high-throughput evaluation of tissues in DART testing. Birth Defects Research 110:12-16, 2018. © 2017 Wiley Periodicals, Inc.

Vibrational analysis of implants and tissues: Calibration and mechanical spectroscopy of multi-component materials.

Several new methods have been used to non-destructively evaluate the mechanical properties of materials and tissues including magnetic resonance elastography, ultrasound elastography, optical coherence elastography, and various forms of vibrational analysis. One of the limitations of using these methods is the need to establish a relationship between the modulus measured using each new technique and moduli measured using well-established techniques such as constant rate-of-strain and incremental stress-strain curves. In addition, there are no available methods for analyzing the mechanical properties of the individual components of multi-component materials. In this article, we present data showing that there is a strong correlation (correlation coefficient >0.9) between the modulus measured using classical uniaxial tensile incremental stress-strain tests and those made using a combination of optical coherence tomography and vibrational analysis. Beyond this, we demonstrate that the moduli of the major structural components of pig skin can be measured using this technique. These results suggest that optical coherence tomography in concert with vibrational analysis can be used to measure the moduli of biological and implant materials without having to determine Poisson's ratio. In addition, each of the moduli of the major fibrous components of pig skin can be measured concurrently using this technique. These results may be useful in the characterization of synthetic implants and tissue derived materials without requiring removal of one or more components that are to be characterized. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1666-1671, 2017.

A method for nondestructive mechanical testing of tissues and implants.

Numerous tests have been used to elucidate mechanical properties of tissues and implants including tensile, compressive, shear, hydrostatic compression, and three-point bending in one or more axial directions. The development of a nondestructive test that could be applied to tissues and materials in vivo would promote the analysis of tissue pathology as well as the design of implant materials. The purpose of this article is to present the results of preliminary studies demonstrating nondestructive in vitro testing of a tissue model, decellularized human dermis, and a model implant, silicone rubber, using a combination of optical coherence tomography (OCT), and vibrational analysis. The results presented suggest that nondestructive vibrational testing of tissues and materials can be used to determine the modulus of polymeric materials and the results are similar to those found using tensile stress-strain measurements. The advantage of this method is that the modulus can be obtained from vibrational methods without having to approximate the tangent to the stress-strain curve, which is difficult for nonlinear materials that have a rapidly changing slope. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 15-22, 2017.